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  * 3. 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 = mtod(n, struct ip *), *nip;
 189         unsigned oiphlen = oip->ip_hl << 2;
 190         struct icmp *icp;
 191         struct mbuf *m;
 192         unsigned icmplen, icmpelen, nlen;
 193
 194         KASSERT((u_int)type <= ICMP_MAXTYPE, ("%s: illegal ICMP type", __func__));
 195 #ifdef ICMPPRINTFS
 196         if (icmpprintfs)
 197                 printf("icmp_error(%p, %x, %d)\n", oip, type, code);
 198 #endif
 199         if (type != ICMP_REDIRECT)
 200                 ICMPSTAT_INC(icps_error);
 201         /*
 202          * Don't send error:
 203          *  if the original packet was encrypted.
 204          *  if not the first fragment of message.
 205          *  in response to a multicast or broadcast packet.
 206          *  if the old packet protocol was an ICMP error message.
 207          */
 208         if (n->m_flags & M_DECRYPTED)
 209                 goto freeit;
 210         if (oip->ip_off & htons(~(IP_MF|IP_DF)))
 211                 goto freeit;
 212         if (n->m_flags & (M_BCAST|M_MCAST))
 213                 goto freeit;
 214         if (oip->ip_p == IPPROTO_ICMP && type != ICMP_REDIRECT &&
 215           n->m_len >= oiphlen + ICMP_MINLEN &&
 216           !ICMP_INFOTYPE(((struct icmp *)((caddr_t)oip + oiphlen))->icmp_type)) {
 217                 ICMPSTAT_INC(icps_oldicmp);
 218                 goto freeit;
 219         }
 220         /* Drop if IP header plus 8 bytes is not contignous in first mbuf. */
 221         if (oiphlen + 8 > n->m_len)
 222                 goto freeit;
 223         /*
 224          * Calculate length to quote from original packet and
 225          * prevent the ICMP mbuf from overflowing.
 226          * Unfortunately this is non-trivial since ip_forward()
 227          * sends us truncated packets.
 228          */
 229         nlen = m_length(n, NULL);
 230         if (oip->ip_p == IPPROTO_TCP) {
 231                 struct tcphdr *th;
 232                 int tcphlen;
 233
 234                 if (oiphlen + sizeof(struct tcphdr) > n->m_len &&
 235                     n->m_next == NULL)
 236                         goto stdreply;
 237                 if (n->m_len < oiphlen + sizeof(struct tcphdr) &&
 238                     ((n = m_pullup(n, oiphlen + sizeof(struct tcphdr))) == NULL))
 239                         goto freeit;
 240                 th = (struct tcphdr *)((caddr_t)oip + oiphlen);
 241                 tcphlen = th->th_off << 2;
 242                 if (tcphlen < sizeof(struct tcphdr))
 243                         goto freeit;
 244                 if (ntohs(oip->ip_len) < oiphlen + tcphlen)
 245                         goto freeit;
 246                 if (oiphlen + tcphlen > n->m_len && n->m_next == NULL)
 247                         goto stdreply;
 248                 if (n->m_len < oiphlen + tcphlen &&
 249                     ((n = m_pullup(n, oiphlen + tcphlen)) == NULL))
 250                         goto freeit;
 251                 icmpelen = max(tcphlen, min(V_icmp_quotelen,
 252                     ntohs(oip->ip_len) - oiphlen));
 253         } else if (oip->ip_p == IPPROTO_SCTP) {
 254                 struct sctphdr *sh;
 255                 struct sctp_chunkhdr *ch;
 256
 257                 if (ntohs(oip->ip_len) < oiphlen + sizeof(struct sctphdr))
 258                         goto stdreply;
 259                 if (oiphlen + sizeof(struct sctphdr) > n->m_len &&
 260                     n->m_next == NULL)
 261                         goto stdreply;
 262                 if (n->m_len < oiphlen + sizeof(struct sctphdr) &&
 263                     (n = m_pullup(n, oiphlen + sizeof(struct sctphdr))) == NULL)
 264                         goto freeit;
 265                 icmpelen = max(sizeof(struct sctphdr),
 266                     min(V_icmp_quotelen, ntohs(oip->ip_len) - oiphlen));
 267                 sh = (struct sctphdr *)((caddr_t)oip + oiphlen);
 268                 if (ntohl(sh->v_tag) == 0 &&
 269                     ntohs(oip->ip_len) >= oiphlen + sizeof(struct sctphdr) + 8 &&
 270                     (n->m_len >= oiphlen + sizeof(struct sctphdr) + 8 ||
 271                      n->m_next != NULL)) {
