FreeBSD/Linux Kernel Cross Reference
sys/netinet/ip_flow.c
1 /*-
2 * Copyright (c) 1998 The NetBSD Foundation, Inc.
3 * All rights reserved.
4 *
5 * This code is derived from software contributed to The NetBSD Foundation
6 * by the 3am Software Foundry ("3am"). It was developed by Matt Thomas.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. All advertising materials mentioning features or use of this software
17 * must display the following acknowledgement:
18 * This product includes software developed by the NetBSD
19 * Foundation, Inc. and its contributors.
20 * 4. Neither the name of The NetBSD Foundation nor the names of its
21 * contributors may be used to endorse or promote products derived
22 * from this software without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
25 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
26 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
27 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
28 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
29 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
30 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
31 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
32 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
33 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
34 * POSSIBILITY OF SUCH DAMAGE.
35 *
36 * $FreeBSD$
37 */
38
39 #include <sys/param.h>
40 #include <sys/systm.h>
41 #include <sys/malloc.h>
42 #include <sys/mbuf.h>
43 #include <sys/protosw.h>
44 #include <sys/socket.h>
45 #include <sys/kernel.h>
46
47 #include <sys/sysctl.h>
48
49 #include <net/if.h>
50 #include <net/route.h>
51
52 #include <netinet/in.h>
53 #include <netinet/in_systm.h>
54 #include <netinet/ip.h>
55 #include <netinet/in_var.h>
56 #include <netinet/ip_var.h>
57 #include <netinet/ip_flow.h>
58
59 #define IPFLOW_TIMER (5 * PR_SLOWHZ)
60 #define IPFLOW_HASHBITS 6 /* should not be a multiple of 8 */
61 #define IPFLOW_HASHSIZE (1 << IPFLOW_HASHBITS)
62 static LIST_HEAD(ipflowhead, ipflow) ipflows[IPFLOW_HASHSIZE];
63 static int ipflow_inuse;
64 #define IPFLOW_MAX 256
65
66 static int ipflow_active = 0;
67 SYSCTL_INT(_net_inet_ip, IPCTL_FASTFORWARDING, fastforwarding, CTLFLAG_RW,
68 &ipflow_active, 0, "Enable flow-based IP forwarding");
69
70 static MALLOC_DEFINE(M_IPFLOW, "ip_flow", "IP flow");
71
72 static unsigned
73 ipflow_hash(
74 struct in_addr dst,
75 struct in_addr src,
76 unsigned tos)
77 {
78 unsigned hash = tos;
79 int idx;
80 for (idx = 0; idx < 32; idx += IPFLOW_HASHBITS)
81 hash += (dst.s_addr >> (32 - idx)) + (src.s_addr >> idx);
82 return hash & (IPFLOW_HASHSIZE-1);
83 }
84
85 static struct ipflow *
86 ipflow_lookup(
87 const struct ip *ip)
88 {
89 unsigned hash;
90 struct ipflow *ipf;
91
92 hash = ipflow_hash(ip->ip_dst, ip->ip_src, ip->ip_tos);
93
94 ipf = LIST_FIRST(&ipflows[hash]);
95 while (ipf != NULL) {
96 if (ip->ip_dst.s_addr == ipf->ipf_dst.s_addr
97 && ip->ip_src.s_addr == ipf->ipf_src.s_addr
98 && ip->ip_tos == ipf->ipf_tos)
99 break;
100 ipf = LIST_NEXT(ipf, ipf_next);
101 }
102 return ipf;
103 }
104
105 int
106 ipflow_fastforward(
107 struct mbuf *m)
108 {
109 struct ip *ip;
110 struct ipflow *ipf;
111 struct rtentry *rt;
112 struct sockaddr *dst;
113 int error;
114
115 /*
116 * Are we forwarding packets? Big enough for an IP packet?
117 */
118 if (!ipforwarding || !ipflow_active || m->m_len < sizeof(struct ip))
119 return 0;
120 /*
121 * IP header with no option and valid version and length
122 */
123 ip = mtod(m, struct ip *);
124 if (ip->ip_v != IPVERSION || ip->ip_hl != (sizeof(struct ip) >> 2)
125 || ntohs(ip->ip_len) > m->m_pkthdr.len)
126 return 0;
127 /*
128 * Find a flow.
129 */
130 if ((ipf = ipflow_lookup(ip)) == NULL)
131 return 0;
132
133 /*
134 * Route and interface still up?
135 */
136 rt = ipf->ipf_ro.ro_rt;
137 if ((rt->rt_flags & RTF_UP) == 0 || (rt->rt_ifp->if_flags & IFF_UP) == 0)
138 return 0;
139
140 /*
141 * Packet size OK? TTL?
142 */
143 if (m->m_pkthdr.len > rt->rt_ifp->if_mtu || ip->ip_ttl <= IPTTLDEC)
144 return 0;
145
146 /*
147 * Everything checks out and so we can forward this packet.
148 * Modify the TTL and incrementally change the checksum.
149 */
150 ip->ip_ttl -= IPTTLDEC;
151 if (ip->ip_sum >= htons(0xffff - (IPTTLDEC << 8))) {
152 ip->ip_sum += htons(IPTTLDEC << 8) + 1;
153 } else {
154 ip->ip_sum += htons(IPTTLDEC << 8);
155 }
156
157 /*
158 * Send the packet on its way. All we can get back is ENOBUFS
159 */
160 ipf->ipf_uses++;
161 ipf->ipf_timer = IPFLOW_TIMER;
162
163 if (rt->rt_flags & RTF_GATEWAY)
164 dst = rt->rt_gateway;
165 else
166 dst = &ipf->ipf_ro.ro_dst;
167 if ((error = (*rt->rt_ifp->if_output)(rt->rt_ifp, m, dst, rt)) != 0) {
168 if (error == ENOBUFS)
169 ipf->ipf_dropped++;
170 else
171 ipf->ipf_errors++;
172 }
173 return 1;
174 }
175
176 static void
177 ipflow_addstats(
178 struct ipflow *ipf)
179 {
180 ipf->ipf_ro.ro_rt->rt_use += ipf->ipf_uses;
181 ipstat.ips_cantforward += ipf->ipf_errors + ipf->ipf_dropped;
182 ipstat.ips_forward += ipf->ipf_uses;
183 ipstat.ips_fastforward += ipf->ipf_uses;
184 }
185
186 static void
187 ipflow_free(
188 struct ipflow *ipf)
189 {
190 int s;
191 /*
192 * Remove the flow from the hash table (at elevated IPL).
