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   1 /*
   2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
   3  *              operating system.  INET is implemented using the  BSD Socket
   4  *              interface as the means of communication with the user level.
   5  *
   6  *              The Internet Protocol (IP) 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->inet_daddr;
 333                 if(opt && opt->srr)
 334                         daddr = opt->faddr;
 335
 336                 {
 337                         struct flowi fl = { .oif = sk->sk_bound_dev_if,
 338                                             .mark = sk->sk_mark,
 339                                             .nl_u = { .ip4_u =
 340                                                       { .daddr = daddr,
 341                                                         .saddr = inet->inet_saddr,
 342                                                         .tos = RT_CONN_FLAGS(sk) } },
 343                                             .proto = sk->sk_protocol,
 344                                             .flags = inet_sk_flowi_flags(sk),
 345                                             .uli_u = { .ports =
 346                                                        { .sport = inet->inet_sport,
 347                                                          .dport = inet->inet_dport } } };
 348
 349                         /* If this fails, retransmit mechanism of transport layer will
 350                          * keep trying until route appears or the connection times
 351                          * itself out.
 352                          */
 353                         security_sk_classify_flow(sk, &fl);
 354                         if (ip_route_output_flow(sock_net(sk), &rt, &fl, sk, 0))
 355                                 goto no_route;
 356                 }
 357                 sk_setup_caps(sk, &rt->u.dst);
 358         }
 359         skb_dst_set(skb, dst_clone(&rt->u.dst));
 360
 361 packet_routed:
 362         if (opt && opt->is_strictroute && rt->rt_dst != rt->rt_gateway)
 363                 goto no_route;
 364
 365         /* OK, we know where to send it, allocate and build IP header. */
 366         skb_push(skb, sizeof(struct iphdr) + (opt ? opt->optlen : 0));
 367         skb_reset_network_header(skb);
 368         iph = ip_hdr(skb);
 369         *((__be16 *)iph) = htons((4 << 12) | (5 << 8) | (inet->tos & 0xff));
 370         if (ip_dont_fragment(sk, &rt->u.dst) && !ipfragok)
 371                 iph->frag_off = htons(IP_DF);
 372         else
 373                 iph->frag_off = 0;
 374         iph->ttl      = ip_select_ttl(inet, &rt->u.dst);
 375         iph->protocol = sk->sk_protocol;
 376         iph->saddr    = rt->rt_src;
 377         iph->daddr    = rt->rt_dst;
 378         /* Transport layer set skb->h.foo itself. */
 379
 380         if (opt && opt->optlen) {
 381                 iph->ihl += opt->optlen >> 2;
 382                 ip_options_build(skb, opt, inet->inet_daddr, rt, 0);
 383         }
 384
 385         ip_select_ident_more(iph, &rt->u.dst, sk,
 386                              (skb_shinfo(skb)->gso_segs ?: 1) - 1);
 387
 388         skb->priority = sk->sk_priority;
 389         skb->mark = sk->sk_mark;
 390
 391         return ip_local_out(skb);
 392
 393 no_route:
 394         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);
 395         kfree_skb(skb);
 396         return -EHOSTUNREACH;
 397 }
 398
 399
 400 static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
 401 {
 402         to->pkt_type = from->pkt_type;
 403         to->priority = from->priority;
 404         to->protocol = from->protocol;
 405         skb_dst_drop(to);
 406         skb_dst_set(to, dst_clone(skb_dst(from)));
 407         to->dev = from->dev;
 408         to->mark = from->mark;
 409
 410         /* Copy the flags to each fragment. */
 411         IPCB(to)->flags = IPCB(from)->flags;
 412
 413 #ifdef CONFIG_NET_SCHED
 414         to->tc_index = from->tc_index;
 415 #endif
 416         nf_copy(to, from);
 417 #if defined(CONFIG_NETFILTER_XT_TARGET_TRACE) || \
 418     defined(CONFIG_NETFILTER_XT_TARGET_TRACE_MODULE)
 419         to->nf_trace = from->nf_trace;
 420 #endif
 421 #if defined(CONFIG_IP_VS) || defined(CONFIG_IP_VS_MODULE)
 422         to->ipvs_property = from->ipvs_property;
 423 #endif
 424         skb_copy_secmark(to, from);
 425 }
 426
 427 /*
 428  *      This IP datagram is too large to be sent in one piece.  Break it up into
 429  *      smaller pieces (each of size equal to IP header plus
 430  *      a block of the data of the original IP data part) that will yet fit in a
 431  *      single device frame, and queue such a frame for sending.
