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  * Version:     $Id: ip_input.c,v 1.55 2002/01/12 07:39:45 davem Exp $
   9  *
  10  * Authors:     Ross Biro
  11  *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
  12  *              Donald Becker, <becker@super.org>
  13  *              Alan Cox, <Alan.Cox@linux.org>
  14  *              Richard Underwood
  15  *              Stefan Becker, <stefanb@yello.ping.de>
  16  *              Jorge Cwik, <jorge@laser.satlink.net>
  17  *              Arnt Gulbrandsen, <agulbra@nvg.unit.no>
  18  *
  19  *
  20  * Fixes:
  21  *              Alan Cox        :       Commented a couple of minor bits of surplus code
  22  *              Alan Cox        :       Undefining IP_FORWARD doesn't include the code
  23  *                                      (just stops a compiler warning).
  24  *              Alan Cox        :       Frames with >=MAX_ROUTE record routes, strict routes or loose routes
  25  *                                      are junked rather than corrupting things.
  26  *              Alan Cox        :       Frames to bad broadcast subnets are dumped
  27  *                                      We used to process them non broadcast and
  28  *                                      boy could that cause havoc.
  29  *              Alan Cox        :       ip_forward sets the free flag on the
  30  *                                      new frame it queues. Still crap because
  31  *                                      it copies the frame but at least it
  32  *                                      doesn't eat memory too.
  33  *              Alan Cox        :       Generic queue code and memory fixes.
  34  *              Fred Van Kempen :       IP fragment support (borrowed from NET2E)
  35  *              Gerhard Koerting:       Forward fragmented frames correctly.
  36  *              Gerhard Koerting:       Fixes to my fix of the above 8-).
  37  *              Gerhard Koerting:       IP interface addressing fix.
  38  *              Linus Torvalds  :       More robustness checks
  39  *              Alan Cox        :       Even more checks: Still not as robust as it ought to be
  40  *              Alan Cox        :       Save IP header pointer for later
  41  *              Alan Cox        :       ip option setting
  42  *              Alan Cox        :       Use ip_tos/ip_ttl settings
  43  *              Alan Cox        :       Fragmentation bogosity removed
  44  *                                      (Thanks to Mark.Bush@prg.ox.ac.uk)
  45  *              Dmitry Gorodchanin :    Send of a raw packet crash fix.
  46  *              Alan Cox        :       Silly ip bug when an overlength
  47  *                                      fragment turns up. Now frees the
  48  *                                      queue.
  49  *              Linus Torvalds/ :       Memory leakage on fragmentation
  50  *              Alan Cox        :       handling.
  51  *              Gerhard Koerting:       Forwarding uses IP priority hints
  52  *              Teemu Rantanen  :       Fragment problems.
  53  *              Alan Cox        :       General cleanup, comments and reformat
  54  *              Alan Cox        :       SNMP statistics
  55  *              Alan Cox        :       BSD address rule semantics. Also see
  56  *                                      UDP as there is a nasty checksum issue
  57  *                                      if you do things the wrong way.
  58  *              Alan Cox        :       Always defrag, moved IP_FORWARD to the config.in file
  59  *              Alan Cox        :       IP options adjust sk->priority.
  60  *              Pedro Roque     :       Fix mtu/length error in ip_forward.
  61  *              Alan Cox        :       Avoid ip_chk_addr when possible.
  62  *      Richard Underwood       :       IP multicasting.
  63  *              Alan Cox        :       Cleaned up multicast handlers.
  64  *              Alan Cox        :       RAW sockets demultiplex in the BSD style.
  65  *              Gunther Mayer   :       Fix the SNMP reporting typo
  66  *              Alan Cox        :       Always in group 224.0.0.1
  67  *      Pauline Middelink       :       Fast ip_checksum update when forwarding
  68  *                                      Masquerading support.
  69  *              Alan Cox        :       Multicast loopback error for 224.0.0.1
  70  *              Alan Cox        :       IP_MULTICAST_LOOP option.
  71  *              Alan Cox        :       Use notifiers.
  72  *              Bjorn Ekwall    :       Removed ip_csum (from slhc.c too)
  73  *              Bjorn Ekwall    :       Moved ip_fast_csum to ip.h (inline!)
  74  *              Stefan Becker   :       Send out ICMP HOST REDIRECT
  75  *      Arnt Gulbrandsen        :       ip_build_xmit
  76  *              Alan Cox        :       Per socket routing cache
  77  *              Alan Cox        :       Fixed routing cache, added header cache.
