a short pointer. The previous implementation seems to be in a gray zone of the C standard, and GCC generates incorrect code for it at -O2 or higher on some platforms.
1434 lines
39 KiB
C
1434 lines
39 KiB
C
/*-
|
|
* Copyright (c) 2001 Charles Mott <cm@linktel.net>
|
|
* All rights reserved.
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following conditions
|
|
* are met:
|
|
* 1. Redistributions of source code must retain the above copyright
|
|
* notice, this list of conditions and the following disclaimer.
|
|
* 2. Redistributions in binary form must reproduce the above copyright
|
|
* notice, this list of conditions and the following disclaimer in the
|
|
* documentation and/or other materials provided with the distribution.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
|
|
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
|
|
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
* SUCH DAMAGE.
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|
*/
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|
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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|
|
|
/*
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|
Alias.c provides supervisory control for the functions of the
|
|
packet aliasing software. It consists of routines to monitor
|
|
TCP connection state, protocol-specific aliasing routines,
|
|
fragment handling and the following outside world functional
|
|
interfaces: SaveFragmentPtr, GetFragmentPtr, FragmentAliasIn,
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|
PacketAliasIn and PacketAliasOut.
|
|
|
|
The other C program files are briefly described. The data
|
|
structure framework which holds information needed to translate
|
|
packets is encapsulated in alias_db.c. Data is accessed by
|
|
function calls, so other segments of the program need not know
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|
about the underlying data structures. Alias_ftp.c contains
|
|
special code for modifying the ftp PORT command used to establish
|
|
data connections, while alias_irc.c does the same for IRC
|
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DCC. Alias_util.c contains a few utility routines.
|
|
|
|
Version 1.0 August, 1996 (cjm)
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|
|
|
Version 1.1 August 20, 1996 (cjm)
|
|
PPP host accepts incoming connections for ports 0 to 1023.
|
|
(Gary Roberts pointed out the need to handle incoming
|
|
connections.)
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|
|
|
Version 1.2 September 7, 1996 (cjm)
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|
Fragment handling error in alias_db.c corrected.
|
|
(Tom Torrance helped fix this problem.)
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|
|
|
Version 1.4 September 16, 1996 (cjm)
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|
- A more generalized method for handling incoming
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|
connections, without the 0-1023 restriction, is
|
|
implemented in alias_db.c
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|
- Improved ICMP support in alias.c. Traceroute
|
|
packet streams can now be correctly aliased.
|
|
- TCP connection closing logic simplified in
|
|
alias.c and now allows for additional 1 minute
|
|
"grace period" after FIN or RST is observed.
|
|
|
|
Version 1.5 September 17, 1996 (cjm)
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|
Corrected error in handling incoming UDP packets with 0 checksum.
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|
(Tom Torrance helped fix this problem.)
|
|
|
|
Version 1.6 September 18, 1996 (cjm)
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|
Simplified ICMP aliasing scheme. Should now support
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|
traceroute from Win95 as well as FreeBSD.
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|
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|
Version 1.7 January 9, 1997 (cjm)
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- Out-of-order fragment handling.
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- IP checksum error fixed for ftp transfers
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|
from aliasing host.
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- Integer return codes added to all
|
|
aliasing/de-aliasing functions.
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|
- Some obsolete comments cleaned up.
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|
- Differential checksum computations for
|
|
IP header (TCP, UDP and ICMP were already
|
|
differential).
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|
|
|
Version 2.1 May 1997 (cjm)
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|
- Added support for outgoing ICMP error
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|
messages.
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|
- Added two functions PacketAliasIn2()
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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
|
|
PacketAliasOut2() as poorly conceived.
|
|
|
|
Version 2.3 Dec 1998 (dillon)
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|
- Major bounds checking additions, see FreeBSD/CVS
|
|
|
|
Version 3.1 May, 2000 (salander)
|
|
- Added hooks to handle PPTP.
|
|
|
|
Version 3.2 July, 2000 (salander and satoh)
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|
- Added PacketUnaliasOut routine.
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|
- Added hooks to handle RTSP/RTP.
|
|
|
|
See HISTORY file for additional revisions.
|
|
*/
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|
|
|
#include <sys/types.h>
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|
|
|
#include <netinet/in_systm.h>
|
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#include <netinet/in.h>
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#include <netinet/ip.h>
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|
#include <netinet/ip_icmp.h>
|
|
#include <netinet/tcp.h>
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|
#include <netinet/udp.h>
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|
|
|
#include <stdio.h>
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|
|
|
#include "alias_local.h"
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|
#include "alias.h"
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|
|
|
#define NETBIOS_NS_PORT_NUMBER 137
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#define NETBIOS_DGM_PORT_NUMBER 138
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#define FTP_CONTROL_PORT_NUMBER 21
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|
#define IRC_CONTROL_PORT_NUMBER_1 6667
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#define IRC_CONTROL_PORT_NUMBER_2 6668
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#define CUSEEME_PORT_NUMBER 7648
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#define RTSP_CONTROL_PORT_NUMBER_1 554
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#define RTSP_CONTROL_PORT_NUMBER_2 7070
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#define TFTP_PORT_NUMBER 69
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#define PPTP_CONTROL_PORT_NUMBER 1723
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|
|
|
static __inline int
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|
twowords(void *p)
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|
{
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uint8_t *c = p;
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|
|
|
#if BYTE_ORDER == LITTLE_ENDIAN
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uint16_t s1 = ((uint16_t)c[1] << 8) + (uint16_t)c[0];
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uint16_t s2 = ((uint16_t)c[3] << 8) + (uint16_t)c[2];
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#else
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uint16_t s1 = ((uint16_t)c[0] << 8) + (uint16_t)c[1];
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uint16_t s2 = ((uint16_t)c[2] << 8) + (uint16_t)c[3];
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|
#endif
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return (s1 + s2);
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|
}
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|
|
/* TCP Handling Routines
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|
TcpMonitorIn() -- These routines monitor TCP connections, and
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TcpMonitorOut() delete a link when a connection is closed.
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|
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|
These routines look for SYN, FIN and RST flags to determine when TCP
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connections open and close. When a TCP connection closes, the data
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structure containing packet aliasing information is deleted after
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|
a timeout period.
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*/
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|
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|
/* Local prototypes */
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|
static void TcpMonitorIn(struct ip *, struct alias_link *);
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|
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|
static void TcpMonitorOut(struct ip *, struct alias_link *);
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|
|
|
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|
static void
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|
TcpMonitorIn(struct ip *pip, struct alias_link *lnk)
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|
{
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|
struct tcphdr *tc;
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|
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|
tc = (struct tcphdr *)((char *)pip + (pip->ip_hl << 2));
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|
switch (GetStateIn(lnk)) {
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case ALIAS_TCP_STATE_NOT_CONNECTED:
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if (tc->th_flags & TH_RST)
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SetStateIn(lnk, ALIAS_TCP_STATE_DISCONNECTED);
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|
else if (tc->th_flags & TH_SYN)
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SetStateIn(lnk, ALIAS_TCP_STATE_CONNECTED);
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|
break;
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|
case ALIAS_TCP_STATE_CONNECTED:
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|
if (tc->th_flags & (TH_FIN | TH_RST))
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SetStateIn(lnk, ALIAS_TCP_STATE_DISCONNECTED);
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break;
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|
}
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|
}
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|
|
|
static void
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|
TcpMonitorOut(struct ip *pip, struct alias_link *lnk)
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|
{
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|
struct tcphdr *tc;
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|
|
|
tc = (struct tcphdr *)((char *)pip + (pip->ip_hl << 2));
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|
|
|
switch (GetStateOut(lnk)) {
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|
case ALIAS_TCP_STATE_NOT_CONNECTED:
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|
if (tc->th_flags & TH_RST)
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|
SetStateOut(lnk, ALIAS_TCP_STATE_DISCONNECTED);
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|
else if (tc->th_flags & TH_SYN)
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SetStateOut(lnk, ALIAS_TCP_STATE_CONNECTED);
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|
break;
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|
case ALIAS_TCP_STATE_CONNECTED:
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if (tc->th_flags & (TH_FIN | TH_RST))
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SetStateOut(lnk, ALIAS_TCP_STATE_DISCONNECTED);
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|
break;
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|
}
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|
}
|
|
|
|
|
|
|
|
|
|
|
|
/* Protocol Specific Packet Aliasing Routines
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|
|
|
IcmpAliasIn(), IcmpAliasIn1(), IcmpAliasIn2()
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|
IcmpAliasOut(), IcmpAliasOut1(), IcmpAliasOut2()
|
|
ProtoAliasIn(), ProtoAliasOut()
|
|
UdpAliasIn(), UdpAliasOut()
|
|
TcpAliasIn(), TcpAliasOut()
|
|
|
|
These routines handle protocol specific details of packet aliasing.
