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  * Authors:     Ross Biro
   9  *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
  10  *              Donald Becker, <becker@super.org>
  11  *              Alan Cox, <Alan.Cox@linux.org>
  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  *              Hirokazu Takahashi, <taka@valinux.co.jp>
  17  *
  18  *      See ip_input.c for original log
  19  *
  20  *      Fixes:
  21  *              Alan Cox        :       Missing nonblock feature in ip_build_xmit.
  22  *              Mike Kilburn    :       htons() missing in ip_build_xmit.
  23  *              Bradford Johnson:       Fix faulty handling of some frames when
  24  *                                      no route is found.
  25  *              Alexander Demenshin:    Missing sk/skb free in ip_queue_xmit
  26  *                                      (in case if packet not accepted by
  27  *                                      output firewall rules)
  28  *              Mike McLagan    :       Routing by source
  29  *              Alexey Kuznetsov:       use new route cache
  30  *              Andi Kleen:             Fix broken PMTU recovery and remove
  31  *                                      some redundant tests.
  32  *      Vitaly E. Lavrov        :       Transparent proxy revived after year coma.
  33  *              Andi Kleen      :       Replace ip_reply with ip_send_reply.
  34  *              Andi Kleen      :       Split fast and slow ip_build_xmit path
  35  *                                      for decreased register pressure on x86
  36  *                                      and more readibility.
  37  *              Marc Boucher    :       When call_out_firewall returns FW_QUEUE,
  38  *                                      silently drop skb instead of failing with -EPERM.
  39  *              Detlev Wengorz  :       Copy protocol for fragments.
  40  *              Hirokazu Takahashi:     HW checksumming for outgoing UDP
  41  *                                      datagrams.
  42  *              Hirokazu Takahashi:     sendfile() on UDP works now.
  43  */
  44
  45 #include <asm/uaccess.h>
  46 #include <asm/system.h>
  47 #include <linux/module.h>
  48 #include <linux/types.h>
  49 #include <linux/kernel.h>
  50 #include <linux/mm.h>
  51 #include <linux/string.h>
  52 #include <linux/errno.h>
  53 #include <linux/highmem.h>
  54
  55 #include <linux/socket.h>
  56 #include <linux/sockios.h>
  57 #include <linux/in.h>
  58 #include <linux/inet.h>
  59 #include <linux/netdevice.h>
  60 #include <linux/etherdevice.h>
  61 #include <linux/proc_fs.h>
  62 #include <linux/stat.h>
  63 #include <linux/init.h>
  64
  65 #include <net/snmp.h>
  66 #include <net/ip.h>
  67 #include <net/protocol.h>
  68 #include <net/route.h>
  69 #include <net/xfrm.h>
  70 #include <linux/skbuff.h>
  71 #include <net/sock.h>
  72 #include <net/arp.h>
  73 #include <net/icmp.h>
  74 #include <net/checksum.h>
  75 #include <net/inetpeer.h>
  76 #include <linux/igmp.h>
  77 #include <linux/netfilter_ipv4.h>
  78 #include <linux/netfilter_bridge.h>
  79 #include <linux/mroute.h>
  80 #include <linux/netlink.h>
  81 #include <linux/tcp.h>
  82
  83 int sysctl_ip_default_ttl __read_mostly = IPDEFTTL;
  84
  85 /* Generate a checksum for an outgoing IP datagram. */
  86 __inline__ void ip_send_check(struct iphdr *iph)
  87 {
  88         iph->check = 0;
  89         iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
  90 }
  91
  92 int __ip_local_out(struct sk_buff *skb)
  93 {
  94         struct iphdr *iph = ip_hdr(skb);
  95
  96         iph->tot_len = htons(skb->len);
  97         ip_send_check(iph);
  98         return nf_hook(PF_INET, NF_INET_LOCAL_OUT, skb, NULL, skb_dst(skb)->dev,
  99                        dst_output);
 100 }
 101
 102 int ip_local_out(struct sk_buff *skb)
 103 {
 104         int err;
 105
 106         err = __ip_local_out(skb);
 107         if (likely(err == 1))
 108                 err = dst_output(skb);
 109
 110         return err;
 111 }
 112 EXPORT_SYMBOL_GPL(ip_local_out);
 113
 114 /* dev_loopback_xmit for use with netfilter. */
 115 static int ip_dev_loopback_xmit(struct sk_buff *newskb)
 116 {
 117         skb_reset_mac_header(newskb);
 118         __skb_pull(newskb, skb_network_offset(newskb));
 119         newskb->pkt_type = PACKET_LOOPBACK;
 120         newskb->ip_summed = CHECKSUM_UNNECESSARY;
 121         WARN_ON(!skb_dst(newskb));
 122         netif_rx(newskb);
 123         return 0;
 124 }
 125
 126 static inline int ip_select_ttl(struct inet_sock *inet, struct dst_entry *dst)
 127 {
 128         int ttl = inet->uc_ttl;
 129
 130         if (ttl < 0)
 131                 ttl = dst_metric(dst, RTAX_HOPLIMIT);
 132         return ttl;
 133 }
 134
 135 /*
 136  *              Add an ip header to a skbuff and send it out.
