Update to version 2.2. Only the PacketAlias*()
functions should now be used. The old 2.1 stuff is there for backwards compatability. Submitted by: Charles Mott <cmott@snake.srv.net>
This commit is contained in:
Brian Somers
parent
9fb4ef6227
commit
3efa11bb71
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=27864
105
lib/libalias/HISTORY
Normal file
105
lib/libalias/HISTORY
Normal file
@ -0,0 +1,105 @@
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Version 1.0: August 11, 1996 (cjm)
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Version 1.1: August 20, 1996 (cjm)
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- Host accepts incoming connections for ports 0 to 1023.
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Version 1.2: September 7, 1996 (cjm)
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- Fragment handling error in alias_db.c corrected.
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Version 1.3: September 15, 1996 (cjm)
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- Generalized mechanism for handling incoming
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connections (no more 0 to 1023 restriction).
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- Increased ICMP support (will handle traceroute now).
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- Improved TCP close connection logic.
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Version 1.4: September 16, 1996 (cjm)
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Version 1.5: September 17, 1996 (cjm)
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- Corrected error in handling incoming UDP packets
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with zero checksum.
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Version 1.6: September 18, 1996
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- Simplified ICMP data storage. Will now handle
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tracert from Win95 and NT as well as FreeBSD
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traceroute, which uses UDP packets to non-existent
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ports.
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Verstion 1.7: January 9, 1997 (cjm)
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- Reduced malloc() activity for ICMP echo and
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timestamp requests.
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- Added handling for out-of-order IP fragments.
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- Switched to differential checksum computation
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for IP headers (TCP, UDP and ICMP checksums
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were already differential).
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- Accepts FTP data connections from other than
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port 20. This allows one ftp connections
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from two hosts which are both running packet
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aliasing.
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Version 1.8: January 14, 1997 (cjm)
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- Fixed data type error in function StartPoint()
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in alias_db.c (this bug did not exist before v1.7)
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Version 1.9: February 1, 1997 (Eivind Eklund <perhaps@yes.no>)
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- Added support for IRC DCC (ee)
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- Changed the aliasing routines to use ANSI style
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throughout (ee)
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- Minor API changes for integration with other
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programs than PPP (ee)
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- Fixed minor security hole in alias_ftp.c for
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other applications of the aliasing software.
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Hole could _not_ manifest in ppp+pktAlias, but
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could potentially manifest in other applications
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of the aliasing. (ee)
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- Connections initiated from packet aliasing
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host machine will not have their port number
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aliased unless it conflicts with an aliasing
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port already being used. (There is an option
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to disable this for debugging) (cjm)
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- Sockets will be allocated in cases where
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there might be port interference with the
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host machine. This can be disabled in cases
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where the ppp host will be acting purely as a
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masquerading router and not generate any
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traffic of its own.
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(cjm)
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Version 2.0: March, 1997 (cjm)
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- Aliasing links are cleared only when a host interface address
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changes.
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- PacketAliasPermanentLink() API added.
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- Option for only aliasing private, unregistered
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IP addresses added.
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- Substantial rework to the aliasing lookup engine.
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Version 2.1: May, 1997 (cjm)
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- Continuing rework to the aliasing lookup engine
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to support multiple incoming addresses and static
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NAT. PacketAliasRedirectPort() and
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PacketAliasRedirectAddr() added to API.
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- Now supports outgoing as well as incoming ICMP
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error messges.
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Version 2.2: July, 1997 (cjm)
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- Rationalized API function names to all begin with
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"PacketAlias..." Old function names are retained
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for backwards compatitibility.
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- Packet aliasing engine will now free memory of
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fragments which are never resolved after a timeout
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period. Once a fragment is resolved, it becomes
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the users responsibility to free the memory.
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@ -1,8 +1,9 @@
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LIB= alias
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SHLIB_MAJOR= 2
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SHLIB_MINOR= 1
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SHLIB_MINOR= 2
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CFLAGS+=-Wall -I${.CURDIR}
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SRCS= alias.c alias_db.c alias_ftp.c alias_irc.c alias_util.c
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SRCS= alias.c alias_db.c alias_ftp.c alias_irc.c alias_util.c alias_old.c
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MAN3=libalias.3
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beforeinstall:
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${INSTALL} -C -o ${BINOWN} -g ${BINGRP} -m 444 ${.CURDIR}/alias.h \
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@ -66,6 +66,13 @@
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and PacketAliasOut2() for dynamic address
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control (e.g. round-robin allocation of
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incoming packets).
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Version 2.2 July 1997 (cjm)
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- Rationalized API function names to begin
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with "PacketAlias..."
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- Eliminated PacketAliasIn2() and
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PacketAliasOut2() as poorly conceived.
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*/
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#include <stdio.h>
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@ -884,20 +891,18 @@ FragmentOut(struct ip *pip)
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/* Outside World Access
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SaveFragmentPtr()
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GetNextFragmentPtr()
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FragmentAliasIn()
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PacketAliasSaveFragment()
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PacketAliasGetFragment()
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PacketAliasFragmentIn()
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PacketAliasIn()
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PacketAliasOut()
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PacketAliasIn2()
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PacketAliasOut2()
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(prototypes in alias.h)
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*/
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int
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SaveFragmentPtr(char *ptr)
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PacketAliasSaveFragment(char *ptr)
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{
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int iresult;
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struct alias_link *link;
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@ -916,7 +921,7 @@ SaveFragmentPtr(char *ptr)
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char *
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GetNextFragmentPtr(char *ptr)
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PacketAliasGetFragment(char *ptr)
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{
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struct alias_link *link;
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char *fptr;
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@ -927,6 +932,7 @@ GetNextFragmentPtr(char *ptr)
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if (link != NULL)
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{
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GetFragmentPtr(link, &fptr);
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SetFragmentPtr(link, NULL);
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SetExpire(link, 0); /* Deletes link */
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return(fptr);
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@ -939,11 +945,11 @@ GetNextFragmentPtr(char *ptr)
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void
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FragmentAliasIn(char *ptr, /* Points to correctly de-aliased
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header fragment */
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char *ptr_fragment /* Points to fragment which must
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be de-aliased */
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)
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PacketAliasFragmentIn(char *ptr, /* Points to correctly de-aliased
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header fragment */
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char *ptr_fragment /* Points to fragment which must
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be de-aliased */
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)
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{
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struct ip *pip;
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struct ip *fpip;
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@ -967,6 +973,7 @@ PacketAliasIn(char *ptr, int maxpacketsize)
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int iresult;
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HouseKeeping();
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ClearCheckNewLink();
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pip = (struct ip *) ptr;
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alias_addr = pip->ip_dst;
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@ -1039,6 +1046,7 @@ PacketAliasOut(char *ptr, /* valid IP packet */
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struct ip *pip;
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HouseKeeping();
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ClearCheckNewLink();
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pip = (struct ip *) ptr;
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addr_save = GetDefaultAliasAddress();
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@ -1056,7 +1064,7 @@ PacketAliasOut(char *ptr, /* valid IP packet */
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else if (addr >= UNREG_ADDR_A_LOWER && addr <= UNREG_ADDR_A_UPPER)
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iclass = 1;
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if (iclass == 0)
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if (iclass != 0)
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{
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SetDefaultAliasAddress(pip->ip_src);
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}
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@ -1086,57 +1094,3 @@ PacketAliasOut(char *ptr, /* valid IP packet */
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SetDefaultAliasAddress(addr_save);
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return(iresult);
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}
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int
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PacketAliasIn2(char *ptr, /* valid IP packet */
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struct in_addr addr, /* Default aliasing address */
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int maxpacketsize /* How much the packet data may grow
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(FTP and IRC inline changes) */
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)
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{
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int result_code;
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struct in_addr addr_save;
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ClearNewDefaultLink();
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addr_save = GetDefaultAliasAddress();
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SetDefaultTargetAddress(addr);
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result_code = PacketAliasIn(ptr, maxpacketsize);
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ClearDefaultTargetAddress();
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if (result_code == PKT_ALIAS_OK)
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{
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if (CheckNewDefaultLink())
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return PKT_ALIAS_NEW_LINK;
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}
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return result_code;
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}
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int
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PacketAliasOut2(char *ptr, /* valid IP packet */
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struct in_addr addr, /* Default aliasing address */
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int maxpacketsize /* How much the packet data may grow
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(FTP and IRC inline changes) */
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)
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{
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int result_code;
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struct in_addr addr_save;
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ClearNewDefaultLink();
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addr_save = GetDefaultAliasAddress();
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SetDefaultAliasAddress(addr);
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result_code = PacketAliasOut(ptr, maxpacketsize);
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SetDefaultAliasAddress(addr_save);
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if (result_code == PKT_ALIAS_OK)
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{
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if (CheckNewDefaultLink())
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return PKT_ALIAS_NEW_LINK;
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}
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return result_code;
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}
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@ -12,45 +12,82 @@
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#ifndef _ALIAS_H_
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#define _ALIAS_H_
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/* Alias link representativei (incomplete struct) */
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#ifndef NULL
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#define NULL 0
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#endif
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/* Alias link representative (incomplete struct) */
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struct alias_link;
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/* External interfaces (API) to packet aliasing engine */
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/* Initialization and Control */
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extern void
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PacketAliasInit(void);
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extern void
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PacketAliasSetAddress(struct in_addr);
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extern unsigned int
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PacketAliasSetMode(unsigned int, unsigned int);
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/* Packet Handling */
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extern int
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PacketAliasIn(char *, int maxpacketsize);
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extern int
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PacketAliasOut(char *, int maxpacketsize);
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/* Port and Address Redirection */
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extern struct alias_link *
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PacketAliasRedirectPort(struct in_addr, u_short,
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struct in_addr, u_short,
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struct in_addr, u_short,
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u_char);
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extern struct alias_link *
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PacketAliasRedirectAddr(struct in_addr,
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struct in_addr);
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extern void
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PacketAliasRedirectDelete(struct alias_link *);
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/* Fragment Handling */
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extern int
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PacketAliasSaveFragment(char *);
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extern char *
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PacketAliasGetFragment(char *);
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extern void
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PacketAliasFragmentIn(char *, char *);
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/* Miscellaneous Functions */
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extern u_short
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PacketAliasInternetChecksum(u_short *, int);
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/*
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In version 2.2, the function names were rationalized
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to all be of the form PacketAlias... These are the
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old function names for backwards compatibility
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*/
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extern int SaveFragmentPtr(char *);
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extern char *GetNextFragmentPtr(char *);
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extern void FragmentAliasIn(char *, char *);
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extern int PacketAliasIn(char *, int maxpacketsize);
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extern int PacketAliasOut(char *, int maxpacketsize);
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extern int PacketAliasIn2(char *, struct in_addr, int maxpacketsize);
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extern int PacketAliasOut2(char *, struct in_addr, int maxpacketsize);
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extern void SetPacketAliasAddress(struct in_addr);
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extern void InitPacketAlias(void);
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extern void InitPacketAliasLog(void);
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extern void UninitPacketAliasLog(void);
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extern unsigned int SetPacketAliasMode(unsigned int, unsigned int);
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extern struct alias_link *
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PacketAliasRedirectPort(struct in_addr, u_short,
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struct in_addr, u_short,
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struct in_addr, u_short,
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u_char);
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extern int PacketAliasIn2(char *, struct in_addr, int maxpacketsize);
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extern int PacketAliasOut2(char *, struct in_addr, int maxpacketsize);
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extern int
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PacketAliasPermanentLink(struct in_addr, u_short,
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struct in_addr, u_short,
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u_short, u_char);
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extern struct alias_link *
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PacketAliasRedirectAddr(struct in_addr,
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struct in_addr);
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void PacketAliasRedirectDelete(struct alias_link *);
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/* InternetChecksum() is not specifically part of the
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packet aliasing API, but is sometimes needed outside
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the module. (~for instance, natd uses it to create
|
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an ICMP error message when interface size is
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exceeded.) */
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extern u_short InternetChecksum(u_short *, int);
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/* Obsolete constant */
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#define PKT_ALIAS_NEW_LINK 5
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/********************** Mode flags ********************/
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/* Set these flags using SetPacketAliasMode() */
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@ -58,25 +95,28 @@ extern u_short InternetChecksum(u_short *, int);
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/* If PKT_ALIAS_LOG is set, a message will be printed to
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/var/log/alias.log every time a link is created or deleted. This
|
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is useful for debugging */
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#define PKT_ALIAS_LOG 1
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#define PKT_ALIAS_LOG 0x01
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/* If PKT_ALIAS_DENY_INCOMING is set, then incoming connections (e.g.
