2 * SPDX-License-Identifier: BSD-2-Clause
4 * Copyright (c) 2001 Charles Mott <cm@linktel.net>
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 Alias_db.c encapsulates all data structures used for storing
31 packet aliasing data. Other parts of the aliasing software
32 access data through functions provided in this file.
34 Data storage is based on the notion of a "link", which is
35 established for ICMP echo/reply packets, UDP datagrams and
36 TCP stream connections. A link stores the original source
37 and destination addresses. For UDP and TCP, it also stores
38 source and destination port numbers, as well as an alias
39 port number. Links are also used to store information about
42 There is a facility for sweeping through and deleting old
43 links as new packets are sent through. A simple timeout is
44 used for ICMP and UDP links. TCP links are left alone unless
45 there is an incomplete connection, in which case the link
46 can be deleted after a certain amount of time.
48 Initial version: August, 1996 (cjm)
50 Version 1.4: September 16, 1996 (cjm)
51 Facility for handling incoming links added.
53 Version 1.6: September 18, 1996 (cjm)
54 ICMP data handling simplified.
56 Version 1.7: January 9, 1997 (cjm)
57 Fragment handling simplified.
58 Saves pointers for unresolved fragments.
59 Permits links for unspecified remote ports
60 or unspecified remote addresses.
61 Fixed bug which did not properly zero port
62 table entries after a link was deleted.
63 Cleaned up some obsolete comments.
65 Version 1.8: January 14, 1997 (cjm)
66 Fixed data type error in StartPoint().
67 (This error did not exist prior to v1.7
68 and was discovered and fixed by Ari Suutari)
70 Version 1.9: February 1, 1997
71 Optionally, connections initiated from packet aliasing host
72 machine will will not have their port number aliased unless it
73 conflicts with an aliasing port already being used. (cjm)
75 All options earlier being #ifdef'ed are now available through
76 a new interface, SetPacketAliasMode(). This allows run time
77 control (which is now available in PPP+pktAlias through the
78 'alias' keyword). (ee)
80 Added ability to create an alias port without
81 either destination address or port specified.
82 port type = ALIAS_PORT_UNKNOWN_DEST_ALL (ee)
84 Removed K&R style function headers
85 and general cleanup. (ee)
87 Added packetAliasMode to replace compiler #defines's (ee)
89 Allocates sockets for partially specified
90 ports if ALIAS_USE_SOCKETS defined. (cjm)
92 Version 2.0: March, 1997
93 SetAliasAddress() will now clean up alias links
94 if the aliasing address is changed. (cjm)
96 PacketAliasPermanentLink() function added to support permanent
97 links. (J. Fortes suggested the need for this.)
100 (192.168.0.1, port 23) <-> alias port 6002, unknown dest addr/port
102 (192.168.0.2, port 21) <-> alias port 3604, known dest addr
105 These permanent links allow for incoming connections to
106 machines on the local network. They can be given with a
107 user-chosen amount of specificity, with increasing specificity
108 meaning more security. (cjm)
110 Quite a bit of rework to the basic engine. The portTable[]
111 array, which kept track of which ports were in use was replaced
112 by a table/linked list structure. (cjm)
114 SetExpire() function added. (cjm)
116 DeleteLink() no longer frees memory association with a pointer
117 to a fragment (this bug was first recognized by E. Eklund in
120 Version 2.1: May, 1997 (cjm)
121 Packet aliasing engine reworked so that it can handle
122 multiple external addresses rather than just a single
125 PacketAliasRedirectPort() and PacketAliasRedirectAddr()
126 added to the API. The first function is a more generalized
127 version of PacketAliasPermanentLink(). The second function
128 implements static network address translation.
130 Version 3.2: July, 2000 (salander and satoh)
131 Added FindNewPortGroup to get contiguous range of port values.
133 Added QueryUdpTcpIn and QueryUdpTcpOut to look for an aliasing
134 link but not actually add one.
