net/ipv4/icmp.c

   1 /*
   2  *      NET3:   Implementation of the ICMP protocol layer.
   3  *
   4  *              Alan Cox, <alan@lxorguk.ukuu.org.uk>
   5  *
   6  *      This program is free software; you can redistribute it and/or
   7  *      modify it under the terms of the GNU General Public License
   8  *      as published by the Free Software Foundation; either version
   9  *      2 of the License, or (at your option) any later version.
  10  *
  11  *      Some of the function names and the icmp unreach table for this
  12  *      module were derived from [icmp.c 1.0.11 06/02/93] by
  13  *      Ross Biro, Fred N. van Kempen, Mark Evans, Alan Cox, Gerhard Koerting.
  14  *      Other than that this module is a complete rewrite.
  15  *
  16  *      Fixes:
  17  *      Clemens Fruhwirth       :       introduce global icmp rate limiting
  18  *                                      with icmp type masking ability instead
  19  *                                      of broken per type icmp timeouts.
  20  *              Mike Shaver     :       RFC1122 checks.
  21  *              Alan Cox        :       Multicast ping reply as self.
  22  *              Alan Cox        :       Fix atomicity lockup in ip_build_xmit
  23  *                                      call.
  24  *              Alan Cox        :       Added 216,128 byte paths to the MTU
  25  *                                      code.
  26  *              Martin Mares    :       RFC1812 checks.
  27  *              Martin Mares    :       Can be configured to follow redirects
  28  *                                      if acting as a router _without_ a
  29  *                                      routing protocol (RFC 1812).
  30  *              Martin Mares    :       Echo requests may be configured to
  31  *                                      be ignored (RFC 1812).
  32  *              Martin Mares    :       Limitation of ICMP error message
  33  *                                      transmit rate (RFC 1812).
  34  *              Martin Mares    :       TOS and Precedence set correctly
  35  *                                      (RFC 1812).
  36  *              Martin Mares    :       Now copying as much data from the
  37  *                                      original packet as we can without
  38  *                                      exceeding 576 bytes (RFC 1812).
  39  *      Willy Konynenberg       :       Transparent proxying support.
  40  *              Keith Owens     :       RFC1191 correction for 4.2BSD based
  41  *                                      path MTU bug.
  42  *              Thomas Quinot   :       ICMP Dest Unreach codes up to 15 are
  43  *                                      valid (RFC 1812).
  44  *              Andi Kleen      :       Check all packet lengths properly
  45  *                                      and moved all kfree_skb() up to
  46  *                                      icmp_rcv.
  47  *              Andi Kleen      :       Move the rate limit bookkeeping
  48  *                                      into the dest entry and use a token
  49  *                                      bucket filter (thanks to ANK). Make
  50  *                                      the rates sysctl configurable.
  51  *              Yu Tianli       :       Fixed two ugly bugs in icmp_send
  52  *                                      - IP option length was accounted wrongly
  53  *                                      - ICMP header length was not accounted
  54  *                                        at all.
  55  *              Tristan Greaves :       Added sysctl option to ignore bogus
  56  *                                      broadcast responses from broken routers.
  57  *
  58  * To Fix:
  59  *
  60  *      - Should use skb_pull() instead of all the manual checking.
  61  *        This would also greatly simply some upper layer error handlers. --AK
  62  *
  63  */
  64
  65 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  66
  67 #include <linux/module.h>
  68 #include <linux/types.h>
  69 #include <linux/jiffies.h>
  70 #include <linux/kernel.h>
  71 #include <linux/fcntl.h>
  72 #include <linux/socket.h>
  73 #include <linux/in.h>
  74 #include <linux/inet.h>
  75 #include <linux/inetdevice.h>
  76 #include <linux/netdevice.h>
  77 #include <linux/string.h>
  78 #include <linux/netfilter_ipv4.h>
  79 #include <linux/slab.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 <net/ping.h>
  89 #include <linux/skbuff.h>
  90 #include <net/sock.h>
  91 #include <linux/errno.h>
  92 #include <linux/timer.h>
  93 #include <linux/init.h>
  94 #include <asm/uaccess.h>
  95 #include <net/checksum.h>
  96 #include <net/xfrm.h>
  97 #include <net/inet_common.h>
  98
  99 /*
 100  *      Build xmit assembly blocks
 101  */
 102
 103 struct icmp_bxm {
 104         struct sk_buff *skb;
 105         int offset;
 106         int data_len;
 107
 108         struct {
 109                 struct icmphdr icmph;
 110                 __be32         times[3];
 111         } data;
 112         int head_len;
 113         struct ip_options_data replyopts;
 114 };
 115
 116 /* An array of errno for error messages from dest unreach. */
