net/ipv4/icmp.c

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This source file includes following definitions.
icmp_sk
icmp_xmit_lock
icmp_xmit_unlock
icmp_global_allow
icmpv4_mask_allow
icmpv4_global_allow
icmpv4_xrlim_allow
icmp_out_count
icmp_glue_bits
icmp_push_reply
icmp_reply
icmp_route_lookup
__icmp_send
icmp_socket_deliver
icmp_tag_validation
icmp_unreach
icmp_redirect
icmp_echo
icmp_timestamp
icmp_discard
icmp_rcv
icmp_err
icmp_sk_exit
icmp_sk_init
icmp_init
   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *      NET3:   Implementation of the ICMP protocol layer.
   4  *
   5  *              Alan Cox, <alan@lxorguk.ukuu.org.uk>
   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 
  96 /*
  97  *      Build xmit assembly blocks
  98  */
  99 
 100 struct icmp_bxm {
 101         struct sk_buff *skb;
 102         int offset;
 103         int data_len;
 104 
 105         struct {
 106                 struct icmphdr icmph;
 107                 __be32         times[3];
 108         } data;
 109         int head_len;
 110         struct ip_options_data replyopts;
 111 };
 112 
 113 /* An array of errno for error messages from dest unreach. */
 114 /* RFC 1122: 3.2.2.1 States that NET_UNREACH, HOST_UNREACH and SR_FAILED MUST be considered 'transient errs'. */
 115 
 116 const struct icmp_err icmp_err_convert[] = {
 117         {
 118                 .errno = ENETUNREACH,   /* ICMP_NET_UNREACH */
 119                 .fatal = 0,
 120         },
 121         {
 122                 .errno = EHOSTUNREACH,  /* ICMP_HOST_UNREACH */
 123                 .fatal = 0,
 124         },
 125         {
 126                 .errno = ENOPROTOOPT    /* ICMP_PROT_UNREACH */,
 127                 .fatal = 1,
 128         },
 129         {
 130                 .errno = ECONNREFUSED,  /* ICMP_PORT_UNREACH */
 131                 .fatal = 1,
 132         },
 133         {
 134                 .errno = EMSGSIZE,      /* ICMP_FRAG_NEEDED */
 135                 .fatal = 0,
 136         },
 137         {
 138                 .errno = EOPNOTSUPP,    /* ICMP_SR_FAILED */
 139                 .fatal = 0,
 140         },
 141         {
 142                 .errno = ENETUNREACH,   /* ICMP_NET_UNKNOWN */
 143                 .fatal = 1,
 144         },
 145         {
 146                 .errno = EHOSTDOWN,     /* ICMP_HOST_UNKNOWN */
 147                 .fatal = 1,
 148         },
 149         {
 150                 .errno = ENONET,        /* ICMP_HOST_ISOLATED */
 151                 .fatal = 1,
 152         },
 153         {
 154                 .errno = ENETUNREACH,   /* ICMP_NET_ANO */
 155                 .fatal = 1,
 156         },
 157         {
 158                 .errno = EHOSTUNREACH,  /* ICMP_HOST_ANO */
 159                 .fatal = 1,
 160         },
 161         {
 162                 .errno = ENETUNREACH,   /* ICMP_NET_UNR_TOS */
 163                 .fatal = 0,
 164         },
 165         {
 166                 .errno = EHOSTUNREACH,  /* ICMP_HOST_UNR_TOS */
 167                 .fatal = 0,
 168         },
 169         {
 170                 .errno = EHOSTUNREACH,  /* ICMP_PKT_FILTERED */
 171                 .fatal = 1,
 172         },
 173         {
 174                 .errno = EHOSTUNREACH,  /* ICMP_PREC_VIOLATION */
 175                 .fatal = 1,
 176         },
 177         {
 178                 .errno = EHOSTUNREACH,  /* ICMP_PREC_CUTOFF */
 179                 .fatal = 1,
 180         },
 181 };
 182 EXPORT_SYMBOL(icmp_err_convert);
 183 
 184 /*
 185  *      ICMP control array. This specifies what to do with each ICMP.
 186  */
 187 
 188 struct icmp_control {
 189         bool (*handler)(struct sk_buff *skb);
 190         short   error;          /* This ICMP is classed as an error message */
 191 };
 192 
 193 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES+1];
 194 
 195 /*
 196  *      The ICMP socket(s). This is the most convenient way to flow control
 197  *      our ICMP output as well as maintain a clean interface throughout
 198  *      all layers. All Socketless IP sends will soon be gone.
 199  *
 200  *      On SMP we have one ICMP socket per-cpu.
 201  */
 202 static struct sock *icmp_sk(struct net *net)
 203 {
 204         return this_cpu_read(*net->ipv4.icmp_sk);
 205 }
 206 
 207 /* Called with BH disabled */
 208 static inline struct sock *icmp_xmit_lock(struct net *net)
 209 {
 210         struct sock *sk;
 211 
 212         sk = icmp_sk(net);
 213 
 214         if (unlikely(!spin_trylock(&sk->sk_lock.slock))) {
 215                 /* This can happen if the output path signals a
 216                  * dst_link_failure() for an outgoing ICMP packet.
