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   1 /*
   2  *      NET3:   Implementation of the ICMP protocol layer.
   3  *
   4  *              Alan Cox, <alan@redhat.com>
   5  *
   6  *      Version: $Id: icmp.c,v 1.85 2002/02/01 22:01:03 davem Exp $
   7  *
   8  *      This program is free software; you can redistribute it and/or
   9  *      modify it under the terms of the GNU General Public License
  10  *      as published by the Free Software Foundation; either version
  11  *      2 of the License, or (at your option) any later version.
  12  *
  13  *      Some of the function names and the icmp unreach table for this
  14  *      module were derived from [icmp.c 1.0.11 06/02/93] by
  15  *      Ross Biro, Fred N. van Kempen, Mark Evans, Alan Cox, Gerhard Koerting.
  16  *      Other than that this module is a complete rewrite.
  17  *
  18  *      Fixes:
  19  *      Clemens Fruhwirth       :       introduce global icmp rate limiting
  20  *                                      with icmp type masking ability instead
  21  *                                      of broken per type icmp timeouts.
  22  *              Mike Shaver     :       RFC1122 checks.
  23  *              Alan Cox        :       Multicast ping reply as self.
  24  *              Alan Cox        :       Fix atomicity lockup in ip_build_xmit
  25  *                                      call.
  26  *              Alan Cox        :       Added 216,128 byte paths to the MTU
  27  *                                      code.
  28  *              Martin Mares    :       RFC1812 checks.
  29  *              Martin Mares    :       Can be configured to follow redirects
  30  *                                      if acting as a router _without_ a
  31  *                                      routing protocol (RFC 1812).
  32  *              Martin Mares    :       Echo requests may be configured to
  33  *                                      be ignored (RFC 1812).
  34  *              Martin Mares    :       Limitation of ICMP error message
  35  *                                      transmit rate (RFC 1812).
  36  *              Martin Mares    :       TOS and Precedence set correctly
  37  *                                      (RFC 1812).
  38  *              Martin Mares    :       Now copying as much data from the
  39  *                                      original packet as we can without
  40  *                                      exceeding 576 bytes (RFC 1812).
  41  *      Willy Konynenberg       :       Transparent proxying support.
  42  *              Keith Owens     :       RFC1191 correction for 4.2BSD based
  43  *                                      path MTU bug.
  44  *              Thomas Quinot   :       ICMP Dest Unreach codes up to 15 are
  45  *                                      valid (RFC 1812).
  46  *              Andi Kleen      :       Check all packet lengths properly
  47  *                                      and moved all kfree_skb() up to
  48  *                                      icmp_rcv.
  49  *              Andi Kleen      :       Move the rate limit bookkeeping
  50  *                                      into the dest entry and use a token
  51  *                                      bucket filter (thanks to ANK). Make
  52  *                                      the rates sysctl configurable.
  53  *              Yu Tianli       :       Fixed two ugly bugs in icmp_send
  54  *                                      - IP option length was accounted wrongly
  55  *                                      - ICMP header length was not accounted
  56  *                                        at all.
  57  *              Tristan Greaves :       Added sysctl option to ignore bogus
  58  *                                      broadcast responses from broken routers.
  59  *
  60  * To Fix:
  61  *
  62  *      - Should use skb_pull() instead of all the manual checking.
  63  *        This would also greatly simply some upper layer error handlers. --AK
  64  *
  65  */
  66
  67 #include <linux/config.h>
  68 #include <linux/module.h>
  69 #include <linux/types.h>
  70 #include <linux/jiffies.h>
  71 #include <linux/kernel.h>
  72 #include <linux/fcntl.h>
  73 #include <linux/socket.h>
  74 #include <linux/in.h>
  75 #include <linux/inet.h>
  76 #include <linux/inetdevice.h>
  77 #include <linux/netdevice.h>
  78 #include <linux/string.h>
  79 #include <linux/netfilter_ipv4.h>
  80 #include <net/snmp.h>
  81 #include <net/ip.h>
  82 #include <net/route.h>
  83 #include <net/protocol.h>
  84 #include <net/icmp.h>
  85 #include <net/tcp.h>
  86 #include <net/udp.h>
  87 #include <net/raw.h>
  88 #include <linux/skbuff.h>
  89 #include <net/sock.h>
  90 #include <linux/errno.h>
  91 #include <linux/timer.h>
  92 #include <linux/init.h>
  93 #include <asm/system.h>
  94 #include <asm/uaccess.h>
  95 #include <net/checksum.h>
  96
  97 /*
  98  *      Build xmit assembly blocks
  99  */
 100
 101 struct icmp_bxm {
 102         struct sk_buff *skb;
 103         int offset;
 104         int data_len;
 105
 106         struct {
 107                 struct icmphdr icmph;
 108                 __u32          times[3];
 109         } data;
 110         int head_len;
 111         struct ip_options replyopts;
 112         unsigned char  optbuf[40];
 113 };
 114
 115 /*
 116  *      Statistics
 117  */
 118 DEFINE_SNMP_STAT(struct icmp_mib, icmp_statistics) __read_mostly;
 119
 120 /* An array of errno for error messages from dest unreach. */