 137  *
 138  */
 139 int ip_build_and_send_pkt(struct sk_buff *skb, struct sock *sk,
 140                           __be32 saddr, __be32 daddr, struct ip_options *opt)
 141 {
 142         struct inet_sock *inet = inet_sk(sk);
 143         struct rtable *rt = skb_rtable(skb);
 144         struct iphdr *iph;
 145
 146         /* Build the IP header. */
 147         skb_push(skb, sizeof(struct iphdr) + (opt ? opt->optlen : 0));
 148         skb_reset_network_header(skb);
 149         iph = ip_hdr(skb);
 150         iph->version  = 4;
 151         iph->ihl      = 5;
 152         iph->tos      = inet->tos;
 153         if (ip_dont_fragment(sk, &rt->u.dst))
 154                 iph->frag_off = htons(IP_DF);
 155         else
 156                 iph->frag_off = 0;
 157         iph->ttl      = ip_select_ttl(inet, &rt->u.dst);
 158         iph->daddr    = rt->rt_dst;
 159         iph->saddr    = rt->rt_src;
 160         iph->protocol = sk->sk_protocol;
 161         ip_select_ident(iph, &rt->u.dst, sk);
 162
 163         if (opt && opt->optlen) {
 164                 iph->ihl += opt->optlen>>2;
 165                 ip_options_build(skb, opt, daddr, rt, 0);
 166         }
 167
 168         skb->priority = sk->sk_priority;
 169         skb->mark = sk->sk_mark;
 170
 171         /* Send it out. */
 172         return ip_local_out(skb);
 173 }
 174
 175 EXPORT_SYMBOL_GPL(ip_build_and_send_pkt);
 176
 177 static inline int ip_finish_output2(struct sk_buff *skb)
 178 {
 179         struct dst_entry *dst = skb_dst(skb);
 180         struct rtable *rt = (struct rtable *)dst;
 181         struct net_device *dev = dst->dev;
 182         unsigned int hh_len = LL_RESERVED_SPACE(dev);
 183
 184         if (rt->rt_type == RTN_MULTICAST) {
 185                 IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUTMCAST, skb->len);
 186         } else if (rt->rt_type == RTN_BROADCAST)
 187                 IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUTBCAST, skb->len);
 188
 189         /* Be paranoid, rather than too clever. */
 190         if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) {
 191                 struct sk_buff *skb2;
 192
 193                 skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev));
 194                 if (skb2 == NULL) {
 195                         kfree_skb(skb);
 196                         return -ENOMEM;
 197                 }
 198                 if (skb->sk)
 199                         skb_set_owner_w(skb2, skb->sk);
 200                 kfree_skb(skb);
 201                 skb = skb2;
 202         }
 203
 204         if (dst->hh)
 205                 return neigh_hh_output(dst->hh, skb);
 206         else if (dst->neighbour)
 207                 return dst->neighbour->output(skb);
 208
 209         if (net_ratelimit())
 210                 printk(KERN_DEBUG "ip_finish_output2: No header cache and no neighbour!\n");
 211         kfree_skb(skb);
 212         return -EINVAL;
 213 }
 214
 215 static inline int ip_skb_dst_mtu(struct sk_buff *skb)
 216 {
 217         struct inet_sock *inet = skb->sk ? inet_sk(skb->sk) : NULL;
 218
 219         return (inet && inet->pmtudisc == IP_PMTUDISC_PROBE) ?
 220                skb_dst(skb)->dev->mtu : dst_mtu(skb_dst(skb));
 221 }
 222
 223 static int ip_finish_output(struct sk_buff *skb)
 224 {
 225 #if defined(CONFIG_NETFILTER) && defined(CONFIG_XFRM)
 226         /* Policy lookup after SNAT yielded a new policy */
 227         if (skb_dst(skb)->xfrm != NULL) {
 228                 IPCB(skb)->flags |= IPSKB_REROUTED;
 229                 return dst_output(skb);
 230         }
 231 #endif
 232         if (skb->len > ip_skb_dst_mtu(skb) && !skb_is_gso(skb))
 233                 return ip_fragment(skb, ip_finish_output2);
 234         else
 235                 return ip_finish_output2(skb);
 236 }
 237
 238 int ip_mc_output(struct sk_buff *skb)
 239 {
 240         struct sock *sk = skb->sk;
 241         struct rtable *rt = skb_rtable(skb);
 242         struct net_device *dev = rt->u.dst.dev;
 243
 244         /*
 245          *      If the indicated interface is up and running, send the packet.
 246          */
 247         IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUT, skb->len);
 248
 249         skb->dev = dev;
 250         skb->protocol = htons(ETH_P_IP);
 251
 252         /*
 253          *      Multicasts are looped back for other local users
 254          */
 255
 256         if (rt->rt_flags&RTCF_MULTICAST) {
 257                 if ((!sk || inet_sk(sk)->mc_loop)
 258 #ifdef CONFIG_IP_MROUTE
 259                 /* Small optimization: do not loopback not local frames,
 260                    which returned after forwarding; they will be  dropped
 261                    by ip_mr_input in any case.
 262                    Note, that local frames are looped back to be delivered
 263                    to local recipients.
 264
 265                    This check is duplicated in ip_mr_input at the moment.
 266                  */
 267                     && ((rt->rt_flags&RTCF_LOCAL) || !(IPCB(skb)->flags&IPSKB_FORWARDED))
 268 #endif
 269                 ) {
 270                         struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
 271                         if (newskb)
 272                                 NF_HOOK(PF_INET, NF_INET_POST_ROUTING, newskb,
 273                                         NULL, newskb->dev,
 274                                         ip_dev_loopback_xmit);
 275                 }
 276
 277                 /* Multicasts with ttl 0 must not go beyond the host */
 278
 279                 if (ip_hdr(skb)->ttl == 0) {
 280                         kfree_skb(skb);
 281                         return 0;
 282                 }
 283         }
 284
 285         if (rt->rt_flags&RTCF_BROADCAST) {
 286                 struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
 287                 if (newskb)
 288                         NF_HOOK(PF_INET, NF_INET_POST_ROUTING, newskb, NULL,
 289                                 newskb->dev, ip_dev_loopback_xmit);
 290         }
 291
 292         return NF_HOOK_COND(PF_INET, NF_INET_POST_ROUTING, skb, NULL, skb->dev,
 293                             ip_finish_output,
 294                             !(IPCB(skb)->flags & IPSKB_REROUTED));
 295 }
 296
 297 int ip_output(struct sk_buff *skb)
 298 {
 299         struct net_device *dev = skb_dst(skb)->dev;
 300
 301         IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUT, skb->len);
 302
 303         skb->dev = dev;
 304         skb->protocol = htons(ETH_P_IP);
 305
 306         return NF_HOOK_COND(PF_INET, NF_INET_POST_ROUTING, skb, NULL, dev,
 307                             ip_finish_output,
 308                             !(IPCB(skb)->flags & IPSKB_REROUTED));
 309 }
 310
 311 int ip_queue_xmit(struct sk_buff *skb, int ipfragok)
 312 {
 313         struct sock *sk = skb->sk;
 314         struct inet_sock *inet = inet_sk(sk);
 315         struct ip_options *opt = inet->opt;
 316         struct rtable *rt;
 317         struct iphdr *iph;
 318
 319         /* Skip all of this if the packet is already routed,
 320          * f.e. by something like SCTP.
 321          */
 322         rt = skb_rtable(skb);
 323         if (rt != NULL)
 324                 goto packet_routed;
 325
 326         /* Make sure we can route this packet. */
 327         rt = (struct rtable *)__sk_dst_check(sk, 0);
 328         if (rt == NULL) {
 329                 __be32 daddr;
 330
 331                 /* Use correct destination address if we have options. */
 332                 daddr = inet->daddr;
 333                 if(opt && opt->srr)
 334                         daddr = opt->faddr;
 335
 336                 {
 337                         struct flowi fl = { .oif = sk->sk_bound_dev_if,
 338                                             .nl_u = { .ip4_u =
 339                                                       { .daddr = daddr,
 340                                                         .saddr = inet->saddr,
 341                                                         .tos = RT_CONN_FLAGS(sk) } },
 342                                             .proto = sk->sk_protocol,
 343                                             .flags = inet_sk_flowi_flags(sk),
 344                                             .uli_u = { .ports =
 345                                                        { .sport = inet->sport,
 346                                                          .dport = inet->dport } } };
 347
 348                         /* If this fails, retransmit mechanism of transport layer will
 349                          * keep trying until route appears or the connection times
 350                          * itself out.