 217                  */
 218                 return NULL;
 219         }
 220         return sk;
 221 }
 222 
 223 static inline void icmp_xmit_unlock(struct sock *sk)
 224 {
 225         spin_unlock(&sk->sk_lock.slock);
 226 }
 227 
 228 int sysctl_icmp_msgs_per_sec __read_mostly = 1000;
 229 int sysctl_icmp_msgs_burst __read_mostly = 50;
 230 
 231 static struct {
 232         spinlock_t      lock;
 233         u32             credit;
 234         u32             stamp;
 235 } icmp_global = {
 236         .lock           = __SPIN_LOCK_UNLOCKED(icmp_global.lock),
 237 };
 238 
 239 /**
 240  * icmp_global_allow - Are we allowed to send one more ICMP message ?
 241  *
 242  * Uses a token bucket to limit our ICMP messages to sysctl_icmp_msgs_per_sec.
 243  * Returns false if we reached the limit and can not send another packet.
 244  * Note: called with BH disabled
 245  */
 246 bool icmp_global_allow(void)
 247 {
 248         u32 credit, delta, incr = 0, now = (u32)jiffies;
 249         bool rc = false;
 250 
 251         /* Check if token bucket is empty and cannot be refilled
 252          * without taking the spinlock. The READ_ONCE() are paired
 253          * with the following WRITE_ONCE() in this same function.
 254          */
 255         if (!READ_ONCE(icmp_global.credit)) {
 256                 delta = min_t(u32, now - READ_ONCE(icmp_global.stamp), HZ);
 257                 if (delta < HZ / 50)
 258                         return false;
 259         }
 260 
 261         spin_lock(&icmp_global.lock);
 262         delta = min_t(u32, now - icmp_global.stamp, HZ);
 263         if (delta >= HZ / 50) {
 264                 incr = sysctl_icmp_msgs_per_sec * delta / HZ ;
 265                 if (incr)
 266                         WRITE_ONCE(icmp_global.stamp, now);
 267         }
 268         credit = min_t(u32, icmp_global.credit + incr, sysctl_icmp_msgs_burst);
 269         if (credit) {
 270                 credit--;
 271                 rc = true;
 272         }
 273         WRITE_ONCE(icmp_global.credit, credit);
 274         spin_unlock(&icmp_global.lock);
 275         return rc;
 276 }
 277 EXPORT_SYMBOL(icmp_global_allow);
 278 
 279 static bool icmpv4_mask_allow(struct net *net, int type, int code)
 280 {
 281         if (type > NR_ICMP_TYPES)
 282                 return true;
 283 
 284         /* Don't limit PMTU discovery. */
 285         if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 286                 return true;
 287 
 288         /* Limit if icmp type is enabled in ratemask. */
 289         if (!((1 << type) & net->ipv4.sysctl_icmp_ratemask))
 290                 return true;
 291 
 292         return false;
 293 }
 294 
 295 static bool icmpv4_global_allow(struct net *net, int type, int code)
 296 {
 297         if (icmpv4_mask_allow(net, type, code))
 298                 return true;
 299 
 300         if (icmp_global_allow())
 301                 return true;
 302 
 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, net->ipv4.sysctl_icmp_ratelimit);
 328         if (peer)
 329                 inet_putpeer(peer);
 330 out:
 331         return rc;
 332 }
 333 
 334 /*
 335  *      Maintain the counters used in the SNMP statistics for outgoing ICMP
 336  */
 337 void icmp_out_count(struct net *net, unsigned char type)
 338 {
 339         ICMPMSGOUT_INC_STATS(net, type);
 340         ICMP_INC_STATS(net, ICMP_MIB_OUTMSGS);
 341 }
 342 
 343 /*
 344  *      Checksum each fragment, and on the first include the headers and final
 345  *      checksum.
 346  */
 347 static int icmp_glue_bits(void *from, char *to, int offset, int len, int odd,
 348                           struct sk_buff *skb)
 349 {
 350         struct icmp_bxm *icmp_param = (struct icmp_bxm *)from;
 351         __wsum csum;
 352 
 353         csum = skb_copy_and_csum_bits(icmp_param->skb,
 354                                       icmp_param->offset + offset,
 355                                       to, len, 0);
 356 
 357         skb->csum = csum_block_add(skb->csum, csum, odd);
 358         if (icmp_pointers[icmp_param->data.icmph.type].error)
 359                 nf_ct_attach(skb, icmp_param->skb);
 360         return 0;
 361 }
 362 
 363 static void icmp_push_reply(struct icmp_bxm *icmp_param,
 364                             struct flowi4 *fl4,
 365                             struct ipcm_cookie *ipc, struct rtable **rt)
 366 {
 367         struct sock *sk;
 368         struct sk_buff *skb;
 369 
 370         sk = icmp_sk(dev_net((*rt)->dst.dev));
 371         if (ip_append_data(sk, fl4, icmp_glue_bits, icmp_param,
 372                            icmp_param->data_len+icmp_param->head_len,
 373                            icmp_param->head_len,
 374                            ipc, rt, MSG_DONTWAIT) < 0) {
 375                 __ICMP_INC_STATS(sock_net(sk), ICMP_MIB_OUTERRORS);
 376                 ip_flush_pending_frames(sk);
 377         } else if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {
 378                 struct icmphdr *icmph = icmp_hdr(skb);
 379                 __wsum csum = 0;
 380                 struct sk_buff *skb1;
 381 
 382                 skb_queue_walk(&sk->sk_write_queue, skb1) {
 383                         csum = csum_add(csum, skb1->csum);
 384                 }
 385                 csum = csum_partial_copy_nocheck((void *)&icmp_param->data,
 386                                                  (char *)icmph,
 387                                                  icmp_param->head_len, csum);
 388                 icmph->checksum = csum_fold(csum);
 389                 skb->ip_summed = CHECKSUM_NONE;
 390                 ip_push_pending_frames(sk, fl4);
 391         }
 392 }
 393 
 394 /*
 395  *      Driving logic for building and sending ICMP messages.