  78  *              Alan Cox        :       Loopback didn't work right in original ip_build_xmit - fixed it.
  79  *              Alan Cox        :       Only send ICMP_REDIRECT if src/dest are the same net.
  80  *              Alan Cox        :       Incoming IP option handling.
  81  *              Alan Cox        :       Set saddr on raw output frames as per BSD.
  82  *              Alan Cox        :       Stopped broadcast source route explosions.
  83  *              Alan Cox        :       Can disable source routing
  84  *              Takeshi Sone    :       Masquerading didn't work.
  85  *      Dave Bonn,Alan Cox      :       Faster IP forwarding whenever possible.
  86  *              Alan Cox        :       Memory leaks, tramples, misc debugging.
  87  *              Alan Cox        :       Fixed multicast (by popular demand 8))
  88  *              Alan Cox        :       Fixed forwarding (by even more popular demand 8))
  89  *              Alan Cox        :       Fixed SNMP statistics [I think]
  90  *      Gerhard Koerting        :       IP fragmentation forwarding fix
  91  *              Alan Cox        :       Device lock against page fault.
  92  *              Alan Cox        :       IP_HDRINCL facility.
  93  *      Werner Almesberger      :       Zero fragment bug
  94  *              Alan Cox        :       RAW IP frame length bug
  95  *              Alan Cox        :       Outgoing firewall on build_xmit
  96  *              A.N.Kuznetsov   :       IP_OPTIONS support throughout the kernel
  97  *              Alan Cox        :       Multicast routing hooks
  98  *              Jos Vos         :       Do accounting *before* call_in_firewall
  99  *      Willy Konynenberg       :       Transparent proxying support
 100  *
 101  *
 102  *
 103  * To Fix:
 104  *              IP fragmentation wants rewriting cleanly. The RFC815 algorithm is much more efficient
 105  *              and could be made very efficient with the addition of some virtual memory hacks to permit
 106  *              the allocation of a buffer that can then be 'grown' by twiddling page tables.
 107  *              Output fragmentation wants updating along with the buffer management to use a single
 108  *              interleaved copy algorithm so that fragmenting has a one copy overhead. Actual packet
 109  *              output should probably do its own fragmentation at the UDP/RAW layer. TCP shouldn't cause
 110  *              fragmentation anyway.
 111  *
 112  *              This program is free software; you can redistribute it and/or
 113  *              modify it under the terms of the GNU General Public License
 114  *              as published by the Free Software Foundation; either version
 115  *              2 of the License, or (at your option) any later version.
 116  */
 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/config.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/netdevice.h>
 132 #include <linux/etherdevice.h>
 133
 134 #include <net/snmp.h>
 135 #include <net/ip.h>
 136 #include <net/protocol.h>
 137 #include <net/route.h>
 138 #include <linux/skbuff.h>
 139 #include <net/sock.h>
 140 #include <net/arp.h>
 141 #include <net/icmp.h>
 142 #include <net/raw.h>
 143 #include <net/checksum.h>
 144 #include <linux/netfilter_ipv4.h>
 145 #include <net/xfrm.h>
 146 #include <linux/mroute.h>
 147 #include <linux/netlink.h>
 148
 149 /*
 150  *      SNMP management statistics
 151  */
 152
 153 DEFINE_SNMP_STAT(struct ipstats_mib, ip_statistics);
 154
 155 /*
 156  *      Process Router Attention IP option
 157  */
 158 int ip_call_ra_chain(struct sk_buff *skb)
 159 {
 160         struct ip_ra_chain *ra;
 161         u8 protocol = skb->nh.iph->protocol;
 162         struct sock *last = NULL;
 163
 164         read_lock(&ip_ra_lock);
 165         for (ra = ip_ra_chain; ra; ra = ra->next) {
 166                 struct sock *sk = ra->sk;
 167
 168                 /* If socket is bound to an interface, only report
 169                  * the packet if it came  from that interface.