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|
One may observe a certain amount of repetitive arithmetic in these
|
|
functions, the purpose of which is to compute a revised checksum
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|
without actually summing over the entire data packet, which could be
|
|
unnecessarily time consuming.
|
|
|
|
The purpose of the packet aliasing routines is to replace the source
|
|
address of the outgoing packet and then correctly put it back for
|
|
any incoming packets. For TCP and UDP, ports are also re-mapped.
|
|
|
|
For ICMP echo/timestamp requests and replies, the following scheme
|
|
is used: the ID number is replaced by an alias for the outgoing
|
|
packet.
|
|
|
|
ICMP error messages are handled by looking at the IP fragment
|
|
in the data section of the message.
|
|
|
|
For TCP and UDP protocols, a port number is chosen for an outgoing
|
|
packet, and then incoming packets are identified by IP address and
|
|
port numbers. For TCP packets, there is additional logic in the event
|
|
that sequence and ACK numbers have been altered (as in the case for
|
|
FTP data port commands).
|
|
|
|
The port numbers used by the packet aliasing module are not true
|
|
ports in the Unix sense. No sockets are actually bound to ports.
|
|
They are more correctly thought of as placeholders.
|
|
|
|
All packets go through the aliasing mechanism, whether they come from
|
|
the gateway machine or other machines on a local area network.
|
|
*/
|
|
|
|
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|
/* Local prototypes */
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|
static int IcmpAliasIn1(struct libalias *, struct ip *);
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|
static int IcmpAliasIn2(struct libalias *, struct ip *);
|
|
static int IcmpAliasIn(struct libalias *, struct ip *);
|
|
|
|
static int IcmpAliasOut1(struct libalias *, struct ip *);
|
|
static int IcmpAliasOut2(struct libalias *, struct ip *);
|
|
static int IcmpAliasOut(struct libalias *, struct ip *, int create);
|
|
|
|
static int ProtoAliasIn(struct libalias *, struct ip *);
|
|
static int ProtoAliasOut(struct libalias *, struct ip *, int create);
|
|
|
|
static int UdpAliasIn(struct libalias *, struct ip *);
|
|
static int UdpAliasOut(struct libalias *, struct ip *, int create);
|
|
|
|
static int TcpAliasIn(struct libalias *, struct ip *);
|
|
static int TcpAliasOut(struct libalias *, struct ip *, int, int create);
|
|
|
|
|
|
static int
|
|
IcmpAliasIn1(struct libalias *la, struct ip *pip)
|
|
{
|
|
/*
|
|
De-alias incoming echo and timestamp replies.
|
|
Alias incoming echo and timestamp requests.
|
|
*/
|
|
struct alias_link *lnk;
|
|
struct icmp *ic;
|
|
|
|
ic = (struct icmp *)((char *)pip + (pip->ip_hl << 2));
|
|
|
|
/* Get source address from ICMP data field and restore original data */
|
|
lnk = FindIcmpIn(la, pip->ip_src, pip->ip_dst, ic->icmp_id, 1);
|
|
if (lnk != NULL) {
|
|
u_short original_id;
|
|
int accumulate;
|
|
|
|
original_id = GetOriginalPort(lnk);
|
|
|
|
/* Adjust ICMP checksum */
|
|
accumulate = ic->icmp_id;
|
|
accumulate -= original_id;
|
|
ADJUST_CHECKSUM(accumulate, ic->icmp_cksum);
|
|
|
|
/* Put original sequence number back in */
|
|
ic->icmp_id = original_id;
|
|
|
|
/* Put original address back into IP header */
|
|
{
|
|
struct in_addr original_address;
|
|
|
|
original_address = GetOriginalAddress(lnk);
|
|
DifferentialChecksum(&pip->ip_sum,
|
|
&original_address, &pip->ip_dst, 2);
|
|
pip->ip_dst = original_address;
|
|
}
|
|
|
|
return (PKT_ALIAS_OK);
|
|
}
|
|
return (PKT_ALIAS_IGNORED);
|
|
}
|
|
|
|
static int
|
|
IcmpAliasIn2(struct libalias *la, struct ip *pip)
|
|
{
|
|
/*
|
|
Alias incoming ICMP error messages containing
|
|
IP header and first 64 bits of datagram.
