1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1982, 1986, 1988, 1993
5 * The Regents of the University of California. All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the University nor the names of its 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 THE REGENTS 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 THE REGENTS 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 * @(#)ip_icmp.c 8.2 (Berkeley) 1/4/94
32 */
33
34 #include <sys/cdefs.h>
35 __FBSDID("$FreeBSD: stable/12/sys/netinet/ip_icmp.c 371883 2022-04-07 13:15:58Z git2svn $");
36
37 #include "opt_inet.h"
38
39 #include <sys/param.h>
40 #include <sys/systm.h>
41 #include <sys/mbuf.h>
42 #include <sys/protosw.h>
43 #include <sys/socket.h>
44 #include <sys/time.h>
45 #include <sys/kernel.h>
46 #include <sys/lock.h>
47 #include <sys/rmlock.h>
48 #include <sys/sysctl.h>
49 #include <sys/syslog.h>
50
51 #include <net/if.h>
52 #include <net/if_var.h>
53 #include <net/if_types.h>
54 #include <net/route.h>
55 #include <net/vnet.h>
56
57 #include <netinet/in.h>
58 #include <netinet/in_fib.h>
59 #include <netinet/in_pcb.h>
60 #include <netinet/in_systm.h>
61 #include <netinet/in_var.h>
62 #include <netinet/ip.h>
63 #include <netinet/ip_icmp.h>
64 #include <netinet/ip_var.h>
65 #include <netinet/ip_options.h>
66 #include <netinet/sctp.h>
67 #include <netinet/tcp.h>
68 #include <netinet/tcp_var.h>
69 #include <netinet/tcpip.h>
70 #include <netinet/icmp_var.h>
71
72
73 #ifdef INET
74
75 #include <machine/in_cksum.h>
76
77 #include <security/mac/mac_framework.h>
78 #endif /* INET */
79
80 /*
81 * ICMP routines: error generation, receive packet processing, and
82 * routines to turnaround packets back to the originator, and
83 * host table maintenance routines.
84 */
85 VNET_DEFINE_STATIC(int, icmplim) = 200;
86 #define V_icmplim VNET(icmplim)
87 SYSCTL_INT(_net_inet_icmp, ICMPCTL_ICMPLIM, icmplim, CTLFLAG_VNET | CTLFLAG_RW,
88 &VNET_NAME(icmplim), 0,
89 "Maximum number of ICMP responses per second");
90
91 VNET_DEFINE_STATIC(int, icmplim_curr_jitter) = 0;
92 #define V_icmplim_curr_jitter VNET(icmplim_curr_jitter)
93 VNET_DEFINE_STATIC(int, icmplim_jitter) = 16;
94 #define V_icmplim_jitter VNET(icmplim_jitter)
95 SYSCTL_INT(_net_inet_icmp, OID_AUTO, icmplim_jitter, CTLFLAG_VNET | CTLFLAG_RW,
96 &VNET_NAME(icmplim_jitter), 0,
97 "Random icmplim jitter adjustment limit");
98
99 VNET_DEFINE_STATIC(int, icmplim_output) = 1;
100 #define V_icmplim_output VNET(icmplim_output)
101 SYSCTL_INT(_net_inet_icmp, OID_AUTO, icmplim_output, CTLFLAG_VNET | CTLFLAG_RW,
102 &VNET_NAME(icmplim_output), 0,
103 "Enable logging of ICMP response rate limiting");
104
105 #ifdef INET
106 VNET_PCPUSTAT_DEFINE(struct icmpstat, icmpstat);
107 VNET_PCPUSTAT_SYSINIT(icmpstat);
108 SYSCTL_VNET_PCPUSTAT(_net_inet_icmp, ICMPCTL_STATS, stats, struct icmpstat,
109 icmpstat, "ICMP statistics (struct icmpstat, netinet/icmp_var.h)");
110
111 #ifdef VIMAGE
112 VNET_PCPUSTAT_SYSUNINIT(icmpstat);
113 #endif /* VIMAGE */
114
115 VNET_DEFINE_STATIC(int, icmpmaskrepl) = 0;
116 #define V_icmpmaskrepl VNET(icmpmaskrepl)
117 SYSCTL_INT(_net_inet_icmp, ICMPCTL_MASKREPL, maskrepl, CTLFLAG_VNET | CTLFLAG_RW,
118 &VNET_NAME(icmpmaskrepl), 0,
119 "Reply to ICMP Address Mask Request packets");
120
121 VNET_DEFINE_STATIC(u_int, icmpmaskfake) = 0;
122 #define V_icmpmaskfake VNET(icmpmaskfake)
123 SYSCTL_UINT(_net_inet_icmp, OID_AUTO, maskfake, CTLFLAG_VNET | CTLFLAG_RW,
124 &VNET_NAME(icmpmaskfake), 0,
125 "Fake reply to ICMP Address Mask Request packets");
126
127 VNET_DEFINE(int, drop_redirect) = 0;
128 #define V_drop_redirect VNET(drop_redirect)
129 SYSCTL_INT(_net_inet_icmp, OID_AUTO, drop_redirect, CTLFLAG_VNET | CTLFLAG_RW,
130 &VNET_NAME(drop_redirect), 0,
131 "Ignore ICMP redirects");
132
133 VNET_DEFINE_STATIC(int, log_redirect) = 0;
134 #define V_log_redirect VNET(log_redirect)
135 SYSCTL_INT(_net_inet_icmp, OID_AUTO, log_redirect, CTLFLAG_VNET | CTLFLAG_RW,
136 &VNET_NAME(log_redirect), 0,
137 "Log ICMP redirects to the console");
138
139 VNET_DEFINE_STATIC(char, reply_src[IFNAMSIZ]);
