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 #include <net/ip_fib.h>
  99
 100 /*
 101  *      Build xmit assembly blocks
 102  */
 103
 104 struct icmp_bxm {
 105         struct sk_buff *skb;
 106         int offset;
 107         int data_len;
 108
 109         struct {
 110                 struct icmphdr icmph;
 111                 __be32         times[3];
 112         } data;
 113         int head_len;
 114         struct ip_options_data replyopts;
 115 };
 116
 117 /* An array of errno for error messages from dest unreach. */
 118 /* RFC 1122: 3.2.2.1 States that NET_UNREACH, HOST_UNREACH and SR_FAILED MUST be considered 'transient errs'. */
 119
 120 const struct icmp_err icmp_err_convert[] = {
 121         {
 122                 .errno = ENETUNREACH,   /* ICMP_NET_UNREACH */
 123                 .fatal = 0,
 124         },
 125         {
 126                 .errno = EHOSTUNREACH,  /* ICMP_HOST_UNREACH */
 127                 .fatal = 0,
 128         },
 129         {
 130                 .errno = ENOPROTOOPT    /* ICMP_PROT_UNREACH */,
 131                 .fatal = 1,
 132         },
 133         {
 134                 .errno = ECONNREFUSED,  /* ICMP_PORT_UNREACH */
 135                 .fatal = 1,
 136         },
 137         {
 138                 .errno = EMSGSIZE,      /* ICMP_FRAG_NEEDED */
 139                 .fatal = 0,
 140         },
 141         {
 142                 .errno = EOPNOTSUPP,    /* ICMP_SR_FAILED */
 143                 .fatal = 0,
 144         },
 145         {
 146                 .errno = ENETUNREACH,   /* ICMP_NET_UNKNOWN */
 147                 .fatal = 1,
 148         },
 149         {
 150                 .errno = EHOSTDOWN,     /* ICMP_HOST_UNKNOWN */
 151                 .fatal = 1,
 152         },
 153         {
 154                 .errno = ENONET,        /* ICMP_HOST_ISOLATED */
 155                 .fatal = 1,
 156         },
 157         {
 158                 .errno = ENETUNREACH,   /* ICMP_NET_ANO */
 159                 .fatal = 1,
 160         },
 161         {
 162                 .errno = EHOSTUNREACH,  /* ICMP_HOST_ANO */
 163                 .fatal = 1,
 164         },
 165         {
 166                 .errno = ENETUNREACH,   /* ICMP_NET_UNR_TOS */
 167                 .fatal = 0,
 168         },
 169         {
 170                 .errno = EHOSTUNREACH,  /* ICMP_HOST_UNR_TOS */
 171                 .fatal = 0,
 172         },
 173         {
 174                 .errno = EHOSTUNREACH,  /* ICMP_PKT_FILTERED */
 175                 .fatal = 1,
 176         },
 177         {
 178                 .errno = EHOSTUNREACH,  /* ICMP_PREC_VIOLATION */
 179                 .fatal = 1,
 180         },
 181         {
 182                 .errno = EHOSTUNREACH,  /* ICMP_PREC_CUTOFF */
 183                 .fatal = 1,
 184         },
 185 };
 186 EXPORT_SYMBOL(icmp_err_convert);
 187
 188 /*
 189  *      ICMP control array. This specifies what to do with each ICMP.
 190  */
 191
 192 struct icmp_control {
 193         void (*handler)(struct sk_buff *skb);
 194         short   error;          /* This ICMP is classed as an error message */
 195 };
 196
 197 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES+1];
 198
 199 /*
 200  *      The ICMP socket(s). This is the most convenient way to flow control
 201  *      our ICMP output as well as maintain a clean interface throughout
 202  *      all layers. All Socketless IP sends will soon be gone.
 203  *
 204  *      On SMP we have one ICMP socket per-cpu.
 205  */
 206 static struct sock *icmp_sk(struct net *net)
 207 {
 208         return net->ipv4.icmp_sk[smp_processor_id()];
 209 }
 210
 211 static inline struct sock *icmp_xmit_lock(struct net *net)
 212 {
 213         struct sock *sk;
 214
 215         local_bh_disable();
 216
 217         sk = icmp_sk(net);
 218
 219         if (unlikely(!spin_trylock(&sk->sk_lock.slock))) {
 220                 /* This can happen if the output path signals a
 221                  * dst_link_failure() for an outgoing ICMP packet.
 222                  */
 223                 local_bh_enable();
 224                 return NULL;
 225         }
 226         return sk;
 227 }
 228
 229 static inline void icmp_xmit_unlock(struct sock *sk)
 230 {
 231         spin_unlock_bh(&sk->sk_lock.slock);
 232 }
 233
 234 /*
 235  *      Send an ICMP frame.