 351                          */
 352                         security_sk_classify_flow(sk, &fl);
 353                         if (ip_route_output_flow(sock_net(sk), &rt, &fl, sk, 0))
 354                                 goto no_route;
 355                 }
 356                 sk_setup_caps(sk, &rt->u.dst);
 357         }
 358         skb_dst_set(skb, dst_clone(&rt->u.dst));
 359
 360 packet_routed:
 361         if (opt && opt->is_strictroute && rt->rt_dst != rt->rt_gateway)
 362                 goto no_route;
 363
 364         /* OK, we know where to send it, allocate and build IP header. */
 365         skb_push(skb, sizeof(struct iphdr) + (opt ? opt->optlen : 0));
 366         skb_reset_network_header(skb);
 367         iph = ip_hdr(skb);
 368         *((__be16 *)iph) = htons((4 << 12) | (5 << 8) | (inet->tos & 0xff));
 369         if (ip_dont_fragment(sk, &rt->u.dst) && !ipfragok)
 370                 iph->frag_off = htons(IP_DF);
 371         else
 372                 iph->frag_off = 0;
 373         iph->ttl      = ip_select_ttl(inet, &rt->u.dst);
 374         iph->protocol = sk->sk_protocol;
 375         iph->saddr    = rt->rt_src;
 376         iph->daddr    = rt->rt_dst;
 377         /* Transport layer set skb->h.foo itself. */
 378
 379         if (opt && opt->optlen) {
 380                 iph->ihl += opt->optlen >> 2;
 381                 ip_options_build(skb, opt, inet->daddr, rt, 0);
 382         }
 383
 384         ip_select_ident_more(iph, &rt->u.dst, sk,
 385                              (skb_shinfo(skb)->gso_segs ?: 1) - 1);
 386
 387         skb->priority = sk->sk_priority;
 388         skb->mark = sk->sk_mark;
 389
 390         return ip_local_out(skb);
 391
 392 no_route:
 393         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);
 394         kfree_skb(skb);
 395         return -EHOSTUNREACH;
 396 }
 397
 398
 399 static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
 400 {
 401         to->pkt_type = from->pkt_type;
 402         to->priority = from->priority;
 403         to->protocol = from->protocol;
 404         skb_dst_drop(to);
 405         skb_dst_set(to, dst_clone(skb_dst(from)));
 406         to->dev = from->dev;
 407         to->mark = from->mark;
 408
 409         /* Copy the flags to each fragment. */
 410         IPCB(to)->flags = IPCB(from)->flags;
 411
 412 #ifdef CONFIG_NET_SCHED
 413         to->tc_index = from->tc_index;
 414 #endif
 415         nf_copy(to, from);
 416 #if defined(CONFIG_NETFILTER_XT_TARGET_TRACE) || \
 417     defined(CONFIG_NETFILTER_XT_TARGET_TRACE_MODULE)
 418         to->nf_trace = from->nf_trace;
 419 #endif
 420 #if defined(CONFIG_IP_VS) || defined(CONFIG_IP_VS_MODULE)
 421         to->ipvs_property = from->ipvs_property;
 422 #endif
 423         skb_copy_secmark(to, from);
 424 }
 425
 426 /*
 427  *      This IP datagram is too large to be sent in one piece.  Break it up into
 428  *      smaller pieces (each of size equal to IP header plus
 429  *      a block of the data of the original IP data part) that will yet fit in a
 430  *      single device frame, and queue such a frame for sending.
 431  */
 432
 433 int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
 434 {
 435         struct iphdr *iph;
 436         int raw = 0;
 437         int ptr;
 438         struct net_device *dev;
 439         struct sk_buff *skb2;
 440         unsigned int mtu, hlen, left, len, ll_rs, pad;
 441         int offset;
 442         __be16 not_last_frag;
 443         struct rtable *rt = skb_rtable(skb);
 444         int err = 0;
 445
 446         dev = rt->u.dst.dev;
 447
 448         /*
 449          *      Point into the IP datagram header.
 450          */
 451
 452         iph = ip_hdr(skb);
 453
 454         if (unlikely((iph->frag_off & htons(IP_DF)) && !skb->local_df)) {
 455                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
 456                 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
 457                           htonl(ip_skb_dst_mtu(skb)));
 458                 kfree_skb(skb);
 459                 return -EMSGSIZE;
 460         }
 461
 462         /*
 463          *      Setup starting values.
 464          */
 465
 466         hlen = iph->ihl * 4;
 467         mtu = dst_mtu(&rt->u.dst) - hlen;       /* Size of data space */
 468         IPCB(skb)->flags |= IPSKB_FRAG_COMPLETE;
 469
 470         /* When frag_list is given, use it. First, check its validity:
 471          * some transformers could create wrong frag_list or break existing
 472          * one, it is not prohibited. In this case fall back to copying.
 473          *
 474          * LATER: this step can be merged to real generation of fragments,
 475          * we can switch to copy when see the first bad fragment.
