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                 if (unlikely(!rt))
 817                         return -EFAULT;
 818                 /*
 819                  * We steal reference to this route, caller should not release it
 820                  */
 821                 *rtp = NULL;
 822                 inet->cork.fragsize = mtu = inet->pmtudisc == IP_PMTUDISC_PROBE ?
 823                                             rt->u.dst.dev->mtu :
 824                                             dst_mtu(rt->u.dst.path);
 825                 inet->cork.dst = &rt->u.dst;
 826                 inet->cork.length = 0;
 827                 sk->sk_sndmsg_page = NULL;
 828                 sk->sk_sndmsg_off = 0;
 829                 if ((exthdrlen = rt->u.dst.header_len) != 0) {
 830                         length += exthdrlen;
 831                         transhdrlen += exthdrlen;
 832                 }
 833         } else {
 834                 rt = (struct rtable *)inet->cork.dst;
 835                 if (inet->cork.flags & IPCORK_OPT)
 836                         opt = inet->cork.opt;
 837
 838                 transhdrlen = 0;
 839                 exthdrlen = 0;
 840                 mtu = inet->cork.fragsize;
 841         }
 842         hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
 843
 844         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
 845         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
 846
 847         if (inet->cork.length + length > 0xFFFF - fragheaderlen) {
 848                 ip_local_error(sk, EMSGSIZE, rt->rt_dst, inet->dport, mtu-exthdrlen);
 849                 return -EMSGSIZE;
 850         }
 851
 852         /*
 853          * transhdrlen > 0 means that this is the first fragment and we wish
 854          * it won't be fragmented in the future.
 855          */
 856         if (transhdrlen &&
 857             length + fragheaderlen <= mtu &&
 858             rt->u.dst.dev->features & NETIF_F_V4_CSUM &&
 859             !exthdrlen)
 860                 csummode = CHECKSUM_PARTIAL;
 861
 862         inet->cork.length += length;
 863         if (((length> mtu) || !skb_queue_empty(&sk->sk_write_queue)) &&
 864             (sk->sk_protocol == IPPROTO_UDP) &&
 865             (rt->u.dst.dev->features & NETIF_F_UFO)) {
 866                 err = ip_ufo_append_data(sk, getfrag, from, length, hh_len,
 867                                          fragheaderlen, transhdrlen, mtu,
 868                                          flags);
 869                 if (err)
 870                         goto error;
 871                 return 0;
 872         }
 873
 874         /* So, what's going on in the loop below?
 875          *
 876          * We use calculated fragment length to generate chained skb,
 877          * each of segments is IP fragment ready for sending to network after
 878          * adding appropriate IP header.
 879          */
 880
 881         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
 882                 goto alloc_new_skb;
 883
 884         while (length > 0) {
 885                 /* Check if the remaining data fits into current packet. */
 886                 copy = mtu - skb->len;
 887                 if (copy < length)
 888                         copy = maxfraglen - skb->len;
 889                 if (copy <= 0) {
 890                         char *data;
 891                         unsigned int datalen;
 892                         unsigned int fraglen;
 893                         unsigned int fraggap;
 894                         unsigned int alloclen;
 895                         struct sk_buff *skb_prev;
 896 alloc_new_skb:
 897                         skb_prev = skb;
 898                         if (skb_prev)
 899                                 fraggap = skb_prev->len - maxfraglen;
 900                         else
 901                                 fraggap = 0;
 902
 903                         /*
 904                          * If remaining data exceeds the mtu,
 905                          * we know we need more fragment(s).
 906                          */
 907                         datalen = length + fraggap;
 908                         if (datalen > mtu - fragheaderlen)
 909                                 datalen = maxfraglen - fragheaderlen;
 910                         fraglen = datalen + fragheaderlen;
 911
 912                         if ((flags & MSG_MORE) &&
 913                             !(rt->u.dst.dev->features&NETIF_F_SG))
 914                                 alloclen = mtu;
 915                         else
 916                                 alloclen = datalen + fragheaderlen;
 917
 918                         /* The last fragment gets additional space at tail.