 117 /* RFC 1122: 3.2.2.1 States that NET_UNREACH, HOST_UNREACH and SR_FAILED MUST be considered 'transient errs'. */
 118
 119 const struct icmp_err icmp_err_convert[] = {
 120         {
 121                 .errno = ENETUNREACH,   /* ICMP_NET_UNREACH */
 122                 .fatal = 0,
 123         },
 124         {
 125                 .errno = EHOSTUNREACH,  /* ICMP_HOST_UNREACH */
 126                 .fatal = 0,
 127         },
 128         {
 129                 .errno = ENOPROTOOPT    /* ICMP_PROT_UNREACH */,
 130                 .fatal = 1,
 131         },
 132         {
 133                 .errno = ECONNREFUSED,  /* ICMP_PORT_UNREACH */
 134                 .fatal = 1,
 135         },
 136         {
 137                 .errno = EMSGSIZE,      /* ICMP_FRAG_NEEDED */
 138                 .fatal = 0,
 139         },
 140         {
 141                 .errno = EOPNOTSUPP,    /* ICMP_SR_FAILED */
 142                 .fatal = 0,
 143         },
 144         {
 145                 .errno = ENETUNREACH,   /* ICMP_NET_UNKNOWN */
 146                 .fatal = 1,
 147         },
 148         {
 149                 .errno = EHOSTDOWN,     /* ICMP_HOST_UNKNOWN */
 150                 .fatal = 1,
 151         },
 152         {
 153                 .errno = ENONET,        /* ICMP_HOST_ISOLATED */
 154                 .fatal = 1,
 155         },
 156         {
 157                 .errno = ENETUNREACH,   /* ICMP_NET_ANO */
 158                 .fatal = 1,
 159         },
 160         {
 161                 .errno = EHOSTUNREACH,  /* ICMP_HOST_ANO */
 162                 .fatal = 1,
 163         },
 164         {
 165                 .errno = ENETUNREACH,   /* ICMP_NET_UNR_TOS */
 166                 .fatal = 0,
 167         },
 168         {
 169                 .errno = EHOSTUNREACH,  /* ICMP_HOST_UNR_TOS */
 170                 .fatal = 0,
 171         },
 172         {
 173                 .errno = EHOSTUNREACH,  /* ICMP_PKT_FILTERED */
 174                 .fatal = 1,
 175         },
 176         {
 177                 .errno = EHOSTUNREACH,  /* ICMP_PREC_VIOLATION */
 178                 .fatal = 1,
 179         },
 180         {
 181                 .errno = EHOSTUNREACH,  /* ICMP_PREC_CUTOFF */
 182                 .fatal = 1,
 183         },
 184 };
 185 EXPORT_SYMBOL(icmp_err_convert);
 186
 187 /*
 188  *      ICMP control array. This specifies what to do with each ICMP.
 189  */
 190
 191 struct icmp_control {
 192         void (*handler)(struct sk_buff *skb);
 193         short   error;          /* This ICMP is classed as an error message */
 194 };
 195
 196 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES+1];
 197
 198 /*
 199  *      The ICMP socket(s). This is the most convenient way to flow control
 200  *      our ICMP output as well as maintain a clean interface throughout
 201  *      all layers. All Socketless IP sends will soon be gone.
 202  *
 203  *      On SMP we have one ICMP socket per-cpu.
 204  */
 205 static struct sock *icmp_sk(struct net *net)
 206 {
 207         return net->ipv4.icmp_sk[smp_processor_id()];
 208 }
 209
 210 static inline struct sock *icmp_xmit_lock(struct net *net)
 211 {
 212         struct sock *sk;
 213
 214         local_bh_disable();
 215
 216         sk = icmp_sk(net);
 217
 218         if (unlikely(!spin_trylock(&sk->sk_lock.slock))) {
 219                 /* This can happen if the output path signals a
 220                  * dst_link_failure() for an outgoing ICMP packet.
 221                  */
 222                 local_bh_enable();
 223                 return NULL;
 224         }
 225         return sk;
 226 }
 227
 228 static inline void icmp_xmit_unlock(struct sock *sk)
 229 {
 230         spin_unlock_bh(&sk->sk_lock.slock);
 231 }
 232
 233 /*
 234  *      Send an ICMP frame.
 235  */
 236
 237 static inline bool icmpv4_xrlim_allow(struct net *net, struct rtable *rt,
 238                                       struct flowi4 *fl4, int type, int code)
 239 {
 240         struct dst_entry *dst = &rt->dst;
 241         bool rc = true;
 242
 243         if (type > NR_ICMP_TYPES)
 244                 goto out;
 245
 246         /* Don't limit PMTU discovery. */
 247         if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 248                 goto out;
 249
 250         /* No rate limit on loopback */
 251         if (dst->dev && (dst->dev->flags&IFF_LOOPBACK))
 252                 goto out;
 253
 254         /* Limit if icmp type is enabled in ratemask. */
 255         if ((1 << type) & net->ipv4.sysctl_icmp_ratemask) {
 256                 if (!rt->peer)
 257                         rt_bind_peer(rt, fl4->daddr, 1);
 258                 rc = inet_peer_xrlim_allow(rt->peer,
 259                                            net->ipv4.sysctl_icmp_ratelimit);
 260         }
 261 out:
 262         return rc;
 263 }
 264
 265 /*
 266  *      Maintain the counters used in the SNMP statistics for outgoing ICMP
 267  */
 268 void icmp_out_count(struct net *net, unsigned char type)
 269 {
 270         ICMPMSGOUT_INC_STATS(net, type);
 271         ICMP_INC_STATS(net, ICMP_MIB_OUTMSGS);
 272 }
 273
 274 /*
 275  *      Checksum each fragment, and on the first include the headers and final
 276  *      checksum.