 432  */
 433
 434 int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
 435 {
 436         struct iphdr *iph;
 437         int raw = 0;
 438         int ptr;
 439         struct net_device *dev;
 440         struct sk_buff *skb2;
 441         unsigned int mtu, hlen, left, len, ll_rs, pad;
 442         int offset;
 443         __be16 not_last_frag;
 444         struct rtable *rt = skb_rtable(skb);
 445         int err = 0;
 446
 447         dev = rt->u.dst.dev;
 448
 449         /*
 450          *      Point into the IP datagram header.
 451          */
 452
 453         iph = ip_hdr(skb);
 454
 455         if (unlikely((iph->frag_off & htons(IP_DF)) && !skb->local_df)) {
 456                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
 457                 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
 458                           htonl(ip_skb_dst_mtu(skb)));
 459                 kfree_skb(skb);
 460                 return -EMSGSIZE;
 461         }
 462
 463         /*
 464          *      Setup starting values.
 465          */
 466
 467         hlen = iph->ihl * 4;
 468         mtu = dst_mtu(&rt->u.dst) - hlen;       /* Size of data space */
 469         IPCB(skb)->flags |= IPSKB_FRAG_COMPLETE;
 470
 471         /* When frag_list is given, use it. First, check its validity:
 472          * some transformers could create wrong frag_list or break existing
 473          * one, it is not prohibited. In this case fall back to copying.
 474          *
 475          * LATER: this step can be merged to real generation of fragments,
 476          * we can switch to copy when see the first bad fragment.
 477          */
 478         if (skb_has_frags(skb)) {
 479                 struct sk_buff *frag;
 480                 int first_len = skb_pagelen(skb);
 481                 int truesizes = 0;
 482
 483                 if (first_len - hlen > mtu ||
 484                     ((first_len - hlen) & 7) ||
 485                     (iph->frag_off & htons(IP_MF|IP_OFFSET)) ||
 486                     skb_cloned(skb))
 487                         goto slow_path;
 488
 489                 skb_walk_frags(skb, frag) {
 490                         /* Correct geometry. */
 491                         if (frag->len > mtu ||
 492                             ((frag->len & 7) && frag->next) ||
 493                             skb_headroom(frag) < hlen)
 494                             goto slow_path;
 495
 496                         /* Partially cloned skb? */
 497                         if (skb_shared(frag))
 498                                 goto slow_path;
 499
 500                         BUG_ON(frag->sk);
 501                         if (skb->sk) {
 502                                 frag->sk = skb->sk;
 503                                 frag->destructor = sock_wfree;
 504                                 truesizes += frag->truesize;
 505                         }
 506                 }
 507
 508                 /* Everything is OK. Generate! */
 509
 510                 err = 0;
 511                 offset = 0;
 512                 frag = skb_shinfo(skb)->frag_list;
 513                 skb_frag_list_init(skb);
 514                 skb->data_len = first_len - skb_headlen(skb);
 515                 skb->truesize -= truesizes;
 516                 skb->len = first_len;
 517                 iph->tot_len = htons(first_len);
 518                 iph->frag_off = htons(IP_MF);
 519                 ip_send_check(iph);
 520
 521                 for (;;) {
 522                         /* Prepare header of the next frame,
 523                          * before previous one went down. */
 524                         if (frag) {
 525                                 frag->ip_summed = CHECKSUM_NONE;
 526                                 skb_reset_transport_header(frag);
 527                                 __skb_push(frag, hlen);
 528                                 skb_reset_network_header(frag);
 529                                 memcpy(skb_network_header(frag), iph, hlen);
 530                                 iph = ip_hdr(frag);
 531                                 iph->tot_len = htons(frag->len);
 532                                 ip_copy_metadata(frag, skb);
 533                                 if (offset == 0)
 534                                         ip_options_fragment(frag);
 535                                 offset += skb->len - hlen;
 536                                 iph->frag_off = htons(offset>>3);
 537                                 if (frag->next != NULL)
 538                                         iph->frag_off |= htons(IP_MF);
 539                                 /* Ready, complete checksum */
 540                                 ip_send_check(iph);
 541                         }
 542
 543                         err = output(skb);
 544
 545                         if (!err)
 546                                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGCREATES);
 547                         if (err || !frag)
 548                                 break;
 549
 550                         skb = frag;
 551                         frag = skb->next;
 552                         skb->next = NULL;
 553                 }
 554
 555                 if (err == 0) {
 556                         IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGOKS);
 557                         return 0;
 558                 }
 559
 560                 while (frag) {
 561                         skb = frag->next;
 562                         kfree_skb(frag);
 563                         frag = skb;
 564                 }
 565                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
 566                 return err;
 567         }
 568
 569 slow_path:
 570         left = skb->len - hlen;         /* Space per frame */
 571         ptr = raw + hlen;               /* Where to start from */
 572
 573         /* for bridged IP traffic encapsulated inside f.e. a vlan header,
 574          * we need to make room for the encapsulating header
 575          */
 576         pad = nf_bridge_pad(skb);
 577         ll_rs = LL_RESERVED_SPACE_EXTRA(rt->u.dst.dev, pad);
 578         mtu -= pad;
 579
 580         /*
 581          *      Fragment the datagram.
