sap_tables.c revision 50479 
1/*
2 * Copyright (c) 1995 John Hay.  All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 * 3. All advertising materials mentioning features or use of this software
13 *    must display the following acknowledgement:
14 *	This product includes software developed by John Hay.
15 * 4. Neither the name of the author nor the names of any co-contributors
16 *    may be used to endorse or promote products derived from this software
17 *    without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY John Hay AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED.  IN NO EVENT SHALL John Hay OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 *
31 * $FreeBSD: head/usr.sbin/IPXrouted/sap_tables.c 50479 1999-08-28 01:35:59Z peter $
32 */
33
34#include "defs.h"
35#include <string.h>
36#include <stdlib.h>
37
38#define FIXLEN(s) { if ((s)->sa_len == 0) (s)->sa_len = sizeof (*(s));}
39
40sap_hash sap_head[SAPHASHSIZ];
41
42void
43sapinit(void)
44{
45	int i;
46
47	for (i=0; i<SAPHASHSIZ; i++)
48		sap_head[i].forw = sap_head[i].back =
49					(struct sap_entry *)&sap_head[i];
50}
51
52/*
53 * This hash use the first 14 letters of the ServName and the ServType
54 * to create a 32 bit hash value.
55 */
56int
57saphash(u_short ServType, char *ServName)
58{
59	int hsh, i;
60	char name[SERVNAMELEN];
61
62	bzero(name, SERVNAMELEN);
63	strncpy(name, ServName, SERVNAMELEN);
64	ServName = name;
65
66	hsh = 0;
67
68#define SMVAL   33
69
70	hsh = hsh * SMVAL + (ServType & 0xff);
71	hsh = hsh * SMVAL + (ServType >> 8);
72
73	for (i=0;i<14;i++) {
74		hsh = hsh * SMVAL + *ServName++;
75		ServName++;
76	}
77
78#undef SMVAL
79
80	return hsh;
81}
82
83/*
84 * Look for an exact match on ServType and ServName. It is
85 * mostly used by the function that process SAP RESPONSE packets.
86 *
87 * A hash is created and used to index into the hash table. Then
88 * that list is walk through searching for a match.
89 *
90 * If no match is found NULL is returned.
91 */
92struct sap_entry *
93sap_lookup(u_short ServType, char *ServName)
94{
95	register struct sap_entry *sap;
96	register struct sap_hash  *sh;
97	int hsh;
98
99	hsh = saphash(ServType, ServName);
100	sh = &sap_head[hsh & SAPHASHMASK];
101
102	for(sap = sh->forw; sap != (sap_entry *)sh; sap = sap->forw) {
103		if ((hsh == sap->hash) &&
104		    (ServType == sap->sap.ServType) &&
105		    (strncmp(ServName, sap->sap.ServName, SERVNAMELEN) == 0)) {
106			return sap;
107		}
108	}
109	return NULL;
110}
111
112/*
113 * This returns the nearest service of the specified type. If no
114 * suitable service is found or if that service is on the interface
115 * where the request came from, NULL is returned.
116 *
117 * When checking interfaces clones must be considered also.
118 *
119 * XXX TODO:
120 * Maybe we can use RIP tables to get the fastest service (ticks).
121 */
122struct sap_entry *
123sap_nearestserver(ushort ServType, struct interface *ifp)
124{
125	register struct sap_entry *sap;
126	register struct sap_entry *csap;
127	struct sap_hash  *sh;
128	register struct sap_entry *best = NULL;
129	register int besthops = HOPCNT_INFINITY;
130
131	sh = sap_head;
132
133	for (; sh < &sap_head[SAPHASHSIZ]; sh++)
134		for(sap = sh->forw; sap != (sap_entry *)sh; sap = sap->forw) {
135			if (ServType != sap->sap.ServType)
136				continue;
137
138			if (ntohs(sap->sap.hops) < besthops) {
139				best = sap;
140				besthops = ntohs(best->sap.hops);
141			}
142next:;
143		}
144	return best;
145}
146
147/*
148 * Add a entry to the SAP table.
149 *
150 * If the malloc fail, the entry will silently be thrown away.
151 */
152void
153sap_add(struct sap_info *si, struct sockaddr *from)
154{
155	register struct sap_entry *nsap;
156	register struct sap_hash *sh;
157
158	if (ntohs(si->hops) == HOPCNT_INFINITY)
159		return;
160
161	FIXLEN(from);
162	nsap = malloc(sizeof(struct sap_entry));
163	if (nsap == NULL)
164		return;
165
166	nsap->sap = *si;
167	nsap->source = *from;
168	nsap->clone = NULL;
169	nsap->ifp = if_ifwithnet(from);
170	nsap->state = RTS_CHANGED;
171	nsap->timer = 0;
172	nsap->hash = saphash(si->ServType, si->ServName);
173
174	sh = &sap_head[nsap->hash & SAPHASHMASK];
175
176	insque(nsap, sh);
177	TRACE_SAP_ACTION("ADD", nsap);
178}
179
180/*
181 * Change an existing SAP entry. If a clone exist for the old one,
182 * check if it is cheaper. If it is change tothe clone, otherwise
183 * delete all the clones.