 236  */
 237
 238 static inline bool icmpv4_xrlim_allow(struct net *net, struct rtable *rt,
 239                                       struct flowi4 *fl4, int type, int code)
 240 {
 241         struct dst_entry *dst = &rt->dst;
 242         bool rc = true;
 243
 244         if (type > NR_ICMP_TYPES)
 245                 goto out;
 246
 247         /* Don't limit PMTU discovery. */
 248         if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 249                 goto out;
 250
 251         /* No rate limit on loopback */
 252         if (dst->dev && (dst->dev->flags&IFF_LOOPBACK))
 253                 goto out;
 254
 255         /* Limit if icmp type is enabled in ratemask. */
 256         if ((1 << type) & net->ipv4.sysctl_icmp_ratemask) {
 257                 struct inet_peer *peer = inet_getpeer_v4(net->ipv4.peers, fl4->daddr, 1);
 258                 rc = inet_peer_xrlim_allow(peer,
 259                                            net->ipv4.sysctl_icmp_ratelimit);
 260                 if (peer)
 261                         inet_putpeer(peer);
 262         }
 263 out:
 264         return rc;
 265 }
 266
 267 /*
 268  *      Maintain the counters used in the SNMP statistics for outgoing ICMP
 269  */
 270 void icmp_out_count(struct net *net, unsigned char type)
 271 {
 272         ICMPMSGOUT_INC_STATS(net, type);
 273         ICMP_INC_STATS(net, ICMP_MIB_OUTMSGS);
 274 }
 275
 276 /*
 277  *      Checksum each fragment, and on the first include the headers and final
 278  *      checksum.
 279  */
 280 static int icmp_glue_bits(void *from, char *to, int offset, int len, int odd,
 281                           struct sk_buff *skb)
 282 {
 283         struct icmp_bxm *icmp_param = (struct icmp_bxm *)from;
 284         __wsum csum;
 285
 286         csum = skb_copy_and_csum_bits(icmp_param->skb,
 287                                       icmp_param->offset + offset,
 288                                       to, len, 0);
 289
 290         skb->csum = csum_block_add(skb->csum, csum, odd);
 291         if (icmp_pointers[icmp_param->data.icmph.type].error)
 292                 nf_ct_attach(skb, icmp_param->skb);
 293         return 0;
 294 }
 295
 296 static void icmp_push_reply(struct icmp_bxm *icmp_param,
 297                             struct flowi4 *fl4,
 298                             struct ipcm_cookie *ipc, struct rtable **rt)
 299 {
 300         struct sock *sk;
 301         struct sk_buff *skb;
 302
 303         sk = icmp_sk(dev_net((*rt)->dst.dev));
 304         if (ip_append_data(sk, fl4, icmp_glue_bits, icmp_param,
 305                            icmp_param->data_len+icmp_param->head_len,
 306                            icmp_param->head_len,
 307                            ipc, rt, MSG_DONTWAIT) < 0) {
 308                 ICMP_INC_STATS_BH(sock_net(sk), ICMP_MIB_OUTERRORS);
 309                 ip_flush_pending_frames(sk);
 310         } else if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {
 311                 struct icmphdr *icmph = icmp_hdr(skb);
 312                 __wsum csum = 0;
 313                 struct sk_buff *skb1;
 314
 315                 skb_queue_walk(&sk->sk_write_queue, skb1) {
 316                         csum = csum_add(csum, skb1->csum);
 317                 }
 318                 csum = csum_partial_copy_nocheck((void *)&icmp_param->data,
 319                                                  (char *)icmph,
 320                                                  icmp_param->head_len, csum);
 321                 icmph->checksum = csum_fold(csum);
 322                 skb->ip_summed = CHECKSUM_NONE;
 323                 ip_push_pending_frames(sk, fl4);
 324         }
 325 }
 326
 327 /*
 328  *      Driving logic for building and sending ICMP messages.