 476          */
 477         if (skb_has_frags(skb)) {
 478                 struct sk_buff *frag;
 479                 int first_len = skb_pagelen(skb);
 480                 int truesizes = 0;
 481
 482                 if (first_len - hlen > mtu ||
 483                     ((first_len - hlen) & 7) ||
 484                     (iph->frag_off & htons(IP_MF|IP_OFFSET)) ||
 485                     skb_cloned(skb))
 486                         goto slow_path;
 487
 488                 skb_walk_frags(skb, frag) {
 489                         /* Correct geometry. */
 490                         if (frag->len > mtu ||
 491                             ((frag->len & 7) && frag->next) ||
 492                             skb_headroom(frag) < hlen)
 493                             goto slow_path;
 494
 495                         /* Partially cloned skb? */
 496                         if (skb_shared(frag))
 497                                 goto slow_path;
 498
 499                         BUG_ON(frag->sk);
 500                         if (skb->sk) {
 501                                 frag->sk = skb->sk;
 502                                 frag->destructor = sock_wfree;
 503                                 truesizes += frag->truesize;
 504                         }
 505                 }
 506
 507                 /* Everything is OK. Generate! */
 508
 509                 err = 0;
 510                 offset = 0;
 511                 frag = skb_shinfo(skb)->frag_list;
 512                 skb_frag_list_init(skb);
 513                 skb->data_len = first_len - skb_headlen(skb);
 514                 skb->truesize -= truesizes;
 515                 skb->len = first_len;
 516                 iph->tot_len = htons(first_len);
 517                 iph->frag_off = htons(IP_MF);
 518                 ip_send_check(iph);
 519
 520                 for (;;) {
 521                         /* Prepare header of the next frame,
 522                          * before previous one went down. */
 523                         if (frag) {
 524                                 frag->ip_summed = CHECKSUM_NONE;
 525                                 skb_reset_transport_header(frag);
 526                                 __skb_push(frag, hlen);
 527                                 skb_reset_network_header(frag);
 528                                 memcpy(skb_network_header(frag), iph, hlen);
 529                                 iph = ip_hdr(frag);
 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)
 545                                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGCREATES);
 546                         if (err || !frag)
 547                                 break;
 548
 549                         skb = frag;
 550                         frag = skb->next;
 551                         skb->next = NULL;
 552                 }
 553
 554                 if (err == 0) {
 555                         IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGOKS);
 556                         return 0;
 557                 }
 558
 559                 while (frag) {
 560                         skb = frag->next;
 561                         kfree_skb(frag);
 562                         frag = skb;
 563                 }
 564                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
 565                 return err;
 566         }
 567
 568 slow_path:
 569         left = skb->len - hlen;         /* Space per frame */
 570         ptr = raw + hlen;               /* Where to start from */
 571
 572         /* for bridged IP traffic encapsulated inside f.e. a vlan header,
 573          * we need to make room for the encapsulating header
 574          */
 575         pad = nf_bridge_pad(skb);
 576         ll_rs = LL_RESERVED_SPACE_EXTRA(rt->u.dst.dev, pad);
 577         mtu -= pad;
 578
 579         /*
 580          *      Fragment the datagram.
 581          */
 582
 583         offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3;
 584         not_last_frag = iph->frag_off & htons(IP_MF);
 585
 586         /*
 587          *      Keep copying data until we run out.
 588          */
 589
 590         while (left > 0) {
 591                 len = left;
 592                 /* IF: it doesn't fit, use 'mtu' - the data space left */
 593                 if (len > mtu)
 594                         len = mtu;
 595                 /* IF: we are not sending upto and including the packet end
 596                    then align the next start on an eight byte boundary */
 597                 if (len < left) {
 598                         len &= ~7;
 599                 }
 600                 /*
 601                  *      Allocate buffer.
 602                  */
 603
 604                 if ((skb2 = alloc_skb(len+hlen+ll_rs, GFP_ATOMIC)) == NULL) {
 605                         NETDEBUG(KERN_INFO "IP: frag: no memory for new fragment!\n");
 606                         err = -ENOMEM;
 607                         goto fail;
 608                 }
 609
 610                 /*
 611                  *      Set up data on packet
 612                  */
 613
 614                 ip_copy_metadata(skb2, skb);
 615                 skb_reserve(skb2, ll_rs);
 616                 skb_put(skb2, len + hlen);
 617                 skb_reset_network_header(skb2);
 618                 skb2->transport_header = skb2->network_header + hlen;
 619
 620                 /*
 621                  *      Charge the memory for the fragment to any owner
 622                  *      it might possess
 623                  */
 624
 625                 if (skb->sk)
 626                         skb_set_owner_w(skb2, skb->sk);
 627
 628                 /*
 629                  *      Copy the packet header into the new buffer.
 630                  */
 631
 632                 skb_copy_from_linear_data(skb, skb_network_header(skb2), hlen);
 633
 634                 /*
 635                  *      Copy a block of the IP datagram.
 636                  */
 637                 if (skb_copy_bits(skb, ptr, skb_transport_header(skb2), len))
 638                         BUG();
 639                 left -= len;
 640
 641                 /*
 642                  *      Fill in the new header fields.
 643                  */
 644                 iph = ip_hdr(skb2);
 645                 iph->frag_off = htons((offset >> 3));
 646
 647                 /* ANK: dirty, but effective trick. Upgrade options only if
 648                  * the segment to be fragmented was THE FIRST (otherwise,
 649                  * options are already fixed) and make it ONCE
 650                  * on the initial skb, so that all the following fragments
 651                  * will inherit fixed options.
 652                  */
 653                 if (offset == 0)
 654                         ip_options_fragment(skb);
 655
 656                 /*
 657                  *      Added AC : If we are fragmenting a fragment that's not the
 658                  *                 last fragment then keep MF on each bit
 659                  */
 660                 if (left > 0 || not_last_frag)
 661                         iph->frag_off |= htons(IP_MF);
 662                 ptr += len;
 663                 offset += len;
 664
 665                 /*
 666                  *      Put this fragment into the sending queue.
 667                  */
 668                 iph->tot_len = htons(len + hlen);
 669
 670                 ip_send_check(iph);
 671
 672                 err = output(skb2);
 673                 if (err)
 674                         goto fail;
 675
 676                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGCREATES);
 677         }
 678         kfree_skb(skb);
 679         IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGOKS);
 680         return err;
 681
 682 fail:
 683         kfree_skb(skb);
 684         IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
 685         return err;
 686 }
 687
 688 EXPORT_SYMBOL(ip_fragment);
 689
 690 int
 691 ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
 692 {
 693         struct iovec *iov = from;
 694
 695         if (skb->ip_summed == CHECKSUM_PARTIAL) {
 696                 if (memcpy_fromiovecend(to, iov, offset, len) < 0)
 697                         return -EFAULT;
 698         } else {
 699                 __wsum csum = 0;
 700                 if (csum_partial_copy_fromiovecend(to, iov, offset, len, &csum) < 0)
 701                         return -EFAULT;
 702                 skb->csum = csum_block_add(skb->csum, csum, odd);
 703         }
 704         return 0;
 705 }
 706
 707 static inline __wsum
 708 csum_page(struct page *page, int offset, int copy)
 709 {
 710         char *kaddr;
 711         __wsum csum;
 712         kaddr = kmap(page);
 713         csum = csum_partial(kaddr + offset, copy, 0);
 714         kunmap(page);
 715         return csum;
 716 }
 717
 718 static inline int ip_ufo_append_data(struct sock *sk,
 719                         int getfrag(void *from, char *to, int offset, int len,
 720                                int odd, struct sk_buff *skb),
 721                         void *from, int length, int hh_len, int fragheaderlen,
 722                         int transhdrlen, int mtu, unsigned int flags)
 723 {
 724         struct sk_buff *skb;
 725         int err;
 726
 727         /* There is support for UDP fragmentation offload by network
 728          * device, so create one single skb packet containing complete
 729          * udp datagram
 730          */
 731         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL) {
 732                 skb = sock_alloc_send_skb(sk,
 733                         hh_len + fragheaderlen + transhdrlen + 20,
 734                         (flags & MSG_DONTWAIT), &err);
 735
 736                 if (skb == NULL)
 737                         return err;
 738
 739                 /* reserve space for Hardware header */
 740                 skb_reserve(skb, hh_len);
 741
 742                 /* create space for UDP/IP header */
 743                 skb_put(skb, fragheaderlen + transhdrlen);
 744
 745                 /* initialize network header pointer */
 746                 skb_reset_network_header(skb);
 747
 748                 /* initialize protocol header pointer */
 749                 skb->transport_header = skb->network_header + fragheaderlen;
 750
 751                 skb->ip_summed = CHECKSUM_PARTIAL;
 752                 skb->csum = 0;
 753                 sk->sk_sndmsg_off = 0;
 754
 755                 /* specify the length of each IP datagram fragment */
 756                 skb_shinfo(skb)->gso_size = mtu - fragheaderlen;
 757                 skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
 758                 __skb_queue_tail(&sk->sk_write_queue, skb);
 759         }
 760
 761         return skb_append_datato_frags(sk, skb, getfrag, from,
 762                                        (length - transhdrlen));
 763 }
 764
 765 /*
 766  *      ip_append_data() and ip_append_page() can make one large IP datagram
 767  *      from many pieces of data. Each pieces will be holded on the socket
 768  *      until ip_push_pending_frames() is called. Each piece can be a page
 769  *      or non-page data.