 396  */
 397 
 398 static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
 399 {
 400         struct ipcm_cookie ipc;
 401         struct rtable *rt = skb_rtable(skb);
 402         struct net *net = dev_net(rt->dst.dev);
 403         struct flowi4 fl4;
 404         struct sock *sk;
 405         struct inet_sock *inet;
 406         __be32 daddr, saddr;
 407         u32 mark = IP4_REPLY_MARK(net, skb->mark);
 408         int type = icmp_param->data.icmph.type;
 409         int code = icmp_param->data.icmph.code;
 410 
 411         if (ip_options_echo(net, &icmp_param->replyopts.opt.opt, skb))
 412                 return;
 413 
 414         /* Needed by both icmp_global_allow and icmp_xmit_lock */
 415         local_bh_disable();
 416 
 417         /* global icmp_msgs_per_sec */
 418         if (!icmpv4_global_allow(net, type, code))
 419                 goto out_bh_enable;
 420 
 421         sk = icmp_xmit_lock(net);
 422         if (!sk)
 423                 goto out_bh_enable;
 424         inet = inet_sk(sk);
 425 
 426         icmp_param->data.icmph.checksum = 0;
 427 
 428         ipcm_init(&ipc);
 429         inet->tos = ip_hdr(skb)->tos;
 430         sk->sk_mark = mark;
 431         daddr = ipc.addr = ip_hdr(skb)->saddr;
 432         saddr = fib_compute_spec_dst(skb);
 433 
 434         if (icmp_param->replyopts.opt.opt.optlen) {
 435                 ipc.opt = &icmp_param->replyopts.opt;
 436                 if (ipc.opt->opt.srr)
 437                         daddr = icmp_param->replyopts.opt.opt.faddr;
 438         }
 439         memset(&fl4, 0, sizeof(fl4));
 440         fl4.daddr = daddr;
 441         fl4.saddr = saddr;
 442         fl4.flowi4_mark = mark;
 443         fl4.flowi4_uid = sock_net_uid(net, NULL);
 444         fl4.flowi4_tos = RT_TOS(ip_hdr(skb)->tos);
 445         fl4.flowi4_proto = IPPROTO_ICMP;
 446         fl4.flowi4_oif = l3mdev_master_ifindex(skb->dev);
 447         security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
 448         rt = ip_route_output_key(net, &fl4);
 449         if (IS_ERR(rt))
 450                 goto out_unlock;
 451         if (icmpv4_xrlim_allow(net, rt, &fl4, type, code))
 452                 icmp_push_reply(icmp_param, &fl4, &ipc, &rt);
 453         ip_rt_put(rt);
 454 out_unlock:
 455         icmp_xmit_unlock(sk);
 456 out_bh_enable:
 457         local_bh_enable();
 458 }
 459 
 460 static struct rtable *icmp_route_lookup(struct net *net,
 461                                         struct flowi4 *fl4,
 462                                         struct sk_buff *skb_in,
 463                                         const struct iphdr *iph,
 464                                         __be32 saddr, u8 tos, u32 mark,
 465                                         int type, int code,
 466                                         struct icmp_bxm *param)
 467 {
 468         struct rtable *rt, *rt2;
 469         struct flowi4 fl4_dec;
 470         int err;
 471 
 472         memset(fl4, 0, sizeof(*fl4));
 473         fl4->daddr = (param->replyopts.opt.opt.srr ?
 474                       param->replyopts.opt.opt.faddr : iph->saddr);
 475         fl4->saddr = saddr;
 476         fl4->flowi4_mark = mark;
 477         fl4->flowi4_uid = sock_net_uid(net, NULL);
 478         fl4->flowi4_tos = RT_TOS(tos);
 479         fl4->flowi4_proto = IPPROTO_ICMP;
 480         fl4->fl4_icmp_type = type;
 481         fl4->fl4_icmp_code = code;
 482         fl4->flowi4_oif = l3mdev_master_ifindex(skb_dst(skb_in)->dev);
 483 
 484         security_skb_classify_flow(skb_in, flowi4_to_flowi(fl4));
 485         rt = ip_route_output_key_hash(net, fl4, skb_in);
 486         if (IS_ERR(rt))
 487                 return rt;
 488 
 489         /* No need to clone since we're just using its address. */
 490         rt2 = rt;
 491 
 492         rt = (struct rtable *) xfrm_lookup(net, &rt->dst,
 493                                            flowi4_to_flowi(fl4), NULL, 0);
 494         if (!IS_ERR(rt)) {
 495                 if (rt != rt2)
 496                         return rt;
 497         } else if (PTR_ERR(rt) == -EPERM) {
 498                 rt = NULL;
 499         } else
 500                 return rt;
 501 
 502         err = xfrm_decode_session_reverse(skb_in, flowi4_to_flowi(&fl4_dec), AF_INET);
 503         if (err)
 504                 goto relookup_failed;
 505 
 506         if (inet_addr_type_dev_table(net, skb_dst(skb_in)->dev,
 507                                      fl4_dec.saddr) == RTN_LOCAL) {
 508                 rt2 = __ip_route_output_key(net, &fl4_dec);
 509                 if (IS_ERR(rt2))
 510                         err = PTR_ERR(rt2);
 511         } else {
 512                 struct flowi4 fl4_2 = {};
 513                 unsigned long orefdst;
 514 
 515                 fl4_2.daddr = fl4_dec.saddr;
 516                 rt2 = ip_route_output_key(net, &fl4_2);
 517                 if (IS_ERR(rt2)) {
 518                         err = PTR_ERR(rt2);
 519                         goto relookup_failed;
 520                 }
