net/ipv4/ip_input.c

   1 /*
   2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
   3  *              operating system.  INET is implemented using the  BSD Socket
   4  *              interface as the means of communication with the user level.
   5  *
   6  *              The Internet Protocol (IP) module.
   7  *
   8  * Authors:     Ross Biro
   9  *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
  10  *              Donald Becker, <becker@super.org>
  11  *              Alan Cox, <alan@lxorguk.ukuu.org.uk>
  12  *              Richard Underwood
  13  *              Stefan Becker, <stefanb@yello.ping.de>
  14  *              Jorge Cwik, <jorge@laser.satlink.net>
  15  *              Arnt Gulbrandsen, <agulbra@nvg.unit.no>
  16  *
  17  *
  18  * Fixes:
  19  *              Alan Cox        :       Commented a couple of minor bits of surplus code
  20  *              Alan Cox        :       Undefining IP_FORWARD doesn't include the code
  21  *                                      (just stops a compiler warning).
  22  *              Alan Cox        :       Frames with >=MAX_ROUTE record routes, strict routes or loose routes
  23  *                                      are junked rather than corrupting things.
  24  *              Alan Cox        :       Frames to bad broadcast subnets are dumped
  25  *                                      We used to process them non broadcast and
  26  *                                      boy could that cause havoc.
  27  *              Alan Cox        :       ip_forward sets the free flag on the
  28  *                                      new frame it queues. Still crap because
  29  *                                      it copies the frame but at least it
  30  *                                      doesn't eat memory too.
  31  *              Alan Cox        :       Generic queue code and memory fixes.
  32  *              Fred Van Kempen :       IP fragment support (borrowed from NET2E)
  33  *              Gerhard Koerting:       Forward fragmented frames correctly.
  34  *              Gerhard Koerting:       Fixes to my fix of the above 8-).
  35  *              Gerhard Koerting:       IP interface addressing fix.
  36  *              Linus Torvalds  :       More robustness checks
  37  *              Alan Cox        :       Even more checks: Still not as robust as it ought to be
  38  *              Alan Cox        :       Save IP header pointer for later
  39  *              Alan Cox        :       ip option setting
  40  *              Alan Cox        :       Use ip_tos/ip_ttl settings
  41  *              Alan Cox        :       Fragmentation bogosity removed
  42  *                                      (Thanks to Mark.Bush@prg.ox.ac.uk)
  43  *              Dmitry Gorodchanin :    Send of a raw packet crash fix.
  44  *              Alan Cox        :       Silly ip bug when an overlength
  45  *                                      fragment turns up. Now frees the
  46  *                                      queue.
  47  *              Linus Torvalds/ :       Memory leakage on fragmentation
  48  *              Alan Cox        :       handling.
  49  *              Gerhard Koerting:       Forwarding uses IP priority hints
  50  *              Teemu Rantanen  :       Fragment problems.
  51  *              Alan Cox        :       General cleanup, comments and reformat
  52  *              Alan Cox        :       SNMP statistics
  53  *              Alan Cox        :       BSD address rule semantics. Also see
  54  *                                      UDP as there is a nasty checksum issue
  55  *                                      if you do things the wrong way.
  56  *              Alan Cox        :       Always defrag, moved IP_FORWARD to the config.in file
  57  *              Alan Cox        :       IP options adjust sk->priority.
  58  *              Pedro Roque     :       Fix mtu/length error in ip_forward.
  59  *              Alan Cox        :       Avoid ip_chk_addr when possible.
  60  *      Richard Underwood       :       IP multicasting.
  61  *              Alan Cox        :       Cleaned up multicast handlers.
  62  *              Alan Cox        :       RAW sockets demultiplex in the BSD style.
  63  *              Gunther Mayer   :       Fix the SNMP reporting typo
  64  *              Alan Cox        :       Always in group 224.0.0.1
  65  *      Pauline Middelink       :       Fast ip_checksum update when forwarding
  66  *                                      Masquerading support.
