1 /*
2 * Copyright (c) 2003 Andre Oppermann, Internet Business Solutions AG
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. The name of the author may not be used to endorse or promote
14 * products derived from this software without specific prior written
15 * permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 *
29 * $FreeBSD: releng/5.3/sys/netinet/ip_fastfwd.c 136588 2004-10-16 08:43:07Z cvs2svn $
30 */
31
32 /*
33 * ip_fastforward gets its speed from processing the forwarded packet to
34 * completion (if_output on the other side) without any queues or netisr's.
35 * The receiving interface DMAs the packet into memory, the upper half of
36 * driver calls ip_fastforward, we do our routing table lookup and directly
37 * send it off to the outgoing interface which DMAs the packet to the
38 * network card. The only part of the packet we touch with the CPU is the
39 * IP header (unless there are complex firewall rules touching other parts
40 * of the packet, but that is up to you). We are essentially limited by bus
41 * bandwidth and how fast the network card/driver can set up receives and
42 * transmits.
43 *
44 * We handle basic errors, ip header errors, checksum errors,
45 * destination unreachable, fragmentation and fragmentation needed and
46 * report them via icmp to the sender.
47 *
48 * Else if something is not pure IPv4 unicast forwarding we fall back to
49 * the normal ip_input processing path. We should only be called from
50 * interfaces connected to the outside world.
51 *
52 * Firewalling is fully supported including divert, ipfw fwd and ipfilter
53 * ipnat and address rewrite.
54 *
55 * IPSEC is not supported if this host is a tunnel broker. IPSEC is
56 * supported for connections to/from local host.
57 *
58 * We try to do the least expensive (in CPU ops) checks and operations
59 * first to catch junk with as little overhead as possible.
60 *
61 * We take full advantage of hardware support for ip checksum and
62 * fragmentation offloading.
63 *
64 * We don't do ICMP redirect in the fast forwarding path. I have had my own
65 * cases where two core routers with Zebra routing suite would send millions
66 * ICMP redirects to connected hosts if the router to dest was not the default
67 * gateway. In one case it was filling the routing table of a host with close
68 * 300'000 cloned redirect entries until it ran out of kernel memory. However
69 * the networking code proved very robust and it didn't crash or went ill
70 * otherwise.
71 */
72
73 /*
74 * Many thanks to Matt Thomas of NetBSD for basic structure of ip_flow.c which
75 * is being followed here.
76 */
77
78 #include "opt_ipfw.h"
79 #include "opt_ipstealth.h"
80
81 #include <sys/param.h>
82 #include <sys/systm.h>
83 #include <sys/kernel.h>
84 #include <sys/malloc.h>
85 #include <sys/mbuf.h>
86 #include <sys/protosw.h>
87 #include <sys/socket.h>
88 #include <sys/sysctl.h>
89
90 #include <net/pfil.h>
91 #include <net/if.h>
92 #include <net/if_types.h>
93 #include <net/if_var.h>
94 #include <net/if_dl.h>
95 #include <net/route.h>
96
97 #include <netinet/in.h>
98 #include <netinet/in_systm.h>
99 #include <netinet/in_var.h>
100 #include <netinet/ip.h>
101 #include <netinet/ip_var.h>
102 #include <netinet/ip_icmp.h>
103
104 #include <machine/in_cksum.h>
105
106 static int ipfastforward_active = 0;
107 SYSCTL_INT(_net_inet_ip, OID_AUTO, fastforwarding, CTLFLAG_RW,
108 &ipfastforward_active, 0, "Enable fast IP forwarding");
109
110 static struct sockaddr_in *
111 ip_findroute(struct route *ro, struct in_addr dest, struct mbuf *m)
112 {
113 struct sockaddr_in *dst;
114 struct rtentry *rt;
115
116 /*
117 * Find route to destination.
118 */
119 bzero(ro, sizeof(*ro));
120 dst = (struct sockaddr_in *)&ro->ro_dst;
121 dst->sin_family = AF_INET;
122 dst->sin_len = sizeof(*dst);
123 dst->sin_addr.s_addr = dest.s_addr;
124 rtalloc_ign(ro, RTF_CLONING);
125
126 /*
127 * Route there and interface still up?
