sys/netinet/ip_icmp.c

   1 /*-
   2  * Copyright (c) 1982, 1986, 1988, 1993
   3  *      The Regents of the University of California.  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  * 4. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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  *      @(#)ip_icmp.c   8.2 (Berkeley) 1/4/94
  30  */
  31
  32 #include <sys/cdefs.h>
  33 __FBSDID("$FreeBSD$");
  34
  35 #include "opt_inet.h"
  36
  37 #include <sys/param.h>
  38 #include <sys/systm.h>
  39 #include <sys/mbuf.h>
  40 #include <sys/protosw.h>
  41 #include <sys/socket.h>
  42 #include <sys/time.h>
  43 #include <sys/kernel.h>
  44 #include <sys/lock.h>
  45 #include <sys/rmlock.h>
  46 #include <sys/sysctl.h>
  47 #include <sys/syslog.h>
  48
  49 #include <net/if.h>
  50 #include <net/if_var.h>
  51 #include <net/if_types.h>
  52 #include <net/route.h>
  53 #include <net/vnet.h>
  54
  55 #include <netinet/in.h>
  56 #include <netinet/in_fib.h>
  57 #include <netinet/in_pcb.h>
  58 #include <netinet/in_systm.h>
  59 #include <netinet/in_var.h>
  60 #include <netinet/ip.h>
  61 #include <netinet/ip_icmp.h>
  62 #include <netinet/ip_var.h>
  63 #include <netinet/ip_options.h>
  64 #include <netinet/sctp.h>
  65 #include <netinet/tcp.h>
  66 #include <netinet/tcp_var.h>
  67 #include <netinet/tcpip.h>
  68 #include <netinet/icmp_var.h>
  69
  70 #ifdef INET
  71
  72 #include <machine/in_cksum.h>
  73
  74 #include <security/mac/mac_framework.h>
  75 #endif /* INET */
  76
  77 /*
  78  * ICMP routines: error generation, receive packet processing, and
  79  * routines to turnaround packets back to the originator, and
  80  * host table maintenance routines.
  81  */
  82 static VNET_DEFINE(int, icmplim) = 200;
  83 #define V_icmplim                       VNET(icmplim)
  84 SYSCTL_INT(_net_inet_icmp, ICMPCTL_ICMPLIM, icmplim, CTLFLAG_VNET | CTLFLAG_RW,
  85         &VNET_NAME(icmplim), 0,
  86         "Maximum number of ICMP responses per second");
  87
  88 static VNET_DEFINE(int, icmplim_output) = 1;
  89 #define V_icmplim_output                VNET(icmplim_output)
  90 SYSCTL_INT(_net_inet_icmp, OID_AUTO, icmplim_output, CTLFLAG_VNET | CTLFLAG_RW,
  91         &VNET_NAME(icmplim_output), 0,
  92         "Enable logging of ICMP response rate limiting");
  93
  94 #ifdef INET
  95 VNET_PCPUSTAT_DEFINE(struct icmpstat, icmpstat);
  96 VNET_PCPUSTAT_SYSINIT(icmpstat);
  97 SYSCTL_VNET_PCPUSTAT(_net_inet_icmp, ICMPCTL_STATS, stats, struct icmpstat,
  98     icmpstat, "ICMP statistics (struct icmpstat, netinet/icmp_var.h)");
  99
 100 #ifdef VIMAGE
 101 VNET_PCPUSTAT_SYSUNINIT(icmpstat);
 102 #endif /* VIMAGE */
 103
 104 static VNET_DEFINE(int, icmpmaskrepl) = 0;
 105 #define V_icmpmaskrepl                  VNET(icmpmaskrepl)
 106 SYSCTL_INT(_net_inet_icmp, ICMPCTL_MASKREPL, maskrepl, CTLFLAG_VNET | CTLFLAG_RW,
 107         &VNET_NAME(icmpmaskrepl), 0,
 108         "Reply to ICMP Address Mask Request packets");
 109
 110 static VNET_DEFINE(u_int, icmpmaskfake) = 0;
 111 #define V_icmpmaskfake                  VNET(icmpmaskfake)
 112 SYSCTL_UINT(_net_inet_icmp, OID_AUTO, maskfake, CTLFLAG_VNET | CTLFLAG_RW,
 113         &VNET_NAME(icmpmaskfake), 0,
 114         "Fake reply to ICMP Address Mask Request packets");
 115
 116 VNET_DEFINE(int, drop_redirect) = 0;
 117 #define V_drop_redirect                 VNET(drop_redirect)
 118 SYSCTL_INT(_net_inet_icmp, OID_AUTO, drop_redirect, CTLFLAG_VNET | CTLFLAG_RW,
 119         &VNET_NAME(drop_redirect), 0,
 120         "Ignore ICMP redirects");
 121
 122 static VNET_DEFINE(int, log_redirect) = 0;
 123 #define V_log_redirect                  VNET(log_redirect)
 124 SYSCTL_INT(_net_inet_icmp, OID_AUTO, log_redirect, CTLFLAG_VNET | CTLFLAG_RW,
 125         &VNET_NAME(log_redirect), 0,
 126         "Log ICMP redirects to the console");
 127
 128 static VNET_DEFINE(char, reply_src[IFNAMSIZ]);
 129 #define V_reply_src                     VNET(reply_src)
 130 SYSCTL_STRING(_net_inet_icmp, OID_AUTO, reply_src, CTLFLAG_VNET | CTLFLAG_RW,
 131         &VNET_NAME(reply_src), IFNAMSIZ,
 132         "ICMP reply source for non-local packets");