|
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to ftp, telnet or web servers will be prevented by the aliasing
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mechanism. */
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#define PKT_ALIAS_DENY_INCOMING 2
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#define PKT_ALIAS_DENY_INCOMING 0x02
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|
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/* If PKT_ALIAS_SAME_PORTS is set, packets will be attempted sent from
|
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the same port as they originated on. This allow eg rsh to work
|
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the same port as they originated on. This allows eg rsh to work
|
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*99% of the time*, but _not_ 100%. (It will be slightly flakey
|
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instead of not working at all.) */
|
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#define PKT_ALIAS_SAME_PORTS 4
|
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instead of not working at all.) This mode bit is set by
|
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PacketAliasInit(), so it is a default mode of operation. */
|
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#define PKT_ALIAS_SAME_PORTS 0x04
|
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|
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/* If PKT_ALIAS_USE_SOCKETS is set, then when partially specified
|
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links (e.g. destination port and/or address is zero), the packet
|
||||
aliasing engine will attempt to allocate a socket for the aliasing
|
||||
port it chooses. This will avoid interference with the host
|
||||
machine. Fully specified links do not require this. */
|
||||
#define PKT_ALIAS_USE_SOCKETS 8
|
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machine. Fully specified links do not require this. This bit
|
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is set after a call to PacketAliasInit(), so it is a default
|
||||
mode of operation.*/
|
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#define PKT_ALIAS_USE_SOCKETS 0x08
|
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|
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/* If PKT_ALIAS_UNREGISTERED_ONLY is set, then only packets with with
|
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unregistered source addresses will be aliased (along with those
|
||||
@ -86,9 +126,15 @@ extern u_short InternetChecksum(u_short *, int);
|
||||
10.0.0.0 -> 10.255.255.255
|
||||
172.16.0.0 -> 172.31.255.255
|
||||
192.168.0.0 -> 192.168.255.255 */
|
||||
#define PKT_ALIAS_UNREGISTERED_ONLY 16
|
||||
|
||||
#define PKT_ALIAS_UNREGISTERED_ONLY 0x10
|
||||
|
||||
/* If PKT_ALIAS_RESET_ON_ADDR_CHANGE is set, then the table of dynamic
|
||||
aliasing links will be reset whenever PacketAliasSetAddress()
|
||||
changes the default aliasing address. If the default aliasing
|
||||
address is left unchanged by this functions call, then the
|
||||
table of dynamic aliasing links will be left intact. This
|
||||
bit is set after a call to PacketAliasInit(). */
|
||||
#define PKT_ALIAS_RESET_ON_ADDR_CHANGE 0x20
|
||||
|
||||
/* Return Codes */
|
||||
#define PKT_ALIAS_ERROR -1
|
||||
@ -96,7 +142,6 @@ extern u_short InternetChecksum(u_short *, int);
|
||||
#define PKT_ALIAS_IGNORED 2
|
||||
#define PKT_ALIAS_UNRESOLVED_FRAGMENT 3
|
||||
#define PKT_ALIAS_FOUND_HEADER_FRAGMENT 4
|
||||
#define PKT_ALIAS_NEW_LINK 5
|
||||
|
||||
#endif
|
||||
/*lint -restore */
|
||||
|
||||
@ -249,8 +249,8 @@ struct alias_link /* Main data structure */
|
||||
|
||||
union /* Auxiliary data */
|
||||
{
|
||||
struct in_addr frag_addr;
|
||||
char *frag_ptr;
|
||||
struct in_addr frag_addr;
|
||||
struct tcp_dat *tcp;
|
||||
} data;
|
||||
};
|
||||
@ -755,6 +755,8 @@ DeleteLink(struct alias_link *link)
|
||||
break;
|
||||
case LINK_FRAGMENT_PTR:
|
||||
fragmentPtrLinkCount--;
|
||||
if (link->data.frag_ptr != NULL)
|
||||
free(link->data.frag_ptr);
|
||||
break;
|
||||
}
|
||||
|
||||
@ -1351,8 +1353,6 @@ FindAliasAddress(struct in_addr original_addr)
|
||||
GetOriginalPort(), GetAliasPort()
|
||||
SetAckModified(), GetAckModified()
|
||||
GetDeltaAckIn(), GetDeltaSeqOut(), AddSeq()
|
||||
ClearNewLink()
|
||||
CheckNewLink()
|
||||
*/
|
||||
|
||||
|
||||
@ -1457,19 +1457,6 @@ SetDefaultAliasAddress(struct in_addr alias_addr)
|
||||
}
|
||||
|
||||
|
||||
void
|
||||
SetDefaultTargetAddress(struct in_addr target_addr)
|
||||
{
|
||||
targetAddress = target_addr;
|
||||
}
|
||||
|
||||
|
||||
void ClearDefaultTargetAddress(void)
|
||||
{
|
||||
targetAddress.s_addr = 0;
|
||||
}
|
||||
|
||||
|
||||
u_short
|
||||
GetOriginalPort(struct alias_link *link)
|
||||
{
|
||||
@ -1661,19 +1648,18 @@ SetExpire(struct alias_link *link, int expire)
|
||||
}
|
||||
|
||||
void
|
||||
ClearNewDefaultLink(void)
|
||||
ClearCheckNewLink(void)
|
||||
{
|
||||
newDefaultLink = 0;
|
||||
}
|
||||
|
||||
|
||||
int
|
||||
CheckNewDefaultLink(void)
|
||||
{
|
||||
return newDefaultLink;
|
||||
}
|
||||
|
||||
/* Miscellaneous Functions
|
||||
|
||||
HouseKeeping()
|
||||
InitPacketAliasLog()
|
||||
UninitPacketAliasLog()
|
||||
*/
|
||||
|
||||
/*
|
||||
Whenever an outgoing or incoming packet is handled, HouseKeeping()
|
||||
@ -1734,6 +1720,31 @@ HouseKeeping(void)
|
||||
}
|
||||
|
||||
|
||||
/* Init the log file and enable logging */
|
||||
void
|
||||
InitPacketAliasLog(void)
|
||||
{
|
||||
if ((~packetAliasMode & PKT_ALIAS_LOG)
|
||||
&& (monitorFile = fopen("/var/log/alias.log", "w")))
|
||||
{
|
||||
packetAliasMode |= PKT_ALIAS_LOG;
|
||||
fprintf(monitorFile,
|
||||
"PacketAlias/InitPacketAliasLog: Packet alias logging enabled.\n");
|
||||
}
|
||||
}
|
||||
|
||||
|
||||
/* Close the log-file and disable logging. */
|
||||
void
|
||||
UninitPacketAliasLog(void)
|
||||
{
|
||||
if( monitorFile )
|
||||
fclose(monitorFile);
|
||||
packetAliasMode &= ~PKT_ALIAS_LOG;
|
||||
}
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
@ -1743,11 +1754,10 @@ HouseKeeping(void)
|
||||
|
||||
PacketAliasRedirectPort()
|
||||
PacketAliasRedirectAddr()
|
||||
SetPacketAliasAddress()
|
||||
InitPacketAliasLog()
|
||||
UninitPacketAliasLog()
|
||||
InitPacketAlias()
|
||||
SetPacketAliasMode()
|
||||
PacketAliasRedirectDelete()
|
||||
PacketAliasSetAddress()
|
||||
PacketAliasInit()
|
||||
PacketAliasSetMode()
|
||||
|
||||
(prototypes in alias.h)
|
||||
*/
|
||||
@ -1795,28 +1805,6 @@ PacketAliasRedirectPort(struct in_addr src_addr, u_short src_port,
|
||||
}
|
||||
|
||||
|
||||
/* This function is slightly less generalized than
|
||||
PacketAliasRedirectPort and is included for backwards
|
||||
compatibility */
|
||||
int
|
||||
PacketAliasPermanentLink(struct in_addr src_addr, u_short src_port,
|
||||
struct in_addr dst_addr, u_short dst_port,
|
||||
u_short alias_port, u_char proto)
|
||||
{
|
||||
struct alias_link *link;
|
||||
|
||||
link = PacketAliasRedirectPort(src_addr, src_port,
|
||||
dst_addr, dst_port,
|
||||
nullAddress, alias_port,
|
||||
proto);
|
||||
|
||||
if (link == NULL)
|
||||
return -1;
|
||||
else
|
||||
return 0;
|
||||
}
|
||||
|
||||
|
||||
/* Static address translation */
|
||||
struct alias_link *
|
||||
PacketAliasRedirectAddr(struct in_addr src_addr,
|
||||
@ -1845,7 +1833,7 @@ PacketAliasRedirectAddr(struct in_addr src_addr,
|
||||
void
|
||||
PacketAliasRedirectDelete(struct alias_link *link)
|
||||
{
|
||||
/* This is a very dangerous function to put in the API,
|
||||
/* This is a dangerous function to put in the API,
|
||||
because an invalid pointer can crash the program. */
|
||||
|
||||
deleteAllLinks = 1;
|
||||
@ -1855,9 +1843,10 @@ PacketAliasRedirectDelete(struct alias_link *link)
|
||||
|
||||
|
||||
void
|
||||
SetPacketAliasAddress(struct in_addr addr)
|
||||
PacketAliasSetAddress(struct in_addr addr)
|
||||
{
|
||||
if (aliasAddress.s_addr != addr.s_addr)
|
||||
if (packetAliasMode & PKT_ALIAS_RESET_ON_ADDR_CHANGE
|
||||
&& aliasAddress.s_addr != addr.s_addr)
|
||||
{
|
||||
CleanupAliasData();
|
||||
aliasAddress = addr;
|
||||
@ -1865,32 +1854,15 @@ SetPacketAliasAddress(struct in_addr addr)
|
||||
}
|
||||
|
||||
|
||||
/* Init the log file and enable logging */
|
||||
void
|
||||
InitPacketAliasLog(void)
|
||||
PacketAliasSetTarget(struct in_addr target_addr)
|
||||
{
|
||||
if ((~packetAliasMode & PKT_ALIAS_LOG)
|
||||
&& (monitorFile = fopen("/var/log/alias.log", "w")))
|
||||
{
|
||||
packetAliasMode |= PKT_ALIAS_LOG;
|
||||
fprintf(monitorFile,
|
||||
"PacketAlias/InitPacketAliasLog: Packet alias logging enabled.\n");
|
||||
}
|
||||
}
|
||||
|
||||
|
||||
/* Close the log-file and disable logging. */
|
||||
void
|
||||
UninitPacketAliasLog(void)
|
||||
{
|
||||
if( monitorFile )
|
||||
fclose(monitorFile);
|
||||
packetAliasMode &= ~PKT_ALIAS_LOG;
|
||||
targetAddress = target_addr;
|
||||
}
|
||||
|
||||
|
||||
void
|
||||
InitPacketAlias(void)
|
||||
PacketAliasInit(void)
|
||||
{
|
||||
int i;
|
||||
struct timeval tv;
|
||||
@ -1918,6 +1890,7 @@ InitPacketAlias(void)
|
||||
}
|
||||
|
||||
aliasAddress.s_addr = 0;
|
||||
targetAddress.s_addr = 0;
|
||||
|
||||
icmpLinkCount = 0;
|
||||
udpLinkCount = 0;
|
||||
@ -1929,19 +1902,14 @@ InitPacketAlias(void)
|
||||
cleanupIndex =0;
|
||||
|
||||
packetAliasMode = PKT_ALIAS_SAME_PORTS
|
||||
| PKT_ALIAS_USE_SOCKETS;
|
||||
|
||||
if (packetAliasMode & PKT_ALIAS_LOG)
|
||||
{
|
||||
InitPacketAliasLog();
|
||||
fprintf(monitorFile, "Packet aliasing initialized.\n");
|
||||
}
|
||||
| PKT_ALIAS_USE_SOCKETS
|
||||
| PKT_ALIAS_RESET_ON_ADDR_CHANGE;
|
||||
}
|
||||
|
||||
|
||||
/* Change mode for some operations */
|
||||
unsigned int
|
||||
SetPacketAliasMode
|
||||
PacketAliasSetMode
|
||||
(
|
||||
unsigned int flags, /* Which state to bring flags to */
|
||||
unsigned int mask /* Mask of which flags to affect (use 0 to do a
|
||||
@ -1964,9 +1932,8 @@ SetPacketAliasMode
|
||||
}
|
||||
|
||||
|
||||
/*
|
||||
Clear all packet aliasing links, but leave mode
|
||||
flags unchanged. Typically used when the interface
|
||||
address changes and all existing links become
|
||||
invalid.
|
||||
*/
|
||||
int
|
||||
PacketAliasCheckNewLink(void)
|
||||
{
|
||||
return newDefaultLink;
|
||||
}
|
||||
|
||||
@ -68,8 +68,6 @@ struct in_addr GetDestAddress(struct alias_link *);
|
||||
struct in_addr GetAliasAddress(struct alias_link *);
|
||||
struct in_addr GetDefaultAliasAddress(void);
|
||||
void SetDefaultAliasAddress(struct in_addr);
|
||||
void SetDefaultTargetAddress(struct in_addr);
|
||||
void ClearDefaultTargetAddress(void);
|
||||
u_short GetOriginalPort(struct alias_link *);
|
||||
u_short GetAliasPort(struct alias_link *);
|
||||
void SetAckModified(struct alias_link *);
|
||||
@ -78,8 +76,7 @@ int GetDeltaAckIn(struct ip *, struct alias_link *);
|
||||
int GetDeltaSeqOut(struct ip *, struct alias_link *);
|
||||
void AddSeq(struct ip *, struct alias_link *, int);
|
||||
void SetExpire(struct alias_link *, int);
|
||||
void ClearNewDefaultLink(void);
|
||||
int CheckNewDefaultLink(void);
|
||||
void ClearCheckNewLink(void);
|
||||
|
||||
/* Housekeeping function */
|
||||
void HouseKeeping(void);
|
||||
@ -88,4 +85,9 @@ void HouseKeeping(void);
|
||||
/*lint -save -library Suppress flexelint warnings */
|
||||
void AliasHandleFtpOut(struct ip *, struct alias_link *, int);
|
||||
void AliasHandleIrcOut(struct ip *pip, struct alias_link *link, int maxsize );
|
||||
|
||||
/* Log file control */
|
||||
void InitPacketAliasLog(void);
|
||||
void UninitPacketAliasLog(void);
|
||||
|
||||
/*lint -restore */
|
||||
|
||||
77
lib/libalias/alias_old.c
Normal file
77
lib/libalias/alias_old.c
Normal file
@ -0,0 +1,77 @@
|
||||
/*
|
||||
This file can be considered a junk pile of old functions that
|
||||
are either obsolete or have had their names changed. In the
|
||||
transition from alias2.1 to alias2.2, all the function names
|
||||
were rationalized so that they began with "PacketAlias..."
|
||||
|
||||
These functions are included for backwards compatibility.
|
||||
*/
|
||||
|
||||
#include <sys/types.h>
|
||||
#include <netinet/in_systm.h>
|
||||
#include <netinet/in.h>
|
||||
#include <netinet/ip.h>
|
||||
#include "alias.h"
|
||||
#include "alias_local.h"
|
||||
|
||||
void
|
||||
InitPacketAlias(void)
|
||||
{
|
||||
PacketAliasInit();
|
||||
}
|
||||
|
||||
void
|
||||
SetPacketAliasAddress(struct in_addr addr)
|
||||
{
|
||||
PacketAliasSetAddress(addr);
|
||||
}
|
||||
|
||||
unsigned int
|
||||
SetPacketAliasMode(unsigned int flags, unsigned int mask)
|
||||
{
|
||||
return PacketAliasSetMode(flags, mask);
|
||||
}
|
||||
|
||||
int
|
||||
PacketAliasPermanentLink(struct in_addr src_addr, u_short src_port,
|
||||
struct in_addr dst_addr, u_short dst_port,
|
||||
u_short alias_port, u_char proto)
|
||||
{
|
||||
struct alias_link *link;
|
||||
struct in_addr null_address;
|
||||
|
||||
null_address.s_addr = 0;
|
||||
link = PacketAliasRedirectPort(src_addr, src_port,
|
||||
dst_addr, dst_port,
|
||||
null_address, alias_port,
|
||||
proto);
|
||||
|
||||
if (link == NULL)
|
||||
return -1;
|
||||
else
|
||||
return 0;
|
||||
}
|
||||
|
||||
int
|
||||
SaveFragmentPtr(char *ptr)
|
||||
{
|
||||
return PacketAliasSaveFragment(ptr);
|
||||
}
|
||||
|
||||
char *
|
||||
GetNextFragmentPtr(char *ptr)
|
||||
{
|
||||
return PacketAliasGetFragment(ptr);
|
||||
}
|
||||
|
||||
void
|
||||
FragmentAliasIn(char *header, char *fragment)
|
||||
{
|
||||
PacketAliasFragmentIn(header, fragment);
|
||||
}
|
||||
|
||||
u_short
|
||||
InternetChecksum(u_short *ptr, int len)
|
||||
{
|
||||
return PacketAliasInternetChecksum(ptr, len);
|
||||
}
|
||||
@ -26,10 +26,11 @@ purposes);
|
||||
#include <netinet/ip.h>
|
||||
#include <netinet/tcp.h>
|
||||
|
||||
#include "alias.h"
|
||||
#include "alias_local.h"
|
||||
|
||||
u_short
|
||||
InternetChecksum(u_short *ptr, int nbytes)
|
||||
PacketAliasInternetChecksum(u_short *ptr, int nbytes)
|
||||
{
|
||||
int sum, oddbyte;
|
||||
|
||||
@ -53,7 +54,8 @@ InternetChecksum(u_short *ptr, int nbytes)
|
||||
u_short
|
||||
IpChecksum(struct ip *pip)
|
||||
{
|
||||
return( InternetChecksum((u_short *) pip, (pip->ip_hl << 2)) );
|
||||
return( PacketAliasInternetChecksum((u_short *) pip,
|
||||
(pip->ip_hl << 2)) );
|
||||
|
||||
}
|
||||
|
||||
|
||||
722
lib/libalias/libalias.3
Normal file
722
lib/libalias/libalias.3
Normal file
@ -0,0 +1,722 @@
|
||||
.Dd July, 1997
|
||||
.Dt "libalias" 3
|
||||
.Os
|
||||
.Sh NAME
|
||||
.Nm "libalias"
|
||||
Packet Aliasing Library. A collection of
|
||||
functions for aliasing and de-aliasing
|
||||
of IP packets, intended for masquerading and
|
||||
network address translation (NAT).
|
||||
|
||||
.Sh SYNOPSIS
|
||||
.Fd #include <netinet/in.h>
|
||||
.Fd #include <alias.h>
|
||||
|
||||
Function prototypes are given in the main body
|
||||
of the text.