 121 /* RFC 1122: 3.2.2.1 States that NET_UNREACH, HOST_UNREACH and SR_FAILED MUST be considered 'transient errs'. */
 122
 123 struct icmp_err icmp_err_convert[] = {
 124         {
 125                 .errno = ENETUNREACH,   /* ICMP_NET_UNREACH */
 126                 .fatal = 0,
 127         },
 128         {
 129                 .errno = EHOSTUNREACH,  /* ICMP_HOST_UNREACH */
 130                 .fatal = 0,
 131         },
 132         {
 133                 .errno = ENOPROTOOPT    /* ICMP_PROT_UNREACH */,
 134                 .fatal = 1,
 135         },
 136         {
 137                 .errno = ECONNREFUSED,  /* ICMP_PORT_UNREACH */
 138                 .fatal = 1,
 139         },
 140         {
 141                 .errno = EMSGSIZE,      /* ICMP_FRAG_NEEDED */
 142                 .fatal = 0,
 143         },
 144         {
 145                 .errno = EOPNOTSUPP,    /* ICMP_SR_FAILED */
 146                 .fatal = 0,
 147         },
 148         {
 149                 .errno = ENETUNREACH,   /* ICMP_NET_UNKNOWN */
 150                 .fatal = 1,
 151         },
 152         {
 153                 .errno = EHOSTDOWN,     /* ICMP_HOST_UNKNOWN */
 154                 .fatal = 1,
 155         },
 156         {
 157                 .errno = ENONET,        /* ICMP_HOST_ISOLATED */
 158                 .fatal = 1,
 159         },
 160         {
 161                 .errno = ENETUNREACH,   /* ICMP_NET_ANO */
 162                 .fatal = 1,
 163         },
 164         {
 165                 .errno = EHOSTUNREACH,  /* ICMP_HOST_ANO */
 166                 .fatal = 1,
 167         },
 168         {
 169                 .errno = ENETUNREACH,   /* ICMP_NET_UNR_TOS */
 170                 .fatal = 0,
 171         },
 172         {
 173                 .errno = EHOSTUNREACH,  /* ICMP_HOST_UNR_TOS */
 174                 .fatal = 0,
 175         },
 176         {
 177                 .errno = EHOSTUNREACH,  /* ICMP_PKT_FILTERED */
 178                 .fatal = 1,
 179         },
 180         {
 181                 .errno = EHOSTUNREACH,  /* ICMP_PREC_VIOLATION */
 182                 .fatal = 1,
 183         },
 184         {
 185                 .errno = EHOSTUNREACH,  /* ICMP_PREC_CUTOFF */
 186                 .fatal = 1,
 187         },
 188 };
 189
 190 /* Control parameters for ECHO replies. */
 191 int sysctl_icmp_echo_ignore_all;
 192 int sysctl_icmp_echo_ignore_broadcasts = 1;
 193
 194 /* Control parameter - ignore bogus broadcast responses? */
 195 int sysctl_icmp_ignore_bogus_error_responses;
 196
 197 /*
 198  *      Configurable global rate limit.
 199  *
 200  *      ratelimit defines tokens/packet consumed for dst->rate_token bucket
 201  *      ratemask defines which icmp types are ratelimited by setting
 202  *      it's bit position.
 203  *
 204  *      default:
 205  *      dest unreachable (3), source quench (4),
 206  *      time exceeded (11), parameter problem (12)
 207  */
 208
 209 int sysctl_icmp_ratelimit = 1 * HZ;
 210 int sysctl_icmp_ratemask = 0x1818;
 211 int sysctl_icmp_errors_use_inbound_ifaddr;
 212
 213 /*
 214  *      ICMP control array. This specifies what to do with each ICMP.
 215  */
 216
 217 struct icmp_control {
 218         int output_entry;       /* Field for increment on output */
 219         int input_entry;        /* Field for increment on input */
 220         void (*handler)(struct sk_buff *skb);
 221         short   error;          /* This ICMP is classed as an error message */
 222 };
 223
 224 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES+1];
 225
 226 /*
 227  *      The ICMP socket(s). This is the most convenient way to flow control
 228  *      our ICMP output as well as maintain a clean interface throughout
 229  *      all layers. All Socketless IP sends will soon be gone.
 230  *
 231  *      On SMP we have one ICMP socket per-cpu.
 232  */
 233 static DEFINE_PER_CPU(struct socket *, __icmp_socket) = NULL;
 234 #define icmp_socket     __get_cpu_var(__icmp_socket)
 235
 236 static __inline__ int icmp_xmit_lock(void)
 237 {
 238         local_bh_disable();
 239
 240         if (unlikely(!spin_trylock(&icmp_socket->sk->sk_lock.slock))) {
 241                 /* This can happen if the output path signals a
 242                  * dst_link_failure() for an outgoing ICMP packet.
 243                  */
 244                 local_bh_enable();
 245                 return 1;
 246         }
 247         return 0;
 248 }
 249
 250 static void icmp_xmit_unlock(void)
 251 {
 252         spin_unlock_bh(&icmp_socket->sk->sk_lock.slock);
 253 }
 254
 255 /*
 256  *      Send an ICMP frame.
 257  */
 258
 259 /*
 260  *      Check transmit rate limitation for given message.
 261  *      The rate information is held in the destination cache now.
 262  *      This function is generic and could be used for other purposes
 263  *      too. It uses a Token bucket filter as suggested by Alexey Kuznetsov.
 264  *
 265  *      Note that the same dst_entry fields are modified by functions in
 266  *      route.c too, but these work for packet destinations while xrlim_allow
 267  *      works for icmp destinations. This means the rate limiting information
 268  *      for one "ip object" is shared - and these ICMPs are twice limited:
 269  *      by source and by destination.
 270  *
 271  *      RFC 1812: 4.3.2.8 SHOULD be able to limit error message rate
 272  *                        SHOULD allow setting of rate limits
 273  *
 274  *      Shared between ICMPv4 and ICMPv6.