 133
 134 static VNET_DEFINE(int, icmp_rfi) = 0;
 135 #define V_icmp_rfi                      VNET(icmp_rfi)
 136 SYSCTL_INT(_net_inet_icmp, OID_AUTO, reply_from_interface, CTLFLAG_VNET | CTLFLAG_RW,
 137         &VNET_NAME(icmp_rfi), 0,
 138         "ICMP reply from incoming interface for non-local packets");
 139
 140 static VNET_DEFINE(int, icmp_quotelen) = 8;
 141 #define V_icmp_quotelen                 VNET(icmp_quotelen)
 142 SYSCTL_INT(_net_inet_icmp, OID_AUTO, quotelen, CTLFLAG_VNET | CTLFLAG_RW,
 143         &VNET_NAME(icmp_quotelen), 0,
 144         "Number of bytes from original packet to quote in ICMP reply");
 145
 146 static VNET_DEFINE(int, icmpbmcastecho) = 0;
 147 #define V_icmpbmcastecho                VNET(icmpbmcastecho)
 148 SYSCTL_INT(_net_inet_icmp, OID_AUTO, bmcastecho, CTLFLAG_VNET | CTLFLAG_RW,
 149         &VNET_NAME(icmpbmcastecho), 0,
 150         "Reply to multicast ICMP Echo Request and Timestamp packets");
 151
 152 static VNET_DEFINE(int, icmptstamprepl) = 1;
 153 #define V_icmptstamprepl                VNET(icmptstamprepl)
 154 SYSCTL_INT(_net_inet_icmp, OID_AUTO, tstamprepl, CTLFLAG_RW,
 155         &VNET_NAME(icmptstamprepl), 0,
 156         "Respond to ICMP Timestamp packets");
 157
 158 #ifdef ICMPPRINTFS
 159 int     icmpprintfs = 0;
 160 #endif
 161
 162 static void     icmp_reflect(struct mbuf *);
 163 static void     icmp_send(struct mbuf *, struct mbuf *);
 164
 165 extern  struct protosw inetsw[];
 166
 167 /*
 168  * Kernel module interface for updating icmpstat.  The argument is an index
 169  * into icmpstat treated as an array of u_long.  While this encodes the
 170  * general layout of icmpstat into the caller, it doesn't encode its
 171  * location, so that future changes to add, for example, per-CPU stats
 172  * support won't cause binary compatibility problems for kernel modules.
 173  */
 174 void
 175 kmod_icmpstat_inc(int statnum)
 176 {
 177
 178         counter_u64_add(VNET(icmpstat)[statnum], 1);
 179 }
 180
 181 /*
 182  * Generate an error packet of type error
 183  * in response to bad packet ip.
 184  */
 185 void
 186 icmp_error(struct mbuf *n, int type, int code, uint32_t dest, int mtu)
 187 {
 188         struct ip *oip, *nip;
 189         struct icmp *icp;
 190         struct mbuf *m;
 191         unsigned icmplen, icmpelen, nlen, oiphlen;
 192
 193         KASSERT((u_int)type <= ICMP_MAXTYPE, ("%s: illegal ICMP type",
 194             __func__));
 195
 196         if (type != ICMP_REDIRECT)
 197                 ICMPSTAT_INC(icps_error);
 198         /*
 199          * Don't send error:
 200          *  if the original packet was encrypted.
 201          *  if not the first fragment of message.
 202          *  in response to a multicast or broadcast packet.
 203          *  if the old packet protocol was an ICMP error message.
 204          */
 205         if (n->m_flags & M_DECRYPTED)
 206                 goto freeit;
 207         if (n->m_flags & (M_BCAST|M_MCAST))
 208                 goto freeit;
 209
 210         /* Drop if IP header plus 8 bytes is not contiguous in first mbuf. */
 211         if (n->m_len < sizeof(struct ip) + ICMP_MINLEN)
 212                 goto freeit;
 213         oip = mtod(n, struct ip *);
 214         oiphlen = oip->ip_hl << 2;
 215         if (n->m_len < oiphlen + ICMP_MINLEN)
 216                 goto freeit;
 217 #ifdef ICMPPRINTFS
 218         if (icmpprintfs)
 219                 printf("icmp_error(%p, %x, %d)\n", oip, type, code);
 220 #endif
 221         if (oip->ip_off & htons(~(IP_MF|IP_DF)))
 222                 goto freeit;
 223         if (oip->ip_p == IPPROTO_ICMP && type != ICMP_REDIRECT &&
 224             !ICMP_INFOTYPE(((struct icmp *)((caddr_t)oip +
 225                 oiphlen))->icmp_type)) {
 226                 ICMPSTAT_INC(icps_oldicmp);
 227                 goto freeit;
 228         }
 229         /*
 230          * Calculate length to quote from original packet and
 231          * prevent the ICMP mbuf from overflowing.
 232          * Unfortunately this is non-trivial since ip_forward()
 233          * sends us truncated packets.