|
|
*/
|
|
struct ip *ip;
|
|
struct icmp *ic, *ic2;
|
|
struct udphdr *ud;
|
|
struct tcphdr *tc;
|
|
struct alias_link *lnk;
|
|
|
|
ic = (struct icmp *)((char *)pip + (pip->ip_hl << 2));
|
|
ip = &ic->icmp_ip;
|
|
|
|
ud = (struct udphdr *)((char *)ip + (ip->ip_hl << 2));
|
|
tc = (struct tcphdr *)ud;
|
|
ic2 = (struct icmp *)ud;
|
|
|
|
if (ip->ip_p == IPPROTO_UDP)
|
|
lnk = FindUdpTcpIn(la, ip->ip_dst, ip->ip_src,
|
|
ud->uh_dport, ud->uh_sport,
|
|
IPPROTO_UDP, 0);
|
|
else if (ip->ip_p == IPPROTO_TCP)
|
|
lnk = FindUdpTcpIn(la, ip->ip_dst, ip->ip_src,
|
|
tc->th_dport, tc->th_sport,
|
|
IPPROTO_TCP, 0);
|
|
else if (ip->ip_p == IPPROTO_ICMP) {
|
|
if (ic2->icmp_type == ICMP_ECHO || ic2->icmp_type == ICMP_TSTAMP)
|
|
lnk = FindIcmpIn(la, ip->ip_dst, ip->ip_src, ic2->icmp_id, 0);
|
|
else
|
|
lnk = NULL;
|
|
} else
|
|
lnk = NULL;
|
|
|
|
if (lnk != NULL) {
|
|
if (ip->ip_p == IPPROTO_UDP || ip->ip_p == IPPROTO_TCP) {
|
|
int accumulate, accumulate2;
|
|
struct in_addr original_address;
|
|
u_short original_port;
|
|
|
|
original_address = GetOriginalAddress(lnk);
|
|
original_port = GetOriginalPort(lnk);
|
|
|
|
/* Adjust ICMP checksum */
|
|
accumulate = twowords(&ip->ip_src);
|
|
accumulate -= twowords(&original_address);
|
|
accumulate += ud->uh_sport;
|
|
accumulate -= original_port;
|
|
accumulate2 = accumulate;
|
|
accumulate2 += ip->ip_sum;
|
|
ADJUST_CHECKSUM(accumulate, ip->ip_sum);
|
|
accumulate2 -= ip->ip_sum;
|
|
ADJUST_CHECKSUM(accumulate2, ic->icmp_cksum);
|
|
|
|
/* Un-alias address in IP header */
|
|
DifferentialChecksum(&pip->ip_sum,
|
|
&original_address, &pip->ip_dst, 2);
|
|
pip->ip_dst = original_address;
|
|
|
|
/* Un-alias address and port number of original IP packet
|
|
fragment contained in ICMP data section */
|
|
ip->ip_src = original_address;
|
|
ud->uh_sport = original_port;
|
|
} else if (ip->ip_p == IPPROTO_ICMP) {
|
|
int accumulate, accumulate2;
|
|
struct in_addr original_address;
|
|
u_short original_id;
|
|
|
|
original_address = GetOriginalAddress(lnk);
|
|
original_id = GetOriginalPort(lnk);
|
|
|
|
/* Adjust ICMP checksum */
|
|
accumulate = twowords(&ip->ip_src);
|
|
accumulate -= twowords(&original_address);
|
|
accumulate += ic2->icmp_id;
|
|
accumulate -= original_id;
|
|
accumulate2 = accumulate;
|
|
accumulate2 += ip->ip_sum;
|
|
ADJUST_CHECKSUM(accumulate, ip->ip_sum);
|
|
accumulate2 -= ip->ip_sum;
|
|
ADJUST_CHECKSUM(accumulate2, ic->icmp_cksum);
|
|
|
|
/* Un-alias address in IP header */
|
|
DifferentialChecksum(&pip->ip_sum,
|
|
&original_address, &pip->ip_dst, 2);
|
|
pip->ip_dst = original_address;
|
|
|
|
/* Un-alias address of original IP packet and sequence number of
|
|
embedded ICMP datagram */
|
|
ip->ip_src = original_address;
|
|
ic2->icmp_id = original_id;
|
|
}
|
|
return (PKT_ALIAS_OK);
|
|
}
|
|
return (PKT_ALIAS_IGNORED);
|
|
}
|
|
|
|
|
|
static int
|
|
IcmpAliasIn(struct libalias *la, struct ip *pip)
|
|
{
|
|
int iresult;
|
|
struct icmp *ic;
|
|
|
|
/* Return if proxy-only mode is enabled */
|
|
if (la->packetAliasMode & PKT_ALIAS_PROXY_ONLY)
|
|
return (PKT_ALIAS_OK);
|
|
|
|
ic = (struct icmp *)((char *)pip + (pip->ip_hl << 2));
|
|
|
|
iresult = PKT_ALIAS_IGNORED;
|
|
switch (ic->icmp_type) {
|
|
case ICMP_ECHOREPLY:
|
|
case ICMP_TSTAMPREPLY:
|
|
if (ic->icmp_code == 0) {
|
|
iresult = IcmpAliasIn1(la, pip);
|
|
}
|
|
break;
|
|
case ICMP_UNREACH:
|
|
case ICMP_SOURCEQUENCH:
|
|
case ICMP_TIMXCEED:
|
|
case ICMP_PARAMPROB:
|
|
iresult = IcmpAliasIn2(la, pip);
|
|
break;
|
|
case ICMP_ECHO:
|
|
case ICMP_TSTAMP:
|
|
iresult = IcmpAliasIn1(la, pip);
|
|
break;
|
|
}
|
|
return (iresult);
|
|
}
|
|
|
|
|
|
static int
|
|
IcmpAliasOut1(struct libalias *la, struct ip *pip)
|
|
{
|
|
/*
|
|
Alias outgoing echo and timestamp requests.
|
|
De-alias outgoing echo and timestamp replies.
|
|
*/
|
|
struct alias_link *lnk;
|
|
struct icmp *ic;
|
|
|
|
ic = (struct icmp *)((char *)pip + (pip->ip_hl << 2));
|
|
|
|
/* Save overwritten data for when echo packet returns */
|
|
lnk = FindIcmpOut(la, pip->ip_src, pip->ip_dst, ic->icmp_id, 1);
|
|
if (lnk != NULL) {
|
|
u_short alias_id;
|
|
int accumulate;
|
|
|
|
alias_id = GetAliasPort(lnk);
|
|
|
|
/* Since data field is being modified, adjust ICMP checksum */
|
|
accumulate = ic->icmp_id;
|
|
accumulate -= alias_id;
|
|
ADJUST_CHECKSUM(accumulate, ic->icmp_cksum);
|
|
|
|
/* Alias sequence number */
|
|
ic->icmp_id = alias_id;
|
|
|
|
/* Change source address */
|
|
{
|
|
struct in_addr alias_address;
|
|
|
|
alias_address = GetAliasAddress(lnk);
|
|
DifferentialChecksum(&pip->ip_sum,
|
|
&alias_address, &pip->ip_src, 2);
|
|
pip->ip_src = alias_address;
|
|
}
|
|
|
|
return (PKT_ALIAS_OK);
|
|
}
|
|
return (PKT_ALIAS_IGNORED);
|
|
}
|
|
|
|
|
|
static int
|
|
IcmpAliasOut2(struct libalias *la, struct ip *pip)
|
|
{
|
|
/*
|
|
Alias outgoing ICMP error messages containing
|
|
IP header and first 64 bits of datagram.
|
|
*/
|
|
struct ip *ip;
|
|
struct icmp *ic, *ic2;
|
|
struct udphdr *ud;
|
|
struct tcphdr *tc;
|
|
struct alias_link *lnk;
|
|
|
|
ic = (struct icmp *)((char *)pip + (pip->ip_hl << 2));
|
|
ip = &ic->icmp_ip;
|
|
|
|
ud = (struct udphdr *)((char *)ip + (ip->ip_hl << 2));
|
|
tc = (struct tcphdr *)ud;
|
|
ic2 = (struct icmp *)ud;
|
|
|
|
if (ip->ip_p == IPPROTO_UDP)
|
|
lnk = FindUdpTcpOut(la, ip->ip_dst, ip->ip_src,
|
|
ud->uh_dport, ud->uh_sport,
|
|
IPPROTO_UDP, 0);
|
|
else if (ip->ip_p == IPPROTO_TCP)
|
|
lnk = FindUdpTcpOut(la, ip->ip_dst, ip->ip_src,
|
|
tc->th_dport, tc->th_sport,
|
|
IPPROTO_TCP, 0);
|
|
else if (ip->ip_p == IPPROTO_ICMP) {
|
|
if (ic2->icmp_type == ICMP_ECHO || ic2->icmp_type == ICMP_TSTAMP)
|
|
lnk = FindIcmpOut(la, ip->ip_dst, ip->ip_src, ic2->icmp_id, 0);
|
|
else
|
|
lnk = NULL;
|
|
} else
|
|
lnk = NULL;
|
|
|
|
if (lnk != NULL) {
|
|
if (ip->ip_p == IPPROTO_UDP || ip->ip_p == IPPROTO_TCP) {
|
|
int accumulate;
|
|
struct in_addr alias_address;
|
|
u_short alias_port;
|
|
|
|
alias_address = GetAliasAddress(lnk);
|
|
alias_port = GetAliasPort(lnk);
|
|
|
|
/* Adjust ICMP checksum */
|
|
accumulate = twowords(&ip->ip_dst);
|
|
accumulate -= twowords(&alias_address);
|
|
accumulate += ud->uh_dport;
|
|
accumulate -= alias_port;
|
|
ADJUST_CHECKSUM(accumulate, ic->icmp_cksum);
|
|
|
|
/*
|
|
* Alias address in IP header if it comes from the host
|
|
* the original TCP/UDP packet was destined for.