128 */
129 rt = ro->ro_rt;
130 if (rt && (rt->rt_flags & RTF_UP) &&
131 (rt->rt_ifp->if_flags & IFF_UP) &&
132 (rt->rt_ifp->if_flags & IFF_RUNNING)) {
133 if (rt->rt_flags & RTF_GATEWAY)
134 dst = (struct sockaddr_in *)rt->rt_gateway;
135 } else {
136 ipstat.ips_noroute++;
137 ipstat.ips_cantforward++;
138 if (rt)
139 RTFREE(rt);
140 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, NULL);
141 return NULL;
142 }
143 return dst;
144 }
145
146 /*
147 * Try to forward a packet based on the destination address.
148 * This is a fast path optimized for the plain forwarding case.
149 * If the packet is handled (and consumed) here then we return 1;
150 * otherwise 0 is returned and the packet should be delivered
151 * to ip_input for full processing.
152 */
153 int
154 ip_fastforward(struct mbuf *m)
155 {
156 struct ip *ip;
157 struct mbuf *m0 = NULL;
158 struct route ro;
159 struct sockaddr_in *dst = NULL;
160 struct in_ifaddr *ia = NULL;
161 struct ifaddr *ifa = NULL;
162 struct ifnet *ifp;
163 struct in_addr odest, dest;
164 u_short sum, ip_len;
165 int error = 0;
166 int hlen, mtu;
167 #ifdef IPFIREWALL_FORWARD
168 struct m_tag *fwd_tag;
169 #endif
170
171 /*
172 * Are we active and forwarding packets?
173 */
174 if (!ipfastforward_active || !ipforwarding)
175 return 0;
176
177 M_ASSERTVALID(m);
178 M_ASSERTPKTHDR(m);
179
180 ro.ro_rt = NULL;
181
182 /*
183 * Step 1: check for packet drop conditions (and sanity checks)
184 */
185
186 /*
187 * Is entire packet big enough?
188 */
189 if (m->m_pkthdr.len < sizeof(struct ip)) {
190 ipstat.ips_tooshort++;
191 goto drop;
192 }
193
194 /*
195 * Is first mbuf large enough for ip header and is header present?
196 */
197 if (m->m_len < sizeof (struct ip) &&
198 (m = m_pullup(m, sizeof (struct ip))) == 0) {
199 ipstat.ips_toosmall++;
200 goto drop;
201 }
202
203 ip = mtod(m, struct ip *);
204
205 /*
206 * Is it IPv4?
207 */
208 if (ip->ip_v != IPVERSION) {
209 ipstat.ips_badvers++;
210 goto drop;
211 }
212
213 /*
214 * Is IP header length correct and is it in first mbuf?
215 */
216 hlen = ip->ip_hl << 2;
217 if (hlen < sizeof(struct ip)) { /* minimum header length */
218 ipstat.ips_badlen++;
219 goto drop;
220 }
221 if (hlen > m->m_len) {
222 if ((m = m_pullup(m, hlen)) == 0) {
223 ipstat.ips_badhlen++;
224 goto drop;
225 }
226 ip = mtod(m, struct ip *);
227 }
228
229 /*
230 * Checksum correct?
231 */
232 if (m->m_pkthdr.csum_flags & CSUM_IP_CHECKED)
233 sum = !(m->m_pkthdr.csum_flags & CSUM_IP_VALID);
234 else {
235 if (hlen == sizeof(struct ip))
236 sum = in_cksum_hdr(ip);
237 else
238 sum = in_cksum(m, hlen);
239 }
240 if (sum) {
241 ipstat.ips_badsum++;
242 goto drop;
243 }
244 m->m_pkthdr.csum_flags |= (CSUM_IP_CHECKED | CSUM_IP_VALID);
245
246 ip_len = ntohs(ip->ip_len);
247
248 /*
249 * Is IP length longer than packet we have got?