 329  */
 330
 331 static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
 332 {
 333         struct ipcm_cookie ipc;
 334         struct rtable *rt = skb_rtable(skb);
 335         struct net *net = dev_net(rt->dst.dev);
 336         struct flowi4 fl4;
 337         struct sock *sk;
 338         struct inet_sock *inet;
 339         __be32 daddr, saddr;
 340         u32 mark = IP4_REPLY_MARK(net, skb->mark);
 341
 342         if (ip_options_echo(&icmp_param->replyopts.opt.opt, skb))
 343                 return;
 344
 345         sk = icmp_xmit_lock(net);
 346         if (sk == NULL)
 347                 return;
 348         inet = inet_sk(sk);
 349
 350         icmp_param->data.icmph.checksum = 0;
 351
 352         inet->tos = ip_hdr(skb)->tos;
 353         sk->sk_mark = mark;
 354         daddr = ipc.addr = ip_hdr(skb)->saddr;
 355         saddr = fib_compute_spec_dst(skb);
 356         ipc.opt = NULL;
 357         ipc.tx_flags = 0;
 358         ipc.ttl = 0;
 359         ipc.tos = -1;
 360
 361         if (icmp_param->replyopts.opt.opt.optlen) {
 362                 ipc.opt = &icmp_param->replyopts.opt;
 363                 if (ipc.opt->opt.srr)
 364                         daddr = icmp_param->replyopts.opt.opt.faddr;
 365         }
 366         memset(&fl4, 0, sizeof(fl4));
 367         fl4.daddr = daddr;
 368         fl4.saddr = saddr;
 369         fl4.flowi4_mark = mark;
 370         fl4.flowi4_tos = RT_TOS(ip_hdr(skb)->tos);
 371         fl4.flowi4_proto = IPPROTO_ICMP;
 372         security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
 373         rt = ip_route_output_key(net, &fl4);
 374         if (IS_ERR(rt))
 375                 goto out_unlock;
 376         if (icmpv4_xrlim_allow(net, rt, &fl4, icmp_param->data.icmph.type,
 377                                icmp_param->data.icmph.code))
 378                 icmp_push_reply(icmp_param, &fl4, &ipc, &rt);
 379         ip_rt_put(rt);
 380 out_unlock:
 381         icmp_xmit_unlock(sk);
 382 }
 383
 384 static struct rtable *icmp_route_lookup(struct net *net,
 385                                         struct flowi4 *fl4,
 386                                         struct sk_buff *skb_in,
 387                                         const struct iphdr *iph,
 388                                         __be32 saddr, u8 tos, u32 mark,
 389                                         int type, int code,
 390                                         struct icmp_bxm *param)
 391 {
 392         struct rtable *rt, *rt2;
 393         struct flowi4 fl4_dec;
 394         int err;
 395
 396         memset(fl4, 0, sizeof(*fl4));
 397         fl4->daddr = (param->replyopts.opt.opt.srr ?
 398                       param->replyopts.opt.opt.faddr : iph->saddr);
 399         fl4->saddr = saddr;
 400         fl4->flowi4_mark = mark;
 401         fl4->flowi4_tos = RT_TOS(tos);
 402         fl4->flowi4_proto = IPPROTO_ICMP;
 403         fl4->fl4_icmp_type = type;
 404         fl4->fl4_icmp_code = code;
 405         security_skb_classify_flow(skb_in, flowi4_to_flowi(fl4));
 406         rt = __ip_route_output_key(net, fl4);
 407         if (IS_ERR(rt))
 408                 return rt;
 409
 410         /* No need to clone since we're just using its address. */
 411         rt2 = rt;
 412
 413         rt = (struct rtable *) xfrm_lookup(net, &rt->dst,
 414                                            flowi4_to_flowi(fl4), NULL, 0);
 415         if (!IS_ERR(rt)) {
 416                 if (rt != rt2)
 417                         return rt;
 418         } else if (PTR_ERR(rt) == -EPERM) {
 419                 rt = NULL;
 420         } else
 421                 return rt;
 422
 423         err = xfrm_decode_session_reverse(skb_in, flowi4_to_flowi(&fl4_dec), AF_INET);
 424         if (err)
 425                 goto relookup_failed;
 426
 427         if (inet_addr_type(net, fl4_dec.saddr) == RTN_LOCAL) {
 428                 rt2 = __ip_route_output_key(net, &fl4_dec);
 429                 if (IS_ERR(rt2))
 430                         err = PTR_ERR(rt2);
 431         } else {
 432                 struct flowi4 fl4_2 = {};
 433                 unsigned long orefdst;
 434
 435                 fl4_2.daddr = fl4_dec.saddr;
 436                 rt2 = ip_route_output_key(net, &fl4_2);
 437                 if (IS_ERR(rt2)) {
 438                         err = PTR_ERR(rt2);
 439                         goto relookup_failed;
 440                 }
 441                 /* Ugh! */
 442                 orefdst = skb_in->_skb_refdst; /* save old refdst */
 443                 err = ip_route_input(skb_in, fl4_dec.daddr, fl4_dec.saddr,
 444                                      RT_TOS(tos), rt2->dst.dev);
 445
 446                 dst_release(&rt2->dst);
 447                 rt2 = skb_rtable(skb_in);
 448                 skb_in->_skb_refdst = orefdst; /* restore old refdst */
 449         }
 450
 451         if (err)
 452                 goto relookup_failed;
 453
 454         rt2 = (struct rtable *) xfrm_lookup(net, &rt2->dst,
 455                                             flowi4_to_flowi(&fl4_dec), NULL,
 456                                             XFRM_LOOKUP_ICMP);
 457         if (!IS_ERR(rt2)) {
 458                 dst_release(&rt->dst);
 459                 memcpy(fl4, &fl4_dec, sizeof(*fl4));
 460                 rt = rt2;
 461         } else if (PTR_ERR(rt2) == -EPERM) {
 462                 if (rt)
 463                         dst_release(&rt->dst);
 464                 return rt2;
 465         } else {
 466                 err = PTR_ERR(rt2);
 467                 goto relookup_failed;
 468         }
 469         return rt;
 470
 471 relookup_failed:
 472         if (rt)
 473                 return rt;
 474         return ERR_PTR(err);
 475 }
 476
 477 /*
 478  *      Send an ICMP message in response to a situation
 479  *
 480  *      RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header.