|
||||
|
||||
.Sh CONTENTS
|
||||
.Bd -literal -offset left
|
||||
1. Introduction
|
||||
2. Initialization and Control
|
||||
2.1 PacketAliasInit()
|
||||
2.2 PacketAliasSetAddress()
|
||||
2.3 PacketAliasSetMode()
|
||||
3. Packet Handling
|
||||
3.1 PacketAliasOut()
|
||||
3.2 PacketAliasIn()
|
||||
4. Port and Address Redirection
|
||||
4.1 PacketAliasRedirectPort()
|
||||
4.2 PacketAliasRedirectAddr()
|
||||
4.3 PacketAliasRedirectDelete()
|
||||
5. Fragment Handling
|
||||
5.1 PacketAliasSaveFragment()
|
||||
5.2 PacketAliasGetFragment()
|
||||
5.3 PacketAliasFragmentIn()
|
||||
6. Miscellaneous Functions
|
||||
6.1 PacketAliasSetTarget()
|
||||
6.2 PacketAliasCheckNewLink()
|
||||
6.3 PacketAliasInternetChecksum()
|
||||
7. Authors
|
||||
8. Acknowledgments
|
||||
|
||||
Appendix A: Conceptual Background
|
||||
A.1 Aliasing Links
|
||||
A.2 Static and Dynamic Links
|
||||
A.3 Partially Specified Links
|
||||
A.4 Dynamic Link Creation
|
||||
.Ed
|
||||
|
||||
.Sh 1. Introduction
|
||||
This library is a moderately portable
|
||||
set of functions designed to assist
|
||||
in the process of IP masquerading and
|
||||
network address translation. Outgoing
|
||||
packets from a local network with
|
||||
unregistered IP addresses can be aliased
|
||||
to appear as if they came from an
|
||||
accessible IP address. Incoming packets
|
||||
are then de-aliased so that they are sent
|
||||
to the correct machine on the local network.
|
||||
|
||||
A certain amount of flexibility is built
|
||||
into the packet aliasing engine. In
|
||||
the simplest mode of operation, a
|
||||
many-to-one address mapping takes place
|
||||
between local network and the packet
|
||||
aliasing host. This is known as IP
|
||||
masquerading. In addition, one-to-one
|
||||
mappings between local and public addresses
|
||||
can also be implemented, which is known as
|
||||
static NAT. In between these extremes,
|
||||
different groups of private addresses
|
||||
can be linked to different public addresses,
|
||||
comprising several distinct many-to-one
|
||||
mappings. Also, a given public address
|
||||
and port can be staticly redirected to
|
||||
a private address/port.
|
||||
|
||||
The packet aliasing engine was designed
|
||||
to operate in user space outside of the
|
||||
kernel, without any access to private
|
||||
kernel data structure, but the source code
|
||||
can also be ported to a kernel environment.
|
||||
|
||||
.Sh 2. Initialization and Control
|
||||
Two specific functions, PacketAliasInit()
|
||||
and PacketAliasSetAddress(), must always be
|
||||
called before any packet handling may be
|
||||
performed. In addition, the operating mode
|
||||
of the packet aliasing engine can be customized
|
||||
by calling PacketAliasSetMode().
|
||||
.Ss 2.1 PacketAliasInit()
|
||||
|
||||
.Ft void
|
||||
.Fn PacketAliasInit "void"
|
||||
|
||||
This function has no argument or return
|
||||
value and is used to initialize internal
|
||||
data structures. The following mode bits
|
||||
are always set after calling
|
||||
PacketAliasInit(). See section 2.3 for
|
||||
the meaning of these mode bits.
|
||||
.Bd -literal -offset indent
|
||||
PKT_ALIAS_USE_SAME_PORTS
|
||||
PKT_ALIAS_USE_SOCKETS
|
||||
PKT_ALIAS_RESET_ON_ADDR_CHANGE
|
||||
|
||||
.Ed
|
||||
This function will always return the packet
|
||||
aliasing engine to the same initial state.
|
||||
PacketAliasSetAddress() must be called afterwards,
|
||||
and any desired changes from the default mode
|
||||
bits listed above require a call to
|
||||
PacketAliasSetMode().
|
||||
|
||||
It is mandatory that this function be called
|
||||
at the beginning of a program prior to any
|
||||
packet handling.
|
||||
.Ss 2.2 PacketAliasSetAddress()
|
||||
|
||||
.Ft void
|
||||
.Fn PacketAliasSetAddress "struct in_addr addr"
|
||||
|
||||
This function sets the source address to which
|
||||
outgoing packets from the local area network
|
||||
are aliased. All outgoing packets are remapped
|
||||
to this address unless overridden by a static
|
||||
address mapping established by
|
||||
PacketAliasRedirectAddr().
|
||||
|
||||
If the PKT_ALIAS_RESET_ON_ADDR_CHANGE mode bit
|
||||
is set (the default mode of operation), then
|
||||
the internal aliasing link tables will be reset
|
||||
any time the aliasing address changes, as if
|
||||
PacketAliasReset() were called. This is useful
|
||||
for interfaces such as ppp where the IP
|
||||
address may or may not change on successive
|
||||
dial-up attempts.
|
||||
|
||||
If the PKT_ALIAS_RESET_ON_ADDR_CHANGE mode bit
|
||||
is set to zero, this function can also be used to
|
||||
dynamically change the aliasing address on a
|
||||
packet to packet basis (it is a low overhead
|
||||
call).
|
||||
|
||||
It is mandatory that this function be called
|
||||
prior to any packet handling.
|
||||
.Ss 2.3 PacketAliasSetMode()
|
||||
|
||||
.Ft void
|
||||
.Fn PacketAliasSetMode "int mode" "int mask"
|
||||
|
||||
This function sets or clears mode bits
|
||||
according to the value of
|
||||
.Em mode .
|
||||
Only bits marked in
|
||||
.Em mask
|
||||
are affected. The following mode bits are
|
||||
defined in alias.h:
|
||||
.Bl -hang -offset left
|
||||
.It PKT_ALIAS_LOG.
|
||||
Enables logging /var/log/alias.log. The log file
|
||||
shows total numbers of links (icmp, tcp, udp) each
|
||||
time an aliasing link is created or deleted. Mainly
|
||||
useful for debugging when the log file is viewed
|
||||
continuously with "tail -f".
|
||||
.It PKT_ALIAS_DENY_INCOMING.
|
||||
If this mode bit is set, all incoming packets
|
||||
associated with new TCP connections or new
|
||||
UDP transactions will be marked for being
|
||||
ignored (PacketAliasIn() return code
|
||||
PKT_ALIAS_IGNORED) by the calling program.
|
||||
Response packets to connections or transactions
|
||||
initiated from the packet aliasing host or
|
||||
local network will be unaffected. This mode
|
||||
bit is useful for implementing a one-way firewall.
|
||||
.It PKT_ALIAS_SAME_PORTS.
|
||||
If this mode bit is set, the packet aliasing
|
||||
engine will attempt to leave the alias port
|
||||
numbers unchanged from the actual local port
|
||||
number. This can be done as long as the
|
||||
quintuple (proto, alias addr, alias port,
|
||||
remote addr, remote port) is unique. If a
|
||||
conflict exists, an new aliasing port number is
|
||||
chosen even if this mode bit is set.
|
||||
.It PKT_ALIAS_USE_SOCKETS.
|
||||
This bit should be set when the the packet
|
||||
aliasing host originates network traffic as
|
||||
well as forwards it. When the packet aliasing
|
||||
host is waiting for a connection from an
|
||||
unknown host address or unknown port number
|
||||
(e.g. an FTP data connection), this mode bit
|
||||
specifies that a socket be allocated as a place
|
||||
holder to prevent port conflicts. Once a
|
||||
connection is extablished, usually within a
|
||||
minute or so, the socket is closed.
|
||||
.It PKT_ALIAS_UNREGISTERED_ONLY.
|
||||
If this mode bit is set, traffic on the
|
||||
local network which does not originate from
|
||||
unregistered address spaces will be ignored.
|
||||
Standard Class A, B and C unregistered addresses
|
||||
are:
|
||||
.Bd -literal -offset indent
|
||||
10.0.0.0 -> 10.255.255.255 (Class A subnet)
|
||||
172.16.0.0 -> 172.31.255.255 (Class B subnets)
|
||||
192.168.0.0 -> 192.168.255.255 (Class C subnets)
|
||||
|
||||
.Ed
|
||||
This option is useful in the case that
|
||||
packet aliasing host has both registered and
|
||||
unregistered subnets on different interfaces.
|
||||
The registered subnet is fully accessible to
|
||||
the outside world, so traffic from it doesn't
|
||||
need to be passed through the packet aliasing
|
||||
engine.
|
||||
.It PKT_ALIAS_RESET_ON_ADDR_CHANGE.
|
||||
When this mode bit is set and
|
||||
PacketAliasSetAddress() is called to change
|
||||
the aliasing address, the internal link table
|
||||
of the packet aliasing engine will be cleared.
|
||||
This operating mode is useful for ppp links
|
||||
where the interface address can sometimes
|
||||
change or remain the same between dial-ups.
|
||||
If this mode bit is not set, it the link table
|
||||
will never be reset in the event of an
|
||||
address change.
|
||||
.El
|
||||
.Sh 3. Packet Handling
|
||||
The packet handling functions are used to
|
||||
modify incoming (remote->local) and outgoing
|
||||
(local->remote) packets. The calling program
|
||||
is responsible for receiving and sending
|
||||
packets via network interfaces.
|
||||
|
||||
Along with PacketAliasInit() and PacketAliasSetAddress(),
|
||||
the two packet handling functions, PacketAliasIn()
|
||||
and PacketAliasOut(), comprise minimal set of functions
|
||||
needed for a basic IP masquerading implementation.
|
||||
.Ss 3.1 PacketAliasIn()
|
||||
|
||||
.Ft int
|
||||
.Fn PacketAliasIn "char *buffer" "int maxpacketsize"
|
||||
|
||||
An incoming packet coming from a remote machine to
|
||||
the local network is de-aliased by this function.
|
||||
The IP packet is pointed to by
|
||||
.Em buffer ,
|
||||
and
|
||||
.Em maxpacketsize
|
||||
indicates the size of the data structure containing
|
||||
the packet and should be at least as large as the
|
||||
actual packet size.
|
||||
|
||||
Return codes:
|
||||
.Bl -hang -offset left
|
||||
.It PKT_ALIAS_ERROR.
|
||||
An internal error within the packet aliasing
|
||||
engine occured.
|
||||
.It PKT_ALIAS_OK.
|
||||
The packet aliasing process was successful.
|
||||
.It PKT_ALIAS_IGNORED.
|
||||
The packet was ignored and not de-aliased.
|
||||
This can happen if the protocal is unrecognized,
|
||||
possibly an ICMP message type is not handled or
|
||||
if incoming packets for new connections are being
|
||||
ignored (see PKT_ALIAS_DENY_INCOMING in section
|
||||
2.2).
|
||||
.It PKT_ALIAS_UNRESOLVED_FRAGMENT.
|
||||
This is returned when a fragment cannot be
|
||||
resolved because the header fragment has not
|
||||
been sent yet. In this situation, fragments
|
||||
must be saved with PacketAliasSaveFragment()
|
||||
until a header fragment is found.
|
||||
.It PKT_ALIAS_FOUND_HEADER_FRAGMENT.
|
||||
The packet aliasing process was successful,
|
||||
and a header fragment was found. This is a
|
||||
signal to retrieve any unresolved fragments
|
||||
with PacketAliasGetFragment() and de-alias
|
||||
them with PacketAliasFragmentIn().
|
||||
.El
|
||||
.Ss 3.2 PacketAliasOut()
|
||||
|
||||
.Ft int
|
||||
.Fn PacketAliasIn "char *buffer" "int maxpacketsize"
|
||||
|
||||
An outgoing packet coming from the local network
|
||||
to a remote machine is aliased by this function.
|
||||
The IP packet is pointed to by
|
||||
.Em buffer r,
|
||||
and
|
||||
.Em maxpacketsize
|
||||
indicates the maximum packet size permissable
|
||||
should the packet length be changed. IP encoding
|
||||
protocols place addresss and port information in
|
||||
the encapsulated data stream which have to be
|
||||
modified and can account for changes in packet
|
||||
length. Well known examples of such protocols
|
||||
are FTP and IRC.
|
||||
|
||||
Return codes:
|
||||
.Bl -hang -offset left
|
||||
.It PKT_ALIAS_ERROR.
|
||||
An internal error within the packet aliasing
|
||||
engine occured.
|
||||
.It PKT_ALIAS_OK.
|
||||
The packet aliasing process was successful.
|
||||
.It PKT_ALIAS_IGNORED.
|
||||
The packet was ignored and not de-aliased.
|
||||
This can happen if the protocal is unrecognized,
|
||||
or possibly an ICMP message type is not handled.
|
||||
.El
|
||||
|
||||
.Sh 4. Port and Address Redirection
|
||||
The functions described in this section allow machines
|
||||
on the local network to be accessible in some degree
|
||||
to new incoming connections from the external network.
|
||||
Individual ports can be re-mapped or static network
|
||||
address translations can be designated.
|
||||
.Ss 4.1 PacketAliasRedirectPort()
|
||||
|
||||
.Ft struct alias_link *
|
||||
.Fo PacketAliasRedirectPort
|
||||
.Fa "struct in_addr local_addr"
|
||||
.Fa "u_short local_port"
|
||||
.Fa "struct in_addr remote_addr"
|
||||
.Fa "u_short remote_port"
|
||||
.Fa "struct in_addr alias_addr"
|
||||
.Fa "u_short alias_port"
|
||||
.Fa "u_char proto"
|
||||
.Fc
|
||||
|
||||
This function specifies that traffic from a
|
||||
given remote address/port to an alias address/port
|
||||
be redirected to a specified local address/port.
|
||||
The paramater
|
||||
.Em proto
|
||||
can be either IPPROTO_TCP or IPPROTO_UDP, as
|
||||
defined in <netinet/in.h>.
|
||||
|
||||
If
|
||||
.Em local_addr
|
||||
or
|
||||
.Em alias_addr
|
||||
is zero, this indicates that the packet aliasing
|
||||
address as established by PacketAliasSetAddress()
|
||||
is to be used. Even if PacketAliasAddress() is
|
||||
called to change the address after PacketAliasRedirectPort()
|
||||
is called, a zero reference will track this change.
|
||||
|
||||
If
|
||||
.Em remote_addr
|
||||
is zero, this indicates to redirect packets from
|
||||
any remote address. Likewise, if
|
||||
.Em remote_port
|
||||
is zero, this indicates to redirect packets originating
|
||||
from any remote port number. Almost always, the remote
|
||||
port specification will be zero, but non-zero remote
|
||||
addresses can be sometimes be useful for firewalling.
|
||||
If two calls to PacketAliasRedirectPort() overlap in
|
||||
their address/port specifications, then the most recent
|
||||
call will have precedence.
|
||||
|
||||
This function returns a pointer which can subsequently
|
||||
be used by PacketAliasRedirectDelete(). If NULL is
|
||||
returned, then the function call did not complete
|
||||
successfully.
|
||||
|
||||
All port numbers are in network address byte order,
|
||||
so it is necessary to use htons() to convert these
|
||||
parameters from internally readable numbers to
|
||||
network byte order. Addresses are also in network
|
||||
byte order, which is implicit in the use of the
|
||||
.Em struct in_addr
|
||||
data type.
|
||||
.Ss 4.2 PacketAliasRedirectAddr()
|
||||
|
||||
.Ft struct alias_link *
|
||||
.Fo PacketAliasRedirectAddress
|
||||
.Fa "struct in_addr local_addr"
|
||||
.Fa "struct in_addr alias_addr"
|
||||
.Fc
|
||||
|
||||
This function desgnates that all incoming
|
||||
traffic to
|
||||
.Em alias_addr
|
||||
be redirected to
|
||||
.Em local_addr.
|
||||
Similarly, all outgoing traffic from
|
||||
.Em local_addr
|
||||
is aliased to
|
||||
.Em alias_addr .
