net/ipv4/icmp.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *      NET3:   Implementation of the ICMP protocol layer.
   4  *
   5  *              Alan Cox, <[email protected]>
   6  *
   7  *      Some of the function names and the icmp unreach table for this
   8  *      module were derived from [icmp.c 1.0.11 06/02/93] by
   9  *      Ross Biro, Fred N. van Kempen, Mark Evans, Alan Cox, Gerhard Koerting.
  10  *      Other than that this module is a complete rewrite.
  11  *
  12  *      Fixes:
  13  *      Clemens Fruhwirth       :       introduce global icmp rate limiting
  14  *                                      with icmp type masking ability instead
  15  *                                      of broken per type icmp timeouts.
  16  *              Mike Shaver     :       RFC1122 checks.
  17  *              Alan Cox        :       Multicast ping reply as self.
  18  *              Alan Cox        :       Fix atomicity lockup in ip_build_xmit
  19  *                                      call.
  20  *              Alan Cox        :       Added 216,128 byte paths to the MTU
  21  *                                      code.
  22  *              Martin Mares    :       RFC1812 checks.
  23  *              Martin Mares    :       Can be configured to follow redirects
  24  *                                      if acting as a router _without_ a
  25  *                                      routing protocol (RFC 1812).
  26  *              Martin Mares    :       Echo requests may be configured to
  27  *                                      be ignored (RFC 1812).
  28  *              Martin Mares    :       Limitation of ICMP error message
  29  *                                      transmit rate (RFC 1812).
  30  *              Martin Mares    :       TOS and Precedence set correctly
  31  *                                      (RFC 1812).
  32  *              Martin Mares    :       Now copying as much data from the
  33  *                                      original packet as we can without
  34  *                                      exceeding 576 bytes (RFC 1812).
  35  *      Willy Konynenberg       :       Transparent proxying support.
  36  *              Keith Owens     :       RFC1191 correction for 4.2BSD based
  37  *                                      path MTU bug.
  38  *              Thomas Quinot   :       ICMP Dest Unreach codes up to 15 are
  39  *                                      valid (RFC 1812).
  40  *              Andi Kleen      :       Check all packet lengths properly
  41  *                                      and moved all kfree_skb() up to
  42  *                                      icmp_rcv.
  43  *              Andi Kleen      :       Move the rate limit bookkeeping
  44  *                                      into the dest entry and use a token
  45  *                                      bucket filter (thanks to ANK). Make
  46  *                                      the rates sysctl configurable.
  47  *              Yu Tianli       :       Fixed two ugly bugs in icmp_send
  48  *                                      - IP option length was accounted wrongly
  49  *                                      - ICMP header length was not accounted
  50  *                                        at all.
  51  *              Tristan Greaves :       Added sysctl option to ignore bogus
  52  *                                      broadcast responses from broken routers.
  53  *
  54  * To Fix:
  55  *
  56  *      - Should use skb_pull() instead of all the manual checking.
  57  *        This would also greatly simply some upper layer error handlers. --AK
  58  */
  59
  60 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  61
  62 #include <linux/module.h>
  63 #include <linux/types.h>
  64 #include <linux/jiffies.h>
  65 #include <linux/kernel.h>
  66 #include <linux/fcntl.h>
  67 #include <linux/socket.h>
  68 #include <linux/in.h>
  69 #include <linux/inet.h>
  70 #include <linux/inetdevice.h>
  71 #include <linux/netdevice.h>
  72 #include <linux/string.h>
  73 #include <linux/netfilter_ipv4.h>
  74 #include <linux/slab.h>
  75 #include <net/snmp.h>
  76 #include <net/ip.h>
  77 #include <net/route.h>
  78 #include <net/protocol.h>
  79 #include <net/icmp.h>
  80 #include <net/tcp.h>
  81 #include <net/udp.h>
  82 #include <net/raw.h>
  83 #include <net/ping.h>
  84 #include <linux/skbuff.h>
  85 #include <net/sock.h>
  86 #include <linux/errno.h>
  87 #include <linux/timer.h>
  88 #include <linux/init.h>
  89 #include <linux/uaccess.h>
  90 #include <net/checksum.h>
  91 #include <net/xfrm.h>
  92 #include <net/inet_common.h>
  93 #include <net/ip_fib.h>
  94 #include <net/l3mdev.h>
  95 #include <net/addrconf.h>
  96 #define CREATE_TRACE_POINTS
  97 #include <trace/events/icmp.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         enum skb_drop_reason (*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 static DEFINE_PER_CPU(struct sock *, ipv4_icmp_sk);
 199
 200 /* Called with BH disabled */
 201 static inline struct sock *icmp_xmit_lock(struct net *net)
 202 {
 203         struct sock *sk;
 204
 205         sk = this_cpu_read(ipv4_icmp_sk);
 206
 207         if (unlikely(!spin_trylock(&sk->sk_lock.slock))) {
 208                 /* This can happen if the output path signals a
 209                  * dst_link_failure() for an outgoing ICMP packet.
 210                  */
 211                 return NULL;
 212         }
 213         sock_net_set(sk, net);
 214         return sk;
 215 }
 216
 217 static inline void icmp_xmit_unlock(struct sock *sk)
 218 {
 219         sock_net_set(sk, &init_net);
 220         spin_unlock(&sk->sk_lock.slock);
 221 }
 222
 223 int sysctl_icmp_msgs_per_sec __read_mostly = 1000;
 224 int sysctl_icmp_msgs_burst __read_mostly = 50;
 225
 226 static struct {
 227         spinlock_t      lock;
 228         u32             credit;
 229         u32             stamp;
 230 } icmp_global = {
 231         .lock           = __SPIN_LOCK_UNLOCKED(icmp_global.lock),
 232 };
 233
 234 /**
 235  * icmp_global_allow - Are we allowed to send one more ICMP message ?
 236  *
 237  * Uses a token bucket to limit our ICMP messages to ~sysctl_icmp_msgs_per_sec.
 238  * Returns false if we reached the limit and can not send another packet.
 239  * Note: called with BH disabled
 240  */
 241 bool icmp_global_allow(void)
 242 {
 243         u32 credit, delta, incr = 0, now = (u32)jiffies;
 244         bool rc = false;
 245
 246         /* Check if token bucket is empty and cannot be refilled
 247          * without taking the spinlock. The READ_ONCE() are paired
 248          * with the following WRITE_ONCE() in this same function.
 249          */
 250         if (!READ_ONCE(icmp_global.credit)) {
 251                 delta = min_t(u32, now - READ_ONCE(icmp_global.stamp), HZ);
 252                 if (delta < HZ / 50)
 253                         return false;
 254         }
 255
 256         spin_lock(&icmp_global.lock);
 257         delta = min_t(u32, now - icmp_global.stamp, HZ);
 258         if (delta >= HZ / 50) {
 259                 incr = READ_ONCE(sysctl_icmp_msgs_per_sec) * delta / HZ;
 260                 if (incr)
 261                         WRITE_ONCE(icmp_global.stamp, now);
 262         }
 263         credit = min_t(u32, icmp_global.credit + incr,
 264                        READ_ONCE(sysctl_icmp_msgs_burst));
 265         if (credit) {
 266                 /* We want to use a credit of one in average, but need to randomize
 267                  * it for security reasons.