 770  *
 771  *      Not only UDP, other transport protocols - e.g. raw sockets - can use
 772  *      this interface potentially.
 773  *
 774  *      LATER: length must be adjusted by pad at tail, when it is required.
 775  */
 776 int ip_append_data(struct sock *sk,
 777                    int getfrag(void *from, char *to, int offset, int len,
 778                                int odd, struct sk_buff *skb),
 779                    void *from, int length, int transhdrlen,
 780                    struct ipcm_cookie *ipc, struct rtable **rtp,
 781                    unsigned int flags)
 782 {
 783         struct inet_sock *inet = inet_sk(sk);
 784         struct sk_buff *skb;
 785
 786         struct ip_options *opt = NULL;
 787         int hh_len;
 788         int exthdrlen;
 789         int mtu;
 790         int copy;
 791         int err;
 792         int offset = 0;
 793         unsigned int maxfraglen, fragheaderlen;
 794         int csummode = CHECKSUM_NONE;
 795         struct rtable *rt;
 796
 797         if (flags&MSG_PROBE)
 798                 return 0;
 799
 800         if (skb_queue_empty(&sk->sk_write_queue)) {
 801                 /*
 802                  * setup for corking.
 803                  */
 804                 opt = ipc->opt;
 805                 if (opt) {
 806                         if (inet->cork.opt == NULL) {
 807                                 inet->cork.opt = kmalloc(sizeof(struct ip_options) + 40, sk->sk_allocation);
 808                                 if (unlikely(inet->cork.opt == NULL))
 809                                         return -ENOBUFS;
 810                         }
 811                         memcpy(inet->cork.opt, opt, sizeof(struct ip_options)+opt->optlen);
 812                         inet->cork.flags |= IPCORK_OPT;
 813                         inet->cork.addr = ipc->addr;
 814                 }
 815                 rt = *rtp;
 816                 /*
 817                  * We steal reference to this route, caller should not release it
 818                  */
 819                 *rtp = NULL;
 820                 inet->cork.fragsize = mtu = inet->pmtudisc == IP_PMTUDISC_PROBE ?
 821                                             rt->u.dst.dev->mtu :
 822                                             dst_mtu(rt->u.dst.path);
 823                 inet->cork.dst = &rt->u.dst;
 824                 inet->cork.length = 0;
 825                 sk->sk_sndmsg_page = NULL;
 826                 sk->sk_sndmsg_off = 0;
 827                 if ((exthdrlen = rt->u.dst.header_len) != 0) {
 828                         length += exthdrlen;
 829                         transhdrlen += exthdrlen;
 830                 }
 831         } else {
 832                 rt = (struct rtable *)inet->cork.dst;
 833                 if (inet->cork.flags & IPCORK_OPT)
 834                         opt = inet->cork.opt;
 835
 836                 transhdrlen = 0;
 837                 exthdrlen = 0;
 838                 mtu = inet->cork.fragsize;
 839         }
 840         hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
 841
 842         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
 843         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
 844
 845         if (inet->cork.length + length > 0xFFFF - fragheaderlen) {
 846                 ip_local_error(sk, EMSGSIZE, rt->rt_dst, inet->dport, mtu-exthdrlen);
 847                 return -EMSGSIZE;
 848         }
 849
 850         /*
 851          * transhdrlen > 0 means that this is the first fragment and we wish
 852          * it won't be fragmented in the future.
 853          */
 854         if (transhdrlen &&
 855             length + fragheaderlen <= mtu &&
 856             rt->u.dst.dev->features & NETIF_F_V4_CSUM &&
 857             !exthdrlen)
 858                 csummode = CHECKSUM_PARTIAL;
 859
 860         inet->cork.length += length;
 861         if (((length> mtu) || !skb_queue_empty(&sk->sk_write_queue)) &&
 862             (sk->sk_protocol == IPPROTO_UDP) &&
 863             (rt->u.dst.dev->features & NETIF_F_UFO)) {
 864                 err = ip_ufo_append_data(sk, getfrag, from, length, hh_len,
 865                                          fragheaderlen, transhdrlen, mtu,
 866                                          flags);
 867                 if (err)
 868                         goto error;
 869                 return 0;
 870         }
 871
 872         /* So, what's going on in the loop below?
 873          *
 874          * We use calculated fragment length to generate chained skb,
 875          * each of segments is IP fragment ready for sending to network after
 876          * adding appropriate IP header.
 877          */
 878
 879         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
 880                 goto alloc_new_skb;
 881
 882         while (length > 0) {
 883                 /* Check if the remaining data fits into current packet. */
 884                 copy = mtu - skb->len;
 885                 if (copy < length)
 886                         copy = maxfraglen - skb->len;
 887                 if (copy <= 0) {
 888                         char *data;
 889                         unsigned int datalen;
 890                         unsigned int fraglen;
 891                         unsigned int fraggap;
 892                         unsigned int alloclen;
 893                         struct sk_buff *skb_prev;
 894 alloc_new_skb:
 895                         skb_prev = skb;
 896                         if (skb_prev)
 897                                 fraggap = skb_prev->len - maxfraglen;
 898                         else
 899                                 fraggap = 0;
 900
 901                         /*
 902                          * If remaining data exceeds the mtu,
 903                          * we know we need more fragment(s).
