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: src/sys/netinet/ip_fastfwd.c,v 1.46 2008/12/02 21:37:28 bz Exp $");
78
79 #include "opt_ipfw.h"
80 #include "opt_ipstealth.h"
81
82 #include <sys/param.h>
83 #include <sys/systm.h>
84 #include <sys/kernel.h>
85 #include <sys/malloc.h>
86 #include <sys/mbuf.h>
87 #include <sys/protosw.h>
88 #include <sys/socket.h>
89 #include <sys/sysctl.h>
90 #include <sys/vimage.h>
91
92 #include <net/pfil.h>
93 #include <net/if.h>
94 #include <net/if_types.h>
95 #include <net/if_var.h>
96 #include <net/if_dl.h>
97 #include <net/route.h>
98
99 #include <netinet/in.h>
100 #include <netinet/in_systm.h>
101 #include <netinet/in_var.h>
102 #include <netinet/ip.h>
103 #include <netinet/ip_var.h>
104 #include <netinet/ip_icmp.h>
105 #include <netinet/ip_options.h>
106 #include <netinet/vinet.h>
107
108 #include <machine/in_cksum.h>
109
110 #ifdef VIMAGE_GLOBALS
111 static int ipfastforward_active;
112 #endif
113 SYSCTL_V_INT(V_NET, vnet_inet, _net_inet_ip, OID_AUTO, fastforwarding,
114 CTLFLAG_RW, ipfastforward_active, 0, "Enable fast IP forwarding");
115
116 static struct sockaddr_in *
117 ip_findroute(struct route *ro, struct in_addr dest, struct mbuf *m)
118 {
119 INIT_VNET_INET(curvnet);
120 struct sockaddr_in *dst;
121 struct rtentry *rt;
122
123 /*
124 * Find route to destination.
125 */
126 bzero(ro, sizeof(*ro));
127 dst = (struct sockaddr_in *)&ro->ro_dst;
128 dst->sin_family = AF_INET;
129 dst->sin_len = sizeof(*dst);
130 dst->sin_addr.s_addr = dest.s_addr;
131 in_rtalloc_ign(ro, RTF_CLONING, M_GETFIB(m));
132
133 /*
134 * Route there and interface still up?
135 */
136 rt = ro->ro_rt;
137 if (rt && (rt->rt_flags & RTF_UP) &&
138 (rt->rt_ifp->if_flags & IFF_UP) &&
139 (rt->rt_ifp->if_drv_flags & IFF_DRV_RUNNING)) {
140 if (rt->rt_flags & RTF_GATEWAY)
141 dst = (struct sockaddr_in *)rt->rt_gateway;
142 } else {
143 V_ipstat.ips_noroute++;
144 V_ipstat.ips_cantforward++;
145 if (rt)
146 RTFREE(rt);
147 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0);
148 return NULL;
149 }
150 return dst;
151 }
152
153 /*
154 * Try to forward a packet based on the destination address.
155 * This is a fast path optimized for the plain forwarding case.
156 * If the packet is handled (and consumed) here then we return 1;
157 * otherwise 0 is returned and the packet should be delivered
158 * to ip_input for full processing.
159 */
160 struct mbuf *
161 ip_fastforward(struct mbuf *m)
162 {
163 INIT_VNET_INET(curvnet);
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 u_short sum, ip_len;
171 int error = 0;
172 int hlen, mtu;
173 #ifdef IPFIREWALL_FORWARD
174 struct m_tag *fwd_tag;
175 #endif
176
177 /*
178 * Are we active and forwarding packets?
179 */
180 if (!V_ipfastforward_active || !V_ipforwarding)
181 return m;
182
183 M_ASSERTVALID(m);
184 M_ASSERTPKTHDR(m);
185
186 ro.ro_rt = NULL;
187
188 /*
189 * Step 1: check for packet drop conditions (and sanity checks)
190 */
191
192 /*
193 * Is entire packet big enough?
194 */
195 if (m->m_pkthdr.len < sizeof(struct ip)) {
196 V_ipstat.ips_tooshort++;
197 goto drop;
198 }
199
200 /*
201 * Is first mbuf large enough for ip header and is header present?
202 */
203 if (m->m_len < sizeof (struct ip) &&
204 (m = m_pullup(m, sizeof (struct ip))) == NULL) {
205 V_ipstat.ips_toosmall++;
206 return NULL; /* mbuf already free'd */
207 }
208
209 ip = mtod(m, struct ip *);
210
211 /*
212 * Is it IPv4?