 234          */
 235         nlen = m_length(n, NULL);
 236         if (oip->ip_p == IPPROTO_TCP) {
 237                 struct tcphdr *th;
 238                 int tcphlen;
 239
 240                 if (oiphlen + sizeof(struct tcphdr) > n->m_len &&
 241                     n->m_next == NULL)
 242                         goto stdreply;
 243                 if (n->m_len < oiphlen + sizeof(struct tcphdr) &&
 244                     (n = m_pullup(n, oiphlen + sizeof(struct tcphdr))) == NULL)
 245                         goto freeit;
 246                 oip = mtod(n, struct ip *);
 247                 th = mtodo(n, oiphlen);
 248                 tcphlen = th->th_off << 2;
 249                 if (tcphlen < sizeof(struct tcphdr))
 250                         goto freeit;
 251                 if (ntohs(oip->ip_len) < oiphlen + tcphlen)
 252                         goto freeit;
 253                 if (oiphlen + tcphlen > n->m_len && n->m_next == NULL)
 254                         goto stdreply;
 255                 if (n->m_len < oiphlen + tcphlen &&
 256                     (n = m_pullup(n, oiphlen + tcphlen)) == NULL)
 257                         goto freeit;
 258                 icmpelen = max(tcphlen, min(V_icmp_quotelen,
 259                     ntohs(oip->ip_len) - oiphlen));
 260         } else if (oip->ip_p == IPPROTO_SCTP) {
 261                 struct sctphdr *sh;
 262                 struct sctp_chunkhdr *ch;
 263
 264                 if (ntohs(oip->ip_len) < oiphlen + sizeof(struct sctphdr))
 265                         goto stdreply;
 266                 if (oiphlen + sizeof(struct sctphdr) > n->m_len &&
 267                     n->m_next == NULL)
 268                         goto stdreply;
 269                 if (n->m_len < oiphlen + sizeof(struct sctphdr) &&
 270                     (n = m_pullup(n, oiphlen + sizeof(struct sctphdr))) == NULL)
 271                         goto freeit;
 272                 oip = mtod(n, struct ip *);
 273                 icmpelen = max(sizeof(struct sctphdr),
 274                     min(V_icmp_quotelen, ntohs(oip->ip_len) - oiphlen));
 275                 sh = mtodo(n, oiphlen);
 276                 if (ntohl(sh->v_tag) == 0 &&
 277                     ntohs(oip->ip_len) >= oiphlen +
 278                     sizeof(struct sctphdr) + 8 &&
 279                     (n->m_len >= oiphlen + sizeof(struct sctphdr) + 8 ||
 280                      n->m_next != NULL)) {
 281                         if (n->m_len < oiphlen + sizeof(struct sctphdr) + 8 &&
 282                             (n = m_pullup(n, oiphlen +
 283                             sizeof(struct sctphdr) + 8)) == NULL)
 284                                 goto freeit;
 285                         oip = mtod(n, struct ip *);
 286                         sh = mtodo(n, oiphlen);
 287                         ch = (struct sctp_chunkhdr *)(sh + 1);
 288                         if (ch->chunk_type == SCTP_INITIATION) {
 289                                 icmpelen = max(sizeof(struct sctphdr) + 8,
 290                                     min(V_icmp_quotelen, ntohs(oip->ip_len) -
 291                                     oiphlen));
 292                         }
 293                 }
 294         } else
 295 stdreply:       icmpelen = max(8, min(V_icmp_quotelen, ntohs(oip->ip_len) -
 296                     oiphlen));
 297
 298         icmplen = min(oiphlen + icmpelen, nlen);
 299         if (icmplen < sizeof(struct ip))
 300                 goto freeit;
 301
 302         if (MHLEN > sizeof(struct ip) + ICMP_MINLEN + icmplen)
 303                 m = m_gethdr(M_NOWAIT, MT_DATA);
 304         else
 305                 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR);
 306         if (m == NULL)
 307                 goto freeit;
 308 #ifdef MAC
 309         mac_netinet_icmp_reply(n, m);
 310 #endif
 311         icmplen = min(icmplen, M_TRAILINGSPACE(m) -
 312             sizeof(struct ip) - ICMP_MINLEN);
 313         m_align(m, ICMP_MINLEN + icmplen);
 314         m->m_len = ICMP_MINLEN + icmplen;
 315
 316         /* XXX MRT  make the outgoing packet use the same FIB
 317          * that was associated with the incoming packet
 318          */
 319         M_SETFIB(m, M_GETFIB(n));
 320         icp = mtod(m, struct icmp *);
 321         ICMPSTAT_INC(icps_outhist[type]);
 322         icp->icmp_type = type;
 323         if (type == ICMP_REDIRECT)
 324                 icp->icmp_gwaddr.s_addr = dest;
 325         else {
 326                 icp->icmp_void = 0;
 327                 /*
 328                  * The following assignments assume an overlay with the
 329                  * just zeroed icmp_void field.
 330                  */
 331                 if (type == ICMP_PARAMPROB) {
 332                         icp->icmp_pptr = code;
 333                         code = 0;
 334                 } else if (type == ICMP_UNREACH &&
 335                         code == ICMP_UNREACH_NEEDFRAG && mtu) {
 336                         icp->icmp_nextmtu = htons(mtu);
 337                 }
 338         }
 339         icp->icmp_code = code;
 340
 341         /*
 342          * Copy the quotation into ICMP message and
 343          * convert quoted IP header back to network representation.
 344          */
 345         m_copydata(n, 0, icmplen, (caddr_t)&icp->icmp_ip);
 346         nip = &icp->icmp_ip;
 347
 348         /*
 349          * Set up ICMP message mbuf and copy old IP header (without options
 350          * in front of ICMP message.
 351          * If the original mbuf was meant to bypass the firewall, the error
 352          * reply should bypass as well.
 353          */
 354         m->m_flags |= n->m_flags & M_SKIP_FIREWALL;
 355         m->m_data -= sizeof(struct ip);
 356         m->m_len += sizeof(struct ip);
 357         m->m_pkthdr.len = m->m_len;
 358         m->m_pkthdr.rcvif = n->m_pkthdr.rcvif;
 359         nip = mtod(m, struct ip *);
 360         bcopy((caddr_t)oip, (caddr_t)nip, sizeof(struct ip));
 361         nip->ip_len = htons(m->m_len);
 362         nip->ip_v = IPVERSION;
 363         nip->ip_hl = 5;
 364         nip->ip_p = IPPROTO_ICMP;
 365         nip->ip_tos = 0;
 366         nip->ip_off = 0;
 367         icmp_reflect(m);
 368
 369 freeit:
 370         m_freem(n);
 371 }
 372
 373 /*
 374  * Process a received ICMP message.