 277  */
 278 static int icmp_glue_bits(void *from, char *to, int offset, int len, int odd,
 279                           struct sk_buff *skb)
 280 {
 281         struct icmp_bxm *icmp_param = (struct icmp_bxm *)from;
 282         __wsum csum;
 283
 284         csum = skb_copy_and_csum_bits(icmp_param->skb,
 285                                       icmp_param->offset + offset,
 286                                       to, len, 0);
 287
 288         skb->csum = csum_block_add(skb->csum, csum, odd);
 289         if (icmp_pointers[icmp_param->data.icmph.type].error)
 290                 nf_ct_attach(skb, icmp_param->skb);
 291         return 0;
 292 }
 293
 294 static void icmp_push_reply(struct icmp_bxm *icmp_param,
 295                             struct flowi4 *fl4,
 296                             struct ipcm_cookie *ipc, struct rtable **rt)
 297 {
 298         struct sock *sk;
 299         struct sk_buff *skb;
 300
 301         sk = icmp_sk(dev_net((*rt)->dst.dev));
 302         if (ip_append_data(sk, fl4, icmp_glue_bits, icmp_param,
 303                            icmp_param->data_len+icmp_param->head_len,
 304                            icmp_param->head_len,
 305                            ipc, rt, MSG_DONTWAIT) < 0) {
 306                 ICMP_INC_STATS_BH(sock_net(sk), ICMP_MIB_OUTERRORS);
 307                 ip_flush_pending_frames(sk);
 308         } else if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {
 309                 struct icmphdr *icmph = icmp_hdr(skb);
 310                 __wsum csum = 0;
 311                 struct sk_buff *skb1;
 312
 313                 skb_queue_walk(&sk->sk_write_queue, skb1) {
 314                         csum = csum_add(csum, skb1->csum);
 315                 }
 316                 csum = csum_partial_copy_nocheck((void *)&icmp_param->data,
 317                                                  (char *)icmph,
 318                                                  icmp_param->head_len, csum);
 319                 icmph->checksum = csum_fold(csum);
 320                 skb->ip_summed = CHECKSUM_NONE;
 321                 ip_push_pending_frames(sk, fl4);
 322         }
 323 }
 324
 325 /*
 326  *      Driving logic for building and sending ICMP messages.
 327  */
 328
 329 static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
 330 {
 331         struct ipcm_cookie ipc;
 332         struct rtable *rt = skb_rtable(skb);
 333         struct net *net = dev_net(rt->dst.dev);
 334         struct flowi4 fl4;
 335         struct sock *sk;
 336         struct inet_sock *inet;
 337         __be32 daddr;
 338
 339         if (ip_options_echo(&icmp_param->replyopts.opt.opt, skb))
 340                 return;
 341
 342         sk = icmp_xmit_lock(net);
 343         if (sk == NULL)
 344                 return;
 345         inet = inet_sk(sk);
 346
 347         icmp_param->data.icmph.checksum = 0;
 348
 349         inet->tos = ip_hdr(skb)->tos;
 350         daddr = ipc.addr = ip_hdr(skb)->saddr;
 351         ipc.opt = NULL;
 352         ipc.tx_flags = 0;
 353         if (icmp_param->replyopts.opt.opt.optlen) {
 354                 ipc.opt = &icmp_param->replyopts.opt;
 355                 if (ipc.opt->opt.srr)
 356                         daddr = icmp_param->replyopts.opt.opt.faddr;
 357         }
 358         memset(&fl4, 0, sizeof(fl4));
 359         fl4.daddr = daddr;
 360         fl4.saddr = rt->rt_spec_dst;
 361         fl4.flowi4_tos = RT_TOS(ip_hdr(skb)->tos);
 362         fl4.flowi4_proto = IPPROTO_ICMP;
 363         security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
 364         rt = ip_route_output_key(net, &fl4);
 365         if (IS_ERR(rt))
 366                 goto out_unlock;
 367         if (icmpv4_xrlim_allow(net, rt, &fl4, icmp_param->data.icmph.type,
 368                                icmp_param->data.icmph.code))
 369                 icmp_push_reply(icmp_param, &fl4, &ipc, &rt);
 370         ip_rt_put(rt);
 371 out_unlock:
 372         icmp_xmit_unlock(sk);
 373 }
 374
 375 static struct rtable *icmp_route_lookup(struct net *net,
 376                                         struct flowi4 *fl4,
 377                                         struct sk_buff *skb_in,
 378                                         const struct iphdr *iph,
 379                                         __be32 saddr, u8 tos,
 380                                         int type, int code,
 381                                         struct icmp_bxm *param)
 382 {
 383         struct rtable *rt, *rt2;
 384         struct flowi4 fl4_dec;
 385         int err;
 386
 387         memset(fl4, 0, sizeof(*fl4));
 388         fl4->daddr = (param->replyopts.opt.opt.srr ?