 919                          * Note, with MSG_MORE we overallocate on fragments,
 920                          * because we have no idea what fragment will be
 921                          * the last.
 922                          */
 923                         if (datalen == length + fraggap)
 924                                 alloclen += rt->u.dst.trailer_len;
 925
 926                         if (transhdrlen) {
 927                                 skb = sock_alloc_send_skb(sk,
 928                                                 alloclen + hh_len + 15,
 929                                                 (flags & MSG_DONTWAIT), &err);
 930                         } else {
 931                                 skb = NULL;
 932                                 if (atomic_read(&sk->sk_wmem_alloc) <=
 933                                     2 * sk->sk_sndbuf)
 934                                         skb = sock_wmalloc(sk,
 935                                                            alloclen + hh_len + 15, 1,
 936                                                            sk->sk_allocation);
 937                                 if (unlikely(skb == NULL))
 938                                         err = -ENOBUFS;
 939                                 else
 940                                         /* only the initial fragment is
 941                                            time stamped */
 942                                         ipc->shtx.flags = 0;
 943                         }
 944                         if (skb == NULL)
 945                                 goto error;
 946
 947                         /*
 948                          *      Fill in the control structures
 949                          */
 950                         skb->ip_summed = csummode;
 951                         skb->csum = 0;
 952                         skb_reserve(skb, hh_len);
 953                         *skb_tx(skb) = ipc->shtx;
 954
 955                         /*
 956                          *      Find where to start putting bytes.
 957                          */
 958                         data = skb_put(skb, fraglen);
 959                         skb_set_network_header(skb, exthdrlen);
 960                         skb->transport_header = (skb->network_header +
 961                                                  fragheaderlen);
 962                         data += fragheaderlen;
 963
 964                         if (fraggap) {
 965                                 skb->csum = skb_copy_and_csum_bits(
 966                                         skb_prev, maxfraglen,
 967                                         data + transhdrlen, fraggap, 0);
 968                                 skb_prev->csum = csum_sub(skb_prev->csum,
 969                                                           skb->csum);
 970                                 data += fraggap;
 971                                 pskb_trim_unique(skb_prev, maxfraglen);
 972                         }
 973
 974                         copy = datalen - transhdrlen - fraggap;
 975                         if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
 976                                 err = -EFAULT;
 977                                 kfree_skb(skb);
 978                                 goto error;
 979                         }
 980
 981                         offset += copy;
 982                         length -= datalen - fraggap;
 983                         transhdrlen = 0;
 984                         exthdrlen = 0;
 985                         csummode = CHECKSUM_NONE;
 986
 987                         /*
 988                          * Put the packet on the pending queue.
 989                          */
 990                         __skb_queue_tail(&sk->sk_write_queue, skb);
 991                         continue;
 992                 }
 993
 994                 if (copy > length)
 995                         copy = length;
 996
 997                 if (!(rt->u.dst.dev->features&NETIF_F_SG)) {
 998                         unsigned int off;
 999
1000                         off = skb->len;
1001                         if (getfrag(from, skb_put(skb, copy),
1002                                         offset, copy, off, skb) < 0) {
1003                                 __skb_trim(skb, off);
1004                                 err = -EFAULT;
1005                                 goto error;
1006                         }
1007                 } else {
1008                         int i = skb_shinfo(skb)->nr_frags;
1009                         skb_frag_t *frag = &skb_shinfo(skb)->frags[i-1];
1010                         struct page *page = sk->sk_sndmsg_page;
1011                         int off = sk->sk_sndmsg_off;
1012                         unsigned int left;
1013
1014                         if (page && (left = PAGE_SIZE - off) > 0) {
1015                                 if (copy >= left)
1016                                         copy = left;
1017                                 if (page != frag->page) {
1018                                         if (i == MAX_SKB_FRAGS) {
1019                                                 err = -EMSGSIZE;
1020                                                 goto error;
1021                                         }
1022                                         get_page(page);
