net/ipv4/ip_output.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) output module.
   7  *
   8  * Version:     $Id: ip_output.c,v 1.100 2002/02/01 22:01:03 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  *              Hirokazu Takahashi, <taka@valinux.co.jp>
  19  *
  20  *      See ip_input.c for original log
  21  *
  22  *      Fixes:
  23  *              Alan Cox        :       Missing nonblock feature in ip_build_xmit.
  24  *              Mike Kilburn    :       htons() missing in ip_build_xmit.
  25  *              Bradford Johnson:       Fix faulty handling of some frames when
  26  *                                      no route is found.
  27  *              Alexander Demenshin:    Missing sk/skb free in ip_queue_xmit
  28  *                                      (in case if packet not accepted by
  29  *                                      output firewall rules)
  30  *              Mike McLagan    :       Routing by source
  31  *              Alexey Kuznetsov:       use new route cache
  32  *              Andi Kleen:             Fix broken PMTU recovery and remove
  33  *                                      some redundant tests.
  34  *      Vitaly E. Lavrov        :       Transparent proxy revived after year coma.
  35  *              Andi Kleen      :       Replace ip_reply with ip_send_reply.
  36  *              Andi Kleen      :       Split fast and slow ip_build_xmit path
  37  *                                      for decreased register pressure on x86
  38  *                                      and more readibility.
  39  *              Marc Boucher    :       When call_out_firewall returns FW_QUEUE,
  40  *                                      silently drop skb instead of failing with -EPERM.
  41  *              Detlev Wengorz  :       Copy protocol for fragments.
  42  *              Hirokazu Takahashi:     HW checksumming for outgoing UDP
  43  *                                      datagrams.
  44  *              Hirokazu Takahashi:     sendfile() on UDP works now.
  45  */
  46
  47 #include <asm/uaccess.h>
  48 #include <asm/system.h>
  49 #include <linux/module.h>
  50 #include <linux/types.h>
  51 #include <linux/kernel.h>
  52 #include <linux/sched.h>
  53 #include <linux/mm.h>
  54 #include <linux/string.h>
  55 #include <linux/errno.h>
  56 #include <linux/config.h>
  57
  58 #include <linux/socket.h>
  59 #include <linux/sockios.h>
  60 #include <linux/in.h>
  61 #include <linux/inet.h>
  62 #include <linux/netdevice.h>
  63 #include <linux/etherdevice.h>
  64 #include <linux/proc_fs.h>
  65 #include <linux/stat.h>
  66 #include <linux/init.h>
  67
  68 #include <net/snmp.h>
  69 #include <net/ip.h>
  70 #include <net/protocol.h>
  71 #include <net/route.h>
  72 #include <net/tcp.h>
  73 #include <net/udp.h>
  74 #include <linux/skbuff.h>
  75 #include <net/sock.h>
  76 #include <net/arp.h>
  77 #include <net/icmp.h>
  78 #include <net/raw.h>
  79 #include <net/checksum.h>
  80 #include <net/inetpeer.h>
  81 #include <net/checksum.h>
  82 #include <linux/igmp.h>
  83 #include <linux/netfilter_ipv4.h>
  84 #include <linux/netfilter_bridge.h>
  85 #include <linux/mroute.h>
  86 #include <linux/netlink.h>
  87
  88 /*
  89  *      Shall we try to damage output packets if routing dev changes?
  90  */
  91
  92 int sysctl_ip_dynaddr;
  93 int sysctl_ip_default_ttl = IPDEFTTL;
  94
  95 /* Generate a checksum for an outgoing IP datagram. */
  96 __inline__ void ip_send_check(struct iphdr *iph)
  97 {
  98         iph->check = 0;
  99         iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
 100 }
 101
 102 /* dev_loopback_xmit for use with netfilter. */
 103 static int ip_dev_loopback_xmit(struct sk_buff *newskb)
 104 {
 105         newskb->mac.raw = newskb->data;
 106         __skb_pull(newskb, newskb->nh.raw - newskb->data);
 107         newskb->pkt_type = PACKET_LOOPBACK;
 108         newskb->ip_summed = CHECKSUM_UNNECESSARY;
 109         BUG_TRAP(newskb->dst);
 110
 111 #ifdef CONFIG_NETFILTER_DEBUG
 112         nf_debug_ip_loopback_xmit(newskb);
 113 #endif
 114         nf_reset(newskb);
 115         netif_rx(newskb);
 116         return 0;
 117 }
 118
 119 static inline int ip_select_ttl(struct inet_sock *inet, struct dst_entry *dst)
 120 {
 121         int ttl = inet->uc_ttl;
 122
 123         if (ttl < 0)
 124                 ttl = dst_metric(dst, RTAX_HOPLIMIT);
 125         return ttl;
 126 }
 127
 128 /*
 129  *              Add an ip header to a skbuff and send it out.
 130  *
 131  */
 132 int ip_build_and_send_pkt(struct sk_buff *skb, struct sock *sk,
 133                           u32 saddr, u32 daddr, struct ip_options *opt)
 134 {
 135         struct inet_sock *inet = inet_sk(sk);
 136         struct rtable *rt = (struct rtable *)skb->dst;
 137         struct iphdr *iph;
 138
 139         /* Build the IP header. */
 140         if (opt)
 141                 iph=(struct iphdr *)skb_push(skb,sizeof(struct iphdr) + opt->optlen);
 142         else
 143                 iph=(struct iphdr *)skb_push(skb,sizeof(struct iphdr));
 144
 145         iph->version  = 4;
 146         iph->ihl      = 5;
 147         iph->tos      = inet->tos;
 148         if (ip_dont_fragment(sk, &rt->u.dst))
 149                 iph->frag_off = htons(IP_DF);
 150         else
 151                 iph->frag_off = 0;
 152         iph->ttl      = ip_select_ttl(inet, &rt->u.dst);
 153         iph->daddr    = rt->rt_dst;
 154         iph->saddr    = rt->rt_src;
 155         iph->protocol = sk->sk_protocol;
 156         iph->tot_len  = htons(skb->len);
 157         ip_select_ident(iph, &rt->u.dst, sk);
 158         skb->nh.iph   = iph;
 159
 160         if (opt && opt->optlen) {
 161                 iph->ihl += opt->optlen>>2;
 162                 ip_options_build(skb, opt, daddr, rt, 0);
 163         }
 164         ip_send_check(iph);
 165
 166         skb->priority = sk->sk_priority;
 167
 168         /* Send it out. */
 169         return NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, skb, NULL, rt->u.dst.dev,
 170                        dst_output);
 171 }
 172
 173 static inline int ip_finish_output2(struct sk_buff *skb)
 174 {
 175         struct dst_entry *dst = skb->dst;
 176         struct hh_cache *hh = dst->hh;
 177         struct net_device *dev = dst->dev;
 178         int hh_len = LL_RESERVED_SPACE(dev);
 179
 180         /* Be paranoid, rather than too clever. */
 181         if (unlikely(skb_headroom(skb) < hh_len && dev->hard_header)) {
 182                 struct sk_buff *skb2;
 183
 184                 skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev));
 185                 if (skb2 == NULL) {
 186                         kfree_skb(skb);
 187                         return -ENOMEM;
 188                 }
 189                 if (skb->sk)
 190                         skb_set_owner_w(skb2, skb->sk);
 191                 kfree_skb(skb);
 192                 skb = skb2;
 193         }
 194
 195 #ifdef CONFIG_NETFILTER_DEBUG
 196         nf_debug_ip_finish_output2(skb);
 197 #endif /*CONFIG_NETFILTER_DEBUG*/
 198
 199 #ifdef CONFIG_BRIDGE_NETFILTER
 200         /* bridge-netfilter defers calling some IP hooks to the bridge layer
 201          * and still needs the conntrack reference.