 268                  */
 269                 credit = max_t(int, credit - get_random_u32_below(3), 0);
 270                 rc = true;
 271         }
 272         WRITE_ONCE(icmp_global.credit, credit);
 273         spin_unlock(&icmp_global.lock);
 274         return rc;
 275 }
 276 EXPORT_SYMBOL(icmp_global_allow);
 277
 278 static bool icmpv4_mask_allow(struct net *net, int type, int code)
 279 {
 280         if (type > NR_ICMP_TYPES)
 281                 return true;
 282
 283         /* Don't limit PMTU discovery. */
 284         if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 285                 return true;
 286
 287         /* Limit if icmp type is enabled in ratemask. */
 288         if (!((1 << type) & READ_ONCE(net->ipv4.sysctl_icmp_ratemask)))
 289                 return true;
 290
 291         return false;
 292 }
 293
 294 static bool icmpv4_global_allow(struct net *net, int type, int code)
 295 {
 296         if (icmpv4_mask_allow(net, type, code))
 297                 return true;
 298
 299         if (icmp_global_allow())
 300                 return true;
 301
 302         __ICMP_INC_STATS(net, ICMP_MIB_RATELIMITGLOBAL);
 303         return false;
 304 }
 305
 306 /*
 307  *      Send an ICMP frame.
 308  */
 309
 310 static bool icmpv4_xrlim_allow(struct net *net, struct rtable *rt,
 311                                struct flowi4 *fl4, int type, int code)
 312 {
 313         struct dst_entry *dst = &rt->dst;
 314         struct inet_peer *peer;
 315         bool rc = true;
 316         int vif;
 317
 318         if (icmpv4_mask_allow(net, type, code))
 319                 goto out;
 320
 321         /* No rate limit on loopback */
 322         if (dst->dev && (dst->dev->flags&IFF_LOOPBACK))
 323                 goto out;
 324
 325         vif = l3mdev_master_ifindex(dst->dev);
 326         peer = inet_getpeer_v4(net->ipv4.peers, fl4->daddr, vif, 1);
 327         rc = inet_peer_xrlim_allow(peer,
 328                                    READ_ONCE(net->ipv4.sysctl_icmp_ratelimit));
 329         if (peer)
 330                 inet_putpeer(peer);
 331 out:
 332         if (!rc)
 333                 __ICMP_INC_STATS(net, ICMP_MIB_RATELIMITHOST);
 334         return rc;
 335 }
 336
 337 /*
 338  *      Maintain the counters used in the SNMP statistics for outgoing ICMP
 339  */
 340 void icmp_out_count(struct net *net, unsigned char type)
 341 {
 342         ICMPMSGOUT_INC_STATS(net, type);
 343         ICMP_INC_STATS(net, ICMP_MIB_OUTMSGS);
 344 }
 345
 346 /*
 347  *      Checksum each fragment, and on the first include the headers and final
 348  *      checksum.
 349  */
 350 static int icmp_glue_bits(void *from, char *to, int offset, int len, int odd,
 351                           struct sk_buff *skb)
 352 {
 353         struct icmp_bxm *icmp_param = from;
 354         __wsum csum;
 355
 356         csum = skb_copy_and_csum_bits(icmp_param->skb,
 357                                       icmp_param->offset + offset,
 358                                       to, len);
 359
 360         skb->csum = csum_block_add(skb->csum, csum, odd);
 361         if (icmp_pointers[icmp_param->data.icmph.type].error)
 362                 nf_ct_attach(skb, icmp_param->skb);
 363         return 0;
 364 }
 365
 366 static void icmp_push_reply(struct sock *sk,
 367                             struct icmp_bxm *icmp_param,
 368                             struct flowi4 *fl4,
 369                             struct ipcm_cookie *ipc, struct rtable **rt)
 370 {
 371         struct sk_buff *skb;
 372
 373         if (ip_append_data(sk, fl4, icmp_glue_bits, icmp_param,
 374                            icmp_param->data_len+icmp_param->head_len,
 375                            icmp_param->head_len,
 376                            ipc, rt, MSG_DONTWAIT) < 0) {
 377                 __ICMP_INC_STATS(sock_net(sk), ICMP_MIB_OUTERRORS);
 378                 ip_flush_pending_frames(sk);
 379         } else if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {
 380                 struct icmphdr *icmph = icmp_hdr(skb);
 381                 __wsum csum;
 382                 struct sk_buff *skb1;
 383
 384                 csum = csum_partial_copy_nocheck((void *)&icmp_param->data,
 385                                                  (char *)icmph,
 386                                                  icmp_param->head_len);
 387                 skb_queue_walk(&sk->sk_write_queue, skb1) {
 388                         csum = csum_add(csum, skb1->csum);
 389                 }
 390                 icmph->checksum = csum_fold(csum);
 391                 skb->ip_summed = CHECKSUM_NONE;
 392                 ip_push_pending_frames(sk, fl4);
 393         }
 394 }
 395
 396 /*
 397  *      Driving logic for building and sending ICMP messages.
 398  */
 399
 400 static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
 401 {
 402         struct ipcm_cookie ipc;
 403         struct rtable *rt = skb_rtable(skb);
 404         struct net *net = dev_net(rt->dst.dev);
 405         struct flowi4 fl4;
 406         struct sock *sk;
 407         struct inet_sock *inet;
 408         __be32 daddr, saddr;
 409         u32 mark = IP4_REPLY_MARK(net, skb->mark);
 410         int type = icmp_param->data.icmph.type;
 411         int code = icmp_param->data.icmph.code;
 412
 413         if (ip_options_echo(net, &icmp_param->replyopts.opt.opt, skb))
 414                 return;
 415
 416         /* Needed by both icmp_global_allow and icmp_xmit_lock */
 417         local_bh_disable();
 418
 419         /* global icmp_msgs_per_sec */
 420         if (!icmpv4_global_allow(net, type, code))
 421                 goto out_bh_enable;
 422
 423         sk = icmp_xmit_lock(net);
 424         if (!sk)
 425                 goto out_bh_enable;
 426         inet = inet_sk(sk);
 427
 428         icmp_param->data.icmph.checksum = 0;
 429
 430         ipcm_init(&ipc);
 431         inet->tos = ip_hdr(skb)->tos;
 432         ipc.sockc.mark = mark;
 433         daddr = ipc.addr = ip_hdr(skb)->saddr;
 434         saddr = fib_compute_spec_dst(skb);
 435
 436         if (icmp_param->replyopts.opt.opt.optlen) {
 437                 ipc.opt = &icmp_param->replyopts.opt;
 438                 if (ipc.opt->opt.srr)
 439                         daddr = icmp_param->replyopts.opt.opt.faddr;
 440         }
 441         memset(&fl4, 0, sizeof(fl4));
 442         fl4.daddr = daddr;
 443         fl4.saddr = saddr;
 444         fl4.flowi4_mark = mark;
 445         fl4.flowi4_uid = sock_net_uid(net, NULL);
 446         fl4.flowi4_tos = RT_TOS(ip_hdr(skb)->tos);
 447         fl4.flowi4_proto = IPPROTO_ICMP;
 448         fl4.flowi4_oif = l3mdev_master_ifindex(skb->dev);
 449         security_skb_classify_flow(skb, flowi4_to_flowi_common(&fl4));
 450         rt = ip_route_output_key(net, &fl4);
 451         if (IS_ERR(rt))
 452                 goto out_unlock;
 453         if (icmpv4_xrlim_allow(net, rt, &fl4, type, code))
 454                 icmp_push_reply(sk, icmp_param, &fl4, &ipc, &rt);
 455         ip_rt_put(rt);
 456 out_unlock:
 457         icmp_xmit_unlock(sk);
 458 out_bh_enable:
 459         local_bh_enable();
 460 }
 461
 462 /*
 463  * The device used for looking up which routing table to use for sending an ICMP
 464  * error is preferably the source whenever it is set, which should ensure the
 465  * icmp error can be sent to the source host, else lookup using the routing
 466  * table of the destination device, else use the main routing table (index 0).