 389                       param->replyopts.opt.opt.faddr : iph->saddr);
 390         fl4->saddr = saddr;
 391         fl4->flowi4_tos = RT_TOS(tos);
 392         fl4->flowi4_proto = IPPROTO_ICMP;
 393         fl4->fl4_icmp_type = type;
 394         fl4->fl4_icmp_code = code;
 395         security_skb_classify_flow(skb_in, flowi4_to_flowi(fl4));
 396         rt = __ip_route_output_key(net, fl4);
 397         if (IS_ERR(rt))
 398                 return rt;
 399
 400         /* No need to clone since we're just using its address. */
 401         rt2 = rt;
 402
 403         rt = (struct rtable *) xfrm_lookup(net, &rt->dst,
 404                                            flowi4_to_flowi(fl4), NULL, 0);
 405         if (!IS_ERR(rt)) {
 406                 if (rt != rt2)
 407                         return rt;
 408         } else if (PTR_ERR(rt) == -EPERM) {
 409                 rt = NULL;
 410         } else
 411                 return rt;
 412
 413         err = xfrm_decode_session_reverse(skb_in, flowi4_to_flowi(&fl4_dec), AF_INET);
 414         if (err)
 415                 goto relookup_failed;
 416
 417         if (inet_addr_type(net, fl4_dec.saddr) == RTN_LOCAL) {
 418                 rt2 = __ip_route_output_key(net, &fl4_dec);
 419                 if (IS_ERR(rt2))
 420                         err = PTR_ERR(rt2);
 421         } else {
 422                 struct flowi4 fl4_2 = {};
 423                 unsigned long orefdst;
 424
 425                 fl4_2.daddr = fl4_dec.saddr;
 426                 rt2 = ip_route_output_key(net, &fl4_2);
 427                 if (IS_ERR(rt2)) {
 428                         err = PTR_ERR(rt2);
 429                         goto relookup_failed;
 430                 }
 431                 /* Ugh! */
 432                 orefdst = skb_in->_skb_refdst; /* save old refdst */
 433                 err = ip_route_input(skb_in, fl4_dec.daddr, fl4_dec.saddr,
 434                                      RT_TOS(tos), rt2->dst.dev);
 435
 436                 dst_release(&rt2->dst);
 437                 rt2 = skb_rtable(skb_in);
 438                 skb_in->_skb_refdst = orefdst; /* restore old refdst */
 439         }
 440
 441         if (err)
 442                 goto relookup_failed;
 443
 444         rt2 = (struct rtable *) xfrm_lookup(net, &rt2->dst,
 445                                             flowi4_to_flowi(&fl4_dec), NULL,
 446                                             XFRM_LOOKUP_ICMP);
 447         if (!IS_ERR(rt2)) {
 448                 dst_release(&rt->dst);
 449                 memcpy(fl4, &fl4_dec, sizeof(*fl4));
 450                 rt = rt2;
 451         } else if (PTR_ERR(rt2) == -EPERM) {
 452                 if (rt)
 453                         dst_release(&rt->dst);
 454                 return rt2;
 455         } else {
 456                 err = PTR_ERR(rt2);
 457                 goto relookup_failed;
 458         }
 459         return rt;
 460
 461 relookup_failed:
 462         if (rt)
 463                 return rt;
 464         return ERR_PTR(err);
 465 }
 466
 467 /*
 468  *      Send an ICMP message in response to a situation
 469  *
 470  *      RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header.
 471  *                MAY send more (we do).
 472  *                      MUST NOT change this header information.
 473  *                      MUST NOT reply to a multicast/broadcast IP address.
 474  *                      MUST NOT reply to a multicast/broadcast MAC address.
 475  *                      MUST reply to only the first fragment.
 476  */
 477
 478 void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info)
 479 {
 480         struct iphdr *iph;
 481         int room;
 482         struct icmp_bxm icmp_param;
 483         struct rtable *rt = skb_rtable(skb_in);
 484         struct ipcm_cookie ipc;
 485         struct flowi4 fl4;
 486         __be32 saddr;
 487         u8  tos;
 488         struct net *net;
 489         struct sock *sk;
 490
 491         if (!rt)
 492                 goto out;
 493         net = dev_net(rt->dst.dev);
 494
 495         /*
 496          *      Find the original header. It is expected to be valid, of course.
 497          *      Check this, icmp_send is called from the most obscure devices
 498          *      sometimes.
 499          */
 500         iph = ip_hdr(skb_in);
 501
 502         if ((u8 *)iph < skb_in->head ||
 503             (skb_in->network_header + sizeof(*iph)) > skb_in->tail)
 504                 goto out;
 505
 506         /*
 507          *      No replies to physical multicast/broadcast
 508          */
 509         if (skb_in->pkt_type != PACKET_HOST)
 510                 goto out;
 511
 512         /*
 513          *      Now check at the protocol level
 514          */
 515         if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
 516                 goto out;
 517
 518         /*
 519          *      Only reply to fragment 0. We byte re-order the constant
 520          *      mask for efficiency.
 521          */
 522         if (iph->frag_off & htons(IP_OFFSET))
 523                 goto out;
 524
 525         /*
 526          *      If we send an ICMP error to an ICMP error a mess would result..
 527          */
 528         if (icmp_pointers[type].error) {
 529                 /*
 530                  *      We are an error, check if we are replying to an
 531                  *      ICMP error
 532                  */
 533                 if (iph->protocol == IPPROTO_ICMP) {
 534                         u8 _inner_type, *itp;
 535
 536                         itp = skb_header_pointer(skb_in,
 537                                                  skb_network_header(skb_in) +
 538                                                  (iph->ihl << 2) +
 539                                                  offsetof(struct icmphdr,
 540                                                           type) -
 541                                                  skb_in->data,
 542                                                  sizeof(_inner_type),
 543                                                  &_inner_type);
 544                         if (itp == NULL)
 545                                 goto out;
 546
 547                         /*
 548                          *      Assume any unknown ICMP type is an error. This
 549                          *      isn't specified by the RFC, but think about it..
 550                          */
 551                         if (*itp > NR_ICMP_TYPES ||
 552                             icmp_pointers[*itp].error)
 553                                 goto out;
 554                 }
 555         }
 556
 557         sk = icmp_xmit_lock(net);
 558         if (sk == NULL)
 559                 return;
 560
 561         /*
 562          *      Construct source address and options.
 563          */
 564
 565         saddr = iph->daddr;
 566         if (!(rt->rt_flags & RTCF_LOCAL)) {
 567                 struct net_device *dev = NULL;
 568
 569                 rcu_read_lock();
 570                 if (rt_is_input_route(rt) &&
 571                     net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr)
 572                         dev = dev_get_by_index_rcu(net, rt->rt_iif);
 573
 574                 if (dev)
 575                         saddr = inet_select_addr(dev, 0, RT_SCOPE_LINK);
 576                 else
 577                         saddr = 0;
 578                 rcu_read_unlock();
 579         }
 580
 581         tos = icmp_pointers[type].error ? ((iph->tos & IPTOS_TOS_MASK) |
 582                                            IPTOS_PREC_INTERNETCONTROL) :
 583                                           iph->tos;
 584
 585         if (ip_options_echo(&icmp_param.replyopts.opt.opt, skb_in))
 586                 goto out_unlock;
 587
 588
 589         /*
 590          *      Prepare data for ICMP header.