1023                                         skb_fill_page_desc(skb, i, page, sk->sk_sndmsg_off, 0);
1024                                         frag = &skb_shinfo(skb)->frags[i];
1025                                 }
1026                         } else if (i < MAX_SKB_FRAGS) {
1027                                 if (copy > PAGE_SIZE)
1028                                         copy = PAGE_SIZE;
1029                                 page = alloc_pages(sk->sk_allocation, 0);
1030                                 if (page == NULL)  {
1031                                         err = -ENOMEM;
1032                                         goto error;
1033                                 }
1034                                 sk->sk_sndmsg_page = page;
1035                                 sk->sk_sndmsg_off = 0;
1036
1037                                 skb_fill_page_desc(skb, i, page, 0, 0);
1038                                 frag = &skb_shinfo(skb)->frags[i];
1039                         } else {
1040                                 err = -EMSGSIZE;
1041                                 goto error;
1042                         }
1043                         if (getfrag(from, page_address(frag->page)+frag->page_offset+frag->size, offset, copy, skb->len, skb) < 0) {
1044                                 err = -EFAULT;
1045                                 goto error;
1046                         }
1047                         sk->sk_sndmsg_off += copy;
1048                         frag->size += copy;
1049                         skb->len += copy;
1050                         skb->data_len += copy;
1051                         skb->truesize += copy;
1052                         atomic_add(copy, &sk->sk_wmem_alloc);
1053                 }
1054                 offset += copy;
1055                 length -= copy;
1056         }
1057
1058         return 0;
1059
1060 error:
1061         inet->cork.length -= length;
1062         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1063         return err;
1064 }
1065
1066 ssize_t ip_append_page(struct sock *sk, struct page *page,
1067                        int offset, size_t size, int flags)
1068 {
1069         struct inet_sock *inet = inet_sk(sk);
1070         struct sk_buff *skb;
1071         struct rtable *rt;
1072         struct ip_options *opt = NULL;
1073         int hh_len;
1074         int mtu;
1075         int len;
1076         int err;
1077         unsigned int maxfraglen, fragheaderlen, fraggap;
1078
1079         if (inet->hdrincl)
1080                 return -EPERM;
1081
1082         if (flags&MSG_PROBE)
1083                 return 0;
1084
1085         if (skb_queue_empty(&sk->sk_write_queue))
1086                 return -EINVAL;
1087
1088         rt = (struct rtable *)inet->cork.dst;
1089         if (inet->cork.flags & IPCORK_OPT)
1090                 opt = inet->cork.opt;
1091
1092         if (!(rt->u.dst.dev->features&NETIF_F_SG))
1093                 return -EOPNOTSUPP;
1094
1095         hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
1096         mtu = inet->cork.fragsize;
1097
1098         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
1099         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
1100
1101         if (inet->cork.length + size > 0xFFFF - fragheaderlen) {
1102                 ip_local_error(sk, EMSGSIZE, rt->rt_dst, inet->dport, mtu);
1103                 return -EMSGSIZE;
1104         }
1105
1106         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
1107                 return -EINVAL;
1108
1109         inet->cork.length += size;
1110         if ((sk->sk_protocol == IPPROTO_UDP) &&
1111             (rt->u.dst.dev->features & NETIF_F_UFO)) {
1112                 skb_shinfo(skb)->gso_size = mtu - fragheaderlen;
1113                 skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
1114         }
1115
1116
1117         while (size > 0) {
1118                 int i;
1119
1120                 if (skb_is_gso(skb))
1121                         len = size;
1122                 else {
1123
1124                         /* Check if the remaining data fits into current packet. */
1125                         len = mtu - skb->len;
1126                         if (len < size)
1127                                 len = maxfraglen - skb->len;
1128                 }
1129                 if (len <= 0) {
1130                         struct sk_buff *skb_prev;
1131                         int alloclen;
1132
1133                         skb_prev = skb;
1134                         fraggap = skb_prev->len - maxfraglen;
1135
1136                         alloclen = fragheaderlen + hh_len + fraggap + 15;
1137                         skb = sock_wmalloc(sk, alloclen, 1, sk->sk_allocation);
1138                         if (unlikely(!skb)) {
1139                                 err = -ENOBUFS;
1140                                 goto error;
1141                         }
1142
1143                         /*
1144                          *      Fill in the control structures
1145                          */
1146                         skb->ip_summed = CHECKSUM_NONE;
1147                         skb->csum = 0;
1148                         skb_reserve(skb, hh_len);
1149
1150                         /*
1151                          *      Find where to start putting bytes.