 272                         if (n->m_len < oiphlen + sizeof(struct sctphdr) + 8 &&
 273                             (n = m_pullup(n, oiphlen + sizeof(struct sctphdr) + 8)) == NULL)
 274                                 goto freeit;
 275                         ch = (struct sctp_chunkhdr *)(sh + 1);
 276                         if (ch->chunk_type == SCTP_INITIATION) {
 277                                 icmpelen = max(sizeof(struct sctphdr) + 8,
 278                                     min(V_icmp_quotelen, ntohs(oip->ip_len) - oiphlen));
 279                         }
 280                 }
 281         } else
 282 stdreply:       icmpelen = max(8, min(V_icmp_quotelen, ntohs(oip->ip_len) - oiphlen));
 283
 284         icmplen = min(oiphlen + icmpelen, nlen);
 285         if (icmplen < sizeof(struct ip))
 286                 goto freeit;
 287
 288         if (MHLEN > sizeof(struct ip) + ICMP_MINLEN + icmplen)
 289                 m = m_gethdr(M_NOWAIT, MT_DATA);
 290         else
 291                 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR);
 292         if (m == NULL)
 293                 goto freeit;
 294 #ifdef MAC
 295         mac_netinet_icmp_reply(n, m);
 296 #endif
 297         icmplen = min(icmplen, M_TRAILINGSPACE(m) - sizeof(struct ip) - ICMP_MINLEN);
 298         m_align(m, ICMP_MINLEN + icmplen);
 299         m->m_len = ICMP_MINLEN + icmplen;
 300
 301         /* XXX MRT  make the outgoing packet use the same FIB
 302          * that was associated with the incoming packet
 303          */
 304         M_SETFIB(m, M_GETFIB(n));
 305         icp = mtod(m, struct icmp *);
 306         ICMPSTAT_INC(icps_outhist[type]);
 307         icp->icmp_type = type;
 308         if (type == ICMP_REDIRECT)
 309                 icp->icmp_gwaddr.s_addr = dest;
 310         else {
 311                 icp->icmp_void = 0;
 312                 /*
 313                  * The following assignments assume an overlay with the
 314                  * just zeroed icmp_void field.
 315                  */
 316                 if (type == ICMP_PARAMPROB) {
 317                         icp->icmp_pptr = code;
 318                         code = 0;
 319                 } else if (type == ICMP_UNREACH &&
 320                         code == ICMP_UNREACH_NEEDFRAG && mtu) {
 321                         icp->icmp_nextmtu = htons(mtu);
 322                 }
 323         }
 324         icp->icmp_code = code;
 325
 326         /*
 327          * Copy the quotation into ICMP message and
 328          * convert quoted IP header back to network representation.
 329          */
 330         m_copydata(n, 0, icmplen, (caddr_t)&icp->icmp_ip);
 331         nip = &icp->icmp_ip;
 332
 333         /*
 334          * Set up ICMP message mbuf and copy old IP header (without options
 335          * in front of ICMP message.
 336          * If the original mbuf was meant to bypass the firewall, the error
 337          * reply should bypass as well.
 338          */
 339         m->m_flags |= n->m_flags & M_SKIP_FIREWALL;
 340         m->m_data -= sizeof(struct ip);
 341         m->m_len += sizeof(struct ip);
 342         m->m_pkthdr.len = m->m_len;
 343         m->m_pkthdr.rcvif = n->m_pkthdr.rcvif;
 344         nip = mtod(m, struct ip *);
 345         bcopy((caddr_t)oip, (caddr_t)nip, sizeof(struct ip));
 346         nip->ip_len = htons(m->m_len);
 347         nip->ip_v = IPVERSION;
 348         nip->ip_hl = 5;
 349         nip->ip_p = IPPROTO_ICMP;
 350         nip->ip_tos = 0;
 351         nip->ip_off = 0;
 352         icmp_reflect(m);
 353
 354 freeit:
 355         m_freem(n);
 356 }
 357
 358 /*
 359  * Process a received ICMP message.
 360  */
 361 int
 362 icmp_input(struct mbuf **mp, int *offp, int proto)
 363 {
 364         struct icmp *icp;
 365         struct in_ifaddr *ia;
 366         struct mbuf *m = *mp;
 367         struct ip *ip = mtod(m, struct ip *);
 368         struct sockaddr_in icmpsrc, icmpdst, icmpgw;
 369         int hlen = *offp;
 370         int icmplen = ntohs(ip->ip_len) - *offp;
 371         int i, code;
 372         void (*ctlfunc)(int, struct sockaddr *, void *);
 373         int fibnum;
 374
 375         *mp = NULL;
 376
 377         /*
 378          * Locate icmp structure in mbuf, and check
 379          * that not corrupted and of at least minimum length.