|
||||
|
||||
If
|
||||
.Em local_addr
|
||||
or
|
||||
.Em alias_addr
|
||||
is zero, this indicates that the packet aliasing
|
||||
address as established by PacketAliasSetAddress()
|
||||
is to be used. Even if PacketAliasAddress() is
|
||||
called to change the address after PacketAliasRedirectAddr()
|
||||
is called, a zero reference will track this change.
|
||||
|
||||
If subsequent calls to PacketAliasRedirectAddr()
|
||||
use the same aliasing address, all new incoming
|
||||
traffic to this aliasing address will be redirected
|
||||
to the local address made in the last function call,
|
||||
but new traffic all of the local machines designated
|
||||
in the several function calls will be aliased to
|
||||
the same address. Consider the following example:
|
||||
.Bd -literal -offset left
|
||||
PacketAliasRedirectAddr(inet_aton("192.168.0.2"),
|
||||
inet_aton("141.221.254.101"));
|
||||
PacketAliasRedirectAddr(inet_aton("192.168.0.3"),
|
||||
inet_aton("141.221.254.101"));
|
||||
PacketAliasRedirectAddr(inet_aton("192.168.0.4"),
|
||||
inet_aton("141.221.254.101"));
|
||||
.Ed
|
||||
|
||||
Any outgoing connections such as telnet or ftp
|
||||
from 192.168.0.2, 102.168.0.3, 192.168.0.4 will
|
||||
appear to come from 141.221.254.101. Any incoming
|
||||
connections to 141.221.254.101 will be directed
|
||||
to 192.168.0.4.
|
||||
|
||||
Any calls to PacketAliasRedirectPort() will
|
||||
have precedence over address mappings designated
|
||||
by PacketAliasRedirectAddr().
|
||||
|
||||
This function returns a pointer which can subsequently
|
||||
be used by PacketAliasRedirectDelete(). If NULL is
|
||||
returned, then the function call did not complete
|
||||
successfully.
|
||||
.Ss 4.3 PacketAliasRedirectDelete()
|
||||
|
||||
.Ft void
|
||||
.Fn PacketAliasRedirectDelete "struct alias_link *ptr"
|
||||
|
||||
This function will delete a specific static redirect
|
||||
rule entered by PacketAliasRedirectPort() or
|
||||
PacketAliasRedirectAddr(). The parameter
|
||||
.Em ptr
|
||||
is the pointer returned by either of the redirection
|
||||
functions. If an invalid pointer is passed to
|
||||
PacketAliasRedirectDelete(), then a program crash
|
||||
or unpredictable operation could result, so it is
|
||||
necessary to be careful using this function.
|
||||
|
||||
.Sh 5. Fragment Handling
|
||||
The functions in this section are used to deal with
|
||||
incoming fragments.
|
||||
|
||||
Outgoing fragments are handled within PacketAliasOut()
|
||||
by changing the address according to any
|
||||
applicable mapping set by PacketAliasRedirectAddress(),
|
||||
or the default aliasing address set by
|
||||
PacketAliasSetAddress().
|
||||
|
||||
Incoming fragments are handled in one of two ways.
|
||||
If the header of a fragmented IP packet has already
|
||||
been seen, then all subsequent fragments will be
|
||||
re-mapped in the same manner the header fragment
|
||||
was. Fragments which arrive before the header
|
||||
are saved and then retrieved once the header fragment
|
||||
has been resolved.
|
||||
.Ss 5.1 PacketAliasSaveFragment()
|
||||
|
||||
.Ft int
|
||||
.Fn PacketAliasSaveFragment "char *ptr"
|
||||
|
||||
When PacketAliasIn() returns
|
||||
PKT_ALIAS_UNRESOLVED_FRAGMENT, this
|
||||
function can be used to save the pointer to
|
||||
the unresolved fragment.
|
||||
|
||||
It is implicitly assumed that
|
||||
.Em ptr
|
||||
points to a block of memory allocated by
|
||||
malloc(). If the fragment is never
|
||||
resolved, the packet aliasing engine will
|
||||
automatically free the memory after a
|
||||
timeout period. [Eventually this function
|
||||
should be modified so that a callback
|
||||
function for freeing memory is passed as
|
||||
an argument.]
|
||||
|
||||
This function returns PKT_ALIAS_OK if it
|
||||
was successful and PKT_ALIAS_ERROR if there
|
||||
was an error.
|
||||
.Ss 5.2 PacketAliasGetNextFragment()
|
||||
|
||||
.Ft char *
|
||||
.Fn PacketAliasGetFragment "char *buffer"
|
||||
|
||||
This function can be used to retrieve fragment
|
||||
pointers saved by PacketAliasSaveFragment().
|
||||
The IP header fragment pointed to by
|
||||
Em buffer
|
||||
is the header fragment indicated when
|
||||
PacketAliasIn() returns PKT_ALIAS_FOUND_HEADER_FRAGMENT.
|
||||
Once a a fragment pointer is retrieved, it
|
||||
becomes the calling program's responsibility
|
||||
to free the dynamically allocated memory for
|
||||
the fragment.
|
||||
|
||||
PacketAliasGetFragment() can be called
|
||||
sequentially until there are no more fragments
|
||||
available, at which time it returns NULL.
|
||||
.Ss 5.3 PacketAliasFragmentIn()
|
||||
|
||||
.Ft void
|
||||
.Fn PacketAliasFragmentIn "char *header" "char *fragment"
|
||||
|
||||
When a fragment is retrieved with
|
||||
PacketAliasGetFragment(), it can then be
|
||||
de-aliased with a call to PacketAliasFragmentIn().
|
||||
.Em header
|
||||
is the pointer to a header fragment used as a
|
||||
template, and
|
||||
.Em fragment
|
||||
is the pointer to the packet to be de-aliased.
|
||||
|
||||
.Sh 6. Miscellaneous Functions
|
||||
|
||||
.Ss 6.1 PacketAliasSetTarget()
|
||||
|
||||
.Ft void
|
||||
.Fn PacketAliasSetTarget "struct in_addr addr"
|
||||
|
||||
When an incoming packet not associated with
|
||||
any pre-existing aliasing link arrives at the
|
||||
host machine, it will be sent to the address
|
||||
indicated by a call to PacketAliasSetTarget().
|
||||
|
||||
If this function is not called, or is called
|
||||
with a zero address argument, then all new
|
||||
incoming packets go to the address set by
|
||||
PacketAliasSetAddress.
|
||||
.Ss 6.2 PacketAliasCheckNewLink()
|
||||
|
||||
.Ft int
|
||||
.Fn PacketAliasCheckNewLink "void"
|
||||
|
||||
This function returns a non-zero value when
|
||||
a new aliasing link is created. In circumstances
|
||||
where incoming traffic is being sequentially
|
||||
sent to different local servers, this function
|
||||
can be used to trigger when PacketAliasSetTarget()
|
||||
is called to change the default target address.
|
||||
.Ss 6.3 PacketAliasInternetChecksum()
|
||||
|
||||
.Ft u_short
|
||||
.Fn PacketAliasInternetChecksum "char *buffer" "int nbytes"
|
||||
|
||||
This is a utility function that does not seem
|
||||
to be available elswhere and is included as a
|
||||
convenience. It computes the internet checksum,
|
||||
which is used in both IP and protocol-specific
|
||||
headers (TCP, UDP, ICMP).
|
||||
|
||||
.Em buffer
|
||||
points to the data block to be checksummed, and
|
||||
.Em nbytes
|
||||
is the number of bytes. The 16-bit checksum
|
||||
field should be zeroed before computing the checksum.
|
||||
|
||||
Checksums can also be verified by operating on a block
|
||||
of data including its checksum. If the checksum is
|
||||
valid, PacketAliasInternetChecksum() will return zero.
|
||||
|
||||
.Sh 7. Authors
|
||||
Charles Mott (cmott@srv.net), versions 1.0 - 1.8, 2.0 - 2.2.
|
||||
|
||||
Eivind Eiklund (eivind@freebsd.org), versions 1.8b and 1.9.
|
||||
Added IRC support as well as contributing a number of
|
||||
architectural improvements.
|
||||
|
||||
.Sh 8. Acknowledgments
|
||||
|
||||
Listed below, in approximate chronological
|
||||
order, are individuals who have provided
|
||||
valuable comments and/or debugging assistance.
|
||||
|
||||
.Bl -inset -compact -offset left
|
||||
.It Gary Roberts
|
||||
.It Tom Torrance
|
||||
.It Reto Burkhalter
|
||||
.It Martin Renters
|
||||
.It Brian Somers
|
||||
.It Paul Traina
|
||||
.It Ari Suutari
|
||||
.It Dave Remien
|
||||
.It J. Fortes
|
||||
.It Andrzej Bialeki
|
||||
.El
|
||||
|
||||
.Sh Appendix: Conceptual Background
|
||||
This appendix is intended for those who
|
||||
are planning to modify the source code or want
|
||||
to create somewhat esoteric applications using
|
||||
the packet aliasing functions.
|
||||
|
||||
The conceptual framework under which the
|
||||
packet aliasing engine operates is described here.
|
||||
Central to the discussion is the idea of an
|
||||
"aliasing link" which describes the relationship
|
||||
for a given packet transaction between the local
|
||||
machine, aliased identity and remote machine. It
|
||||
is discussed how such links come into existence
|
||||
and are destroyed.
|
||||
.Ss A.1 Aliasing Links
|
||||
There is a notion of an "aliasing link",
|
||||
which is 7-tuple describing a specific
|
||||
translation:
|
||||
.Bd -literal -offset indent
|
||||
(local addr, local port, alias addr, alias port,
|
||||
remote addr, remote port, protocol)
|
||||
.Ed
|
||||
|
||||
Outgoing packets have the local address and
|
||||
port number replaced with the alias address
|
||||
and port number. Incoming packets undergo the
|
||||
reverse process. The packet aliasing engine
|
||||
attempts to match packets against an internal
|
||||
table of aliasing links to determine how to
|
||||
modify a given IP packet. Both the IP
|
||||
header and protocol dependent headers are
|
||||
modified as necessary. Aliasing links are
|
||||
created and deleted as necessary according
|
||||
to network traffic.
|
||||
|
||||
Protocols can be TCP, UDP or even ICMP in
|
||||
certain circumstances. (Some types of ICMP
|
||||
packets can be aliased according to sequence
|
||||
or id number which acts as an equivalent port
|
||||
number for identifying how individual packets
|
||||
should be handled.)
|
||||
|
||||
Each aliasing link must have a unique
|
||||
combination of the following five quanties:
|
||||
alias address/port, remote address/port
|
||||
and protocol. This ensures that several
|
||||
machines on a local network can share the
|
||||
same aliased IP address. In cases where
|
||||
conflicts might arise, the aliasing port
|
||||
is chosen so that uniqueness is maintained.
|
||||
.Ss A.2 Static and Dynamic Links
|
||||
Aliasing links can either be static or dynamic.
|
||||
Static links persist indefinitely and represent
|
||||
fixed rules for translating IP packets. Dynamic
|
||||
links come into existence for a specific TCP
|
||||
connection or UDP transaction or ICMP echo
|
||||
sequence. For the case of TCP, the connection
|
||||
can be monitored to see when the associated
|
||||
aliasing link should be deleted. Aliasing links
|
||||
for UDP transactions (and ICMP echo and timestamp
|
||||
equests) work on a simple timeout rule. When
|
||||
no activity is observed on a dynamic link for
|
||||
a certain amount of time it is automatically
|
||||
deleted. Timeout rules also apply to TCP
|
||||
connections which do not open or close
|
||||
properly.
|
||||
.Ss A.3 Partially Specified Aliasing Links
|
||||
Aliasing links can be partially specified,
|
||||
meaning that the remote address and/or remote
|
||||
ports are unkown. In this case, when a packet
|
||||
matching the incomplete specification is found,
|
||||
a fully specified dynamic link is created. If
|
||||
the original partially specified link is dynamic,
|
||||
it will be deleted after the fully specified link
|
||||
is created, otherwise it will persist.
|
||||
|
||||
For instance, a partially specified link might
|
||||
be
|
||||
.Bd -literal -offset indent
|
||||
(192.168.0.4, 23, 204.228.203.215, 8066, 0, 0, tcp)
|
||||
.Ed
|
||||
|
||||
The zeros denote unspecified components for
|
||||
the remote address and port. If this link were
|
||||
static it would have the effect of redirecting
|
||||
all incoming traffic from port 8066 of
|
||||
204.228.203.215 to port 23 (telnet) of machine
|
||||
192.168.0.4 on the local network. Each
|
||||
individual telnet connection would initiate
|
||||
the creation of a distinct dynamic link.
|
||||
.Ss A.4 Dynamic Link Creation
|
||||
In addition to aliasing links, there are
|
||||
also address mappings that can be stored
|
||||
within the internal data table of the packet
|
||||
aliasing mechanism.
|
||||
.Bd -literal -offset indent
|
||||
(local addr, alias addr)
|
||||
.Ed
|
||||
|
||||
Address mappings are searched when creating
|
||||
new dynamic links.
|
||||
|
||||
All outgoing packets from the local network
|
||||
automatically create a dynamic link if
|
||||
they do not match an already existing fully
|
||||
specified link. If an address mapping exists
|
||||
for the the outgoing packet, this determines
|
||||
the alias address to be used. If no mapping
|
||||
exists, then a default address, usually the
|
||||
address of the packet aliasing host, is used.
|
||||
If necessary, this default address can be
|
||||
changed as often as each indvidual packet
|
||||
arrives.
|
||||
|
||||
The aliasing port number is determined
|
||||
such that the new dynamic link does not
|
||||
conflict with any existing links. In the
|
||||
default operating mode, the packet aliasing
|
||||
engine attempts to set the aliasing port
|
||||
equal to the local port number. If this
|
||||
results in a conflict, then port numbers
|
||||
are randomly chosen until a unique aliasing
|
||||
link can be established. In an alternate
|
||||
operating mode, the first choice of an
|
||||
aliasing port is also random and unrelated
|
||||
to the local port number.
|
||||
|
||||
105
sys/netinet/libalias/HISTORY
Normal file
105
sys/netinet/libalias/HISTORY
Normal file
@ -0,0 +1,105 @@
|
||||
Version 1.0: August 11, 1996 (cjm)
|
||||
|
||||
Version 1.1: August 20, 1996 (cjm)
|
||||
- Host accepts incoming connections for ports 0 to 1023.
|
||||
|
||||
Version 1.2: September 7, 1996 (cjm)
|
||||
- Fragment handling error in alias_db.c corrected.
|
||||
|
||||
Version 1.3: September 15, 1996 (cjm)
|
||||
- Generalized mechanism for handling incoming
|
||||
connections (no more 0 to 1023 restriction).
|
||||
|
||||
- Increased ICMP support (will handle traceroute now).
|
||||
|
||||
- Improved TCP close connection logic.
|
||||
|
||||
Version 1.4: September 16, 1996 (cjm)
|
||||
|
||||
Version 1.5: September 17, 1996 (cjm)
|
||||
- Corrected error in handling incoming UDP packets
|
||||
with zero checksum.
|
||||
|
||||
Version 1.6: September 18, 1996
|
||||
- Simplified ICMP data storage. Will now handle
|
||||
tracert from Win95 and NT as well as FreeBSD
|
||||
traceroute, which uses UDP packets to non-existent
|
||||
ports.
|
||||
|
||||
Verstion 1.7: January 9, 1997 (cjm)
|
||||
- Reduced malloc() activity for ICMP echo and
|
||||
timestamp requests.
|
||||
|
||||
- Added handling for out-of-order IP fragments.
|
||||
|
||||
- Switched to differential checksum computation
|
||||
for IP headers (TCP, UDP and ICMP checksums
|
||||
were already differential).
|
||||
|
||||
- Accepts FTP data connections from other than
|
||||
port 20. This allows one ftp connections
|
||||
from two hosts which are both running packet
|
||||
aliasing.