 275  */
 276 #define XRLIM_BURST_FACTOR 6
 277 int xrlim_allow(struct dst_entry *dst, int timeout)
 278 {
 279         unsigned long now;
 280         int rc = 0;
 281
 282         now = jiffies;
 283         dst->rate_tokens += now - dst->rate_last;
 284         dst->rate_last = now;
 285         if (dst->rate_tokens > XRLIM_BURST_FACTOR * timeout)
 286                 dst->rate_tokens = XRLIM_BURST_FACTOR * timeout;
 287         if (dst->rate_tokens >= timeout) {
 288                 dst->rate_tokens -= timeout;
 289                 rc = 1;
 290         }
 291         return rc;
 292 }
 293
 294 static inline int icmpv4_xrlim_allow(struct rtable *rt, int type, int code)
 295 {
 296         struct dst_entry *dst = &rt->u.dst;
 297         int rc = 1;
 298
 299         if (type > NR_ICMP_TYPES)
 300                 goto out;
 301
 302         /* Don't limit PMTU discovery. */
 303         if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 304                 goto out;
 305
 306         /* No rate limit on loopback */
 307         if (dst->dev && (dst->dev->flags&IFF_LOOPBACK))
 308                 goto out;
 309
 310         /* Limit if icmp type is enabled in ratemask. */
 311         if ((1 << type) & sysctl_icmp_ratemask)
 312                 rc = xrlim_allow(dst, sysctl_icmp_ratelimit);
 313 out:
 314         return rc;
 315 }
 316
 317 /*
 318  *      Maintain the counters used in the SNMP statistics for outgoing ICMP
 319  */
 320 static void icmp_out_count(int type)
 321 {
 322         if (type <= NR_ICMP_TYPES) {
 323                 ICMP_INC_STATS(icmp_pointers[type].output_entry);
 324                 ICMP_INC_STATS(ICMP_MIB_OUTMSGS);
 325         }
 326 }
 327
 328 /*
 329  *      Checksum each fragment, and on the first include the headers and final
 330  *      checksum.
 331  */
 332 static int icmp_glue_bits(void *from, char *to, int offset, int len, int odd,
 333                           struct sk_buff *skb)
 334 {
 335         struct icmp_bxm *icmp_param = (struct icmp_bxm *)from;
 336         unsigned int csum;
 337
 338         csum = skb_copy_and_csum_bits(icmp_param->skb,
 339                                       icmp_param->offset + offset,
 340                                       to, len, 0);
 341
 342         skb->csum = csum_block_add(skb->csum, csum, odd);
 343         if (icmp_pointers[icmp_param->data.icmph.type].error)
 344                 nf_ct_attach(skb, icmp_param->skb);
 345         return 0;
 346 }
 347
 348 static void icmp_push_reply(struct icmp_bxm *icmp_param,
 349                             struct ipcm_cookie *ipc, struct rtable *rt)
 350 {
 351         struct sk_buff *skb;
 352
 353         if (ip_append_data(icmp_socket->sk, icmp_glue_bits, icmp_param,
 354                            icmp_param->data_len+icmp_param->head_len,
 355                            icmp_param->head_len,
 356                            ipc, rt, MSG_DONTWAIT) < 0)
 357                 ip_flush_pending_frames(icmp_socket->sk);
 358         else if ((skb = skb_peek(&icmp_socket->sk->sk_write_queue)) != NULL) {
 359                 struct icmphdr *icmph = skb->h.icmph;
 360                 unsigned int csum = 0;
 361                 struct sk_buff *skb1;
 362
 363                 skb_queue_walk(&icmp_socket->sk->sk_write_queue, skb1) {
 364                         csum = csum_add(csum, skb1->csum);
 365                 }
 366                 csum = csum_partial_copy_nocheck((void *)&icmp_param->data,
 367                                                  (char *)icmph,
 368                                                  icmp_param->head_len, csum);
 369                 icmph->checksum = csum_fold(csum);
 370                 skb->ip_summed = CHECKSUM_NONE;
 371                 ip_push_pending_frames(icmp_socket->sk);
 372         }
 373 }
 374
 375 /*
 376  *      Driving logic for building and sending ICMP messages.
 377  */
 378
 379 static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
 380 {
 381         struct sock *sk = icmp_socket->sk;
 382         struct inet_sock *inet = inet_sk(sk);
 383         struct ipcm_cookie ipc;
 384         struct rtable *rt = (struct rtable *)skb->dst;
 385         u32 daddr;
 386
 387         if (ip_options_echo(&icmp_param->replyopts, skb))
 388                 goto out;
 389
 390         if (icmp_xmit_lock())
 391                 return;
 392
 393         icmp_param->data.icmph.checksum = 0;
 394         icmp_out_count(icmp_param->data.icmph.type);
 395
 396         inet->tos = skb->nh.iph->tos;
 397         daddr = ipc.addr = rt->rt_src;
 398         ipc.opt = NULL;
 399         if (icmp_param->replyopts.optlen) {
 400                 ipc.opt = &icmp_param->replyopts;
 401                 if (ipc.opt->srr)
 402                         daddr = icmp_param->replyopts.faddr;
 403         }
 404         {
 405                 struct flowi fl = { .nl_u = { .ip4_u =
 406                                               { .daddr = daddr,
 407                                                 .saddr = rt->rt_spec_dst,
 408                                                 .tos = RT_TOS(skb->nh.iph->tos) } },
 409                                     .proto = IPPROTO_ICMP };
 410                 if (ip_route_output_key(&rt, &fl))
 411                         goto out_unlock;
 412         }
 413         if (icmpv4_xrlim_allow(rt, icmp_param->data.icmph.type,
 414                                icmp_param->data.icmph.code))
 415                 icmp_push_reply(icmp_param, &ipc, rt);
 416         ip_rt_put(rt);
 417 out_unlock:
 418         icmp_xmit_unlock();
 419 out:;
 420 }
 421
 422
 423 /*
 424  *      Send an ICMP message in response to a situation
 425  *
 426  *      RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header.