1152                          */
1153                         skb_put(skb, fragheaderlen + fraggap);
1154                         skb_reset_network_header(skb);
1155                         skb->transport_header = (skb->network_header +
1156                                                  fragheaderlen);
1157                         if (fraggap) {
1158                                 skb->csum = skb_copy_and_csum_bits(skb_prev,
1159                                                                    maxfraglen,
1160                                                     skb_transport_header(skb),
1161                                                                    fraggap, 0);
1162                                 skb_prev->csum = csum_sub(skb_prev->csum,
1163                                                           skb->csum);
1164                                 pskb_trim_unique(skb_prev, maxfraglen);
1165                         }
1166
1167                         /*
1168                          * Put the packet on the pending queue.
1169                          */
1170                         __skb_queue_tail(&sk->sk_write_queue, skb);
1171                         continue;
1172                 }
1173
1174                 i = skb_shinfo(skb)->nr_frags;
1175                 if (len > size)
1176                         len = size;
1177                 if (skb_can_coalesce(skb, i, page, offset)) {
1178                         skb_shinfo(skb)->frags[i-1].size += len;
1179                 } else if (i < MAX_SKB_FRAGS) {
1180                         get_page(page);
1181                         skb_fill_page_desc(skb, i, page, offset, len);
1182                 } else {
1183                         err = -EMSGSIZE;
1184                         goto error;
1185                 }
1186
1187                 if (skb->ip_summed == CHECKSUM_NONE) {
1188                         __wsum csum;
1189                         csum = csum_page(page, offset, len);
1190                         skb->csum = csum_block_add(skb->csum, csum, skb->len);
1191                 }
1192
1193                 skb->len += len;
1194                 skb->data_len += len;
1195                 skb->truesize += len;
1196                 atomic_add(len, &sk->sk_wmem_alloc);
1197                 offset += len;
1198                 size -= len;
1199         }
1200         return 0;
1201
1202 error:
1203         inet->cork.length -= size;
1204         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1205         return err;
1206 }
1207
1208 static void ip_cork_release(struct inet_sock *inet)
1209 {
1210         inet->cork.flags &= ~IPCORK_OPT;
1211         kfree(inet->cork.opt);
1212         inet->cork.opt = NULL;
1213         dst_release(inet->cork.dst);
1214         inet->cork.dst = NULL;
1215 }
1216
1217 /*
1218  *      Combined all pending IP fragments on the socket as one IP datagram
1219  *      and push them out.
1220  */
1221 int ip_push_pending_frames(struct sock *sk)
1222 {
1223         struct sk_buff *skb, *tmp_skb;
1224         struct sk_buff **tail_skb;
1225         struct inet_sock *inet = inet_sk(sk);
1226         struct net *net = sock_net(sk);
1227         struct ip_options *opt = NULL;
1228         struct rtable *rt = (struct rtable *)inet->cork.dst;
1229         struct iphdr *iph;
1230         __be16 df = 0;
1231         __u8 ttl;
1232         int err = 0;
1233
1234         if ((skb = __skb_dequeue(&sk->sk_write_queue)) == NULL)
1235                 goto out;
1236         tail_skb = &(skb_shinfo(skb)->frag_list);
1237
1238         /* move skb->data to ip header from ext header */
1239         if (skb->data < skb_network_header(skb))
1240                 __skb_pull(skb, skb_network_offset(skb));
1241         while ((tmp_skb = __skb_dequeue(&sk->sk_write_queue)) != NULL) {
1242                 __skb_pull(tmp_skb, skb_network_header_len(skb));
1243                 *tail_skb = tmp_skb;
1244                 tail_skb = &(tmp_skb->next);
1245                 skb->len += tmp_skb->len;
1246                 skb->data_len += tmp_skb->len;
1247                 skb->truesize += tmp_skb->truesize;
1248                 tmp_skb->destructor = NULL;
1249                 tmp_skb->sk = NULL;
1250         }
1251
1252         /* Unless user demanded real pmtu discovery (IP_PMTUDISC_DO), we allow
1253          * to fragment the frame generated here. No matter, what transforms
1254          * how transforms change size of the packet, it will come out.
