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
30 /*
31 * ip_fastforward gets its speed from processing the forwarded packet to
32 * completion (if_output on the other side) without any queues or netisr's.
33 * The receiving interface DMAs the packet into memory, the upper half of
34 * driver calls ip_fastforward, we do our routing table lookup and directly
35 * send it off to the outgoing interface, which DMAs the packet to the
36 * network card. The only part of the packet we touch with the CPU is the
37 * IP header (unless there are complex firewall rules touching other parts
38 * of the packet, but that is up to you). We are essentially limited by bus
39 * bandwidth and how fast the network card/driver can set up receives and
40 * transmits.
41 *
42 * We handle basic errors, IP header errors, checksum errors,
43 * destination unreachable, fragmentation and fragmentation needed and
44 * report them via ICMP to the sender.
45 *
46 * Else if something is not pure IPv4 unicast forwarding we fall back to
47 * the normal ip_input processing path. We should only be called from
48 * interfaces connected to the outside world.
49 *
50 * Firewalling is fully supported including divert, ipfw fwd and ipfilter
51 * ipnat and address rewrite.
52 *
53 * IPSEC is not supported if this host is a tunnel broker. IPSEC is
54 * supported for connections to/from local host.
55 *
56 * We try to do the least expensive (in CPU ops) checks and operations
57 * first to catch junk with as little overhead as possible.
58 *
59 * We take full advantage of hardware support for IP checksum and
60 * fragmentation offloading.
61 *
62 * We don't do ICMP redirect in the fast forwarding path. I have had my own
63 * cases where two core routers with Zebra routing suite would send millions
64 * ICMP redirects to connected hosts if the destination router was not the
65 * default gateway. In one case it was filling the routing table of a host
66 * with approximately 300.000 cloned redirect entries until it ran out of
67 * kernel memory. However the networking code proved very robust and it didn't
68 * crash or fail in other ways.
69 */
70
71 /*
72 * Many thanks to Matt Thomas of NetBSD for basic structure of ip_flow.c which
73 * is being followed here.
74 */
75
76 #include <sys/cdefs.h>
77 __FBSDID("$FreeBSD: releng/10.2/sys/netinet/ip_fastfwd.c 272868 2014-10-09 23:45:26Z hrs $");
78
79 #include "opt_ipfw.h"
80 #include "opt_ipstealth.h"
81 #include "opt_kdtrace.h"
82
83 #include <sys/param.h>
84 #include <sys/systm.h>
85 #include <sys/kernel.h>
86 #include <sys/malloc.h>
87 #include <sys/mbuf.h>
88 #include <sys/protosw.h>
89 #include <sys/sdt.h>
90 #include <sys/socket.h>
91 #include <sys/sysctl.h>
92
93 #include <net/pfil.h>
94 #include <net/if.h>
95 #include <net/if_types.h>
96 #include <net/if_var.h>
97 #include <net/if_dl.h>
98 #include <net/route.h>
99 #include <net/vnet.h>
100
101 #include <netinet/in.h>
102 #include <netinet/in_kdtrace.h>
103 #include <netinet/in_systm.h>
104 #include <netinet/in_var.h>
105 #include <netinet/ip.h>
106 #include <netinet/ip_var.h>
107 #include <netinet/ip_icmp.h>
108 #include <netinet/ip_options.h>
109
110 #include <machine/in_cksum.h>
111
112 static VNET_DEFINE(int, ipfastforward_active);
113 #define V_ipfastforward_active VNET(ipfastforward_active)
114
115 SYSCTL_VNET_INT(_net_inet_ip, OID_AUTO, fastforwarding, CTLFLAG_RW,
116 &VNET_NAME(ipfastforward_active), 0, "Enable fast IP forwarding");
117
118 static struct sockaddr_in *
119 ip_findroute(struct route *ro, struct in_addr dest, struct mbuf *m)
120 {
121 struct sockaddr_in *dst;
122 struct rtentry *rt;
123
124 /*
125 * Find route to destination.