 467  */
 468 static struct net_device *icmp_get_route_lookup_dev(struct sk_buff *skb)
 469 {
 470         struct net_device *route_lookup_dev = NULL;
 471
 472         if (skb->dev)
 473                 route_lookup_dev = skb->dev;
 474         else if (skb_dst(skb))
 475                 route_lookup_dev = skb_dst(skb)->dev;
 476         return route_lookup_dev;
 477 }
 478
 479 static struct rtable *icmp_route_lookup(struct net *net,
 480                                         struct flowi4 *fl4,
 481                                         struct sk_buff *skb_in,
 482                                         const struct iphdr *iph,
 483                                         __be32 saddr, u8 tos, u32 mark,
 484                                         int type, int code,
 485                                         struct icmp_bxm *param)
 486 {
 487         struct net_device *route_lookup_dev;
 488         struct dst_entry *dst, *dst2;
 489         struct rtable *rt, *rt2;
 490         struct flowi4 fl4_dec;
 491         int err;
 492
 493         memset(fl4, 0, sizeof(*fl4));
 494         fl4->daddr = (param->replyopts.opt.opt.srr ?
 495                       param->replyopts.opt.opt.faddr : iph->saddr);
 496         fl4->saddr = saddr;
 497         fl4->flowi4_mark = mark;
 498         fl4->flowi4_uid = sock_net_uid(net, NULL);
 499         fl4->flowi4_tos = RT_TOS(tos);
 500         fl4->flowi4_proto = IPPROTO_ICMP;
 501         fl4->fl4_icmp_type = type;
 502         fl4->fl4_icmp_code = code;
 503         route_lookup_dev = icmp_get_route_lookup_dev(skb_in);
 504         fl4->flowi4_oif = l3mdev_master_ifindex(route_lookup_dev);
 505
 506         security_skb_classify_flow(skb_in, flowi4_to_flowi_common(fl4));
 507         rt = ip_route_output_key_hash(net, fl4, skb_in);
 508         if (IS_ERR(rt))
 509                 return rt;
 510
 511         /* No need to clone since we're just using its address. */
 512         rt2 = rt;
 513
 514         dst = xfrm_lookup(net, &rt->dst,
 515                           flowi4_to_flowi(fl4), NULL, 0);
 516         rt = dst_rtable(dst);
 517         if (!IS_ERR(dst)) {
 518                 if (rt != rt2)
 519                         return rt;
 520         } else if (PTR_ERR(dst) == -EPERM) {
 521                 rt = NULL;
 522         } else {
 523                 return rt;
 524         }
 525         err = xfrm_decode_session_reverse(net, skb_in, flowi4_to_flowi(&fl4_dec), AF_INET);
 526         if (err)
 527                 goto relookup_failed;
 528
 529         if (inet_addr_type_dev_table(net, route_lookup_dev,
 530                                      fl4_dec.saddr) == RTN_LOCAL) {
 531                 rt2 = __ip_route_output_key(net, &fl4_dec);
 532                 if (IS_ERR(rt2))
 533                         err = PTR_ERR(rt2);
 534         } else {
 535                 struct flowi4 fl4_2 = {};
 536                 unsigned long orefdst;
 537
 538                 fl4_2.daddr = fl4_dec.saddr;
 539                 rt2 = ip_route_output_key(net, &fl4_2);
 540                 if (IS_ERR(rt2)) {
 541                         err = PTR_ERR(rt2);
 542                         goto relookup_failed;
 543                 }
 544                 /* Ugh! */
 545                 orefdst = skb_in->_skb_refdst; /* save old refdst */
 546                 skb_dst_set(skb_in, NULL);
 547                 err = ip_route_input(skb_in, fl4_dec.daddr, fl4_dec.saddr,
 548                                      RT_TOS(tos), rt2->dst.dev);
 549
 550                 dst_release(&rt2->dst);
 551                 rt2 = skb_rtable(skb_in);
 552                 skb_in->_skb_refdst = orefdst; /* restore old refdst */
 553         }
 554
 555         if (err)
 556                 goto relookup_failed;
 557
 558         dst2 = xfrm_lookup(net, &rt2->dst, flowi4_to_flowi(&fl4_dec), NULL,
 559                            XFRM_LOOKUP_ICMP);
 560         rt2 = dst_rtable(dst2);
 561         if (!IS_ERR(dst2)) {
 562                 dst_release(&rt->dst);
 563                 memcpy(fl4, &fl4_dec, sizeof(*fl4));
 564                 rt = rt2;
 565         } else if (PTR_ERR(dst2) == -EPERM) {
 566                 if (rt)
 567                         dst_release(&rt->dst);
 568                 return rt2;
 569         } else {
 570                 err = PTR_ERR(dst2);
 571                 goto relookup_failed;
 572         }
 573         return rt;
 574
 575 relookup_failed:
 576         if (rt)
 577                 return rt;
 578         return ERR_PTR(err);
 579 }
 580
 581 /*
 582  *      Send an ICMP message in response to a situation
 583  *
 584  *      RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header.
 585  *                MAY send more (we do).
 586  *                      MUST NOT change this header information.
 587  *                      MUST NOT reply to a multicast/broadcast IP address.
 588  *                      MUST NOT reply to a multicast/broadcast MAC address.
 589  *                      MUST reply to only the first fragment.
 590  */
 591
 592 void __icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info,
 593                  const struct ip_options *opt)
 594 {
 595         struct iphdr *iph;
 596         int room;
 597         struct icmp_bxm icmp_param;
 598         struct rtable *rt = skb_rtable(skb_in);
 599         struct ipcm_cookie ipc;
 600         struct flowi4 fl4;
 601         __be32 saddr;
 602         u8  tos;
 603         u32 mark;
 604         struct net *net;
 605         struct sock *sk;
 606
 607         if (!rt)
 608                 goto out;
 609
 610         if (rt->dst.dev)
 611                 net = dev_net(rt->dst.dev);
 612         else if (skb_in->dev)
 613                 net = dev_net(skb_in->dev);
 614         else
 615                 goto out;
 616
 617         /*
 618          *      Find the original header. It is expected to be valid, of course.