 375  */
 376 int
 377 icmp_input(struct mbuf **mp, int *offp, int proto)
 378 {
 379         struct icmp *icp;
 380         struct in_ifaddr *ia;
 381         struct mbuf *m = *mp;
 382         struct ip *ip = mtod(m, struct ip *);
 383         struct sockaddr_in icmpsrc, icmpdst, icmpgw;
 384         int hlen = *offp;
 385         int icmplen = ntohs(ip->ip_len) - *offp;
 386         int i, code;
 387         void (*ctlfunc)(int, struct sockaddr *, void *);
 388         int fibnum;
 389
 390         *mp = NULL;
 391
 392         /*
 393          * Locate icmp structure in mbuf, and check
 394          * that not corrupted and of at least minimum length.
 395          */
 396 #ifdef ICMPPRINTFS
 397         if (icmpprintfs) {
 398                 char srcbuf[INET_ADDRSTRLEN];
 399                 char dstbuf[INET_ADDRSTRLEN];
 400
 401                 printf("icmp_input from %s to %s, len %d\n",
 402                     inet_ntoa_r(ip->ip_src, srcbuf),
 403                     inet_ntoa_r(ip->ip_dst, dstbuf), icmplen);
 404         }
 405 #endif
 406         if (icmplen < ICMP_MINLEN) {
 407                 ICMPSTAT_INC(icps_tooshort);
 408                 goto freeit;
 409         }
 410         i = hlen + min(icmplen, ICMP_ADVLENMIN);
 411         if (m->m_len < i && (m = m_pullup(m, i)) == NULL)  {
 412                 ICMPSTAT_INC(icps_tooshort);
 413                 return (IPPROTO_DONE);
 414         }
 415         ip = mtod(m, struct ip *);
 416         m->m_len -= hlen;
 417         m->m_data += hlen;
 418         icp = mtod(m, struct icmp *);
 419         if (in_cksum(m, icmplen)) {
 420                 ICMPSTAT_INC(icps_checksum);
 421                 goto freeit;
 422         }
 423         m->m_len += hlen;
 424         m->m_data -= hlen;
 425
 426 #ifdef ICMPPRINTFS
 427         if (icmpprintfs)
 428                 printf("icmp_input, type %d code %d\n", icp->icmp_type,
 429                     icp->icmp_code);
 430 #endif
 431
 432         /*
 433          * Message type specific processing.
 434          */
 435         if (icp->icmp_type > ICMP_MAXTYPE)
 436                 goto raw;
 437
 438         /* Initialize */
 439         bzero(&icmpsrc, sizeof(icmpsrc));
 440         icmpsrc.sin_len = sizeof(struct sockaddr_in);
 441         icmpsrc.sin_family = AF_INET;
 442         bzero(&icmpdst, sizeof(icmpdst));
 443         icmpdst.sin_len = sizeof(struct sockaddr_in);
 444         icmpdst.sin_family = AF_INET;
 445         bzero(&icmpgw, sizeof(icmpgw));
 446         icmpgw.sin_len = sizeof(struct sockaddr_in);
 447         icmpgw.sin_family = AF_INET;
 448
 449         ICMPSTAT_INC(icps_inhist[icp->icmp_type]);
 450         code = icp->icmp_code;
 451         switch (icp->icmp_type) {
 452
 453         case ICMP_UNREACH:
 454                 switch (code) {
 455                         case ICMP_UNREACH_NET:
 456                         case ICMP_UNREACH_HOST:
 457                         case ICMP_UNREACH_SRCFAIL:
 458                         case ICMP_UNREACH_NET_UNKNOWN:
 459                         case ICMP_UNREACH_HOST_UNKNOWN:
 460                         case ICMP_UNREACH_ISOLATED:
 461                         case ICMP_UNREACH_TOSNET:
 462                         case ICMP_UNREACH_TOSHOST:
 463                         case ICMP_UNREACH_HOST_PRECEDENCE:
 464                         case ICMP_UNREACH_PRECEDENCE_CUTOFF:
 465                                 code = PRC_UNREACH_NET;
 466                                 break;
 467
 468                         case ICMP_UNREACH_NEEDFRAG:
 469                                 code = PRC_MSGSIZE;
 470                                 break;
 471
 472                         /*
 473                          * RFC 1122, Sections 3.2.2.1 and 4.2.3.9.
 474                          * Treat subcodes 2,3 as immediate RST
 475                          */
 476                         case ICMP_UNREACH_PROTOCOL:
 477                                 code = PRC_UNREACH_PROTOCOL;
 478                                 break;
 479                         case ICMP_UNREACH_PORT:
 480                                 code = PRC_UNREACH_PORT;
 481                                 break;
 482
 483                         case ICMP_UNREACH_NET_PROHIB:
 484                         case ICMP_UNREACH_HOST_PROHIB:
 485                         case ICMP_UNREACH_FILTER_PROHIB:
 486                                 code = PRC_UNREACH_ADMIN_PROHIB;
 487                                 break;
 488
 489                         default:
 490                                 goto badcode;
 491                 }
 492                 goto deliver;
 493
 494         case ICMP_TIMXCEED:
 495                 if (code > 1)
 496                         goto badcode;
 497                 code += PRC_TIMXCEED_INTRANS;
 498                 goto deliver;
 499
 500         case ICMP_PARAMPROB:
 501                 if (code > 1)
 502                         goto badcode;
 503                 code = PRC_PARAMPROB;
 504         deliver:
 505                 /*
 506                  * Problem with datagram; advise higher level routines.
