linux/net/ipv4/ip_input.c
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   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
 153DEFINE_SNMP_STAT(struct ipstats_mib, ip_statistics) __read_mostly;
 154
 155/*
 156 *      Process Router Attention IP option
 157 */ 
 158int 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
 199static 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 */ 
 263int 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
 279static 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;
 327drop:
 328        return -1;
 329}
 330
 331static 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
 365drop:
 366        kfree_skb(skb);
 367        return NET_RX_DROP;
 368}
 369
 370/*
 371 *      Main IP Receive routine.
 372 */ 
 373int 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
 437inhdr_error:
 438        IP_INC_STATS_BH(IPSTATS_MIB_INHDRERRORS);
 439drop:
 440        kfree_skb(skb);
 441out:
 442        return NET_RX_DROP;
 443}
 444
 445EXPORT_SYMBOL(ip_statistics);
 446
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