 619          *      Check this, icmp_send is called from the most obscure devices
 620          *      sometimes.
 621          */
 622         iph = ip_hdr(skb_in);
 623
 624         if ((u8 *)iph < skb_in->head ||
 625             (skb_network_header(skb_in) + sizeof(*iph)) >
 626             skb_tail_pointer(skb_in))
 627                 goto out;
 628
 629         /*
 630          *      No replies to physical multicast/broadcast
 631          */
 632         if (skb_in->pkt_type != PACKET_HOST)
 633                 goto out;
 634
 635         /*
 636          *      Now check at the protocol level
 637          */
 638         if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
 639                 goto out;
 640
 641         /*
 642          *      Only reply to fragment 0. We byte re-order the constant
 643          *      mask for efficiency.
 644          */
 645         if (iph->frag_off & htons(IP_OFFSET))
 646                 goto out;
 647
 648         /*
 649          *      If we send an ICMP error to an ICMP error a mess would result..
 650          */
 651         if (icmp_pointers[type].error) {
 652                 /*
 653                  *      We are an error, check if we are replying to an
 654                  *      ICMP error
 655                  */
 656                 if (iph->protocol == IPPROTO_ICMP) {
 657                         u8 _inner_type, *itp;
 658
 659                         itp = skb_header_pointer(skb_in,
 660                                                  skb_network_header(skb_in) +
 661                                                  (iph->ihl << 2) +
 662                                                  offsetof(struct icmphdr,
 663                                                           type) -
 664                                                  skb_in->data,
 665                                                  sizeof(_inner_type),
 666                                                  &_inner_type);
 667                         if (!itp)
 668                                 goto out;
 669
 670                         /*
 671                          *      Assume any unknown ICMP type is an error. This
 672                          *      isn't specified by the RFC, but think about it..
 673                          */
 674                         if (*itp > NR_ICMP_TYPES ||
 675                             icmp_pointers[*itp].error)
 676                                 goto out;
 677                 }
 678         }
 679
 680         /* Needed by both icmp_global_allow and icmp_xmit_lock */
 681         local_bh_disable();
 682
 683         /* Check global sysctl_icmp_msgs_per_sec ratelimit, unless
 684          * incoming dev is loopback.  If outgoing dev change to not be
 685          * loopback, then peer ratelimit still work (in icmpv4_xrlim_allow)
 686          */
 687         if (!(skb_in->dev && (skb_in->dev->flags&IFF_LOOPBACK)) &&
 688               !icmpv4_global_allow(net, type, code))
 689                 goto out_bh_enable;
 690
 691         sk = icmp_xmit_lock(net);
 692         if (!sk)
 693                 goto out_bh_enable;
 694
 695         /*
 696          *      Construct source address and options.
 697          */
 698
 699         saddr = iph->daddr;
 700         if (!(rt->rt_flags & RTCF_LOCAL)) {
 701                 struct net_device *dev = NULL;
 702
 703                 rcu_read_lock();
 704                 if (rt_is_input_route(rt) &&
 705                     READ_ONCE(net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr))
 706                         dev = dev_get_by_index_rcu(net, inet_iif(skb_in));
 707
 708                 if (dev)
 709                         saddr = inet_select_addr(dev, iph->saddr,
 710                                                  RT_SCOPE_LINK);
 711                 else
 712                         saddr = 0;
 713                 rcu_read_unlock();
 714         }
 715
 716         tos = icmp_pointers[type].error ? (RT_TOS(iph->tos) |
 717                                            IPTOS_PREC_INTERNETCONTROL) :
 718                                            iph->tos;
 719         mark = IP4_REPLY_MARK(net, skb_in->mark);
 720
 721         if (__ip_options_echo(net, &icmp_param.replyopts.opt.opt, skb_in, opt))
 722                 goto out_unlock;
 723
 724
 725         /*
 726          *      Prepare data for ICMP header.
 727          */
 728
 729         icmp_param.data.icmph.type       = type;
 730         icmp_param.data.icmph.code       = code;
 731         icmp_param.data.icmph.un.gateway = info;
 732         icmp_param.data.icmph.checksum   = 0;
 733         icmp_param.skb    = skb_in;
 734         icmp_param.offset = skb_network_offset(skb_in);
 735         inet_sk(sk)->tos = tos;
 736         ipcm_init(&ipc);
 737         ipc.addr = iph->saddr;
 738         ipc.opt = &icmp_param.replyopts.opt;
 739         ipc.sockc.mark = mark;
 740
 741         rt = icmp_route_lookup(net, &fl4, skb_in, iph, saddr, tos, mark,
 742                                type, code, &icmp_param);
 743         if (IS_ERR(rt))
 744                 goto out_unlock;
 745
 746         /* peer icmp_ratelimit */
 747         if (!icmpv4_xrlim_allow(net, rt, &fl4, type, code))
 748                 goto ende;
 749
 750         /* RFC says return as much as we can without exceeding 576 bytes. */
 751
 752         room = dst_mtu(&rt->dst);
 753         if (room > 576)
 754                 room = 576;
 755         room -= sizeof(struct iphdr) + icmp_param.replyopts.opt.opt.optlen;
 756         room -= sizeof(struct icmphdr);
 757         /* Guard against tiny mtu. We need to include at least one
 758          * IP network header for this message to make any sense.
 759          */
 760         if (room <= (int)sizeof(struct iphdr))
 761                 goto ende;
 762
 763         icmp_param.data_len = skb_in->len - icmp_param.offset;
 764         if (icmp_param.data_len > room)
 765                 icmp_param.data_len = room;
 766         icmp_param.head_len = sizeof(struct icmphdr);
 767
 768         /* if we don't have a source address at this point, fall back to the
 769          * dummy address instead of sending out a packet with a source address
 770          * of 0.0.0.0
 771          */
 772         if (!fl4.saddr)
 773                 fl4.saddr = htonl(INADDR_DUMMY);
 774
 775         trace_icmp_send(skb_in, type, code);
 776
 777         icmp_push_reply(sk, &icmp_param, &fl4, &ipc, &rt);
 778 ende:
 779         ip_rt_put(rt);
 780 out_unlock:
 781         icmp_xmit_unlock(sk);
 782 out_bh_enable:
 783         local_bh_enable();
 784 out:;
 785 }
 786 EXPORT_SYMBOL(__icmp_send);
 787
 788 #if IS_ENABLED(CONFIG_NF_NAT)
 789 #include <net/netfilter/nf_conntrack.h>
 790 void icmp_ndo_send(struct sk_buff *skb_in, int type, int code, __be32 info)
 791 {
 792         struct sk_buff *cloned_skb = NULL;
 793         struct ip_options opts = { 0 };
 794         enum ip_conntrack_info ctinfo;
 795         struct nf_conn *ct;
 796         __be32 orig_ip;
 797
 798         ct = nf_ct_get(skb_in, &ctinfo);
 799         if (!ct || !(ct->status & IPS_SRC_NAT)) {
 800                 __icmp_send(skb_in, type, code, info, &opts);
 801                 return;
 802         }
 803
 804         if (skb_shared(skb_in))
 805                 skb_in = cloned_skb = skb_clone(skb_in, GFP_ATOMIC);
 806
 807         if (unlikely(!skb_in || skb_network_header(skb_in) < skb_in->head ||
 808             (skb_network_header(skb_in) + sizeof(struct iphdr)) >
 809             skb_tail_pointer(skb_in) || skb_ensure_writable(skb_in,
 810             skb_network_offset(skb_in) + sizeof(struct iphdr))))
 811                 goto out;
 812
 813         orig_ip = ip_hdr(skb_in)->saddr;
 814         ip_hdr(skb_in)->saddr = ct->tuplehash[0].tuple.src.u3.ip;
 815         __icmp_send(skb_in, type, code, info, &opts);
 816         ip_hdr(skb_in)->saddr = orig_ip;
 817 out:
 818         consume_skb(cloned_skb);
 819 }
 820 EXPORT_SYMBOL(icmp_ndo_send);
 821 #endif
 822
 823 static void icmp_socket_deliver(struct sk_buff *skb, u32 info)
 824 {
 825         const struct iphdr *iph = (const struct iphdr *)skb->data;
 826         const struct net_protocol *ipprot;
 827         int protocol = iph->protocol;
 828
 829         /* Checkin full IP header plus 8 bytes of protocol to
 830          * avoid additional coding at protocol handlers.