 380          */
 381 #ifdef ICMPPRINTFS
 382         if (icmpprintfs) {
 383                 char srcbuf[INET_ADDRSTRLEN];
 384                 char dstbuf[INET_ADDRSTRLEN];
 385
 386                 printf("icmp_input from %s to %s, len %d\n",
 387                     inet_ntoa_r(ip->ip_src, srcbuf),
 388                     inet_ntoa_r(ip->ip_dst, dstbuf), icmplen);
 389         }
 390 #endif
 391         if (icmplen < ICMP_MINLEN) {
 392                 ICMPSTAT_INC(icps_tooshort);
 393                 goto freeit;
 394         }
 395         i = hlen + min(icmplen, ICMP_ADVLENMIN);
 396         if (m->m_len < i && (m = m_pullup(m, i)) == NULL)  {
 397                 ICMPSTAT_INC(icps_tooshort);
 398                 return (IPPROTO_DONE);
 399         }
 400         ip = mtod(m, struct ip *);
 401         m->m_len -= hlen;
 402         m->m_data += hlen;
 403         icp = mtod(m, struct icmp *);
 404         if (in_cksum(m, icmplen)) {
 405                 ICMPSTAT_INC(icps_checksum);
 406                 goto freeit;
 407         }
 408         m->m_len += hlen;
 409         m->m_data -= hlen;
 410
 411 #ifdef ICMPPRINTFS
 412         if (icmpprintfs)
 413                 printf("icmp_input, type %d code %d\n", icp->icmp_type,
 414                     icp->icmp_code);
 415 #endif
 416
 417         /*
 418          * Message type specific processing.
 419          */
 420         if (icp->icmp_type > ICMP_MAXTYPE)
 421                 goto raw;
 422
 423         /* Initialize */
 424         bzero(&icmpsrc, sizeof(icmpsrc));
 425         icmpsrc.sin_len = sizeof(struct sockaddr_in);
 426         icmpsrc.sin_family = AF_INET;
 427         bzero(&icmpdst, sizeof(icmpdst));
 428         icmpdst.sin_len = sizeof(struct sockaddr_in);
 429         icmpdst.sin_family = AF_INET;
 430         bzero(&icmpgw, sizeof(icmpgw));
 431         icmpgw.sin_len = sizeof(struct sockaddr_in);
 432         icmpgw.sin_family = AF_INET;
 433
 434         ICMPSTAT_INC(icps_inhist[icp->icmp_type]);
 435         code = icp->icmp_code;
 436         switch (icp->icmp_type) {
 437
 438         case ICMP_UNREACH:
 439                 switch (code) {
 440                         case ICMP_UNREACH_NET:
 441                         case ICMP_UNREACH_HOST:
 442                         case ICMP_UNREACH_SRCFAIL:
 443                         case ICMP_UNREACH_NET_UNKNOWN:
 444                         case ICMP_UNREACH_HOST_UNKNOWN:
 445                         case ICMP_UNREACH_ISOLATED:
 446                         case ICMP_UNREACH_TOSNET:
 447                         case ICMP_UNREACH_TOSHOST:
 448                         case ICMP_UNREACH_HOST_PRECEDENCE:
 449                         case ICMP_UNREACH_PRECEDENCE_CUTOFF:
 450                                 code = PRC_UNREACH_NET;
 451                                 break;
 452
 453                         case ICMP_UNREACH_NEEDFRAG:
 454                                 code = PRC_MSGSIZE;
 455                                 break;
 456
 457                         /*
 458                          * RFC 1122, Sections 3.2.2.1 and 4.2.3.9.
 459                          * Treat subcodes 2,3 as immediate RST
 460                          */
 461                         case ICMP_UNREACH_PROTOCOL:
 462                                 code = PRC_UNREACH_PROTOCOL;
 463                                 break;
 464                         case ICMP_UNREACH_PORT:
 465                                 code = PRC_UNREACH_PORT;
 466                                 break;
 467
 468                         case ICMP_UNREACH_NET_PROHIB:
 469                         case ICMP_UNREACH_HOST_PROHIB:
 470                         case ICMP_UNREACH_FILTER_PROHIB:
 471                                 code = PRC_UNREACH_ADMIN_PROHIB;
 472                                 break;
 473
 474                         default:
 475                                 goto badcode;
 476                 }
 477                 goto deliver;
 478
 479         case ICMP_TIMXCEED:
 480                 if (code > 1)
 481                         goto badcode;
 482                 code += PRC_TIMXCEED_INTRANS;
 483                 goto deliver;
 484
 485         case ICMP_PARAMPROB:
 486                 if (code > 1)
 487                         goto badcode;
 488                 code = PRC_PARAMPROB;
 489         deliver:
 490                 /*
 491                  * Problem with datagram; advise higher level routines.