 481  *                MAY send more (we do).
 482  *                      MUST NOT change this header information.
 483  *                      MUST NOT reply to a multicast/broadcast IP address.
 484  *                      MUST NOT reply to a multicast/broadcast MAC address.
 485  *                      MUST reply to only the first fragment.
 486  */
 487
 488 void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info)
 489 {
 490         struct iphdr *iph;
 491         int room;
 492         struct icmp_bxm *icmp_param;
 493         struct rtable *rt = skb_rtable(skb_in);
 494         struct ipcm_cookie ipc;
 495         struct flowi4 fl4;
 496         __be32 saddr;
 497         u8  tos;
 498         u32 mark;
 499         struct net *net;
 500         struct sock *sk;
 501
 502         if (!rt)
 503                 goto out;
 504         net = dev_net(rt->dst.dev);
 505
 506         /*
 507          *      Find the original header. It is expected to be valid, of course.
 508          *      Check this, icmp_send is called from the most obscure devices
 509          *      sometimes.
 510          */
 511         iph = ip_hdr(skb_in);
 512
 513         if ((u8 *)iph < skb_in->head ||
 514             (skb_network_header(skb_in) + sizeof(*iph)) >
 515             skb_tail_pointer(skb_in))
 516                 goto out;
 517
 518         /*
 519          *      No replies to physical multicast/broadcast
 520          */
 521         if (skb_in->pkt_type != PACKET_HOST)
 522                 goto out;
 523
 524         /*
 525          *      Now check at the protocol level
 526          */
 527         if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
 528                 goto out;
 529
 530         /*
 531          *      Only reply to fragment 0. We byte re-order the constant
 532          *      mask for efficiency.
 533          */
 534         if (iph->frag_off & htons(IP_OFFSET))
 535                 goto out;
 536
 537         /*
 538          *      If we send an ICMP error to an ICMP error a mess would result..
 539          */
 540         if (icmp_pointers[type].error) {
 541                 /*
 542                  *      We are an error, check if we are replying to an
 543                  *      ICMP error
 544                  */
 545                 if (iph->protocol == IPPROTO_ICMP) {
 546                         u8 _inner_type, *itp;
 547
 548                         itp = skb_header_pointer(skb_in,
 549                                                  skb_network_header(skb_in) +
 550                                                  (iph->ihl << 2) +
 551                                                  offsetof(struct icmphdr,
 552                                                           type) -
 553                                                  skb_in->data,
 554                                                  sizeof(_inner_type),
 555                                                  &_inner_type);
 556                         if (itp == NULL)
 557                                 goto out;
 558
 559                         /*
 560                          *      Assume any unknown ICMP type is an error. This
 561                          *      isn't specified by the RFC, but think about it..
 562                          */
 563                         if (*itp > NR_ICMP_TYPES ||
 564                             icmp_pointers[*itp].error)
 565                                 goto out;
 566                 }
 567         }
 568
 569         icmp_param = kmalloc(sizeof(*icmp_param), GFP_ATOMIC);
 570         if (!icmp_param)
 571                 return;
 572
 573         sk = icmp_xmit_lock(net);
 574         if (sk == NULL)
 575                 goto out_free;
 576
 577         /*
 578          *      Construct source address and options.
 579          */
 580
 581         saddr = iph->daddr;
 582         if (!(rt->rt_flags & RTCF_LOCAL)) {
 583                 struct net_device *dev = NULL;
 584
 585                 rcu_read_lock();
 586                 if (rt_is_input_route(rt) &&
 587                     net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr)
 588                         dev = dev_get_by_index_rcu(net, inet_iif(skb_in));
 589
 590                 if (dev)
 591                         saddr = inet_select_addr(dev, 0, RT_SCOPE_LINK);
 592                 else
 593                         saddr = 0;
 594                 rcu_read_unlock();
 595         }
 596
 597         tos = icmp_pointers[type].error ? ((iph->tos & IPTOS_TOS_MASK) |
 598                                            IPTOS_PREC_INTERNETCONTROL) :
 599                                           iph->tos;
 600         mark = IP4_REPLY_MARK(net, skb_in->mark);
 601
 602         if (ip_options_echo(&icmp_param->replyopts.opt.opt, skb_in))
 603                 goto out_unlock;
 604
 605
 606         /*
 607          *      Prepare data for ICMP header.