 521                 /* Ugh! */
 522                 orefdst = skb_in->_skb_refdst; /* save old refdst */
 523                 skb_dst_set(skb_in, NULL);
 524                 err = ip_route_input(skb_in, fl4_dec.daddr, fl4_dec.saddr,
 525                                      RT_TOS(tos), rt2->dst.dev);
 526 
 527                 dst_release(&rt2->dst);
 528                 rt2 = skb_rtable(skb_in);
 529                 skb_in->_skb_refdst = orefdst; /* restore old refdst */
 530         }
 531 
 532         if (err)
 533                 goto relookup_failed;
 534 
 535         rt2 = (struct rtable *) xfrm_lookup(net, &rt2->dst,
 536                                             flowi4_to_flowi(&fl4_dec), NULL,
 537                                             XFRM_LOOKUP_ICMP);
 538         if (!IS_ERR(rt2)) {
 539                 dst_release(&rt->dst);
 540                 memcpy(fl4, &fl4_dec, sizeof(*fl4));
 541                 rt = rt2;
 542         } else if (PTR_ERR(rt2) == -EPERM) {
 543                 if (rt)
 544                         dst_release(&rt->dst);
 545                 return rt2;
 546         } else {
 547                 err = PTR_ERR(rt2);
 548                 goto relookup_failed;
 549         }
 550         return rt;
 551 
 552 relookup_failed:
 553         if (rt)
 554                 return rt;
 555         return ERR_PTR(err);
 556 }
 557 
 558 /*
 559  *      Send an ICMP message in response to a situation
 560  *
 561  *      RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header.
 562  *                MAY send more (we do).
 563  *                      MUST NOT change this header information.
 564  *                      MUST NOT reply to a multicast/broadcast IP address.
 565  *                      MUST NOT reply to a multicast/broadcast MAC address.
 566  *                      MUST reply to only the first fragment.
 567  */
 568 
 569 void __icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info,
 570                  const struct ip_options *opt)
 571 {
 572         struct iphdr *iph;
 573         int room;
 574         struct icmp_bxm icmp_param;
 575         struct rtable *rt = skb_rtable(skb_in);
 576         struct ipcm_cookie ipc;
 577         struct flowi4 fl4;
 578         __be32 saddr;
 579         u8  tos;
 580         u32 mark;
 581         struct net *net;
 582         struct sock *sk;
 583 
 584         if (!rt)
 585                 goto out;
 586 
 587         if (rt->dst.dev)
 588                 net = dev_net(rt->dst.dev);
 589         else if (skb_in->dev)
 590                 net = dev_net(skb_in->dev);
 591         else
 592                 goto out;
 593 
 594         /*
 595          *      Find the original header. It is expected to be valid, of course.
 596          *      Check this, icmp_send is called from the most obscure devices
 597          *      sometimes.
 598          */
 599         iph = ip_hdr(skb_in);
 600 
 601         if ((u8 *)iph < skb_in->head ||
 602             (skb_network_header(skb_in) + sizeof(*iph)) >
 603             skb_tail_pointer(skb_in))
 604                 goto out;
 605 
 606         /*
 607          *      No replies to physical multicast/broadcast
 608          */
 609         if (skb_in->pkt_type != PACKET_HOST)
 610                 goto out;
 611 
 612         /*
 613          *      Now check at the protocol level
 614          */
 615         if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
 616                 goto out;
 617 
 618         /*
 619          *      Only reply to fragment 0. We byte re-order the constant
 620          *      mask for efficiency.
 621          */
 622         if (iph->frag_off & htons(IP_OFFSET))
 623                 goto out;
 624 
 625         /*
 626          *      If we send an ICMP error to an ICMP error a mess would result..
 627          */
 628         if (icmp_pointers[type].error) {
 629                 /*
 630                  *      We are an error, check if we are replying to an
 631                  *      ICMP error
 632                  */
 633                 if (iph->protocol == IPPROTO_ICMP) {
 634                         u8 _inner_type, *itp;
 635 
 636                         itp = skb_header_pointer(skb_in,
 637                                                  skb_network_header(skb_in) +
 638                                                  (iph->ihl << 2) +
 639                                                  offsetof(struct icmphdr,
 640                                                           type) -
 641                                                  skb_in->data,
 642                                                  sizeof(_inner_type),
 643                                                  &_inner_type);
 644                         if (!itp)
 645                                 goto out;
 646 
 647                         /*
 648                          *      Assume any unknown ICMP type is an error. This
 649                          *      isn't specified by the RFC, but think about it..