|
||||
|
||||
Version 1.8: January 14, 1997 (cjm)
|
||||
- Fixed data type error in function StartPoint()
|
||||
in alias_db.c (this bug did not exist before v1.7)
|
||||
|
||||
Version 1.9: February 1, 1997 (Eivind Eklund <perhaps@yes.no>)
|
||||
- Added support for IRC DCC (ee)
|
||||
|
||||
- Changed the aliasing routines to use ANSI style
|
||||
throughout (ee)
|
||||
|
||||
- Minor API changes for integration with other
|
||||
programs than PPP (ee)
|
||||
|
||||
- Fixed minor security hole in alias_ftp.c for
|
||||
other applications of the aliasing software.
|
||||
Hole could _not_ manifest in ppp+pktAlias, but
|
||||
could potentially manifest in other applications
|
||||
of the aliasing. (ee)
|
||||
|
||||
- Connections initiated from packet aliasing
|
||||
host machine will not have their port number
|
||||
aliased unless it conflicts with an aliasing
|
||||
port already being used. (There is an option
|
||||
to disable this for debugging) (cjm)
|
||||
|
||||
- Sockets will be allocated in cases where
|
||||
there might be port interference with the
|
||||
host machine. This can be disabled in cases
|
||||
where the ppp host will be acting purely as a
|
||||
masquerading router and not generate any
|
||||
traffic of its own.
|
||||
(cjm)
|
||||
|
||||
Version 2.0: March, 1997 (cjm)
|
||||
- Aliasing links are cleared only when a host interface address
|
||||
changes.
|
||||
|
||||
- PacketAliasPermanentLink() API added.
|
||||
|
||||
- Option for only aliasing private, unregistered
|
||||
IP addresses added.
|
||||
|
||||
- Substantial rework to the aliasing lookup engine.
|
||||
|
||||
Version 2.1: May, 1997 (cjm)
|
||||
- Continuing rework to the aliasing lookup engine
|
||||
to support multiple incoming addresses and static
|
||||
NAT. PacketAliasRedirectPort() and
|
||||
PacketAliasRedirectAddr() added to API.
|
||||
|
||||
- Now supports outgoing as well as incoming ICMP
|
||||
error messges.
|
||||
|
||||
Version 2.2: July, 1997 (cjm)
|
||||
- Rationalized API function names to all begin with
|
||||
"PacketAlias..." Old function names are retained
|
||||
for backwards compatitibility.
|
||||
|
||||
- Packet aliasing engine will now free memory of
|
||||
fragments which are never resolved after a timeout
|
||||
period. Once a fragment is resolved, it becomes
|
||||
the users responsibility to free the memory.
|
||||
@ -1,8 +1,9 @@
|
||||
LIB= alias
|
||||
SHLIB_MAJOR= 2
|
||||
SHLIB_MINOR= 1
|
||||
SHLIB_MINOR= 2
|
||||
CFLAGS+=-Wall -I${.CURDIR}
|
||||
SRCS= alias.c alias_db.c alias_ftp.c alias_irc.c alias_util.c
|
||||
SRCS= alias.c alias_db.c alias_ftp.c alias_irc.c alias_util.c alias_old.c
|
||||
MAN3=libalias.3
|
||||
|
||||
beforeinstall:
|
||||
${INSTALL} -C -o ${BINOWN} -g ${BINGRP} -m 444 ${.CURDIR}/alias.h \
|
||||
|
||||
@ -66,6 +66,13 @@
|
||||
and PacketAliasOut2() for dynamic address
|
||||
control (e.g. round-robin allocation of
|
||||
incoming packets).
|
||||
|
||||
Version 2.2 July 1997 (cjm)
|
||||
- Rationalized API function names to begin
|
||||
with "PacketAlias..."
|
||||
- Eliminated PacketAliasIn2() and
|
||||
PacketAliasOut2() as poorly conceived.
|
||||
|
||||
*/
|
||||
|
||||
#include <stdio.h>
|
||||
@ -884,20 +891,18 @@ FragmentOut(struct ip *pip)
|
||||
|
||||
/* Outside World Access
|
||||
|
||||
SaveFragmentPtr()
|
||||
GetNextFragmentPtr()
|
||||
FragmentAliasIn()
|
||||
PacketAliasSaveFragment()
|
||||
PacketAliasGetFragment()
|
||||
PacketAliasFragmentIn()
|
||||
PacketAliasIn()
|
||||
PacketAliasOut()
|
||||
PacketAliasIn2()
|
||||
PacketAliasOut2()
|
||||
|
||||
(prototypes in alias.h)
|
||||
*/
|
||||
|
||||
|
||||
int
|
||||
SaveFragmentPtr(char *ptr)
|
||||
PacketAliasSaveFragment(char *ptr)
|
||||
{
|
||||
int iresult;
|
||||
struct alias_link *link;
|
||||
@ -916,7 +921,7 @@ SaveFragmentPtr(char *ptr)
|
||||
|
||||
|
||||
char *
|
||||
GetNextFragmentPtr(char *ptr)
|
||||
PacketAliasGetFragment(char *ptr)
|
||||
{
|
||||
struct alias_link *link;
|
||||
char *fptr;
|
||||
@ -927,6 +932,7 @@ GetNextFragmentPtr(char *ptr)
|
||||
if (link != NULL)
|
||||
{
|
||||
GetFragmentPtr(link, &fptr);
|
||||
SetFragmentPtr(link, NULL);
|
||||
SetExpire(link, 0); /* Deletes link */
|
||||
|
||||
return(fptr);
|
||||
@ -939,11 +945,11 @@ GetNextFragmentPtr(char *ptr)
|
||||
|
||||
|
||||
void
|
||||
FragmentAliasIn(char *ptr, /* Points to correctly de-aliased
|
||||
header fragment */
|
||||
char *ptr_fragment /* Points to fragment which must
|
||||
be de-aliased */
|
||||
)
|
||||
PacketAliasFragmentIn(char *ptr, /* Points to correctly de-aliased
|
||||
header fragment */
|
||||
char *ptr_fragment /* Points to fragment which must
|
||||
be de-aliased */
|
||||
)
|
||||
{
|
||||
struct ip *pip;
|
||||
struct ip *fpip;
|
||||
@ -967,6 +973,7 @@ PacketAliasIn(char *ptr, int maxpacketsize)
|
||||
int iresult;
|
||||
|
||||
HouseKeeping();
|
||||
ClearCheckNewLink();
|
||||
pip = (struct ip *) ptr;
|
||||
alias_addr = pip->ip_dst;
|
||||
|
||||
@ -1039,6 +1046,7 @@ PacketAliasOut(char *ptr, /* valid IP packet */
|
||||
struct ip *pip;
|
||||
|
||||
HouseKeeping();
|
||||
ClearCheckNewLink();
|
||||
pip = (struct ip *) ptr;
|
||||
|
||||
addr_save = GetDefaultAliasAddress();
|
||||
@ -1056,7 +1064,7 @@ PacketAliasOut(char *ptr, /* valid IP packet */
|
||||
else if (addr >= UNREG_ADDR_A_LOWER && addr <= UNREG_ADDR_A_UPPER)
|
||||
iclass = 1;
|
||||
|
||||
if (iclass == 0)
|
||||
if (iclass != 0)
|
||||
{
|
||||
SetDefaultAliasAddress(pip->ip_src);
|
||||
}
|
||||
@ -1086,57 +1094,3 @@ PacketAliasOut(char *ptr, /* valid IP packet */
|
||||
SetDefaultAliasAddress(addr_save);
|
||||
return(iresult);
|
||||
}
|
||||
|
||||
|
||||
int
|
||||
PacketAliasIn2(char *ptr, /* valid IP packet */
|
||||
struct in_addr addr, /* Default aliasing address */
|
||||
int maxpacketsize /* How much the packet data may grow
|
||||
(FTP and IRC inline changes) */
|
||||
)
|
||||
{
|
||||
int result_code;
|
||||
struct in_addr addr_save;
|
||||
|
||||
ClearNewDefaultLink();
|
||||
addr_save = GetDefaultAliasAddress();
|
||||
|
||||
SetDefaultTargetAddress(addr);
|
||||
result_code = PacketAliasIn(ptr, maxpacketsize);
|
||||
ClearDefaultTargetAddress();
|
||||
|
||||
if (result_code == PKT_ALIAS_OK)
|
||||
{
|
||||
if (CheckNewDefaultLink())
|
||||
return PKT_ALIAS_NEW_LINK;
|
||||
}
|
||||
|
||||
return result_code;
|
||||
}
|
||||
|
||||
|
||||
int
|
||||
PacketAliasOut2(char *ptr, /* valid IP packet */
|
||||
struct in_addr addr, /* Default aliasing address */
|
||||
int maxpacketsize /* How much the packet data may grow
|
||||
(FTP and IRC inline changes) */
|
||||
)
|
||||
{
|
||||
int result_code;
|
||||
struct in_addr addr_save;
|
||||
|
||||
ClearNewDefaultLink();
|
||||
addr_save = GetDefaultAliasAddress();
|
||||
|
||||
SetDefaultAliasAddress(addr);
|
||||
result_code = PacketAliasOut(ptr, maxpacketsize);
|
||||
SetDefaultAliasAddress(addr_save);
|
||||
|
||||
if (result_code == PKT_ALIAS_OK)
|
||||
{
|
||||
if (CheckNewDefaultLink())
|
||||
return PKT_ALIAS_NEW_LINK;
|
||||
}
|
||||
|
||||
return result_code;
|
||||
}
|
||||
|
||||
@ -12,45 +12,82 @@
|
||||
#ifndef _ALIAS_H_
|
||||
#define _ALIAS_H_
|
||||
|
||||
/* Alias link representativei (incomplete struct) */
|
||||
#ifndef NULL
|
||||
#define NULL 0
|
||||
#endif
|
||||
|
||||
/* Alias link representative (incomplete struct) */
|
||||
struct alias_link;
|
||||
|
||||
/* External interfaces (API) to packet aliasing engine */
|
||||
|
||||
/* Initialization and Control */
|
||||
extern void
|
||||
PacketAliasInit(void);
|
||||
|
||||
extern void
|
||||
PacketAliasSetAddress(struct in_addr);
|
||||
|
||||
extern unsigned int
|
||||
PacketAliasSetMode(unsigned int, unsigned int);
|
||||
|
||||
/* Packet Handling */
|
||||
extern int
|
||||
PacketAliasIn(char *, int maxpacketsize);
|
||||
|
||||
extern int
|
||||
PacketAliasOut(char *, int maxpacketsize);
|
||||
|
||||
/* Port and Address Redirection */
|
||||
extern struct alias_link *
|
||||
PacketAliasRedirectPort(struct in_addr, u_short,
|
||||
struct in_addr, u_short,
|
||||
struct in_addr, u_short,
|
||||
u_char);
|
||||
|
||||
extern struct alias_link *
|
||||
PacketAliasRedirectAddr(struct in_addr,
|
||||
struct in_addr);
|
||||
|
||||
extern void
|
||||
PacketAliasRedirectDelete(struct alias_link *);
|
||||
|
||||
/* Fragment Handling */
|
||||
extern int
|
||||
PacketAliasSaveFragment(char *);
|
||||
|
||||
extern char *
|
||||
PacketAliasGetFragment(char *);
|
||||
|
||||
extern void
|
||||
PacketAliasFragmentIn(char *, char *);
|
||||
|
||||
/* Miscellaneous Functions */
|
||||
extern u_short
|
||||
PacketAliasInternetChecksum(u_short *, int);
|
||||
|
||||
|
||||
/*
|
||||
In version 2.2, the function names were rationalized
|
||||
to all be of the form PacketAlias... These are the
|
||||
old function names for backwards compatibility
|
||||
*/
|
||||
extern int SaveFragmentPtr(char *);
|
||||
extern char *GetNextFragmentPtr(char *);
|
||||
extern void FragmentAliasIn(char *, char *);
|
||||
extern int PacketAliasIn(char *, int maxpacketsize);
|
||||
extern int PacketAliasOut(char *, int maxpacketsize);
|
||||
extern int PacketAliasIn2(char *, struct in_addr, int maxpacketsize);
|
||||
extern int PacketAliasOut2(char *, struct in_addr, int maxpacketsize);
|
||||
extern void SetPacketAliasAddress(struct in_addr);
|
||||
extern void InitPacketAlias(void);
|
||||
extern void InitPacketAliasLog(void);
|
||||
extern void UninitPacketAliasLog(void);
|
||||
extern unsigned int SetPacketAliasMode(unsigned int, unsigned int);
|
||||
extern struct alias_link *
|
||||
PacketAliasRedirectPort(struct in_addr, u_short,
|
||||
struct in_addr, u_short,
|
||||
struct in_addr, u_short,
|
||||
u_char);
|
||||
extern int PacketAliasIn2(char *, struct in_addr, int maxpacketsize);
|
||||
extern int PacketAliasOut2(char *, struct in_addr, int maxpacketsize);
|
||||
extern int
|
||||
PacketAliasPermanentLink(struct in_addr, u_short,
|
||||
struct in_addr, u_short,
|
||||
u_short, u_char);
|
||||
extern struct alias_link *
|
||||
PacketAliasRedirectAddr(struct in_addr,
|
||||
struct in_addr);
|
||||
void PacketAliasRedirectDelete(struct alias_link *);
|
||||
|
||||
|
||||
/* InternetChecksum() is not specifically part of the
|
||||
packet aliasing API, but is sometimes needed outside
|
||||
the module. (~for instance, natd uses it to create
|
||||
an ICMP error message when interface size is
|
||||
exceeded.) */
|
||||
|
||||
extern u_short InternetChecksum(u_short *, int);
|
||||
|
||||
/* Obsolete constant */
|
||||
#define PKT_ALIAS_NEW_LINK 5
|
||||
|
||||
/********************** Mode flags ********************/
|
||||
/* Set these flags using SetPacketAliasMode() */
|
||||
@ -58,25 +95,28 @@ extern u_short InternetChecksum(u_short *, int);
|
||||
/* If PKT_ALIAS_LOG is set, a message will be printed to
|
||||
/var/log/alias.log every time a link is created or deleted. This
|
||||
is useful for debugging */
|
||||
#define PKT_ALIAS_LOG 1
|
||||
#define PKT_ALIAS_LOG 0x01
|
||||
|
||||
/* If PKT_ALIAS_DENY_INCOMING is set, then incoming connections (e.g.