 608          */
 609
 610         icmp_param->data.icmph.type      = type;
 611         icmp_param->data.icmph.code      = code;
 612         icmp_param->data.icmph.un.gateway = info;
 613         icmp_param->data.icmph.checksum  = 0;
 614         icmp_param->skb   = skb_in;
 615         icmp_param->offset = skb_network_offset(skb_in);
 616         inet_sk(sk)->tos = tos;
 617         sk->sk_mark = mark;
 618         ipc.addr = iph->saddr;
 619         ipc.opt = &icmp_param->replyopts.opt;
 620         ipc.tx_flags = 0;
 621         ipc.ttl = 0;
 622         ipc.tos = -1;
 623
 624         rt = icmp_route_lookup(net, &fl4, skb_in, iph, saddr, tos, mark,
 625                                type, code, icmp_param);
 626         if (IS_ERR(rt))
 627                 goto out_unlock;
 628
 629         if (!icmpv4_xrlim_allow(net, rt, &fl4, type, code))
 630                 goto ende;
 631
 632         /* RFC says return as much as we can without exceeding 576 bytes. */
 633
 634         room = dst_mtu(&rt->dst);
 635         if (room > 576)
 636                 room = 576;
 637         room -= sizeof(struct iphdr) + icmp_param->replyopts.opt.opt.optlen;
 638         room -= sizeof(struct icmphdr);
 639
 640         icmp_param->data_len = skb_in->len - icmp_param->offset;
 641         if (icmp_param->data_len > room)
 642                 icmp_param->data_len = room;
 643         icmp_param->head_len = sizeof(struct icmphdr);
 644
 645         icmp_push_reply(icmp_param, &fl4, &ipc, &rt);
 646 ende:
 647         ip_rt_put(rt);
 648 out_unlock:
 649         icmp_xmit_unlock(sk);
 650 out_free:
 651         kfree(icmp_param);
 652 out:;
 653 }
 654 EXPORT_SYMBOL(icmp_send);
 655
 656
 657 static void icmp_socket_deliver(struct sk_buff *skb, u32 info)
 658 {
 659         const struct iphdr *iph = (const struct iphdr *) skb->data;
 660         const struct net_protocol *ipprot;
 661         int protocol = iph->protocol;
 662
 663         /* Checkin full IP header plus 8 bytes of protocol to
 664          * avoid additional coding at protocol handlers.
 665          */
 666         if (!pskb_may_pull(skb, iph->ihl * 4 + 8)) {
 667                 ICMP_INC_STATS_BH(dev_net(skb->dev), ICMP_MIB_INERRORS);
 668                 return;
 669         }
 670
 671         raw_icmp_error(skb, protocol, info);
 672
 673         ipprot = rcu_dereference(inet_protos[protocol]);
 674         if (ipprot && ipprot->err_handler)
 675                 ipprot->err_handler(skb, info);
 676 }
 677
 678 static bool icmp_tag_validation(int proto)
 679 {
 680         bool ok;
 681
 682         rcu_read_lock();
 683         ok = rcu_dereference(inet_protos[proto])->icmp_strict_tag_validation;
 684         rcu_read_unlock();
 685         return ok;
 686 }
 687
 688 /*
 689  *      Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEED, ICMP_QUENCH, and
 690  *      ICMP_PARAMETERPROB.
 691  */
 692
 693 static void icmp_unreach(struct sk_buff *skb)
 694 {
 695         const struct iphdr *iph;
 696         struct icmphdr *icmph;
 697         struct net *net;
 698         u32 info = 0;
 699
 700         net = dev_net(skb_dst(skb)->dev);
 701
 702         /*
 703          *      Incomplete header ?
 704          *      Only checks for the IP header, there should be an
 705          *      additional check for longer headers in upper levels.
 706          */
 707
 708         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
 709                 goto out_err;
 710
 711         icmph = icmp_hdr(skb);
 712         iph   = (const struct iphdr *)skb->data;
 713
 714         if (iph->ihl < 5) /* Mangled header, drop. */
 715                 goto out_err;
 716
 717         if (icmph->type == ICMP_DEST_UNREACH) {
 718                 switch (icmph->code & 15) {
 719                 case ICMP_NET_UNREACH:
 720                 case ICMP_HOST_UNREACH:
 721                 case ICMP_PROT_UNREACH:
 722                 case ICMP_PORT_UNREACH:
 723                         break;
 724                 case ICMP_FRAG_NEEDED:
 725                         /* for documentation of the ip_no_pmtu_disc
 726                          * values please see
 727                          * Documentation/networking/ip-sysctl.txt
 728                          */
 729                         switch (net->ipv4.sysctl_ip_no_pmtu_disc) {
 730                         default:
 731                                 LIMIT_NETDEBUG(KERN_INFO pr_fmt("%pI4: fragmentation needed and DF set\n"),
 732                                                &iph->daddr);
 733                                 break;
 734                         case 2:
 735                                 goto out;
 736                         case 3:
 737                                 if (!icmp_tag_validation(iph->protocol))
 738                                         goto out;
 739                                 /* fall through */
 740                         case 0:
 741                                 info = ntohs(icmph->un.frag.mtu);
 742                         }
 743                         break;
 744                 case ICMP_SR_FAILED:
 745                         LIMIT_NETDEBUG(KERN_INFO pr_fmt("%pI4: Source Route Failed\n"),
 746                                        &iph->daddr);
 747                         break;
 748                 default:
 749                         break;
 750                 }
 751                 if (icmph->code > NR_ICMP_UNREACH)
 752                         goto out;
 753         } else if (icmph->type == ICMP_PARAMETERPROB)
 754                 info = ntohl(icmph->un.gateway) >> 24;
 755
 756         /*
 757          *      Throw it at our lower layers
 758          *
 759          *      RFC 1122: 3.2.2 MUST extract the protocol ID from the passed
 760          *                header.