 831          */
 832         if (!pskb_may_pull(skb, iph->ihl * 4 + 8)) {
 833                 __ICMP_INC_STATS(dev_net(skb->dev), ICMP_MIB_INERRORS);
 834                 return;
 835         }
 836
 837         raw_icmp_error(skb, protocol, info);
 838
 839         ipprot = rcu_dereference(inet_protos[protocol]);
 840         if (ipprot && ipprot->err_handler)
 841                 ipprot->err_handler(skb, info);
 842 }
 843
 844 static bool icmp_tag_validation(int proto)
 845 {
 846         bool ok;
 847
 848         rcu_read_lock();
 849         ok = rcu_dereference(inet_protos[proto])->icmp_strict_tag_validation;
 850         rcu_read_unlock();
 851         return ok;
 852 }
 853
 854 /*
 855  *      Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEEDED, ICMP_QUENCH, and
 856  *      ICMP_PARAMETERPROB.
 857  */
 858
 859 static enum skb_drop_reason icmp_unreach(struct sk_buff *skb)
 860 {
 861         enum skb_drop_reason reason = SKB_NOT_DROPPED_YET;
 862         const struct iphdr *iph;
 863         struct icmphdr *icmph;
 864         struct net *net;
 865         u32 info = 0;
 866
 867         net = dev_net(skb_dst(skb)->dev);
 868
 869         /*
 870          *      Incomplete header ?
 871          *      Only checks for the IP header, there should be an
 872          *      additional check for longer headers in upper levels.
 873          */
 874
 875         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
 876                 goto out_err;
 877
 878         icmph = icmp_hdr(skb);
 879         iph   = (const struct iphdr *)skb->data;
 880
 881         if (iph->ihl < 5)  { /* Mangled header, drop. */
 882                 reason = SKB_DROP_REASON_IP_INHDR;
 883                 goto out_err;
 884         }
 885
 886         switch (icmph->type) {
 887         case ICMP_DEST_UNREACH:
 888                 switch (icmph->code & 15) {
 889                 case ICMP_NET_UNREACH:
 890                 case ICMP_HOST_UNREACH:
 891                 case ICMP_PROT_UNREACH:
 892                 case ICMP_PORT_UNREACH:
 893                         break;
 894                 case ICMP_FRAG_NEEDED:
 895                         /* for documentation of the ip_no_pmtu_disc
 896                          * values please see
 897                          * Documentation/networking/ip-sysctl.rst
 898                          */
 899                         switch (READ_ONCE(net->ipv4.sysctl_ip_no_pmtu_disc)) {
 900                         default:
 901                                 net_dbg_ratelimited("%pI4: fragmentation needed and DF set\n",
 902                                                     &iph->daddr);
 903                                 break;
 904                         case 2:
 905                                 goto out;
 906                         case 3:
 907                                 if (!icmp_tag_validation(iph->protocol))
 908                                         goto out;
 909                                 fallthrough;
 910                         case 0:
 911                                 info = ntohs(icmph->un.frag.mtu);
 912                         }
 913                         break;
 914                 case ICMP_SR_FAILED:
 915                         net_dbg_ratelimited("%pI4: Source Route Failed\n",
 916                                             &iph->daddr);
 917                         break;
 918                 default:
 919                         break;
 920                 }
 921                 if (icmph->code > NR_ICMP_UNREACH)
 922                         goto out;
 923                 break;
 924         case ICMP_PARAMETERPROB:
 925                 info = ntohl(icmph->un.gateway) >> 24;
 926                 break;
 927         case ICMP_TIME_EXCEEDED:
 928                 __ICMP_INC_STATS(net, ICMP_MIB_INTIMEEXCDS);
 929                 if (icmph->code == ICMP_EXC_FRAGTIME)
 930                         goto out;
 931                 break;
 932         }
 933
 934         /*
 935          *      Throw it at our lower layers
 936          *
 937          *      RFC 1122: 3.2.2 MUST extract the protocol ID from the passed
 938          *                header.
 939          *      RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the
 940          *                transport layer.
 941          *      RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to
 942          *                transport layer.
 943          */
 944
 945         /*
 946          *      Check the other end isn't violating RFC 1122. Some routers send
 947          *      bogus responses to broadcast frames. If you see this message
 948          *      first check your netmask matches at both ends, if it does then
 949          *      get the other vendor to fix their kit.
 950          */
 951
 952         if (!READ_ONCE(net->ipv4.sysctl_icmp_ignore_bogus_error_responses) &&
 953             inet_addr_type_dev_table(net, skb->dev, iph->daddr) == RTN_BROADCAST) {
 954                 net_warn_ratelimited("%pI4 sent an invalid ICMP type %u, code %u error to a broadcast: %pI4 on %s\n",
 955                                      &ip_hdr(skb)->saddr,
 956                                      icmph->type, icmph->code,
 957                                      &iph->daddr, skb->dev->name);
 958                 goto out;
 959         }
 960
 961         icmp_socket_deliver(skb, info);
 962
 963 out:
 964         return reason;
 965 out_err:
 966         __ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
 967         return reason ?: SKB_DROP_REASON_NOT_SPECIFIED;
 968 }
 969
 970
 971 /*
 972  *      Handle ICMP_REDIRECT.