136 Added FindRtspOut, which is closely derived from FindUdpTcpOut,
137 except that the alias port (from FindNewPortGroup) is provided
140 See HISTORY file for additional revisions.
148 Constants (note: constants are also defined
149 near relevant functions or structs)
152 /* Timeouts (in seconds) for different link types */
153 #define ICMP_EXPIRE_TIME 60
154 #define UDP_EXPIRE_TIME 60
155 #define PROTO_EXPIRE_TIME 60
156 #define FRAGMENT_ID_EXPIRE_TIME 10
157 #define FRAGMENT_PTR_EXPIRE_TIME 30
159 /* TCP link expire time for different cases */
160 /* When the link has been used and closed - minimal grace time to
161 allow ACKs and potential re-connect in FTP (XXX - is this allowed?) */
162 #ifndef TCP_EXPIRE_DEAD
163 #define TCP_EXPIRE_DEAD 10
166 /* When the link has been used and closed on one side - the other side
167 is allowed to still send data */
168 #ifndef TCP_EXPIRE_SINGLEDEAD
169 #define TCP_EXPIRE_SINGLEDEAD 90
172 /* When the link isn't yet up */
173 #ifndef TCP_EXPIRE_INITIAL
174 #define TCP_EXPIRE_INITIAL 300
177 /* When the link is up */
178 #ifndef TCP_EXPIRE_CONNECTED
179 #define TCP_EXPIRE_CONNECTED 86400
182 /* Dummy port number codes used for FindLinkIn/Out() and AddLink().
183 These constants can be anything except zero, which indicates an
184 unknown port number. */
186 #define NO_DEST_PORT 1
187 #define NO_SRC_PORT 1
189 /* Matches any/unknown address in FindLinkIn/Out() and AddLink(). */
190 static struct in_addr const ANY_ADDR = { INADDR_ANY };
194 The fundamental data structure used in this program is
195 "struct alias_link". Whenever a TCP connection is made,
196 a UDP datagram is sent out, or an ICMP echo request is made,
197 a link record is made (if it has not already been created).
198 The link record is identified by the source address/port
199 and the destination address/port. In the case of an ICMP
200 echo request, the source port is treated as being equivalent
201 with the 16-bit ID number of the ICMP packet.
203 The link record also can store some auxiliary data. For
204 TCP connections that have had sequence and acknowledgment
205 modifications, data space is available to track these changes.
206 A state field is used to keep track in changes to the TCP
207 connection state. ID numbers of fragments can also be
208 stored in the auxiliary space. Pointers to unresolved
209 fragments can also be stored.
211 The link records support two independent chainings. Lookup
212 tables for input and out tables hold the initial pointers
213 the link chains. On input, the lookup table indexes on alias
214 port and link type. On output, the lookup table indexes on
215 source address, destination address, source port, destination
219 /* used to save changes to ACK/sequence numbers */
220 struct ack_data_record {
227 /* Information about TCP connection */
229 int in; /* State for outside -> inside */
230 int out; /* State for inside -> outside */
231 int index; /* Index to ACK data array */
232 /* Indicates whether ACK and sequence numbers been modified */
236 /* Number of distinct ACK number changes
237 * saved for a modified TCP stream */
238 #define N_LINK_TCP_DATA 3
240 struct tcp_state state;
241 struct ack_data_record ack[N_LINK_TCP_DATA];
242 /* Which firewall record is used for this hole? */
246 /* LSNAT server pool (circular list) */
253 /* Main data structure */
256 /* Address and port information */
257 struct in_addr src_addr;
258 struct in_addr dst_addr;
259 struct in_addr alias_addr;
260 struct in_addr proxy_addr;
265 struct server *server;
266 /* Type of link: TCP, UDP, ICMP, proto, frag */
268 /* values for link_type */
269 #define LINK_ICMP IPPROTO_ICMP
270 #define LINK_UDP IPPROTO_UDP
271 #define LINK_TCP IPPROTO_TCP
272 #define LINK_FRAGMENT_ID (IPPROTO_MAX + 1)
273 #define LINK_FRAGMENT_PTR (IPPROTO_MAX + 2)
274 #define LINK_ADDR (IPPROTO_MAX + 3)
275 #define LINK_PPTP (IPPROTO_MAX + 4)
277 int flags; /* indicates special characteristics */
278 int pflags; /* protocol-specific flags */
280 #define LINK_UNKNOWN_DEST_PORT 0x01
281 #define LINK_UNKNOWN_DEST_ADDR 0x02
282 #define LINK_PERMANENT 0x04
283 #define LINK_PARTIALLY_SPECIFIED 0x03 /* logical-or of first two bits */
284 #define LINK_UNFIREWALLED 0x08