140 #define V_reply_src VNET(reply_src)
141 SYSCTL_STRING(_net_inet_icmp, OID_AUTO, reply_src, CTLFLAG_VNET | CTLFLAG_RW,
142 &VNET_NAME(reply_src), IFNAMSIZ,
143 "ICMP reply source for non-local packets");
144
145 VNET_DEFINE_STATIC(int, icmp_rfi) = 0;
146 #define V_icmp_rfi VNET(icmp_rfi)
147 SYSCTL_INT(_net_inet_icmp, OID_AUTO, reply_from_interface, CTLFLAG_VNET | CTLFLAG_RW,
148 &VNET_NAME(icmp_rfi), 0,
149 "ICMP reply from incoming interface for non-local packets");
150 /* Router requirements RFC 1812 section 4.3.2.3 requires 576 - 28. */
151 VNET_DEFINE_STATIC(int, icmp_quotelen) = 548;
152 #define V_icmp_quotelen VNET(icmp_quotelen)
153 SYSCTL_INT(_net_inet_icmp, OID_AUTO, quotelen, CTLFLAG_VNET | CTLFLAG_RW,
154 &VNET_NAME(icmp_quotelen), 0,
155 "Number of bytes from original packet to quote in ICMP reply");
156
157 VNET_DEFINE_STATIC(int, icmpbmcastecho) = 0;
158 #define V_icmpbmcastecho VNET(icmpbmcastecho)
159 SYSCTL_INT(_net_inet_icmp, OID_AUTO, bmcastecho, CTLFLAG_VNET | CTLFLAG_RW,
160 &VNET_NAME(icmpbmcastecho), 0,
161 "Reply to multicast ICMP Echo Request and Timestamp packets");
162
163 VNET_DEFINE_STATIC(int, icmptstamprepl) = 1;
164 #define V_icmptstamprepl VNET(icmptstamprepl)
165 SYSCTL_INT(_net_inet_icmp, OID_AUTO, tstamprepl, CTLFLAG_VNET | CTLFLAG_RW,
166 &VNET_NAME(icmptstamprepl), 0,
167 "Respond to ICMP Timestamp packets");
168
169 VNET_DEFINE_STATIC(int, error_keeptags) = 0;
170 #define V_error_keeptags VNET(error_keeptags)
171 SYSCTL_INT(_net_inet_icmp, OID_AUTO, error_keeptags, CTLFLAG_VNET | CTLFLAG_RW,
172 &VNET_NAME(error_keeptags), 0,
173 "ICMP error response keeps copy of mbuf_tags of original packet");
174
175 #ifdef ICMPPRINTFS
176 int icmpprintfs = 0;
177 #endif
178
179 static void icmp_reflect(struct mbuf *);
180 static void icmp_send(struct mbuf *, struct mbuf *);
181
182 extern struct protosw inetsw[];
183
184 /*
185 * Kernel module interface for updating icmpstat. The argument is an index
186 * into icmpstat treated as an array of u_long. While this encodes the
187 * general layout of icmpstat into the caller, it doesn't encode its
188 * location, so that future changes to add, for example, per-CPU stats
189 * support won't cause binary compatibility problems for kernel modules.
190 */
191 void
kmod_icmpstat_inc(int statnum)192 kmod_icmpstat_inc(int statnum)
193 {
194
195 counter_u64_add(VNET(icmpstat)[statnum], 1);
196 }
197
198 /*
199 * Generate an error packet of type error
200 * in response to bad packet ip.
201 */
202 void
icmp_error(struct mbuf * n,int type,int code,uint32_t dest,int mtu)203 icmp_error(struct mbuf *n, int type, int code, uint32_t dest, int mtu)
204 {
205 struct ip *oip, *nip;
206 struct icmp *icp;
207 struct mbuf *m;
208 unsigned icmplen, icmpelen, nlen, oiphlen;
209
210 KASSERT((u_int)type <= ICMP_MAXTYPE, ("%s: illegal ICMP type",
211 __func__));
212
213 if (type != ICMP_REDIRECT)
214 ICMPSTAT_INC(icps_error);
215 /*
216 * Don't send error:
217 * if the original packet was encrypted.
218 * if not the first fragment of message.
219 * in response to a multicast or broadcast packet.
220 * if the old packet protocol was an ICMP error message.
221 */
222 if (n->m_flags & M_DECRYPTED)
223 goto freeit;
224 if (n->m_flags & (M_BCAST|M_MCAST))
225 goto freeit;
226
227 /* Drop if IP header plus 8 bytes is not contiguous in first mbuf. */
228 if (n->m_len < sizeof(struct ip) + ICMP_MINLEN)
229 goto freeit;
230 oip = mtod(n, struct ip *);
231 oiphlen = oip->ip_hl << 2;
232 if (n->m_len < oiphlen + ICMP_MINLEN)
233 goto freeit;
234 #ifdef ICMPPRINTFS
235 if (icmpprintfs)
236 printf("icmp_error(%p, %x, %d)\n", oip, type, code);
237 #endif
238 if (oip->ip_off & htons(~(IP_MF|IP_DF)))
239 goto freeit;
240 if (oip->ip_p == IPPROTO_ICMP && type != ICMP_REDIRECT &&
241 !ICMP_INFOTYPE(((struct icmp *)((caddr_t)oip +
242 oiphlen))->icmp_type)) {
243 ICMPSTAT_INC(icps_oldicmp);
244 goto freeit;
245 }
246 /*
247 * Calculate length to quote from original packet and
248 * prevent the ICMP mbuf from overflowing.
249 * Unfortunately this is non-trivial since ip_forward()
250 * sends us truncated packets.
