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