  67  *              Alan Cox        :       Multicast loopback error for 224.0.0.1
  68  *              Alan Cox        :       IP_MULTICAST_LOOP option.
  69  *              Alan Cox        :       Use notifiers.
  70  *              Bjorn Ekwall    :       Removed ip_csum (from slhc.c too)
  71  *              Bjorn Ekwall    :       Moved ip_fast_csum to ip.h (inline!)
  72  *              Stefan Becker   :       Send out ICMP HOST REDIRECT
  73  *      Arnt Gulbrandsen        :       ip_build_xmit
  74  *              Alan Cox        :       Per socket routing cache
  75  *              Alan Cox        :       Fixed routing cache, added header cache.
  76  *              Alan Cox        :       Loopback didn't work right in original ip_build_xmit - fixed it.
  77  *              Alan Cox        :       Only send ICMP_REDIRECT if src/dest are the same net.
  78  *              Alan Cox        :       Incoming IP option handling.
  79  *              Alan Cox        :       Set saddr on raw output frames as per BSD.
  80  *              Alan Cox        :       Stopped broadcast source route explosions.
  81  *              Alan Cox        :       Can disable source routing
  82  *              Takeshi Sone    :       Masquerading didn't work.
  83  *      Dave Bonn,Alan Cox      :       Faster IP forwarding whenever possible.
  84  *              Alan Cox        :       Memory leaks, tramples, misc debugging.
  85  *              Alan Cox        :       Fixed multicast (by popular demand 8))
  86  *              Alan Cox        :       Fixed forwarding (by even more popular demand 8))
  87  *              Alan Cox        :       Fixed SNMP statistics [I think]
  88  *      Gerhard Koerting        :       IP fragmentation forwarding fix
  89  *              Alan Cox        :       Device lock against page fault.
  90  *              Alan Cox        :       IP_HDRINCL facility.
  91  *      Werner Almesberger      :       Zero fragment bug
  92  *              Alan Cox        :       RAW IP frame length bug
  93  *              Alan Cox        :       Outgoing firewall on build_xmit
  94  *              A.N.Kuznetsov   :       IP_OPTIONS support throughout the kernel
  95  *              Alan Cox        :       Multicast routing hooks
  96  *              Jos Vos         :       Do accounting *before* call_in_firewall
  97  *      Willy Konynenberg       :       Transparent proxying support
  98  *
  99  *
 100  *
 101  * To Fix:
 102  *              IP fragmentation wants rewriting cleanly. The RFC815 algorithm is much more efficient
 103  *              and could be made very efficient with the addition of some virtual memory hacks to permit
 104  *              the allocation of a buffer that can then be 'grown' by twiddling page tables.
 105  *              Output fragmentation wants updating along with the buffer management to use a single
 106  *              interleaved copy algorithm so that fragmenting has a one copy overhead. Actual packet
 107  *              output should probably do its own fragmentation at the UDP/RAW layer. TCP shouldn't cause
 108  *              fragmentation anyway.
 109  *
 110  *              This program is free software; you can redistribute it and/or
 111  *              modify it under the terms of the GNU General Public License
 112  *              as published by the Free Software Foundation; either version
 113  *              2 of the License, or (at your option) any later version.