 973  */
 974
 975 static enum skb_drop_reason icmp_redirect(struct sk_buff *skb)
 976 {
 977         if (skb->len < sizeof(struct iphdr)) {
 978                 __ICMP_INC_STATS(dev_net(skb->dev), ICMP_MIB_INERRORS);
 979                 return SKB_DROP_REASON_PKT_TOO_SMALL;
 980         }
 981
 982         if (!pskb_may_pull(skb, sizeof(struct iphdr))) {
 983                 /* there aught to be a stat */
 984                 return SKB_DROP_REASON_NOMEM;
 985         }
 986
 987         icmp_socket_deliver(skb, ntohl(icmp_hdr(skb)->un.gateway));
 988         return SKB_NOT_DROPPED_YET;
 989 }
 990
 991 /*
 992  *      Handle ICMP_ECHO ("ping") and ICMP_EXT_ECHO ("PROBE") requests.
 993  *
 994  *      RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo
 995  *                requests.
 996  *      RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be
 997  *                included in the reply.
 998  *      RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring
 999  *                echo requests, MUST have default=NOT.
1000  *      RFC 8335: 8 MUST have a config option to enable/disable ICMP
1001  *                Extended Echo Functionality, MUST be disabled by default
1002  *      See also WRT handling of options once they are done and working.
1003  */
1004
1005 static enum skb_drop_reason icmp_echo(struct sk_buff *skb)
1006 {
1007         struct icmp_bxm icmp_param;
1008         struct net *net;
1009
1010         net = dev_net(skb_dst(skb)->dev);
1011         /* should there be an ICMP stat for ignored echos? */
1012         if (READ_ONCE(net->ipv4.sysctl_icmp_echo_ignore_all))
1013                 return SKB_NOT_DROPPED_YET;
1014
1015         icmp_param.data.icmph      = *icmp_hdr(skb);
1016         icmp_param.skb             = skb;
1017         icmp_param.offset          = 0;
1018         icmp_param.data_len        = skb->len;
1019         icmp_param.head_len        = sizeof(struct icmphdr);
1020
1021         if (icmp_param.data.icmph.type == ICMP_ECHO)
1022                 icmp_param.data.icmph.type = ICMP_ECHOREPLY;
1023         else if (!icmp_build_probe(skb, &icmp_param.data.icmph))
1024                 return SKB_NOT_DROPPED_YET;
1025
1026         icmp_reply(&icmp_param, skb);
1027         return SKB_NOT_DROPPED_YET;
1028 }
1029
1030 /*      Helper for icmp_echo and icmpv6_echo_reply.
1031  *      Searches for net_device that matches PROBE interface identifier
1032  *              and builds PROBE reply message in icmphdr.
1033  *
1034  *      Returns false if PROBE responses are disabled via sysctl
1035  */
1036
1037 bool icmp_build_probe(struct sk_buff *skb, struct icmphdr *icmphdr)
1038 {
1039         struct icmp_ext_hdr *ext_hdr, _ext_hdr;
1040         struct icmp_ext_echo_iio *iio, _iio;
1041         struct net *net = dev_net(skb->dev);
1042         struct inet6_dev *in6_dev;
1043         struct in_device *in_dev;
1044         struct net_device *dev;
1045         char buff[IFNAMSIZ];
1046         u16 ident_len;
1047         u8 status;
1048
1049         if (!READ_ONCE(net->ipv4.sysctl_icmp_echo_enable_probe))
1050                 return false;
1051
1052         /* We currently only support probing interfaces on the proxy node
1053          * Check to ensure L-bit is set
1054          */
1055         if (!(ntohs(icmphdr->un.echo.sequence) & 1))
1056                 return false;
1057         /* Clear status bits in reply message */
1058         icmphdr->un.echo.sequence &= htons(0xFF00);
1059         if (icmphdr->type == ICMP_EXT_ECHO)
1060                 icmphdr->type = ICMP_EXT_ECHOREPLY;
1061         else
1062                 icmphdr->type = ICMPV6_EXT_ECHO_REPLY;
1063         ext_hdr = skb_header_pointer(skb, 0, sizeof(_ext_hdr), &_ext_hdr);
1064         /* Size of iio is class_type dependent.
1065          * Only check header here and assign length based on ctype in the switch statement
1066          */
1067         iio = skb_header_pointer(skb, sizeof(_ext_hdr), sizeof(iio->extobj_hdr), &_iio);
1068         if (!ext_hdr || !iio)
1069                 goto send_mal_query;
1070         if (ntohs(iio->extobj_hdr.length) <= sizeof(iio->extobj_hdr) ||
1071             ntohs(iio->extobj_hdr.length) > sizeof(_iio))
1072                 goto send_mal_query;
1073         ident_len = ntohs(iio->extobj_hdr.length) - sizeof(iio->extobj_hdr);
1074         iio = skb_header_pointer(skb, sizeof(_ext_hdr),
1075                                  sizeof(iio->extobj_hdr) + ident_len, &_iio);
1076         if (!iio)
1077                 goto send_mal_query;
1078
1079         status = 0;
1080         dev = NULL;
1081         switch (iio->extobj_hdr.class_type) {
1082         case ICMP_EXT_ECHO_CTYPE_NAME:
1083                 if (ident_len >= IFNAMSIZ)
1084                         goto send_mal_query;
1085                 memset(buff, 0, sizeof(buff));
1086                 memcpy(buff, &iio->ident.name, ident_len);
1087                 dev = dev_get_by_name(net, buff);
1088                 break;
1089         case ICMP_EXT_ECHO_CTYPE_INDEX:
1090                 if (ident_len != sizeof(iio->ident.ifindex))
1091                         goto send_mal_query;
1092                 dev = dev_get_by_index(net, ntohl(iio->ident.ifindex));
1093                 break;
1094         case ICMP_EXT_ECHO_CTYPE_ADDR:
1095                 if (ident_len < sizeof(iio->ident.addr.ctype3_hdr) ||
1096                     ident_len != sizeof(iio->ident.addr.ctype3_hdr) +
1097                                  iio->ident.addr.ctype3_hdr.addrlen)
1098                         goto send_mal_query;
1099                 switch (ntohs(iio->ident.addr.ctype3_hdr.afi)) {
1100                 case ICMP_AFI_IP:
1101                         if (iio->ident.addr.ctype3_hdr.addrlen != sizeof(struct in_addr))
1102                                 goto send_mal_query;
1103                         dev = ip_dev_find(net, iio->ident.addr.ip_addr.ipv4_addr);
1104                         break;
1105 #if IS_ENABLED(CONFIG_IPV6)
1106                 case ICMP_AFI_IP6:
1107                         if (iio->ident.addr.ctype3_hdr.addrlen != sizeof(struct in6_addr))
1108                                 goto send_mal_query;
1109                         dev = ipv6_stub->ipv6_dev_find(net, &iio->ident.addr.ip_addr.ipv6_addr, dev);
1110                         dev_hold(dev);
1111                         break;
1112 #endif
1113                 default:
1114                         goto send_mal_query;
1115                 }
1116                 break;
1117         default:
1118                 goto send_mal_query;
1119         }
1120         if (!dev) {
1121                 icmphdr->code = ICMP_EXT_CODE_NO_IF;
1122                 return true;
1123         }
1124         /* Fill bits in reply message */
1125         if (dev->flags & IFF_UP)
1126                 status |= ICMP_EXT_ECHOREPLY_ACTIVE;
1127
1128         in_dev = __in_dev_get_rcu(dev);
1129         if (in_dev && rcu_access_pointer(in_dev->ifa_list))
1130                 status |= ICMP_EXT_ECHOREPLY_IPV4;
1131
1132         in6_dev = __in6_dev_get(dev);
1133         if (in6_dev && !list_empty(&in6_dev->addr_list))
1134                 status |= ICMP_EXT_ECHOREPLY_IPV6;
1135
1136         dev_put(dev);
1137         icmphdr->un.echo.sequence |= htons(status);
1138         return true;
1139 send_mal_query:
1140         icmphdr->code = ICMP_EXT_CODE_MAL_QUERY;
1141         return true;
1142 }
1143 EXPORT_SYMBOL_GPL(icmp_build_probe);
1144
1145 /*
1146  *      Handle ICMP Timestamp requests.
