LXR linux/net/ipv4/ip

   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 <linux/module.h>
 119#include <linux/types.h>
 120#include <linux/kernel.h>
 121#include <linux/string.h>
 122#include <linux/errno.h>
 123#include <linux/slab.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 <net/inet_ecn.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 */
 153bool 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
 190static int ip_local_deliver_finish(struct sock *sk, struct sk_buff *skb)
 191{
 192        struct net *net = dev_net(skb->dev);
 193
 194        __skb_pull(skb, skb_network_header_len(skb));
 195
 196        rcu_read_lock();
 197        {
 198                int protocol = ip_hdr(skb)->protocol;
 199                const struct net_protocol *ipprot;
 200                int raw;
 201
 202        resubmit:
 203                raw = raw_local_deliver(skb, protocol);
 204
 205                ipprot = rcu_dereference(inet_protos[protocol]);
 206                if (ipprot) {
 207                        int ret;
 208
 209                        if (!ipprot->no_policy) {
 210                                if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
 211                                        kfree_skb(skb);
 212                                        goto out;
 213                                }
 214                                nf_reset(skb);
 215                        }
 216                        ret = ipprot->handler(skb);
 217                        if (ret < 0) {
 218                                protocol = -ret;
 219                                goto resubmit;
 220                        }
 221                        IP_INC_STATS_BH(net, IPSTATS_MIB_INDELIVERS);
 222                } else {
 223                        if (!raw) {
 224                                if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
 225                                        IP_INC_STATS_BH(net, IPSTATS_MIB_INUNKNOWNPROTOS);
 226                                        icmp_send(skb, ICMP_DEST_UNREACH,
 227                                                  ICMP_PROT_UNREACH, 0);
 228                                }
 229                                kfree_skb(skb);
 230                        } else {
 231                                IP_INC_STATS_BH(net, IPSTATS_MIB_INDELIVERS);
 232                                consume_skb(skb);
 233                        }
 234                }
 235        }
 236 out:
 237        rcu_read_unlock();
 238
 239        return 0;
 240}
 241
 242/*
 243 *      Deliver IP Packets to the higher protocol layers.
 244 */
 245int ip_local_deliver(struct sk_buff *skb)
 246{
 247        /*
 248         *      Reassemble IP fragments.
 249         */
 250
 251        if (ip_is_fragment(ip_hdr(skb))) {
 252                if (ip_defrag(skb, IP_DEFRAG_LOCAL_DELIVER))
 253                        return 0;
 254        }
 255
 256        return NF_HOOK(NFPROTO_IPV4, NF_INET_LOCAL_IN, NULL, skb,
 257                       skb->dev, NULL,
 258                       ip_local_deliver_finish);
 259}
 260
 261static inline bool ip_rcv_options(struct sk_buff *skb)
 262{
 263        struct ip_options *opt;
 264        const struct iphdr *iph;
 265        struct net_device *dev = skb->dev;
 266
 267        /* It looks as overkill, because not all
 268           IP options require packet mangling.
 269           But it is the easiest for now, especially taking
 270           into account that combination of IP options
 271           and running sniffer is extremely rare condition.
 272                                              --ANK (980813)
 273        */
 274        if (skb_cow(skb, skb_headroom(skb))) {
 275                IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS);
 276                goto drop;
 277        }
 278
 279        iph = ip_hdr(skb);
 280        opt = &(IPCB(skb)->opt);
 281        opt->optlen = iph->ihl*4 - sizeof(struct iphdr);
 282
 283        if (ip_options_compile(dev_net(dev), opt, skb)) {
 284                IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS);
 285                goto drop;
 286        }
 287
 288        if (unlikely(opt->srr)) {
 289                struct in_device *in_dev = __in_dev_get_rcu(dev);
 290
 291                if (in_dev) {
 292                        if (!IN_DEV_SOURCE_ROUTE(in_dev)) {
 293                                if (IN_DEV_LOG_MARTIANS(in_dev))
 294                                        net_info_ratelimited("source route option %pI4 -> %pI4\n",
 295                                                             &iph->saddr,
 296                                                             &iph->daddr);
 297                                goto drop;
 298                        }
 299                }
 300
 301                if (ip_options_rcv_srr(skb))
 302                        goto drop;
 303        }
 304
 305        return false;
 306drop:
 307        return true;
 308}
 309
 310int sysctl_ip_early_demux __read_mostly = 1;
 311EXPORT_SYMBOL(sysctl_ip_early_demux);
 312
 313static int ip_rcv_finish(struct sock *sk, struct sk_buff *skb)
 314{
 315        const struct iphdr *iph = ip_hdr(skb);
 316        struct rtable *rt;
 317
 318        if (sysctl_ip_early_demux && !skb_dst(skb) && !skb->sk) {
 319                const struct net_protocol *ipprot;
 320                int protocol = iph->protocol;
 321
 322                ipprot = rcu_dereference(inet_protos[protocol]);
 323                if (ipprot && ipprot->early_demux) {
 324                        ipprot->early_demux(skb);
 325                        /* must reload iph, skb->head might have changed */
 326                        iph = ip_hdr(skb);
 327                }
 328        }
 329
 330        /*
 331         *      Initialise the virtual path cache for the packet. It describes
 332         *      how the packet travels inside Linux networking.