251 */
252 nlen = m_length(n, NULL);
253 if (oip->ip_p == IPPROTO_TCP) {
254 struct tcphdr *th;
255 int tcphlen;
256
257 if (oiphlen + sizeof(struct tcphdr) > n->m_len &&
258 n->m_next == NULL)
259 goto stdreply;
260 if (n->m_len < oiphlen + sizeof(struct tcphdr) &&
261 (n = m_pullup(n, oiphlen + sizeof(struct tcphdr))) == NULL)
262 goto freeit;
263 oip = mtod(n, struct ip *);
264 th = mtodo(n, oiphlen);
265 tcphlen = th->th_off << 2;
266 if (tcphlen < sizeof(struct tcphdr))
267 goto freeit;
268 if (ntohs(oip->ip_len) < oiphlen + tcphlen)
269 goto freeit;
270 if (oiphlen + tcphlen > n->m_len && n->m_next == NULL)
271 goto stdreply;
272 if (n->m_len < oiphlen + tcphlen &&
273 (n = m_pullup(n, oiphlen + tcphlen)) == NULL)
274 goto freeit;
275 icmpelen = max(tcphlen, min(V_icmp_quotelen,
276 ntohs(oip->ip_len) - oiphlen));
277 } else if (oip->ip_p == IPPROTO_SCTP) {
278 struct sctphdr *sh;
279 struct sctp_chunkhdr *ch;
280
281 if (ntohs(oip->ip_len) < oiphlen + sizeof(struct sctphdr))
282 goto stdreply;
283 if (oiphlen + sizeof(struct sctphdr) > n->m_len &&
284 n->m_next == NULL)
285 goto stdreply;
286 if (n->m_len < oiphlen + sizeof(struct sctphdr) &&
287 (n = m_pullup(n, oiphlen + sizeof(struct sctphdr))) == NULL)
288 goto freeit;
289 oip = mtod(n, struct ip *);
290 icmpelen = max(sizeof(struct sctphdr),
291 min(V_icmp_quotelen, ntohs(oip->ip_len) - oiphlen));
292 sh = mtodo(n, oiphlen);
293 if (ntohl(sh->v_tag) == 0 &&
294 ntohs(oip->ip_len) >= oiphlen +
295 sizeof(struct sctphdr) + 8 &&
296 (n->m_len >= oiphlen + sizeof(struct sctphdr) + 8 ||
297 n->m_next != NULL)) {
298 if (n->m_len < oiphlen + sizeof(struct sctphdr) + 8 &&
299 (n = m_pullup(n, oiphlen +
300 sizeof(struct sctphdr) + 8)) == NULL)
301 goto freeit;
302 oip = mtod(n, struct ip *);
303 sh = mtodo(n, oiphlen);
304 ch = (struct sctp_chunkhdr *)(sh + 1);
305 if (ch->chunk_type == SCTP_INITIATION) {
306 icmpelen = max(sizeof(struct sctphdr) + 8,
307 min(V_icmp_quotelen, ntohs(oip->ip_len) -
308 oiphlen));
309 }
310 }
311 } else
312 stdreply: icmpelen = max(8, min(V_icmp_quotelen, ntohs(oip->ip_len) -
313 oiphlen));
314
315 icmplen = min(oiphlen + icmpelen, nlen);
316 if (icmplen < sizeof(struct ip))
317 goto freeit;
318
319 if (MHLEN > sizeof(struct ip) + ICMP_MINLEN + icmplen)
320 m = m_gethdr(M_NOWAIT, MT_DATA);
321 else
322 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR);
323 if (m == NULL)
324 goto freeit;
325 #ifdef MAC
326 mac_netinet_icmp_reply(n, m);
327 #endif
328 icmplen = min(icmplen, M_TRAILINGSPACE(m) -
329 sizeof(struct ip) - ICMP_MINLEN);
330 m_align(m, sizeof(struct ip) + ICMP_MINLEN + icmplen);
331 m->m_data += sizeof(struct ip);
332 m->m_len = ICMP_MINLEN + icmplen;
333
334 /* XXX MRT make the outgoing packet use the same FIB
335 * that was associated with the incoming packet
336 */
337 M_SETFIB(m, M_GETFIB(n));
338 icp = mtod(m, struct icmp *);
339 ICMPSTAT_INC(icps_outhist[type]);
340 icp->icmp_type = type;
341 if (type == ICMP_REDIRECT)
342 icp->icmp_gwaddr.s_addr = dest;
343 else {
344 icp->icmp_void = 0;
345 /*
346 * The following assignments assume an overlay with the
347 * just zeroed icmp_void field.
348 */
349 if (type == ICMP_PARAMPROB) {
350 icp->icmp_pptr = code;
351 code = 0;
352 } else if (type == ICMP_UNREACH &&
353 code == ICMP_UNREACH_NEEDFRAG && mtu) {
354 icp->icmp_nextmtu = htons(mtu);
355 }
356 }
357 icp->icmp_code = code;
358
359 /*
360 * Copy the quotation into ICMP message and
361 * convert quoted IP header back to network representation.
362 */
363 m_copydata(n, 0, icmplen, (caddr_t)&icp->icmp_ip);
364 nip = &icp->icmp_ip;
365
366 /*
367 * Set up ICMP message mbuf and copy old IP header (without options
368 * in front of ICMP message.
369 * If the original mbuf was meant to bypass the firewall, the error
370 * reply should bypass as well.