126 */
127 bzero(ro, sizeof(*ro));
128 dst = (struct sockaddr_in *)&ro->ro_dst;
129 dst->sin_family = AF_INET;
130 dst->sin_len = sizeof(*dst);
131 dst->sin_addr.s_addr = dest.s_addr;
132 in_rtalloc_ign(ro, 0, M_GETFIB(m));
133
134 /*
135 * Route there and interface still up?
136 */
137 rt = ro->ro_rt;
138 if (rt && (rt->rt_flags & RTF_UP) &&
139 (rt->rt_ifp->if_flags & IFF_UP) &&
140 (rt->rt_ifp->if_drv_flags & IFF_DRV_RUNNING)) {
141 if (rt->rt_flags & RTF_GATEWAY)
142 dst = (struct sockaddr_in *)rt->rt_gateway;
143 } else {
144 IPSTAT_INC(ips_noroute);
145 IPSTAT_INC(ips_cantforward);
146 if (rt)
147 RTFREE(rt);
148 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0);
149 return NULL;
150 }
151 return dst;
152 }
153
154 /*
155 * Try to forward a packet based on the destination address.
156 * This is a fast path optimized for the plain forwarding case.
157 * If the packet is handled (and consumed) here then we return NULL;
158 * otherwise mbuf is returned and the packet should be delivered
159 * to ip_input for full processing.
160 */
161 struct mbuf *
162 ip_fastforward(struct mbuf *m)
163 {
164 struct ip *ip;
165 struct mbuf *m0 = NULL;
166 struct route ro;
167 struct sockaddr_in *dst = NULL;
168 struct ifnet *ifp;
169 struct in_addr odest, dest;
170 uint16_t sum, ip_len, ip_off;
171 int error = 0;
172 int hlen, mtu;
173 struct m_tag *fwd_tag = NULL;
174
175 /*
176 * Are we active and forwarding packets?
177 */
178 if (!V_ipfastforward_active || !V_ipforwarding)
179 return m;
180
181 M_ASSERTVALID(m);
182 M_ASSERTPKTHDR(m);
183
184 bzero(&ro, sizeof(ro));
185
186 /*
187 * Step 1: check for packet drop conditions (and sanity checks)
188 */
189
190 /*
191 * Is entire packet big enough?
192 */
193 if (m->m_pkthdr.len < sizeof(struct ip)) {
194 IPSTAT_INC(ips_tooshort);
195 goto drop;
196 }
197
198 /*
199 * Is first mbuf large enough for ip header and is header present?
200 */
201 if (m->m_len < sizeof (struct ip) &&
202 (m = m_pullup(m, sizeof (struct ip))) == NULL) {
203 IPSTAT_INC(ips_toosmall);
204 return NULL; /* mbuf already free'd */
205 }
206
207 ip = mtod(m, struct ip *);
208
209 /*
210 * Is it IPv4?
211 */
212 if (ip->ip_v != IPVERSION) {
213 IPSTAT_INC(ips_badvers);
214 goto drop;
215 }
216
217 /*
218 * Is IP header length correct and is it in first mbuf?
219 */
220 hlen = ip->ip_hl << 2;
221 if (hlen < sizeof(struct ip)) { /* minimum header length */
222 IPSTAT_INC(ips_badhlen);
223 goto drop;
224 }
225 if (hlen > m->m_len) {
226 if ((m = m_pullup(m, hlen)) == NULL) {
227 IPSTAT_INC(ips_badhlen);
228 return NULL; /* mbuf already free'd */
229 }
230 ip = mtod(m, struct ip *);
231 }
232
233 /*
234 * Checksum correct?
235 */
236 if (m->m_pkthdr.csum_flags & CSUM_IP_CHECKED)
237 sum = !(m->m_pkthdr.csum_flags & CSUM_IP_VALID);
238 else {
239 if (hlen == sizeof(struct ip))
240 sum = in_cksum_hdr(ip);
241 else
242 sum = in_cksum(m, hlen);
243 }
244 if (sum) {
245 IPSTAT_INC(ips_badsum);
246 goto drop;
247 }
248
249 /*
250 * Remember that we have checked the IP header and found it valid.