250 */
251 if (m->m_pkthdr.len < ip_len) {
252 ipstat.ips_tooshort++;
253 goto drop;
254 }
255
256 /*
257 * Is packet longer than IP header tells us? If yes, truncate packet.
258 */
259 if (m->m_pkthdr.len > ip_len) {
260 if (m->m_len == m->m_pkthdr.len) {
261 m->m_len = ip_len;
262 m->m_pkthdr.len = ip_len;
263 } else
264 m_adj(m, ip_len - m->m_pkthdr.len);
265 }
266
267 /*
268 * Is packet from or to 127/8?
269 */
270 if ((ntohl(ip->ip_dst.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET ||
271 (ntohl(ip->ip_src.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET) {
272 ipstat.ips_badaddr++;
273 goto drop;
274 }
275
276 #ifdef ALTQ
277 /*
278 * Is packet dropped by traffic conditioner?
279 */
280 if (altq_input != NULL && (*altq_input)(m, AF_INET) == 0)
281 return 1;
282 #endif
283
284 /*
285 * Step 2: fallback conditions to normal ip_input path processing
286 */
287
288 /*
289 * Only IP packets without options
290 */
291 if (ip->ip_hl != (sizeof(struct ip) >> 2)) {
292 if (ip_doopts == 1)
293 return 0;
294 else if (ip_doopts == 2) {
295 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_FILTER_PROHIB,
296 0, NULL);
297 return 1;
298 }
299 /* else ignore IP options and continue */
300 }
301
302 /*
303 * Only unicast IP, not from loopback, no L2 or IP broadcast,
304 * no multicast, no INADDR_ANY
305 *
306 * XXX: Probably some of these checks could be direct drop
307 * conditions. However it is not clear whether there are some
308 * hacks or obscure behaviours which make it neccessary to
309 * let ip_input handle it. We play safe here and let ip_input
310 * deal with it until it is proven that we can directly drop it.
311 */
312 if ((m->m_pkthdr.rcvif->if_flags & IFF_LOOPBACK) ||
313 ntohl(ip->ip_src.s_addr) == (u_long)INADDR_BROADCAST ||
314 ntohl(ip->ip_dst.s_addr) == (u_long)INADDR_BROADCAST ||
315 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
316 IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
317 ip->ip_dst.s_addr == INADDR_ANY )
318 return 0;
319
320 /*
321 * Is it for a local address on this host?
322 */
323 if (in_localip(ip->ip_dst))
324 return 0;
325
326 /*
327 * Or is it for a local IP broadcast address on this host?
328 */
329 if ((m->m_flags & M_BCAST) &&
330 (m->m_pkthdr.rcvif->if_flags & IFF_BROADCAST)) {
331 TAILQ_FOREACH(ifa, &m->m_pkthdr.rcvif->if_addrhead, ifa_link) {
332 if (ifa->ifa_addr->sa_family != AF_INET)
333 continue;
334 ia = ifatoia(ifa);
335 if (ia->ia_netbroadcast.s_addr == ip->ip_dst.s_addr)
336 return 0;
337 if (satosin(&ia->ia_broadaddr)->sin_addr.s_addr ==
338 ip->ip_dst.s_addr)
339 return 0;
340 }
341 }
342 ipstat.ips_total++;
343
344 /*
345 * Step 3: incoming packet firewall processing
346 */
347
348 /*
349 * Convert to host representation
350 */
351 ip->ip_len = ntohs(ip->ip_len);
352 ip->ip_off = ntohs(ip->ip_off);
353
354 odest.s_addr = dest.s_addr = ip->ip_dst.s_addr;
355
356 /*
357 * Run through list of ipfilter hooks for input packets
358 */
359 if (inet_pfil_hook.ph_busy_count == -1)
360 goto passin;
361
362 if (pfil_run_hooks(&inet_pfil_hook, &m, m->m_pkthdr.rcvif, PFIL_IN, NULL) ||
363 m == NULL)
364 return 1;
365
366 M_ASSERTVALID(m);
367 M_ASSERTPKTHDR(m);
368
369 ip = mtod(m, struct ip *); /* m may have changed by pfil hook */
370 dest.s_addr = ip->ip_dst.s_addr;
371
372 /*
373 * Destination address changed?
