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freebsd-dev/sys/netinet/libalias/alias_db.h
Lutz Donnerhacke 25392fac94 libalias: Fix splay comparsion bug 
Comparing elements in a tree requires transitiviy.  If a < b and b < c
then a must be smaller than c.  This way the tree elements are always
pairwise comparable.

Tristate comparsion functions returning values lower, equal, or
greater than zero, are usually implemented by a simple subtraction of
the operands.  If the size of the operands are equal to the size of
the result, integer modular arithmetics kick in and violates the
transitivity.

Example:
Working on byte with 0, 120, and 240. Now computing the differences:
  120 -   0 = 120
  240 - 120 = 120
  240 -   0 = -16

MFC after:	3 days
2021-07-03 00:31:53 +02:00

444 lines
14 KiB
C
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/*-
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* 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
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*
Alias_db.c encapsulates all data structures used for storing
packet aliasing data. Other parts of the aliasing software
access data through functions provided in this file.
Data storage is based on the notion of a "link", which is
established for ICMP echo/reply packets, UDP datagrams and
TCP stream connections. A link stores the original source
and destination addresses. For UDP and TCP, it also stores
source and destination port numbers, as well as an alias
port number. Links are also used to store information about
fragments.
There is a facility for sweeping through and deleting old
links as new packets are sent through. A simple timeout is
used for ICMP and UDP links. TCP links are left alone unless
there is an incomplete connection, in which case the link
can be deleted after a certain amount of time.
Initial version: August, 1996 (cjm)
Version 1.4: September 16, 1996 (cjm)
Facility for handling incoming links added.
Version 1.6: September 18, 1996 (cjm)
ICMP data handling simplified.
Version 1.7: January 9, 1997 (cjm)
Fragment handling simplified.
Saves pointers for unresolved fragments.
Permits links for unspecified remote ports
or unspecified remote addresses.
Fixed bug which did not properly zero port
table entries after a link was deleted.
Cleaned up some obsolete comments.
Version 1.8: January 14, 1997 (cjm)
Fixed data type error in StartPoint().
(This error did not exist prior to v1.7
and was discovered and fixed by Ari Suutari)
Version 1.9: February 1, 1997
Optionally, connections initiated from packet aliasing host
machine will will not have their port number aliased unless it
conflicts with an aliasing port already being used. (cjm)
All options earlier being #ifdef'ed are now available through
a new interface, SetPacketAliasMode(). This allows run time
control (which is now available in PPP+pktAlias through the
'alias' keyword). (ee)
Added ability to create an alias port without
either destination address or port specified.
port type = ALIAS_PORT_UNKNOWN_DEST_ALL (ee)
Removed K&R style function headers
and general cleanup. (ee)
Added packetAliasMode to replace compiler #defines's (ee)
Allocates sockets for partially specified
ports if ALIAS_USE_SOCKETS defined. (cjm)
Version 2.0: March, 1997
SetAliasAddress() will now clean up alias links
if the aliasing address is changed. (cjm)
PacketAliasPermanentLink() function added to support permanent
links. (J. Fortes suggested the need for this.)
Examples:
(192.168.0.1, port 23) <-> alias port 6002, unknown dest addr/port
(192.168.0.2, port 21) <-> alias port 3604, known dest addr
unknown dest port
These permanent links allow for incoming connections to
machines on the local network. They can be given with a
user-chosen amount of specificity, with increasing specificity
meaning more security. (cjm)
Quite a bit of rework to the basic engine. The portTable[]
array, which kept track of which ports were in use was replaced
by a table/linked list structure. (cjm)
SetExpire() function added. (cjm)
DeleteLink() no longer frees memory association with a pointer
to a fragment (this bug was first recognized by E. Eklund in
v1.9).
Version 2.1: May, 1997 (cjm)
Packet aliasing engine reworked so that it can handle
multiple external addresses rather than just a single
host address.
PacketAliasRedirectPort() and PacketAliasRedirectAddr()
added to the API. The first function is a more generalized
version of PacketAliasPermanentLink(). The second function
implements static network address translation.
Version 3.2: July, 2000 (salander and satoh)
Added FindNewPortGroup to get contiguous range of port values.
Added QueryUdpTcpIn and QueryUdpTcpOut to look for an aliasing
link but not actually add one.
Added FindRtspOut, which is closely derived from FindUdpTcpOut,
except that the alias port (from FindNewPortGroup) is provided
as input.
See HISTORY file for additional revisions.