 507                  */
 508                 if (icmplen < ICMP_ADVLENMIN || icmplen < ICMP_ADVLEN(icp) ||
 509                     icp->icmp_ip.ip_hl < (sizeof(struct ip) >> 2)) {
 510                         ICMPSTAT_INC(icps_badlen);
 511                         goto freeit;
 512                 }
 513                 /* Discard ICMP's in response to multicast packets */
 514                 if (IN_MULTICAST(ntohl(icp->icmp_ip.ip_dst.s_addr)))
 515                         goto badcode;
 516 #ifdef ICMPPRINTFS
 517                 if (icmpprintfs)
 518                         printf("deliver to protocol %d\n", icp->icmp_ip.ip_p);
 519 #endif
 520                 icmpsrc.sin_addr = icp->icmp_ip.ip_dst;
 521                 /*
 522                  * XXX if the packet contains [IPv4 AH TCP], we can't make a
 523                  * notification to TCP layer.
 524                  */
 525                 i = sizeof(struct ip) + min(icmplen, ICMP_ADVLENPREF(icp));
 526                 ip_stripoptions(m);
 527                 if (m->m_len < i && (m = m_pullup(m, i)) == NULL) {
 528                         /* This should actually not happen */
 529                         ICMPSTAT_INC(icps_tooshort);
 530                         return (IPPROTO_DONE);
 531                 }
 532                 ip = mtod(m, struct ip *);
 533                 icp = (struct icmp *)(ip + 1);
 534                 /*
 535                  * The upper layer handler can rely on:
 536                  * - The outer IP header has no options.
 537                  * - The outer IP header, the ICMP header, the inner IP header,
 538                  *   and the first n bytes of the inner payload are contiguous.
 539                  *   n is at least 8, but might be larger based on
 540                  *   ICMP_ADVLENPREF. See its definition in ip_icmp.h.
 541                  */
 542                 ctlfunc = inetsw[ip_protox[icp->icmp_ip.ip_p]].pr_ctlinput;
 543                 if (ctlfunc)
 544                         (*ctlfunc)(code, (struct sockaddr *)&icmpsrc,
 545                                    (void *)&icp->icmp_ip);
 546                 break;
 547
 548         badcode:
 549                 ICMPSTAT_INC(icps_badcode);
 550                 break;
 551
 552         case ICMP_ECHO:
 553                 if (!V_icmpbmcastecho
 554                     && (m->m_flags & (M_MCAST | M_BCAST)) != 0) {
 555                         ICMPSTAT_INC(icps_bmcastecho);
 556                         break;
 557                 }
 558                 icp->icmp_type = ICMP_ECHOREPLY;
 559                 if (badport_bandlim(BANDLIM_ICMP_ECHO) < 0)
 560                         goto freeit;
 561                 else
 562                         goto reflect;
 563
 564         case ICMP_TSTAMP:
 565                 if (V_icmptstamprepl == 0)
 566                         break;
 567                 if (!V_icmpbmcastecho
 568                     && (m->m_flags & (M_MCAST | M_BCAST)) != 0) {
 569                         ICMPSTAT_INC(icps_bmcasttstamp);
 570                         break;
 571                 }
 572                 if (icmplen < ICMP_TSLEN) {
 573                         ICMPSTAT_INC(icps_badlen);
 574                         break;
 575                 }
 576                 icp->icmp_type = ICMP_TSTAMPREPLY;
 577                 icp->icmp_rtime = iptime();
 578                 icp->icmp_ttime = icp->icmp_rtime;      /* bogus, do later! */
 579                 if (badport_bandlim(BANDLIM_ICMP_TSTAMP) < 0)
 580                         goto freeit;
 581                 else
 582                         goto reflect;
 583
 584         case ICMP_MASKREQ:
 585                 if (V_icmpmaskrepl == 0)
 586                         break;
 587                 /*
 588                  * We are not able to respond with all ones broadcast
 589                  * unless we receive it over a point-to-point interface.
 590                  */
 591                 if (icmplen < ICMP_MASKLEN)
 592                         break;
 593                 switch (ip->ip_dst.s_addr) {
 594
 595                 case INADDR_BROADCAST:
 596                 case INADDR_ANY:
 597                         icmpdst.sin_addr = ip->ip_src;
 598                         break;
 599
 600                 default:
 601                         icmpdst.sin_addr = ip->ip_dst;
 602                 }
 603                 ia = (struct in_ifaddr *)ifaof_ifpforaddr(
 604                             (struct sockaddr *)&icmpdst, m->m_pkthdr.rcvif);
 605                 if (ia == NULL)
 606                         break;
 607                 if (ia->ia_ifp == NULL) {
 608                         ifa_free(&ia->ia_ifa);
 609                         break;
 610                 }
 611                 icp->icmp_type = ICMP_MASKREPLY;
 612                 if (V_icmpmaskfake == 0)
 613                         icp->icmp_mask = ia->ia_sockmask.sin_addr.s_addr;
 614                 else
 615                         icp->icmp_mask = V_icmpmaskfake;
 616                 if (ip->ip_src.s_addr == 0) {
 617                         if (ia->ia_ifp->if_flags & IFF_BROADCAST)
 618                             ip->ip_src = satosin(&ia->ia_broadaddr)->sin_addr;
 619                         else if (ia->ia_ifp->if_flags & IFF_POINTOPOINT)
 620                             ip->ip_src = satosin(&ia->ia_dstaddr)->sin_addr;
 621                 }
 622                 ifa_free(&ia->ia_ifa);
 623 reflect:
 624                 ICMPSTAT_INC(icps_reflect);
 625                 ICMPSTAT_INC(icps_outhist[icp->icmp_type]);
 626                 icmp_reflect(m);
 627                 return (IPPROTO_DONE);
 628
 629         case ICMP_REDIRECT:
 630                 if (V_log_redirect) {
 631                         u_long src, dst, gw;
 632
 633                         src = ntohl(ip->ip_src.s_addr);
 634                         dst = ntohl(icp->icmp_ip.ip_dst.s_addr);
 635                         gw = ntohl(icp->icmp_gwaddr.s_addr);
 636                         printf("icmp redirect from %d.%d.%d.%d: "
 637                                "%d.%d.%d.%d => %d.%d.%d.%d\n",
 638                                (int)(src >> 24), (int)((src >> 16) & 0xff),
 639                                (int)((src >> 8) & 0xff), (int)(src & 0xff),
 640                                (int)(dst >> 24), (int)((dst >> 16) & 0xff),
 641                                (int)((dst >> 8) & 0xff), (int)(dst & 0xff),
 642                                (int)(gw >> 24), (int)((gw >> 16) & 0xff),
 643                                (int)((gw >> 8) & 0xff), (int)(gw & 0xff));
 644                 }
 645                 /*
 646                  * RFC1812 says we must ignore ICMP redirects if we
 647                  * are acting as router.