 591          */
 592
 593         icmp_param.data.icmph.type       = type;
 594         icmp_param.data.icmph.code       = code;
 595         icmp_param.data.icmph.un.gateway = info;
 596         icmp_param.data.icmph.checksum   = 0;
 597         icmp_param.skb    = skb_in;
 598         icmp_param.offset = skb_network_offset(skb_in);
 599         inet_sk(sk)->tos = tos;
 600         ipc.addr = iph->saddr;
 601         ipc.opt = &icmp_param.replyopts.opt;
 602         ipc.tx_flags = 0;
 603
 604         rt = icmp_route_lookup(net, &fl4, skb_in, iph, saddr, tos,
 605                                type, code, &icmp_param);
 606         if (IS_ERR(rt))
 607                 goto out_unlock;
 608
 609         if (!icmpv4_xrlim_allow(net, rt, &fl4, type, code))
 610                 goto ende;
 611
 612         /* RFC says return as much as we can without exceeding 576 bytes. */
 613
 614         room = dst_mtu(&rt->dst);
 615         if (room > 576)
 616                 room = 576;
 617         room -= sizeof(struct iphdr) + icmp_param.replyopts.opt.opt.optlen;
 618         room -= sizeof(struct icmphdr);
 619
 620         icmp_param.data_len = skb_in->len - icmp_param.offset;
 621         if (icmp_param.data_len > room)
 622                 icmp_param.data_len = room;
 623         icmp_param.head_len = sizeof(struct icmphdr);
 624
 625         icmp_push_reply(&icmp_param, &fl4, &ipc, &rt);
 626 ende:
 627         ip_rt_put(rt);
 628 out_unlock:
 629         icmp_xmit_unlock(sk);
 630 out:;
 631 }
 632 EXPORT_SYMBOL(icmp_send);
 633
 634
 635 /*
 636  *      Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEED, and ICMP_QUENCH.
 637  */
 638
 639 static void icmp_unreach(struct sk_buff *skb)
 640 {
 641         const struct iphdr *iph;
 642         struct icmphdr *icmph;
 643         int hash, protocol;
 644         const struct net_protocol *ipprot;
 645         u32 info = 0;
 646         struct net *net;
 647
 648         net = dev_net(skb_dst(skb)->dev);
 649
 650         /*
 651          *      Incomplete header ?
 652          *      Only checks for the IP header, there should be an
 653          *      additional check for longer headers in upper levels.
 654          */
 655
 656         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
 657                 goto out_err;
 658
 659         icmph = icmp_hdr(skb);
 660         iph   = (const struct iphdr *)skb->data;
 661
 662         if (iph->ihl < 5) /* Mangled header, drop. */
 663                 goto out_err;
 664
 665         if (icmph->type == ICMP_DEST_UNREACH) {
 666                 switch (icmph->code & 15) {
 667                 case ICMP_NET_UNREACH:
 668                 case ICMP_HOST_UNREACH:
 669                 case ICMP_PROT_UNREACH:
 670                 case ICMP_PORT_UNREACH:
 671                         break;
 672                 case ICMP_FRAG_NEEDED:
 673                         if (ipv4_config.no_pmtu_disc) {
 674                                 LIMIT_NETDEBUG(KERN_INFO pr_fmt("%pI4: fragmentation needed and DF set\n"),
 675                                                &iph->daddr);
 676                         } else {
 677                                 info = ip_rt_frag_needed(net, iph,
 678                                                          ntohs(icmph->un.frag.mtu),
 679                                                          skb->dev);
 680                                 if (!info)
 681                                         goto out;
 682                         }
 683                         break;
 684                 case ICMP_SR_FAILED:
 685                         LIMIT_NETDEBUG(KERN_INFO pr_fmt("%pI4: Source Route Failed\n"),
 686                                        &iph->daddr);
 687                         break;
 688                 default:
 689                         break;
 690                 }
 691                 if (icmph->code > NR_ICMP_UNREACH)
 692                         goto out;
 693         } else if (icmph->type == ICMP_PARAMETERPROB)
 694                 info = ntohl(icmph->un.gateway) >> 24;
 695
 696         /*
 697          *      Throw it at our lower layers
 698          *
 699          *      RFC 1122: 3.2.2 MUST extract the protocol ID from the passed
 700          *                header.
 701          *      RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the
 702          *                transport layer.
 703          *      RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to
 704          *                transport layer.
 705          */
 706
 707         /*
 708          *      Check the other end isn't violating RFC 1122. Some routers send
 709          *      bogus responses to broadcast frames. If you see this message
 710          *      first check your netmask matches at both ends, if it does then
 711          *      get the other vendor to fix their kit.
 712          */
 713
 714         if (!net->ipv4.sysctl_icmp_ignore_bogus_error_responses &&
 715             inet_addr_type(net, iph->daddr) == RTN_BROADCAST) {
 716                 if (net_ratelimit())
 717                         pr_warn("%pI4 sent an invalid ICMP type %u, code %u error to a broadcast: %pI4 on %s\n",
 718                                 &ip_hdr(skb)->saddr,
 719                                 icmph->type, icmph->code,
 720                                 &iph->daddr, skb->dev->name);
 721                 goto out;
 722         }
 723
 724         /* Checkin full IP header plus 8 bytes of protocol to
 725          * avoid additional coding at protocol handlers.
 726          */
 727         if (!pskb_may_pull(skb, iph->ihl * 4 + 8))
 728                 goto out;
 729
 730         iph = (const struct iphdr *)skb->data;
 731         protocol = iph->protocol;
 732
 733         /*
 734          *      Deliver ICMP message to raw sockets. Pretty useless feature?