371 */
372 m->m_flags |= n->m_flags & M_SKIP_FIREWALL;
373 KASSERT(M_LEADINGSPACE(m) >= sizeof(struct ip),
374 ("insufficient space for ip header"));
375 m->m_data -= sizeof(struct ip);
376 m->m_len += sizeof(struct ip);
377 m->m_pkthdr.len = m->m_len;
378 m->m_pkthdr.rcvif = n->m_pkthdr.rcvif;
379 nip = mtod(m, struct ip *);
380 bcopy((caddr_t)oip, (caddr_t)nip, sizeof(struct ip));
381 nip->ip_len = htons(m->m_len);
382 nip->ip_v = IPVERSION;
383 nip->ip_hl = 5;
384 nip->ip_p = IPPROTO_ICMP;
385 nip->ip_tos = 0;
386 nip->ip_off = 0;
387
388 if (V_error_keeptags)
389 m_tag_copy_chain(m, n, M_NOWAIT);
390
391 icmp_reflect(m);
392
393 freeit:
394 m_freem(n);
395 }
396
397 /*
398 * Process a received ICMP message.
399 */
400 int
icmp_input(struct mbuf ** mp,int * offp,int proto)401 icmp_input(struct mbuf **mp, int *offp, int proto)
402 {
403 struct icmp *icp;
404 struct in_ifaddr *ia;
405 struct mbuf *m = *mp;
406 struct ip *ip = mtod(m, struct ip *);
407 struct sockaddr_in icmpsrc, icmpdst, icmpgw;
408 int hlen = *offp;
409 int icmplen = ntohs(ip->ip_len) - *offp;
410 int i, code;
411 void (*ctlfunc)(int, struct sockaddr *, void *);
412 int fibnum;
413
414 *mp = NULL;
415
416 /*
417 * Locate icmp structure in mbuf, and check
418 * that not corrupted and of at least minimum length.
419 */
420 #ifdef ICMPPRINTFS
421 if (icmpprintfs) {
422 char srcbuf[INET_ADDRSTRLEN];
423 char dstbuf[INET_ADDRSTRLEN];
424
425 printf("icmp_input from %s to %s, len %d\n",
426 inet_ntoa_r(ip->ip_src, srcbuf),
427 inet_ntoa_r(ip->ip_dst, dstbuf), icmplen);
428 }
429 #endif
430 NET_EPOCH_ENTER();
431 if (icmplen < ICMP_MINLEN) {
432 ICMPSTAT_INC(icps_tooshort);
433 goto freeit;
434 }
435 i = hlen + min(icmplen, ICMP_ADVLENMIN);
436 if (m->m_len < i && (m = m_pullup(m, i)) == NULL) {
437 ICMPSTAT_INC(icps_tooshort);
438 NET_EPOCH_EXIT();
439 return (IPPROTO_DONE);
440 }
441 ip = mtod(m, struct ip *);
442 m->m_len -= hlen;
443 m->m_data += hlen;
444 icp = mtod(m, struct icmp *);
445 if (in_cksum(m, icmplen)) {
446 ICMPSTAT_INC(icps_checksum);
447 goto freeit;
448 }
449 m->m_len += hlen;
450 m->m_data -= hlen;
451
452 #ifdef ICMPPRINTFS
453 if (icmpprintfs)
454 printf("icmp_input, type %d code %d\n", icp->icmp_type,
455 icp->icmp_code);
456 #endif
457
458 /*
459 * Message type specific processing.
460 */
461 if (icp->icmp_type > ICMP_MAXTYPE)
462 goto raw;
463
464 /* Initialize */
465 bzero(&icmpsrc, sizeof(icmpsrc));
466 icmpsrc.sin_len = sizeof(struct sockaddr_in);
467 icmpsrc.sin_family = AF_INET;
468 bzero(&icmpdst, sizeof(icmpdst));
469 icmpdst.sin_len = sizeof(struct sockaddr_in);
470 icmpdst.sin_family = AF_INET;
471 bzero(&icmpgw, sizeof(icmpgw));
472 icmpgw.sin_len = sizeof(struct sockaddr_in);
473 icmpgw.sin_family = AF_INET;
474
475 ICMPSTAT_INC(icps_inhist[icp->icmp_type]);
476 code = icp->icmp_code;
477 switch (icp->icmp_type) {
478
479 case ICMP_UNREACH:
480 switch (code) {
481 case ICMP_UNREACH_NET:
482 case ICMP_UNREACH_HOST:
483 case ICMP_UNREACH_SRCFAIL:
484 case ICMP_UNREACH_NET_UNKNOWN:
485 case ICMP_UNREACH_HOST_UNKNOWN:
486 case ICMP_UNREACH_ISOLATED:
487 case ICMP_UNREACH_TOSNET:
488 case ICMP_UNREACH_TOSHOST:
489 case ICMP_UNREACH_HOST_PRECEDENCE:
490 case ICMP_UNREACH_PRECEDENCE_CUTOFF:
491 code = PRC_UNREACH_NET;
492 break;
493
494 case ICMP_UNREACH_NEEDFRAG:
495 code = PRC_MSGSIZE;
496 break;
497
498 /*
499 * RFC 1122, Sections 3.2.2.1 and 4.2.3.9.
500 * Treat subcodes 2,3 as immediate RST
501 */
502 case ICMP_UNREACH_PROTOCOL:
503 code = PRC_UNREACH_PROTOCOL;
504 break;
505 case ICMP_UNREACH_PORT:
506 code = PRC_UNREACH_PORT;
507 break;
508
509 case ICMP_UNREACH_NET_PROHIB:
510 case ICMP_UNREACH_HOST_PROHIB:
511 case ICMP_UNREACH_FILTER_PROHIB:
512 code = PRC_UNREACH_ADMIN_PROHIB;
513 break;
514
515 default:
516 goto badcode;
517 }
518 goto deliver;
519
520 case ICMP_TIMXCEED:
521 if (code > 1)
522 goto badcode;
523 code += PRC_TIMXCEED_INTRANS;
524 goto deliver;
525
526 case ICMP_PARAMPROB:
527 if (code > 1)
528 goto badcode;
529 code = PRC_PARAMPROB;
530 deliver:
531 /*
532 * Problem with datagram; advise higher level routines.