 904                          */
 905                         datalen = length + fraggap;
 906                         if (datalen > mtu - fragheaderlen)
 907                                 datalen = maxfraglen - fragheaderlen;
 908                         fraglen = datalen + fragheaderlen;
 909
 910                         if ((flags & MSG_MORE) &&
 911                             !(rt->u.dst.dev->features&NETIF_F_SG))
 912                                 alloclen = mtu;
 913                         else
 914                                 alloclen = datalen + fragheaderlen;
 915
 916                         /* The last fragment gets additional space at tail.
 917                          * Note, with MSG_MORE we overallocate on fragments,
 918                          * because we have no idea what fragment will be
 919                          * the last.
 920                          */
 921                         if (datalen == length + fraggap)
 922                                 alloclen += rt->u.dst.trailer_len;
 923
 924                         if (transhdrlen) {
 925                                 skb = sock_alloc_send_skb(sk,
 926                                                 alloclen + hh_len + 15,
 927                                                 (flags & MSG_DONTWAIT), &err);
 928                         } else {
 929                                 skb = NULL;
 930                                 if (atomic_read(&sk->sk_wmem_alloc) <=
 931                                     2 * sk->sk_sndbuf)
 932                                         skb = sock_wmalloc(sk,
 933                                                            alloclen + hh_len + 15, 1,
 934                                                            sk->sk_allocation);
 935                                 if (unlikely(skb == NULL))
 936                                         err = -ENOBUFS;
 937                                 else
 938                                         /* only the initial fragment is
 939                                            time stamped */
 940                                         ipc->shtx.flags = 0;
 941                         }
 942                         if (skb == NULL)
 943                                 goto error;
 944
 945                         /*
 946                          *      Fill in the control structures
 947                          */
 948                         skb->ip_summed = csummode;
 949                         skb->csum = 0;
 950                         skb_reserve(skb, hh_len);
 951                         *skb_tx(skb) = ipc->shtx;
 952
 953                         /*
 954                          *      Find where to start putting bytes.
 955                          */
 956                         data = skb_put(skb, fraglen);
 957                         skb_set_network_header(skb, exthdrlen);
 958                         skb->transport_header = (skb->network_header +
 959                                                  fragheaderlen);
 960                         data += fragheaderlen;
 961
 962                         if (fraggap) {
 963                                 skb->csum = skb_copy_and_csum_bits(
 964                                         skb_prev, maxfraglen,
 965                                         data + transhdrlen, fraggap, 0);
 966                                 skb_prev->csum = csum_sub(skb_prev->csum,
 967                                                           skb->csum);
 968                                 data += fraggap;
 969                                 pskb_trim_unique(skb_prev, maxfraglen);
 970                         }
 971
 972                         copy = datalen - transhdrlen - fraggap;
 973                         if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
 974                                 err = -EFAULT;
 975                                 kfree_skb(skb);
 976                                 goto error;
 977                         }
 978
 979                         offset += copy;
 980                         length -= datalen - fraggap;
 981                         transhdrlen = 0;
 982                         exthdrlen = 0;
 983                         csummode = CHECKSUM_NONE;
 984
 985                         /*
 986                          * Put the packet on the pending queue.
 987                          */
 988                         __skb_queue_tail(&sk->sk_write_queue, skb);
 989                         continue;
 990                 }
 991
 992                 if (copy > length)
 993                         copy = length;
 994
 995                 if (!(rt->u.dst.dev->features&NETIF_F_SG)) {
 996                         unsigned int off;
 997
 998                         off = skb->len;
 999                         if (getfrag(from, skb_put(skb, copy),
1000                                         offset, copy, off, skb) < 0) {
1001                                 __skb_trim(skb, off);
1002                                 err = -EFAULT;
1003                                 goto error;
1004                         }
1005                 } else {
1006                         int i = skb_shinfo(skb)->nr_frags;
1007                         skb_frag_t *frag = &skb_shinfo(skb)->frags[i-1];
1008                         struct page *page = sk->sk_sndmsg_page;
1009                         int off = sk->sk_sndmsg_off;
1010                         unsigned int left;
1011
1012                         if (page && (left = PAGE_SIZE - off) > 0) {
1013                                 if (copy >= left)
1014                                         copy = left;
1015                                 if (page != frag->page) {
1016                                         if (i == MAX_SKB_FRAGS) {
1017                                                 err = -EMSGSIZE;
1018                                                 goto error;
1019                                         }
1020                                         get_page(page);
1021                                         skb_fill_page_desc(skb, i, page, sk->sk_sndmsg_off, 0);
1022                                         frag = &skb_shinfo(skb)->frags[i];
1023                                 }
1024                         } else if (i < MAX_SKB_FRAGS) {
1025                                 if (copy > PAGE_SIZE)
1026                                         copy = PAGE_SIZE;
1027                                 page = alloc_pages(sk->sk_allocation, 0);
1028                                 if (page == NULL)  {
1029                                         err = -ENOMEM;
1030                                         goto error;
1031                                 }
1032                                 sk->sk_sndmsg_page = page;
1033                                 sk->sk_sndmsg_off = 0;
1034
1035                                 skb_fill_page_desc(skb, i, page, 0, 0);
1036                                 frag = &skb_shinfo(skb)->frags[i];
1037                         } else {
1038                                 err = -EMSGSIZE;
1039                                 goto error;
1040                         }
1041                         if (getfrag(from, page_address(frag->page)+frag->page_offset+frag->size, offset, copy, skb->len, skb) < 0) {
1042                                 err = -EFAULT;
1043                                 goto error;
1044                         }
1045                         sk->sk_sndmsg_off += copy;
1046                         frag->size += copy;
1047                         skb->len += copy;
1048                         skb->data_len += copy;
1049                         skb->truesize += copy;
1050                         atomic_add(copy, &sk->sk_wmem_alloc);
1051                 }
1052                 offset += copy;
1053                 length -= copy;
1054         }
1055
1056         return 0;
1057
1058 error:
1059         inet->cork.length -= length;