 492                  */
 493                 if (icmplen < ICMP_ADVLENMIN || icmplen < ICMP_ADVLEN(icp) ||
 494                     icp->icmp_ip.ip_hl < (sizeof(struct ip) >> 2)) {
 495                         ICMPSTAT_INC(icps_badlen);
 496                         goto freeit;
 497                 }
 498                 /* Discard ICMP's in response to multicast packets */
 499                 if (IN_MULTICAST(ntohl(icp->icmp_ip.ip_dst.s_addr)))
 500                         goto badcode;
 501 #ifdef ICMPPRINTFS
 502                 if (icmpprintfs)
 503                         printf("deliver to protocol %d\n", icp->icmp_ip.ip_p);
 504 #endif
 505                 icmpsrc.sin_addr = icp->icmp_ip.ip_dst;
 506                 /*
 507                  * XXX if the packet contains [IPv4 AH TCP], we can't make a
 508                  * notification to TCP layer.
 509                  */
 510                 i = sizeof(struct ip) + min(icmplen, ICMP_ADVLENPREF(icp));
 511                 ip_stripoptions(m);
 512                 if (m->m_len < i && (m = m_pullup(m, i)) == NULL) {
 513                         /* This should actually not happen */
 514                         ICMPSTAT_INC(icps_tooshort);
 515                         return (IPPROTO_DONE);
 516                 }
 517                 ip = mtod(m, struct ip *);
 518                 icp = (struct icmp *)(ip + 1);
 519                 /*
 520                  * The upper layer handler can rely on:
 521                  * - The outer IP header has no options.
 522                  * - The outer IP header, the ICMP header, the inner IP header,
 523                  *   and the first n bytes of the inner payload are contiguous.
 524                  *   n is at least 8, but might be larger based on
 525                  *   ICMP_ADVLENPREF. See its definition in ip_icmp.h.
 526                  */
 527                 ctlfunc = inetsw[ip_protox[icp->icmp_ip.ip_p]].pr_ctlinput;
 528                 if (ctlfunc)
 529                         (*ctlfunc)(code, (struct sockaddr *)&icmpsrc,
 530                                    (void *)&icp->icmp_ip);
 531                 break;
 532
 533         badcode:
 534                 ICMPSTAT_INC(icps_badcode);
 535                 break;
 536
 537         case ICMP_ECHO:
 538                 if (!V_icmpbmcastecho
 539                     && (m->m_flags & (M_MCAST | M_BCAST)) != 0) {
 540                         ICMPSTAT_INC(icps_bmcastecho);
 541                         break;
 542                 }
 543                 if (badport_bandlim(BANDLIM_ICMP_ECHO) < 0)
 544                         goto freeit;
 545                 icp->icmp_type = ICMP_ECHOREPLY;
 546                 goto reflect;
 547
 548         case ICMP_TSTAMP:
 549                 if (V_icmptstamprepl == 0)
 550                         break;
 551                 if (!V_icmpbmcastecho
 552                     && (m->m_flags & (M_MCAST | M_BCAST)) != 0) {
 553                         ICMPSTAT_INC(icps_bmcasttstamp);
 554                         break;
 555                 }
 556                 if (icmplen < ICMP_TSLEN) {
 557                         ICMPSTAT_INC(icps_badlen);
 558                         break;
 559                 }
 560                 if (badport_bandlim(BANDLIM_ICMP_TSTAMP) < 0)
 561                         goto freeit;
 562                 icp->icmp_type = ICMP_TSTAMPREPLY;
 563                 icp->icmp_rtime = iptime();
 564                 icp->icmp_ttime = icp->icmp_rtime;      /* bogus, do later! */
 565                 goto reflect;
 566
 567         case ICMP_MASKREQ:
 568                 if (V_icmpmaskrepl == 0)
 569                         break;
 570                 /*
 571                  * We are not able to respond with all ones broadcast
 572                  * unless we receive it over a point-to-point interface.