213 */
214 if (ip->ip_v != IPVERSION) {
215 V_ipstat.ips_badvers++;
216 goto drop;
217 }
218
219 /*
220 * Is IP header length correct and is it in first mbuf?
221 */
222 hlen = ip->ip_hl << 2;
223 if (hlen < sizeof(struct ip)) { /* minimum header length */
224 V_ipstat.ips_badlen++;
225 goto drop;
226 }
227 if (hlen > m->m_len) {
228 if ((m = m_pullup(m, hlen)) == NULL) {
229 V_ipstat.ips_badhlen++;
230 return NULL; /* mbuf already free'd */
231 }
232 ip = mtod(m, struct ip *);
233 }
234
235 /*
236 * Checksum correct?
237 */
238 if (m->m_pkthdr.csum_flags & CSUM_IP_CHECKED)
239 sum = !(m->m_pkthdr.csum_flags & CSUM_IP_VALID);
240 else {
241 if (hlen == sizeof(struct ip))
242 sum = in_cksum_hdr(ip);
243 else
244 sum = in_cksum(m, hlen);
245 }
246 if (sum) {
247 V_ipstat.ips_badsum++;
248 goto drop;
249 }
250
251 /*
252 * Remember that we have checked the IP header and found it valid.
253 */
254 m->m_pkthdr.csum_flags |= (CSUM_IP_CHECKED | CSUM_IP_VALID);
255
256 ip_len = ntohs(ip->ip_len);
257
258 /*
259 * Is IP length longer than packet we have got?
260 */
261 if (m->m_pkthdr.len < ip_len) {
262 V_ipstat.ips_tooshort++;
263 goto drop;
264 }
265
266 /*
267 * Is packet longer than IP header tells us? If yes, truncate packet.
268 */
269 if (m->m_pkthdr.len > ip_len) {
270 if (m->m_len == m->m_pkthdr.len) {
271 m->m_len = ip_len;
272 m->m_pkthdr.len = ip_len;
273 } else
274 m_adj(m, ip_len - m->m_pkthdr.len);
275 }
276
277 /*
278 * Is packet from or to 127/8?
279 */
280 if ((ntohl(ip->ip_dst.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET ||
281 (ntohl(ip->ip_src.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET) {
282 V_ipstat.ips_badaddr++;
283 goto drop;
284 }
285
286 #ifdef ALTQ
287 /*
288 * Is packet dropped by traffic conditioner?
289 */
290 if (altq_input != NULL && (*altq_input)(m, AF_INET) == 0)
291 goto drop;
292 #endif
293
294 /*
295 * Step 2: fallback conditions to normal ip_input path processing
296 */
297
298 /*
299 * Only IP packets without options
300 */
301 if (ip->ip_hl != (sizeof(struct ip) >> 2)) {
302 if (ip_doopts == 1)
303 return m;
304 else if (ip_doopts == 2) {
305 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_FILTER_PROHIB,
306 0, 0);
307 return NULL; /* mbuf already free'd */
308 }
309 /* else ignore IP options and continue */
310 }
311
312 /*
313 * Only unicast IP, not from loopback, no L2 or IP broadcast,
314 * no multicast, no INADDR_ANY
315 *
316 * XXX: Probably some of these checks could be direct drop
317 * conditions. However it is not clear whether there are some
318 * hacks or obscure behaviours which make it neccessary to
319 * let ip_input handle it. We play safe here and let ip_input
320 * deal with it until it is proven that we can directly drop it.
321 */
322 if ((m->m_flags & (M_BCAST|M_MCAST)) ||
323 (m->m_pkthdr.rcvif->if_flags & IFF_LOOPBACK) ||
324 ntohl(ip->ip_src.s_addr) == (u_long)INADDR_BROADCAST ||
325 ntohl(ip->ip_dst.s_addr) == (u_long)INADDR_BROADCAST ||
326 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
327 IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
328 IN_LINKLOCAL(ntohl(ip->ip_src.s_addr)) ||
329 IN_LINKLOCAL(ntohl(ip->ip_dst.s_addr)) ||
330 ip->ip_src.s_addr == INADDR_ANY ||
331 ip->ip_dst.s_addr == INADDR_ANY )
332 return m;
333
334 /*
335 * Is it for a local address on this host?