286 int timestamp; /* Time link was last accessed */
287 #ifndef NO_USE_SOCKETS
288 int sockfd; /* socket descriptor */
290 /* Linked list of pointers for input and output lookup tables */
293 SPLAY_ENTRY(alias_link) out;
294 LIST_ENTRY (alias_link) in;
297 LIST_ENTRY (alias_link) list;
301 TAILQ_ENTRY(alias_link) list;
302 int time; /* Expire time for link */
307 struct in_addr frag_addr;
312 /* Clean up procedure. */
313 static void finishoff(void);
315 /* Internal utility routines (used only in alias_db.c)
317 Lookup table starting points:
318 StartPointIn() -- link table initial search point for
320 StartPointOut() -- link table initial search point for
324 SeqDiff() -- difference between two TCP sequences
325 ShowAliasStats() -- send alias statistics to a monitor file
328 /* Local prototypes */
329 static struct group_in *
330 StartPointIn(struct libalias *, struct in_addr, u_short, int, int);
331 static int SeqDiff(u_long, u_long);
334 /* Firewall control */
335 static void InitPunchFW(struct libalias *);
336 static void UninitPunchFW(struct libalias *);
337 static void ClearFWHole(struct alias_link *);
341 /* Log file control */
342 static void ShowAliasStats(struct libalias *);
343 static int InitPacketAliasLog(struct libalias *);
344 static void UninitPacketAliasLog(struct libalias *);
346 void SctpShowAliasStats(struct libalias *la);
351 cmp_out(struct alias_link *a, struct alias_link *b) {
352 int i = a->src_port - b->src_port;
353 if (i != 0) return (i);
354 if (a->src_addr.s_addr > b->src_addr.s_addr) return (1);
355 if (a->src_addr.s_addr < b->src_addr.s_addr) return (-1);
356 if (a->dst_addr.s_addr > b->dst_addr.s_addr) return (1);
357 if (a->dst_addr.s_addr < b->dst_addr.s_addr) return (-1);
358 i = a->dst_port - b->dst_port;
359 if (i != 0) return (i);
360 i = a->link_type - b->link_type;
363 SPLAY_PROTOTYPE(splay_out, alias_link, all.out, cmp_out);
366 cmp_in(struct group_in *a, struct group_in *b) {
367 int i = a->alias_port - b->alias_port;
368 if (i != 0) return (i);
369 i = a->link_type - b->link_type;
370 if (i != 0) return (i);
371 if (a->alias_addr.s_addr > b->alias_addr.s_addr) return (1);
372 if (a->alias_addr.s_addr < b->alias_addr.s_addr) return (-1);
375 SPLAY_PROTOTYPE(splay_in, group_in, in, cmp_in);
377 /* Internal routines for finding, deleting and adding links
380 GetNewPort() -- find and reserve new alias port number
381 GetSocket() -- try to allocate a socket for a given port
383 Link creation and deletion:
384 CleanupAliasData() - remove all link chains from lookup table
385 CleanupLink() - look for a stale link
386 DeleteLink() - remove link
388 ReLink() - change link
391 FindLinkOut() - find link for outgoing packets
392 FindLinkIn() - find link for incoming packets
395 FindNewPortGroup() - find an available group of ports
398 /* Local prototypes */
399 static int GetNewPort(struct libalias *, struct alias_link *, int);
400 #ifndef NO_USE_SOCKETS
401 static u_short GetSocket(struct libalias *, u_short, int *, int);
403 static void CleanupAliasData(struct libalias *, int);
404 static void CleanupLink(struct libalias *, struct alias_link **, int);
405 static void DeleteLink(struct alias_link **, int);
406 static struct alias_link *
407 UseLink(struct libalias *, struct alias_link *);
409 static struct alias_link *
410 ReLink(struct alias_link *,
411 struct in_addr, struct in_addr, struct in_addr,
412 u_short, u_short, int, int, int);
414 static struct alias_link *
415 FindLinkOut(struct libalias *, struct in_addr, struct in_addr, u_short, u_short, int, int);
417 static struct alias_link *
418 FindLinkIn(struct libalias *, struct in_addr, struct in_addr, u_short, u_short, int, int);
420 static u_short _RandomPort(struct libalias *la);
422 #define GET_NEW_PORT_MAX_ATTEMPTS 20
427 static void ClearAllFWHoles(struct libalias *la);
429 #define fw_setfield(la, field, num) \
431 (field)[(num) - la->fireWallBaseNum] = 1; \
432 } /*lint -save -e717 */ while(0)/* lint -restore */
434 #define fw_clrfield(la, field, num) \
436 (field)[(num) - la->fireWallBaseNum] = 0; \
437 } /*lint -save -e717 */ while(0)/* lint -restore */
439 #define fw_tstfield(la, field, num) ((field)[(num) - la->fireWallBaseNum])
441 #endif /* !NO_FW_PUNCH */
443 #endif /* _ALIAS_DB_H_ */