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