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
 125 #include <linux/net.h>
 126 #include <linux/socket.h>
 127 #include <linux/sockios.h>
 128 #include <linux/in.h>
 129 #include <linux/inet.h>
 130 #include <linux/inetdevice.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) __read_mostly;
 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         /* Point into the IP datagram, just past the header. */
 206         skb->h.raw = skb->data;
 207
 208         rcu_read_lock();
 209         {
 210                 /* Note: See raw.c and net/raw.h, RAWV4_HTABLE_SIZE==MAX_INET_PROTOS */
 211                 int protocol = skb->nh.iph->protocol;
 212                 int hash;
 213                 struct sock *raw_sk;
 214                 struct net_protocol *ipprot;
 215
 216         resubmit:
 217                 hash = protocol & (MAX_INET_PROTOS - 1);
 218                 raw_sk = sk_head(&raw_v4_htable[hash]);
 219
 220                 /* If there maybe a raw socket we must check - if not we
 221                  * don't care less
 222                  */
 223                 if (raw_sk && !raw_v4_input(skb, skb->nh.iph, hash))
 224                         raw_sk = NULL;
 225
 226                 if ((ipprot = rcu_dereference(inet_protos[hash])) != NULL) {
 227                         int ret;
 228
 229                         if (!ipprot->no_policy) {
 230                                 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
 231                                         kfree_skb(skb);
 232                                         goto out;
 233                                 }
 234                                 nf_reset(skb);
 235                         }
 236                         ret = ipprot->handler(skb);
 237                         if (ret < 0) {
 238                                 protocol = -ret;
 239                                 goto resubmit;
 240                         }
 241                         IP_INC_STATS_BH(IPSTATS_MIB_INDELIVERS);
 242                 } else {
 243                         if (!raw_sk) {
 244                                 if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
 245                                         IP_INC_STATS_BH(IPSTATS_MIB_INUNKNOWNPROTOS);
 246                                         icmp_send(skb, ICMP_DEST_UNREACH,
 247                                                   ICMP_PROT_UNREACH, 0);
 248                                 }
 249                         } else
 250                                 IP_INC_STATS_BH(IPSTATS_MIB_INDELIVERS);
 251                         kfree_skb(skb);
 252                 }
 253         }
 254  out:
 255         rcu_read_unlock();
 256
 257         return 0;
 258 }
 259
 260 /*
 261  *      Deliver IP Packets to the higher protocol layers.
 262  */
 263 int ip_local_deliver(struct sk_buff *skb)
 264 {
 265         /*
 266          *      Reassemble IP fragments.
 267          */
 268
 269         if (skb->nh.iph->frag_off & htons(IP_MF|IP_OFFSET)) {
 270                 skb = ip_defrag(skb, IP_DEFRAG_LOCAL_DELIVER);
 271                 if (!skb)
 272                         return 0;
 273         }
 274
 275         return NF_HOOK(PF_INET, NF_IP_LOCAL_IN, skb, skb->dev, NULL,
 276                        ip_local_deliver_finish);
 277 }
 278
 279 static inline int ip_rcv_options(struct sk_buff *skb)
 280 {
 281         struct ip_options *opt;
 282         struct iphdr *iph;
 283         struct net_device *dev = skb->dev;
 284
 285         /* It looks as overkill, because not all
 286            IP options require packet mangling.
 287            But it is the easiest for now, especially taking
 288            into account that combination of IP options
 289            and running sniffer is extremely rare condition.
 290                                               --ANK (980813)
 291         */
 292         if (skb_cow(skb, skb_headroom(skb))) {
 293                 IP_INC_STATS_BH(IPSTATS_MIB_INDISCARDS);
 294                 goto drop;
 295         }
 296
 297         iph = skb->nh.iph;
 298
 299         if (ip_options_compile(NULL, skb)) {
 300                 IP_INC_STATS_BH(IPSTATS_MIB_INHDRERRORS);
 301                 goto drop;
 302         }
 303
 304         opt = &(IPCB(skb)->opt);
 305         if (unlikely(opt->srr)) {
 306                 struct in_device *in_dev = in_dev_get(dev);
 307                 if (in_dev) {
 308                         if (!IN_DEV_SOURCE_ROUTE(in_dev)) {
 309                                 if (IN_DEV_LOG_MARTIANS(in_dev) &&
 310                                     net_ratelimit())
 311                                         printk(KERN_INFO "source route option "
 312                                                "%u.%u.%u.%u -> %u.%u.%u.%u\n",
 313                                                NIPQUAD(iph->saddr),
 314                                                NIPQUAD(iph->daddr));
 315                                 in_dev_put(in_dev);
 316                                 goto drop;
 317                         }
 318
 319                         in_dev_put(in_dev);
 320                 }
 321
 322                 if (ip_options_rcv_srr(skb))
 323                         goto drop;
 324         }
 325
 326         return 0;
 327 drop:
 328         return -1;
 329 }
 330
 331 static inline int ip_rcv_finish(struct sk_buff *skb)
 332 {
 333         struct iphdr *iph = skb->nh.iph;
 334
 335         /*
 336          *      Initialise the virtual path cache for the packet. It describes
 337          *      how the packet travels inside Linux networking.