1147  *      RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests.
1148  *                SHOULD be in the kernel for minimum random latency.
1149  *                MUST be accurate to a few minutes.
1150  *                MUST be updated at least at 15Hz.
1151  */
1152 static enum skb_drop_reason icmp_timestamp(struct sk_buff *skb)
1153 {
1154         struct icmp_bxm icmp_param;
1155         /*
1156          *      Too short.
1157          */
1158         if (skb->len < 4)
1159                 goto out_err;
1160
1161         /*
1162          *      Fill in the current time as ms since midnight UT:
1163          */
1164         icmp_param.data.times[1] = inet_current_timestamp();
1165         icmp_param.data.times[2] = icmp_param.data.times[1];
1166
1167         BUG_ON(skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4));
1168
1169         icmp_param.data.icmph      = *icmp_hdr(skb);
1170         icmp_param.data.icmph.type = ICMP_TIMESTAMPREPLY;
1171         icmp_param.data.icmph.code = 0;
1172         icmp_param.skb             = skb;
1173         icmp_param.offset          = 0;
1174         icmp_param.data_len        = 0;
1175         icmp_param.head_len        = sizeof(struct icmphdr) + 12;
1176         icmp_reply(&icmp_param, skb);
1177         return SKB_NOT_DROPPED_YET;
1178
1179 out_err:
1180         __ICMP_INC_STATS(dev_net(skb_dst(skb)->dev), ICMP_MIB_INERRORS);
1181         return SKB_DROP_REASON_PKT_TOO_SMALL;
1182 }
1183
1184 static enum skb_drop_reason icmp_discard(struct sk_buff *skb)
1185 {
1186         /* pretend it was a success */
1187         return SKB_NOT_DROPPED_YET;
1188 }
1189
1190 /*
1191  *      Deal with incoming ICMP packets.
1192  */
1193 int icmp_rcv(struct sk_buff *skb)
1194 {
1195         enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
1196         struct rtable *rt = skb_rtable(skb);
1197         struct net *net = dev_net(rt->dst.dev);
1198         struct icmphdr *icmph;
1199
1200         if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
1201                 struct sec_path *sp = skb_sec_path(skb);
1202                 int nh;
1203
1204                 if (!(sp && sp->xvec[sp->len - 1]->props.flags &
1205                                  XFRM_STATE_ICMP)) {
1206                         reason = SKB_DROP_REASON_XFRM_POLICY;
1207                         goto drop;
1208                 }
1209
1210                 if (!pskb_may_pull(skb, sizeof(*icmph) + sizeof(struct iphdr)))
1211                         goto drop;
1212
1213                 nh = skb_network_offset(skb);
1214                 skb_set_network_header(skb, sizeof(*icmph));
1215
1216                 if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN,
1217                                                 skb)) {
1218                         reason = SKB_DROP_REASON_XFRM_POLICY;
1219                         goto drop;
1220                 }
1221
1222                 skb_set_network_header(skb, nh);
1223         }
1224
1225         __ICMP_INC_STATS(net, ICMP_MIB_INMSGS);
1226
1227         if (skb_checksum_simple_validate(skb))
1228                 goto csum_error;
1229
1230         if (!pskb_pull(skb, sizeof(*icmph)))
1231                 goto error;
1232
1233         icmph = icmp_hdr(skb);
1234
1235         ICMPMSGIN_INC_STATS(net, icmph->type);
1236
1237         /* Check for ICMP Extended Echo (PROBE) messages */
1238         if (icmph->type == ICMP_EXT_ECHO) {
1239                 /* We can't use icmp_pointers[].handler() because it is an array of
1240                  * size NR_ICMP_TYPES + 1 (19 elements) and PROBE has code 42.
1241                  */
1242                 reason = icmp_echo(skb);
1243                 goto reason_check;
1244         }
1245
1246         if (icmph->type == ICMP_EXT_ECHOREPLY) {
1247                 reason = ping_rcv(skb);
1248                 goto reason_check;
1249         }
1250
1251         /*
1252          *      18 is the highest 'known' ICMP type. Anything else is a mystery
1253          *
1254          *      RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
1255          *                discarded.
1256          */
1257         if (icmph->type > NR_ICMP_TYPES) {
1258                 reason = SKB_DROP_REASON_UNHANDLED_PROTO;
1259                 goto error;
1260         }
1261
1262         /*
1263          *      Parse the ICMP message
1264          */
1265
1266         if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) {
1267                 /*
1268                  *      RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be
1269                  *        silently ignored (we let user decide with a sysctl).
1270                  *      RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently
1271                  *        discarded if to broadcast/multicast.