|
||||
to ftp, telnet or web servers will be prevented by the aliasing
|
||||
mechanism. */
|
||||
#define PKT_ALIAS_DENY_INCOMING 2
|
||||
#define PKT_ALIAS_DENY_INCOMING 0x02
|
||||
|
||||
/* If PKT_ALIAS_SAME_PORTS is set, packets will be attempted sent from
|
||||
the same port as they originated on. This allow eg rsh to work
|
||||
the same port as they originated on. This allows eg rsh to work
|
||||
*99% of the time*, but _not_ 100%. (It will be slightly flakey
|
||||
instead of not working at all.) */
|
||||
#define PKT_ALIAS_SAME_PORTS 4
|
||||
instead of not working at all.) This mode bit is set by
|
||||
PacketAliasInit(), so it is a default mode of operation. */
|
||||
#define PKT_ALIAS_SAME_PORTS 0x04
|
||||
|
||||
/* If PKT_ALIAS_USE_SOCKETS is set, then when partially specified
|
||||
links (e.g. destination port and/or address is zero), the packet
|
||||
aliasing engine will attempt to allocate a socket for the aliasing
|
||||
port it chooses. This will avoid interference with the host
|
||||
machine. Fully specified links do not require this. */
|
||||
#define PKT_ALIAS_USE_SOCKETS 8
|
||||
machine. Fully specified links do not require this. This bit
|
||||
is set after a call to PacketAliasInit(), so it is a default
|
||||
mode of operation.*/
|
||||
#define PKT_ALIAS_USE_SOCKETS 0x08
|
||||
|
||||
/* If PKT_ALIAS_UNREGISTERED_ONLY is set, then only packets with with
|
||||
unregistered source addresses will be aliased (along with those
|
||||
@ -86,9 +126,15 @@ extern u_short InternetChecksum(u_short *, int);
|
||||
10.0.0.0 -> 10.255.255.255
|
||||
172.16.0.0 -> 172.31.255.255
|
||||
192.168.0.0 -> 192.168.255.255 */
|
||||
#define PKT_ALIAS_UNREGISTERED_ONLY 16
|
||||
|
||||
#define PKT_ALIAS_UNREGISTERED_ONLY 0x10
|
||||
|
||||
/* If PKT_ALIAS_RESET_ON_ADDR_CHANGE is set, then the table of dynamic
|
||||
aliasing links will be reset whenever PacketAliasSetAddress()
|
||||
changes the default aliasing address. If the default aliasing
|
||||
address is left unchanged by this functions call, then the
|
||||
table of dynamic aliasing links will be left intact. This
|
||||
bit is set after a call to PacketAliasInit(). */
|
||||
#define PKT_ALIAS_RESET_ON_ADDR_CHANGE 0x20
|
||||
|
||||
/* Return Codes */
|
||||
#define PKT_ALIAS_ERROR -1
|
||||
@ -96,7 +142,6 @@ extern u_short InternetChecksum(u_short *, int);
|
||||
#define PKT_ALIAS_IGNORED 2
|
||||
#define PKT_ALIAS_UNRESOLVED_FRAGMENT 3
|
||||
#define PKT_ALIAS_FOUND_HEADER_FRAGMENT 4
|
||||
#define PKT_ALIAS_NEW_LINK 5
|
||||
|
||||
#endif
|
||||
/*lint -restore */
|
||||
|
||||
@ -249,8 +249,8 @@ struct alias_link /* Main data structure */
|
||||
|
||||
union /* Auxiliary data */
|
||||
{
|
||||
struct in_addr frag_addr;
|
||||
char *frag_ptr;
|
||||
struct in_addr frag_addr;
|
||||
struct tcp_dat *tcp;
|
||||
} data;
|
||||
};
|
||||
@ -755,6 +755,8 @@ DeleteLink(struct alias_link *link)
|
||||
break;
|
||||
case LINK_FRAGMENT_PTR:
|
||||
fragmentPtrLinkCount--;
|
||||
if (link->data.frag_ptr != NULL)
|
||||
free(link->data.frag_ptr);
|
||||
break;
|
||||
}
|
||||
|
||||
@ -1351,8 +1353,6 @@ FindAliasAddress(struct in_addr original_addr)
|
||||
GetOriginalPort(), GetAliasPort()
|
||||
SetAckModified(), GetAckModified()
|
||||
GetDeltaAckIn(), GetDeltaSeqOut(), AddSeq()
|
||||
ClearNewLink()
|
||||
CheckNewLink()
|
||||
*/
|
||||
|
||||
|
||||
@ -1457,19 +1457,6 @@ SetDefaultAliasAddress(struct in_addr alias_addr)
|
||||
}
|
||||
|
||||
|
||||
void
|
||||
SetDefaultTargetAddress(struct in_addr target_addr)
|
||||
{
|
||||
targetAddress = target_addr;
|
||||
}
|
||||
|
||||
|
||||
void ClearDefaultTargetAddress(void)
|
||||
{
|
||||
targetAddress.s_addr = 0;
|
||||
}
|
||||
|
||||
|
||||
u_short
|
||||
GetOriginalPort(struct alias_link *link)
|
||||
{
|
||||
@ -1661,19 +1648,18 @@ SetExpire(struct alias_link *link, int expire)
|
||||
}
|
||||
|
||||
void
|
||||
ClearNewDefaultLink(void)
|
||||
ClearCheckNewLink(void)
|
||||
{
|
||||
newDefaultLink = 0;
|
||||
}
|
||||
|
||||
|
||||
int
|
||||
CheckNewDefaultLink(void)
|
||||
{
|
||||
return newDefaultLink;
|
||||
}
|
||||
|
||||
/* Miscellaneous Functions
|
||||
|
||||
HouseKeeping()
|
||||
InitPacketAliasLog()
|
||||
UninitPacketAliasLog()
|
||||
*/
|
||||
|
||||
/*
|
||||
Whenever an outgoing or incoming packet is handled, HouseKeeping()
|
||||
@ -1734,6 +1720,31 @@ HouseKeeping(void)
|
||||
}
|
||||
|
||||
|
||||
/* Init the log file and enable logging */
|
||||
void
|
||||
InitPacketAliasLog(void)
|
||||
{
|
||||
if ((~packetAliasMode & PKT_ALIAS_LOG)
|
||||
&& (monitorFile = fopen("/var/log/alias.log", "w")))
|
||||
{
|
||||
packetAliasMode |= PKT_ALIAS_LOG;
|
||||
fprintf(monitorFile,
|
||||
"PacketAlias/InitPacketAliasLog: Packet alias logging enabled.\n");
|
||||
}
|
||||
}
|
||||
|
||||
|
||||
/* Close the log-file and disable logging. */
|
||||
void
|
||||
UninitPacketAliasLog(void)
|
||||
{
|
||||
if( monitorFile )
|
||||
fclose(monitorFile);
|
||||
packetAliasMode &= ~PKT_ALIAS_LOG;
|
||||
}
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
|
||||
@ -1743,11 +1754,10 @@ HouseKeeping(void)
|
||||
|
||||
PacketAliasRedirectPort()
|
||||
PacketAliasRedirectAddr()
|
||||
SetPacketAliasAddress()
|
||||
InitPacketAliasLog()
|
||||
UninitPacketAliasLog()
|
||||
InitPacketAlias()
|
||||
SetPacketAliasMode()
|
||||
PacketAliasRedirectDelete()
|
||||
PacketAliasSetAddress()
|
||||
PacketAliasInit()
|
||||
PacketAliasSetMode()
|
||||
|
||||
(prototypes in alias.h)
|
||||
*/
|
||||
@ -1795,28 +1805,6 @@ PacketAliasRedirectPort(struct in_addr src_addr, u_short src_port,
|
||||
}
|
||||
|
||||
|
||||
/* This function is slightly less generalized than
|
||||
PacketAliasRedirectPort and is included for backwards
|
||||
compatibility */
|
||||
int
|
||||
PacketAliasPermanentLink(struct in_addr src_addr, u_short src_port,
|
||||
struct in_addr dst_addr, u_short dst_port,
|
||||
u_short alias_port, u_char proto)
|
||||
{
|
||||
struct alias_link *link;
|
||||
|
||||
link = PacketAliasRedirectPort(src_addr, src_port,
|
||||
dst_addr, dst_port,
|
||||
nullAddress, alias_port,
|
||||
proto);
|
||||
|
||||
if (link == NULL)
|
||||
return -1;
|
||||
else
|
||||
return 0;
|
||||
}
|
||||
|
||||
|
||||
/* Static address translation */
|
||||
struct alias_link *
|
||||
PacketAliasRedirectAddr(struct in_addr src_addr,
|
||||
@ -1845,7 +1833,7 @@ PacketAliasRedirectAddr(struct in_addr src_addr,
|
||||
void
|
||||
PacketAliasRedirectDelete(struct alias_link *link)
|
||||
{
|
||||
/* This is a very dangerous function to put in the API,
|
||||
/* This is a dangerous function to put in the API,
|
||||
because an invalid pointer can crash the program. */
|
||||
|
||||
deleteAllLinks = 1;
|
||||
@ -1855,9 +1843,10 @@ PacketAliasRedirectDelete(struct alias_link *link)
|
||||
|
||||
|
||||
void
|
||||
SetPacketAliasAddress(struct in_addr addr)
|
||||
PacketAliasSetAddress(struct in_addr addr)
|
||||
{
|
||||
if (aliasAddress.s_addr != addr.s_addr)
|
||||
if (packetAliasMode & PKT_ALIAS_RESET_ON_ADDR_CHANGE
|
||||
&& aliasAddress.s_addr != addr.s_addr)
|
||||
{
|
||||
CleanupAliasData();
|
||||
aliasAddress = addr;
|
||||
@ -1865,32 +1854,15 @@ SetPacketAliasAddress(struct in_addr addr)
|
||||
}
|
||||
|
||||
|
||||
/* Init the log file and enable logging */
|
||||
void
|
||||
InitPacketAliasLog(void)
|
||||
PacketAliasSetTarget(struct in_addr target_addr)
|
||||
{
|
||||
if ((~packetAliasMode & PKT_ALIAS_LOG)
|
||||
&& (monitorFile = fopen("/var/log/alias.log", "w")))
|
||||
{
|
||||
packetAliasMode |= PKT_ALIAS_LOG;
|
||||
fprintf(monitorFile,
|
||||
"PacketAlias/InitPacketAliasLog: Packet alias logging enabled.\n");
|
||||
}
|
||||
}
|
||||
|
||||
|
||||
/* Close the log-file and disable logging. */
|
||||
void
|
||||
UninitPacketAliasLog(void)
|
||||
{
|
||||
if( monitorFile )
|
||||
fclose(monitorFile);
|
||||
packetAliasMode &= ~PKT_ALIAS_LOG;
|
||||
targetAddress = target_addr;
|
||||
}
|
||||
|
||||
|
||||
void
|
||||
InitPacketAlias(void)
|
||||
PacketAliasInit(void)
|
||||
{
|
||||
int i;
|
||||
struct timeval tv;
|
||||
@ -1918,6 +1890,7 @@ InitPacketAlias(void)
|
||||
}
|
||||
|
||||
aliasAddress.s_addr = 0;
|
||||
targetAddress.s_addr = 0;
|
||||
|
||||
icmpLinkCount = 0;
|
||||
udpLinkCount = 0;
|
||||
@ -1929,19 +1902,14 @@ InitPacketAlias(void)
|
||||
cleanupIndex =0;
|
||||
|
||||
packetAliasMode = PKT_ALIAS_SAME_PORTS
|
||||
| PKT_ALIAS_USE_SOCKETS;
|
||||
|
||||
if (packetAliasMode & PKT_ALIAS_LOG)
|
||||
{
|
||||
InitPacketAliasLog();
|
||||
fprintf(monitorFile, "Packet aliasing initialized.\n");
|
||||
}
|
||||
| PKT_ALIAS_USE_SOCKETS
|
||||
| PKT_ALIAS_RESET_ON_ADDR_CHANGE;
|
||||
}
|
||||
|
||||
|
||||
/* Change mode for some operations */
|
||||
unsigned int
|
||||
SetPacketAliasMode
|
||||
PacketAliasSetMode
|
||||
(
|
||||
unsigned int flags, /* Which state to bring flags to */
|
||||
unsigned int mask /* Mask of which flags to affect (use 0 to do a
|
||||
@ -1964,9 +1932,8 @@ SetPacketAliasMode
|
||||
}
|
||||
|
||||
|
||||
/*
|
||||
Clear all packet aliasing links, but leave mode
|
||||
flags unchanged. Typically used when the interface
|
||||
address changes and all existing links become
|
||||
invalid.
|
||||
*/
|
||||
int
|
||||
PacketAliasCheckNewLink(void)
|
||||
{
|
||||
return newDefaultLink;
|
||||
}
|
||||
|
||||
@ -68,8 +68,6 @@ struct in_addr GetDestAddress(struct alias_link *);
|
||||
struct in_addr GetAliasAddress(struct alias_link *);
|
||||
struct in_addr GetDefaultAliasAddress(void);
|
||||
void SetDefaultAliasAddress(struct in_addr);
|
||||
void SetDefaultTargetAddress(struct in_addr);
|
||||
void ClearDefaultTargetAddress(void);
|
||||
u_short GetOriginalPort(struct alias_link *);
|
||||
u_short GetAliasPort(struct alias_link *);
|
||||
void SetAckModified(struct alias_link *);
|
||||
@ -78,8 +76,7 @@ int GetDeltaAckIn(struct ip *, struct alias_link *);
|
||||
int GetDeltaSeqOut(struct ip *, struct alias_link *);
|
||||
void AddSeq(struct ip *, struct alias_link *, int);
|
||||
void SetExpire(struct alias_link *, int);
|
||||
void ClearNewDefaultLink(void);
|
||||
int CheckNewDefaultLink(void);
|
||||
void ClearCheckNewLink(void);
|
||||
|
||||
/* Housekeeping function */
|
||||
void HouseKeeping(void);
|
||||
@ -88,4 +85,9 @@ void HouseKeeping(void);
|
||||
/*lint -save -library Suppress flexelint warnings */
|
||||
void AliasHandleFtpOut(struct ip *, struct alias_link *, int);
|
||||
void AliasHandleIrcOut(struct ip *pip, struct alias_link *link, int maxsize );
|
||||
|
||||
/* Log file control */
|
||||
void InitPacketAliasLog(void);
|
||||
void UninitPacketAliasLog(void);
|
||||
|
||||
/*lint -restore */
|
||||
|
||||
77
sys/netinet/libalias/alias_old.c
Normal file
77
sys/netinet/libalias/alias_old.c
Normal file
@ -0,0 +1,77 @@
|
||||
/*
|
||||
This file can be considered a junk pile of old functions that
|
||||
are either obsolete or have had their names changed. In the
|
||||
transition from alias2.1 to alias2.2, all the function names
|
||||
were rationalized so that they began with "PacketAlias..."
|
||||
|
||||
These functions are included for backwards compatibility.
|
||||
*/
|
||||
|
||||
#include <sys/types.h>
|
||||
#include <netinet/in_systm.h>
|
||||
#include <netinet/in.h>
|
||||
#include <netinet/ip.h>
|
||||
#include "alias.h"
|
||||
#include "alias_local.h"
|
||||
|
||||
void
|
||||
InitPacketAlias(void)
|
||||
{
|
||||
PacketAliasInit();
|
||||
}
|
||||
|
||||
void
|
||||
SetPacketAliasAddress(struct in_addr addr)
|
||||
{
|
||||
PacketAliasSetAddress(addr);
|
||||
}
|
||||
|
||||
unsigned int
|
||||
SetPacketAliasMode(unsigned int flags, unsigned int mask)
|
||||
{
|
||||
return PacketAliasSetMode(flags, mask);
|
||||
}
|
||||
|
||||
int
|
||||
PacketAliasPermanentLink(struct in_addr src_addr, u_short src_port,
|
||||
struct in_addr dst_addr, u_short dst_port,
|
||||
u_short alias_port, u_char proto)
|
||||
{
|
||||
struct alias_link *link;
|
||||
struct in_addr null_address;
|
||||
|
||||
null_address.s_addr = 0;
|
||||
link = PacketAliasRedirectPort(src_addr, src_port,
|
||||
dst_addr, dst_port,
|
||||
null_address, alias_port,
|
||||
proto);
|
||||
|
||||
if (link == NULL)
|
||||
return -1;
|
||||
else
|
||||
return 0;
|
||||
}
|
||||
|
||||
int
|
||||
SaveFragmentPtr(char *ptr)
|
||||
{
|
||||
return PacketAliasSaveFragment(ptr);
|
||||
}
|
||||
|
||||
char *
|
||||
GetNextFragmentPtr(char *ptr)
|
||||
{
|
||||
return PacketAliasGetFragment(ptr);
|
||||
}
|
||||
|
||||
void
|
||||
FragmentAliasIn(char *header, char *fragment)
|
||||
{
|
||||
PacketAliasFragmentIn(header, fragment);
|
||||
}
|
||||
|
||||
u_short
|
||||
InternetChecksum(u_short *ptr, int len)
|
||||
{
|
||||
return PacketAliasInternetChecksum(ptr, len);
|
||||
}
|
||||
@ -26,10 +26,11 @@ purposes);
|
||||
#include <netinet/ip.h>
|
||||
#include <netinet/tcp.h>
|
||||
|
||||
#include "alias.h"
|
||||
#include "alias_local.h"
|
||||
|
||||
u_short
|
||||
InternetChecksum(u_short *ptr, int nbytes)
|
||||
PacketAliasInternetChecksum(u_short *ptr, int nbytes)
|
||||
{
|
||||
int sum, oddbyte;
|
||||
|
||||
@ -53,7 +54,8 @@ InternetChecksum(u_short *ptr, int nbytes)
|
||||
u_short
|
||||
IpChecksum(struct ip *pip)
|
||||
{
|
||||
return( InternetChecksum((u_short *) pip, (pip->ip_hl << 2)) );
|
||||
return( PacketAliasInternetChecksum((u_short *) pip,
|
||||
(pip->ip_hl << 2)) );
|
||||
|
||||
}
|
||||
|
||||
|
||||
722
sys/netinet/libalias/libalias.3
Normal file
722
sys/netinet/libalias/libalias.3
Normal file
@ -0,0 +1,722 @@
|
||||
.Dd July, 1997
|
||||
.Dt "libalias" 3
|
||||
.Os
|
||||
.Sh NAME
|
||||
.Nm "libalias"
|
||||
Packet Aliasing Library. A collection of
|
||||
functions for aliasing and de-aliasing
|
||||
of IP packets, intended for masquerading and
|
||||
network address translation (NAT).