 761          *      RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the
 762          *                transport layer.
 763          *      RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to
 764          *                transport layer.
 765          */
 766
 767         /*
 768          *      Check the other end isn't violating RFC 1122. Some routers send
 769          *      bogus responses to broadcast frames. If you see this message
 770          *      first check your netmask matches at both ends, if it does then
 771          *      get the other vendor to fix their kit.
 772          */
 773
 774         if (!net->ipv4.sysctl_icmp_ignore_bogus_error_responses &&
 775             inet_addr_type(net, iph->daddr) == RTN_BROADCAST) {
 776                 net_warn_ratelimited("%pI4 sent an invalid ICMP type %u, code %u error to a broadcast: %pI4 on %s\n",
 777                                      &ip_hdr(skb)->saddr,
 778                                      icmph->type, icmph->code,
 779                                      &iph->daddr, skb->dev->name);
 780                 goto out;
 781         }
 782
 783         icmp_socket_deliver(skb, info);
 784
 785 out:
 786         return;
 787 out_err:
 788         ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS);
 789         goto out;
 790 }
 791
 792
 793 /*
 794  *      Handle ICMP_REDIRECT.
 795  */
 796
 797 static void icmp_redirect(struct sk_buff *skb)
 798 {
 799         if (skb->len < sizeof(struct iphdr)) {
 800                 ICMP_INC_STATS_BH(dev_net(skb->dev), ICMP_MIB_INERRORS);
 801                 return;
 802         }
 803
 804         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
 805                 return;
 806
 807         icmp_socket_deliver(skb, icmp_hdr(skb)->un.gateway);
 808 }
 809
 810 /*
 811  *      Handle ICMP_ECHO ("ping") requests.
 812  *
 813  *      RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo
 814  *                requests.
 815  *      RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be
 816  *                included in the reply.
 817  *      RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring
 818  *                echo requests, MUST have default=NOT.
 819  *      See also WRT handling of options once they are done and working.
 820  */
 821
 822 static void icmp_echo(struct sk_buff *skb)
 823 {
 824         struct net *net;
 825
 826         net = dev_net(skb_dst(skb)->dev);
 827         if (!net->ipv4.sysctl_icmp_echo_ignore_all) {
 828                 struct icmp_bxm icmp_param;
 829
 830                 icmp_param.data.icmph      = *icmp_hdr(skb);
 831                 icmp_param.data.icmph.type = ICMP_ECHOREPLY;
 832                 icmp_param.skb             = skb;
 833                 icmp_param.offset          = 0;
 834                 icmp_param.data_len        = skb->len;
 835                 icmp_param.head_len        = sizeof(struct icmphdr);
 836                 icmp_reply(&icmp_param, skb);
 837         }
 838 }
 839
 840 /*
 841  *      Handle ICMP Timestamp requests.
 842  *      RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests.
 843  *                SHOULD be in the kernel for minimum random latency.
 844  *                MUST be accurate to a few minutes.
 845  *                MUST be updated at least at 15Hz.
 846  */
 847 static void icmp_timestamp(struct sk_buff *skb)
 848 {
 849         struct timespec tv;
 850         struct icmp_bxm icmp_param;
 851         /*
 852          *      Too short.