 573                  */
 574                 if (icmplen < ICMP_MASKLEN)
 575                         break;
 576                 switch (ip->ip_dst.s_addr) {
 577
 578                 case INADDR_BROADCAST:
 579                 case INADDR_ANY:
 580                         icmpdst.sin_addr = ip->ip_src;
 581                         break;
 582
 583                 default:
 584                         icmpdst.sin_addr = ip->ip_dst;
 585                 }
 586                 ia = (struct in_ifaddr *)ifaof_ifpforaddr(
 587                             (struct sockaddr *)&icmpdst, m->m_pkthdr.rcvif);
 588                 if (ia == NULL)
 589                         break;
 590                 if (ia->ia_ifp == NULL) {
 591                         ifa_free(&ia->ia_ifa);
 592                         break;
 593                 }
 594                 icp->icmp_type = ICMP_MASKREPLY;
 595                 if (V_icmpmaskfake == 0)
 596                         icp->icmp_mask = ia->ia_sockmask.sin_addr.s_addr;
 597                 else
 598                         icp->icmp_mask = V_icmpmaskfake;
 599                 if (ip->ip_src.s_addr == 0) {
 600                         if (ia->ia_ifp->if_flags & IFF_BROADCAST)
 601                             ip->ip_src = satosin(&ia->ia_broadaddr)->sin_addr;
 602                         else if (ia->ia_ifp->if_flags & IFF_POINTOPOINT)
 603                             ip->ip_src = satosin(&ia->ia_dstaddr)->sin_addr;
 604                 }
 605                 ifa_free(&ia->ia_ifa);
 606 reflect:
 607                 ICMPSTAT_INC(icps_reflect);
 608                 ICMPSTAT_INC(icps_outhist[icp->icmp_type]);
 609                 icmp_reflect(m);
 610                 return (IPPROTO_DONE);
 611
 612         case ICMP_REDIRECT:
 613                 if (V_log_redirect) {
 614                         u_long src, dst, gw;
 615
 616                         src = ntohl(ip->ip_src.s_addr);
 617                         dst = ntohl(icp->icmp_ip.ip_dst.s_addr);
 618                         gw = ntohl(icp->icmp_gwaddr.s_addr);
 619                         printf("icmp redirect from %d.%d.%d.%d: "
 620                                "%d.%d.%d.%d => %d.%d.%d.%d\n",
 621                                (int)(src >> 24), (int)((src >> 16) & 0xff),
 622                                (int)((src >> 8) & 0xff), (int)(src & 0xff),
 623                                (int)(dst >> 24), (int)((dst >> 16) & 0xff),
 624                                (int)((dst >> 8) & 0xff), (int)(dst & 0xff),
 625                                (int)(gw >> 24), (int)((gw >> 16) & 0xff),
 626                                (int)((gw >> 8) & 0xff), (int)(gw & 0xff));
 627                 }
 628                 /*
 629                  * RFC1812 says we must ignore ICMP redirects if we
 630                  * are acting as router.
 631                  */
 632                 if (V_drop_redirect || V_ipforwarding)
 633                         break;
 634                 if (code > 3)
 635                         goto badcode;
 636                 if (icmplen < ICMP_ADVLENMIN || icmplen < ICMP_ADVLEN(icp) ||
 637                     icp->icmp_ip.ip_hl < (sizeof(struct ip) >> 2)) {
 638                         ICMPSTAT_INC(icps_badlen);
 639                         break;
 640                 }
 641                 /*
 642                  * Short circuit routing redirects to force
 643                  * immediate change in the kernel's routing
 644                  * tables.  The message is also handed to anyone
 645                  * listening on a raw socket (e.g. the routing
 646                  * daemon for use in updating its tables).
 647                  */
 648                 icmpgw.sin_addr = ip->ip_src;
 649                 icmpdst.sin_addr = icp->icmp_gwaddr;
 650 #ifdef  ICMPPRINTFS
 651                 if (icmpprintfs) {
 652                         char dstbuf[INET_ADDRSTRLEN];
 653                         char gwbuf[INET_ADDRSTRLEN];
 654
 655                         printf("redirect dst %s to %s\n",
 656                                inet_ntoa_r(icp->icmp_ip.ip_dst, dstbuf),
 657                                inet_ntoa_r(icp->icmp_gwaddr, gwbuf));
 658                 }
 659 #endif
 660                 icmpsrc.sin_addr = icp->icmp_ip.ip_dst;
 661                 for ( fibnum = 0; fibnum < rt_numfibs; fibnum++) {
 662                         in_rtredirect((struct sockaddr *)&icmpsrc,
 663                           (struct sockaddr *)&icmpdst,
 664                           (struct sockaddr *)0, RTF_GATEWAY | RTF_HOST,
 665                           (struct sockaddr *)&icmpgw, fibnum);
 666                 }
 667                 pfctlinput(PRC_REDIRECT_HOST, (struct sockaddr *)&icmpsrc);
 668                 break;
 669
 670         /*
 671          * No kernel processing for the following;
 672          * just fall through to send to raw listener.