533 */
534 if (icmplen < ICMP_ADVLENMIN || icmplen < ICMP_ADVLEN(icp) ||
535 icp->icmp_ip.ip_hl < (sizeof(struct ip) >> 2)) {
536 ICMPSTAT_INC(icps_badlen);
537 goto freeit;
538 }
539 /* Discard ICMP's in response to multicast packets */
540 if (IN_MULTICAST(ntohl(icp->icmp_ip.ip_dst.s_addr)))
541 goto badcode;
542 #ifdef ICMPPRINTFS
543 if (icmpprintfs)
544 printf("deliver to protocol %d\n", icp->icmp_ip.ip_p);
545 #endif
546 icmpsrc.sin_addr = icp->icmp_ip.ip_dst;
547 /*
548 * XXX if the packet contains [IPv4 AH TCP], we can't make a
549 * notification to TCP layer.
550 */
551 i = sizeof(struct ip) + min(icmplen, ICMP_ADVLENPREF(icp));
552 ip_stripoptions(m);
553 if (m->m_len < i && (m = m_pullup(m, i)) == NULL) {
554 /* This should actually not happen */
555 ICMPSTAT_INC(icps_tooshort);
556 NET_EPOCH_EXIT();
557 return (IPPROTO_DONE);
558 }
559 ip = mtod(m, struct ip *);
560 icp = (struct icmp *)(ip + 1);
561 /*
562 * The upper layer handler can rely on:
563 * - The outer IP header has no options.
564 * - The outer IP header, the ICMP header, the inner IP header,
565 * and the first n bytes of the inner payload are contiguous.
566 * n is at least 8, but might be larger based on
567 * ICMP_ADVLENPREF. See its definition in ip_icmp.h.
568 */
569 ctlfunc = inetsw[ip_protox[icp->icmp_ip.ip_p]].pr_ctlinput;
570 if (ctlfunc)
571 (*ctlfunc)(code, (struct sockaddr *)&icmpsrc,
572 (void *)&icp->icmp_ip);
573 break;
574
575 badcode:
576 ICMPSTAT_INC(icps_badcode);
577 break;
578
579 case ICMP_ECHO:
580 if (!V_icmpbmcastecho
581 && (m->m_flags & (M_MCAST | M_BCAST)) != 0) {
582 ICMPSTAT_INC(icps_bmcastecho);
583 break;
584 }
585 if (badport_bandlim(BANDLIM_ICMP_ECHO) < 0)
586 goto freeit;
587 icp->icmp_type = ICMP_ECHOREPLY;
588 goto reflect;
589
590 case ICMP_TSTAMP:
591 if (V_icmptstamprepl == 0)
592 break;
593 if (!V_icmpbmcastecho
594 && (m->m_flags & (M_MCAST | M_BCAST)) != 0) {
595 ICMPSTAT_INC(icps_bmcasttstamp);
596 break;
597 }
598 if (icmplen < ICMP_TSLEN) {
599 ICMPSTAT_INC(icps_badlen);
600 break;
601 }
602 if (badport_bandlim(BANDLIM_ICMP_TSTAMP) < 0)
603 goto freeit;
604 icp->icmp_type = ICMP_TSTAMPREPLY;
605 icp->icmp_rtime = iptime();
606 icp->icmp_ttime = icp->icmp_rtime; /* bogus, do later! */
607 goto reflect;
608
609 case ICMP_MASKREQ:
610 if (V_icmpmaskrepl == 0)
611 break;
612 /*
613 * We are not able to respond with all ones broadcast
614 * unless we receive it over a point-to-point interface.
615 */
616 if (icmplen < ICMP_MASKLEN)
617 break;
618 switch (ip->ip_dst.s_addr) {
619
620 case INADDR_BROADCAST:
621 case INADDR_ANY:
622 icmpdst.sin_addr = ip->ip_src;
623 break;
624
625 default:
626 icmpdst.sin_addr = ip->ip_dst;
627 }
628 ia = (struct in_ifaddr *)ifaof_ifpforaddr(
629 (struct sockaddr *)&icmpdst, m->m_pkthdr.rcvif);
630 if (ia == NULL)
631 break;
632 if (ia->ia_ifp == NULL)
633 break;
634 icp->icmp_type = ICMP_MASKREPLY;
635 if (V_icmpmaskfake == 0)
636 icp->icmp_mask = ia->ia_sockmask.sin_addr.s_addr;
637 else
638 icp->icmp_mask = V_icmpmaskfake;
639 if (ip->ip_src.s_addr == 0) {
640 if (ia->ia_ifp->if_flags & IFF_BROADCAST)
641 ip->ip_src = satosin(&ia->ia_broadaddr)->sin_addr;
642 else if (ia->ia_ifp->if_flags & IFF_POINTOPOINT)
643 ip->ip_src = satosin(&ia->ia_dstaddr)->sin_addr;
644 }
645 reflect:
646 ICMPSTAT_INC(icps_reflect);
647 ICMPSTAT_INC(icps_outhist[icp->icmp_type]);
648 icmp_reflect(m);
649 NET_EPOCH_EXIT();
650 return (IPPROTO_DONE);
651
652 case ICMP_REDIRECT:
653 if (V_log_redirect) {
654 u_long src, dst, gw;
655
656 src = ntohl(ip->ip_src.s_addr);
657 dst = ntohl(icp->icmp_ip.ip_dst.s_addr);
658 gw = ntohl(icp->icmp_gwaddr.s_addr);
659 printf("icmp redirect from %d.%d.%d.%d: "
660 "%d.%d.%d.%d => %d.%d.%d.%d\n",
661 (int)(src >> 24), (int)((src >> 16) & 0xff),
662 (int)((src >> 8) & 0xff), (int)(src & 0xff),
663 (int)(dst >> 24), (int)((dst >> 16) & 0xff),
664 (int)((dst >> 8) & 0xff), (int)(dst & 0xff),
665 (int)(gw >> 24), (int)((gw >> 16) & 0xff),
666 (int)((gw >> 8) & 0xff), (int)(gw & 0xff));
667 }
668 /*
669 * RFC1812 says we must ignore ICMP redirects if we
670 * are acting as router.