 650                          */
 651                         if (*itp > NR_ICMP_TYPES ||
 652                             icmp_pointers[*itp].error)
 653                                 goto out;
 654                 }
 655         }
 656 
 657         /* Needed by both icmp_global_allow and icmp_xmit_lock */
 658         local_bh_disable();
 659 
 660         /* Check global sysctl_icmp_msgs_per_sec ratelimit, unless
 661          * incoming dev is loopback.  If outgoing dev change to not be
 662          * loopback, then peer ratelimit still work (in icmpv4_xrlim_allow)
 663          */
 664         if (!(skb_in->dev && (skb_in->dev->flags&IFF_LOOPBACK)) &&
 665               !icmpv4_global_allow(net, type, code))
 666                 goto out_bh_enable;
 667 
 668         sk = icmp_xmit_lock(net);
 669         if (!sk)
 670                 goto out_bh_enable;
 671 
 672         /*
 673          *      Construct source address and options.
 674          */
 675 
 676         saddr = iph->daddr;
 677         if (!(rt->rt_flags & RTCF_LOCAL)) {
 678                 struct net_device *dev = NULL;
 679 
 680                 rcu_read_lock();
 681                 if (rt_is_input_route(rt) &&
 682                     net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr)
 683                         dev = dev_get_by_index_rcu(net, inet_iif(skb_in));
 684 
 685                 if (dev)
 686                         saddr = inet_select_addr(dev, 0, RT_SCOPE_LINK);
 687                 else
 688                         saddr = 0;
 689                 rcu_read_unlock();
 690         }
 691 
 692         tos = icmp_pointers[type].error ? ((iph->tos & IPTOS_TOS_MASK) |
 693                                            IPTOS_PREC_INTERNETCONTROL) :
 694                                           iph->tos;
 695         mark = IP4_REPLY_MARK(net, skb_in->mark);
 696 
 697         if (__ip_options_echo(net, &icmp_param.replyopts.opt.opt, skb_in, opt))
 698                 goto out_unlock;
 699 
 700 
 701         /*
 702          *      Prepare data for ICMP header.
 703          */
 704 
 705         icmp_param.data.icmph.type       = type;
 706         icmp_param.data.icmph.code       = code;
 707         icmp_param.data.icmph.un.gateway = info;
 708         icmp_param.data.icmph.checksum   = 0;
 709         icmp_param.skb    = skb_in;
 710         icmp_param.offset = skb_network_offset(skb_in);
 711         inet_sk(sk)->tos = tos;
 712         sk->sk_mark = mark;
 713         ipcm_init(&ipc);
 714         ipc.addr = iph->saddr;
 715         ipc.opt = &icmp_param.replyopts.opt;
 716 
 717         rt = icmp_route_lookup(net, &fl4, skb_in, iph, saddr, tos, mark,
 718                                type, code, &icmp_param);
 719         if (IS_ERR(rt))
 720                 goto out_unlock;
 721 
 722         /* peer icmp_ratelimit */
 723         if (!icmpv4_xrlim_allow(net, rt, &fl4, type, code))
 724                 goto ende;
 725 
 726         /* RFC says return as much as we can without exceeding 576 bytes. */
 727 
 728         room = dst_mtu(&rt->dst);
 729         if (room > 576)
 730                 room = 576;
 731         room -= sizeof(struct iphdr) + icmp_param.replyopts.opt.opt.optlen;
 732         room -= sizeof(struct icmphdr);
 733 
 734         icmp_param.data_len = skb_in->len - icmp_param.offset;
 735         if (icmp_param.data_len > room)
 736                 icmp_param.data_len = room;
 737         icmp_param.head_len = sizeof(struct icmphdr);
 738 
 739         icmp_push_reply(&icmp_param, &fl4, &ipc, &rt);
 740 ende:
 741         ip_rt_put(rt);
 742 out_unlock:
 743         icmp_xmit_unlock(sk);
 744 out_bh_enable:
 745         local_bh_enable();
 746 out:;
 747 }
 748 EXPORT_SYMBOL(__icmp_send);
 749 
 750 
 751 static void icmp_socket_deliver(struct sk_buff *skb, u32 info)
 752 {
 753         const struct iphdr *iph = (const struct iphdr *) skb->data;
 754         const struct net_protocol *ipprot;
 755         int protocol = iph->protocol;
 756 
 757         /* Checkin full IP header plus 8 bytes of protocol to
 758          * avoid additional coding at protocol handlers.
 759          */
 760         if (!pskb_may_pull(skb, iph->ihl * 4 + 8)) {
 761                 __ICMP_INC_STATS(dev_net(skb->dev), ICMP_MIB_INERRORS);
 762                 return;
 763         }
 764 
 765         raw_icmp_error(skb, protocol, info);
 766 
 767         ipprot = rcu_dereference(inet_protos[protocol]);
 768         if (ipprot && ipprot->err_handler)
 769                 ipprot->err_handler(skb, info);
 770 }
 771 
 772 static bool icmp_tag_validation(int proto)
 773 {
 774         bool ok;
 775 
 776         rcu_read_lock();
 777         ok = rcu_dereference(inet_protos[proto])->icmp_strict_tag_validation;
 778         rcu_read_unlock();
 779         return ok;
 780 }
 781 
 782 /*
 783  *      Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEEDED, ICMP_QUENCH, and
 784  *      ICMP_PARAMETERPROB.
 785  */
 786 
 787 static bool icmp_unreach(struct sk_buff *skb)
 788 {
 789         const struct iphdr *iph;
 790         struct icmphdr *icmph;
 791         struct net *net;
 792         u32 info = 0;
 793 
 794         net = dev_net(skb_dst(skb)->dev);
 795 
 796         /*
 797          *      Incomplete header ?
 798          *      Only checks for the IP header, there should be an
 799          *      additional check for longer headers in upper levels.