 427  *                MAY send more (we do).
 428  *                      MUST NOT change this header information.
 429  *                      MUST NOT reply to a multicast/broadcast IP address.
 430  *                      MUST NOT reply to a multicast/broadcast MAC address.
 431  *                      MUST reply to only the first fragment.
 432  */
 433
 434 void icmp_send(struct sk_buff *skb_in, int type, int code, u32 info)
 435 {
 436         struct iphdr *iph;
 437         int room;
 438         struct icmp_bxm icmp_param;
 439         struct rtable *rt = (struct rtable *)skb_in->dst;
 440         struct ipcm_cookie ipc;
 441         u32 saddr;
 442         u8  tos;
 443
 444         if (!rt)
 445                 goto out;
 446
 447         /*
 448          *      Find the original header. It is expected to be valid, of course.
 449          *      Check this, icmp_send is called from the most obscure devices
 450          *      sometimes.
 451          */
 452         iph = skb_in->nh.iph;
 453
 454         if ((u8 *)iph < skb_in->head || (u8 *)(iph + 1) > skb_in->tail)
 455                 goto out;
 456
 457         /*
 458          *      No replies to physical multicast/broadcast
 459          */
 460         if (skb_in->pkt_type != PACKET_HOST)
 461                 goto out;
 462
 463         /*
 464          *      Now check at the protocol level
 465          */
 466         if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
 467                 goto out;
 468
 469         /*
 470          *      Only reply to fragment 0. We byte re-order the constant
 471          *      mask for efficiency.
 472          */
 473         if (iph->frag_off & htons(IP_OFFSET))
 474                 goto out;
 475
 476         /*
 477          *      If we send an ICMP error to an ICMP error a mess would result..
 478          */
 479         if (icmp_pointers[type].error) {
 480                 /*
 481                  *      We are an error, check if we are replying to an
 482                  *      ICMP error
 483                  */
 484                 if (iph->protocol == IPPROTO_ICMP) {
 485                         u8 _inner_type, *itp;
 486
 487                         itp = skb_header_pointer(skb_in,
 488                                                  skb_in->nh.raw +
 489                                                  (iph->ihl << 2) +
 490                                                  offsetof(struct icmphdr,
 491                                                           type) -
 492                                                  skb_in->data,
 493                                                  sizeof(_inner_type),
 494                                                  &_inner_type);
 495                         if (itp == NULL)
 496                                 goto out;
 497
 498                         /*
 499                          *      Assume any unknown ICMP type is an error. This
 500                          *      isn't specified by the RFC, but think about it..
 501                          */
 502                         if (*itp > NR_ICMP_TYPES ||
 503                             icmp_pointers[*itp].error)
 504                                 goto out;
 505                 }
 506         }
 507
 508         if (icmp_xmit_lock())
 509                 return;
 510
 511         /*
 512          *      Construct source address and options.
 513          */
 514
 515         saddr = iph->daddr;
 516         if (!(rt->rt_flags & RTCF_LOCAL)) {
 517                 if (sysctl_icmp_errors_use_inbound_ifaddr)
 518                         saddr = inet_select_addr(skb_in->dev, 0, RT_SCOPE_LINK);
 519                 else
 520                         saddr = 0;
 521         }
 522
 523         tos = icmp_pointers[type].error ? ((iph->tos & IPTOS_TOS_MASK) |
 524                                            IPTOS_PREC_INTERNETCONTROL) :
 525                                           iph->tos;
 526
 527         if (ip_options_echo(&icmp_param.replyopts, skb_in))
 528                 goto ende;
 529
 530
 531         /*
 532          *      Prepare data for ICMP header.
 533          */
 534
 535         icmp_param.data.icmph.type       = type;
 536         icmp_param.data.icmph.code       = code;
 537         icmp_param.data.icmph.un.gateway = info;
 538         icmp_param.data.icmph.checksum   = 0;
 539         icmp_param.skb    = skb_in;
 540         icmp_param.offset = skb_in->nh.raw - skb_in->data;
 541         icmp_out_count(icmp_param.data.icmph.type);
 542         inet_sk(icmp_socket->sk)->tos = tos;
 543         ipc.addr = iph->saddr;
 544         ipc.opt = &icmp_param.replyopts;
 545
 546         {
 547                 struct flowi fl = {
 548                         .nl_u = {
 549                                 .ip4_u = {
 550                                         .daddr = icmp_param.replyopts.srr ?
 551                                                 icmp_param.replyopts.faddr :
 552                                                 iph->saddr,
 553                                         .saddr = saddr,
 554                                         .tos = RT_TOS(tos)
 555                                 }
 556                         },
 557                         .proto = IPPROTO_ICMP,
 558                         .uli_u = {
 559                                 .icmpt = {
 560                                         .type = type,
 561                                         .code = code
 562                                 }
 563                         }
 564                 };
 565                 if (ip_route_output_key(&rt, &fl))
 566                         goto out_unlock;
 567         }
 568
 569         if (!icmpv4_xrlim_allow(rt, type, code))
 570                 goto ende;
 571
 572         /* RFC says return as much as we can without exceeding 576 bytes. */
 573
 574         room = dst_mtu(&rt->u.dst);
 575         if (room > 576)
 576                 room = 576;
 577         room -= sizeof(struct iphdr) + icmp_param.replyopts.optlen;
 578         room -= sizeof(struct icmphdr);
 579
 580         icmp_param.data_len = skb_in->len - icmp_param.offset;
 581         if (icmp_param.data_len > room)
 582                 icmp_param.data_len = room;
 583         icmp_param.head_len = sizeof(struct icmphdr);
 584
 585         icmp_push_reply(&icmp_param, &ipc, rt);
 586 ende:
 587         ip_rt_put(rt);
 588 out_unlock:
 589         icmp_xmit_unlock();
 590 out:;
 591 }
 592
 593
 594 /*
 595  *      Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEED, and ICMP_QUENCH.