336 */
337 if (in_localip(ip->ip_dst))
338 return m;
339
340 V_ipstat.ips_total++;
341
342 /*
343 * Step 3: incoming packet firewall processing
344 */
345
346 /*
347 * Convert to host representation
348 */
349 ip->ip_len = ntohs(ip->ip_len);
350 ip->ip_off = ntohs(ip->ip_off);
351
352 odest.s_addr = dest.s_addr = ip->ip_dst.s_addr;
353
354 /*
355 * Run through list of ipfilter hooks for input packets
356 */
357 if (!PFIL_HOOKED(&inet_pfil_hook))
358 goto passin;
359
360 if (pfil_run_hooks(&inet_pfil_hook, &m, m->m_pkthdr.rcvif, PFIL_IN, NULL) ||
361 m == NULL)
362 goto drop;
363
364 M_ASSERTVALID(m);
365 M_ASSERTPKTHDR(m);
366
367 ip = mtod(m, struct ip *); /* m may have changed by pfil hook */
368 dest.s_addr = ip->ip_dst.s_addr;
369
370 /*
371 * Destination address changed?
372 */
373 if (odest.s_addr != dest.s_addr) {
374 /*
375 * Is it now for a local address on this host?
376 */
377 if (in_localip(dest))
378 goto forwardlocal;
379 /*
380 * Go on with new destination address
381 */
382 }
383 #ifdef IPFIREWALL_FORWARD
384 if (m->m_flags & M_FASTFWD_OURS) {
385 /*
386 * ipfw changed it for a local address on this host.
387 */
388 goto forwardlocal;
389 }
390 #endif /* IPFIREWALL_FORWARD */
391
392 passin:
393 /*
394 * Step 4: decrement TTL and look up route
395 */
396
397 /*
398 * Check TTL
399 */
400 #ifdef IPSTEALTH
401 if (!V_ipstealth) {
402 #endif
403 if (ip->ip_ttl <= IPTTLDEC) {
404 icmp_error(m, ICMP_TIMXCEED, ICMP_TIMXCEED_INTRANS, 0, 0);
405 return NULL; /* mbuf already free'd */
406 }
407
408 /*
409 * Decrement the TTL and incrementally change the IP header checksum.
410 * Don't bother doing this with hw checksum offloading, it's faster
411 * doing it right here.
412 */
413 ip->ip_ttl -= IPTTLDEC;
414 if (ip->ip_sum >= (u_int16_t) ~htons(IPTTLDEC << 8))
415 ip->ip_sum -= ~htons(IPTTLDEC << 8);
416 else
417 ip->ip_sum += htons(IPTTLDEC << 8);
418 #ifdef IPSTEALTH
419 }
420 #endif
421
422 /*
423 * Find route to destination.
424 */
425 if ((dst = ip_findroute(&ro, dest, m)) == NULL)
426 return NULL; /* icmp unreach already sent */
427 ifp = ro.ro_rt->rt_ifp;
428
429 /*
430 * Immediately drop blackholed traffic, and directed broadcasts
431 * for either the all-ones or all-zero subnet addresses on
432 * locally attached networks.
433 */
434 if ((ro.ro_rt->rt_flags & (RTF_BLACKHOLE|RTF_BROADCAST)) != 0)
435 goto drop;
436
437 /*
438 * Step 5: outgoing firewall packet processing
439 */
440
441 /*
442 * Run through list of hooks for output packets.
443 */
444 if (!PFIL_HOOKED(&inet_pfil_hook))
445 goto passout;
446
447 if (pfil_run_hooks(&inet_pfil_hook, &m, ifp, PFIL_OUT, NULL) || m == NULL) {
448 goto drop;
449 }
450
451 M_ASSERTVALID(m);
452 M_ASSERTPKTHDR(m);
453
454 ip = mtod(m, struct ip *);
455 dest.s_addr = ip->ip_dst.s_addr;
456
457 /*
458 * Destination address changed?
459 */
460 #ifndef IPFIREWALL_FORWARD
461 if (odest.s_addr != dest.s_addr) {
462 #else
463 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL);
464 if (odest.s_addr != dest.s_addr || fwd_tag != NULL) {
465 #endif /* IPFIREWALL_FORWARD */
466 /*
467 * Is it now for a local address on this host?
468 */
469 #ifndef IPFIREWALL_FORWARD
470 if (in_localip(dest)) {
471 #else
472 if (m->m_flags & M_FASTFWD_OURS || in_localip(dest)) {
473 #endif /* IPFIREWALL_FORWARD */
474 forwardlocal:
475 /*
476 * Return packet for processing by ip_input().
477 * Keep host byte order as expected at ip_input's
478 * "ours"-label.