 338          */
 339         if (skb->dst == NULL) {
 340                 int err = ip_route_input(skb, iph->daddr, iph->saddr, iph->tos,
 341                                          skb->dev);
 342                 if (unlikely(err)) {
 343                         if (err == -EHOSTUNREACH)
 344                                 IP_INC_STATS_BH(IPSTATS_MIB_INADDRERRORS);
 345                         goto drop;
 346                 }
 347         }
 348
 349 #ifdef CONFIG_NET_CLS_ROUTE
 350         if (unlikely(skb->dst->tclassid)) {
 351                 struct ip_rt_acct *st = ip_rt_acct + 256*smp_processor_id();
 352                 u32 idx = skb->dst->tclassid;
 353                 st[idx&0xFF].o_packets++;
 354                 st[idx&0xFF].o_bytes+=skb->len;
 355                 st[(idx>>16)&0xFF].i_packets++;
 356                 st[(idx>>16)&0xFF].i_bytes+=skb->len;
 357         }
 358 #endif
 359
 360         if (iph->ihl > 5 && ip_rcv_options(skb))
 361                 goto drop;
 362
 363         return dst_input(skb);
 364
 365 drop:
 366         kfree_skb(skb);
 367         return NET_RX_DROP;
 368 }
 369
 370 /*
 371  *      Main IP Receive routine.
 372  */
 373 int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev)
 374 {
 375         struct iphdr *iph;
 376         u32 len;
 377
 378         /* When the interface is in promisc. mode, drop all the crap
 379          * that it receives, do not try to analyse it.
 380          */
 381         if (skb->pkt_type == PACKET_OTHERHOST)
 382                 goto drop;
 383
 384         IP_INC_STATS_BH(IPSTATS_MIB_INRECEIVES);
 385
 386         if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL) {
 387                 IP_INC_STATS_BH(IPSTATS_MIB_INDISCARDS);
 388                 goto out;
 389         }
 390
 391         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
 392                 goto inhdr_error;
 393
 394         iph = skb->nh.iph;
 395
 396         /*
 397          *      RFC1122: 3.1.2.2 MUST silently discard any IP frame that fails the checksum.
 398          *
 399          *      Is the datagram acceptable?
 400          *
 401          *      1.      Length at least the size of an ip header
 402          *      2.      Version of 4
 403          *      3.      Checksums correctly. [Speed optimisation for later, skip loopback checksums]
 404          *      4.      Doesn't have a bogus length
 405          */
 406
 407         if (iph->ihl < 5 || iph->version != 4)
 408                 goto inhdr_error;
 409
 410         if (!pskb_may_pull(skb, iph->ihl*4))
 411                 goto inhdr_error;
 412
 413         iph = skb->nh.iph;
 414
 415         if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl)))
 416                 goto inhdr_error;
 417
 418         len = ntohs(iph->tot_len);
 419         if (skb->len < len || len < (iph->ihl*4))
 420                 goto inhdr_error;
 421
 422         /* Our transport medium may have padded the buffer out. Now we know it
 423          * is IP we can trim to the true length of the frame.
 424          * Note this now means skb->len holds ntohs(iph->tot_len).
 425          */
 426         if (pskb_trim_rcsum(skb, len)) {
 427                 IP_INC_STATS_BH(IPSTATS_MIB_INDISCARDS);
 428                 goto drop;
 429         }
 430
 431         /* Remove any debris in the socket control block */
 432         memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
 433
 434         return NF_HOOK(PF_INET, NF_IP_PRE_ROUTING, skb, dev, NULL,
 435                        ip_rcv_finish);
 436
 437 inhdr_error:
 438         IP_INC_STATS_BH(IPSTATS_MIB_INHDRERRORS);
 439 drop:
 440         kfree_skb(skb);
 441 out:
 442         return NET_RX_DROP;
 443 }
 444
 445 EXPORT_SYMBOL(ip_statistics);