 114  */
 115
 116 #define pr_fmt(fmt) "IPv4: " fmt
 117
 118 #include <asm/system.h>
 119 #include <linux/module.h>
 120 #include <linux/types.h>
 121 #include <linux/kernel.h>
 122 #include <linux/string.h>
 123 #include <linux/errno.h>
 124 #include <linux/slab.h>
 125
 126 #include <linux/net.h>
 127 #include <linux/socket.h>
 128 #include <linux/sockios.h>
 129 #include <linux/in.h>
 130 #include <linux/inet.h>
 131 #include <linux/inetdevice.h>
 132 #include <linux/netdevice.h>
 133 #include <linux/etherdevice.h>
 134
 135 #include <net/snmp.h>
 136 #include <net/ip.h>
 137 #include <net/protocol.h>
 138 #include <net/route.h>
 139 #include <linux/skbuff.h>
 140 #include <net/sock.h>
 141 #include <net/arp.h>
 142 #include <net/icmp.h>
 143 #include <net/raw.h>
 144 #include <net/checksum.h>
 145 #include <linux/netfilter_ipv4.h>
 146 #include <net/xfrm.h>
 147 #include <linux/mroute.h>
 148 #include <linux/netlink.h>
 149
 150 /*
 151  *      Process Router Attention IP option (RFC 2113)
 152  */
 153 bool ip_call_ra_chain(struct sk_buff *skb)
 154 {
 155         struct ip_ra_chain *ra;
 156         u8 protocol = ip_hdr(skb)->protocol;
 157         struct sock *last = NULL;
 158         struct net_device *dev = skb->dev;
 159
 160         for (ra = rcu_dereference(ip_ra_chain); ra; ra = rcu_dereference(ra->next)) {
 161                 struct sock *sk = ra->sk;
 162
 163                 /* If socket is bound to an interface, only report
 164                  * the packet if it came  from that interface.
 165                  */
 166                 if (sk && inet_sk(sk)->inet_num == protocol &&
 167                     (!sk->sk_bound_dev_if ||
 168                      sk->sk_bound_dev_if == dev->ifindex) &&
 169                     net_eq(sock_net(sk), dev_net(dev))) {
 170                         if (ip_is_fragment(ip_hdr(skb))) {
 171                                 if (ip_defrag(skb, IP_DEFRAG_CALL_RA_CHAIN))
 172                                         return true;
 173                         }
 174                         if (last) {
 175                                 struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);
 176                                 if (skb2)
 177                                         raw_rcv(last, skb2);
 178                         }
 179                         last = sk;
 180                 }
 181         }
 182
 183         if (last) {
 184                 raw_rcv(last, skb);
 185                 return true;
 186         }
 187         return false;
 188 }
 189
 190 static int ip_local_deliver_finish(struct sk_buff *skb)
 191 {
 192         struct net *net = dev_net(skb->dev);
 193
 194         __skb_pull(skb, ip_hdrlen(skb));
 195
 196         /* Point into the IP datagram, just past the header. */
 197         skb_reset_transport_header(skb);
 198
 199         rcu_read_lock();
 200         {
 201                 int protocol = ip_hdr(skb)->protocol;
 202                 int hash, raw;
 203                 const struct net_protocol *ipprot;
 204
 205         resubmit:
 206                 raw = raw_local_deliver(skb, protocol);
 207
 208                 hash = protocol & (MAX_INET_PROTOS - 1);
 209                 ipprot = rcu_dereference(inet_protos[hash]);
 210                 if (ipprot != NULL) {
 211                         int ret;
 212
 213                         if (!net_eq(net, &init_net) && !ipprot->netns_ok) {
 214                                 if (net_ratelimit())
 215                                         printk("%s: proto %d isn't netns-ready\n",
 216                                                 __func__, protocol);
 217                                 kfree_skb(skb);
 218                                 goto out;
 219                         }
 220
 221                         if (!ipprot->no_policy) {
 222                                 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
 223                                         kfree_skb(skb);
 224                                         goto out;
 225                                 }
 226                                 nf_reset(skb);
 227                         }
 228                         ret = ipprot->handler(skb);
 229                         if (ret < 0) {
 230                                 protocol = -ret;
 231                                 goto resubmit;
 232                         }
 233                         IP_INC_STATS_BH(net, IPSTATS_MIB_INDELIVERS);
 234                 } else {
 235                         if (!raw) {
 236                                 if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
 237                                         IP_INC_STATS_BH(net, IPSTATS_MIB_INUNKNOWNPROTOS);
 238                                         icmp_send(skb, ICMP_DEST_UNREACH,
 239                                                   ICMP_PROT_UNREACH, 0);
 240                                 }
 241                         } else
 242                                 IP_INC_STATS_BH(net, IPSTATS_MIB_INDELIVERS);
 243                         kfree_skb(skb);
 244                 }
 245         }
 246  out:
 247         rcu_read_unlock();
 248
 249         return 0;
 250 }
 251
 252 /*
 253  *      Deliver IP Packets to the higher protocol layers.