1255          */
1256         if (inet->pmtudisc < IP_PMTUDISC_DO)
1257                 skb->local_df = 1;
1258
1259         /* DF bit is set when we want to see DF on outgoing frames.
1260          * If local_df is set too, we still allow to fragment this frame
1261          * locally. */
1262         if (inet->pmtudisc >= IP_PMTUDISC_DO ||
1263             (skb->len <= dst_mtu(&rt->u.dst) &&
1264              ip_dont_fragment(sk, &rt->u.dst)))
1265                 df = htons(IP_DF);
1266
1267         if (inet->cork.flags & IPCORK_OPT)
1268                 opt = inet->cork.opt;
1269
1270         if (rt->rt_type == RTN_MULTICAST)
1271                 ttl = inet->mc_ttl;
1272         else
1273                 ttl = ip_select_ttl(inet, &rt->u.dst);
1274
1275         iph = (struct iphdr *)skb->data;
1276         iph->version = 4;
1277         iph->ihl = 5;
1278         if (opt) {
1279                 iph->ihl += opt->optlen>>2;
1280                 ip_options_build(skb, opt, inet->cork.addr, rt, 0);
1281         }
1282         iph->tos = inet->tos;
1283         iph->frag_off = df;
1284         ip_select_ident(iph, &rt->u.dst, sk);
1285         iph->ttl = ttl;
1286         iph->protocol = sk->sk_protocol;
1287         iph->saddr = rt->rt_src;
1288         iph->daddr = rt->rt_dst;
1289
1290         skb->priority = sk->sk_priority;
1291         skb->mark = sk->sk_mark;
1292         /*
1293          * Steal rt from cork.dst to avoid a pair of atomic_inc/atomic_dec
1294          * on dst refcount
1295          */
1296         inet->cork.dst = NULL;
1297         skb_dst_set(skb, &rt->u.dst);
1298
1299         if (iph->protocol == IPPROTO_ICMP)
1300                 icmp_out_count(net, ((struct icmphdr *)
1301                         skb_transport_header(skb))->type);
1302
1303         /* Netfilter gets whole the not fragmented skb. */
1304         err = ip_local_out(skb);
1305         if (err) {
1306                 if (err > 0)
1307                         err = inet->recverr ? net_xmit_errno(err) : 0;
1308                 if (err)
1309                         goto error;
1310         }
1311
1312 out:
1313         ip_cork_release(inet);
1314         return err;
1315
1316 error:
1317         IP_INC_STATS(net, IPSTATS_MIB_OUTDISCARDS);
1318         goto out;
1319 }
1320
1321 /*
1322  *      Throw away all pending data on the socket.
1323  */
1324 void ip_flush_pending_frames(struct sock *sk)
1325 {
1326         struct sk_buff *skb;
1327
1328         while ((skb = __skb_dequeue_tail(&sk->sk_write_queue)) != NULL)
1329                 kfree_skb(skb);
1330
1331         ip_cork_release(inet_sk(sk));
1332 }
1333
1334
1335 /*
1336  *      Fetch data from kernel space and fill in checksum if needed.