 202          */
 203         if (skb->nf_bridge == NULL)
 204 #endif
 205                 nf_reset(skb);
 206
 207         if (hh) {
 208                 int hh_alen;
 209
 210                 read_lock_bh(&hh->hh_lock);
 211                 hh_alen = HH_DATA_ALIGN(hh->hh_len);
 212                 memcpy(skb->data - hh_alen, hh->hh_data, hh_alen);
 213                 read_unlock_bh(&hh->hh_lock);
 214                 skb_push(skb, hh->hh_len);
 215                 return hh->hh_output(skb);
 216         } else if (dst->neighbour)
 217                 return dst->neighbour->output(skb);
 218
 219         if (net_ratelimit())
 220                 printk(KERN_DEBUG "ip_finish_output2: No header cache and no neighbour!\n");
 221         kfree_skb(skb);
 222         return -EINVAL;
 223 }
 224
 225 int ip_finish_output(struct sk_buff *skb)
 226 {
 227         struct net_device *dev = skb->dst->dev;
 228
 229         skb->dev = dev;
 230         skb->protocol = htons(ETH_P_IP);
 231
 232         return NF_HOOK(PF_INET, NF_IP_POST_ROUTING, skb, NULL, dev,
 233                        ip_finish_output2);
 234 }
 235
 236 int ip_mc_output(struct sk_buff *skb)
 237 {
 238         struct sock *sk = skb->sk;
 239         struct rtable *rt = (struct rtable*)skb->dst;
 240         struct net_device *dev = rt->u.dst.dev;
 241
 242         /*
 243          *      If the indicated interface is up and running, send the packet.
 244          */
 245         IP_INC_STATS(IPSTATS_MIB_OUTREQUESTS);
 246
 247         skb->dev = dev;
 248         skb->protocol = htons(ETH_P_IP);
 249
 250         /*
 251          *      Multicasts are looped back for other local users
 252          */
 253
 254         if (rt->rt_flags&RTCF_MULTICAST) {
 255                 if ((!sk || inet_sk(sk)->mc_loop)
 256 #ifdef CONFIG_IP_MROUTE
 257                 /* Small optimization: do not loopback not local frames,
 258                    which returned after forwarding; they will be  dropped
 259                    by ip_mr_input in any case.
 260                    Note, that local frames are looped back to be delivered
 261                    to local recipients.
 262
 263                    This check is duplicated in ip_mr_input at the moment.
 264                  */
 265                     && ((rt->rt_flags&RTCF_LOCAL) || !(IPCB(skb)->flags&IPSKB_FORWARDED))
 266 #endif
 267                 ) {
 268                         struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
 269                         if (newskb)
 270                                 NF_HOOK(PF_INET, NF_IP_POST_ROUTING, newskb, NULL,
 271                                         newskb->dev,
 272                                         ip_dev_loopback_xmit);
 273                 }
 274
 275                 /* Multicasts with ttl 0 must not go beyond the host */
 276
 277                 if (skb->nh.iph->ttl == 0) {
 278                         kfree_skb(skb);
 279                         return 0;
 280                 }
 281         }
 282
 283         if (rt->rt_flags&RTCF_BROADCAST) {
 284                 struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
 285                 if (newskb)
 286                         NF_HOOK(PF_INET, NF_IP_POST_ROUTING, newskb, NULL,
 287                                 newskb->dev, ip_dev_loopback_xmit);
 288         }
 289
 290         if (skb->len > dst_mtu(&rt->u.dst))
 291                 return ip_fragment(skb, ip_finish_output);
 292         else
 293                 return ip_finish_output(skb);
 294 }
 295
 296 int ip_output(struct sk_buff *skb)
 297 {
 298         IP_INC_STATS(IPSTATS_MIB_OUTREQUESTS);
 299
 300         if (skb->len > dst_mtu(skb->dst) && !skb_shinfo(skb)->tso_size)
 301                 return ip_fragment(skb, ip_finish_output);
 302         else
 303                 return ip_finish_output(skb);
 304 }
 305
 306 int ip_queue_xmit(struct sk_buff *skb, int ipfragok)
 307 {
 308         struct sock *sk = skb->sk;
 309         struct inet_sock *inet = inet_sk(sk);
 310         struct ip_options *opt = inet->opt;
 311         struct rtable *rt;
 312         struct iphdr *iph;
 313
 314         /* Skip all of this if the packet is already routed,
 315          * f.e. by something like SCTP.
 316          */
 317         rt = (struct rtable *) skb->dst;
 318         if (rt != NULL)
 319                 goto packet_routed;
 320
 321         /* Make sure we can route this packet. */
 322         rt = (struct rtable *)__sk_dst_check(sk, 0);
 323         if (rt == NULL) {
 324                 u32 daddr;
 325
 326                 /* Use correct destination address if we have options. */
 327                 daddr = inet->daddr;
 328                 if(opt && opt->srr)
 329                         daddr = opt->faddr;
 330
 331                 {
 332                         struct flowi fl = { .oif = sk->sk_bound_dev_if,
 333                                             .nl_u = { .ip4_u =
 334                                                       { .daddr = daddr,
 335                                                         .saddr = inet->saddr,
 336                                                         .tos = RT_CONN_FLAGS(sk) } },
 337                                             .proto = sk->sk_protocol,
 338                                             .uli_u = { .ports =
 339                                                        { .sport = inet->sport,
 340                                                          .dport = inet->dport } } };
 341
 342                         /* If this fails, retransmit mechanism of transport layer will
 343                          * keep trying until route appears or the connection times
 344                          * itself out.