671 */
672 if (V_drop_redirect || V_ipforwarding)
673 break;
674 if (code > 3)
675 goto badcode;
676 if (icmplen < ICMP_ADVLENMIN || icmplen < ICMP_ADVLEN(icp) ||
677 icp->icmp_ip.ip_hl < (sizeof(struct ip) >> 2)) {
678 ICMPSTAT_INC(icps_badlen);
679 break;
680 }
681 /*
682 * Short circuit routing redirects to force
683 * immediate change in the kernel's routing
684 * tables. The message is also handed to anyone
685 * listening on a raw socket (e.g. the routing
686 * daemon for use in updating its tables).
687 */
688 icmpgw.sin_addr = ip->ip_src;
689 icmpdst.sin_addr = icp->icmp_gwaddr;
690 #ifdef ICMPPRINTFS
691 if (icmpprintfs) {
692 char dstbuf[INET_ADDRSTRLEN];
693 char gwbuf[INET_ADDRSTRLEN];
694
695 printf("redirect dst %s to %s\n",
696 inet_ntoa_r(icp->icmp_ip.ip_dst, dstbuf),
697 inet_ntoa_r(icp->icmp_gwaddr, gwbuf));
698 }
699 #endif
700 icmpsrc.sin_addr = icp->icmp_ip.ip_dst;
701 for ( fibnum = 0; fibnum < rt_numfibs; fibnum++) {
702 in_rtredirect((struct sockaddr *)&icmpsrc,
703 (struct sockaddr *)&icmpdst,
704 (struct sockaddr *)0, RTF_GATEWAY | RTF_HOST,
705 (struct sockaddr *)&icmpgw, fibnum);
706 }
707 pfctlinput(PRC_REDIRECT_HOST, (struct sockaddr *)&icmpsrc);
708 break;
709
710 /*
711 * No kernel processing for the following;
712 * just fall through to send to raw listener.
713 */
714 case ICMP_ECHOREPLY:
715 case ICMP_ROUTERADVERT:
716 case ICMP_ROUTERSOLICIT:
717 case ICMP_TSTAMPREPLY:
718 case ICMP_IREQREPLY:
719 case ICMP_MASKREPLY:
720 case ICMP_SOURCEQUENCH:
721 default:
722 break;
723 }
724
725 raw:
726 NET_EPOCH_EXIT();
727 *mp = m;
728 rip_input(mp, offp, proto);
729 return (IPPROTO_DONE);
730
731 freeit:
732 NET_EPOCH_EXIT();
733 m_freem(m);
734 return (IPPROTO_DONE);
735 }
736
737 /*
738 * Reflect the ip packet back to the source
739 */
740 static void
icmp_reflect(struct mbuf * m)741 icmp_reflect(struct mbuf *m)
742 {
743 struct rm_priotracker in_ifa_tracker;
744 struct ip *ip = mtod(m, struct ip *);
745 struct ifaddr *ifa;
746 struct ifnet *ifp;
747 struct in_ifaddr *ia;
748 struct in_addr t;
749 struct nhop4_extended nh_ext;
750 struct mbuf *opts = NULL;
751 int optlen = (ip->ip_hl << 2) - sizeof(struct ip);
752
753 if (IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
754 IN_EXPERIMENTAL(ntohl(ip->ip_src.s_addr)) ||
755 IN_ZERONET(ntohl(ip->ip_src.s_addr)) ) {
756 m_freem(m); /* Bad return address */
757 ICMPSTAT_INC(icps_badaddr);
758 goto done; /* Ip_output() will check for broadcast */
759 }
760
761 t = ip->ip_dst;
762 ip->ip_dst = ip->ip_src;
763
764 /*
765 * Source selection for ICMP replies:
766 *
767 * If the incoming packet was addressed directly to one of our
768 * own addresses, use dst as the src for the reply.
769 */
770 IN_IFADDR_RLOCK(&in_ifa_tracker);
771 LIST_FOREACH(ia, INADDR_HASH(t.s_addr), ia_hash) {
772 if (t.s_addr == IA_SIN(ia)->sin_addr.s_addr) {
773 t = IA_SIN(ia)->sin_addr;
774 IN_IFADDR_RUNLOCK(&in_ifa_tracker);
775 goto match;
776 }
777 }
778 IN_IFADDR_RUNLOCK(&in_ifa_tracker);
779
780 /*
781 * If the incoming packet was addressed to one of our broadcast
782 * addresses, use the first non-broadcast address which corresponds
783 * to the incoming interface.
784 */
785 ifp = m->m_pkthdr.rcvif;
786 if (ifp != NULL && ifp->if_flags & IFF_BROADCAST) {
787 IF_ADDR_RLOCK(ifp);
788 CK_STAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
789 if (ifa->ifa_addr->sa_family != AF_INET)
790 continue;
791 ia = ifatoia(ifa);
792 if (satosin(&ia->ia_broadaddr)->sin_addr.s_addr ==
793 t.s_addr) {
794 t = IA_SIN(ia)->sin_addr;
795 IF_ADDR_RUNLOCK(ifp);
796 goto match;
797 }
798 }
799 IF_ADDR_RUNLOCK(ifp);
800 }
801 /*
802 * If the packet was transiting through us, use the address of
803 * the interface the packet came through in. If that interface
804 * doesn't have a suitable IP address, the normal selection
805 * criteria apply.