374 */
375 if (odest.s_addr != dest.s_addr) {
376 /*
377 * Is it now for a local address on this host?
378 */
379 if (in_localip(dest))
380 goto forwardlocal;
381 /*
382 * Go on with new destination address
383 */
384 }
385 #ifdef IPFIREWALL_FORWARD
386 if (m->m_flags & M_FASTFWD_OURS) {
387 /*
388 * ipfw changed it for a local address on this host.
389 */
390 goto forwardlocal;
391 }
392 #endif /* IPFIREWALL_FORWARD */
393
394 passin:
395 /*
396 * Step 4: decrement TTL and look up route
397 */
398
399 /*
400 * Check TTL
401 */
402 #ifdef IPSTEALTH
403 if (!ipstealth) {
404 #endif
405 if (ip->ip_ttl <= IPTTLDEC) {
406 icmp_error(m, ICMP_TIMXCEED, ICMP_TIMXCEED_INTRANS, 0, NULL);
407 return 1;
408 }
409
410 /*
411 * Decrement the TTL and incrementally change the checksum.
412 * Don't bother doing this with hw checksum offloading.
413 */
414 ip->ip_ttl -= IPTTLDEC;
415 if (ip->ip_sum >= (u_int16_t) ~htons(IPTTLDEC << 8))
416 ip->ip_sum -= ~htons(IPTTLDEC << 8);
417 else
418 ip->ip_sum += htons(IPTTLDEC << 8);
419 #ifdef IPSTEALTH
420 }
421 #endif
422
423 /*
424 * Find route to destination.
425 */
426 if ((dst = ip_findroute(&ro, dest, m)) == NULL)
427 return 1; /* icmp unreach already sent */
428 ifp = ro.ro_rt->rt_ifp;
429
430 /*
431 * Step 5: outgoing firewall packet processing
432 */
433
434 /*
435 * Run through list of hooks for output packets.
436 */
437 if (inet_pfil_hook.ph_busy_count == -1)
438 goto passout;
439
440 if (pfil_run_hooks(&inet_pfil_hook, &m, ifp, PFIL_OUT, NULL) || m == NULL) {
441 goto consumed;
442 }
443
444 M_ASSERTVALID(m);
445 M_ASSERTPKTHDR(m);
446
447 ip = mtod(m, struct ip *);
448 dest.s_addr = ip->ip_dst.s_addr;
449
450 /*
451 * Destination address changed?
452 */
453 #ifndef IPFIREWALL_FORWARD
454 if (odest.s_addr != dest.s_addr) {
455 #else
456 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL);
457 if (odest.s_addr != dest.s_addr || fwd_tag != NULL) {
458 #endif /* IPFIREWALL_FORWARD */
459 /*
460 * Is it now for a local address on this host?
461 */
462 #ifndef IPFIREWALL_FORWARD
463 if (in_localip(dest)) {
464 #else
465 if (in_localip(dest) || m->m_flags & M_FASTFWD_OURS) {
466 #endif /* IPFIREWALL_FORWARD */
467 forwardlocal:
468 /*
469 * Return packet for processing by ip_input().
470 * Keep host byte order as expected at ip_input's
471 * "ours"-label.