 345                          */
 346                         if (ip_route_output_flow(&rt, &fl, sk, 0))
 347                                 goto no_route;
 348                 }
 349                 __sk_dst_set(sk, &rt->u.dst);
 350                 tcp_v4_setup_caps(sk, &rt->u.dst);
 351         }
 352         skb->dst = dst_clone(&rt->u.dst);
 353
 354 packet_routed:
 355         if (opt && opt->is_strictroute && rt->rt_dst != rt->rt_gateway)
 356                 goto no_route;
 357
 358         /* OK, we know where to send it, allocate and build IP header. */
 359         iph = (struct iphdr *) skb_push(skb, sizeof(struct iphdr) + (opt ? opt->optlen : 0));
 360         *((__u16 *)iph) = htons((4 << 12) | (5 << 8) | (inet->tos & 0xff));
 361         iph->tot_len = htons(skb->len);
 362         if (ip_dont_fragment(sk, &rt->u.dst) && !ipfragok)
 363                 iph->frag_off = htons(IP_DF);
 364         else
 365                 iph->frag_off = 0;
 366         iph->ttl      = ip_select_ttl(inet, &rt->u.dst);
 367         iph->protocol = sk->sk_protocol;
 368         iph->saddr    = rt->rt_src;
 369         iph->daddr    = rt->rt_dst;
 370         skb->nh.iph   = iph;
 371         /* Transport layer set skb->h.foo itself. */
 372
 373         if (opt && opt->optlen) {
 374                 iph->ihl += opt->optlen >> 2;
 375                 ip_options_build(skb, opt, inet->daddr, rt, 0);
 376         }
 377
 378         ip_select_ident_more(iph, &rt->u.dst, sk, skb_shinfo(skb)->tso_segs);
 379
 380         /* Add an IP checksum. */
 381         ip_send_check(iph);
 382
 383         skb->priority = sk->sk_priority;
 384
 385         return NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, skb, NULL, rt->u.dst.dev,
 386                        dst_output);
 387
 388 no_route:
 389         IP_INC_STATS(IPSTATS_MIB_OUTNOROUTES);
 390         kfree_skb(skb);
 391         return -EHOSTUNREACH;
 392 }
 393
 394
 395 static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
 396 {
 397         to->pkt_type = from->pkt_type;
 398         to->priority = from->priority;
 399         to->protocol = from->protocol;
 400         to->security = from->security;
 401         dst_release(to->dst);
 402         to->dst = dst_clone(from->dst);
 403         to->dev = from->dev;
 404
 405         /* Copy the flags to each fragment. */
 406         IPCB(to)->flags = IPCB(from)->flags;
 407
 408 #ifdef CONFIG_NET_SCHED
 409         to->tc_index = from->tc_index;
 410 #endif
 411 #ifdef CONFIG_NETFILTER
 412         to->nfmark = from->nfmark;
 413         to->nfcache = from->nfcache;
 414         /* Connection association is same as pre-frag packet */
 415         nf_conntrack_put(to->nfct);
 416         to->nfct = from->nfct;
 417         nf_conntrack_get(to->nfct);
 418         to->nfctinfo = from->nfctinfo;
 419 #ifdef CONFIG_BRIDGE_NETFILTER
 420         nf_bridge_put(to->nf_bridge);
 421         to->nf_bridge = from->nf_bridge;
 422         nf_bridge_get(to->nf_bridge);
 423 #endif
 424 #ifdef CONFIG_NETFILTER_DEBUG
 425         to->nf_debug = from->nf_debug;
 426 #endif
 427 #endif
 428 }
 429
 430 /*
 431  *      This IP datagram is too large to be sent in one piece.  Break it up into
 432  *      smaller pieces (each of size equal to IP header plus
 433  *      a block of the data of the original IP data part) that will yet fit in a
 434  *      single device frame, and queue such a frame for sending.
 435  */
 436
 437 int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff*))
 438 {
 439         struct iphdr *iph;
 440         int raw = 0;
 441         int ptr;
 442         struct net_device *dev;
 443         struct sk_buff *skb2;
 444         unsigned int mtu, hlen, left, len, ll_rs;
 445         int offset;
 446         int not_last_frag;
 447         struct rtable *rt = (struct rtable*)skb->dst;
 448         int err = 0;
 449
 450         dev = rt->u.dst.dev;
 451
 452         /*
 453          *      Point into the IP datagram header.
 454          */
 455
 456         iph = skb->nh.iph;
 457
 458         if (unlikely((iph->frag_off & htons(IP_DF)) && !skb->local_df)) {
 459                 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
 460                           htonl(dst_mtu(&rt->u.dst)));
 461                 kfree_skb(skb);
 462                 return -EMSGSIZE;
 463         }
 464
 465         /*
 466          *      Setup starting values.
 467          */
 468
 469         hlen = iph->ihl * 4;
 470         mtu = dst_mtu(&rt->u.dst) - hlen;       /* Size of data space */
 471
 472         /* When frag_list is given, use it. First, check its validity:
 473          * some transformers could create wrong frag_list or break existing
 474          * one, it is not prohibited. In this case fall back to copying.
 475          *
 476          * LATER: this step can be merged to real generation of fragments,
 477          * we can switch to copy when see the first bad fragment.