1060         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1061         return err;
1062 }
1063
1064 ssize_t ip_append_page(struct sock *sk, struct page *page,
1065                        int offset, size_t size, int flags)
1066 {
1067         struct inet_sock *inet = inet_sk(sk);
1068         struct sk_buff *skb;
1069         struct rtable *rt;
1070         struct ip_options *opt = NULL;
1071         int hh_len;
1072         int mtu;
1073         int len;
1074         int err;
1075         unsigned int maxfraglen, fragheaderlen, fraggap;
1076
1077         if (inet->hdrincl)
1078                 return -EPERM;
1079
1080         if (flags&MSG_PROBE)
1081                 return 0;
1082
1083         if (skb_queue_empty(&sk->sk_write_queue))
1084                 return -EINVAL;
1085
1086         rt = (struct rtable *)inet->cork.dst;
1087         if (inet->cork.flags & IPCORK_OPT)
1088                 opt = inet->cork.opt;
1089
1090         if (!(rt->u.dst.dev->features&NETIF_F_SG))
1091                 return -EOPNOTSUPP;
1092
1093         hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
1094         mtu = inet->cork.fragsize;
1095
1096         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
1097         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
1098
1099         if (inet->cork.length + size > 0xFFFF - fragheaderlen) {
1100                 ip_local_error(sk, EMSGSIZE, rt->rt_dst, inet->dport, mtu);
1101                 return -EMSGSIZE;
1102         }
1103
1104         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
1105                 return -EINVAL;
1106
1107         inet->cork.length += size;
1108         if ((sk->sk_protocol == IPPROTO_UDP) &&
1109             (rt->u.dst.dev->features & NETIF_F_UFO)) {
1110                 skb_shinfo(skb)->gso_size = mtu - fragheaderlen;
1111                 skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
1112         }
1113
1114
1115         while (size > 0) {
1116                 int i;
1117
1118                 if (skb_is_gso(skb))
1119                         len = size;
1120                 else {
1121
1122                         /* Check if the remaining data fits into current packet. */
1123                         len = mtu - skb->len;
1124                         if (len < size)
1125                                 len = maxfraglen - skb->len;
1126                 }
1127                 if (len <= 0) {
1128                         struct sk_buff *skb_prev;
1129                         int alloclen;
1130
1131                         skb_prev = skb;
1132                         fraggap = skb_prev->len - maxfraglen;
1133
1134                         alloclen = fragheaderlen + hh_len + fraggap + 15;
1135                         skb = sock_wmalloc(sk, alloclen, 1, sk->sk_allocation);
1136                         if (unlikely(!skb)) {
1137                                 err = -ENOBUFS;
1138                                 goto error;
1139                         }
1140
1141                         /*
1142                          *      Fill in the control structures
1143                          */
1144                         skb->ip_summed = CHECKSUM_NONE;
1145                         skb->csum = 0;
1146                         skb_reserve(skb, hh_len);
1147
1148                         /*
1149                          *      Find where to start putting bytes.
1150                          */
1151                         skb_put(skb, fragheaderlen + fraggap);
1152                         skb_reset_network_header(skb);
1153                         skb->transport_header = (skb->network_header +
1154                                                  fragheaderlen);
1155                         if (fraggap) {
1156                                 skb->csum = skb_copy_and_csum_bits(skb_prev,
1157                                                                    maxfraglen,
1158                                                     skb_transport_header(skb),
1159                                                                    fraggap, 0);
1160                                 skb_prev->csum = csum_sub(skb_prev->csum,
1161                                                           skb->csum);
1162                                 pskb_trim_unique(skb_prev, maxfraglen);
1163                         }
1164
1165                         /*
1166                          * Put the packet on the pending queue.
1167                          */
1168                         __skb_queue_tail(&sk->sk_write_queue, skb);
1169                         continue;
1170                 }
1171
1172                 i = skb_shinfo(skb)->nr_frags;
1173                 if (len > size)
1174                         len = size;
1175                 if (skb_can_coalesce(skb, i, page, offset)) {
1176                         skb_shinfo(skb)->frags[i-1].size += len;
1177                 } else if (i < MAX_SKB_FRAGS) {
1178                         get_page(page);
1179                         skb_fill_page_desc(skb, i, page, offset, len);
1180                 } else {
1181                         err = -EMSGSIZE;
1182                         goto error;
1183                 }
1184
1185                 if (skb->ip_summed == CHECKSUM_NONE) {
1186                         __wsum csum;
1187                         csum = csum_page(page, offset, len);
1188                         skb->csum = csum_block_add(skb->csum, csum, skb->len);
1189                 }
1190
1191                 skb->len += len;
1192                 skb->data_len += len;
1193                 skb->truesize += len;
1194                 atomic_add(len, &sk->sk_wmem_alloc);
1195                 offset += len;
1196                 size -= len;
1197         }
1198         return 0;
1199
1200 error:
1201         inet->cork.length -= size;
1202         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1203         return err;
1204 }
1205
1206 static void ip_cork_release(struct inet_sock *inet)
1207 {
1208         inet->cork.flags &= ~IPCORK_OPT;
1209         kfree(inet->cork.opt);
1210         inet->cork.opt = NULL;
1211         dst_release(inet->cork.dst);
1212         inet->cork.dst = NULL;
1213 }
1214
1215 /*
1216  *      Combined all pending IP fragments on the socket as one IP datagram
1217  *      and push them out.
1218  */
1219 int ip_push_pending_frames(struct sock *sk)
1220 {
1221         struct sk_buff *skb, *tmp_skb;
1222         struct sk_buff **tail_skb;
1223         struct inet_sock *inet = inet_sk(sk);
1224         struct net *net = sock_net(sk);
1225         struct ip_options *opt = NULL;
1226         struct rtable *rt = (struct rtable *)inet->cork.dst;
1227         struct iphdr *iph;
1228         __be16 df = 0;
1229         __u8 ttl;
1230         int err = 0;
1231
1232         if ((skb = __skb_dequeue(&sk->sk_write_queue)) == NULL)
1233                 goto out;
1234         tail_skb = &(skb_shinfo(skb)->frag_list);
1235
1236         /* move skb->data to ip header from ext header */
1237         if (skb->data < skb_network_header(skb))
1238                 __skb_pull(skb, skb_network_offset(skb));
1239         while ((tmp_skb = __skb_dequeue(&sk->sk_write_queue)) != NULL) {
1240                 __skb_pull(tmp_skb, skb_network_header_len(skb));
1241                 *tail_skb = tmp_skb;
1242                 tail_skb = &(tmp_skb->next);
1243                 skb->len += tmp_skb->len;
1244                 skb->data_len += tmp_skb->len;
1245                 skb->truesize += tmp_skb->truesize;
1246                 tmp_skb->destructor = NULL;
1247                 tmp_skb->sk = NULL;
1248         }
1249
1250         /* Unless user demanded real pmtu discovery (IP_PMTUDISC_DO), we allow
1251          * to fragment the frame generated here. No matter, what transforms
1252          * how transforms change size of the packet, it will come out.
1253          */
1254         if (inet->pmtudisc < IP_PMTUDISC_DO)
1255                 skb->local_df = 1;
1256
1257         /* DF bit is set when we want to see DF on outgoing frames.