 800          */
 801 
 802         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
 803                 goto out_err;
 804 
 805         icmph = icmp_hdr(skb);
 806         iph   = (const struct iphdr *)skb->data;
 807 
 808         if (iph->ihl < 5) /* Mangled header, drop. */
 809                 goto out_err;
 810 
 811         switch (icmph->type) {
 812         case ICMP_DEST_UNREACH:
 813                 switch (icmph->code & 15) {
 814                 case ICMP_NET_UNREACH:
 815                 case ICMP_HOST_UNREACH:
 816                 case ICMP_PROT_UNREACH:
 817                 case ICMP_PORT_UNREACH:
 818                         break;
 819                 case ICMP_FRAG_NEEDED:
 820                         /* for documentation of the ip_no_pmtu_disc
 821                          * values please see
 822                          * Documentation/networking/ip-sysctl.txt
 823                          */
 824                         switch (net->ipv4.sysctl_ip_no_pmtu_disc) {
 825                         default:
 826                                 net_dbg_ratelimited("%pI4: fragmentation needed and DF set\n",
 827                                                     &iph->daddr);
 828                                 break;
 829                         case 2:
 830                                 goto out;
 831                         case 3:
 832                                 if (!icmp_tag_validation(iph->protocol))
 833                                         goto out;
 834                                 /* fall through */
 835                         case 0:
 836                                 info = ntohs(icmph->un.frag.mtu);
 837                         }
 838                         break;
 839                 case ICMP_SR_FAILED:
 840                         net_dbg_ratelimited("%pI4: Source Route Failed\n",
 841                                             &iph->daddr);
 842                         break;
 843                 default:
 844                         break;
 845                 }
 846                 if (icmph->code > NR_ICMP_UNREACH)
 847                         goto out;
 848                 break;
 849         case ICMP_PARAMETERPROB:
 850                 info = ntohl(icmph->un.gateway) >> 24;
 851                 break;
 852         case ICMP_TIME_EXCEEDED:
 853                 __ICMP_INC_STATS(net, ICMP_MIB_INTIMEEXCDS);
 854                 if (icmph->code == ICMP_EXC_FRAGTIME)
 855                         goto out;
 856                 break;
 857         }
 858 
 859         /*
 860          *      Throw it at our lower layers
 861          *
 862          *      RFC 1122: 3.2.2 MUST extract the protocol ID from the passed
 863          *                header.
 864          *      RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the
 865          *                transport layer.
 866          *      RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to
 867          *                transport layer.
 868          */
 869 
 870         /*
 871          *      Check the other end isn't violating RFC 1122. Some routers send
 872          *      bogus responses to broadcast frames. If you see this message
 873          *      first check your netmask matches at both ends, if it does then
 874          *      get the other vendor to fix their kit.
 875          */
 876 
 877         if (!net->ipv4.sysctl_icmp_ignore_bogus_error_responses &&
 878             inet_addr_type_dev_table(net, skb->dev, iph->daddr) == RTN_BROADCAST) {
 879                 net_warn_ratelimited("%pI4 sent an invalid ICMP type %u, code %u error to a broadcast: %pI4 on %s\n",
 880                                      &ip_hdr(skb)->saddr,
 881                                      icmph->type, icmph->code,
 882                                      &iph->daddr, skb->dev->name);
 883                 goto out;
 884         }
 885 
 886         icmp_socket_deliver(skb, info);
 887 
 888 out:
 889         return true;
 890 out_err:
 891         __ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
 892         return false;
 893 }
 894 
 895 
 896 /*
 897  *      Handle ICMP_REDIRECT.
 898  */
 899 
 900 static bool icmp_redirect(struct sk_buff *skb)
 901 {
 902         if (skb->len < sizeof(struct iphdr)) {
 903                 __ICMP_INC_STATS(dev_net(skb->dev), ICMP_MIB_INERRORS);
 904                 return false;
 905         }
 906 
 907         if (!pskb_may_pull(skb, sizeof(struct iphdr))) {
 908                 /* there aught to be a stat */
 909                 return false;
 910         }
 911 
 912         icmp_socket_deliver(skb, ntohl(icmp_hdr(skb)->un.gateway));
 913         return true;
 914 }
 915 
 916 /*
 917  *      Handle ICMP_ECHO ("ping") requests.
 918  *
 919  *      RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo
 920  *                requests.
 921  *      RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be
 922  *                included in the reply.
 923  *      RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring
 924  *                echo requests, MUST have default=NOT.
 925  *      See also WRT handling of options once they are done and working.
 926  */
 927 
 928 static bool icmp_echo(struct sk_buff *skb)
 929 {
 930         struct net *net;
 931 
 932         net = dev_net(skb_dst(skb)->dev);
 933         if (!net->ipv4.sysctl_icmp_echo_ignore_all) {
 934                 struct icmp_bxm icmp_param;
 935 
 936                 icmp_param.data.icmph      = *icmp_hdr(skb);
 937                 icmp_param.data.icmph.type = ICMP_ECHOREPLY;
 938                 icmp_param.skb             = skb;
 939                 icmp_param.offset          = 0;
 940                 icmp_param.data_len        = skb->len;
 941                 icmp_param.head_len        = sizeof(struct icmphdr);
 942                 icmp_reply(&icmp_param, skb);
 943         }
 944         /* should there be an ICMP stat for ignored echos? */
 945         return true;
 946 }
 947 
 948 /*
 949  *      Handle ICMP Timestamp requests.
 950  *      RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests.
 951  *                SHOULD be in the kernel for minimum random latency.