1337  */
1338 static int ip_reply_glue_bits(void *dptr, char *to, int offset,
1339                               int len, int odd, struct sk_buff *skb)
1340 {
1341         __wsum csum;
1342
1343         csum = csum_partial_copy_nocheck(dptr+offset, to, len, 0);
1344         skb->csum = csum_block_add(skb->csum, csum, odd);
1345         return 0;
1346 }
1347
1348 /*
1349  *      Generic function to send a packet as reply to another packet.
1350  *      Used to send TCP resets so far. ICMP should use this function too.
1351  *
1352  *      Should run single threaded per socket because it uses the sock
1353  *      structure to pass arguments.
1354  */
1355 void ip_send_reply(struct sock *sk, struct sk_buff *skb, struct ip_reply_arg *arg,
1356                    unsigned int len)
1357 {
1358         struct inet_sock *inet = inet_sk(sk);
1359         struct {
1360                 struct ip_options       opt;
1361                 char                    data[40];
1362         } replyopts;
1363         struct ipcm_cookie ipc;
1364         __be32 daddr;
1365         struct rtable *rt = skb_rtable(skb);
1366
1367         if (ip_options_echo(&replyopts.opt, skb))
1368                 return;
1369
1370         daddr = ipc.addr = rt->rt_src;
1371         ipc.opt = NULL;
1372         ipc.shtx.flags = 0;
1373
1374         if (replyopts.opt.optlen) {
1375                 ipc.opt = &replyopts.opt;
1376
1377                 if (ipc.opt->srr)
1378                         daddr = replyopts.opt.faddr;
1379         }
1380
1381         {
1382                 struct flowi fl = { .oif = arg->bound_dev_if,
1383                                     .nl_u = { .ip4_u =
1384                                               { .daddr = daddr,
1385                                                 .saddr = rt->rt_spec_dst,
1386                                                 .tos = RT_TOS(ip_hdr(skb)->tos) } },
1387                                     /* Not quite clean, but right. */
1388                                     .uli_u = { .ports =
1389                                                { .sport = tcp_hdr(skb)->dest,
1390                                                  .dport = tcp_hdr(skb)->source } },
1391                                     .proto = sk->sk_protocol,
1392                                     .flags = ip_reply_arg_flowi_flags(arg) };
1393                 security_skb_classify_flow(skb, &fl);
1394                 if (ip_route_output_key(sock_net(sk), &rt, &fl))
1395                         return;
1396         }
1397
1398         /* And let IP do all the hard work.
1399
1400            This chunk is not reenterable, hence spinlock.
1401            Note that it uses the fact, that this function is called
1402            with locally disabled BH and that sk cannot be already spinlocked.
1403          */
1404         bh_lock_sock(sk);
1405         inet->tos = ip_hdr(skb)->tos;
1406         sk->sk_priority = skb->priority;
1407         sk->sk_protocol = ip_hdr(skb)->protocol;
1408         sk->sk_bound_dev_if = arg->bound_dev_if;
1409         ip_append_data(sk, ip_reply_glue_bits, arg->iov->iov_base, len, 0,
1410                        &ipc, &rt, MSG_DONTWAIT);
1411         if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {
1412                 if (arg->csumoffset >= 0)
1413                         *((__sum16 *)skb_transport_header(skb) +
1414                           arg->csumoffset) = csum_fold(csum_add(skb->csum,
1415                                                                 arg->csum));
1416                 skb->ip_summed = CHECKSUM_NONE;
1417                 ip_push_pending_frames(sk);
1418         }
1419
1420         bh_unlock_sock(sk);
1421
1422         ip_rt_put(rt);
1423 }
1424
1425 void __init ip_init(void)
1426 {
1427         ip_rt_init();
1428         inet_initpeers();
1429
1430 #if defined(CONFIG_IP_MULTICAST) && defined(CONFIG_PROC_FS)
1431         igmp_mc_proc_init();
1432 #endif
1433 }
1434
1435 EXPORT_SYMBOL(ip_generic_getfrag);
1436 EXPORT_SYMBOL(ip_queue_xmit);
1437 EXPORT_SYMBOL(ip_send_check);