 478          */
 479         if (skb_shinfo(skb)->frag_list) {
 480                 struct sk_buff *frag;
 481                 int first_len = skb_pagelen(skb);
 482
 483                 if (first_len - hlen > mtu ||
 484                     ((first_len - hlen) & 7) ||
 485                     (iph->frag_off & htons(IP_MF|IP_OFFSET)) ||
 486                     skb_cloned(skb))
 487                         goto slow_path;
 488
 489                 for (frag = skb_shinfo(skb)->frag_list; frag; frag = frag->next) {
 490                         /* Correct geometry. */
 491                         if (frag->len > mtu ||
 492                             ((frag->len & 7) && frag->next) ||
 493                             skb_headroom(frag) < hlen)
 494                             goto slow_path;
 495
 496                         /* Partially cloned skb? */
 497                         if (skb_shared(frag))
 498                                 goto slow_path;
 499
 500                         BUG_ON(frag->sk);
 501                         if (skb->sk) {
 502                                 sock_hold(skb->sk);
 503                                 frag->sk = skb->sk;
 504                                 frag->destructor = sock_wfree;
 505                                 skb->truesize -= frag->truesize;
 506                         }
 507                 }
 508
 509                 /* Everything is OK. Generate! */
 510
 511                 err = 0;
 512                 offset = 0;
 513                 frag = skb_shinfo(skb)->frag_list;
 514                 skb_shinfo(skb)->frag_list = NULL;
 515                 skb->data_len = first_len - skb_headlen(skb);
 516                 skb->len = first_len;
 517                 iph->tot_len = htons(first_len);
 518                 iph->frag_off = htons(IP_MF);
 519                 ip_send_check(iph);
 520
 521                 for (;;) {
 522                         /* Prepare header of the next frame,
 523                          * before previous one went down. */
 524                         if (frag) {
 525                                 frag->ip_summed = CHECKSUM_NONE;
 526                                 frag->h.raw = frag->data;
 527                                 frag->nh.raw = __skb_push(frag, hlen);
 528                                 memcpy(frag->nh.raw, iph, hlen);
 529                                 iph = frag->nh.iph;
 530                                 iph->tot_len = htons(frag->len);
 531                                 ip_copy_metadata(frag, skb);
 532                                 if (offset == 0)
 533                                         ip_options_fragment(frag);
 534                                 offset += skb->len - hlen;
 535                                 iph->frag_off = htons(offset>>3);
 536                                 if (frag->next != NULL)
 537                                         iph->frag_off |= htons(IP_MF);
 538                                 /* Ready, complete checksum */
 539                                 ip_send_check(iph);
 540                         }
 541
 542                         err = output(skb);
 543
 544                         if (err || !frag)
 545                                 break;
 546
 547                         skb = frag;
 548                         frag = skb->next;
 549                         skb->next = NULL;
 550                 }
 551
 552                 if (err == 0) {
 553                         IP_INC_STATS(IPSTATS_MIB_FRAGOKS);
 554                         return 0;
 555                 }
 556
 557                 while (frag) {
 558                         skb = frag->next;
 559                         kfree_skb(frag);
 560                         frag = skb;
 561                 }
 562                 IP_INC_STATS(IPSTATS_MIB_FRAGFAILS);
 563                 return err;
 564         }
 565
 566 slow_path:
 567         left = skb->len - hlen;         /* Space per frame */
 568         ptr = raw + hlen;               /* Where to start from */
 569
 570 #ifdef CONFIG_BRIDGE_NETFILTER
 571         /* for bridged IP traffic encapsulated inside f.e. a vlan header,
 572          * we need to make room for the encapsulating header */
 573         ll_rs = LL_RESERVED_SPACE_EXTRA(rt->u.dst.dev, nf_bridge_pad(skb));
 574         mtu -= nf_bridge_pad(skb);
 575 #else
 576         ll_rs = LL_RESERVED_SPACE(rt->u.dst.dev);
 577 #endif
 578         /*
 579          *      Fragment the datagram.
 580          */
 581
 582         offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3;
 583         not_last_frag = iph->frag_off & htons(IP_MF);
 584
 585         /*
 586          *      Keep copying data until we run out.
 587          */
 588
 589         while(left > 0) {
 590                 len = left;
 591                 /* IF: it doesn't fit, use 'mtu' - the data space left */
 592                 if (len > mtu)
 593                         len = mtu;
 594                 /* IF: we are not sending upto and including the packet end
 595                    then align the next start on an eight byte boundary */
 596                 if (len < left) {
 597                         len &= ~7;
 598                 }
 599                 /*
 600                  *      Allocate buffer.
 601                  */
 602
 603                 if ((skb2 = alloc_skb(len+hlen+ll_rs, GFP_ATOMIC)) == NULL) {
 604                         NETDEBUG(printk(KERN_INFO "IP: frag: no memory for new fragment!\n"));
 605                         err = -ENOMEM;
 606                         goto fail;
 607                 }
 608
 609                 /*
 610                  *      Set up data on packet
 611                  */
 612
 613                 ip_copy_metadata(skb2, skb);
 614                 skb_reserve(skb2, ll_rs);
 615                 skb_put(skb2, len + hlen);
 616                 skb2->nh.raw = skb2->data;
 617                 skb2->h.raw = skb2->data + hlen;
 618
 619                 /*
 620                  *      Charge the memory for the fragment to any owner
 621                  *      it might possess
 622                  */
 623
 624                 if (skb->sk)
 625                         skb_set_owner_w(skb2, skb->sk);
 626
 627                 /*
 628                  *      Copy the packet header into the new buffer.
 629                  */
 630
 631                 memcpy(skb2->nh.raw, skb->data, hlen);
 632
 633                 /*
 634                  *      Copy a block of the IP datagram.
 635                  */
 636                 if (skb_copy_bits(skb, ptr, skb2->h.raw, len))
 637                         BUG();
 638                 left -= len;
 639
 640                 /*
 641                  *      Fill in the new header fields.
 642                  */
 643                 iph = skb2->nh.iph;
 644                 iph->frag_off = htons((offset >> 3));
 645
 646                 /* ANK: dirty, but effective trick. Upgrade options only if
 647                  * the segment to be fragmented was THE FIRST (otherwise,
 648                  * options are already fixed) and make it ONCE
 649                  * on the initial skb, so that all the following fragments
 650                  * will inherit fixed options.
 651                  */
 652                 if (offset == 0)
 653                         ip_options_fragment(skb);
 654
 655                 /*
 656                  *      Added AC : If we are fragmenting a fragment that's not the
 657                  *                 last fragment then keep MF on each bit
 658                  */
 659                 if (left > 0 || not_last_frag)
 660                         iph->frag_off |= htons(IP_MF);
 661                 ptr += len;
 662                 offset += len;
 663
 664                 /*
 665                  *      Put this fragment into the sending queue.