 333         */
 334        if (!skb_dst(skb)) {
 335                int err = ip_route_input_noref(skb, iph->daddr, iph->saddr,
 336                                               iph->tos, skb->dev);
 337                if (unlikely(err)) {
 338                        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
 369drop:
 370        kfree_skb(skb);
 371        return NET_RX_DROP;
 372}
 373
 374/*
 375 *      Main IP Receive routine.
 376 */
 377int 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        skb = skb_share_check(skb, GFP_ATOMIC);
 392        if (!skb) {
 393                IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS);
 394                goto out;
 395        }
 396
 397        if (!pskb_may_pull(skb, sizeof(struct iphdr)))
 398                goto inhdr_error;
 399
 400        iph = ip_hdr(skb);
 401
 402        /*
 403         *      RFC1122: 3.2.1.2 MUST silently discard any IP frame that fails the checksum.
 404         *
 405         *      Is the datagram acceptable?
 406         *
 407         *      1.      Length at least the size of an ip header
 408         *      2.      Version of 4
 409         *      3.      Checksums correctly. [Speed optimisation for later, skip loopback checksums]
 410         *      4.      Doesn't have a bogus length
 411         */
 412
 413        if (iph->ihl < 5 || iph->version != 4)
 414                goto inhdr_error;
 415
 416        BUILD_BUG_ON(IPSTATS_MIB_ECT1PKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_ECT_1);
 417        BUILD_BUG_ON(IPSTATS_MIB_ECT0PKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_ECT_0);
 418        BUILD_BUG_ON(IPSTATS_MIB_CEPKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_CE);
 419        IP_ADD_STATS_BH(dev_net(dev),
 420                        IPSTATS_MIB_NOECTPKTS + (iph->tos & INET_ECN_MASK),
 421                        max_t(unsigned short, 1, skb_shinfo(skb)->gso_segs));
 422
 423        if (!pskb_may_pull(skb, iph->ihl*4))
 424                goto inhdr_error;
 425
 426        iph = ip_hdr(skb);
 427
 428        if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl)))
 429                goto csum_error;
 430
 431        len = ntohs(iph->tot_len);
 432        if (skb->len < len) {
 433                IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INTRUNCATEDPKTS);
 434                goto drop;
 435        } else if (len < (iph->ihl*4))
 436                goto inhdr_error;
 437
 438        /* Our transport medium may have padded the buffer out. Now we know it
 439         * is IP we can trim to the true length of the frame.
 440         * Note this now means skb->len holds ntohs(iph->tot_len).
 441         */
 442        if (pskb_trim_rcsum(skb, len)) {
 443                IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS);
 444                goto drop;
 445        }
 446
 447        skb->transport_header = skb->network_header + iph->ihl*4;
 448
 449        /* Remove any debris in the socket control block */
 450        memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
 451
 452        /* Must drop socket now because of tproxy. */
 453        skb_orphan(skb);
 454
 455        return NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, NULL, skb,
 456                       dev, NULL,
 457                       ip_rcv_finish);
 458
 459csum_error:
 460        IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_CSUMERRORS);
 461inhdr_error:
 462        IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS);
 463drop:
 464        kfree_skb(skb);
 465out:
 466        return NET_RX_DROP;
 467}
 468