|
|
*/
|
|
if (pip->ip_src.s_addr == ip->ip_dst.s_addr) {
|
|
DifferentialChecksum(&pip->ip_sum,
|
|
&alias_address, &pip->ip_src, 2);
|
|
pip->ip_src = alias_address;
|
|
}
|
|
/* Alias address and port number of original IP packet
|
|
fragment contained in ICMP data section */
|
|
ip->ip_dst = alias_address;
|
|
ud->uh_dport = alias_port;
|
|
} else if (ip->ip_p == IPPROTO_ICMP) {
|
|
int accumulate;
|
|
struct in_addr alias_address;
|
|
u_short alias_id;
|
|
|
|
alias_address = GetAliasAddress(lnk);
|
|
alias_id = GetAliasPort(lnk);
|
|
|
|
/* Adjust ICMP checksum */
|
|
accumulate = twowords(&ip->ip_dst);
|
|
accumulate -= twowords(&alias_address);
|
|
accumulate += ic2->icmp_id;
|
|
accumulate -= alias_id;
|
|
ADJUST_CHECKSUM(accumulate, ic->icmp_cksum);
|
|
|
|
/*
|
|
* Alias address in IP header if it comes from the host
|
|
* the original ICMP message was destined for.
|
|
*/
|
|
if (pip->ip_src.s_addr == ip->ip_dst.s_addr) {
|
|
DifferentialChecksum(&pip->ip_sum,
|
|
&alias_address, &pip->ip_src, 2);
|
|
pip->ip_src = alias_address;
|
|
}
|
|
/* Alias address of original IP packet and sequence number of
|
|
embedded ICMP datagram */
|
|
ip->ip_dst = alias_address;
|
|
ic2->icmp_id = alias_id;
|
|
}
|
|
return (PKT_ALIAS_OK);
|
|
}
|
|
return (PKT_ALIAS_IGNORED);
|
|
}
|
|
|
|
|
|
static int
|
|
IcmpAliasOut(struct libalias *la, struct ip *pip, int create)
|
|
{
|
|
int iresult;
|
|
struct icmp *ic;
|
|
|
|
(void)create;
|
|
|
|
/* Return if proxy-only mode is enabled */
|
|
if (la->packetAliasMode & PKT_ALIAS_PROXY_ONLY)
|
|
return (PKT_ALIAS_OK);
|
|
|
|
ic = (struct icmp *)((char *)pip + (pip->ip_hl << 2));
|
|
|
|
iresult = PKT_ALIAS_IGNORED;
|
|
switch (ic->icmp_type) {
|
|
case ICMP_ECHO:
|
|
case ICMP_TSTAMP:
|
|
if (ic->icmp_code == 0) {
|
|
iresult = IcmpAliasOut1(la, pip);
|
|
}
|
|
break;
|
|
case ICMP_UNREACH:
|
|
case ICMP_SOURCEQUENCH:
|
|
case ICMP_TIMXCEED:
|
|
case ICMP_PARAMPROB:
|
|
iresult = IcmpAliasOut2(la, pip);
|
|
break;
|
|
case ICMP_ECHOREPLY:
|
|
case ICMP_TSTAMPREPLY:
|
|
iresult = IcmpAliasOut1(la, pip);
|
|
}
|
|
return (iresult);
|
|
}
|
|
|
|
|
|
|
|
static int
|
|
ProtoAliasIn(struct libalias *la, struct ip *pip)
|
|
{
|
|
/*
|
|
Handle incoming IP packets. The
|
|
only thing which is done in this case is to alias
|
|
the dest IP address of the packet to our inside
|
|
machine.
|
|
*/
|
|
struct alias_link *lnk;
|
|
|
|
/* Return if proxy-only mode is enabled */
|
|
if (la->packetAliasMode & PKT_ALIAS_PROXY_ONLY)
|
|
return (PKT_ALIAS_OK);
|
|
|
|
lnk = FindProtoIn(la, pip->ip_src, pip->ip_dst, pip->ip_p);
|
|
if (lnk != NULL) {
|
|
struct in_addr original_address;
|
|
|
|
original_address = GetOriginalAddress(lnk);
|
|
|
|
/* Restore original IP address */
|
|
DifferentialChecksum(&pip->ip_sum,
|
|
&original_address, &pip->ip_dst, 2);
|
|
pip->ip_dst = original_address;
|
|
|
|
return (PKT_ALIAS_OK);
|
|
}
|
|
return (PKT_ALIAS_IGNORED);
|
|
}
|
|
|
|
|
|
static int
|
|
ProtoAliasOut(struct libalias *la, struct ip *pip, int create)
|
|
{
|
|
/*
|
|
Handle outgoing IP packets. The
|
|
only thing which is done in this case is to alias
|
|
the source IP address of the packet.
|
|
*/
|
|
struct alias_link *lnk;
|
|
|
|
(void)create;
|
|
|
|
/* Return if proxy-only mode is enabled */
|
|
if (la->packetAliasMode & PKT_ALIAS_PROXY_ONLY)
|
|
return (PKT_ALIAS_OK);
|
|
|
|
lnk = FindProtoOut(la, pip->ip_src, pip->ip_dst, pip->ip_p);
|
|
if (lnk != NULL) {
|
|
struct in_addr alias_address;
|
|
|
|
alias_address = GetAliasAddress(lnk);
|
|
|
|
/* Change source address */
|
|
DifferentialChecksum(&pip->ip_sum,
|
|
&alias_address, &pip->ip_src, 2);
|
|
pip->ip_src = alias_address;
|
|
|
|
return (PKT_ALIAS_OK);
|
|
}
|
|
return (PKT_ALIAS_IGNORED);
|
|
}
|
|
|
|
|
|
static int
|
|
UdpAliasIn(struct libalias *la, struct ip *pip)
|
|
{
|
|
struct udphdr *ud;
|
|
struct alias_link *lnk;
|
|
|
|
/* Return if proxy-only mode is enabled */
|
|
if (la->packetAliasMode & PKT_ALIAS_PROXY_ONLY)
|
|
return (PKT_ALIAS_OK);
|
|
|
|
ud = (struct udphdr *)((char *)pip + (pip->ip_hl << 2));
|
|
|
|
lnk = FindUdpTcpIn(la, pip->ip_src, pip->ip_dst,
|
|
ud->uh_sport, ud->uh_dport,
|
|
IPPROTO_UDP, 1);
|
|
if (lnk != NULL) {
|
|
struct in_addr alias_address;
|
|
struct in_addr original_address;
|
|
u_short alias_port;
|
|
int accumulate;
|
|
int r = 0;
|
|
|
|
alias_address = GetAliasAddress(lnk);
|
|
original_address = GetOriginalAddress(lnk);
|
|
alias_port = ud->uh_dport;
|
|
ud->uh_dport = GetOriginalPort(lnk);
|
|
|
|
/* Special processing for IP encoding protocols */
|
|
if (ntohs(ud->uh_dport) == CUSEEME_PORT_NUMBER)
|
|
AliasHandleCUSeeMeIn(la, pip, original_address);
|
|
/* If NETBIOS Datagram, It should be alias address in UDP Data, too */
|
|
else if (ntohs(ud->uh_dport) == NETBIOS_DGM_PORT_NUMBER
|
|
|| ntohs(ud->uh_sport) == NETBIOS_DGM_PORT_NUMBER)
|
|
r = AliasHandleUdpNbt(la, pip, lnk, &original_address, ud->uh_dport);
|
|
else if (ntohs(ud->uh_dport) == NETBIOS_NS_PORT_NUMBER
|
|
|| ntohs(ud->uh_sport) == NETBIOS_NS_PORT_NUMBER)
|
|
r = AliasHandleUdpNbtNS(la, pip, lnk, &alias_address, &alias_port,
|
|
&original_address, &ud->uh_dport);
|
|
|
|
/* If UDP checksum is not zero, then adjust since destination port */
|
|
/* is being unaliased and destination address is being altered. */
|
|
if (ud->uh_sum != 0) {
|
|
accumulate = alias_port;
|
|
accumulate -= ud->uh_dport;
|
|
accumulate += twowords(&alias_address);
|
|
accumulate -= twowords(&original_address);
|
|
ADJUST_CHECKSUM(accumulate, ud->uh_sum);
|
|
}
|
|
/* Restore original IP address */
|
|
DifferentialChecksum(&pip->ip_sum,
|
|
&original_address, &pip->ip_dst, 2);
|
|
pip->ip_dst = original_address;
|
|
|
|
/*
|
|
* If we cannot figure out the packet, ignore it.