 853          */
 854         if (skb->len < 4)
 855                 goto out_err;
 856
 857         /*
 858          *      Fill in the current time as ms since midnight UT:
 859          */
 860         getnstimeofday(&tv);
 861         icmp_param.data.times[1] = htonl((tv.tv_sec % 86400) * MSEC_PER_SEC +
 862                                          tv.tv_nsec / NSEC_PER_MSEC);
 863         icmp_param.data.times[2] = icmp_param.data.times[1];
 864         if (skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4))
 865                 BUG();
 866         icmp_param.data.icmph      = *icmp_hdr(skb);
 867         icmp_param.data.icmph.type = ICMP_TIMESTAMPREPLY;
 868         icmp_param.data.icmph.code = 0;
 869         icmp_param.skb             = skb;
 870         icmp_param.offset          = 0;
 871         icmp_param.data_len        = 0;
 872         icmp_param.head_len        = sizeof(struct icmphdr) + 12;
 873         icmp_reply(&icmp_param, skb);
 874 out:
 875         return;
 876 out_err:
 877         ICMP_INC_STATS_BH(dev_net(skb_dst(skb)->dev), ICMP_MIB_INERRORS);
 878         goto out;
 879 }
 880
 881 static void icmp_discard(struct sk_buff *skb)
 882 {
 883 }
 884
 885 /*
 886  *      Deal with incoming ICMP packets.
 887  */
 888 int icmp_rcv(struct sk_buff *skb)
 889 {
 890         struct icmphdr *icmph;
 891         struct rtable *rt = skb_rtable(skb);
 892         struct net *net = dev_net(rt->dst.dev);
 893
 894         if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
 895                 struct sec_path *sp = skb_sec_path(skb);
 896                 int nh;
 897
 898                 if (!(sp && sp->xvec[sp->len - 1]->props.flags &
 899                                  XFRM_STATE_ICMP))
 900                         goto drop;
 901
 902                 if (!pskb_may_pull(skb, sizeof(*icmph) + sizeof(struct iphdr)))
 903                         goto drop;
 904
 905                 nh = skb_network_offset(skb);
 906                 skb_set_network_header(skb, sizeof(*icmph));
 907
 908                 if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN, skb))
 909                         goto drop;
 910
 911                 skb_set_network_header(skb, nh);
 912         }
 913
 914         ICMP_INC_STATS_BH(net, ICMP_MIB_INMSGS);
 915
 916         if (skb_checksum_simple_validate(skb))
 917                 goto csum_error;
 918
 919         if (!pskb_pull(skb, sizeof(*icmph)))
 920                 goto error;
 921
 922         icmph = icmp_hdr(skb);
 923
 924         ICMPMSGIN_INC_STATS_BH(net, icmph->type);
 925         /*
 926          *      18 is the highest 'known' ICMP type. Anything else is a mystery
 927          *
 928          *      RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
 929          *                discarded.
 930          */
 931         if (icmph->type > NR_ICMP_TYPES)
 932                 goto error;
 933
 934
 935         /*
 936          *      Parse the ICMP message
 937          */
 938
 939         if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) {
 940                 /*
 941                  *      RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be
 942                  *        silently ignored (we let user decide with a sysctl).
 943                  *      RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently
 944                  *        discarded if to broadcast/multicast.
 945                  */
 946                 if ((icmph->type == ICMP_ECHO ||
 947                      icmph->type == ICMP_TIMESTAMP) &&
 948                     net->ipv4.sysctl_icmp_echo_ignore_broadcasts) {
 949                         goto error;
 950                 }
 951                 if (icmph->type != ICMP_ECHO &&
 952                     icmph->type != ICMP_TIMESTAMP &&
 953                     icmph->type != ICMP_ADDRESS &&
 954                     icmph->type != ICMP_ADDRESSREPLY) {
 955                         goto error;
 956                 }
 957         }
 958
 959         icmp_pointers[icmph->type].handler(skb);
 960
 961 drop:
 962         kfree_skb(skb);
 963         return 0;
 964 csum_error:
 965         ICMP_INC_STATS_BH(net, ICMP_MIB_CSUMERRORS);
 966 error:
 967         ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS);
 968         goto drop;
 969 }
 970
 971 void icmp_err(struct sk_buff *skb, u32 info)
 972 {
 973         struct iphdr *iph = (struct iphdr *)skb->data;
 974         int offset = iph->ihl<<2;
 975         struct icmphdr *icmph = (struct icmphdr *)(skb->data + offset);
 976         int type = icmp_hdr(skb)->type;
 977         int code = icmp_hdr(skb)->code;
 978         struct net *net = dev_net(skb->dev);
 979
 980         /*
 981          * Use ping_err to handle all icmp errors except those
 982          * triggered by ICMP_ECHOREPLY which sent from kernel.