 952  *                MUST be accurate to a few minutes.
 953  *                MUST be updated at least at 15Hz.
 954  */
 955 static bool icmp_timestamp(struct sk_buff *skb)
 956 {
 957         struct icmp_bxm icmp_param;
 958         /*
 959          *      Too short.
 960          */
 961         if (skb->len < 4)
 962                 goto out_err;
 963 
 964         /*
 965          *      Fill in the current time as ms since midnight UT:
 966          */
 967         icmp_param.data.times[1] = inet_current_timestamp();
 968         icmp_param.data.times[2] = icmp_param.data.times[1];
 969 
 970         BUG_ON(skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4));
 971 
 972         icmp_param.data.icmph      = *icmp_hdr(skb);
 973         icmp_param.data.icmph.type = ICMP_TIMESTAMPREPLY;
 974         icmp_param.data.icmph.code = 0;
 975         icmp_param.skb             = skb;
 976         icmp_param.offset          = 0;
 977         icmp_param.data_len        = 0;
 978         icmp_param.head_len        = sizeof(struct icmphdr) + 12;
 979         icmp_reply(&icmp_param, skb);
 980         return true;
 981 
 982 out_err:
 983         __ICMP_INC_STATS(dev_net(skb_dst(skb)->dev), ICMP_MIB_INERRORS);
 984         return false;
 985 }
 986 
 987 static bool icmp_discard(struct sk_buff *skb)
 988 {
 989         /* pretend it was a success */
 990         return true;
 991 }
 992 
 993 /*
 994  *      Deal with incoming ICMP packets.
 995  */
 996 int icmp_rcv(struct sk_buff *skb)
 997 {
 998         struct icmphdr *icmph;
 999         struct rtable *rt = skb_rtable(skb);
1000         struct net *net = dev_net(rt->dst.dev);
1001         bool success;
1002 
1003         if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
1004                 struct sec_path *sp = skb_sec_path(skb);
1005                 int nh;
1006 
1007                 if (!(sp && sp->xvec[sp->len - 1]->props.flags &
1008                                  XFRM_STATE_ICMP))
1009                         goto drop;
1010 
1011                 if (!pskb_may_pull(skb, sizeof(*icmph) + sizeof(struct iphdr)))
1012                         goto drop;
1013 
1014                 nh = skb_network_offset(skb);
1015                 skb_set_network_header(skb, sizeof(*icmph));
1016 
1017                 if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN, skb))
1018                         goto drop;
1019 
1020                 skb_set_network_header(skb, nh);
1021         }
1022 
1023         __ICMP_INC_STATS(net, ICMP_MIB_INMSGS);
1024 
1025         if (skb_checksum_simple_validate(skb))
1026                 goto csum_error;
1027 
1028         if (!pskb_pull(skb, sizeof(*icmph)))
1029                 goto error;
1030 
1031         icmph = icmp_hdr(skb);
1032 
1033         ICMPMSGIN_INC_STATS(net, icmph->type);
1034         /*
1035          *      18 is the highest 'known' ICMP type. Anything else is a mystery
1036          *
1037          *      RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
1038          *                discarded.
1039          */
1040         if (icmph->type > NR_ICMP_TYPES)
1041                 goto error;
1042 
1043 
1044         /*
1045          *      Parse the ICMP message
1046          */
1047 
1048         if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) {
1049                 /*
1050                  *      RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be
1051                  *        silently ignored (we let user decide with a sysctl).
1052                  *      RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently
1053                  *        discarded if to broadcast/multicast.
1054                  */
1055                 if ((icmph->type == ICMP_ECHO ||
1056                      icmph->type == ICMP_TIMESTAMP) &&
1057                     net->ipv4.sysctl_icmp_echo_ignore_broadcasts) {
1058                         goto error;
1059                 }
1060                 if (icmph->type != ICMP_ECHO &&
1061                     icmph->type != ICMP_TIMESTAMP &&
1062                     icmph->type != ICMP_ADDRESS &&
1063                     icmph->type != ICMP_ADDRESSREPLY) {
1064                         goto error;
1065                 }
1066         }
1067 
1068         success = icmp_pointers[icmph->type].handler(skb);
1069 
1070         if (success)  {
1071                 consume_skb(skb);
1072                 return NET_RX_SUCCESS;
1073         }
1074 
1075 drop:
1076         kfree_skb(skb);
1077         return NET_RX_DROP;
1078 csum_error:
1079         __ICMP_INC_STATS(net, ICMP_MIB_CSUMERRORS);
1080 error:
1081         __ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
1082         goto drop;
1083 }
1084 
1085 int icmp_err(struct sk_buff *skb, u32 info)
1086 {
1087         struct iphdr *iph = (struct iphdr *)skb->data;
1088         int offset = iph->ihl<<2;
1089         struct icmphdr *icmph = (struct icmphdr *)(skb->data + offset);
1090         int type = icmp_hdr(skb)->type;
1091         int code = icmp_hdr(skb)->code;
1092         struct net *net = dev_net(skb->dev);
1093 
1094         /*
1095          * Use ping_err to handle all icmp errors except those
1096          * triggered by ICMP_ECHOREPLY which sent from kernel.