|
|
*/
|
|
if (r < 0)
|
|
return (PKT_ALIAS_IGNORED);
|
|
else
|
|
return (PKT_ALIAS_OK);
|
|
}
|
|
return (PKT_ALIAS_IGNORED);
|
|
}
|
|
|
|
static int
|
|
UdpAliasOut(struct libalias *la, struct ip *pip, int create)
|
|
{
|
|
struct udphdr *ud;
|
|
struct alias_link *lnk;
|
|
|
|
/* Return if proxy-only mode is enabled */
|
|
if (la->packetAliasMode & PKT_ALIAS_PROXY_ONLY)
|
|
return (PKT_ALIAS_OK);
|
|
|
|
ud = (struct udphdr *)((char *)pip + (pip->ip_hl << 2));
|
|
|
|
lnk = FindUdpTcpOut(la, pip->ip_src, pip->ip_dst,
|
|
ud->uh_sport, ud->uh_dport,
|
|
IPPROTO_UDP, create);
|
|
if (lnk != NULL) {
|
|
u_short alias_port;
|
|
struct in_addr alias_address;
|
|
|
|
alias_address = GetAliasAddress(lnk);
|
|
alias_port = GetAliasPort(lnk);
|
|
|
|
/* Special processing for IP encoding protocols */
|
|
if (ntohs(ud->uh_dport) == CUSEEME_PORT_NUMBER)
|
|
AliasHandleCUSeeMeOut(la, pip, lnk);
|
|
/* If NETBIOS Datagram, It should be alias address in UDP Data, too */
|
|
else if (ntohs(ud->uh_dport) == NETBIOS_DGM_PORT_NUMBER
|
|
|| ntohs(ud->uh_sport) == NETBIOS_DGM_PORT_NUMBER)
|
|
AliasHandleUdpNbt(la, pip, lnk, &alias_address, alias_port);
|
|
else if (ntohs(ud->uh_dport) == NETBIOS_NS_PORT_NUMBER
|
|
|| ntohs(ud->uh_sport) == NETBIOS_NS_PORT_NUMBER)
|
|
AliasHandleUdpNbtNS(la, pip, lnk, &pip->ip_src, &ud->uh_sport,
|
|
&alias_address, &alias_port);
|
|
/*
|
|
* We don't know in advance what TID the TFTP server will choose,
|
|
* so we create a wilcard link (destination port is unspecified)
|
|
* that will match any TID from a given destination.
|
|
*/
|
|
else if (ntohs(ud->uh_dport) == TFTP_PORT_NUMBER)
|
|
FindRtspOut(la, pip->ip_src, pip->ip_dst,
|
|
ud->uh_sport, alias_port, IPPROTO_UDP);
|
|
|
|
/* If UDP checksum is not zero, adjust since source port is */
|
|
/* being aliased and source address is being altered */
|
|
if (ud->uh_sum != 0) {
|
|
int accumulate;
|
|
|
|
accumulate = ud->uh_sport;
|
|
accumulate -= alias_port;
|
|
accumulate += twowords(&pip->ip_src);
|
|
accumulate -= twowords(&alias_address);
|
|
ADJUST_CHECKSUM(accumulate, ud->uh_sum);
|
|
}
|
|
/* Put alias port in UDP header */
|
|
ud->uh_sport = alias_port;
|
|
|
|
/* Change source address */
|
|
DifferentialChecksum(&pip->ip_sum,
|
|
&alias_address, &pip->ip_src, 2);
|
|
pip->ip_src = alias_address;
|
|
|
|
return (PKT_ALIAS_OK);
|
|
}
|
|
return (PKT_ALIAS_IGNORED);
|
|
}
|
|
|
|
|
|
|
|
static int
|
|
TcpAliasIn(struct libalias *la, struct ip *pip)
|
|
{
|
|
struct tcphdr *tc;
|
|
struct alias_link *lnk;
|
|
|
|
tc = (struct tcphdr *)((char *)pip + (pip->ip_hl << 2));
|
|
|
|
lnk = FindUdpTcpIn(la, pip->ip_src, pip->ip_dst,
|
|
tc->th_sport, tc->th_dport,
|
|
IPPROTO_TCP,
|
|
!(la->packetAliasMode & PKT_ALIAS_PROXY_ONLY));
|
|
if (lnk != NULL) {
|
|
struct in_addr alias_address;
|
|
struct in_addr original_address;
|
|
struct in_addr proxy_address;
|
|
u_short alias_port;
|
|
u_short proxy_port;
|
|
int accumulate;
|
|
|
|
/* Special processing for IP encoding protocols */
|
|
if (ntohs(tc->th_dport) == PPTP_CONTROL_PORT_NUMBER
|
|
|| ntohs(tc->th_sport) == PPTP_CONTROL_PORT_NUMBER)
|
|
AliasHandlePptpIn(la, pip, lnk);
|
|
else if (la->skinnyPort != 0 && (ntohs(tc->th_dport) == la->skinnyPort
|
|
|| ntohs(tc->th_sport) == la->skinnyPort))
|
|
AliasHandleSkinny(la, pip, lnk);
|
|
|
|
alias_address = GetAliasAddress(lnk);
|
|
original_address = GetOriginalAddress(lnk);
|
|
proxy_address = GetProxyAddress(lnk);
|
|
alias_port = tc->th_dport;
|
|
tc->th_dport = GetOriginalPort(lnk);
|
|
proxy_port = GetProxyPort(lnk);
|
|
|
|
/* Adjust TCP checksum since destination port is being unaliased */
|
|
/* and destination port is being altered. */
|
|
accumulate = alias_port;
|
|
accumulate -= tc->th_dport;
|
|
accumulate += twowords(&alias_address);
|
|
accumulate -= twowords(&original_address);
|
|
|
|
/* If this is a proxy, then modify the TCP source port and
|
|
checksum accumulation */
|
|
if (proxy_port != 0) {
|
|
accumulate += tc->th_sport;
|
|
tc->th_sport = proxy_port;
|
|
accumulate -= tc->th_sport;
|
|
accumulate += twowords(&pip->ip_src);
|
|
accumulate -= twowords(&proxy_address);
|
|
}
|
|
/* See if ACK number needs to be modified */
|
|
if (GetAckModified(lnk) == 1) {
|
|
int delta;
|
|
|
|
delta = GetDeltaAckIn(pip, lnk);
|
|
if (delta != 0) {
|
|
accumulate += twowords(&tc->th_ack);
|
|
tc->th_ack = htonl(ntohl(tc->th_ack) - delta);
|
|
accumulate -= twowords(&tc->th_ack);
|
|
}
|
|
}
|
|
ADJUST_CHECKSUM(accumulate, tc->th_sum);
|
|
|
|
/* Restore original IP address */
|
|
accumulate = twowords(&pip->ip_dst);
|
|
pip->ip_dst = original_address;
|
|
accumulate -= twowords(&pip->ip_dst);
|
|
|
|
/* If this is a transparent proxy packet, then modify the source
|
|
address */
|
|
if (proxy_address.s_addr != 0) {
|
|