472 */
473 m->m_flags |= M_FASTFWD_OURS;
474 if (ro.ro_rt)
475 RTFREE(ro.ro_rt);
476 return 0;
477 }
478 /*
479 * Redo route lookup with new destination address
480 */
481 #ifdef IPFIREWALL_FORWARD
482 if (fwd_tag) {
483 if (!in_localip(ip->ip_src) && !in_localaddr(ip->ip_dst))
484 dest.s_addr = ((struct sockaddr_in *)(fwd_tag+1))->sin_addr.s_addr;
485 m_tag_delete(m, fwd_tag);
486 }
487 #endif /* IPFIREWALL_FORWARD */
488 RTFREE(ro.ro_rt);
489 if ((dst = ip_findroute(&ro, dest, m)) == NULL)
490 return 1; /* icmp unreach already sent */
491 ifp = ro.ro_rt->rt_ifp;
492 }
493
494 passout:
495 /*
496 * Step 6: send off the packet
497 */
498
499 /*
500 * Check if route is dampned (when ARP is unable to resolve)
501 */
502 if ((ro.ro_rt->rt_flags & RTF_REJECT) &&
503 ro.ro_rt->rt_rmx.rmx_expire >= time_second) {
504 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, NULL);
505 goto consumed;
506 }
507
508 #ifndef ALTQ
509 /*
510 * Check if there is enough space in the interface queue
511 */
512 if ((ifp->if_snd.ifq_len + ip->ip_len / ifp->if_mtu + 1) >=
513 ifp->if_snd.ifq_maxlen) {
514 ipstat.ips_odropped++;
515 /* would send source quench here but that is depreciated */
516 goto drop;
517 }
518 #endif
519
520 /*
521 * Check if media link state of interface is not down
522 */
523 if (ifp->if_link_state == LINK_STATE_DOWN) {
524 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, NULL);
525 goto consumed;
526 }
527
528 /*
529 * Check if packet fits MTU or if hardware will fragement for us
530 */
531 if (ro.ro_rt->rt_rmx.rmx_mtu)
532 mtu = min(ro.ro_rt->rt_rmx.rmx_mtu, ifp->if_mtu);
533 else
534 mtu = ifp->if_mtu;
535
536 if (ip->ip_len <= mtu ||
537 (ifp->if_hwassist & CSUM_FRAGMENT && (ip->ip_off & IP_DF) == 0)) {
538 /*
539 * Restore packet header fields to original values
540 */
541 ip->ip_len = htons(ip->ip_len);
542 ip->ip_off = htons(ip->ip_off);
543 /*
544 * Send off the packet via outgoing interface
545 */
546 error = (*ifp->if_output)(ifp, m,
547 (struct sockaddr *)dst, ro.ro_rt);
548 } else {
549 /*
550 * Handle EMSGSIZE with icmp reply needfrag for TCP MTU discovery
551 */
552 if (ip->ip_off & IP_DF) {
553 ipstat.ips_cantfrag++;
554 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_NEEDFRAG,
555 0, ifp);
556 goto consumed;
557 } else {
558 /*
559 * We have to fragement the packet
560 */
561 m->m_pkthdr.csum_flags |= CSUM_IP;
562 /*
563 * ip_fragment expects ip_len and ip_off in host byte
564 * order but returns all packets in network byte order
565 */
566 if (ip_fragment(ip, &m, mtu, ifp->if_hwassist,
567 (~ifp->if_hwassist & CSUM_DELAY_IP))) {
568 goto drop;
569 }
570 KASSERT(m != NULL, ("null mbuf and no error"));
571 /*
572 * Send off the fragments via outgoing interface
573 */
574 error = 0;
575 do {
576 m0 = m->m_nextpkt;
577 m->m_nextpkt = NULL;
578
579 error = (*ifp->if_output)(ifp, m,
580 (struct sockaddr *)dst, ro.ro_rt);
581 if (error)
582 break;
583 } while ((m = m0) != NULL);
584 if (error) {
585 /* Reclaim remaining fragments */
586 for (; m; m = m0) {
587 m0 = m->m_nextpkt;
588 m->m_nextpkt = NULL;
589 m_freem(m);
590 }
591 } else
592 ipstat.ips_fragmented++;
593 }
594 }
595
596 if (error != 0)
597 ipstat.ips_odropped++;
598 else {
599 ro.ro_rt->rt_rmx.rmx_pksent++;
600 ipstat.ips_forward++;
601 ipstat.ips_fastforward++;
602 }
603 consumed:
604 RTFREE(ro.ro_rt);
605 return 1;
606 drop:
607 if (m)
608 m_freem(m);
609 if (ro.ro_rt)
610 RTFREE(ro.ro_rt);
611 return 1;
612 }
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