 170                  */
 171                 if (sk && inet_sk(sk)->num == protocol &&
 172                     (!sk->sk_bound_dev_if ||
 173                      sk->sk_bound_dev_if == skb->dev->ifindex)) {
 174                         if (skb->nh.iph->frag_off & htons(IP_MF|IP_OFFSET)) {
 175                                 skb = ip_defrag(skb, IP_DEFRAG_CALL_RA_CHAIN);
 176                                 if (skb == NULL) {
 177                                         read_unlock(&ip_ra_lock);
 178                                         return 1;
 179                                 }
 180                         }
 181                         if (last) {
 182                                 struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);
 183                                 if (skb2)
 184                                         raw_rcv(last, skb2);
 185                         }
 186                         last = sk;
 187                 }
 188         }
 189
 190         if (last) {
 191                 raw_rcv(last, skb);
 192                 read_unlock(&ip_ra_lock);
 193                 return 1;
 194         }
 195         read_unlock(&ip_ra_lock);
 196         return 0;
 197 }
 198
 199 static inline int ip_local_deliver_finish(struct sk_buff *skb)
 200 {
 201         int ihl = skb->nh.iph->ihl*4;
 202
 203         __skb_pull(skb, ihl);
 204
 205         /* Free reference early: we don't need it any more, and it may
 206            hold ip_conntrack module loaded indefinitely. */
 207         nf_reset(skb);
 208
 209         /* Point into the IP datagram, just past the header. */
 210         skb->h.raw = skb->data;
 211
 212         rcu_read_lock();
 213         {
 214                 /* Note: See raw.c and net/raw.h, RAWV4_HTABLE_SIZE==MAX_INET_PROTOS */
 215                 int protocol = skb->nh.iph->protocol;
 216                 int hash;
 217                 struct sock *raw_sk;
 218                 struct net_protocol *ipprot;
 219
 220         resubmit:
 221                 hash = protocol & (MAX_INET_PROTOS - 1);
 222                 raw_sk = sk_head(&raw_v4_htable[hash]);
 223
 224                 /* If there maybe a raw socket we must check - if not we
 225                  * don't care less
 226                  */
 227                 if (raw_sk)
 228                         raw_v4_input(skb, skb->nh.iph, hash);
 229
 230                 if ((ipprot = rcu_dereference(inet_protos[hash])) != NULL) {
 231                         int ret;
 232
 233                         if (!ipprot->no_policy &&
 234                             !xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
 235                                 kfree_skb(skb);
 236                                 goto out;
 237                         }
 238                         ret = ipprot->handler(skb);
 239                         if (ret < 0) {
 240                                 protocol = -ret;
 241                                 goto resubmit;
 242                         }
 243                         IP_INC_STATS_BH(IPSTATS_MIB_INDELIVERS);
 244                 } else {
 245                         if (!raw_sk) {
 246                                 if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
 247                                         IP_INC_STATS_BH(IPSTATS_MIB_INUNKNOWNPROTOS);
 248                                         icmp_send(skb, ICMP_DEST_UNREACH,
 249                                                   ICMP_PROT_UNREACH, 0);
 250                                 }
 251                         } else
 252                                 IP_INC_STATS_BH(IPSTATS_MIB_INDELIVERS);
 253                         kfree_skb(skb);
 254                 }
 255         }
 256  out:
 257         rcu_read_unlock();
 258
 259         return 0;
 260 }
 261
 262 /*
 263  *      Deliver IP Packets to the higher protocol layers.
 264  */
 265 int ip_local_deliver(struct sk_buff *skb)
 266 {
 267         /*
 268          *      Reassemble IP fragments.
 269          */
 270
 271         if (skb->nh.iph->frag_off & htons(IP_MF|IP_OFFSET)) {
 272                 skb = ip_defrag(skb, IP_DEFRAG_LOCAL_DELIVER);
 273                 if (!skb)
 274                         return 0;
 275         }
 276
 277         return NF_HOOK(PF_INET, NF_IP_LOCAL_IN, skb, skb->dev, NULL,
 278                        ip_local_deliver_finish);
 279 }
 280
 281 static inline int ip_rcv_finish(struct sk_buff *skb)
 282 {
 283         struct net_device *dev = skb->dev;
 284         struct iphdr *iph = skb->nh.iph;
 285
 286         /*
 287          *      Initialise the virtual path cache for the packet. It describes
 288          *      how the packet travels inside Linux networking.
 289          */
 290         if (skb->dst == NULL) {
 291                 if (ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, dev))
 292                         goto drop;
 293         }
 294
 295 #ifdef CONFIG_NET_CLS_ROUTE
 296         if (skb->dst->tclassid) {
 297                 struct ip_rt_acct *st = ip_rt_acct + 256*smp_processor_id();
 298                 u32 idx = skb->dst->tclassid;
 299                 st[idx&0xFF].o_packets++;
 300                 st[idx&0xFF].o_bytes+=skb->len;
 301                 st[(idx>>16)&0xFF].i_packets++;
 302                 st[(idx>>16)&0xFF].i_bytes+=skb->len;
 303         }
 304 #endif
 305
 306         if (iph->ihl > 5) {
 307                 struct ip_options *opt;
 308
 309                 /* It looks as overkill, because not all
 310                    IP options require packet mangling.
 311                    But it is the easiest for now, especially taking
 312                    into account that combination of IP options
 313                    and running sniffer is extremely rare condition.