accumulate += twowords(&pip->ip_src);
|
|
pip->ip_src = proxy_address;
|
|
accumulate -= twowords(&pip->ip_src);
|
|
}
|
|
ADJUST_CHECKSUM(accumulate, pip->ip_sum);
|
|
|
|
/* Monitor TCP connection state */
|
|
TcpMonitorIn(pip, lnk);
|
|
|
|
return (PKT_ALIAS_OK);
|
|
}
|
|
return (PKT_ALIAS_IGNORED);
|
|
}
|
|
|
|
static int
|
|
TcpAliasOut(struct libalias *la, struct ip *pip, int maxpacketsize, int create)
|
|
{
|
|
int proxy_type;
|
|
u_short dest_port;
|
|
u_short proxy_server_port;
|
|
struct in_addr dest_address;
|
|
struct in_addr proxy_server_address;
|
|
struct tcphdr *tc;
|
|
struct alias_link *lnk;
|
|
|
|
tc = (struct tcphdr *)((char *)pip + (pip->ip_hl << 2));
|
|
|
|
proxy_type = ProxyCheck(la, pip, &proxy_server_address, &proxy_server_port);
|
|
|
|
if (proxy_type == 0 && (la->packetAliasMode & PKT_ALIAS_PROXY_ONLY))
|
|
return (PKT_ALIAS_OK);
|
|
|
|
/* If this is a transparent proxy, save original destination,
|
|
then alter the destination and adjust checksums */
|
|
dest_port = tc->th_dport;
|
|
dest_address = pip->ip_dst;
|
|
if (proxy_type != 0) {
|
|
int accumulate;
|
|
|
|
accumulate = tc->th_dport;
|
|
tc->th_dport = proxy_server_port;
|
|
accumulate -= tc->th_dport;
|
|
accumulate += twowords(&pip->ip_dst);
|
|
accumulate -= twowords(&proxy_server_address);
|
|
ADJUST_CHECKSUM(accumulate, tc->th_sum);
|
|
|
|
accumulate = twowords(&pip->ip_dst);
|
|
pip->ip_dst = proxy_server_address;
|
|
accumulate -= twowords(&pip->ip_dst);
|
|
ADJUST_CHECKSUM(accumulate, pip->ip_sum);
|
|
}
|
|
lnk = FindUdpTcpOut(la, pip->ip_src, pip->ip_dst,
|
|
tc->th_sport, tc->th_dport,
|
|
IPPROTO_TCP, create);
|
|
if (lnk == NULL)
|
|
return (PKT_ALIAS_IGNORED);
|
|
if (lnk != NULL) {
|
|
u_short alias_port;
|
|
struct in_addr alias_address;
|
|
int accumulate;
|
|
|
|
/* Save original destination address, if this is a proxy packet.
|
|
Also modify packet to include destination encoding. This may
|
|
change the size of IP header. */
|
|
if (proxy_type != 0) {
|
|
SetProxyPort(lnk, dest_port);
|
|
SetProxyAddress(lnk, dest_address);
|
|
ProxyModify(la, lnk, pip, maxpacketsize, proxy_type);
|
|
tc = (struct tcphdr *)((char *)pip + (pip->ip_hl << 2));
|
|
}
|
|
/* Get alias address and port */
|
|
alias_port = GetAliasPort(lnk);
|
|
alias_address = GetAliasAddress(lnk);
|
|
|
|
/* Monitor TCP connection state */
|
|
TcpMonitorOut(pip, lnk);
|
|
|
|
/* Special processing for IP encoding protocols */
|
|
if (ntohs(tc->th_dport) == FTP_CONTROL_PORT_NUMBER
|
|
|| ntohs(tc->th_sport) == FTP_CONTROL_PORT_NUMBER)
|
|
AliasHandleFtpOut(la, pip, lnk, maxpacketsize);
|
|
else if (ntohs(tc->th_dport) == IRC_CONTROL_PORT_NUMBER_1
|
|
|| ntohs(tc->th_dport) == IRC_CONTROL_PORT_NUMBER_2)
|
|
AliasHandleIrcOut(la, pip, lnk, maxpacketsize);
|
|
else if (ntohs(tc->th_dport) == RTSP_CONTROL_PORT_NUMBER_1
|
|
|| ntohs(tc->th_sport) == RTSP_CONTROL_PORT_NUMBER_1
|
|
|| ntohs(tc->th_dport) == RTSP_CONTROL_PORT_NUMBER_2
|
|
|| ntohs(tc->th_sport) == RTSP_CONTROL_PORT_NUMBER_2)
|
|
AliasHandleRtspOut(la, pip, lnk, maxpacketsize);
|
|
else if (ntohs(tc->th_dport) == PPTP_CONTROL_PORT_NUMBER
|
|
|| ntohs(tc->th_sport) == PPTP_CONTROL_PORT_NUMBER)
|
|
AliasHandlePptpOut(la, pip, lnk);
|
|
else if (la->skinnyPort != 0 && (ntohs(tc->th_sport) == la->skinnyPort
|
|
|| ntohs(tc->th_dport) == la->skinnyPort))
|
|
AliasHandleSkinny(la, pip, lnk);
|
|
|
|
/* Adjust TCP checksum since source port is being aliased */
|
|
/* and source address is being altered */
|
|
accumulate = tc->th_sport;
|
|
tc->th_sport = alias_port;
|
|
accumulate -= tc->th_sport;
|
|
accumulate += twowords(&pip->ip_src);
|
|
accumulate -= twowords(&alias_address);
|
|
|
|
/* Modify sequence number if necessary */
|
|
if (GetAckModified(lnk) == 1) {
|
|
int delta;
|
|
|
|
delta = GetDeltaSeqOut(pip, lnk);
|
|
if (delta != 0) {
|
|
accumulate += twowords(&tc->th_seq);
|
|
tc->th_seq = htonl(ntohl(tc->th_seq) + delta);
|
|
accumulate -= twowords(&tc->th_seq);
|
|
}
|
|
}
|
|
ADJUST_CHECKSUM(accumulate, tc->th_sum);
|
|
|
|
/* Change source address */
|
|
accumulate = twowords(&pip->ip_src);
|
|
pip->ip_src = alias_address;
|
|
accumulate -= twowords(&pip->ip_src);
|
|
ADJUST_CHECKSUM(accumulate, pip->ip_sum);
|
|
|
|
return (PKT_ALIAS_OK);
|
|
}
|
|
return (PKT_ALIAS_IGNORED);
|
|
}
|
|
|
|
|
|
|
|
|
|
/* Fragment Handling
|
|
|
|
FragmentIn()
|
|
FragmentOut()
|
|
|
|
The packet aliasing module has a limited ability for handling IP
|
|
fragments. If the ICMP, TCP or UDP header is in the first fragment
|
|
received, then the ID number of the IP packet is saved, and other
|
|
fragments are identified according to their ID number and IP address
|
|
they were sent from. Pointers to unresolved fragments can also be
|
|
saved and recalled when a header fragment is seen.