 666                  */
 667
 668                 IP_INC_STATS(IPSTATS_MIB_FRAGCREATES);
 669
 670                 iph->tot_len = htons(len + hlen);
 671
 672                 ip_send_check(iph);
 673
 674                 err = output(skb2);
 675                 if (err)
 676                         goto fail;
 677         }
 678         kfree_skb(skb);
 679         IP_INC_STATS(IPSTATS_MIB_FRAGOKS);
 680         return err;
 681
 682 fail:
 683         kfree_skb(skb);
 684         IP_INC_STATS(IPSTATS_MIB_FRAGFAILS);
 685         return err;
 686 }
 687
 688 int
 689 ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
 690 {
 691         struct iovec *iov = from;
 692
 693         if (skb->ip_summed == CHECKSUM_HW) {
 694                 if (memcpy_fromiovecend(to, iov, offset, len) < 0)
 695                         return -EFAULT;
 696         } else {
 697                 unsigned int csum = 0;
 698                 if (csum_partial_copy_fromiovecend(to, iov, offset, len, &csum) < 0)
 699                         return -EFAULT;
 700                 skb->csum = csum_block_add(skb->csum, csum, odd);
 701         }
 702         return 0;
 703 }
 704
 705 static inline unsigned int
 706 csum_page(struct page *page, int offset, int copy)
 707 {
 708         char *kaddr;
 709         unsigned int csum;
 710         kaddr = kmap(page);
 711         csum = csum_partial(kaddr + offset, copy, 0);
 712         kunmap(page);
 713         return csum;
 714 }
 715
 716 /*
 717  *      ip_append_data() and ip_append_page() can make one large IP datagram
 718  *      from many pieces of data. Each pieces will be holded on the socket
 719  *      until ip_push_pending_frames() is called. Each piece can be a page
 720  *      or non-page data.
 721  *
 722  *      Not only UDP, other transport protocols - e.g. raw sockets - can use
 723  *      this interface potentially.
 724  *
 725  *      LATER: length must be adjusted by pad at tail, when it is required.
 726  */
 727 int ip_append_data(struct sock *sk,
 728                    int getfrag(void *from, char *to, int offset, int len,
 729                                int odd, struct sk_buff *skb),
 730                    void *from, int length, int transhdrlen,
 731                    struct ipcm_cookie *ipc, struct rtable *rt,
 732                    unsigned int flags)
 733 {
 734         struct inet_sock *inet = inet_sk(sk);
 735         struct sk_buff *skb;
 736
 737         struct ip_options *opt = NULL;
 738         int hh_len;
 739         int exthdrlen;
 740         int mtu;
 741         int copy;
 742         int err;
 743         int offset = 0;
 744         unsigned int maxfraglen, fragheaderlen;
 745         int csummode = CHECKSUM_NONE;
 746
 747         if (flags&MSG_PROBE)
 748                 return 0;
 749
 750         if (skb_queue_empty(&sk->sk_write_queue)) {
 751                 /*
 752                  * setup for corking.
 753                  */
 754                 opt = ipc->opt;
 755                 if (opt) {
 756                         if (inet->cork.opt == NULL) {
 757                                 inet->cork.opt = kmalloc(sizeof(struct ip_options) + 40, sk->sk_allocation);
 758                                 if (unlikely(inet->cork.opt == NULL))
 759                                         return -ENOBUFS;
 760                         }
 761                         memcpy(inet->cork.opt, opt, sizeof(struct ip_options)+opt->optlen);
 762                         inet->cork.flags |= IPCORK_OPT;
 763                         inet->cork.addr = ipc->addr;
 764                 }
 765                 dst_hold(&rt->u.dst);
 766                 inet->cork.fragsize = mtu = dst_mtu(rt->u.dst.path);
 767                 inet->cork.rt = rt;
 768                 inet->cork.length = 0;
 769                 sk->sk_sndmsg_page = NULL;
 770                 sk->sk_sndmsg_off = 0;
 771                 if ((exthdrlen = rt->u.dst.header_len) != 0) {
 772                         length += exthdrlen;
 773                         transhdrlen += exthdrlen;
 774                 }
 775         } else {
 776                 rt = inet->cork.rt;
 777                 if (inet->cork.flags & IPCORK_OPT)
 778                         opt = inet->cork.opt;
 779
 780                 transhdrlen = 0;
 781                 exthdrlen = 0;
 782                 mtu = inet->cork.fragsize;
 783         }
 784         hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
 785
 786         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
 787         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
 788
 789         if (inet->cork.length + length > 0xFFFF - fragheaderlen) {
 790                 ip_local_error(sk, EMSGSIZE, rt->rt_dst, inet->dport, mtu-exthdrlen);
 791                 return -EMSGSIZE;
 792         }
 793
 794         /*
 795          * transhdrlen > 0 means that this is the first fragment and we wish
 796          * it won't be fragmented in the future.
 797          */
 798         if (transhdrlen &&
 799             length + fragheaderlen <= mtu &&
 800             rt->u.dst.dev->features&(NETIF_F_IP_CSUM|NETIF_F_NO_CSUM|NETIF_F_HW_CSUM) &&
 801             !exthdrlen)
 802                 csummode = CHECKSUM_HW;
 803
 804         inet->cork.length += length;
 805
 806         /* So, what's going on in the loop below?
 807          *
 808          * We use calculated fragment length to generate chained skb,
 809          * each of segments is IP fragment ready for sending to network after
 810          * adding appropriate IP header.
 811          */
 812
 813         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
 814                 goto alloc_new_skb;
 815
 816         while (length > 0) {
 817                 /* Check if the remaining data fits into current packet. */
 818                 copy = mtu - skb->len;
 819                 if (copy < length)
 820                         copy = maxfraglen - skb->len;
 821                 if (copy <= 0) {
 822                         char *data;
 823                         unsigned int datalen;
 824                         unsigned int fraglen;
 825                         unsigned int fraggap;
 826                         unsigned int alloclen;
 827                         struct sk_buff *skb_prev;
 828 alloc_new_skb:
 829                         skb_prev = skb;
 830                         if (skb_prev)
 831                                 fraggap = skb_prev->len - maxfraglen;
 832                         else
 833                                 fraggap = 0;
 834
 835                         /*
 836                          * If remaining data exceeds the mtu,
 837                          * we know we need more fragment(s).
 838                          */
 839                         datalen = length + fraggap;
 840                         if (datalen > mtu - fragheaderlen)
 841                                 datalen = maxfraglen - fragheaderlen;
 842                         fraglen = datalen + fragheaderlen;
 843
 844                         if ((flags & MSG_MORE) &&
 845                             !(rt->u.dst.dev->features&NETIF_F_SG))
 846                                 alloclen = mtu;
 847                         else
 848                                 alloclen = datalen + fragheaderlen;
 849
 850                         /* The last fragment gets additional space at tail.
 851                          * Note, with MSG_MORE we overallocate on fragments,
 852                          * because we have no idea what fragment will be
 853                          * the last.