806 */
807 if (V_icmp_rfi && ifp != NULL) {
808 IF_ADDR_RLOCK(ifp);
809 CK_STAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
810 if (ifa->ifa_addr->sa_family != AF_INET)
811 continue;
812 ia = ifatoia(ifa);
813 t = IA_SIN(ia)->sin_addr;
814 IF_ADDR_RUNLOCK(ifp);
815 goto match;
816 }
817 IF_ADDR_RUNLOCK(ifp);
818 }
819 /*
820 * If the incoming packet was not addressed directly to us, use
821 * designated interface for icmp replies specified by sysctl
822 * net.inet.icmp.reply_src (default not set). Otherwise continue
823 * with normal source selection.
824 */
825 if (V_reply_src[0] != '\0' && (ifp = ifunit(V_reply_src))) {
826 IF_ADDR_RLOCK(ifp);
827 CK_STAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
828 if (ifa->ifa_addr->sa_family != AF_INET)
829 continue;
830 ia = ifatoia(ifa);
831 t = IA_SIN(ia)->sin_addr;
832 IF_ADDR_RUNLOCK(ifp);
833 goto match;
834 }
835 IF_ADDR_RUNLOCK(ifp);
836 }
837 /*
838 * If the packet was transiting through us, use the address of
839 * the interface that is the closest to the packet source.
840 * When we don't have a route back to the packet source, stop here
841 * and drop the packet.
842 */
843 if (fib4_lookup_nh_ext(M_GETFIB(m), ip->ip_dst, 0, 0, &nh_ext) != 0) {
844 m_freem(m);
845 ICMPSTAT_INC(icps_noroute);
846 goto done;
847 }
848 t = nh_ext.nh_src;
849 match:
850 #ifdef MAC
851 mac_netinet_icmp_replyinplace(m);
852 #endif
853 ip->ip_src = t;
854 ip->ip_ttl = V_ip_defttl;
855
856 if (optlen > 0) {
857 u_char *cp;
858 int opt, cnt;
859 u_int len;
860
861 /*
862 * Retrieve any source routing from the incoming packet;
863 * add on any record-route or timestamp options.
864 */
865 cp = (u_char *) (ip + 1);
866 if ((opts = ip_srcroute(m)) == NULL &&
867 (opts = m_gethdr(M_NOWAIT, MT_DATA))) {
868 opts->m_len = sizeof(struct in_addr);
869 mtod(opts, struct in_addr *)->s_addr = 0;
870 }
871 if (opts) {
872 #ifdef ICMPPRINTFS
873 if (icmpprintfs)
874 printf("icmp_reflect optlen %d rt %d => ",
875 optlen, opts->m_len);
876 #endif
877 for (cnt = optlen; cnt > 0; cnt -= len, cp += len) {
878 opt = cp[IPOPT_OPTVAL];
879 if (opt == IPOPT_EOL)
880 break;
881 if (opt == IPOPT_NOP)
882 len = 1;
883 else {
884 if (cnt < IPOPT_OLEN + sizeof(*cp))
885 break;
886 len = cp[IPOPT_OLEN];
887 if (len < IPOPT_OLEN + sizeof(*cp) ||
888 len > cnt)
889 break;
890 }
891 /*
892 * Should check for overflow, but it "can't happen"
893 */
894 if (opt == IPOPT_RR || opt == IPOPT_TS ||
895 opt == IPOPT_SECURITY) {
896 bcopy((caddr_t)cp,
897 mtod(opts, caddr_t) + opts->m_len, len);
898 opts->m_len += len;
899 }
900 }
901 /* Terminate & pad, if necessary */
902 cnt = opts->m_len % 4;
903 if (cnt) {
904 for (; cnt < 4; cnt++) {
905 *(mtod(opts, caddr_t) + opts->m_len) =
906 IPOPT_EOL;
907 opts->m_len++;
908 }
909 }
910 #ifdef ICMPPRINTFS
911 if (icmpprintfs)
912 printf("%d\n", opts->m_len);
913 #endif
914 }
915 ip_stripoptions(m);
916 }
917 m_tag_delete_nonpersistent(m);
918 m->m_flags &= ~(M_BCAST|M_MCAST);
919 icmp_send(m, opts);
920 done:
921 if (opts)
922 (void)m_free(opts);
923 }
924
925 /*
926 * Send an icmp packet back to the ip level,
927 * after supplying a checksum.
928 */
929 static void
icmp_send(struct mbuf * m,struct mbuf * opts)930 icmp_send(struct mbuf *m, struct mbuf *opts)
931 {
932 struct ip *ip = mtod(m, struct ip *);
933 int hlen;
934 struct icmp *icp;
935
936 hlen = ip->ip_hl << 2;
937 m->m_data += hlen;
938 m->m_len -= hlen;
939 icp = mtod(m, struct icmp *);
940 icp->icmp_cksum = 0;
941 icp->icmp_cksum = in_cksum(m, ntohs(ip->ip_len) - hlen);
942 m->m_data -= hlen;
943 m->m_len += hlen;
944 m->m_pkthdr.rcvif = (struct ifnet *)0;
945 #ifdef ICMPPRINTFS
946 if (icmpprintfs) {
947 char dstbuf[INET_ADDRSTRLEN];
948 char srcbuf[INET_ADDRSTRLEN];
949
950 printf("icmp_send dst %s src %s\n",
951 inet_ntoa_r(ip->ip_dst, dstbuf),
952 inet_ntoa_r(ip->ip_src, srcbuf));
953 }
954 #endif
955 (void) ip_output(m, opts, NULL, 0, NULL, NULL);
956 }
957
958 /*
959 * Return milliseconds since 00:00 UTC in network format.