 648                  */
 649                 if (V_drop_redirect || V_ipforwarding)
 650                         break;
 651                 if (code > 3)
 652                         goto badcode;
 653                 if (icmplen < ICMP_ADVLENMIN || icmplen < ICMP_ADVLEN(icp) ||
 654                     icp->icmp_ip.ip_hl < (sizeof(struct ip) >> 2)) {
 655                         ICMPSTAT_INC(icps_badlen);
 656                         break;
 657                 }
 658                 /*
 659                  * Short circuit routing redirects to force
 660                  * immediate change in the kernel's routing
 661                  * tables.  The message is also handed to anyone
 662                  * listening on a raw socket (e.g. the routing
 663                  * daemon for use in updating its tables).
 664                  */
 665                 icmpgw.sin_addr = ip->ip_src;
 666                 icmpdst.sin_addr = icp->icmp_gwaddr;
 667 #ifdef  ICMPPRINTFS
 668                 if (icmpprintfs) {
 669                         char dstbuf[INET_ADDRSTRLEN];
 670                         char gwbuf[INET_ADDRSTRLEN];
 671
 672                         printf("redirect dst %s to %s\n",
 673                                inet_ntoa_r(icp->icmp_ip.ip_dst, dstbuf),
 674                                inet_ntoa_r(icp->icmp_gwaddr, gwbuf));
 675                 }
 676 #endif
 677                 icmpsrc.sin_addr = icp->icmp_ip.ip_dst;
 678                 for ( fibnum = 0; fibnum < rt_numfibs; fibnum++) {
 679                         in_rtredirect((struct sockaddr *)&icmpsrc,
 680                           (struct sockaddr *)&icmpdst,
 681                           (struct sockaddr *)0, RTF_GATEWAY | RTF_HOST,
 682                           (struct sockaddr *)&icmpgw, fibnum);
 683                 }
 684                 pfctlinput(PRC_REDIRECT_HOST, (struct sockaddr *)&icmpsrc);
 685                 break;
 686
 687         /*
 688          * No kernel processing for the following;
 689          * just fall through to send to raw listener.
 690          */
 691         case ICMP_ECHOREPLY:
 692         case ICMP_ROUTERADVERT:
 693         case ICMP_ROUTERSOLICIT:
 694         case ICMP_TSTAMPREPLY:
 695         case ICMP_IREQREPLY:
 696         case ICMP_MASKREPLY:
 697         case ICMP_SOURCEQUENCH:
 698         default:
 699                 break;
 700         }
 701
 702 raw:
 703         *mp = m;
 704         rip_input(mp, offp, proto);
 705         return (IPPROTO_DONE);
 706
 707 freeit:
 708         m_freem(m);
 709         return (IPPROTO_DONE);
 710 }
 711
 712 /*
 713  * Reflect the ip packet back to the source
 714  */
 715 static void
 716 icmp_reflect(struct mbuf *m)
 717 {
 718         struct rm_priotracker in_ifa_tracker;
 719         struct ip *ip = mtod(m, struct ip *);
 720         struct ifaddr *ifa;
 721         struct ifnet *ifp;
 722         struct in_ifaddr *ia;
 723         struct in_addr t;
 724         struct nhop4_extended nh_ext;
 725         struct mbuf *opts = NULL;
 726         int optlen = (ip->ip_hl << 2) - sizeof(struct ip);
 727
 728         if (IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
 729             IN_EXPERIMENTAL(ntohl(ip->ip_src.s_addr)) ||
 730             IN_ZERONET(ntohl(ip->ip_src.s_addr)) ) {
 731                 m_freem(m);     /* Bad return address */
 732                 ICMPSTAT_INC(icps_badaddr);
 733                 goto done;      /* Ip_output() will check for broadcast */
 734         }
 735
 736         t = ip->ip_dst;
 737         ip->ip_dst = ip->ip_src;
 738
 739         /*
 740          * Source selection for ICMP replies:
 741          *
 742          * If the incoming packet was addressed directly to one of our
 743          * own addresses, use dst as the src for the reply.