 854                          */
 855                         if (datalen == length)
 856                                 alloclen += rt->u.dst.trailer_len;
 857
 858                         if (transhdrlen) {
 859                                 skb = sock_alloc_send_skb(sk,
 860                                                 alloclen + hh_len + 15,
 861                                                 (flags & MSG_DONTWAIT), &err);
 862                         } else {
 863                                 skb = NULL;
 864                                 if (atomic_read(&sk->sk_wmem_alloc) <=
 865                                     2 * sk->sk_sndbuf)
 866                                         skb = sock_wmalloc(sk,
 867                                                            alloclen + hh_len + 15, 1,
 868                                                            sk->sk_allocation);
 869                                 if (unlikely(skb == NULL))
 870                                         err = -ENOBUFS;
 871                         }
 872                         if (skb == NULL)
 873                                 goto error;
 874
 875                         /*
 876                          *      Fill in the control structures
 877                          */
 878                         skb->ip_summed = csummode;
 879                         skb->csum = 0;
 880                         skb_reserve(skb, hh_len);
 881
 882                         /*
 883                          *      Find where to start putting bytes.
 884                          */
 885                         data = skb_put(skb, fraglen);
 886                         skb->nh.raw = data + exthdrlen;
 887                         data += fragheaderlen;
 888                         skb->h.raw = data + exthdrlen;
 889
 890                         if (fraggap) {
 891                                 skb->csum = skb_copy_and_csum_bits(
 892                                         skb_prev, maxfraglen,
 893                                         data + transhdrlen, fraggap, 0);
 894                                 skb_prev->csum = csum_sub(skb_prev->csum,
 895                                                           skb->csum);
 896                                 data += fraggap;
 897                                 skb_trim(skb_prev, maxfraglen);
 898                         }
 899
 900                         copy = datalen - transhdrlen - fraggap;
 901                         if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
 902                                 err = -EFAULT;
 903                                 kfree_skb(skb);
 904                                 goto error;
 905                         }
 906
 907                         offset += copy;
 908                         length -= datalen - fraggap;
 909                         transhdrlen = 0;
 910                         exthdrlen = 0;
 911                         csummode = CHECKSUM_NONE;
 912
 913                         /*
 914                          * Put the packet on the pending queue.
 915                          */
 916                         __skb_queue_tail(&sk->sk_write_queue, skb);
 917                         continue;
 918                 }
 919
 920                 if (copy > length)
 921                         copy = length;
 922
 923                 if (!(rt->u.dst.dev->features&NETIF_F_SG)) {
 924                         unsigned int off;
 925
 926                         off = skb->len;
 927                         if (getfrag(from, skb_put(skb, copy),
 928                                         offset, copy, off, skb) < 0) {
 929                                 __skb_trim(skb, off);
 930                                 err = -EFAULT;
 931                                 goto error;
 932                         }
 933                 } else {
 934                         int i = skb_shinfo(skb)->nr_frags;
 935                         skb_frag_t *frag = &skb_shinfo(skb)->frags[i-1];
 936                         struct page *page = sk->sk_sndmsg_page;
 937                         int off = sk->sk_sndmsg_off;
 938                         unsigned int left;
 939
 940                         if (page && (left = PAGE_SIZE - off) > 0) {
 941                                 if (copy >= left)
 942                                         copy = left;
 943                                 if (page != frag->page) {
 944                                         if (i == MAX_SKB_FRAGS) {
 945                                                 err = -EMSGSIZE;
 946                                                 goto error;
 947                                         }
 948                                         get_page(page);
 949                                         skb_fill_page_desc(skb, i, page, sk->sk_sndmsg_off, 0);
 950                                         frag = &skb_shinfo(skb)->frags[i];
 951                                 }
 952                         } else if (i < MAX_SKB_FRAGS) {
 953                                 if (copy > PAGE_SIZE)
 954                                         copy = PAGE_SIZE;
 955                                 page = alloc_pages(sk->sk_allocation, 0);
 956                                 if (page == NULL)  {
 957                                         err = -ENOMEM;
 958                                         goto error;
 959                                 }
 960                                 sk->sk_sndmsg_page = page;
 961                                 sk->sk_sndmsg_off = 0;
 962
 963                                 skb_fill_page_desc(skb, i, page, 0, 0);
 964                                 frag = &skb_shinfo(skb)->frags[i];
 965                                 skb->truesize += PAGE_SIZE;
 966                                 atomic_add(PAGE_SIZE, &sk->sk_wmem_alloc);
 967                         } else {
 968                                 err = -EMSGSIZE;
 969                                 goto error;
 970                         }
 971                         if (getfrag(from, page_address(frag->page)+frag->page_offset+frag->size, offset, copy, skb->len, skb) < 0) {
 972                                 err = -EFAULT;
 973                                 goto error;
 974                         }
 975                         sk->sk_sndmsg_off += copy;
 976                         frag->size += copy;
 977                         skb->len += copy;
 978                         skb->data_len += copy;
 979                 }
 980                 offset += copy;
 981                 length -= copy;
 982         }
 983
 984         return 0;
 985
 986 error:
 987         inet->cork.length -= length;
 988         IP_INC_STATS(IPSTATS_MIB_OUTDISCARDS);
 989         return err;
 990 }
 991
 992 ssize_t ip_append_page(struct sock *sk, struct page *page,
 993                        int offset, size_t size, int flags)
 994 {
 995         struct inet_sock *inet = inet_sk(sk);
 996         struct sk_buff *skb;
 997         struct rtable *rt;
 998         struct ip_options *opt = NULL;
 999         int hh_len;
1000         int mtu;
1001         int len;
1002         int err;
1003         unsigned int maxfraglen, fragheaderlen, fraggap;
1004
1005         if (inet->hdrincl)
1006                 return -EPERM;
1007
1008         if (flags&MSG_PROBE)
1009                 return 0;
1010
1011         if (skb_queue_empty(&sk->sk_write_queue))
1012                 return -EINVAL;
1013
1014         rt = inet->cork.rt;
1015         if (inet->cork.flags & IPCORK_OPT)
1016                 opt = inet->cork.opt;
1017
1018         if (!(rt->u.dst.dev->features&NETIF_F_SG))
1019                 return -EOPNOTSUPP;
1020
1021         hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
1022         mtu = inet->cork.fragsize;
1023
1024         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
1025         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
1026
1027         if (inet->cork.length + size > 0xFFFF - fragheaderlen) {
1028                 ip_local_error(sk, EMSGSIZE, rt->rt_dst, inet->dport, mtu);
1029                 return -EMSGSIZE;
1030         }
1031
1032         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
1033                 return -EINVAL;
1034
1035         inet->cork.length += size;
1036
1037         while (size > 0) {
1038                 int i;
1039
1040                 /* Check if the remaining data fits into current packet. */
1041                 len = mtu - skb->len;
1042                 if (len < size)
1043                         len = maxfraglen - skb->len;
1044                 if (len <= 0) {
1045                         struct sk_buff *skb_prev;
1046                         char *data;
1047                         struct iphdr *iph;
1048                         int alloclen;
1049
1050                         skb_prev = skb;
1051                         if (skb_prev)
1052                                 fraggap = skb_prev->len - maxfraglen;
1053                         else
1054                                 fraggap = 0;
1055
1056                         alloclen = fragheaderlen + hh_len + fraggap + 15;
1057                         skb = sock_wmalloc(sk, alloclen, 1, sk->sk_allocation);
1058                         if (unlikely(!skb)) {
1059                                 err = -ENOBUFS;
1060                                 goto error;
1061                         }
1062
1063                         /*
1064                          *      Fill in the control structures
1065                          */
1066                         skb->ip_summed = CHECKSUM_NONE;
1067                         skb->csum = 0;
1068                         skb_reserve(skb, hh_len);
1069
1070                         /*
1071                          *      Find where to start putting bytes.