193 * Once it's off the list, we can deal with it at normal
194 * network IPL.
195 */
196 s = splimp();
197 LIST_REMOVE(ipf, ipf_next);
198 splx(s);
199 ipflow_addstats(ipf);
200 RTFREE(ipf->ipf_ro.ro_rt);
201 ipflow_inuse--;
202 free(ipf, M_IPFLOW);
203 }
204
205 static struct ipflow *
206 ipflow_reap(
207 void)
208 {
209 struct ipflow *ipf, *maybe_ipf = NULL;
210 int idx;
211 int s;
212
213 for (idx = 0; idx < IPFLOW_HASHSIZE; idx++) {
214 ipf = LIST_FIRST(&ipflows[idx]);
215 while (ipf != NULL) {
216 /*
217 * If this no longer points to a valid route
218 * reclaim it.
219 */
220 if ((ipf->ipf_ro.ro_rt->rt_flags & RTF_UP) == 0)
221 goto done;
222 /*
223 * choose the one that's been least recently used
224 * or has had the least uses in the last 1.5
225 * intervals.
226 */
227 if (maybe_ipf == NULL
228 || ipf->ipf_timer < maybe_ipf->ipf_timer
229 || (ipf->ipf_timer == maybe_ipf->ipf_timer
230 && ipf->ipf_last_uses + ipf->ipf_uses <
231 maybe_ipf->ipf_last_uses +
232 maybe_ipf->ipf_uses))
233 maybe_ipf = ipf;
234 ipf = LIST_NEXT(ipf, ipf_next);
235 }
236 }
237 ipf = maybe_ipf;
238 done:
239 /*
240 * Remove the entry from the flow table.
241 */
242 s = splimp();
243 LIST_REMOVE(ipf, ipf_next);
244 splx(s);
245 ipflow_addstats(ipf);
246 RTFREE(ipf->ipf_ro.ro_rt);
247 return ipf;
248 }
249
250 void
251 ipflow_slowtimo(
252 void)
253 {
254 struct ipflow *ipf;
255 int idx;
256
257 for (idx = 0; idx < IPFLOW_HASHSIZE; idx++) {
258 ipf = LIST_FIRST(&ipflows[idx]);
259 while (ipf != NULL) {
260 struct ipflow *next_ipf = LIST_NEXT(ipf, ipf_next);
261 if (--ipf->ipf_timer == 0) {
262 ipflow_free(ipf);
263 } else {
264 ipf->ipf_last_uses = ipf->ipf_uses;
265 ipf->ipf_ro.ro_rt->rt_use += ipf->ipf_uses;
266 ipstat.ips_forward += ipf->ipf_uses;
267 ipstat.ips_fastforward += ipf->ipf_uses;
268 ipf->ipf_uses = 0;
269 }
270 ipf = next_ipf;
271 }
272 }
273 }
274
275 void
276 ipflow_create(
277 const struct route *ro,
278 struct mbuf *m)
279 {
280 const struct ip *const ip = mtod(m, struct ip *);
281 struct ipflow *ipf;
282 unsigned hash;
283 int s;
284
285 /*
286 * Don't create cache entries for ICMP messages.
287 */
288 if (!ipflow_active || ip->ip_p == IPPROTO_ICMP)
289 return;
290 /*
291 * See if an existing flow struct exists. If so remove it from it's
292 * list and free the old route. If not, try to malloc a new one
293 * (if we aren't at our limit).
294 */
295 ipf = ipflow_lookup(ip);
296 if (ipf == NULL) {
297 if (ipflow_inuse == IPFLOW_MAX) {
298 ipf = ipflow_reap();
299 } else {
300 ipf = (struct ipflow *) malloc(sizeof(*ipf), M_IPFLOW,
301 M_NOWAIT);
302 if (ipf == NULL)
303 return;
304 ipflow_inuse++;
305 }
306 bzero((caddr_t) ipf, sizeof(*ipf));
307 } else {
308 s = splimp();
309 LIST_REMOVE(ipf, ipf_next);
310 splx(s);
311 ipflow_addstats(ipf);
312 RTFREE(ipf->ipf_ro.ro_rt);
313 ipf->ipf_uses = ipf->ipf_last_uses = 0;
314 ipf->ipf_errors = ipf->ipf_dropped = 0;
315 }
316
317 /*
318 * Fill in the updated information.
319 */
320 ipf->ipf_ro = *ro;
321 ro->ro_rt->rt_refcnt++;
322 ipf->ipf_dst = ip->ip_dst;
323 ipf->ipf_src = ip->ip_src;
324 ipf->ipf_tos = ip->ip_tos;
325 ipf->ipf_timer = IPFLOW_TIMER;
326 /*
327 * Insert into the approriate bucket of the flow table.
328 */
329 hash = ipflow_hash(ip->ip_dst, ip->ip_src, ip->ip_tos);
330 s = splimp();
331 LIST_INSERT_HEAD(&ipflows[hash], ipf, ipf_next);
332 splx(s);
333 }
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