184 */
185void
186sap_change(struct sap_entry *sap,
187           struct sap_info *si,
188           struct sockaddr *from)
189{
190	struct sap_entry *osap = NULL;
191
192	FIXLEN(from);
193	TRACE_SAP_ACTION("CHANGE FROM", sap);
194	/*
195	 * If the hopcount (metric) is HOPCNT_INFINITY (16) it means that
196	 * a service has gone down. We should keep it like that for 30
197	 * seconds, so that it will get broadcast and then change to a
198	 * clone if one exist.
199	 */
200	if (sap->clone && (ntohs(si->hops) != HOPCNT_INFINITY)) {
201		/*
202		 * There are three possibilities:
203		 * 1. The new path is cheaper than the old one.
204		 *      Free all the clones.
205		 *
206		 * 2. The new path is the same cost as the old ones.
207		 *      If it is on the list of clones remove it
208		 *      from the clone list and free it.
209		 *
210		 * 3. The new path is more expensive than the old one.
211		 *      Use the values of the first clone and take it
212		 *      out of the list, to be freed at the end.
213		 */
214		osap = sap->clone;
215		if (ntohs(osap->sap.hops) > ntohs(si->hops)) {
216			struct sap_entry *nsap;
217
218			while (osap) {
219				nsap = osap->clone;
220				TRACE_SAP_ACTION("DELETE", osap);
221				free(osap);
222				osap = nsap;
223			}
224			sap->clone = NULL;
225		} else if (ntohs(osap->sap.hops) == ntohs(si->hops)) {
226			struct sap_entry *psap;
227
228			psap = sap;
229			while (osap) {
230				if (equal(&osap->source, from)) {
231					psap->clone = osap->clone;
232					TRACE_SAP_ACTION("DELETE", osap);
233					free(osap);
234					osap = psap->clone;
235				} else {
236					psap = osap;
237					osap = osap->clone;
238				}
239			}
240		} else {
241		from = &osap->source;
242		si = &osap->sap;
243		sap->clone = osap->clone;
244		}
245	}
246	sap->sap = *si;
247	sap->source = *from;
248	sap->ifp = if_ifwithnet(from);
249	sap->state = RTS_CHANGED;
250	if (ntohs(si->hops) == HOPCNT_INFINITY)
251		sap->timer = EXPIRE_TIME;
252	else
253		sap->timer = 0;
254
255	if (osap) {
256		TRACE_SAP_ACTION("DELETE", osap);
257		free(osap);
258	}
259	TRACE_SAP_ACTION("CHANGE TO", sap);
260}
261
262/*
263 * Add a clone to the specified SAP entry. A clone is a different
264 * route to the same service. We must know about them when we use
265 * the split horizon algorithm.
266 *
267 * If the malloc fail, the entry will silently be thrown away.
268 */
269void
270sap_add_clone(struct sap_entry *sap,
271	      struct sap_info *clone,
272	      struct sockaddr *from)
273{
274	register struct sap_entry *nsap;
275	register struct sap_entry *csap;
276
277	if (ntohs(clone->hops) == HOPCNT_INFINITY)
278		return;
279
280	FIXLEN(from);
281	nsap = malloc(sizeof(struct sap_entry));
282	if (nsap == NULL)
283		return;
284
285	if (ftrace)
286		fprintf(ftrace, "CLONE ADD %04.4X %s.\n",
287			ntohs(clone->ServType),
288			clone->ServName);
289
290	nsap->sap = *clone;
291	nsap->source = *from;
292	nsap->clone = NULL;
293	nsap->ifp = if_ifwithnet(from);
294	nsap->state = RTS_CHANGED;
295	nsap->timer = 0;
296	nsap->hash = saphash(clone->ServType, clone->ServName);
297
298	csap = sap;
299	while (csap->clone)
300		csap = csap->clone;
301	csap->clone = nsap;
302	TRACE_SAP_ACTION("ADD CLONE", nsap);
303}
304
305/*
306 * Remove a SAP entry from the table and free the memory
307 * used by it.
308 *
309 * If the service have clone, do a sap_change to it and free
310 * the clone.
311 */
312void
313sap_delete(struct sap_entry *sap)
314{
315	if (sap->clone) {
316		sap_change(sap, &sap->clone->sap, &sap->clone->source);
317		return;
318	}
319	remque(sap);
320	TRACE_SAP_ACTION("DELETE", sap);
321	free(sap);
322}
323