|
|
*/
|
|
|
|
/* Local prototypes */
|
|
static int FragmentIn(struct libalias *, struct ip *);
|
|
static int FragmentOut(struct libalias *, struct ip *);
|
|
|
|
|
|
static int
|
|
FragmentIn(struct libalias *la, struct ip *pip)
|
|
{
|
|
struct alias_link *lnk;
|
|
|
|
lnk = FindFragmentIn2(la, pip->ip_src, pip->ip_dst, pip->ip_id);
|
|
if (lnk != NULL) {
|
|
struct in_addr original_address;
|
|
|
|
GetFragmentAddr(lnk, &original_address);
|
|
DifferentialChecksum(&pip->ip_sum,
|
|
&original_address, &pip->ip_dst, 2);
|
|
pip->ip_dst = original_address;
|
|
|
|
return (PKT_ALIAS_OK);
|
|
}
|
|
return (PKT_ALIAS_UNRESOLVED_FRAGMENT);
|
|
}
|
|
|
|
|
|
static int
|
|
FragmentOut(struct libalias *la, struct ip *pip)
|
|
{
|
|
struct in_addr alias_address;
|
|
|
|
alias_address = FindAliasAddress(la, pip->ip_src);
|
|
DifferentialChecksum(&pip->ip_sum,
|
|
&alias_address, &pip->ip_src, 2);
|
|
pip->ip_src = alias_address;
|
|
|
|
return (PKT_ALIAS_OK);
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
/* Outside World Access
|
|
|
|
PacketAliasSaveFragment()
|
|
PacketAliasGetFragment()
|
|
PacketAliasFragmentIn()
|
|
PacketAliasIn()
|
|
PacketAliasOut()
|
|
PacketUnaliasOut()
|
|
|
|
(prototypes in alias.h)
|
|
*/
|
|
|
|
|
|
int
|
|
LibAliasSaveFragment(struct libalias *la, char *ptr)
|
|
{
|
|
int iresult;
|
|
struct alias_link *lnk;
|
|
struct ip *pip;
|
|
|
|
pip = (struct ip *)ptr;
|
|
lnk = AddFragmentPtrLink(la, pip->ip_src, pip->ip_id);
|
|
iresult = PKT_ALIAS_ERROR;
|
|
if (lnk != NULL) {
|
|
SetFragmentPtr(lnk, ptr);
|
|
iresult = PKT_ALIAS_OK;
|
|
}
|
|
return (iresult);
|
|
}
|
|
|
|
|
|
char *
|
|
LibAliasGetFragment(struct libalias *la, char *ptr)
|
|
{
|
|
struct alias_link *lnk;
|
|
char *fptr;
|
|
struct ip *pip;
|
|
|
|
pip = (struct ip *)ptr;
|
|
lnk = FindFragmentPtr(la, pip->ip_src, pip->ip_id);
|
|
if (lnk != NULL) {
|
|
GetFragmentPtr(lnk, &fptr);
|
|
SetFragmentPtr(lnk, NULL);
|
|
SetExpire(lnk, 0); /* Deletes link */
|
|
|
|
return (fptr);
|
|
} else {
|
|
return (NULL);
|
|
}
|
|
}
|
|
|
|
|
|
void
|
|
LibAliasFragmentIn(struct libalias *la, 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;
|
|
|
|
(void)la;
|
|
pip = (struct ip *)ptr;
|
|
fpip = (struct ip *)ptr_fragment;
|
|
|
|
DifferentialChecksum(&fpip->ip_sum,
|
|
&pip->ip_dst, &fpip->ip_dst, 2);
|
|
fpip->ip_dst = pip->ip_dst;
|
|
}
|
|
|
|
|
|
int
|
|
LibAliasIn(struct libalias *la, char *ptr, int maxpacketsize)
|
|
{
|
|
struct in_addr alias_addr;
|
|
struct ip *pip;
|
|
int iresult;
|
|
|
|
if (la->packetAliasMode & PKT_ALIAS_REVERSE) {
|
|
la->packetAliasMode &= ~PKT_ALIAS_REVERSE;
|
|
iresult = PacketAliasOut(ptr, maxpacketsize);
|
|
la->packetAliasMode |= PKT_ALIAS_REVERSE;
|
|
return (iresult);
|
|
}
|
|
HouseKeeping(la);
|
|
ClearCheckNewLink(la);
|
|
pip = (struct ip *)ptr;
|
|
alias_addr = pip->ip_dst;
|
|
|
|
/* Defense against mangled packets */
|
|
if (ntohs(pip->ip_len) > maxpacketsize
|
|
|| (pip->ip_hl << 2) > maxpacketsize)
|
|
return (PKT_ALIAS_IGNORED);
|
|
|
|
iresult = PKT_ALIAS_IGNORED;
|
|
if ((ntohs(pip->ip_off) & IP_OFFMASK) == 0) {
|
|
switch (pip->ip_p) {
|
|
case IPPROTO_ICMP:
|
|
iresult = IcmpAliasIn(la, pip);
|
|
break;
|
|
case IPPROTO_UDP:
|
|
iresult = UdpAliasIn(la, pip);
|
|
break;
|
|
case IPPROTO_TCP:
|
|
iresult = TcpAliasIn(la, pip);
|
|
break;
|
|
case IPPROTO_GRE:
|
|
if (la->packetAliasMode & PKT_ALIAS_PROXY_ONLY ||
|
|
AliasHandlePptpGreIn(la, pip) == 0)
|
|
iresult = PKT_ALIAS_OK;
|
|
else
|
|
iresult = ProtoAliasIn(la, pip);
|
|
break;
|
|
default:
|
|
iresult = ProtoAliasIn(la, pip);
|
|
break;
|
|
}
|
|
|
|
if (ntohs(pip->ip_off) & IP_MF) {
|
|
struct alias_link *lnk;
|
|
|
|
lnk = FindFragmentIn1(la, pip->ip_src, alias_addr, pip->ip_id);
|
|
if (lnk != NULL) {
|
|
iresult = PKT_ALIAS_FOUND_HEADER_FRAGMENT;
|
|
SetFragmentAddr(lnk, pip->ip_dst);
|
|
} else {
|
|
iresult = PKT_ALIAS_ERROR;
|
|
}
|
|
}
|
|
} else {
|
|
iresult = FragmentIn(la, pip);
|
|
}
|
|
|
|
return (iresult);
|
|
}
|
|
|
|
|
|
|
|
/* Unregistered address ranges */
|
|
|
|
/* 10.0.0.0 -> 10.255.255.255 */
|
|
#define UNREG_ADDR_A_LOWER 0x0a000000
|
|
#define UNREG_ADDR_A_UPPER 0x0affffff
|
|
|
|
/* 172.16.0.0 -> 172.31.255.255 */
|
|
#define UNREG_ADDR_B_LOWER 0xac100000
|
|
#define UNREG_ADDR_B_UPPER 0xac1fffff
|
|
|
|
/* 192.168.0.0 -> 192.168.255.255 */
|
|
#define UNREG_ADDR_C_LOWER 0xc0a80000
|
|
#define UNREG_ADDR_C_UPPER 0xc0a8ffff
|
|
|
|
int
|
|
LibAliasOut(struct libalias *la, char *ptr, /* valid IP packet */
|
|
int maxpacketsize /* How much the packet data may grow (FTP
|
|
* and IRC inline changes) */
|
|
)
|
|
{
|
|
return (LibAliasOutTry(la, ptr, maxpacketsize, 1));
|
|
}
|
|
|
|
int
|
|
LibAliasOutTry(struct libalias *la, char *ptr, /* valid IP packet */
|
|
int maxpacketsize, /* How much the packet data may grow (FTP
|
|
* and IRC inline changes) */