 254  */
 255 int ip_local_deliver(struct sk_buff *skb)
 256 {
 257         /*
 258          *      Reassemble IP fragments.
 259          */
 260
 261         if (ip_is_fragment(ip_hdr(skb))) {
 262                 if (ip_defrag(skb, IP_DEFRAG_LOCAL_DELIVER))
 263                         return 0;
 264         }
 265
 266         return NF_HOOK(NFPROTO_IPV4, NF_INET_LOCAL_IN, skb, skb->dev, NULL,
 267                        ip_local_deliver_finish);
 268 }
 269
 270 static inline bool ip_rcv_options(struct sk_buff *skb)
 271 {
 272         struct ip_options *opt;
 273         const struct iphdr *iph;
 274         struct net_device *dev = skb->dev;
 275
 276         /* It looks as overkill, because not all
 277            IP options require packet mangling.
 278            But it is the easiest for now, especially taking
 279            into account that combination of IP options
 280            and running sniffer is extremely rare condition.
 281                                               --ANK (980813)
 282         */
 283         if (skb_cow(skb, skb_headroom(skb))) {
 284                 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS);
 285                 goto drop;
 286         }
 287
 288         iph = ip_hdr(skb);
 289         opt = &(IPCB(skb)->opt);
 290         opt->optlen = iph->ihl*4 - sizeof(struct iphdr);
 291
 292         if (ip_options_compile(dev_net(dev), opt, skb)) {
 293                 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS);
 294                 goto drop;
 295         }
 296
 297         if (unlikely(opt->srr)) {
 298                 struct in_device *in_dev = __in_dev_get_rcu(dev);
 299
 300                 if (in_dev) {
 301                         if (!IN_DEV_SOURCE_ROUTE(in_dev)) {
 302                                 if (IN_DEV_LOG_MARTIANS(in_dev) &&
 303                                     net_ratelimit())
 304                                         pr_info("source route option %pI4 -> %pI4\n",
 305                                                 &iph->saddr, &iph->daddr);
 306                                 goto drop;
 307                         }
 308                 }
 309
 310                 if (ip_options_rcv_srr(skb))
 311                         goto drop;
 312         }
 313
 314         return false;
 315 drop:
 316         return true;
 317 }
 318
 319 static int ip_rcv_finish(struct sk_buff *skb)
 320 {
 321         const struct iphdr *iph = ip_hdr(skb);
 322         struct rtable *rt;
 323
 324         /*
 325          *      Initialise the virtual path cache for the packet. It describes
 326          *      how the packet travels inside Linux networking.