 673          */
 674         case ICMP_ECHOREPLY:
 675         case ICMP_ROUTERADVERT:
 676         case ICMP_ROUTERSOLICIT:
 677         case ICMP_TSTAMPREPLY:
 678         case ICMP_IREQREPLY:
 679         case ICMP_MASKREPLY:
 680         case ICMP_SOURCEQUENCH:
 681         default:
 682                 break;
 683         }
 684
 685 raw:
 686         *mp = m;
 687         rip_input(mp, offp, proto);
 688         return (IPPROTO_DONE);
 689
 690 freeit:
 691         m_freem(m);
 692         return (IPPROTO_DONE);
 693 }
 694
 695 /*
 696  * Reflect the ip packet back to the source
 697  */
 698 static void
 699 icmp_reflect(struct mbuf *m)
 700 {
 701         struct rm_priotracker in_ifa_tracker;
 702         struct ip *ip = mtod(m, struct ip *);
 703         struct ifaddr *ifa;
 704         struct ifnet *ifp;
 705         struct in_ifaddr *ia;
 706         struct in_addr t;
 707         struct nhop4_extended nh_ext;
 708         struct mbuf *opts = NULL;
 709         int optlen = (ip->ip_hl << 2) - sizeof(struct ip);
 710
 711         if (IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
 712             IN_EXPERIMENTAL(ntohl(ip->ip_src.s_addr)) ||
 713             IN_ZERONET(ntohl(ip->ip_src.s_addr)) ) {
 714                 m_freem(m);     /* Bad return address */
 715                 ICMPSTAT_INC(icps_badaddr);
 716                 goto done;      /* Ip_output() will check for broadcast */
 717         }
 718
 719         t = ip->ip_dst;
 720         ip->ip_dst = ip->ip_src;
 721
 722         /*
 723          * Source selection for ICMP replies:
 724          *
 725          * If the incoming packet was addressed directly to one of our
 726          * own addresses, use dst as the src for the reply.
 727          */
 728         IN_IFADDR_RLOCK(&in_ifa_tracker);
 729         LIST_FOREACH(ia, INADDR_HASH(t.s_addr), ia_hash) {
 730                 if (t.s_addr == IA_SIN(ia)->sin_addr.s_addr) {
 731                         t = IA_SIN(ia)->sin_addr;
 732                         IN_IFADDR_RUNLOCK(&in_ifa_tracker);
 733                         goto match;
 734                 }
 735         }
 736         IN_IFADDR_RUNLOCK(&in_ifa_tracker);
 737
 738         /*
 739          * If the incoming packet was addressed to one of our broadcast
 740          * addresses, use the first non-broadcast address which corresponds
 741          * to the incoming interface.
 742          */
 743         ifp = m->m_pkthdr.rcvif;
 744         if (ifp != NULL && ifp->if_flags & IFF_BROADCAST) {
 745                 IF_ADDR_RLOCK(ifp);
 746                 TAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
 747                         if (ifa->ifa_addr->sa_family != AF_INET)
 748                                 continue;
 749                         ia = ifatoia(ifa);
 750                         if (satosin(&ia->ia_broadaddr)->sin_addr.s_addr ==
 751                             t.s_addr) {
 752                                 t = IA_SIN(ia)->sin_addr;
 753                                 IF_ADDR_RUNLOCK(ifp);
 754                                 goto match;
 755                         }
 756                 }
 757                 IF_ADDR_RUNLOCK(ifp);
 758         }
 759         /*
 760          * If the packet was transiting through us, use the address of
 761          * the interface the packet came through in.  If that interface
 762          * doesn't have a suitable IP address, the normal selection
 763          * criteria apply.
 764          */
 765         if (V_icmp_rfi && ifp != NULL) {
 766                 IF_ADDR_RLOCK(ifp);
 767                 TAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
 768                         if (ifa->ifa_addr->sa_family != AF_INET)
 769                                 continue;
 770                         ia = ifatoia(ifa);
 771                         t = IA_SIN(ia)->sin_addr;
 772                         IF_ADDR_RUNLOCK(ifp);
 773                         goto match;
 774                 }
 775                 IF_ADDR_RUNLOCK(ifp);
 776         }
 777         /*
 778          * If the incoming packet was not addressed directly to us, use
 779          * designated interface for icmp replies specified by sysctl
 780          * net.inet.icmp.reply_src (default not set). Otherwise continue
 781          * with normal source selection.
 782          */
 783         if (V_reply_src[0] != '\0' && (ifp = ifunit(V_reply_src))) {
 784                 IF_ADDR_RLOCK(ifp);
 785                 TAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
 786                         if (ifa->ifa_addr->sa_family != AF_INET)
 787                                 continue;
 788                         ia = ifatoia(ifa);
 789                         t = IA_SIN(ia)->sin_addr;
 790                         IF_ADDR_RUNLOCK(ifp);
 791                         goto match;
 792                 }
 793                 IF_ADDR_RUNLOCK(ifp);
 794         }
 795         /*
 796          * If the packet was transiting through us, use the address of
 797          * the interface that is the closest to the packet source.