 744          */
 745         IN_IFADDR_RLOCK(&in_ifa_tracker);
 746         LIST_FOREACH(ia, INADDR_HASH(t.s_addr), ia_hash) {
 747                 if (t.s_addr == IA_SIN(ia)->sin_addr.s_addr) {
 748                         t = IA_SIN(ia)->sin_addr;
 749                         IN_IFADDR_RUNLOCK(&in_ifa_tracker);
 750                         goto match;
 751                 }
 752         }
 753         IN_IFADDR_RUNLOCK(&in_ifa_tracker);
 754
 755         /*
 756          * If the incoming packet was addressed to one of our broadcast
 757          * addresses, use the first non-broadcast address which corresponds
 758          * to the incoming interface.
 759          */
 760         ifp = m->m_pkthdr.rcvif;
 761         if (ifp != NULL && ifp->if_flags & IFF_BROADCAST) {
 762                 IF_ADDR_RLOCK(ifp);
 763                 TAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
 764                         if (ifa->ifa_addr->sa_family != AF_INET)
 765                                 continue;
 766                         ia = ifatoia(ifa);
 767                         if (satosin(&ia->ia_broadaddr)->sin_addr.s_addr ==
 768                             t.s_addr) {
 769                                 t = IA_SIN(ia)->sin_addr;
 770                                 IF_ADDR_RUNLOCK(ifp);
 771                                 goto match;
 772                         }
 773                 }
 774                 IF_ADDR_RUNLOCK(ifp);
 775         }
 776         /*
 777          * If the packet was transiting through us, use the address of
 778          * the interface the packet came through in.  If that interface
 779          * doesn't have a suitable IP address, the normal selection
 780          * criteria apply.
 781          */
 782         if (V_icmp_rfi && ifp != NULL) {
 783                 IF_ADDR_RLOCK(ifp);
 784                 TAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
 785                         if (ifa->ifa_addr->sa_family != AF_INET)
 786                                 continue;
 787                         ia = ifatoia(ifa);
 788                         t = IA_SIN(ia)->sin_addr;
 789                         IF_ADDR_RUNLOCK(ifp);
 790                         goto match;
 791                 }
 792                 IF_ADDR_RUNLOCK(ifp);
 793         }
 794         /*
 795          * If the incoming packet was not addressed directly to us, use
 796          * designated interface for icmp replies specified by sysctl
 797          * net.inet.icmp.reply_src (default not set). Otherwise continue
 798          * with normal source selection.
 799          */
 800         if (V_reply_src[0] != '\0' && (ifp = ifunit(V_reply_src))) {
 801                 IF_ADDR_RLOCK(ifp);
 802                 TAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
 803                         if (ifa->ifa_addr->sa_family != AF_INET)
 804                                 continue;
 805                         ia = ifatoia(ifa);
 806                         t = IA_SIN(ia)->sin_addr;
 807                         IF_ADDR_RUNLOCK(ifp);
 808                         goto match;
 809                 }
 810                 IF_ADDR_RUNLOCK(ifp);
 811         }
 812         /*
 813          * If the packet was transiting through us, use the address of
 814          * the interface that is the closest to the packet source.
 815          * When we don't have a route back to the packet source, stop here
 816          * and drop the packet.
 817          */
 818         if (fib4_lookup_nh_ext(M_GETFIB(m), ip->ip_dst, 0, 0, &nh_ext) != 0) {
 819                 m_freem(m);
 820                 ICMPSTAT_INC(icps_noroute);
 821                 goto done;
 822         }
 823         t = nh_ext.nh_src;
 824 match:
 825 #ifdef MAC
 826         mac_netinet_icmp_replyinplace(m);
 827 #endif
 828         ip->ip_src = t;
 829         ip->ip_ttl = V_ip_defttl;
 830
 831         if (optlen > 0) {
 832                 register u_char *cp;
 833                 int opt, cnt;
 834                 u_int len;
 835
 836                 /*
 837                  * Retrieve any source routing from the incoming packet;
 838                  * add on any record-route or timestamp options.
 839                  */
 840                 cp = (u_char *) (ip + 1);
 841                 if ((opts = ip_srcroute(m)) == NULL &&
 842                     (opts = m_gethdr(M_NOWAIT, MT_DATA))) {
 843                         opts->m_len = sizeof(struct in_addr);
 844                         mtod(opts, struct in_addr *)->s_addr = 0;
 845                 }
 846                 if (opts) {
 847 #ifdef ICMPPRINTFS
 848                     if (icmpprintfs)
 849                             printf("icmp_reflect optlen %d rt %d => ",
 850                                 optlen, opts->m_len);
 851 #endif
 852                     for (cnt = optlen; cnt > 0; cnt -= len, cp += len) {
 853                             opt = cp[IPOPT_OPTVAL];
 854                             if (opt == IPOPT_EOL)
 855                                     break;
 856                             if (opt == IPOPT_NOP)
 857                                     len = 1;
 858                             else {
 859                                     if (cnt < IPOPT_OLEN + sizeof(*cp))
 860                                             break;
 861                                     len = cp[IPOPT_OLEN];
 862                                     if (len < IPOPT_OLEN + sizeof(*cp) ||
 863                                         len > cnt)
 864                                             break;
 865                             }
 866                             /*
 867                              * Should check for overflow, but it "can't happen"
 868                              */
 869                             if (opt == IPOPT_RR || opt == IPOPT_TS ||
 870                                 opt == IPOPT_SECURITY) {
 871                                     bcopy((caddr_t)cp,
 872                                         mtod(opts, caddr_t) + opts->m_len, len);
 873                                     opts->m_len += len;
 874                             }
 875                     }
 876                     /* Terminate & pad, if necessary */
 877                     cnt = opts->m_len % 4;
 878                     if (cnt) {
 879                             for (; cnt < 4; cnt++) {
 880                                     *(mtod(opts, caddr_t) + opts->m_len) =
 881                                         IPOPT_EOL;
 882                                     opts->m_len++;
 883                             }
 884                     }
 885 #ifdef ICMPPRINTFS
 886                     if (icmpprintfs)
 887                             printf("%d\n", opts->m_len);
 888 #endif
 889                 }
 890                 ip_stripoptions(m);
 891         }
 892         m_tag_delete_nonpersistent(m);
 893         m->m_flags &= ~(M_BCAST|M_MCAST);
 894         icmp_send(m, opts);
 895 done:
 896         if (opts)
 897                 (void)m_free(opts);
 898 }
 899
 900 /*
 901  * Send an icmp packet back to the ip level,
 902  * after supplying a checksum.