 327          */
 328         if (skb_dst(skb) == NULL) {
 329                 int err = ip_route_input_noref(skb, iph->daddr, iph->saddr,
 330                                                iph->tos, skb->dev);
 331                 if (unlikely(err)) {
 332                         if (err == -EHOSTUNREACH)
 333                                 IP_INC_STATS_BH(dev_net(skb->dev),
 334                                                 IPSTATS_MIB_INADDRERRORS);
 335                         else if (err == -ENETUNREACH)
 336                                 IP_INC_STATS_BH(dev_net(skb->dev),
 337                                                 IPSTATS_MIB_INNOROUTES);
 338                         else if (err == -EXDEV)
 339                                 NET_INC_STATS_BH(dev_net(skb->dev),
 340                                                  LINUX_MIB_IPRPFILTER);
 341                         goto drop;
 342                 }
 343         }
 344
 345 #ifdef CONFIG_IP_ROUTE_CLASSID
 346         if (unlikely(skb_dst(skb)->tclassid)) {
 347                 struct ip_rt_acct *st = this_cpu_ptr(ip_rt_acct);
 348                 u32 idx = skb_dst(skb)->tclassid;
 349                 st[idx&0xFF].o_packets++;
 350                 st[idx&0xFF].o_bytes += skb->len;
 351                 st[(idx>>16)&0xFF].i_packets++;
 352                 st[(idx>>16)&0xFF].i_bytes += skb->len;
 353         }
 354 #endif
 355
 356         if (iph->ihl > 5 && ip_rcv_options(skb))
 357                 goto drop;
 358
 359         rt = skb_rtable(skb);
 360         if (rt->rt_type == RTN_MULTICAST) {
 361                 IP_UPD_PO_STATS_BH(dev_net(rt->dst.dev), IPSTATS_MIB_INMCAST,
 362                                 skb->len);
 363         } else if (rt->rt_type == RTN_BROADCAST)
 364                 IP_UPD_PO_STATS_BH(dev_net(rt->dst.dev), IPSTATS_MIB_INBCAST,
 365                                 skb->len);
 366
 367         return dst_input(skb);
 368
 369 drop:
 370         kfree_skb(skb);
 371         return NET_RX_DROP;
 372 }
 373
 374 /*
 375  *      Main IP Receive routine.
 376  */
 377 int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev)
 378 {
 379         const struct iphdr *iph;
 380         u32 len;
 381
 382         /* When the interface is in promisc. mode, drop all the crap
 383          * that it receives, do not try to analyse it.
 384          */
 385         if (skb->pkt_type == PACKET_OTHERHOST)
 386                 goto drop;
 387
 388
 389         IP_UPD_PO_STATS_BH(dev_net(dev), IPSTATS_MIB_IN, skb->len);
 390
 391         if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL) {
 392                 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS);
 393                 goto out;
 394         }
 395
 396         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
 397                 goto inhdr_error;
 398
 399         iph = ip_hdr(skb);
 400
 401         /*
 402          *      RFC1122: 3.2.1.2 MUST silently discard any IP frame that fails the checksum.
 403          *
 404          *      Is the datagram acceptable?
 405          *
 406          *      1.      Length at least the size of an ip header
 407          *      2.      Version of 4
 408          *      3.      Checksums correctly. [Speed optimisation for later, skip loopback checksums]
 409          *      4.      Doesn't have a bogus length
 410          */
 411
 412         if (iph->ihl < 5 || iph->version != 4)
 413                 goto inhdr_error;
 414
 415         if (!pskb_may_pull(skb, iph->ihl*4))
 416                 goto inhdr_error;
 417
 418         iph = ip_hdr(skb);
 419
 420         if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl)))
 421                 goto inhdr_error;
 422
 423         len = ntohs(iph->tot_len);
 424         if (skb->len < len) {
 425                 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INTRUNCATEDPKTS);
 426                 goto drop;
 427         } else if (len < (iph->ihl*4))
 428                 goto inhdr_error;
 429
 430         /* Our transport medium may have padded the buffer out. Now we know it
 431          * is IP we can trim to the true length of the frame.
 432          * Note this now means skb->len holds ntohs(iph->tot_len).
 433          */
 434         if (pskb_trim_rcsum(skb, len)) {
 435                 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS);
 436                 goto drop;
 437         }
 438
 439         /* Remove any debris in the socket control block */
 440         memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
 441
 442         /* Must drop socket now because of tproxy. */
 443         skb_orphan(skb);
 444
 445         return NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, skb, dev, NULL,
 446                        ip_rcv_finish);
 447
 448 inhdr_error:
 449         IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS);
 450 drop:
 451         kfree_skb(skb);
 452 out:
 453         return NET_RX_DROP;
 454 }