251 */
252 m->m_pkthdr.csum_flags |= (CSUM_IP_CHECKED | CSUM_IP_VALID);
253
254 ip_len = ntohs(ip->ip_len);
255
256 /*
257 * Is IP length longer than packet we have got?
258 */
259 if (m->m_pkthdr.len < ip_len) {
260 IPSTAT_INC(ips_tooshort);
261 goto drop;
262 }
263
264 /*
265 * Is packet longer than IP header tells us? If yes, truncate packet.
266 */
267 if (m->m_pkthdr.len > ip_len) {
268 if (m->m_len == m->m_pkthdr.len) {
269 m->m_len = ip_len;
270 m->m_pkthdr.len = ip_len;
271 } else
272 m_adj(m, ip_len - m->m_pkthdr.len);
273 }
274
275 /*
276 * Is packet from or to 127/8?
277 */
278 if ((ntohl(ip->ip_dst.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET ||
279 (ntohl(ip->ip_src.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET) {
280 IPSTAT_INC(ips_badaddr);
281 goto drop;
282 }
283
284 #ifdef ALTQ
285 /*
286 * Is packet dropped by traffic conditioner?
287 */
288 if (altq_input != NULL && (*altq_input)(m, AF_INET) == 0)
289 goto drop;
290 #endif
291
292 /*
293 * Step 2: fallback conditions to normal ip_input path processing
294 */
295
296 /*
297 * Only IP packets without options
298 */
299 if (ip->ip_hl != (sizeof(struct ip) >> 2)) {
300 if (V_ip_doopts == 1)
301 return m;
302 else if (V_ip_doopts == 2) {
303 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_FILTER_PROHIB,
304 0, 0);
305 return NULL; /* mbuf already free'd */
306 }
307 /* else ignore IP options and continue */
308 }
309
310 /*
311 * Only unicast IP, not from loopback, no L2 or IP broadcast,
312 * no multicast, no INADDR_ANY
313 *
314 * XXX: Probably some of these checks could be direct drop
315 * conditions. However it is not clear whether there are some
316 * hacks or obscure behaviours which make it neccessary to
317 * let ip_input handle it. We play safe here and let ip_input
318 * deal with it until it is proven that we can directly drop it.
319 */
320 if ((m->m_flags & (M_BCAST|M_MCAST)) ||
321 (m->m_pkthdr.rcvif->if_flags & IFF_LOOPBACK) ||
322 ntohl(ip->ip_src.s_addr) == (u_long)INADDR_BROADCAST ||
323 ntohl(ip->ip_dst.s_addr) == (u_long)INADDR_BROADCAST ||
324 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
325 IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
326 IN_LINKLOCAL(ntohl(ip->ip_src.s_addr)) ||
327 IN_LINKLOCAL(ntohl(ip->ip_dst.s_addr)) ||
328 ip->ip_src.s_addr == INADDR_ANY ||
329 ip->ip_dst.s_addr == INADDR_ANY )
330 return m;
331
332 /*
333 * Is it for a local address on this host?
334 */
335 if (in_localip(ip->ip_dst))
336 return m;
337
338 IPSTAT_INC(ips_total);
339
340 /*
341 * Step 3: incoming packet firewall processing
342 */
343
344 odest.s_addr = dest.s_addr = ip->ip_dst.s_addr;
345
346 /*
347 * Run through list of ipfilter hooks for input packets
348 */
349 if (!PFIL_HOOKED(&V_inet_pfil_hook))
350 goto passin;
351
352 if (pfil_run_hooks(
353 &V_inet_pfil_hook, &m, m->m_pkthdr.rcvif, PFIL_IN, NULL) ||
354 m == NULL)
355 goto drop;
356
357 M_ASSERTVALID(m);
358 M_ASSERTPKTHDR(m);
359
360 ip = mtod(m, struct ip *); /* m may have changed by pfil hook */
361 dest.s_addr = ip->ip_dst.s_addr;
362
363 /*
364 * Destination address changed?