1097          */
1098         if (icmph->type != ICMP_ECHOREPLY) {
1099                 ping_err(skb, offset, info);
1100                 return 0;
1101         }
1102 
1103         if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
1104                 ipv4_update_pmtu(skb, net, info, 0, IPPROTO_ICMP);
1105         else if (type == ICMP_REDIRECT)
1106                 ipv4_redirect(skb, net, 0, IPPROTO_ICMP);
1107 
1108         return 0;
1109 }
1110 
1111 /*
1112  *      This table is the definition of how we handle ICMP.
1113  */
1114 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = {
1115         [ICMP_ECHOREPLY] = {
1116                 .handler = ping_rcv,
1117         },
1118         [1] = {
1119                 .handler = icmp_discard,
1120                 .error = 1,
1121         },
1122         [2] = {
1123                 .handler = icmp_discard,
1124                 .error = 1,
1125         },
1126         [ICMP_DEST_UNREACH] = {
1127                 .handler = icmp_unreach,
1128                 .error = 1,
1129         },
1130         [ICMP_SOURCE_QUENCH] = {
1131                 .handler = icmp_unreach,
1132                 .error = 1,
1133         },
1134         [ICMP_REDIRECT] = {
1135                 .handler = icmp_redirect,
1136                 .error = 1,
1137         },
1138         [6] = {
1139                 .handler = icmp_discard,
1140                 .error = 1,
1141         },
1142         [7] = {
1143                 .handler = icmp_discard,
1144                 .error = 1,
1145         },
1146         [ICMP_ECHO] = {
1147                 .handler = icmp_echo,
1148         },
1149         [9] = {
1150                 .handler = icmp_discard,
1151                 .error = 1,
1152         },
1153         [10] = {
1154                 .handler = icmp_discard,
1155                 .error = 1,
1156         },
1157         [ICMP_TIME_EXCEEDED] = {
1158                 .handler = icmp_unreach,
1159                 .error = 1,
1160         },
1161         [ICMP_PARAMETERPROB] = {
1162                 .handler = icmp_unreach,
1163                 .error = 1,
1164         },
1165         [ICMP_TIMESTAMP] = {
1166                 .handler = icmp_timestamp,
1167         },
1168         [ICMP_TIMESTAMPREPLY] = {
1169                 .handler = icmp_discard,
1170         },
1171         [ICMP_INFO_REQUEST] = {
1172                 .handler = icmp_discard,
1173         },
1174         [ICMP_INFO_REPLY] = {
1175                 .handler = icmp_discard,
1176         },
1177         [ICMP_ADDRESS] = {
1178                 .handler = icmp_discard,
1179         },
1180         [ICMP_ADDRESSREPLY] = {
1181                 .handler = icmp_discard,
1182         },
1183 };
1184 
1185 static void __net_exit icmp_sk_exit(struct net *net)
1186 {
1187         int i;
1188 
1189         for_each_possible_cpu(i)
1190                 inet_ctl_sock_destroy(*per_cpu_ptr(net->ipv4.icmp_sk, i));
1191         free_percpu(net->ipv4.icmp_sk);
1192         net->ipv4.icmp_sk = NULL;
1193 }
1194 
1195 static int __net_init icmp_sk_init(struct net *net)
1196 {
1197         int i, err;
1198 
1199         net->ipv4.icmp_sk = alloc_percpu(struct sock *);
1200         if (!net->ipv4.icmp_sk)
1201                 return -ENOMEM;
1202 
1203         for_each_possible_cpu(i) {
1204                 struct sock *sk;
1205 
1206                 err = inet_ctl_sock_create(&sk, PF_INET,
1207                                            SOCK_RAW, IPPROTO_ICMP, net);
1208                 if (err < 0)
1209                         goto fail;
1210 
1211                 *per_cpu_ptr(net->ipv4.icmp_sk, i) = sk;
1212 
1213                 /* Enough space for 2 64K ICMP packets, including
1214                  * sk_buff/skb_shared_info struct overhead.
1215                  */
1216                 sk->sk_sndbuf = 2 * SKB_TRUESIZE(64 * 1024);
1217 
1218                 /*
1219                  * Speedup sock_wfree()
1220                  */
1221                 sock_set_flag(sk, SOCK_USE_WRITE_QUEUE);
1222                 inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT;
1223         }
1224 
1225         /* Control parameters for ECHO replies. */
1226         net->ipv4.sysctl_icmp_echo_ignore_all = 0;
1227         net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1;
1228 
1229         /* Control parameter - ignore bogus broadcast responses? */
1230         net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1;
1231 
1232         /*
1233          *      Configurable global rate limit.
1234          *
1235          *      ratelimit defines tokens/packet consumed for dst->rate_token
1236          *      bucket ratemask defines which icmp types are ratelimited by
1237          *      setting it's bit position.
1238          *
1239          *      default:
1240          *      dest unreachable (3), source quench (4),
1241          *      time exceeded (11), parameter problem (12)
1242          */
1243 
1244         net->ipv4.sysctl_icmp_ratelimit = 1 * HZ;
1245         net->ipv4.sysctl_icmp_ratemask = 0x1818;
1246         net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0;
1247 
1248         return 0;
1249 
1250 fail:
1251         icmp_sk_exit(net);
1252         return err;
1253 }
1254 
1255 static struct pernet_operations __net_initdata icmp_sk_ops = {
1256        .init = icmp_sk_init,
1257        .exit = icmp_sk_exit,
1258 };
1259 
1260 int __init icmp_init(void)
1261 {
1262         return register_pernet_subsys(&icmp_sk_ops);
1263 }
/* [<][>][^][v][top][bottom][index][help] */
root/net/ipv4/icmp.c

DEFINITIONS