*/
#ifndef _ALIAS_DB_H_
#define _ALIAS_DB_H_
/*
Constants (note: constants are also defined
near relevant functions or structs)
*/
/* Timeouts (in seconds) for different link types */
#define ICMP_EXPIRE_TIME 60
#define UDP_EXPIRE_TIME 60
#define PROTO_EXPIRE_TIME 60
#define FRAGMENT_ID_EXPIRE_TIME 10
#define FRAGMENT_PTR_EXPIRE_TIME 30
/* TCP link expire time for different cases */
/* When the link has been used and closed - minimal grace time to
allow ACKs and potential re-connect in FTP (XXX - is this allowed?) */
#ifndef TCP_EXPIRE_DEAD
#define TCP_EXPIRE_DEAD 10
#endif
/* When the link has been used and closed on one side - the other side
is allowed to still send data */
#ifndef TCP_EXPIRE_SINGLEDEAD
#define TCP_EXPIRE_SINGLEDEAD 90
#endif
/* When the link isn't yet up */
#ifndef TCP_EXPIRE_INITIAL
#define TCP_EXPIRE_INITIAL 300
#endif
/* When the link is up */
#ifndef TCP_EXPIRE_CONNECTED
#define TCP_EXPIRE_CONNECTED 86400
#endif
/* Dummy port number codes used for FindLinkIn/Out() and AddLink().
These constants can be anything except zero, which indicates an
unknown port number. */
#define NO_DEST_PORT 1
#define NO_SRC_PORT 1
/* Matches any/unknown address in FindLinkIn/Out() and AddLink(). */
static struct in_addr const ANY_ADDR = { INADDR_ANY };
/* Data Structures
The fundamental data structure used in this program is
"struct alias_link". Whenever a TCP connection is made,
a UDP datagram is sent out, or an ICMP echo request is made,
a link record is made (if it has not already been created).
The link record is identified by the source address/port
and the destination address/port. In the case of an ICMP
echo request, the source port is treated as being equivalent
with the 16-bit ID number of the ICMP packet.
The link record also can store some auxiliary data. For
TCP connections that have had sequence and acknowledgment
modifications, data space is available to track these changes.
A state field is used to keep track in changes to the TCP
connection state. ID numbers of fragments can also be
stored in the auxiliary space. Pointers to unresolved
fragments can also be stored.
The link records support two independent chainings. Lookup
tables for input and out tables hold the initial pointers
the link chains. On input, the lookup table indexes on alias
port and link type. On output, the lookup table indexes on
source address, destination address, source port, destination
port and link type.
*/
/* used to save changes to ACK/sequence numbers */
struct ack_data_record {
u_long ack_old;
u_long ack_new;
int delta;
int active;
};
/* Information about TCP connection */
struct tcp_state {
int in; /* State for outside -> inside */
int out; /* State for inside -> outside */
int index; /* Index to ACK data array */
/* Indicates whether ACK and sequence numbers been modified */
int ack_modified;
};
/* Number of distinct ACK number changes
* saved for a modified TCP stream */
#define N_LINK_TCP_DATA 3
struct tcp_dat {
struct tcp_state state;
struct ack_data_record ack[N_LINK_TCP_DATA];
/* Which firewall record is used for this hole? */
int fwhole;
};
/* LSNAT server pool (circular list) */
struct server {
struct in_addr addr;
u_short port;
struct server *next;
};
/* Main data structure */
struct alias_link {
struct libalias *la;
/* Address and port information */
struct in_addr src_addr;
struct in_addr dst_addr;
struct in_addr alias_addr;
struct in_addr proxy_addr;
u_short src_port;
u_short dst_port;
u_short alias_port;
u_short proxy_port;
struct server *server;
/* Type of link: TCP, UDP, ICMP, proto, frag */
int link_type;
/* values for link_type */
#define LINK_ICMP IPPROTO_ICMP
#define LINK_UDP IPPROTO_UDP
#define LINK_TCP IPPROTO_TCP
#define LINK_FRAGMENT_ID (IPPROTO_MAX + 1)
#define LINK_FRAGMENT_PTR (IPPROTO_MAX + 2)
#define LINK_ADDR (IPPROTO_MAX + 3)
#define LINK_PPTP (IPPROTO_MAX + 4)
int flags; /* indicates special characteristics */
int pflags; /* protocol-specific flags */
/* flag bits */
#define LINK_UNKNOWN_DEST_PORT 0x01
#define LINK_UNKNOWN_DEST_ADDR 0x02
#define LINK_PERMANENT 0x04
#define LINK_PARTIALLY_SPECIFIED 0x03 /* logical-or of first two bits */
#define LINK_UNFIREWALLED 0x08
int timestamp; /* Time link was last accessed */
#ifndef NO_USE_SOCKETS
int sockfd; /* socket descriptor */