479 */
480 m->m_flags |= M_FASTFWD_OURS;
481 if (ro.ro_rt)
482 RTFREE(ro.ro_rt);
483 return m;
484 }
485 /*
486 * Redo route lookup with new destination address
487 */
488 #ifdef IPFIREWALL_FORWARD
489 if (fwd_tag) {
490 dest.s_addr = ((struct sockaddr_in *)
491 (fwd_tag + 1))->sin_addr.s_addr;
492 m_tag_delete(m, fwd_tag);
493 }
494 #endif /* IPFIREWALL_FORWARD */
495 RTFREE(ro.ro_rt);
496 if ((dst = ip_findroute(&ro, dest, m)) == NULL)
497 return NULL; /* icmp unreach already sent */
498 ifp = ro.ro_rt->rt_ifp;
499 }
500
501 passout:
502 /*
503 * Step 6: send off the packet
504 */
505
506 /*
507 * Check if route is dampned (when ARP is unable to resolve)
508 */
509 if ((ro.ro_rt->rt_flags & RTF_REJECT) &&
510 (ro.ro_rt->rt_rmx.rmx_expire == 0 ||
511 time_uptime < ro.ro_rt->rt_rmx.rmx_expire)) {
512 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0);
513 goto consumed;
514 }
515
516 #ifndef ALTQ
517 /*
518 * Check if there is enough space in the interface queue
519 */
520 if ((ifp->if_snd.ifq_len + ip->ip_len / ifp->if_mtu + 1) >=
521 ifp->if_snd.ifq_maxlen) {
522 V_ipstat.ips_odropped++;
523 /* would send source quench here but that is depreciated */
524 goto drop;
525 }
526 #endif
527
528 /*
529 * Check if media link state of interface is not down
530 */
531 if (ifp->if_link_state == LINK_STATE_DOWN) {
532 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0);
533 goto consumed;
534 }
535
536 /*
537 * Check if packet fits MTU or if hardware will fragment for us
538 */
539 if (ro.ro_rt->rt_rmx.rmx_mtu)
540 mtu = min(ro.ro_rt->rt_rmx.rmx_mtu, ifp->if_mtu);
541 else
542 mtu = ifp->if_mtu;
543
544 if (ip->ip_len <= mtu ||
545 (ifp->if_hwassist & CSUM_FRAGMENT && (ip->ip_off & IP_DF) == 0)) {
546 /*
547 * Restore packet header fields to original values
548 */
549 ip->ip_len = htons(ip->ip_len);
550 ip->ip_off = htons(ip->ip_off);
551 /*
552 * Send off the packet via outgoing interface
553 */
554 error = (*ifp->if_output)(ifp, m,
555 (struct sockaddr *)dst, ro.ro_rt);
556 } else {
557 /*
558 * Handle EMSGSIZE with icmp reply needfrag for TCP MTU discovery
559 */
560 if (ip->ip_off & IP_DF) {
561 V_ipstat.ips_cantfrag++;
562 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_NEEDFRAG,
563 0, mtu);
564 goto consumed;
565 } else {
566 /*
567 * We have to fragment the packet
568 */
569 m->m_pkthdr.csum_flags |= CSUM_IP;
570 /*
571 * ip_fragment expects ip_len and ip_off in host byte
572 * order but returns all packets in network byte order
573 */
574 if (ip_fragment(ip, &m, mtu, ifp->if_hwassist,
575 (~ifp->if_hwassist & CSUM_DELAY_IP))) {
576 goto drop;
577 }
578 KASSERT(m != NULL, ("null mbuf and no error"));
579 /*
580 * Send off the fragments via outgoing interface
581 */
582 error = 0;
583 do {
584 m0 = m->m_nextpkt;
585 m->m_nextpkt = NULL;
586
587 error = (*ifp->if_output)(ifp, m,
588 (struct sockaddr *)dst, ro.ro_rt);
589 if (error)
590 break;
591 } while ((m = m0) != NULL);
592 if (error) {
593 /* Reclaim remaining fragments */
594 for (m = m0; m; m = m0) {
595 m0 = m->m_nextpkt;
596 m_freem(m);
597 }
598 } else
599 V_ipstat.ips_fragmented++;
600 }
601 }
602
603 if (error != 0)
604 V_ipstat.ips_odropped++;
605 else {
606 ro.ro_rt->rt_rmx.rmx_pksent++;
607 V_ipstat.ips_forward++;
608 V_ipstat.ips_fastforward++;
609 }
610 consumed:
611 RTFREE(ro.ro_rt);
612 return NULL;
613 drop:
614 if (m)
615 m_freem(m);
616 if (ro.ro_rt)
617 RTFREE(ro.ro_rt);
618 return NULL;
619 }
620
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