 798          * When we don't have a route back to the packet source, stop here
 799          * and drop the packet.
 800          */
 801         if (fib4_lookup_nh_ext(M_GETFIB(m), ip->ip_dst, 0, 0, &nh_ext) != 0) {
 802                 m_freem(m);
 803                 ICMPSTAT_INC(icps_noroute);
 804                 goto done;
 805         }
 806         t = nh_ext.nh_src;
 807 match:
 808 #ifdef MAC
 809         mac_netinet_icmp_replyinplace(m);
 810 #endif
 811         ip->ip_src = t;
 812         ip->ip_ttl = V_ip_defttl;
 813
 814         if (optlen > 0) {
 815                 u_char *cp;
 816                 int opt, cnt;
 817                 u_int len;
 818
 819                 /*
 820                  * Retrieve any source routing from the incoming packet;
 821                  * add on any record-route or timestamp options.
 822                  */
 823                 cp = (u_char *) (ip + 1);
 824                 if ((opts = ip_srcroute(m)) == NULL &&
 825                     (opts = m_gethdr(M_NOWAIT, MT_DATA))) {
 826                         opts->m_len = sizeof(struct in_addr);
 827                         mtod(opts, struct in_addr *)->s_addr = 0;
 828                 }
 829                 if (opts) {
 830 #ifdef ICMPPRINTFS
 831                     if (icmpprintfs)
 832                             printf("icmp_reflect optlen %d rt %d => ",
 833                                 optlen, opts->m_len);
 834 #endif
 835                     for (cnt = optlen; cnt > 0; cnt -= len, cp += len) {
 836                             opt = cp[IPOPT_OPTVAL];
 837                             if (opt == IPOPT_EOL)
 838                                     break;
 839                             if (opt == IPOPT_NOP)
 840                                     len = 1;
 841                             else {
 842                                     if (cnt < IPOPT_OLEN + sizeof(*cp))
 843                                             break;
 844                                     len = cp[IPOPT_OLEN];
 845                                     if (len < IPOPT_OLEN + sizeof(*cp) ||
 846                                         len > cnt)
 847                                             break;
 848                             }
 849                             /*
 850                              * Should check for overflow, but it "can't happen"
 851                              */
 852                             if (opt == IPOPT_RR || opt == IPOPT_TS ||
 853                                 opt == IPOPT_SECURITY) {
 854                                     bcopy((caddr_t)cp,
 855                                         mtod(opts, caddr_t) + opts->m_len, len);
 856                                     opts->m_len += len;
 857                             }
 858                     }
 859                     /* Terminate & pad, if necessary */
 860                     cnt = opts->m_len % 4;
 861                     if (cnt) {
 862                             for (; cnt < 4; cnt++) {
 863                                     *(mtod(opts, caddr_t) + opts->m_len) =
 864                                         IPOPT_EOL;
 865                                     opts->m_len++;
 866                             }
 867                     }
 868 #ifdef ICMPPRINTFS
 869                     if (icmpprintfs)
 870                             printf("%d\n", opts->m_len);
 871 #endif
 872                 }
 873                 ip_stripoptions(m);
 874         }
 875         m_tag_delete_nonpersistent(m);
 876         m->m_flags &= ~(M_BCAST|M_MCAST);
 877         icmp_send(m, opts);
 878 done:
 879         if (opts)
 880                 (void)m_free(opts);
 881 }
 882
 883 /*
 884  * Send an icmp packet back to the ip level,
 885  * after supplying a checksum.
 886  */
 887 static void
 888 icmp_send(struct mbuf *m, struct mbuf *opts)
 889 {
 890         struct ip *ip = mtod(m, struct ip *);
 891         int hlen;
 892         struct icmp *icp;
 893
 894         hlen = ip->ip_hl << 2;
 895         m->m_data += hlen;
 896         m->m_len -= hlen;
 897         icp = mtod(m, struct icmp *);
 898         icp->icmp_cksum = 0;
 899         icp->icmp_cksum = in_cksum(m, ntohs(ip->ip_len) - hlen);
 900         m->m_data -= hlen;
 901         m->m_len += hlen;
 902         m->m_pkthdr.rcvif = (struct ifnet *)0;
 903 #ifdef ICMPPRINTFS
 904         if (icmpprintfs) {
 905                 char dstbuf[INET_ADDRSTRLEN];
 906                 char srcbuf[INET_ADDRSTRLEN];
 907
 908                 printf("icmp_send dst %s src %s\n",
 909                     inet_ntoa_r(ip->ip_dst, dstbuf),
 910                     inet_ntoa_r(ip->ip_src, srcbuf));
 911         }
 912 #endif
 913         (void) ip_output(m, opts, NULL, 0, NULL, NULL);
 914 }
 915
 916 /*
 917  * Return milliseconds since 00:00 UTC in network format.