1272                  */
1273                 if ((icmph->type == ICMP_ECHO ||
1274                      icmph->type == ICMP_TIMESTAMP) &&
1275                     READ_ONCE(net->ipv4.sysctl_icmp_echo_ignore_broadcasts)) {
1276                         reason = SKB_DROP_REASON_INVALID_PROTO;
1277                         goto error;
1278                 }
1279                 if (icmph->type != ICMP_ECHO &&
1280                     icmph->type != ICMP_TIMESTAMP &&
1281                     icmph->type != ICMP_ADDRESS &&
1282                     icmph->type != ICMP_ADDRESSREPLY) {
1283                         reason = SKB_DROP_REASON_INVALID_PROTO;
1284                         goto error;
1285                 }
1286         }
1287
1288         reason = icmp_pointers[icmph->type].handler(skb);
1289 reason_check:
1290         if (!reason)  {
1291                 consume_skb(skb);
1292                 return NET_RX_SUCCESS;
1293         }
1294
1295 drop:
1296         kfree_skb_reason(skb, reason);
1297         return NET_RX_DROP;
1298 csum_error:
1299         reason = SKB_DROP_REASON_ICMP_CSUM;
1300         __ICMP_INC_STATS(net, ICMP_MIB_CSUMERRORS);
1301 error:
1302         __ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
1303         goto drop;
1304 }
1305
1306 static bool ip_icmp_error_rfc4884_validate(const struct sk_buff *skb, int off)
1307 {
1308         struct icmp_extobj_hdr *objh, _objh;
1309         struct icmp_ext_hdr *exth, _exth;
1310         u16 olen;
1311
1312         exth = skb_header_pointer(skb, off, sizeof(_exth), &_exth);
1313         if (!exth)
1314                 return false;
1315         if (exth->version != 2)
1316                 return true;
1317
1318         if (exth->checksum &&
1319             csum_fold(skb_checksum(skb, off, skb->len - off, 0)))
1320                 return false;
1321
1322         off += sizeof(_exth);
1323         while (off < skb->len) {
1324                 objh = skb_header_pointer(skb, off, sizeof(_objh), &_objh);
1325                 if (!objh)
1326                         return false;
1327
1328                 olen = ntohs(objh->length);
1329                 if (olen < sizeof(_objh))
1330                         return false;
1331
1332                 off += olen;
1333                 if (off > skb->len)
1334                         return false;
1335         }
1336
1337         return true;
1338 }
1339
1340 void ip_icmp_error_rfc4884(const struct sk_buff *skb,
1341                            struct sock_ee_data_rfc4884 *out,
1342                            int thlen, int off)
1343 {
1344         int hlen;
1345
1346         /* original datagram headers: end of icmph to payload (skb->data) */
1347         hlen = -skb_transport_offset(skb) - thlen;
1348
1349         /* per rfc 4884: minimal datagram length of 128 bytes */
1350         if (off < 128 || off < hlen)
1351                 return;
1352
1353         /* kernel has stripped headers: return payload offset in bytes */
1354         off -= hlen;
1355         if (off + sizeof(struct icmp_ext_hdr) > skb->len)
1356                 return;
1357
1358         out->len = off;
1359
1360         if (!ip_icmp_error_rfc4884_validate(skb, off))
1361                 out->flags |= SO_EE_RFC4884_FLAG_INVALID;
1362 }
1363 EXPORT_SYMBOL_GPL(ip_icmp_error_rfc4884);
1364
1365 int icmp_err(struct sk_buff *skb, u32 info)
1366 {
1367         struct iphdr *iph = (struct iphdr *)skb->data;
1368         int offset = iph->ihl<<2;
1369         struct icmphdr *icmph = (struct icmphdr *)(skb->data + offset);
1370         int type = icmp_hdr(skb)->type;
1371         int code = icmp_hdr(skb)->code;
1372         struct net *net = dev_net(skb->dev);
1373
1374         /*
1375          * Use ping_err to handle all icmp errors except those
1376          * triggered by ICMP_ECHOREPLY which sent from kernel.
1377          */
1378         if (icmph->type != ICMP_ECHOREPLY) {
1379                 ping_err(skb, offset, info);
1380                 return 0;
1381         }
1382
1383         if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
1384                 ipv4_update_pmtu(skb, net, info, 0, IPPROTO_ICMP);
1385         else if (type == ICMP_REDIRECT)
1386                 ipv4_redirect(skb, net, 0, IPPROTO_ICMP);
1387
1388         return 0;
1389 }
1390
1391 /*
1392  *      This table is the definition of how we handle ICMP.
1393  */
1394 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = {
1395         [ICMP_ECHOREPLY] = {
1396                 .handler = ping_rcv,
1397         },
1398         [1] = {
1399                 .handler = icmp_discard,
1400                 .error = 1,
1401         },
1402         [2] = {
1403                 .handler = icmp_discard,
1404                 .error = 1,
1405         },
1406         [ICMP_DEST_UNREACH] = {
1407                 .handler = icmp_unreach,
1408                 .error = 1,
1409         },
1410         [ICMP_SOURCE_QUENCH] = {
1411                 .handler = icmp_unreach,
1412                 .error = 1,
1413         },
1414         [ICMP_REDIRECT] = {
1415                 .handler = icmp_redirect,
1416                 .error = 1,
1417         },
1418         [6] = {
1419                 .handler = icmp_discard,
1420                 .error = 1,
1421         },
1422         [7] = {
1423                 .handler = icmp_discard,
1424                 .error = 1,
1425         },
1426         [ICMP_ECHO] = {
1427                 .handler = icmp_echo,
1428         },
1429         [9] = {
1430                 .handler = icmp_discard,
1431                 .error = 1,
1432         },
1433         [10] = {
1434                 .handler = icmp_discard,
1435                 .error = 1,
1436         },
1437         [ICMP_TIME_EXCEEDED] = {
1438                 .handler = icmp_unreach,
1439                 .error = 1,
1440         },
1441         [ICMP_PARAMETERPROB] = {
1442                 .handler = icmp_unreach,
1443                 .error = 1,
1444         },
1445         [ICMP_TIMESTAMP] = {
1446                 .handler = icmp_timestamp,
1447         },
1448         [ICMP_TIMESTAMPREPLY] = {
1449                 .handler = icmp_discard,
1450         },
1451         [ICMP_INFO_REQUEST] = {
1452                 .handler = icmp_discard,
1453         },
1454         [ICMP_INFO_REPLY] = {
1455                 .handler = icmp_discard,
1456         },
1457         [ICMP_ADDRESS] = {
1458                 .handler = icmp_discard,
1459         },
1460         [ICMP_ADDRESSREPLY] = {
1461                 .handler = icmp_discard,
1462         },
1463 };
1464
1465 static int __net_init icmp_sk_init(struct net *net)
1466 {
1467         /* Control parameters for ECHO replies. */
1468         net->ipv4.sysctl_icmp_echo_ignore_all = 0;
1469         net->ipv4.sysctl_icmp_echo_enable_probe = 0;
1470         net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1;
1471
1472         /* Control parameter - ignore bogus broadcast responses? */
1473         net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1;
1474
1475         /*
1476          *      Configurable global rate limit.
1477          *
1478          *      ratelimit defines tokens/packet consumed for dst->rate_token
1479          *      bucket ratemask defines which icmp types are ratelimited by
1480          *      setting it's bit position.
1481          *
1482          *      default:
1483          *      dest unreachable (3), source quench (4),
1484          *      time exceeded (11), parameter problem (12)
1485          */
1486
1487         net->ipv4.sysctl_icmp_ratelimit = 1 * HZ;
1488         net->ipv4.sysctl_icmp_ratemask = 0x1818;
1489         net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0;
1490
1491         return 0;
1492 }
1493
1494 static struct pernet_operations __net_initdata icmp_sk_ops = {
1495        .init = icmp_sk_init,
1496 };
1497
1498 int __init icmp_init(void)
1499 {
1500         int err, i;
1501
1502         for_each_possible_cpu(i) {
1503                 struct sock *sk;
1504
1505                 err = inet_ctl_sock_create(&sk, PF_INET,
1506                                            SOCK_RAW, IPPROTO_ICMP, &init_net);
1507                 if (err < 0)
1508                         return err;
1509
1510                 per_cpu(ipv4_icmp_sk, i) = sk;
1511
1512                 /* Enough space for 2 64K ICMP packets, including
1513                  * sk_buff/skb_shared_info struct overhead.
1514                  */
1515                 sk->sk_sndbuf = 2 * SKB_TRUESIZE(64 * 1024);
1516
1517                 /*
1518                  * Speedup sock_wfree()
1519                  */
1520                 sock_set_flag(sk, SOCK_USE_WRITE_QUEUE);
1521                 inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT;
1522         }
1523         return register_pernet_subsys(&icmp_sk_ops);
1524 }