365 */
366 if (odest.s_addr != dest.s_addr) {
367 /*
368 * Is it now for a local address on this host?
369 */
370 if (in_localip(dest))
371 goto forwardlocal;
372 /*
373 * Go on with new destination address
374 */
375 }
376
377 if (m->m_flags & M_FASTFWD_OURS) {
378 /*
379 * ipfw changed it for a local address on this host.
380 */
381 goto forwardlocal;
382 }
383
384 passin:
385 /*
386 * Step 4: decrement TTL and look up route
387 */
388
389 /*
390 * Check TTL
391 */
392 #ifdef IPSTEALTH
393 if (!V_ipstealth) {
394 #endif
395 if (ip->ip_ttl <= IPTTLDEC) {
396 icmp_error(m, ICMP_TIMXCEED, ICMP_TIMXCEED_INTRANS, 0, 0);
397 return NULL; /* mbuf already free'd */
398 }
399
400 /*
401 * Decrement the TTL and incrementally change the IP header checksum.
402 * Don't bother doing this with hw checksum offloading, it's faster
403 * doing it right here.
404 */
405 ip->ip_ttl -= IPTTLDEC;
406 if (ip->ip_sum >= (u_int16_t) ~htons(IPTTLDEC << 8))
407 ip->ip_sum -= ~htons(IPTTLDEC << 8);
408 else
409 ip->ip_sum += htons(IPTTLDEC << 8);
410 #ifdef IPSTEALTH
411 }
412 #endif
413
414 /*
415 * Find route to destination.
416 */
417 if ((dst = ip_findroute(&ro, dest, m)) == NULL)
418 return NULL; /* icmp unreach already sent */
419 ifp = ro.ro_rt->rt_ifp;
420
421 /*
422 * Immediately drop blackholed traffic, and directed broadcasts
423 * for either the all-ones or all-zero subnet addresses on
424 * locally attached networks.
425 */
426 if ((ro.ro_rt->rt_flags & (RTF_BLACKHOLE|RTF_BROADCAST)) != 0)
427 goto drop;
428
429 /*
430 * Step 5: outgoing firewall packet processing
431 */
432
433 /*
434 * Run through list of hooks for output packets.
435 */
436 if (!PFIL_HOOKED(&V_inet_pfil_hook))
437 goto passout;
438
439 if (pfil_run_hooks(&V_inet_pfil_hook, &m, ifp, PFIL_OUT, NULL) || m == NULL) {
440 goto drop;
441 }
442
443 M_ASSERTVALID(m);
444 M_ASSERTPKTHDR(m);
445
446 ip = mtod(m, struct ip *);
447 dest.s_addr = ip->ip_dst.s_addr;
448
449 /*
450 * Destination address changed?
451 */
452 if (m->m_flags & M_IP_NEXTHOP)
453 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL);
454 if (odest.s_addr != dest.s_addr || fwd_tag != NULL) {
455 /*
456 * Is it now for a local address on this host?
457 */
458 if (m->m_flags & M_FASTFWD_OURS || in_localip(dest)) {
459 forwardlocal:
460 /*
461 * Return packet for processing by ip_input().