|
|
int create /* Create new entries ? */
|
|
)
|
|
{
|
|
int iresult;
|
|
struct in_addr addr_save;
|
|
struct ip *pip;
|
|
|
|
if (la->packetAliasMode & PKT_ALIAS_REVERSE) {
|
|
la->packetAliasMode &= ~PKT_ALIAS_REVERSE;
|
|
iresult = PacketAliasIn(ptr, maxpacketsize);
|
|
la->packetAliasMode |= PKT_ALIAS_REVERSE;
|
|
return (iresult);
|
|
}
|
|
HouseKeeping(la);
|
|
ClearCheckNewLink(la);
|
|
pip = (struct ip *)ptr;
|
|
|
|
/* Defense against mangled packets */
|
|
if (ntohs(pip->ip_len) > maxpacketsize
|
|
|| (pip->ip_hl << 2) > maxpacketsize)
|
|
return (PKT_ALIAS_IGNORED);
|
|
|
|
addr_save = GetDefaultAliasAddress(la);
|
|
if (la->packetAliasMode & PKT_ALIAS_UNREGISTERED_ONLY) {
|
|
u_long addr;
|
|
int iclass;
|
|
|
|
iclass = 0;
|
|
addr = ntohl(pip->ip_src.s_addr);
|
|
if (addr >= UNREG_ADDR_C_LOWER && addr <= UNREG_ADDR_C_UPPER)
|
|
iclass = 3;
|
|
else if (addr >= UNREG_ADDR_B_LOWER && addr <= UNREG_ADDR_B_UPPER)
|
|
iclass = 2;
|
|
else if (addr >= UNREG_ADDR_A_LOWER && addr <= UNREG_ADDR_A_UPPER)
|
|
iclass = 1;
|
|
|
|
if (iclass == 0) {
|
|
SetDefaultAliasAddress(la, pip->ip_src);
|
|
}
|
|
} else if (la->packetAliasMode & PKT_ALIAS_PROXY_ONLY) {
|
|
SetDefaultAliasAddress(la, pip->ip_src);
|
|
}
|
|
iresult = PKT_ALIAS_IGNORED;
|
|
if ((ntohs(pip->ip_off) & IP_OFFMASK) == 0) {
|
|
switch (pip->ip_p) {
|
|
case IPPROTO_ICMP:
|
|
iresult = IcmpAliasOut(la, pip, create);
|
|
break;
|
|
case IPPROTO_UDP:
|
|
iresult = UdpAliasOut(la, pip, create);
|
|
break;
|
|
case IPPROTO_TCP:
|
|
iresult = TcpAliasOut(la, pip, maxpacketsize, create);
|
|
break;
|
|
case IPPROTO_GRE:
|
|
if (AliasHandlePptpGreOut(la, pip) == 0)
|
|
iresult = PKT_ALIAS_OK;
|
|
else
|
|
iresult = ProtoAliasOut(la, pip, create);
|
|
break;
|
|
default:
|
|
iresult = ProtoAliasOut(la, pip, create);
|
|
break;
|
|
}
|
|
} else {
|
|
iresult = FragmentOut(la, pip);
|
|
}
|
|
|
|
SetDefaultAliasAddress(la, addr_save);
|
|
return (iresult);
|
|
}
|
|
|
|
int
|
|
LibAliasUnaliasOut(struct libalias *la, char *ptr, /* valid IP packet */
|
|
int maxpacketsize /* for error checking */
|
|
)
|
|
{
|
|
struct ip *pip;
|
|
struct icmp *ic;
|
|
struct udphdr *ud;
|
|
struct tcphdr *tc;
|
|
struct alias_link *lnk;
|
|
int iresult = PKT_ALIAS_IGNORED;
|
|
|
|
pip = (struct ip *)ptr;
|
|
|
|
/* Defense against mangled packets */
|
|
if (ntohs(pip->ip_len) > maxpacketsize
|
|
|| (pip->ip_hl << 2) > maxpacketsize)
|
|
return (iresult);
|
|
|
|
ud = (struct udphdr *)((char *)pip + (pip->ip_hl << 2));
|
|
tc = (struct tcphdr *)ud;
|
|
ic = (struct icmp *)ud;
|
|
|
|
/* Find a link */
|
|
if (pip->ip_p == IPPROTO_UDP)
|
|
lnk = FindUdpTcpIn(la, pip->ip_dst, pip->ip_src,
|
|
ud->uh_dport, ud->uh_sport,
|
|
IPPROTO_UDP, 0);
|
|
else if (pip->ip_p == IPPROTO_TCP)
|
|
lnk = FindUdpTcpIn(la, pip->ip_dst, pip->ip_src,
|
|
tc->th_dport, tc->th_sport,
|
|
IPPROTO_TCP, 0);
|
|
else if (pip->ip_p == IPPROTO_ICMP)
|
|
lnk = FindIcmpIn(la, pip->ip_dst, pip->ip_src, ic->icmp_id, 0);
|
|
else
|
|
lnk = NULL;
|
|
|
|
/* Change it from an aliased packet to an unaliased packet */
|
|
if (lnk != NULL) {
|
|
if (pip->ip_p == IPPROTO_UDP || pip->ip_p == IPPROTO_TCP) {
|
|
int accumulate;
|
|
struct in_addr original_address;
|
|
u_short original_port;
|
|
|
|
original_address = GetOriginalAddress(lnk);
|
|
original_port = GetOriginalPort(lnk);
|
|
|
|
/* Adjust TCP/UDP checksum */
|
|
accumulate = twowords(&pip->ip_src);
|
|
accumulate -= twowords(&original_address);
|
|
|
|
if (pip->ip_p == IPPROTO_UDP) {
|
|
accumulate += ud->uh_sport;
|
|
accumulate -= original_port;
|
|
ADJUST_CHECKSUM(accumulate, ud->uh_sum);
|
|
} else {
|
|
accumulate += tc->th_sport;
|
|
accumulate -= original_port;
|
|
ADJUST_CHECKSUM(accumulate, tc->th_sum);
|
|
}
|
|
|
|
/* Adjust IP checksum */
|
|
DifferentialChecksum(&pip->ip_sum,
|
|
&original_address, &pip->ip_src, 2);
|
|
|
|
/* Un-alias source address and port number */
|
|
pip->ip_src = original_address;
|
|
if (pip->ip_p == IPPROTO_UDP)
|
|
ud->uh_sport = original_port;
|
|
else
|
|
tc->th_sport = original_port;
|
|
|
|
iresult = PKT_ALIAS_OK;
|
|
|
|
} else if (pip->ip_p == IPPROTO_ICMP) {
|
|
|
|
int accumulate;
|
|
struct in_addr original_address;
|
|
u_short original_id;
|
|
|
|
original_address = GetOriginalAddress(lnk);
|
|
original_id = GetOriginalPort(lnk);
|
|
|
|
/* Adjust ICMP checksum */
|
|
accumulate = twowords(&pip->ip_src);
|
|
accumulate -= twowords(&original_address);
|
|
accumulate += ic->icmp_id;
|
|
accumulate -= original_id;
|
|
ADJUST_CHECKSUM(accumulate, ic->icmp_cksum);
|
|
|
|
/* Adjust IP checksum */
|
|
DifferentialChecksum(&pip->ip_sum,
|
|
&original_address, &pip->ip_src, 2);
|
|
|
|
/* Un-alias source address and port number */
|
|
pip->ip_src = original_address;
|
|
ic->icmp_id = original_id;
|
|
|
|
iresult = PKT_ALIAS_OK;
|
|
}
|
|
}
|
|
return (iresult);
|
|
|
|
}
|