 903  */
 904 static void
 905 icmp_send(struct mbuf *m, struct mbuf *opts)
 906 {
 907         register struct ip *ip = mtod(m, struct ip *);
 908         register int hlen;
 909         register struct icmp *icp;
 910
 911         hlen = ip->ip_hl << 2;
 912         m->m_data += hlen;
 913         m->m_len -= hlen;
 914         icp = mtod(m, struct icmp *);
 915         icp->icmp_cksum = 0;
 916         icp->icmp_cksum = in_cksum(m, ntohs(ip->ip_len) - hlen);
 917         m->m_data -= hlen;
 918         m->m_len += hlen;
 919         m->m_pkthdr.rcvif = (struct ifnet *)0;
 920 #ifdef ICMPPRINTFS
 921         if (icmpprintfs) {
 922                 char dstbuf[INET_ADDRSTRLEN];
 923                 char srcbuf[INET_ADDRSTRLEN];
 924
 925                 printf("icmp_send dst %s src %s\n",
 926                     inet_ntoa_r(ip->ip_dst, dstbuf),
 927                     inet_ntoa_r(ip->ip_src, srcbuf));
 928         }
 929 #endif
 930         (void) ip_output(m, opts, NULL, 0, NULL, NULL);
 931 }
 932
 933 /*
 934  * Return milliseconds since 00:00 UTC in network format.
 935  */
 936 uint32_t
 937 iptime(void)
 938 {
 939         struct timeval atv;
 940         u_long t;
 941
 942         getmicrotime(&atv);
 943         t = (atv.tv_sec % (24*60*60)) * 1000 + atv.tv_usec / 1000;
 944         return (htonl(t));
 945 }
 946
 947 /*
 948  * Return the next larger or smaller MTU plateau (table from RFC 1191)
 949  * given current value MTU.  If DIR is less than zero, a larger plateau
 950  * is returned; otherwise, a smaller value is returned.
 951  */
 952 int
 953 ip_next_mtu(int mtu, int dir)
 954 {
 955         static int mtutab[] = {
 956                 65535, 32000, 17914, 8166, 4352, 2002, 1492, 1280, 1006, 508,
 957                 296, 68, 0
 958         };
 959         int i, size;
 960
 961         size = (sizeof mtutab) / (sizeof mtutab[0]);
 962         if (dir >= 0) {
 963                 for (i = 0; i < size; i++)
 964                         if (mtu > mtutab[i])
 965                                 return mtutab[i];
 966         } else {
 967                 for (i = size - 1; i >= 0; i--)
 968                         if (mtu < mtutab[i])
 969                                 return mtutab[i];
 970                 if (mtu == mtutab[0])
 971                         return mtutab[0];
 972         }
 973         return 0;
 974 }
 975 #endif /* INET */
 976
 977
 978 /*
 979  * badport_bandlim() - check for ICMP bandwidth limit
 980  *
 981  *      Return 0 if it is ok to send an ICMP error response, -1 if we have
 982  *      hit our bandwidth limit and it is not ok.
 983  *
 984  *      If icmplim is <= 0, the feature is disabled and 0 is returned.
 985  *
 986  *      For now we separate the TCP and UDP subsystems w/ different 'which'
 987  *      values.  We may eventually remove this separation (and simplify the
 988  *      code further).
 989  *
 990  *      Note that the printing of the error message is delayed so we can
 991  *      properly print the icmp error rate that the system was trying to do
 992  *      (i.e. 22000/100 pps, etc...).  This can cause long delays in printing
 993  *      the 'final' error, but it doesn't make sense to solve the printing
 994  *      delay with more complex code.
 995  */
 996
 997 int
 998 badport_bandlim(int which)
 999 {
1000
1001 #define N(a)    (sizeof (a) / sizeof (a[0]))
1002         static struct rate {
1003                 const char      *type;
1004                 struct timeval  lasttime;
1005                 int             curpps;
1006         } rates[BANDLIM_MAX+1] = {
1007                 { "icmp unreach response" },
1008                 { "icmp ping response" },
1009                 { "icmp tstamp response" },
1010                 { "closed port RST response" },
1011                 { "open port RST response" },
1012                 { "icmp6 unreach response" },
1013                 { "sctp ootb response" }
1014         };
1015
1016         /*
1017          * Return ok status if feature disabled or argument out of range.
1018          */
1019         if (V_icmplim > 0 && (u_int) which < N(rates)) {
1020                 struct rate *r = &rates[which];
1021                 int opps = r->curpps;
1022
1023                 if (!ppsratecheck(&r->lasttime, &r->curpps, V_icmplim))
1024                         return -1;      /* discard packet */
1025                 /*
1026                  * If we've dropped below the threshold after having
1027                  * rate-limited traffic print the message.  This preserves
1028                  * the previous behaviour at the expense of added complexity.
1029                  */
1030                 if (V_icmplim_output && opps > V_icmplim)
1031                         log(LOG_NOTICE, "Limiting %s from %d to %d packets/sec\n",
1032                                 r->type, opps, V_icmplim);
1033         }
1034         return 0;                       /* okay to send packet */
1035 #undef N
1036 }