462 */
463 m->m_flags |= M_FASTFWD_OURS;
464 if (ro.ro_rt)
465 RTFREE(ro.ro_rt);
466 return m;
467 }
468 /*
469 * Redo route lookup with new destination address
470 */
471 if (fwd_tag) {
472 dest.s_addr = ((struct sockaddr_in *)
473 (fwd_tag + 1))->sin_addr.s_addr;
474 m_tag_delete(m, fwd_tag);
475 m->m_flags &= ~M_IP_NEXTHOP;
476 }
477 RTFREE(ro.ro_rt);
478 if ((dst = ip_findroute(&ro, dest, m)) == NULL)
479 return NULL; /* icmp unreach already sent */
480 ifp = ro.ro_rt->rt_ifp;
481 }
482
483 passout:
484 /*
485 * Step 6: send off the packet
486 */
487 ip_len = ntohs(ip->ip_len);
488 ip_off = ntohs(ip->ip_off);
489
490 /*
491 * Check if route is dampned (when ARP is unable to resolve)
492 */
493 if ((ro.ro_rt->rt_flags & RTF_REJECT) &&
494 (ro.ro_rt->rt_expire == 0 || time_uptime < ro.ro_rt->rt_expire)) {
495 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0);
496 goto consumed;
497 }
498
499 #ifndef ALTQ
500 /*
501 * Check if there is enough space in the interface queue
502 */
503 if ((ifp->if_snd.ifq_len + ip_len / ifp->if_mtu + 1) >=
504 ifp->if_snd.ifq_maxlen) {
505 IPSTAT_INC(ips_odropped);
506 /* would send source quench here but that is depreciated */
507 goto drop;
508 }
509 #endif
510
511 /*
512 * Check if media link state of interface is not down
513 */
514 if (ifp->if_link_state == LINK_STATE_DOWN) {
515 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0);
516 goto consumed;
517 }
518
519 /*
520 * Check if packet fits MTU or if hardware will fragment for us
521 */
522 if (ro.ro_rt->rt_mtu)
523 mtu = min(ro.ro_rt->rt_mtu, ifp->if_mtu);
524 else
525 mtu = ifp->if_mtu;
526
527 if (ip_len <= mtu ||
528 (ifp->if_hwassist & CSUM_FRAGMENT && (ip_off & IP_DF) == 0)) {
529 /*
530 * Avoid confusing lower layers.
531 */
532 m_clrprotoflags(m);
533 /*
534 * Send off the packet via outgoing interface
535 */
536 IP_PROBE(send, NULL, NULL, ip, ifp, ip, NULL);
537 error = (*ifp->if_output)(ifp, m,
538 (struct sockaddr *)dst, &ro);
539 } else {
540 /*
541 * Handle EMSGSIZE with icmp reply needfrag for TCP MTU discovery
542 */
543 if (ip_off & IP_DF) {
544 IPSTAT_INC(ips_cantfrag);
545 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_NEEDFRAG,
546 0, mtu);
547 goto consumed;
548 } else {
549 /*
550 * We have to fragment the packet
551 */
552 m->m_pkthdr.csum_flags |= CSUM_IP;
553 if (ip_fragment(ip, &m, mtu, ifp->if_hwassist))
554 goto drop;
555 KASSERT(m != NULL, ("null mbuf and no error"));
556 /*
557 * Send off the fragments via outgoing interface
558 */
559 error = 0;
560 do {
561 m0 = m->m_nextpkt;
562 m->m_nextpkt = NULL;
563 /*
564 * Avoid confusing lower layers.
565 */
566 m_clrprotoflags(m);
567
568 IP_PROBE(send, NULL, NULL, ip, ifp, ip, NULL);
569 error = (*ifp->if_output)(ifp, m,
570 (struct sockaddr *)dst, &ro);
571 if (error)
572 break;
573 } while ((m = m0) != NULL);
574 if (error) {
575 /* Reclaim remaining fragments */
576 for (m = m0; m; m = m0) {
577 m0 = m->m_nextpkt;
578 m_freem(m);
579 }
580 } else
581 IPSTAT_INC(ips_fragmented);
582 }
583 }
584
585 if (error != 0)
586 IPSTAT_INC(ips_odropped);
587 else {
588 counter_u64_add(ro.ro_rt->rt_pksent, 1);
589 IPSTAT_INC(ips_forward);
590 IPSTAT_INC(ips_fastforward);
591 }
592 consumed:
593 RTFREE(ro.ro_rt);
594 return NULL;
595 drop:
596 if (m)
597 m_freem(m);
598 if (ro.ro_rt)
599 RTFREE(ro.ro_rt);
600 return NULL;
601 }
Cache object: ca30550a941f7e99c930b4e85af89756
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