|
||||
|
||||
.Sh SYNOPSIS
|
||||
.Fd #include <netinet/in.h>
|
||||
.Fd #include <alias.h>
|
||||
|
||||
Function prototypes are given in the main body
|
||||
of the text.
|
||||
|
||||
.Sh CONTENTS
|
||||
.Bd -literal -offset left
|
||||
1. Introduction
|
||||
2. Initialization and Control
|
||||
2.1 PacketAliasInit()
|
||||
2.2 PacketAliasSetAddress()
|
||||
2.3 PacketAliasSetMode()
|
||||
3. Packet Handling
|
||||
3.1 PacketAliasOut()
|
||||
3.2 PacketAliasIn()
|
||||
4. Port and Address Redirection
|
||||
4.1 PacketAliasRedirectPort()
|
||||
4.2 PacketAliasRedirectAddr()
|
||||
4.3 PacketAliasRedirectDelete()
|
||||
5. Fragment Handling
|
||||
5.1 PacketAliasSaveFragment()
|
||||
5.2 PacketAliasGetFragment()
|
||||
5.3 PacketAliasFragmentIn()
|
||||
6. Miscellaneous Functions
|
||||
6.1 PacketAliasSetTarget()
|
||||
6.2 PacketAliasCheckNewLink()
|
||||
6.3 PacketAliasInternetChecksum()
|
||||
7. Authors
|
||||
8. Acknowledgments
|
||||
|
||||
Appendix A: Conceptual Background
|
||||
A.1 Aliasing Links
|
||||
A.2 Static and Dynamic Links
|
||||
A.3 Partially Specified Links
|
||||
A.4 Dynamic Link Creation
|
||||
.Ed
|
||||
|
||||
.Sh 1. Introduction
|
||||
This library is a moderately portable
|
||||
set of functions designed to assist
|
||||
in the process of IP masquerading and
|
||||
network address translation. Outgoing
|
||||
packets from a local network with
|
||||
unregistered IP addresses can be aliased
|
||||
to appear as if they came from an
|
||||
accessible IP address. Incoming packets
|
||||
are then de-aliased so that they are sent
|
||||
to the correct machine on the local network.
|
||||
|
||||
A certain amount of flexibility is built
|
||||
into the packet aliasing engine. In
|
||||
the simplest mode of operation, a
|
||||
many-to-one address mapping takes place
|
||||
between local network and the packet
|
||||
aliasing host. This is known as IP
|
||||
masquerading. In addition, one-to-one
|
||||
mappings between local and public addresses
|
||||
can also be implemented, which is known as
|
||||
static NAT. In between these extremes,
|
||||
different groups of private addresses
|
||||
can be linked to different public addresses,
|
||||
comprising several distinct many-to-one
|
||||
mappings. Also, a given public address
|
||||
and port can be staticly redirected to
|
||||
a private address/port.
|
||||
|
||||
The packet aliasing engine was designed
|
||||
to operate in user space outside of the
|
||||
kernel, without any access to private
|
||||
kernel data structure, but the source code
|
||||
can also be ported to a kernel environment.
|
||||
|
||||
.Sh 2. Initialization and Control
|
||||
Two specific functions, PacketAliasInit()
|
||||
and PacketAliasSetAddress(), must always be
|
||||
called before any packet handling may be
|
||||
performed. In addition, the operating mode
|
||||
of the packet aliasing engine can be customized
|
||||
by calling PacketAliasSetMode().
|
||||
.Ss 2.1 PacketAliasInit()
|
||||
|
||||
.Ft void
|
||||
.Fn PacketAliasInit "void"
|
||||
|
||||
This function has no argument or return
|
||||
value and is used to initialize internal
|
||||
data structures. The following mode bits
|
||||
are always set after calling
|
||||
PacketAliasInit(). See section 2.3 for
|
||||
the meaning of these mode bits.
|
||||
.Bd -literal -offset indent
|
||||
PKT_ALIAS_USE_SAME_PORTS
|
||||
PKT_ALIAS_USE_SOCKETS
|
||||
PKT_ALIAS_RESET_ON_ADDR_CHANGE
|
||||
|
||||
.Ed
|
||||
This function will always return the packet
|
||||
aliasing engine to the same initial state.
|
||||
PacketAliasSetAddress() must be called afterwards,
|
||||
and any desired changes from the default mode
|
||||
bits listed above require a call to
|
||||
PacketAliasSetMode().
|
||||
|
||||
It is mandatory that this function be called
|
||||
at the beginning of a program prior to any
|
||||
packet handling.
|
||||
.Ss 2.2 PacketAliasSetAddress()
|
||||
|
||||
.Ft void
|
||||
.Fn PacketAliasSetAddress "struct in_addr addr"
|
||||
|
||||
This function sets the source address to which
|
||||
outgoing packets from the local area network
|
||||
are aliased. All outgoing packets are remapped
|
||||
to this address unless overridden by a static
|
||||
address mapping established by
|
||||
PacketAliasRedirectAddr().
|
||||
|
||||
If the PKT_ALIAS_RESET_ON_ADDR_CHANGE mode bit
|
||||
is set (the default mode of operation), then
|
||||
the internal aliasing link tables will be reset
|
||||
any time the aliasing address changes, as if
|
||||
PacketAliasReset() were called. This is useful
|
||||
for interfaces such as ppp where the IP
|
||||
address may or may not change on successive
|
||||
dial-up attempts.
|
||||
|
||||
If the PKT_ALIAS_RESET_ON_ADDR_CHANGE mode bit
|
||||
is set to zero, this function can also be used to
|
||||
dynamically change the aliasing address on a
|
||||
packet to packet basis (it is a low overhead
|
||||
call).
|
||||
|
||||
It is mandatory that this function be called
|
||||
prior to any packet handling.
|
||||
.Ss 2.3 PacketAliasSetMode()
|
||||
|
||||
.Ft void
|
||||
.Fn PacketAliasSetMode "int mode" "int mask"
|
||||
|
||||
This function sets or clears mode bits
|
||||
according to the value of
|
||||
.Em mode .
|
||||
Only bits marked in
|
||||
.Em mask
|
||||
are affected. The following mode bits are
|
||||
defined in alias.h:
|
||||
.Bl -hang -offset left
|
||||
.It PKT_ALIAS_LOG.
|
||||
Enables logging /var/log/alias.log. The log file
|
||||
shows total numbers of links (icmp, tcp, udp) each
|
||||
time an aliasing link is created or deleted. Mainly
|
||||
useful for debugging when the log file is viewed
|
||||
continuously with "tail -f".
|
||||
.It PKT_ALIAS_DENY_INCOMING.
|
||||
If this mode bit is set, all incoming packets
|
||||
associated with new TCP connections or new
|
||||
UDP transactions will be marked for being
|
||||
ignored (PacketAliasIn() return code
|
||||
PKT_ALIAS_IGNORED) by the calling program.
|
||||
Response packets to connections or transactions
|
||||
initiated from the packet aliasing host or
|
||||
local network will be unaffected. This mode
|
||||
bit is useful for implementing a one-way firewall.
|
||||
.It PKT_ALIAS_SAME_PORTS.
|
||||
If this mode bit is set, the packet aliasing
|
||||
engine will attempt to leave the alias port
|
||||
numbers unchanged from the actual local port
|
||||
number. This can be done as long as the
|
||||
quintuple (proto, alias addr, alias port,
|
||||
remote addr, remote port) is unique. If a
|
||||
conflict exists, an new aliasing port number is
|
||||
chosen even if this mode bit is set.
|
||||
.It PKT_ALIAS_USE_SOCKETS.
|
||||
This bit should be set when the the packet
|
||||
aliasing host originates network traffic as
|
||||
well as forwards it. When the packet aliasing
|
||||
host is waiting for a connection from an
|
||||
unknown host address or unknown port number
|
||||
(e.g. an FTP data connection), this mode bit
|
||||
specifies that a socket be allocated as a place
|
||||
holder to prevent port conflicts. Once a
|
||||
connection is extablished, usually within a
|
||||
minute or so, the socket is closed.
|
||||
.It PKT_ALIAS_UNREGISTERED_ONLY.
|
||||
If this mode bit is set, traffic on the
|
||||
local network which does not originate from
|
||||
unregistered address spaces will be ignored.
|
||||
Standard Class A, B and C unregistered addresses
|
||||
are:
|
||||
.Bd -literal -offset indent
|
||||
10.0.0.0 -> 10.255.255.255 (Class A subnet)
|
||||
172.16.0.0 -> 172.31.255.255 (Class B subnets)
|
||||
192.168.0.0 -> 192.168.255.255 (Class C subnets)
|
||||
|
||||
.Ed
|
||||
This option is useful in the case that
|
||||
packet aliasing host has both registered and
|
||||
unregistered subnets on different interfaces.
|
||||
The registered subnet is fully accessible to
|
||||
the outside world, so traffic from it doesn't
|
||||
need to be passed through the packet aliasing
|
||||
engine.
|
||||
.It PKT_ALIAS_RESET_ON_ADDR_CHANGE.
|
||||
When this mode bit is set and
|
||||
PacketAliasSetAddress() is called to change
|
||||
the aliasing address, the internal link table
|
||||
of the packet aliasing engine will be cleared.
|
||||
This operating mode is useful for ppp links
|
||||
where the interface address can sometimes
|
||||
change or remain the same between dial-ups.
|
||||
If this mode bit is not set, it the link table
|
||||
will never be reset in the event of an
|
||||
address change.
|
||||
.El
|
||||
.Sh 3. Packet Handling
|
||||
The packet handling functions are used to
|
||||
modify incoming (remote->local) and outgoing
|
||||
(local->remote) packets. The calling program
|
||||
is responsible for receiving and sending
|
||||
packets via network interfaces.
|
||||
|
||||
Along with PacketAliasInit() and PacketAliasSetAddress(),
|
||||
the two packet handling functions, PacketAliasIn()
|
||||
and PacketAliasOut(), comprise minimal set of functions
|
||||
needed for a basic IP masquerading implementation.
|
||||
.Ss 3.1 PacketAliasIn()
|
||||
|
||||
.Ft int
|
||||
.Fn PacketAliasIn "char *buffer" "int maxpacketsize"
|
||||
|
||||
An incoming packet coming from a remote machine to
|
||||
the local network is de-aliased by this function.
|
||||
The IP packet is pointed to by
|
||||
.Em buffer ,
|
||||
and
|
||||
.Em maxpacketsize
|
||||
indicates the size of the data structure containing
|
||||
the packet and should be at least as large as the
|
||||
actual packet size.
|
||||
|
||||
Return codes:
|
||||
.Bl -hang -offset left
|
||||
.It PKT_ALIAS_ERROR.
|
||||
An internal error within the packet aliasing
|
||||
engine occured.
|
||||
.It PKT_ALIAS_OK.
|
||||
The packet aliasing process was successful.
|
||||
.It PKT_ALIAS_IGNORED.
|
||||
The packet was ignored and not de-aliased.
|
||||
This can happen if the protocal is unrecognized,
|
||||
possibly an ICMP message type is not handled or
|
||||
if incoming packets for new connections are being
|
||||
ignored (see PKT_ALIAS_DENY_INCOMING in section
|
||||
2.2).
|
||||
.It PKT_ALIAS_UNRESOLVED_FRAGMENT.
|
||||
This is returned when a fragment cannot be
|
||||
resolved because the header fragment has not
|
||||
been sent yet. In this situation, fragments
|
||||
must be saved with PacketAliasSaveFragment()
|
||||
until a header fragment is found.
|
||||
.It PKT_ALIAS_FOUND_HEADER_FRAGMENT.
|
||||
The packet aliasing process was successful,
|
||||
and a header fragment was found. This is a
|
||||
signal to retrieve any unresolved fragments
|
||||
with PacketAliasGetFragment() and de-alias
|
||||
them with PacketAliasFragmentIn().
|
||||
.El
|
||||
.Ss 3.2 PacketAliasOut()
|
||||
|
||||
.Ft int
|
||||
.Fn PacketAliasIn "char *buffer" "int maxpacketsize"
|
||||
|
||||
An outgoing packet coming from the local network
|
||||
to a remote machine is aliased by this function.
|
||||
The IP packet is pointed to by
|
||||
.Em buffer r,
|
||||
and
|
||||
.Em maxpacketsize
|
||||
indicates the maximum packet size permissable
|
||||
should the packet length be changed. IP encoding
|
||||
protocols place addresss and port information in
|
||||
the encapsulated data stream which have to be
|
||||
modified and can account for changes in packet
|
||||
length. Well known examples of such protocols
|
||||
are FTP and IRC.
|
||||
|
||||
Return codes:
|
||||
.Bl -hang -offset left
|
||||
.It PKT_ALIAS_ERROR.
|
||||
An internal error within the packet aliasing
|
||||
engine occured.
|
||||
.It PKT_ALIAS_OK.
|
||||
The packet aliasing process was successful.
|
||||
.It PKT_ALIAS_IGNORED.
|
||||
The packet was ignored and not de-aliased.
|
||||
This can happen if the protocal is unrecognized,
|
||||
or possibly an ICMP message type is not handled.
|
||||
.El
|
||||
|
||||
.Sh 4. Port and Address Redirection
|
||||
The functions described in this section allow machines
|
||||
on the local network to be accessible in some degree
|
||||
to new incoming connections from the external network.
|
||||
Individual ports can be re-mapped or static network
|
||||
address translations can be designated.
|
||||
.Ss 4.1 PacketAliasRedirectPort()
|
||||
|
||||
.Ft struct alias_link *
|
||||
.Fo PacketAliasRedirectPort
|
||||
.Fa "struct in_addr local_addr"
|
||||
.Fa "u_short local_port"
|
||||
.Fa "struct in_addr remote_addr"
|
||||
.Fa "u_short remote_port"
|
||||
.Fa "struct in_addr alias_addr"
|
||||
.Fa "u_short alias_port"
|
||||
.Fa "u_char proto"
|
||||
.Fc
|
||||
|
||||
This function specifies that traffic from a
|
||||
given remote address/port to an alias address/port
|
||||
be redirected to a specified local address/port.
|
||||
The paramater
|
||||
.Em proto
|
||||
can be either IPPROTO_TCP or IPPROTO_UDP, as
|
||||
defined in <netinet/in.h>.
|
||||
|
||||
If
|
||||
.Em local_addr
|
||||
or
|
||||
.Em alias_addr
|
||||
is zero, this indicates that the packet aliasing
|
||||
address as established by PacketAliasSetAddress()
|
||||
is to be used. Even if PacketAliasAddress() is
|
||||
called to change the address after PacketAliasRedirectPort()
|
||||
is called, a zero reference will track this change.