1072                          */
1073                         data = skb_put(skb, fragheaderlen + fraggap);
1074                         skb->nh.iph = iph = (struct iphdr *)data;
1075                         data += fragheaderlen;
1076                         skb->h.raw = data;
1077
1078                         if (fraggap) {
1079                                 skb->csum = skb_copy_and_csum_bits(
1080                                         skb_prev, maxfraglen,
1081                                         data, fraggap, 0);
1082                                 skb_prev->csum = csum_sub(skb_prev->csum,
1083                                                           skb->csum);
1084                                 skb_trim(skb_prev, maxfraglen);
1085                         }
1086
1087                         /*
1088                          * Put the packet on the pending queue.
1089                          */
1090                         __skb_queue_tail(&sk->sk_write_queue, skb);
1091                         continue;
1092                 }
1093
1094                 i = skb_shinfo(skb)->nr_frags;
1095                 if (len > size)
1096                         len = size;
1097                 if (skb_can_coalesce(skb, i, page, offset)) {
1098                         skb_shinfo(skb)->frags[i-1].size += len;
1099                 } else if (i < MAX_SKB_FRAGS) {
1100                         get_page(page);
1101                         skb_fill_page_desc(skb, i, page, offset, len);
1102                 } else {
1103                         err = -EMSGSIZE;
1104                         goto error;
1105                 }
1106
1107                 if (skb->ip_summed == CHECKSUM_NONE) {
1108                         unsigned int csum;
1109                         csum = csum_page(page, offset, len);
1110                         skb->csum = csum_block_add(skb->csum, csum, skb->len);
1111                 }
1112
1113                 skb->len += len;
1114                 skb->data_len += len;
1115                 offset += len;
1116                 size -= len;
1117         }
1118         return 0;
1119
1120 error:
1121         inet->cork.length -= size;
1122         IP_INC_STATS(IPSTATS_MIB_OUTDISCARDS);
1123         return err;
1124 }
1125
1126 /*
1127  *      Combined all pending IP fragments on the socket as one IP datagram
1128  *      and push them out.
1129  */
1130 int ip_push_pending_frames(struct sock *sk)
1131 {
1132         struct sk_buff *skb, *tmp_skb;
1133         struct sk_buff **tail_skb;
1134         struct inet_sock *inet = inet_sk(sk);
1135         struct ip_options *opt = NULL;
1136         struct rtable *rt = inet->cork.rt;
1137         struct iphdr *iph;
1138         int df = 0;
1139         __u8 ttl;
1140         int err = 0;
1141
1142         if ((skb = __skb_dequeue(&sk->sk_write_queue)) == NULL)
1143                 goto out;
1144         tail_skb = &(skb_shinfo(skb)->frag_list);
1145
1146         /* move skb->data to ip header from ext header */
1147         if (skb->data < skb->nh.raw)
1148                 __skb_pull(skb, skb->nh.raw - skb->data);
1149         while ((tmp_skb = __skb_dequeue(&sk->sk_write_queue)) != NULL) {
1150                 __skb_pull(tmp_skb, skb->h.raw - skb->nh.raw);
1151                 *tail_skb = tmp_skb;
1152                 tail_skb = &(tmp_skb->next);
1153                 skb->len += tmp_skb->len;
1154                 skb->data_len += tmp_skb->len;
1155                 skb->truesize += tmp_skb->truesize;
1156                 __sock_put(tmp_skb->sk);
1157                 tmp_skb->destructor = NULL;
1158                 tmp_skb->sk = NULL;
1159         }
1160
1161         /* Unless user demanded real pmtu discovery (IP_PMTUDISC_DO), we allow
1162          * to fragment the frame generated here. No matter, what transforms
1163          * how transforms change size of the packet, it will come out.
1164          */
1165         if (inet->pmtudisc != IP_PMTUDISC_DO)
1166                 skb->local_df = 1;
1167
1168         /* DF bit is set when we want to see DF on outgoing frames.
1169          * If local_df is set too, we still allow to fragment this frame
1170          * locally. */
1171         if (inet->pmtudisc == IP_PMTUDISC_DO ||
1172             (skb->len <= dst_mtu(&rt->u.dst) &&
1173              ip_dont_fragment(sk, &rt->u.dst)))
1174                 df = htons(IP_DF);
1175
1176         if (inet->cork.flags & IPCORK_OPT)
1177                 opt = inet->cork.opt;
1178
1179         if (rt->rt_type == RTN_MULTICAST)
1180                 ttl = inet->mc_ttl;
1181         else
1182                 ttl = ip_select_ttl(inet, &rt->u.dst);
1183
1184         iph = (struct iphdr *)skb->data;
1185         iph->version = 4;
1186         iph->ihl = 5;
1187         if (opt) {
1188                 iph->ihl += opt->optlen>>2;
1189                 ip_options_build(skb, opt, inet->cork.addr, rt, 0);
1190         }
1191         iph->tos = inet->tos;
1192         iph->tot_len = htons(skb->len);
1193         iph->frag_off = df;
1194         if (!df) {
1195                 __ip_select_ident(iph, &rt->u.dst, 0);
1196         } else {
1197                 iph->id = htons(inet->id++);
1198         }
1199         iph->ttl = ttl;
1200         iph->protocol = sk->sk_protocol;
1201         iph->saddr = rt->rt_src;
1202         iph->daddr = rt->rt_dst;
1203         ip_send_check(iph);
1204
1205         skb->priority = sk->sk_priority;
1206         skb->dst = dst_clone(&rt->u.dst);
1207
1208         /* Netfilter gets whole the not fragmented skb. */
1209         err = NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, skb, NULL,
1210                       skb->dst->dev, dst_output);
1211         if (err) {
1212                 if (err > 0)
1213                         err = inet->recverr ? net_xmit_errno(err) : 0;
1214                 if (err)
1215                         goto error;
1216         }
1217
1218 out:
1219         inet->cork.flags &= ~IPCORK_OPT;
1220         if (inet->cork.opt) {
1221                 kfree(inet->cork.opt);
1222                 inet->cork.opt = NULL;
1223         }
1224         if (inet->cork.rt) {
1225                 ip_rt_put(inet->cork.rt);
1226                 inet->cork.rt = NULL;
1227         }
1228         return err;
1229
1230 error:
1231         IP_INC_STATS(IPSTATS_MIB_OUTDISCARDS);
1232         goto out;
1233 }
1234
1235 /*
1236  *      Throw away all pending data on the socket.