 596  */
 597
 598 static void icmp_unreach(struct sk_buff *skb)
 599 {
 600         struct iphdr *iph;
 601         struct icmphdr *icmph;
 602         int hash, protocol;
 603         struct net_protocol *ipprot;
 604         struct sock *raw_sk;
 605         u32 info = 0;
 606
 607         /*
 608          *      Incomplete header ?
 609          *      Only checks for the IP header, there should be an
 610          *      additional check for longer headers in upper levels.
 611          */
 612
 613         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
 614                 goto out_err;
 615
 616         icmph = skb->h.icmph;
 617         iph   = (struct iphdr *)skb->data;
 618
 619         if (iph->ihl < 5) /* Mangled header, drop. */
 620                 goto out_err;
 621
 622         if (icmph->type == ICMP_DEST_UNREACH) {
 623                 switch (icmph->code & 15) {
 624                 case ICMP_NET_UNREACH:
 625                 case ICMP_HOST_UNREACH:
 626                 case ICMP_PROT_UNREACH:
 627                 case ICMP_PORT_UNREACH:
 628                         break;
 629                 case ICMP_FRAG_NEEDED:
 630                         if (ipv4_config.no_pmtu_disc) {
 631                                 LIMIT_NETDEBUG(KERN_INFO "ICMP: %u.%u.%u.%u: "
 632                                                          "fragmentation needed "
 633                                                          "and DF set.\n",
 634                                                NIPQUAD(iph->daddr));
 635                         } else {
 636                                 info = ip_rt_frag_needed(iph,
 637                                                      ntohs(icmph->un.frag.mtu));
 638                                 if (!info)
 639                                         goto out;
 640                         }
 641                         break;
 642                 case ICMP_SR_FAILED:
 643                         LIMIT_NETDEBUG(KERN_INFO "ICMP: %u.%u.%u.%u: Source "
 644                                                  "Route Failed.\n",
 645                                        NIPQUAD(iph->daddr));
 646                         break;
 647                 default:
 648                         break;
 649                 }
 650                 if (icmph->code > NR_ICMP_UNREACH)
 651                         goto out;
 652         } else if (icmph->type == ICMP_PARAMETERPROB)
 653                 info = ntohl(icmph->un.gateway) >> 24;
 654
 655         /*
 656          *      Throw it at our lower layers
 657          *
 658          *      RFC 1122: 3.2.2 MUST extract the protocol ID from the passed
 659          *                header.
 660          *      RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the
 661          *                transport layer.
 662          *      RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to
 663          *                transport layer.
 664          */
 665
 666         /*
 667          *      Check the other end isnt violating RFC 1122. Some routers send
 668          *      bogus responses to broadcast frames. If you see this message
 669          *      first check your netmask matches at both ends, if it does then
 670          *      get the other vendor to fix their kit.
 671          */
 672
 673         if (!sysctl_icmp_ignore_bogus_error_responses &&
 674             inet_addr_type(iph->daddr) == RTN_BROADCAST) {
 675                 if (net_ratelimit())
 676                         printk(KERN_WARNING "%u.%u.%u.%u sent an invalid ICMP "
 677                                             "type %u, code %u "
 678                                             "error to a broadcast: %u.%u.%u.%u on %s\n",
 679                                NIPQUAD(skb->nh.iph->saddr),
 680                                icmph->type, icmph->code,
 681                                NIPQUAD(iph->daddr),
 682                                skb->dev->name);
 683                 goto out;
 684         }
 685
 686         /* Checkin full IP header plus 8 bytes of protocol to
 687          * avoid additional coding at protocol handlers.
 688          */
 689         if (!pskb_may_pull(skb, iph->ihl * 4 + 8))
 690                 goto out;
 691
 692         iph = (struct iphdr *)skb->data;
 693         protocol = iph->protocol;
 694
 695         /*
 696          *      Deliver ICMP message to raw sockets. Pretty useless feature?
 697          */
 698
 699         /* Note: See raw.c and net/raw.h, RAWV4_HTABLE_SIZE==MAX_INET_PROTOS */
 700         hash = protocol & (MAX_INET_PROTOS - 1);
 701         read_lock(&raw_v4_lock);
 702         if ((raw_sk = sk_head(&raw_v4_htable[hash])) != NULL) {
 703                 while ((raw_sk = __raw_v4_lookup(raw_sk, protocol, iph->daddr,
 704                                                  iph->saddr,
 705                                                  skb->dev->ifindex)) != NULL) {
 706                         raw_err(raw_sk, skb, info);
 707                         raw_sk = sk_next(raw_sk);
 708                         iph = (struct iphdr *)skb->data;
 709                 }
 710         }
 711         read_unlock(&raw_v4_lock);
 712
 713         rcu_read_lock();
 714         ipprot = rcu_dereference(inet_protos[hash]);
 715         if (ipprot && ipprot->err_handler)
 716                 ipprot->err_handler(skb, info);
 717         rcu_read_unlock();
 718
 719 out:
 720         return;
 721 out_err:
 722         ICMP_INC_STATS_BH(ICMP_MIB_INERRORS);
 723         goto out;
 724 }
 725
 726
 727 /*
 728  *      Handle ICMP_REDIRECT.