#endif
/* Linked list of pointers for input and output lookup tables */
union {
struct {
SPLAY_ENTRY(alias_link) out;
LIST_ENTRY (alias_link) in;
} all;
struct {
LIST_ENTRY (alias_link) list;
} pptp;
};
struct {
TAILQ_ENTRY(alias_link) list;
int time; /* Expire time for link */
} expire;
/* Auxiliary data */
union {
char *frag_ptr;
struct in_addr frag_addr;
struct tcp_dat *tcp;
} data;
};
/* Clean up procedure. */
static void finishoff(void);
/* Internal utility routines (used only in alias_db.c)
Lookup table starting points:
StartPointIn() -- link table initial search point for
incoming packets
StartPointOut() -- link table initial search point for
outgoing packets
Miscellaneous:
SeqDiff() -- difference between two TCP sequences
ShowAliasStats() -- send alias statistics to a monitor file
*/
/* Local prototypes */
static struct group_in *
StartPointIn(struct libalias *, struct in_addr, u_short, int, int);
static int SeqDiff(u_long, u_long);
#ifndef NO_FW_PUNCH
/* Firewall control */
static void InitPunchFW(struct libalias *);
static void UninitPunchFW(struct libalias *);
static void ClearFWHole(struct alias_link *);
#endif
/* Log file control */
static void ShowAliasStats(struct libalias *);
static int InitPacketAliasLog(struct libalias *);
static void UninitPacketAliasLog(struct libalias *);
void SctpShowAliasStats(struct libalias *la);
/* Splay handling */
static inline int
cmp_out(struct alias_link *a, struct alias_link *b) {
int i = a->src_port - b->src_port;
if (i != 0) return (i);
if (a->src_addr.s_addr > b->src_addr.s_addr) return (1);
if (a->src_addr.s_addr < b->src_addr.s_addr) return (-1);
if (a->dst_addr.s_addr > b->dst_addr.s_addr) return (1);
if (a->dst_addr.s_addr < b->dst_addr.s_addr) return (-1);
i = a->dst_port - b->dst_port;
if (i != 0) return (i);
i = a->link_type - b->link_type;
return (i);
}
SPLAY_PROTOTYPE(splay_out, alias_link, all.out, cmp_out);
static inline int
cmp_in(struct group_in *a, struct group_in *b) {
int i = a->alias_port - b->alias_port;
if (i != 0) return (i);
i = a->link_type - b->link_type;
if (i != 0) return (i);
if (a->alias_addr.s_addr > b->alias_addr.s_addr) return (1);
if (a->alias_addr.s_addr < b->alias_addr.s_addr) return (-1);
return (0);
}
SPLAY_PROTOTYPE(splay_in, group_in, in, cmp_in);
/* Internal routines for finding, deleting and adding links
Port Allocation:
GetNewPort() -- find and reserve new alias port number
GetSocket() -- try to allocate a socket for a given port
Link creation and deletion:
CleanupAliasData() - remove all link chains from lookup table
CleanupLink() - look for a stale link
DeleteLink() - remove link
AddLink() - add link
ReLink() - change link
Link search:
FindLinkOut() - find link for outgoing packets
FindLinkIn() - find link for incoming packets
Port search:
FindNewPortGroup() - find an available group of ports
*/
/* Local prototypes */
static int GetNewPort(struct libalias *, struct alias_link *, int);
#ifndef NO_USE_SOCKETS
static u_short GetSocket(struct libalias *, u_short, int *, int);
#endif
static void CleanupAliasData(struct libalias *, int);
static void CleanupLink(struct libalias *, struct alias_link **, int);
static void DeleteLink(struct alias_link **, int);
static struct alias_link *
UseLink(struct libalias *, struct alias_link *);
static struct alias_link *
ReLink(struct alias_link *,
struct in_addr, struct in_addr, struct in_addr,
u_short, u_short, int, int, int);
static struct alias_link *
FindLinkOut(struct libalias *, struct in_addr, struct in_addr, u_short, u_short, int, int);
static struct alias_link *
FindLinkIn(struct libalias *, struct in_addr, struct in_addr, u_short, u_short, int, int);
static u_short _RandomPort(struct libalias *la);
#define GET_NEW_PORT_MAX_ATTEMPTS 20
#ifndef NO_FW_PUNCH
static void ClearAllFWHoles(struct libalias *la);
#define fw_setfield(la, field, num) \
do { \
(field)[(num) - la->fireWallBaseNum] = 1; \
} /*lint -save -e717 */ while(0)/* lint -restore */
#define fw_clrfield(la, field, num) \
do { \
(field)[(num) - la->fireWallBaseNum] = 0; \
} /*lint -save -e717 */ while(0)/* lint -restore */
#define fw_tstfield(la, field, num) ((field)[(num) - la->fireWallBaseNum])
#endif /* !NO_FW_PUNCH */
#endif /* _ALIAS_DB_H_ */
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