1237  */
1238 void ip_flush_pending_frames(struct sock *sk)
1239 {
1240         struct inet_sock *inet = inet_sk(sk);
1241         struct sk_buff *skb;
1242
1243         while ((skb = __skb_dequeue_tail(&sk->sk_write_queue)) != NULL)
1244                 kfree_skb(skb);
1245
1246         inet->cork.flags &= ~IPCORK_OPT;
1247         if (inet->cork.opt) {
1248                 kfree(inet->cork.opt);
1249                 inet->cork.opt = NULL;
1250         }
1251         if (inet->cork.rt) {
1252                 ip_rt_put(inet->cork.rt);
1253                 inet->cork.rt = NULL;
1254         }
1255 }
1256
1257
1258 /*
1259  *      Fetch data from kernel space and fill in checksum if needed.
1260  */
1261 static int ip_reply_glue_bits(void *dptr, char *to, int offset,
1262                               int len, int odd, struct sk_buff *skb)
1263 {
1264         unsigned int csum;
1265
1266         csum = csum_partial_copy_nocheck(dptr+offset, to, len, 0);
1267         skb->csum = csum_block_add(skb->csum, csum, odd);
1268         return 0;
1269 }
1270
1271 /*
1272  *      Generic function to send a packet as reply to another packet.
1273  *      Used to send TCP resets so far. ICMP should use this function too.
1274  *
1275  *      Should run single threaded per socket because it uses the sock
1276  *      structure to pass arguments.
1277  *
1278  *      LATER: switch from ip_build_xmit to ip_append_*
1279  */
1280 void ip_send_reply(struct sock *sk, struct sk_buff *skb, struct ip_reply_arg *arg,
1281                    unsigned int len)
1282 {
1283         struct inet_sock *inet = inet_sk(sk);
1284         struct {
1285                 struct ip_options       opt;
1286                 char                    data[40];
1287         } replyopts;
1288         struct ipcm_cookie ipc;
1289         u32 daddr;
1290         struct rtable *rt = (struct rtable*)skb->dst;
1291
1292         if (ip_options_echo(&replyopts.opt, skb))
1293                 return;
1294
1295         daddr = ipc.addr = rt->rt_src;
1296         ipc.opt = NULL;
1297
1298         if (replyopts.opt.optlen) {
1299                 ipc.opt = &replyopts.opt;
1300
1301                 if (ipc.opt->srr)
1302                         daddr = replyopts.opt.faddr;
1303         }
1304
1305         {
1306                 struct flowi fl = { .nl_u = { .ip4_u =
1307                                               { .daddr = daddr,
1308                                                 .saddr = rt->rt_spec_dst,
1309                                                 .tos = RT_TOS(skb->nh.iph->tos) } },
1310                                     /* Not quite clean, but right. */
1311                                     .uli_u = { .ports =
1312                                                { .sport = skb->h.th->dest,
1313                                                  .dport = skb->h.th->source } },
1314                                     .proto = sk->sk_protocol };
1315                 if (ip_route_output_key(&rt, &fl))
1316                         return;
1317         }
1318
1319         /* And let IP do all the hard work.
1320
1321            This chunk is not reenterable, hence spinlock.
1322            Note that it uses the fact, that this function is called
1323            with locally disabled BH and that sk cannot be already spinlocked.
1324          */
1325         bh_lock_sock(sk);
1326         inet->tos = skb->nh.iph->tos;
1327         sk->sk_priority = skb->priority;
1328         sk->sk_protocol = skb->nh.iph->protocol;
1329         ip_append_data(sk, ip_reply_glue_bits, arg->iov->iov_base, len, 0,
1330                        &ipc, rt, MSG_DONTWAIT);
1331         if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {
1332                 if (arg->csumoffset >= 0)
1333                         *((u16 *)skb->h.raw + arg->csumoffset) = csum_fold(csum_add(skb->csum, arg->csum));
1334                 skb->ip_summed = CHECKSUM_NONE;
1335                 ip_push_pending_frames(sk);
1336         }
1337
1338         bh_unlock_sock(sk);
1339
1340         ip_rt_put(rt);
1341 }
1342
1343 /*
1344  *      IP protocol layer initialiser
1345  */
1346
1347 static struct packet_type ip_packet_type = {
1348         .type = __constant_htons(ETH_P_IP),
1349         .func = ip_rcv,
1350 };
1351
1352 /*
1353  *      IP registers the packet type and then calls the subprotocol initialisers
1354  */
1355
1356 void __init ip_init(void)
1357 {
1358         dev_add_pack(&ip_packet_type);
1359
1360         ip_rt_init();
1361         inet_initpeers();
1362
1363 #if defined(CONFIG_IP_MULTICAST) && defined(CONFIG_PROC_FS)
1364         igmp_mc_proc_init();
1365 #endif
1366 }
1367
1368 EXPORT_SYMBOL(ip_finish_output);
1369 EXPORT_SYMBOL(ip_fragment);
1370 EXPORT_SYMBOL(ip_generic_getfrag);
1371 EXPORT_SYMBOL(ip_queue_xmit);
1372 EXPORT_SYMBOL(ip_send_check);
1373
1374 #ifdef CONFIG_SYSCTL
1375 EXPORT_SYMBOL(sysctl_ip_default_ttl);
1376 #endif