 729  */
 730
 731 static void icmp_redirect(struct sk_buff *skb)
 732 {
 733         struct iphdr *iph;
 734         unsigned long ip;
 735
 736         if (skb->len < sizeof(struct iphdr))
 737                 goto out_err;
 738
 739         /*
 740          *      Get the copied header of the packet that caused the redirect
 741          */
 742         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
 743                 goto out;
 744
 745         iph = (struct iphdr *)skb->data;
 746         ip = iph->daddr;
 747
 748         switch (skb->h.icmph->code & 7) {
 749         case ICMP_REDIR_NET:
 750         case ICMP_REDIR_NETTOS:
 751                 /*
 752                  * As per RFC recommendations now handle it as a host redirect.
 753                  */
 754         case ICMP_REDIR_HOST:
 755         case ICMP_REDIR_HOSTTOS:
 756                 ip_rt_redirect(skb->nh.iph->saddr, ip, skb->h.icmph->un.gateway,
 757                                iph->saddr, iph->tos, skb->dev);
 758                 break;
 759         }
 760 out:
 761         return;
 762 out_err:
 763         ICMP_INC_STATS_BH(ICMP_MIB_INERRORS);
 764         goto out;
 765 }
 766
 767 /*
 768  *      Handle ICMP_ECHO ("ping") requests.
 769  *
 770  *      RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo
 771  *                requests.
 772  *      RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be
 773  *                included in the reply.
 774  *      RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring
 775  *                echo requests, MUST have default=NOT.
 776  *      See also WRT handling of options once they are done and working.
 777  */
 778
 779 static void icmp_echo(struct sk_buff *skb)
 780 {
 781         if (!sysctl_icmp_echo_ignore_all) {
 782                 struct icmp_bxm icmp_param;
 783
 784                 icmp_param.data.icmph      = *skb->h.icmph;
 785                 icmp_param.data.icmph.type = ICMP_ECHOREPLY;
 786                 icmp_param.skb             = skb;
 787                 icmp_param.offset          = 0;
 788                 icmp_param.data_len        = skb->len;
 789                 icmp_param.head_len        = sizeof(struct icmphdr);
 790                 icmp_reply(&icmp_param, skb);
 791         }
 792 }
 793
 794 /*
 795  *      Handle ICMP Timestamp requests.
 796  *      RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests.
 797  *                SHOULD be in the kernel for minimum random latency.
 798  *                MUST be accurate to a few minutes.
 799  *                MUST be updated at least at 15Hz.
 800  */
 801 static void icmp_timestamp(struct sk_buff *skb)
 802 {
 803         struct timeval tv;
 804         struct icmp_bxm icmp_param;
 805         /*
 806          *      Too short.
 807          */
 808         if (skb->len < 4)
 809                 goto out_err;
 810
 811         /*
 812          *      Fill in the current time as ms since midnight UT:
 813          */
 814         do_gettimeofday(&tv);
 815         icmp_param.data.times[1] = htonl((tv.tv_sec % 86400) * 1000 +
 816                                          tv.tv_usec / 1000);
 817         icmp_param.data.times[2] = icmp_param.data.times[1];
 818         if (skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4))
 819                 BUG();
 820         icmp_param.data.icmph      = *skb->h.icmph;
 821         icmp_param.data.icmph.type = ICMP_TIMESTAMPREPLY;
 822         icmp_param.data.icmph.code = 0;
 823         icmp_param.skb             = skb;
 824         icmp_param.offset          = 0;
 825         icmp_param.data_len        = 0;
 826         icmp_param.head_len        = sizeof(struct icmphdr) + 12;
 827         icmp_reply(&icmp_param, skb);
 828 out:
 829         return;
 830 out_err:
 831         ICMP_INC_STATS_BH(ICMP_MIB_INERRORS);
 832         goto out;
 833 }
 834
 835
 836 /*
 837  *      Handle ICMP_ADDRESS_MASK requests.  (RFC950)
 838  *
 839  * RFC1122 (3.2.2.9).  A host MUST only send replies to
 840  * ADDRESS_MASK requests if it's been configured as an address mask
 841  * agent.  Receiving a request doesn't constitute implicit permission to
 842  * act as one. Of course, implementing this correctly requires (SHOULD)
 843  * a way to turn the functionality on and off.  Another one for sysctl(),
 844  * I guess. -- MS
 845  *
 846  * RFC1812 (4.3.3.9).   A router MUST implement it.
 847  *                      A router SHOULD have switch turning it on/off.
 848  *                      This switch MUST be ON by default.
 849  *
 850  * Gratuitous replies, zero-source replies are not implemented,
 851  * that complies with RFC. DO NOT implement them!!! All the idea
 852  * of broadcast addrmask replies as specified in RFC950 is broken.
 853  * The problem is that it is not uncommon to have several prefixes
 854  * on one physical interface. Moreover, addrmask agent can even be
 855  * not aware of existing another prefixes.
 856  * If source is zero, addrmask agent cannot choose correct prefix.
 857  * Gratuitous mask announcements suffer from the same problem.
 858  * RFC1812 explains it, but still allows to use ADDRMASK,
 859  * that is pretty silly. --ANK
 860  *
 861  * All these rules are so bizarre, that I removed kernel addrmask
 862  * support at all. It is wrong, it is obsolete, nobody uses it in
 863  * any case. --ANK
 864  *
 865  * Furthermore you can do it with a usermode address agent program
 866  * anyway...