1258          * If local_df is set too, we still allow to fragment this frame
1259          * locally. */
1260         if (inet->pmtudisc >= IP_PMTUDISC_DO ||
1261             (skb->len <= dst_mtu(&rt->u.dst) &&
1262              ip_dont_fragment(sk, &rt->u.dst)))
1263                 df = htons(IP_DF);
1264
1265         if (inet->cork.flags & IPCORK_OPT)
1266                 opt = inet->cork.opt;
1267
1268         if (rt->rt_type == RTN_MULTICAST)
1269                 ttl = inet->mc_ttl;
1270         else
1271                 ttl = ip_select_ttl(inet, &rt->u.dst);
1272
1273         iph = (struct iphdr *)skb->data;
1274         iph->version = 4;
1275         iph->ihl = 5;
1276         if (opt) {
1277                 iph->ihl += opt->optlen>>2;
1278                 ip_options_build(skb, opt, inet->cork.addr, rt, 0);
1279         }
1280         iph->tos = inet->tos;
1281         iph->frag_off = df;
1282         ip_select_ident(iph, &rt->u.dst, sk);
1283         iph->ttl = ttl;
1284         iph->protocol = sk->sk_protocol;
1285         iph->saddr = rt->rt_src;
1286         iph->daddr = rt->rt_dst;
1287
1288         skb->priority = sk->sk_priority;
1289         skb->mark = sk->sk_mark;
1290         /*
1291          * Steal rt from cork.dst to avoid a pair of atomic_inc/atomic_dec
1292          * on dst refcount
1293          */
1294         inet->cork.dst = NULL;
1295         skb_dst_set(skb, &rt->u.dst);
1296
1297         if (iph->protocol == IPPROTO_ICMP)
1298                 icmp_out_count(net, ((struct icmphdr *)
1299                         skb_transport_header(skb))->type);
1300
1301         /* Netfilter gets whole the not fragmented skb. */
1302         err = ip_local_out(skb);
1303         if (err) {
1304                 if (err > 0)
1305                         err = inet->recverr ? net_xmit_errno(err) : 0;
1306                 if (err)
1307                         goto error;
1308         }
1309
1310 out:
1311         ip_cork_release(inet);
1312         return err;
1313
1314 error:
1315         IP_INC_STATS(net, IPSTATS_MIB_OUTDISCARDS);
1316         goto out;
1317 }
1318
1319 /*
1320  *      Throw away all pending data on the socket.
1321  */
1322 void ip_flush_pending_frames(struct sock *sk)
1323 {
1324         struct sk_buff *skb;
1325
1326         while ((skb = __skb_dequeue_tail(&sk->sk_write_queue)) != NULL)
1327                 kfree_skb(skb);
1328
1329         ip_cork_release(inet_sk(sk));
1330 }
1331
1332
1333 /*
1334  *      Fetch data from kernel space and fill in checksum if needed.
1335  */
1336 static int ip_reply_glue_bits(void *dptr, char *to, int offset,
1337                               int len, int odd, struct sk_buff *skb)
1338 {
1339         __wsum csum;
1340
1341         csum = csum_partial_copy_nocheck(dptr+offset, to, len, 0);
1342         skb->csum = csum_block_add(skb->csum, csum, odd);
1343         return 0;
1344 }
1345
1346 /*
1347  *      Generic function to send a packet as reply to another packet.
1348  *      Used to send TCP resets so far. ICMP should use this function too.
1349  *
1350  *      Should run single threaded per socket because it uses the sock
1351  *      structure to pass arguments.
1352  */
1353 void ip_send_reply(struct sock *sk, struct sk_buff *skb, struct ip_reply_arg *arg,
1354                    unsigned int len)
1355 {
1356         struct inet_sock *inet = inet_sk(sk);
1357         struct {
1358                 struct ip_options       opt;
1359                 char                    data[40];
1360         } replyopts;
1361         struct ipcm_cookie ipc;
1362         __be32 daddr;
1363         struct rtable *rt = skb_rtable(skb);
1364
1365         if (ip_options_echo(&replyopts.opt, skb))
1366                 return;
1367
1368         daddr = ipc.addr = rt->rt_src;
1369         ipc.opt = NULL;
1370         ipc.shtx.flags = 0;
1371
1372         if (replyopts.opt.optlen) {
1373                 ipc.opt = &replyopts.opt;
1374
1375                 if (ipc.opt->srr)
1376                         daddr = replyopts.opt.faddr;
1377         }
1378
1379         {
1380                 struct flowi fl = { .oif = arg->bound_dev_if,
1381                                     .nl_u = { .ip4_u =
1382                                               { .daddr = daddr,
1383                                                 .saddr = rt->rt_spec_dst,
1384                                                 .tos = RT_TOS(ip_hdr(skb)->tos) } },
1385                                     /* Not quite clean, but right. */
1386                                     .uli_u = { .ports =
1387                                                { .sport = tcp_hdr(skb)->dest,
1388                                                  .dport = tcp_hdr(skb)->source } },
1389                                     .proto = sk->sk_protocol,
1390                                     .flags = ip_reply_arg_flowi_flags(arg) };
1391                 security_skb_classify_flow(skb, &fl);
1392                 if (ip_route_output_key(sock_net(sk), &rt, &fl))
1393                         return;
1394         }
1395
1396         /* And let IP do all the hard work.
1397
1398            This chunk is not reenterable, hence spinlock.
1399            Note that it uses the fact, that this function is called
1400            with locally disabled BH and that sk cannot be already spinlocked.
1401          */
1402         bh_lock_sock(sk);
1403         inet->tos = ip_hdr(skb)->tos;
1404         sk->sk_priority = skb->priority;
1405         sk->sk_protocol = ip_hdr(skb)->protocol;
1406         sk->sk_bound_dev_if = arg->bound_dev_if;
1407         ip_append_data(sk, ip_reply_glue_bits, arg->iov->iov_base, len, 0,
1408                        &ipc, &rt, MSG_DONTWAIT);
1409         if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {
1410                 if (arg->csumoffset >= 0)
1411                         *((__sum16 *)skb_transport_header(skb) +
1412                           arg->csumoffset) = csum_fold(csum_add(skb->csum,
1413                                                                 arg->csum));
1414                 skb->ip_summed = CHECKSUM_NONE;
1415                 ip_push_pending_frames(sk);
1416         }
1417
1418         bh_unlock_sock(sk);
1419
1420         ip_rt_put(rt);
1421 }
1422
1423 void __init ip_init(void)
1424 {
1425         ip_rt_init();
1426         inet_initpeers();
1427
1428 #if defined(CONFIG_IP_MULTICAST) && defined(CONFIG_PROC_FS)
1429         igmp_mc_proc_init();
1430 #endif
1431 }
1432
1433 EXPORT_SYMBOL(ip_generic_getfrag);
1434 EXPORT_SYMBOL(ip_queue_xmit);
1435 EXPORT_SYMBOL(ip_send_check);