 735          */
 736         raw_icmp_error(skb, protocol, info);
 737
 738         hash = protocol & (MAX_INET_PROTOS - 1);
 739         rcu_read_lock();
 740         ipprot = rcu_dereference(inet_protos[hash]);
 741         if (ipprot && ipprot->err_handler)
 742                 ipprot->err_handler(skb, info);
 743         rcu_read_unlock();
 744
 745 out:
 746         return;
 747 out_err:
 748         ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS);
 749         goto out;
 750 }
 751
 752
 753 /*
 754  *      Handle ICMP_REDIRECT.
 755  */
 756
 757 static void icmp_redirect(struct sk_buff *skb)
 758 {
 759         const struct iphdr *iph;
 760
 761         if (skb->len < sizeof(struct iphdr))
 762                 goto out_err;
 763
 764         /*
 765          *      Get the copied header of the packet that caused the redirect
 766          */
 767         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
 768                 goto out;
 769
 770         iph = (const struct iphdr *)skb->data;
 771
 772         switch (icmp_hdr(skb)->code & 7) {
 773         case ICMP_REDIR_NET:
 774         case ICMP_REDIR_NETTOS:
 775                 /*
 776                  * As per RFC recommendations now handle it as a host redirect.
 777                  */
 778         case ICMP_REDIR_HOST:
 779         case ICMP_REDIR_HOSTTOS:
 780                 ip_rt_redirect(ip_hdr(skb)->saddr, iph->daddr,
 781                                icmp_hdr(skb)->un.gateway,
 782                                iph->saddr, skb->dev);
 783                 break;
 784         }
 785
 786         /* Ping wants to see redirects.
 787          * Let's pretend they are errors of sorts... */
 788         if (iph->protocol == IPPROTO_ICMP &&
 789             iph->ihl >= 5 &&
 790             pskb_may_pull(skb, (iph->ihl<<2)+8)) {
 791                 ping_err(skb, icmp_hdr(skb)->un.gateway);
 792         }
 793
 794 out:
 795         return;
 796 out_err:
 797         ICMP_INC_STATS_BH(dev_net(skb->dev), ICMP_MIB_INERRORS);
 798         goto out;
 799 }
 800
 801 /*
 802  *      Handle ICMP_ECHO ("ping") requests.
 803  *
 804  *      RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo
 805  *                requests.
 806  *      RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be
 807  *                included in the reply.
 808  *      RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring
 809  *                echo requests, MUST have default=NOT.
 810  *      See also WRT handling of options once they are done and working.
 811  */
 812
 813 static void icmp_echo(struct sk_buff *skb)
 814 {
 815         struct net *net;
 816
 817         net = dev_net(skb_dst(skb)->dev);
 818         if (!net->ipv4.sysctl_icmp_echo_ignore_all) {
 819                 struct icmp_bxm icmp_param;
 820
 821                 icmp_param.data.icmph      = *icmp_hdr(skb);
 822                 icmp_param.data.icmph.type = ICMP_ECHOREPLY;
 823                 icmp_param.skb             = skb;
 824                 icmp_param.offset          = 0;
 825                 icmp_param.data_len        = skb->len;
 826                 icmp_param.head_len        = sizeof(struct icmphdr);
 827                 icmp_reply(&icmp_param, skb);
 828         }
 829 }
 830
 831 /*
 832  *      Handle ICMP Timestamp requests.
 833  *      RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests.
 834  *                SHOULD be in the kernel for minimum random latency.
 835  *                MUST be accurate to a few minutes.
 836  *                MUST be updated at least at 15Hz.
 837  */
 838 static void icmp_timestamp(struct sk_buff *skb)
 839 {
 840         struct timespec tv;
 841         struct icmp_bxm icmp_param;
 842         /*
 843          *      Too short.
 844          */
 845         if (skb->len < 4)
 846                 goto out_err;
 847
 848         /*
 849          *      Fill in the current time as ms since midnight UT:
 850          */
 851         getnstimeofday(&tv);
 852         icmp_param.data.times[1] = htonl((tv.tv_sec % 86400) * MSEC_PER_SEC +
 853                                          tv.tv_nsec / NSEC_PER_MSEC);
 854         icmp_param.data.times[2] = icmp_param.data.times[1];
 855         if (skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4))
 856                 BUG();
 857         icmp_param.data.icmph      = *icmp_hdr(skb);
 858         icmp_param.data.icmph.type = ICMP_TIMESTAMPREPLY;
 859         icmp_param.data.icmph.code = 0;
 860         icmp_param.skb             = skb;
 861         icmp_param.offset          = 0;
 862         icmp_param.data_len        = 0;
 863         icmp_param.head_len        = sizeof(struct icmphdr) + 12;
 864         icmp_reply(&icmp_param, skb);
 865 out:
 866         return;
 867 out_err:
 868         ICMP_INC_STATS_BH(dev_net(skb_dst(skb)->dev), ICMP_MIB_INERRORS);
 869         goto out;
 870 }
 871
 872
 873 /*
 874  *      Handle ICMP_ADDRESS_MASK requests.  (RFC950)
 875  *
 876  * RFC1122 (3.2.2.9).  A host MUST only send replies to
 877  * ADDRESS_MASK requests if it's been configured as an address mask
 878  * agent.  Receiving a request doesn't constitute implicit permission to
 879  * act as one. Of course, implementing this correctly requires (SHOULD)
 880  * a way to turn the functionality on and off.  Another one for sysctl(),
 881  * I guess. -- MS
 882  *
 883  * RFC1812 (4.3.3.9).   A router MUST implement it.