 314                                                       --ANK (980813)
 315                 */
 316
 317                 if (skb_cow(skb, skb_headroom(skb))) {
 318                         IP_INC_STATS_BH(IPSTATS_MIB_INDISCARDS);
 319                         goto drop;
 320                 }
 321                 iph = skb->nh.iph;
 322
 323                 if (ip_options_compile(NULL, skb))
 324                         goto inhdr_error;
 325
 326                 opt = &(IPCB(skb)->opt);
 327                 if (opt->srr) {
 328                         struct in_device *in_dev = in_dev_get(dev);
 329                         if (in_dev) {
 330                                 if (!IN_DEV_SOURCE_ROUTE(in_dev)) {
 331                                         if (IN_DEV_LOG_MARTIANS(in_dev) && net_ratelimit())
 332                                                 printk(KERN_INFO "source route option %u.%u.%u.%u -> %u.%u.%u.%u\n",
 333                                                        NIPQUAD(iph->saddr), NIPQUAD(iph->daddr));
 334                                         in_dev_put(in_dev);
 335                                         goto drop;
 336                                 }
 337                                 in_dev_put(in_dev);
 338                         }
 339                         if (ip_options_rcv_srr(skb))
 340                                 goto drop;
 341                 }
 342         }
 343
 344         return dst_input(skb);
 345
 346 inhdr_error:
 347         IP_INC_STATS_BH(IPSTATS_MIB_INHDRERRORS);
 348 drop:
 349         kfree_skb(skb);
 350         return NET_RX_DROP;
 351 }
 352
 353 /*
 354  *      Main IP Receive routine.
 355  */
 356 int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt)
 357 {
 358         struct iphdr *iph;
 359
 360         /* When the interface is in promisc. mode, drop all the crap
 361          * that it receives, do not try to analyse it.
 362          */
 363         if (skb->pkt_type == PACKET_OTHERHOST)
 364                 goto drop;
 365
 366         IP_INC_STATS_BH(IPSTATS_MIB_INRECEIVES);
 367
 368         if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL) {
 369                 IP_INC_STATS_BH(IPSTATS_MIB_INDISCARDS);
 370                 goto out;
 371         }
 372
 373         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
 374                 goto inhdr_error;
 375
 376         iph = skb->nh.iph;
 377
 378         /*
 379          *      RFC1122: 3.1.2.2 MUST silently discard any IP frame that fails the checksum.
 380          *
 381          *      Is the datagram acceptable?
 382          *
 383          *      1.      Length at least the size of an ip header
 384          *      2.      Version of 4
 385          *      3.      Checksums correctly. [Speed optimisation for later, skip loopback checksums]
 386          *      4.      Doesn't have a bogus length
 387          */
 388
 389         if (iph->ihl < 5 || iph->version != 4)
 390                 goto inhdr_error;
 391
 392         if (!pskb_may_pull(skb, iph->ihl*4))
 393                 goto inhdr_error;
 394
 395         iph = skb->nh.iph;
 396
 397         if (ip_fast_csum((u8 *)iph, iph->ihl) != 0)
 398                 goto inhdr_error;
 399
 400         {
 401                 __u32 len = ntohs(iph->tot_len);
 402                 if (skb->len < len || len < (iph->ihl<<2))
 403                         goto inhdr_error;
 404
 405                 /* Our transport medium may have padded the buffer out. Now we know it
 406                  * is IP we can trim to the true length of the frame.
 407                  * Note this now means skb->len holds ntohs(iph->tot_len).
 408                  */
 409                 if (pskb_trim_rcsum(skb, len)) {
 410                         IP_INC_STATS_BH(IPSTATS_MIB_INDISCARDS);
 411                         goto drop;
 412                 }
 413         }
 414
 415         return NF_HOOK(PF_INET, NF_IP_PRE_ROUTING, skb, dev, NULL,
 416                        ip_rcv_finish);
 417
 418 inhdr_error:
 419         IP_INC_STATS_BH(IPSTATS_MIB_INHDRERRORS);
 420 drop:
 421         kfree_skb(skb);
 422 out:
 423         return NET_RX_DROP;
 424 }
 425
 426 EXPORT_SYMBOL(ip_rcv);
 427 EXPORT_SYMBOL(ip_statistics);