 983          */
 984         if (icmph->type != ICMP_ECHOREPLY) {
 985                 ping_err(skb, offset, info);
 986                 return;
 987         }
 988
 989         if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 990                 ipv4_update_pmtu(skb, net, info, 0, 0, IPPROTO_ICMP, 0);
 991         else if (type == ICMP_REDIRECT)
 992                 ipv4_redirect(skb, net, 0, 0, IPPROTO_ICMP, 0);
 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                 .handler = ping_rcv,
1001         },
1002         [1] = {
1003                 .handler = icmp_discard,
1004                 .error = 1,
1005         },
1006         [2] = {
1007                 .handler = icmp_discard,
1008                 .error = 1,
1009         },
1010         [ICMP_DEST_UNREACH] = {
1011                 .handler = icmp_unreach,
1012                 .error = 1,
1013         },
1014         [ICMP_SOURCE_QUENCH] = {
1015                 .handler = icmp_unreach,
1016                 .error = 1,
1017         },
1018         [ICMP_REDIRECT] = {
1019                 .handler = icmp_redirect,
1020                 .error = 1,
1021         },
1022         [6] = {
1023                 .handler = icmp_discard,
1024                 .error = 1,
1025         },
1026         [7] = {
1027                 .handler = icmp_discard,
1028                 .error = 1,
1029         },
1030         [ICMP_ECHO] = {
1031                 .handler = icmp_echo,
1032         },
1033         [9] = {
1034                 .handler = icmp_discard,
1035                 .error = 1,
1036         },
1037         [10] = {
1038                 .handler = icmp_discard,
1039                 .error = 1,
1040         },
1041         [ICMP_TIME_EXCEEDED] = {
1042                 .handler = icmp_unreach,
1043                 .error = 1,
1044         },
1045         [ICMP_PARAMETERPROB] = {
1046                 .handler = icmp_unreach,
1047                 .error = 1,
1048         },
1049         [ICMP_TIMESTAMP] = {
1050                 .handler = icmp_timestamp,
1051         },
1052         [ICMP_TIMESTAMPREPLY] = {
1053                 .handler = icmp_discard,
1054         },
1055         [ICMP_INFO_REQUEST] = {
1056                 .handler = icmp_discard,
1057         },
1058         [ICMP_INFO_REPLY] = {
1059                 .handler = icmp_discard,
1060         },
1061         [ICMP_ADDRESS] = {
1062                 .handler = icmp_discard,
1063         },
1064         [ICMP_ADDRESSREPLY] = {
1065                 .handler = icmp_discard,
1066         },
1067 };
1068
1069 static void __net_exit icmp_sk_exit(struct net *net)
1070 {
1071         int i;
1072
1073         for_each_possible_cpu(i)
1074                 inet_ctl_sock_destroy(net->ipv4.icmp_sk[i]);
1075         kfree(net->ipv4.icmp_sk);
1076         net->ipv4.icmp_sk = NULL;
1077 }
1078
1079 static int __net_init icmp_sk_init(struct net *net)
1080 {
1081         int i, err;
1082
1083         net->ipv4.icmp_sk =
1084                 kzalloc(nr_cpu_ids * sizeof(struct sock *), GFP_KERNEL);
1085         if (net->ipv4.icmp_sk == NULL)
1086                 return -ENOMEM;
1087
1088         for_each_possible_cpu(i) {
1089                 struct sock *sk;
1090
1091                 err = inet_ctl_sock_create(&sk, PF_INET,
1092                                            SOCK_RAW, IPPROTO_ICMP, net);
1093                 if (err < 0)
1094                         goto fail;
1095
1096                 net->ipv4.icmp_sk[i] = sk;
1097
1098                 /* Enough space for 2 64K ICMP packets, including
1099                  * sk_buff/skb_shared_info struct overhead.
1100                  */
1101                 sk->sk_sndbuf = 2 * SKB_TRUESIZE(64 * 1024);
1102
1103                 /*
1104                  * Speedup sock_wfree()
1105                  */
1106                 sock_set_flag(sk, SOCK_USE_WRITE_QUEUE);
1107                 inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT;
1108         }
1109
1110         /* Control parameters for ECHO replies. */
1111         net->ipv4.sysctl_icmp_echo_ignore_all = 0;
1112         net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1;
1113
1114         /* Control parameter - ignore bogus broadcast responses? */
1115         net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1;
1116
1117         /*
1118          *      Configurable global rate limit.
1119          *
1120          *      ratelimit defines tokens/packet consumed for dst->rate_token
1121          *      bucket ratemask defines which icmp types are ratelimited by
1122          *      setting it's bit position.
1123          *
1124          *      default:
1125          *      dest unreachable (3), source quench (4),
1126          *      time exceeded (11), parameter problem (12)
1127          */
1128
1129         net->ipv4.sysctl_icmp_ratelimit = 1 * HZ;
1130         net->ipv4.sysctl_icmp_ratemask = 0x1818;
1131         net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0;
1132
1133         return 0;
1134
1135 fail:
1136         for_each_possible_cpu(i)
1137                 inet_ctl_sock_destroy(net->ipv4.icmp_sk[i]);
1138         kfree(net->ipv4.icmp_sk);
1139         return err;
1140 }
1141
1142 static struct pernet_operations __net_initdata icmp_sk_ops = {
1143        .init = icmp_sk_init,
1144        .exit = icmp_sk_exit,
1145 };
1146
1147 int __init icmp_init(void)
1148 {
1149         return register_pernet_subsys(&icmp_sk_ops);
1150 }