 884  *                      A router SHOULD have switch turning it on/off.
 885  *                      This switch MUST be ON by default.
 886  *
 887  * Gratuitous replies, zero-source replies are not implemented,
 888  * that complies with RFC. DO NOT implement them!!! All the idea
 889  * of broadcast addrmask replies as specified in RFC950 is broken.
 890  * The problem is that it is not uncommon to have several prefixes
 891  * on one physical interface. Moreover, addrmask agent can even be
 892  * not aware of existing another prefixes.
 893  * If source is zero, addrmask agent cannot choose correct prefix.
 894  * Gratuitous mask announcements suffer from the same problem.
 895  * RFC1812 explains it, but still allows to use ADDRMASK,
 896  * that is pretty silly. --ANK
 897  *
 898  * All these rules are so bizarre, that I removed kernel addrmask
 899  * support at all. It is wrong, it is obsolete, nobody uses it in
 900  * any case. --ANK
 901  *
 902  * Furthermore you can do it with a usermode address agent program
 903  * anyway...
 904  */
 905
 906 static void icmp_address(struct sk_buff *skb)
 907 {
 908 #if 0
 909         if (net_ratelimit())
 910                 printk(KERN_DEBUG "a guy asks for address mask. Who is it?\n");
 911 #endif
 912 }
 913
 914 /*
 915  * RFC1812 (4.3.3.9).   A router SHOULD listen all replies, and complain
 916  *                      loudly if an inconsistency is found.
 917  * called with rcu_read_lock()
 918  */
 919
 920 static void icmp_address_reply(struct sk_buff *skb)
 921 {
 922         struct rtable *rt = skb_rtable(skb);
 923         struct net_device *dev = skb->dev;
 924         struct in_device *in_dev;
 925         struct in_ifaddr *ifa;
 926
 927         if (skb->len < 4 || !(rt->rt_flags&RTCF_DIRECTSRC))
 928                 return;
 929
 930         in_dev = __in_dev_get_rcu(dev);
 931         if (!in_dev)
 932                 return;
 933
 934         if (in_dev->ifa_list &&
 935             IN_DEV_LOG_MARTIANS(in_dev) &&
 936             IN_DEV_FORWARD(in_dev)) {
 937                 __be32 _mask, *mp;
 938
 939                 mp = skb_header_pointer(skb, 0, sizeof(_mask), &_mask);
 940                 BUG_ON(mp == NULL);
 941                 for (ifa = in_dev->ifa_list; ifa; ifa = ifa->ifa_next) {
 942                         if (*mp == ifa->ifa_mask &&
 943                             inet_ifa_match(ip_hdr(skb)->saddr, ifa))
 944                                 break;
 945                 }
 946                 if (!ifa && net_ratelimit()) {
 947                         pr_info("Wrong address mask %pI4 from %s/%pI4\n",
 948                                 mp, dev->name, &ip_hdr(skb)->saddr);
 949                 }
 950         }
 951 }
 952
 953 static void icmp_discard(struct sk_buff *skb)
 954 {
 955 }
 956
 957 /*
 958  *      Deal with incoming ICMP packets.
 959  */
 960 int icmp_rcv(struct sk_buff *skb)
 961 {
 962         struct icmphdr *icmph;
 963         struct rtable *rt = skb_rtable(skb);
 964         struct net *net = dev_net(rt->dst.dev);
 965
 966         if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
 967                 struct sec_path *sp = skb_sec_path(skb);
 968                 int nh;
 969
 970                 if (!(sp && sp->xvec[sp->len - 1]->props.flags &
 971                                  XFRM_STATE_ICMP))
 972                         goto drop;
 973
 974                 if (!pskb_may_pull(skb, sizeof(*icmph) + sizeof(struct iphdr)))
 975                         goto drop;
 976
 977                 nh = skb_network_offset(skb);
 978                 skb_set_network_header(skb, sizeof(*icmph));
 979
 980                 if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN, skb))
 981                         goto drop;
 982
 983                 skb_set_network_header(skb, nh);
 984         }
 985
 986         ICMP_INC_STATS_BH(net, ICMP_MIB_INMSGS);
 987
 988         switch (skb->ip_summed) {
 989         case CHECKSUM_COMPLETE:
 990                 if (!csum_fold(skb->csum))
 991                         break;
 992                 /* fall through */
 993         case CHECKSUM_NONE:
 994                 skb->csum = 0;
 995                 if (__skb_checksum_complete(skb))
 996                         goto error;
 997         }
 998
 999         if (!pskb_pull(skb, sizeof(*icmph)))
1000                 goto error;
1001
1002         icmph = icmp_hdr(skb);
1003
1004         ICMPMSGIN_INC_STATS_BH(net, icmph->type);
1005         /*
1006          *      18 is the highest 'known' ICMP type. Anything else is a mystery
1007          *
1008          *      RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
1009          *                discarded.
1010          */
1011         if (icmph->type > NR_ICMP_TYPES)
1012                 goto error;
1013
1014
1015         /*
1016          *      Parse the ICMP message
1017          */
1018
1019         if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) {
1020                 /*
1021                  *      RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be
1022                  *        silently ignored (we let user decide with a sysctl).
1023                  *      RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently
1024                  *        discarded if to broadcast/multicast.