|
||||
|
||||
If
|
||||
.Em remote_addr
|
||||
is zero, this indicates to redirect packets from
|
||||
any remote address. Likewise, if
|
||||
.Em remote_port
|
||||
is zero, this indicates to redirect packets originating
|
||||
from any remote port number. Almost always, the remote
|
||||
port specification will be zero, but non-zero remote
|
||||
addresses can be sometimes be useful for firewalling.
|
||||
If two calls to PacketAliasRedirectPort() overlap in
|
||||
their address/port specifications, then the most recent
|
||||
call will have precedence.
|
||||
|
||||
This function returns a pointer which can subsequently
|
||||
be used by PacketAliasRedirectDelete(). If NULL is
|
||||
returned, then the function call did not complete
|
||||
successfully.
|
||||
|
||||
All port numbers are in network address byte order,
|
||||
so it is necessary to use htons() to convert these
|
||||
parameters from internally readable numbers to
|
||||
network byte order. Addresses are also in network
|
||||
byte order, which is implicit in the use of the
|
||||
.Em struct in_addr
|
||||
data type.
|
||||
.Ss 4.2 PacketAliasRedirectAddr()
|
||||
|
||||
.Ft struct alias_link *
|
||||
.Fo PacketAliasRedirectAddress
|
||||
.Fa "struct in_addr local_addr"
|
||||
.Fa "struct in_addr alias_addr"
|
||||
.Fc
|
||||
|
||||
This function desgnates that all incoming
|
||||
traffic to
|
||||
.Em alias_addr
|
||||
be redirected to
|
||||
.Em local_addr.
|
||||
Similarly, all outgoing traffic from
|
||||
.Em local_addr
|
||||
is aliased to
|
||||
.Em alias_addr .
|
||||
|
||||
If
|
||||
.Em local_addr
|
||||
or
|
||||
.Em alias_addr
|
||||
is zero, this indicates that the packet aliasing
|
||||
address as established by PacketAliasSetAddress()
|
||||
is to be used. Even if PacketAliasAddress() is
|
||||
called to change the address after PacketAliasRedirectAddr()
|
||||
is called, a zero reference will track this change.
|
||||
|
||||
If subsequent calls to PacketAliasRedirectAddr()
|
||||
use the same aliasing address, all new incoming
|
||||
traffic to this aliasing address will be redirected
|
||||
to the local address made in the last function call,
|
||||
but new traffic all of the local machines designated
|
||||
in the several function calls will be aliased to
|
||||
the same address. Consider the following example:
|
||||
.Bd -literal -offset left
|
||||
PacketAliasRedirectAddr(inet_aton("192.168.0.2"),
|
||||
inet_aton("141.221.254.101"));
|
||||
PacketAliasRedirectAddr(inet_aton("192.168.0.3"),
|
||||
inet_aton("141.221.254.101"));
|
||||
PacketAliasRedirectAddr(inet_aton("192.168.0.4"),
|
||||
inet_aton("141.221.254.101"));
|
||||
.Ed
|
||||
|
||||
Any outgoing connections such as telnet or ftp
|
||||
from 192.168.0.2, 102.168.0.3, 192.168.0.4 will
|
||||
appear to come from 141.221.254.101. Any incoming
|
||||
connections to 141.221.254.101 will be directed
|
||||
to 192.168.0.4.
|
||||
|
||||
Any calls to PacketAliasRedirectPort() will
|
||||
have precedence over address mappings designated
|
||||
by PacketAliasRedirectAddr().
|
||||
|
||||
This function returns a pointer which can subsequently
|
||||
be used by PacketAliasRedirectDelete(). If NULL is
|
||||
returned, then the function call did not complete
|
||||
successfully.
|
||||
.Ss 4.3 PacketAliasRedirectDelete()
|
||||
|
||||
.Ft void
|
||||
.Fn PacketAliasRedirectDelete "struct alias_link *ptr"
|
||||
|
||||
This function will delete a specific static redirect
|
||||
rule entered by PacketAliasRedirectPort() or
|
||||
PacketAliasRedirectAddr(). The parameter
|
||||
.Em ptr
|
||||
is the pointer returned by either of the redirection
|
||||
functions. If an invalid pointer is passed to
|
||||
PacketAliasRedirectDelete(), then a program crash
|
||||
or unpredictable operation could result, so it is
|
||||
necessary to be careful using this function.
|
||||
|
||||
.Sh 5. Fragment Handling
|
||||
The functions in this section are used to deal with
|
||||
incoming fragments.
|
||||
|
||||
Outgoing fragments are handled within PacketAliasOut()
|
||||
by changing the address according to any
|
||||
applicable mapping set by PacketAliasRedirectAddress(),
|
||||
or the default aliasing address set by
|
||||
PacketAliasSetAddress().
|
||||
|
||||
Incoming fragments are handled in one of two ways.
|
||||
If the header of a fragmented IP packet has already
|
||||
been seen, then all subsequent fragments will be
|
||||
re-mapped in the same manner the header fragment
|
||||
was. Fragments which arrive before the header
|
||||
are saved and then retrieved once the header fragment
|
||||
has been resolved.
|
||||
.Ss 5.1 PacketAliasSaveFragment()
|
||||
|
||||
.Ft int
|
||||
.Fn PacketAliasSaveFragment "char *ptr"
|
||||
|
||||
When PacketAliasIn() returns
|
||||
PKT_ALIAS_UNRESOLVED_FRAGMENT, this
|
||||
function can be used to save the pointer to
|
||||
the unresolved fragment.
|
||||
|
||||
It is implicitly assumed that
|
||||
.Em ptr
|
||||
points to a block of memory allocated by
|
||||
malloc(). If the fragment is never
|
||||
resolved, the packet aliasing engine will
|
||||
automatically free the memory after a
|
||||
timeout period. [Eventually this function
|
||||
should be modified so that a callback
|
||||
function for freeing memory is passed as
|
||||
an argument.]
|
||||
|
||||
This function returns PKT_ALIAS_OK if it
|
||||
was successful and PKT_ALIAS_ERROR if there
|
||||
was an error.
|
||||
.Ss 5.2 PacketAliasGetNextFragment()
|
||||
|
||||
.Ft char *
|
||||
.Fn PacketAliasGetFragment "char *buffer"
|
||||
|
||||
This function can be used to retrieve fragment
|
||||
pointers saved by PacketAliasSaveFragment().
|
||||
The IP header fragment pointed to by
|
||||
Em buffer
|
||||
is the header fragment indicated when
|
||||
PacketAliasIn() returns PKT_ALIAS_FOUND_HEADER_FRAGMENT.
|
||||
Once a a fragment pointer is retrieved, it
|
||||
becomes the calling program's responsibility
|
||||
to free the dynamically allocated memory for
|
||||
the fragment.
|
||||
|
||||
PacketAliasGetFragment() can be called
|
||||
sequentially until there are no more fragments
|
||||
available, at which time it returns NULL.
|
||||
.Ss 5.3 PacketAliasFragmentIn()
|
||||
|
||||
.Ft void
|
||||
.Fn PacketAliasFragmentIn "char *header" "char *fragment"
|
||||
|
||||
When a fragment is retrieved with
|
||||
PacketAliasGetFragment(), it can then be
|
||||
de-aliased with a call to PacketAliasFragmentIn().
|
||||
.Em header
|
||||
is the pointer to a header fragment used as a
|
||||
template, and
|
||||
.Em fragment
|
||||
is the pointer to the packet to be de-aliased.
|
||||
|
||||
.Sh 6. Miscellaneous Functions
|
||||
|
||||
.Ss 6.1 PacketAliasSetTarget()
|
||||
|
||||
.Ft void
|
||||
.Fn PacketAliasSetTarget "struct in_addr addr"
|
||||
|
||||
When an incoming packet not associated with
|
||||
any pre-existing aliasing link arrives at the
|
||||
host machine, it will be sent to the address
|
||||
indicated by a call to PacketAliasSetTarget().
|
||||
|
||||
If this function is not called, or is called
|
||||
with a zero address argument, then all new
|
||||
incoming packets go to the address set by
|
||||
PacketAliasSetAddress.
|
||||
.Ss 6.2 PacketAliasCheckNewLink()
|
||||
|
||||
.Ft int
|
||||
.Fn PacketAliasCheckNewLink "void"
|
||||
|
||||
This function returns a non-zero value when
|
||||
a new aliasing link is created. In circumstances
|
||||
where incoming traffic is being sequentially
|
||||
sent to different local servers, this function
|
||||
can be used to trigger when PacketAliasSetTarget()
|
||||
is called to change the default target address.
|
||||
.Ss 6.3 PacketAliasInternetChecksum()
|
||||
|
||||
.Ft u_short
|
||||
.Fn PacketAliasInternetChecksum "char *buffer" "int nbytes"
|
||||
|
||||
This is a utility function that does not seem
|
||||
to be available elswhere and is included as a
|
||||
convenience. It computes the internet checksum,
|
||||
which is used in both IP and protocol-specific
|
||||
headers (TCP, UDP, ICMP).
|
||||
|
||||
.Em buffer
|
||||
points to the data block to be checksummed, and
|
||||
.Em nbytes
|
||||
is the number of bytes. The 16-bit checksum
|
||||
field should be zeroed before computing the checksum.
|
||||
|
||||
Checksums can also be verified by operating on a block
|
||||
of data including its checksum. If the checksum is
|
||||
valid, PacketAliasInternetChecksum() will return zero.
|
||||
|
||||
.Sh 7. Authors
|
||||
Charles Mott (cmott@srv.net), versions 1.0 - 1.8, 2.0 - 2.2.
|
||||
|
||||
Eivind Eiklund (eivind@freebsd.org), versions 1.8b and 1.9.
|
||||
Added IRC support as well as contributing a number of
|
||||
architectural improvements.
|
||||
|
||||
.Sh 8. Acknowledgments
|
||||
|
||||
Listed below, in approximate chronological
|
||||
order, are individuals who have provided
|
||||
valuable comments and/or debugging assistance.
|
||||
|
||||
.Bl -inset -compact -offset left
|
||||
.It Gary Roberts
|
||||
.It Tom Torrance
|
||||
.It Reto Burkhalter
|
||||
.It Martin Renters
|
||||
.It Brian Somers
|
||||
.It Paul Traina
|
||||
.It Ari Suutari
|
||||
.It Dave Remien
|
||||
.It J. Fortes
|
||||
.It Andrzej Bialeki
|
||||
.El
|
||||
|
||||
.Sh Appendix: Conceptual Background
|
||||
This appendix is intended for those who
|
||||
are planning to modify the source code or want
|
||||
to create somewhat esoteric applications using
|
||||
the packet aliasing functions.
|
||||
|
||||
The conceptual framework under which the
|
||||
packet aliasing engine operates is described here.
|
||||
Central to the discussion is the idea of an
|
||||
"aliasing link" which describes the relationship
|
||||
for a given packet transaction between the local
|
||||
machine, aliased identity and remote machine. It
|
||||
is discussed how such links come into existence
|
||||
and are destroyed.
|
||||
.Ss A.1 Aliasing Links
|
||||
There is a notion of an "aliasing link",
|
||||
which is 7-tuple describing a specific
|
||||
translation:
|
||||
.Bd -literal -offset indent
|
||||
(local addr, local port, alias addr, alias port,
|
||||
remote addr, remote port, protocol)
|
||||
.Ed
|
||||
|
||||
Outgoing packets have the local address and
|
||||
port number replaced with the alias address
|
||||
and port number. Incoming packets undergo the
|
||||
reverse process. The packet aliasing engine
|
||||
attempts to match packets against an internal
|
||||
table of aliasing links to determine how to
|
||||
modify a given IP packet. Both the IP
|
||||
header and protocol dependent headers are
|
||||
modified as necessary. Aliasing links are
|
||||
created and deleted as necessary according
|
||||
to network traffic.
|
||||
|
||||
Protocols can be TCP, UDP or even ICMP in
|
||||
certain circumstances. (Some types of ICMP
|
||||
packets can be aliased according to sequence
|
||||
or id number which acts as an equivalent port
|
||||
number for identifying how individual packets
|
||||
should be handled.)
|
||||
|
||||
Each aliasing link must have a unique
|
||||
combination of the following five quanties:
|
||||
alias address/port, remote address/port
|
||||
and protocol. This ensures that several
|
||||
machines on a local network can share the
|
||||
same aliased IP address. In cases where
|
||||
conflicts might arise, the aliasing port
|
||||
is chosen so that uniqueness is maintained.
|
||||
.Ss A.2 Static and Dynamic Links
|
||||
Aliasing links can either be static or dynamic.
|
||||
Static links persist indefinitely and represent
|
||||
fixed rules for translating IP packets. Dynamic
|
||||
links come into existence for a specific TCP
|
||||
connection or UDP transaction or ICMP echo
|
||||
sequence. For the case of TCP, the connection
|
||||
can be monitored to see when the associated
|
||||
aliasing link should be deleted. Aliasing links
|
||||
for UDP transactions (and ICMP echo and timestamp
|
||||
equests) work on a simple timeout rule. When
|
||||
no activity is observed on a dynamic link for
|
||||
a certain amount of time it is automatically
|
||||
deleted. Timeout rules also apply to TCP
|
||||
connections which do not open or close
|
||||
properly.
|
||||
.Ss A.3 Partially Specified Aliasing Links
|
||||
Aliasing links can be partially specified,
|
||||
meaning that the remote address and/or remote
|
||||
ports are unkown. In this case, when a packet
|
||||
matching the incomplete specification is found,
|
||||
a fully specified dynamic link is created. If
|
||||
the original partially specified link is dynamic,
|
||||
it will be deleted after the fully specified link
|
||||
is created, otherwise it will persist.
|
||||
|
||||
For instance, a partially specified link might
|
||||
be
|
||||
.Bd -literal -offset indent
|
||||
(192.168.0.4, 23, 204.228.203.215, 8066, 0, 0, tcp)
|
||||
.Ed
|
||||
|
||||
The zeros denote unspecified components for
|
||||
the remote address and port. If this link were
|
||||
static it would have the effect of redirecting
|
||||
all incoming traffic from port 8066 of
|
||||
204.228.203.215 to port 23 (telnet) of machine
|
||||
192.168.0.4 on the local network. Each
|
||||
individual telnet connection would initiate
|
||||
the creation of a distinct dynamic link.
|
||||
.Ss A.4 Dynamic Link Creation
|
||||
In addition to aliasing links, there are
|
||||
also address mappings that can be stored
|
||||
within the internal data table of the packet
|
||||
aliasing mechanism.
|
||||
.Bd -literal -offset indent
|
||||
(local addr, alias addr)
|
||||
.Ed
|
||||
|
||||
Address mappings are searched when creating
|
||||
new dynamic links.
|
||||
|
||||
All outgoing packets from the local network
|
||||
automatically create a dynamic link if
|
||||
they do not match an already existing fully
|
||||
specified link. If an address mapping exists
|
||||
for the the outgoing packet, this determines
|
||||
the alias address to be used. If no mapping
|
||||
exists, then a default address, usually the
|
||||
address of the packet aliasing host, is used.
|
||||
If necessary, this default address can be
|
||||
changed as often as each indvidual packet
|
||||
arrives.
|
||||
|
||||
The aliasing port number is determined
|
||||
such that the new dynamic link does not
|
||||
conflict with any existing links. In the
|
||||
default operating mode, the packet aliasing
|
||||
engine attempts to set the aliasing port
|
||||
equal to the local port number. If this
|
||||
results in a conflict, then port numbers
|
||||
are randomly chosen until a unique aliasing
|
||||
link can be established. In an alternate
|
||||
operating mode, the first choice of an
|
||||
aliasing port is also random and unrelated
|
||||
to the local port number.
|
||||
|
||||
Loading…
Reference in New Issue
Block a user