sys/netinet/ip_icmp.c

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