 867  */
 868
 869 static void icmp_address(struct sk_buff *skb)
 870 {
 871 #if 0
 872         if (net_ratelimit())
 873                 printk(KERN_DEBUG "a guy asks for address mask. Who is it?\n");
 874 #endif
 875 }
 876
 877 /*
 878  * RFC1812 (4.3.3.9).   A router SHOULD listen all replies, and complain
 879  *                      loudly if an inconsistency is found.
 880  */
 881
 882 static void icmp_address_reply(struct sk_buff *skb)
 883 {
 884         struct rtable *rt = (struct rtable *)skb->dst;
 885         struct net_device *dev = skb->dev;
 886         struct in_device *in_dev;
 887         struct in_ifaddr *ifa;
 888
 889         if (skb->len < 4 || !(rt->rt_flags&RTCF_DIRECTSRC))
 890                 goto out;
 891
 892         in_dev = in_dev_get(dev);
 893         if (!in_dev)
 894                 goto out;
 895         rcu_read_lock();
 896         if (in_dev->ifa_list &&
 897             IN_DEV_LOG_MARTIANS(in_dev) &&
 898             IN_DEV_FORWARD(in_dev)) {
 899                 u32 _mask, *mp;
 900
 901                 mp = skb_header_pointer(skb, 0, sizeof(_mask), &_mask);
 902                 if (mp == NULL)
 903                         BUG();
 904                 for (ifa = in_dev->ifa_list; ifa; ifa = ifa->ifa_next) {
 905                         if (*mp == ifa->ifa_mask &&
 906                             inet_ifa_match(rt->rt_src, ifa))
 907                                 break;
 908                 }
 909                 if (!ifa && net_ratelimit()) {
 910                         printk(KERN_INFO "Wrong address mask %u.%u.%u.%u from "
 911                                          "%s/%u.%u.%u.%u\n",
 912                                NIPQUAD(*mp), dev->name, NIPQUAD(rt->rt_src));
 913                 }
 914         }
 915         rcu_read_unlock();
 916         in_dev_put(in_dev);
 917 out:;
 918 }
 919
 920 static void icmp_discard(struct sk_buff *skb)
 921 {
 922 }
 923
 924 /*
 925  *      Deal with incoming ICMP packets.
 926  */
 927 int icmp_rcv(struct sk_buff *skb)
 928 {
 929         struct icmphdr *icmph;
 930         struct rtable *rt = (struct rtable *)skb->dst;
 931
 932         ICMP_INC_STATS_BH(ICMP_MIB_INMSGS);
 933
 934         switch (skb->ip_summed) {
 935         case CHECKSUM_HW:
 936                 if (!(u16)csum_fold(skb->csum))
 937                         break;
 938                 /* fall through */
 939         case CHECKSUM_NONE:
 940                 skb->csum = 0;
 941                 if (__skb_checksum_complete(skb))
 942                         goto error;
 943         }
 944
 945         if (!pskb_pull(skb, sizeof(struct icmphdr)))
 946                 goto error;
 947
 948         icmph = skb->h.icmph;
 949
 950         /*
 951          *      18 is the highest 'known' ICMP type. Anything else is a mystery
 952          *
 953          *      RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
 954          *                discarded.
 955          */
 956         if (icmph->type > NR_ICMP_TYPES)
 957                 goto error;
 958
 959
 960         /*
 961          *      Parse the ICMP message
 962          */
 963
 964         if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) {
 965                 /*
 966                  *      RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be
 967                  *        silently ignored (we let user decide with a sysctl).
 968                  *      RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently
 969                  *        discarded if to broadcast/multicast.
 970                  */
 971                 if ((icmph->type == ICMP_ECHO ||
 972                      icmph->type == ICMP_TIMESTAMP) &&
 973                     sysctl_icmp_echo_ignore_broadcasts) {
 974                         goto error;
 975                 }
 976                 if (icmph->type != ICMP_ECHO &&
 977                     icmph->type != ICMP_TIMESTAMP &&
 978                     icmph->type != ICMP_ADDRESS &&
 979                     icmph->type != ICMP_ADDRESSREPLY) {
 980                         goto error;
 981                 }
 982         }
 983
 984         ICMP_INC_STATS_BH(icmp_pointers[icmph->type].input_entry);
 985         icmp_pointers[icmph->type].handler(skb);
 986
 987 drop:
 988         kfree_skb(skb);
 989         return 0;
 990 error:
 991         ICMP_INC_STATS_BH(ICMP_MIB_INERRORS);
 992         goto drop;
 993 }
 994
 995 /*
 996  *      This table is the definition of how we handle ICMP.