960 */
961 uint32_t
iptime(void)962 iptime(void)
963 {
964 struct timeval atv;
965 u_long t;
966
967 getmicrotime(&atv);
968 t = (atv.tv_sec % (24*60*60)) * 1000 + atv.tv_usec / 1000;
969 return (htonl(t));
970 }
971
972 /*
973 * Return the next larger or smaller MTU plateau (table from RFC 1191)
974 * given current value MTU. If DIR is less than zero, a larger plateau
975 * is returned; otherwise, a smaller value is returned.
976 */
977 int
ip_next_mtu(int mtu,int dir)978 ip_next_mtu(int mtu, int dir)
979 {
980 static int mtutab[] = {
981 65535, 32000, 17914, 8166, 4352, 2002, 1492, 1280, 1006, 508,
982 296, 68, 0
983 };
984 int i, size;
985
986 size = (sizeof mtutab) / (sizeof mtutab[0]);
987 if (dir >= 0) {
988 for (i = 0; i < size; i++)
989 if (mtu > mtutab[i])
990 return mtutab[i];
991 } else {
992 for (i = size - 1; i >= 0; i--)
993 if (mtu < mtutab[i])
994 return mtutab[i];
995 if (mtu == mtutab[0])
996 return mtutab[0];
997 }
998 return 0;
999 }
1000 #endif /* INET */
1001
1002
1003 /*
1004 * badport_bandlim() - check for ICMP bandwidth limit
1005 *
1006 * Return 0 if it is ok to send an ICMP error response, -1 if we have
1007 * hit our bandwidth limit and it is not ok.
1008 *
1009 * If icmplim is <= 0, the feature is disabled and 0 is returned.
1010 *
1011 * For now we separate the TCP and UDP subsystems w/ different 'which'
1012 * values. We may eventually remove this separation (and simplify the
1013 * code further).
1014 *
1015 * Note that the printing of the error message is delayed so we can
1016 * properly print the icmp error rate that the system was trying to do
1017 * (i.e. 22000/100 pps, etc...). This can cause long delays in printing
1018 * the 'final' error, but it doesn't make sense to solve the printing
1019 * delay with more complex code.
1020 */
1021 struct icmp_rate {
1022 const char *descr;
1023 struct counter_rate cr;
1024 };
1025 VNET_DEFINE_STATIC(struct icmp_rate, icmp_rates[BANDLIM_MAX]) = {
1026 { "icmp unreach response" },
1027 { "icmp ping response" },
1028 { "icmp tstamp response" },
1029 { "closed port RST response" },
1030 { "open port RST response" },
1031 { "icmp6 unreach response" },
1032 { "sctp ootb response" }
1033 };
1034 #define V_icmp_rates VNET(icmp_rates)
1035
1036 static void
icmp_bandlimit_init(void)1037 icmp_bandlimit_init(void)
1038 {
1039
1040 for (int i = 0; i < BANDLIM_MAX; i++) {
1041 V_icmp_rates[i].cr.cr_rate = counter_u64_alloc(M_WAITOK);
1042 V_icmp_rates[i].cr.cr_ticks = ticks;
1043 }
1044 }
1045 VNET_SYSINIT(icmp_bandlimit, SI_SUB_PROTO_DOMAIN, SI_ORDER_ANY,
1046 icmp_bandlimit_init, NULL);
1047
1048 static void
icmp_bandlimit_uninit(void)1049 icmp_bandlimit_uninit(void)
1050 {
1051
1052 for (int i = 0; i < BANDLIM_MAX; i++)
1053 counter_u64_free(V_icmp_rates[i].cr.cr_rate);
1054 }
1055 VNET_SYSUNINIT(icmp_bandlimit, SI_SUB_PROTO_DOMAIN, SI_ORDER_THIRD,
1056 icmp_bandlimit_uninit, NULL);
1057
1058 int
badport_bandlim(int which)1059 badport_bandlim(int which)
1060 {
1061 int64_t pps;
1062
1063 if (V_icmplim == 0 || which == BANDLIM_UNLIMITED)
1064 return (0);
1065
1066 KASSERT(which >= 0 && which < BANDLIM_MAX,
1067 ("%s: which %d", __func__, which));
1068
1069 if ((V_icmplim + V_icmplim_curr_jitter) <= 0)
1070 V_icmplim_curr_jitter = -V_icmplim + 1;
1071
1072 pps = counter_ratecheck(&V_icmp_rates[which].cr, V_icmplim +
1073 V_icmplim_curr_jitter);
1074 if (pps > 0) {
1075 /*
1076 * Adjust limit +/- to jitter the measurement to deny a
1077 * side-channel port scan as in CVE-2020-25705
1078 */
1079 if (V_icmplim_jitter > 0) {
1080 int32_t inc =
1081 arc4random_uniform(V_icmplim_jitter * 2 +1)
1082 - V_icmplim_jitter;
1083
1084 V_icmplim_curr_jitter = inc;
1085 }
1086 }
1087 if (pps == -1)
1088 return (-1);
1089 if (pps > 0 && V_icmplim_output)
1090 log(LOG_NOTICE, "Limiting %s from %jd to %d packets/sec\n",
1091 V_icmp_rates[which].descr, (intmax_t )pps, V_icmplim +
1092 V_icmplim_curr_jitter);
1093 return (0);
1094 }
1095