1025                  */
1026                 if ((icmph->type == ICMP_ECHO ||
1027                      icmph->type == ICMP_TIMESTAMP) &&
1028                     net->ipv4.sysctl_icmp_echo_ignore_broadcasts) {
1029                         goto error;
1030                 }
1031                 if (icmph->type != ICMP_ECHO &&
1032                     icmph->type != ICMP_TIMESTAMP &&
1033                     icmph->type != ICMP_ADDRESS &&
1034                     icmph->type != ICMP_ADDRESSREPLY) {
1035                         goto error;
1036                 }
1037         }
1038
1039         icmp_pointers[icmph->type].handler(skb);
1040
1041 drop:
1042         kfree_skb(skb);
1043         return 0;
1044 error:
1045         ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS);
1046         goto drop;
1047 }
1048
1049 /*
1050  *      This table is the definition of how we handle ICMP.
1051  */
1052 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = {
1053         [ICMP_ECHOREPLY] = {
1054                 .handler = ping_rcv,
1055         },
1056         [1] = {
1057                 .handler = icmp_discard,
1058                 .error = 1,
1059         },
1060         [2] = {
1061                 .handler = icmp_discard,
1062                 .error = 1,
1063         },
1064         [ICMP_DEST_UNREACH] = {
1065                 .handler = icmp_unreach,
1066                 .error = 1,
1067         },
1068         [ICMP_SOURCE_QUENCH] = {
1069                 .handler = icmp_unreach,
1070                 .error = 1,
1071         },
1072         [ICMP_REDIRECT] = {
1073                 .handler = icmp_redirect,
1074                 .error = 1,
1075         },
1076         [6] = {
1077                 .handler = icmp_discard,
1078                 .error = 1,
1079         },
1080         [7] = {
1081                 .handler = icmp_discard,
1082                 .error = 1,
1083         },
1084         [ICMP_ECHO] = {
1085                 .handler = icmp_echo,
1086         },
1087         [9] = {
1088                 .handler = icmp_discard,
1089                 .error = 1,
1090         },
1091         [10] = {
1092                 .handler = icmp_discard,
1093                 .error = 1,
1094         },
1095         [ICMP_TIME_EXCEEDED] = {
1096                 .handler = icmp_unreach,
1097                 .error = 1,
1098         },
1099         [ICMP_PARAMETERPROB] = {
1100                 .handler = icmp_unreach,
1101                 .error = 1,
1102         },
1103         [ICMP_TIMESTAMP] = {
1104                 .handler = icmp_timestamp,
1105         },
1106         [ICMP_TIMESTAMPREPLY] = {
1107                 .handler = icmp_discard,
1108         },
1109         [ICMP_INFO_REQUEST] = {
1110                 .handler = icmp_discard,
1111         },
1112         [ICMP_INFO_REPLY] = {
1113                 .handler = icmp_discard,
1114         },
1115         [ICMP_ADDRESS] = {
1116                 .handler = icmp_address,
1117         },
1118         [ICMP_ADDRESSREPLY] = {
1119                 .handler = icmp_address_reply,
1120         },
1121 };
1122
1123 static void __net_exit icmp_sk_exit(struct net *net)
1124 {
1125         int i;
1126
1127         for_each_possible_cpu(i)
1128                 inet_ctl_sock_destroy(net->ipv4.icmp_sk[i]);
1129         kfree(net->ipv4.icmp_sk);
1130         net->ipv4.icmp_sk = NULL;
1131 }
1132
1133 static int __net_init icmp_sk_init(struct net *net)
1134 {
1135         int i, err;
1136
1137         net->ipv4.icmp_sk =
1138                 kzalloc(nr_cpu_ids * sizeof(struct sock *), GFP_KERNEL);
1139         if (net->ipv4.icmp_sk == NULL)
1140                 return -ENOMEM;
1141
1142         for_each_possible_cpu(i) {
1143                 struct sock *sk;
1144
1145                 err = inet_ctl_sock_create(&sk, PF_INET,
1146                                            SOCK_RAW, IPPROTO_ICMP, net);
1147                 if (err < 0)
1148                         goto fail;
1149
1150                 net->ipv4.icmp_sk[i] = sk;
1151
1152                 /* Enough space for 2 64K ICMP packets, including
1153                  * sk_buff/skb_shared_info struct overhead.
1154                  */
1155                 sk->sk_sndbuf = 2 * SKB_TRUESIZE(64 * 1024);
1156
1157                 /*
1158                  * Speedup sock_wfree()
1159                  */
1160                 sock_set_flag(sk, SOCK_USE_WRITE_QUEUE);
1161                 inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT;
1162         }
1163
1164         /* Control parameters for ECHO replies. */
1165         net->ipv4.sysctl_icmp_echo_ignore_all = 0;
1166         net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1;
1167
1168         /* Control parameter - ignore bogus broadcast responses? */
1169         net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1;
1170
1171         /*
1172          *      Configurable global rate limit.
1173          *
1174          *      ratelimit defines tokens/packet consumed for dst->rate_token
1175          *      bucket ratemask defines which icmp types are ratelimited by
1176          *      setting it's bit position.
1177          *
1178          *      default:
1179          *      dest unreachable (3), source quench (4),
1180          *      time exceeded (11), parameter problem (12)
1181          */
1182
1183         net->ipv4.sysctl_icmp_ratelimit = 1 * HZ;
1184         net->ipv4.sysctl_icmp_ratemask = 0x1818;
1185         net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0;
1186
1187         return 0;
1188
1189 fail:
1190         for_each_possible_cpu(i)
1191                 inet_ctl_sock_destroy(net->ipv4.icmp_sk[i]);
1192         kfree(net->ipv4.icmp_sk);
1193         return err;
1194 }
1195
1196 static struct pernet_operations __net_initdata icmp_sk_ops = {
1197        .init = icmp_sk_init,
1198        .exit = icmp_sk_exit,
1199 };
1200
1201 int __init icmp_init(void)
1202 {
1203         return register_pernet_subsys(&icmp_sk_ops);
1204 }