 997  */
 998 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = {
 999         [ICMP_ECHOREPLY] = {
1000                 .output_entry = ICMP_MIB_OUTECHOREPS,
1001                 .input_entry = ICMP_MIB_INECHOREPS,
1002                 .handler = icmp_discard,
1003         },
1004         [1] = {
1005                 .output_entry = ICMP_MIB_DUMMY,
1006                 .input_entry = ICMP_MIB_INERRORS,
1007                 .handler = icmp_discard,
1008                 .error = 1,
1009         },
1010         [2] = {
1011                 .output_entry = ICMP_MIB_DUMMY,
1012                 .input_entry = ICMP_MIB_INERRORS,
1013                 .handler = icmp_discard,
1014                 .error = 1,
1015         },
1016         [ICMP_DEST_UNREACH] = {
1017                 .output_entry = ICMP_MIB_OUTDESTUNREACHS,
1018                 .input_entry = ICMP_MIB_INDESTUNREACHS,
1019                 .handler = icmp_unreach,
1020                 .error = 1,
1021         },
1022         [ICMP_SOURCE_QUENCH] = {
1023                 .output_entry = ICMP_MIB_OUTSRCQUENCHS,
1024                 .input_entry = ICMP_MIB_INSRCQUENCHS,
1025                 .handler = icmp_unreach,
1026                 .error = 1,
1027         },
1028         [ICMP_REDIRECT] = {
1029                 .output_entry = ICMP_MIB_OUTREDIRECTS,
1030                 .input_entry = ICMP_MIB_INREDIRECTS,
1031                 .handler = icmp_redirect,
1032                 .error = 1,
1033         },
1034         [6] = {
1035                 .output_entry = ICMP_MIB_DUMMY,
1036                 .input_entry = ICMP_MIB_INERRORS,
1037                 .handler = icmp_discard,
1038                 .error = 1,
1039         },
1040         [7] = {
1041                 .output_entry = ICMP_MIB_DUMMY,
1042                 .input_entry = ICMP_MIB_INERRORS,
1043                 .handler = icmp_discard,
1044                 .error = 1,
1045         },
1046         [ICMP_ECHO] = {
1047                 .output_entry = ICMP_MIB_OUTECHOS,
1048                 .input_entry = ICMP_MIB_INECHOS,
1049                 .handler = icmp_echo,
1050         },
1051         [9] = {
1052                 .output_entry = ICMP_MIB_DUMMY,
1053                 .input_entry = ICMP_MIB_INERRORS,
1054                 .handler = icmp_discard,
1055                 .error = 1,
1056         },
1057         [10] = {
1058                 .output_entry = ICMP_MIB_DUMMY,
1059                 .input_entry = ICMP_MIB_INERRORS,
1060                 .handler = icmp_discard,
1061                 .error = 1,
1062         },
1063         [ICMP_TIME_EXCEEDED] = {
1064                 .output_entry = ICMP_MIB_OUTTIMEEXCDS,
1065                 .input_entry = ICMP_MIB_INTIMEEXCDS,
1066                 .handler = icmp_unreach,
1067                 .error = 1,
1068         },
1069         [ICMP_PARAMETERPROB] = {
1070                 .output_entry = ICMP_MIB_OUTPARMPROBS,
1071                 .input_entry = ICMP_MIB_INPARMPROBS,
1072                 .handler = icmp_unreach,
1073                 .error = 1,
1074         },
1075         [ICMP_TIMESTAMP] = {
1076                 .output_entry = ICMP_MIB_OUTTIMESTAMPS,
1077                 .input_entry = ICMP_MIB_INTIMESTAMPS,
1078                 .handler = icmp_timestamp,
1079         },
1080         [ICMP_TIMESTAMPREPLY] = {
1081                 .output_entry = ICMP_MIB_OUTTIMESTAMPREPS,
1082                 .input_entry = ICMP_MIB_INTIMESTAMPREPS,
1083                 .handler = icmp_discard,
1084         },
1085         [ICMP_INFO_REQUEST] = {
1086                 .output_entry = ICMP_MIB_DUMMY,
1087                 .input_entry = ICMP_MIB_DUMMY,
1088                 .handler = icmp_discard,
1089         },
1090         [ICMP_INFO_REPLY] = {
1091                 .output_entry = ICMP_MIB_DUMMY,
1092                 .input_entry = ICMP_MIB_DUMMY,
1093                 .handler = icmp_discard,
1094         },
1095         [ICMP_ADDRESS] = {
1096                 .output_entry = ICMP_MIB_OUTADDRMASKS,
1097                 .input_entry = ICMP_MIB_INADDRMASKS,
1098                 .handler = icmp_address,
1099         },
1100         [ICMP_ADDRESSREPLY] = {
1101                 .output_entry = ICMP_MIB_OUTADDRMASKREPS,
1102                 .input_entry = ICMP_MIB_INADDRMASKREPS,
1103                 .handler = icmp_address_reply,
1104         },
1105 };
1106
1107 void __init icmp_init(struct net_proto_family *ops)
1108 {
1109         struct inet_sock *inet;
1110         int i;
1111
1112         for_each_cpu(i) {
1113                 int err;
1114
1115                 err = sock_create_kern(PF_INET, SOCK_RAW, IPPROTO_ICMP,
1116                                        &per_cpu(__icmp_socket, i));
1117
1118                 if (err < 0)
1119                         panic("Failed to create the ICMP control socket.\n");
1120
1121                 per_cpu(__icmp_socket, i)->sk->sk_allocation = GFP_ATOMIC;
1122
1123                 /* Enough space for 2 64K ICMP packets, including
1124                  * sk_buff struct overhead.
1125                  */
1126                 per_cpu(__icmp_socket, i)->sk->sk_sndbuf =
1127                         (2 * ((64 * 1024) + sizeof(struct sk_buff)));
1128
1129                 inet = inet_sk(per_cpu(__icmp_socket, i)->sk);
1130                 inet->uc_ttl = -1;
1131                 inet->pmtudisc = IP_PMTUDISC_DONT;
1132
1133                 /* Unhash it so that IP input processing does not even
1134                  * see it, we do not wish this socket to see incoming
1135                  * packets.
1136                  */
1137                 per_cpu(__icmp_socket, i)->sk->sk_prot->unhash(per_cpu(__icmp_socket, i)->sk);
1138         }
1139 }
1140
1141 EXPORT_SYMBOL(icmp_err_convert);
1142 EXPORT_SYMBOL(icmp_send);
1143 EXPORT_SYMBOL(icmp_statistics);
1144 EXPORT_SYMBOL(xrlim_allow);