 918  */
 919 uint32_t
 920 iptime(void)
 921 {
 922         struct timeval atv;
 923         u_long t;
 924
 925         getmicrotime(&atv);
 926         t = (atv.tv_sec % (24*60*60)) * 1000 + atv.tv_usec / 1000;
 927         return (htonl(t));
 928 }
 929
 930 /*
 931  * Return the next larger or smaller MTU plateau (table from RFC 1191)
 932  * given current value MTU.  If DIR is less than zero, a larger plateau
 933  * is returned; otherwise, a smaller value is returned.
 934  */
 935 int
 936 ip_next_mtu(int mtu, int dir)
 937 {
 938         static int mtutab[] = {
 939                 65535, 32000, 17914, 8166, 4352, 2002, 1492, 1280, 1006, 508,
 940                 296, 68, 0
 941         };
 942         int i, size;
 943
 944         size = (sizeof mtutab) / (sizeof mtutab[0]);
 945         if (dir >= 0) {
 946                 for (i = 0; i < size; i++)
 947                         if (mtu > mtutab[i])
 948                                 return mtutab[i];
 949         } else {
 950                 for (i = size - 1; i >= 0; i--)
 951                         if (mtu < mtutab[i])
 952                                 return mtutab[i];
 953                 if (mtu == mtutab[0])
 954                         return mtutab[0];
 955         }
 956         return 0;
 957 }
 958 #endif /* INET */
 959
 960
 961 /*
 962  * badport_bandlim() - check for ICMP bandwidth limit
 963  *
 964  *      Return 0 if it is ok to send an ICMP error response, -1 if we have
 965  *      hit our bandwidth limit and it is not ok.
 966  *
 967  *      If icmplim is <= 0, the feature is disabled and 0 is returned.
 968  *
 969  *      For now we separate the TCP and UDP subsystems w/ different 'which'
 970  *      values.  We may eventually remove this separation (and simplify the
 971  *      code further).
 972  *
 973  *      Note that the printing of the error message is delayed so we can
 974  *      properly print the icmp error rate that the system was trying to do
 975  *      (i.e. 22000/100 pps, etc...).  This can cause long delays in printing
 976  *      the 'final' error, but it doesn't make sense to solve the printing
 977  *      delay with more complex code.
 978  */
 979 struct icmp_rate {
 980         const char *descr;
 981         struct counter_rate cr;
 982 };
 983 static VNET_DEFINE(struct icmp_rate, icmp_rates[BANDLIM_MAX]) = {
 984         { "icmp unreach response" },
 985         { "icmp ping response" },
 986         { "icmp tstamp response" },
 987         { "closed port RST response" },
 988         { "open port RST response" },
 989         { "icmp6 unreach response" },
 990         { "sctp ootb response" }
 991 };
 992 #define V_icmp_rates    VNET(icmp_rates)
 993
 994 static void
 995 icmp_bandlimit_init(void)
 996 {
 997
 998         for (int i = 0; i < BANDLIM_MAX; i++) {
 999                 V_icmp_rates[i].cr.cr_rate = counter_u64_alloc(M_WAITOK);
1000                 V_icmp_rates[i].cr.cr_ticks = ticks;
1001         }
1002 }
1003 VNET_SYSINIT(icmp_bandlimit, SI_SUB_PROTO_DOMAIN, SI_ORDER_ANY,
1004     icmp_bandlimit_init, NULL);
1005
1006 static void
1007 icmp_bandlimit_uninit(void)
1008 {
1009
1010         for (int i = 0; i < BANDLIM_MAX; i++)
1011                 counter_u64_free(V_icmp_rates[i].cr.cr_rate);
1012 }
1013 VNET_SYSUNINIT(icmp_bandlimit, SI_SUB_PROTO_DOMAIN, SI_ORDER_THIRD,
1014     icmp_bandlimit_uninit, NULL);
1015
1016 int
1017 badport_bandlim(int which)
1018 {
1019         int64_t pps;
1020
1021         if (V_icmplim == 0 || which == BANDLIM_UNLIMITED)
1022                 return (0);
1023
1024         KASSERT(which >= 0 && which < BANDLIM_MAX,
1025             ("%s: which %d", __func__, which));
1026
1027         pps = counter_ratecheck(&V_icmp_rates[which].cr, V_icmplim);
1028         if (pps == -1)
1029                 return (-1);
1030         if (pps > 0 && V_icmplim_output)
1031                 log(LOG_NOTICE, "Limiting %s from %jd to %d packets/sec\n",
1032                         V_icmp_rates[which].descr, (intmax_t )pps, V_icmplim);
1033         return (0);
1034 }