 582          */
 583
 584         offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3;
 585         not_last_frag = iph->frag_off & htons(IP_MF);
 586
 587         /*
 588          *      Keep copying data until we run out.
 589          */
 590
 591         while (left > 0) {
 592                 len = left;
 593                 /* IF: it doesn't fit, use 'mtu' - the data space left */
 594                 if (len > mtu)
 595                         len = mtu;
 596                 /* IF: we are not sending upto and including the packet end
 597                    then align the next start on an eight byte boundary */
 598                 if (len < left) {
 599                         len &= ~7;
 600                 }
 601                 /*
 602                  *      Allocate buffer.
 603                  */
 604
 605                 if ((skb2 = alloc_skb(len+hlen+ll_rs, GFP_ATOMIC)) == NULL) {
 606                         NETDEBUG(KERN_INFO "IP: frag: no memory for new fragment!\n");
 607                         err = -ENOMEM;
 608                         goto fail;
 609                 }
 610
 611                 /*
 612                  *      Set up data on packet
 613                  */
 614
 615                 ip_copy_metadata(skb2, skb);
 616                 skb_reserve(skb2, ll_rs);
 617                 skb_put(skb2, len + hlen);
 618                 skb_reset_network_header(skb2);
 619                 skb2->transport_header = skb2->network_header + hlen;
 620
 621                 /*
 622                  *      Charge the memory for the fragment to any owner
 623                  *      it might possess
 624                  */
 625
 626                 if (skb->sk)
 627                         skb_set_owner_w(skb2, skb->sk);
 628
 629                 /*
 630                  *      Copy the packet header into the new buffer.
 631                  */
 632
 633                 skb_copy_from_linear_data(skb, skb_network_header(skb2), hlen);
 634
 635                 /*
 636                  *      Copy a block of the IP datagram.
 637                  */
 638                 if (skb_copy_bits(skb, ptr, skb_transport_header(skb2), len))
 639                         BUG();
 640                 left -= len;
 641
 642                 /*
 643                  *      Fill in the new header fields.
 644                  */
 645                 iph = ip_hdr(skb2);
 646                 iph->frag_off = htons((offset >> 3));
 647
 648                 /* ANK: dirty, but effective trick. Upgrade options only if
 649                  * the segment to be fragmented was THE FIRST (otherwise,
 650                  * options are already fixed) and make it ONCE
 651                  * on the initial skb, so that all the following fragments
 652                  * will inherit fixed options.
 653                  */
 654                 if (offset == 0)
 655                         ip_options_fragment(skb);
 656
 657                 /*
 658                  *      Added AC : If we are fragmenting a fragment that's not the
 659                  *                 last fragment then keep MF on each bit
 660                  */
 661                 if (left > 0 || not_last_frag)
 662                         iph->frag_off |= htons(IP_MF);
 663                 ptr += len;
 664                 offset += len;
 665
 666                 /*
 667                  *      Put this fragment into the sending queue.
 668                  */
 669                 iph->tot_len = htons(len + hlen);
 670
 671                 ip_send_check(iph);
 672
 673                 err = output(skb2);
 674                 if (err)
 675                         goto fail;
 676
 677                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGCREATES);
 678         }
 679         kfree_skb(skb);
 680         IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGOKS);
 681         return err;
 682
 683 fail:
 684         kfree_skb(skb);
 685         IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
 686         return err;
 687 }
 688
 689 EXPORT_SYMBOL(ip_fragment);
 690
 691 int
 692 ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
 693 {
 694         struct iovec *iov = from;
 695
 696         if (skb->ip_summed == CHECKSUM_PARTIAL) {
 697                 if (memcpy_fromiovecend(to, iov, offset, len) < 0)
 698                         return -EFAULT;
 699         } else {
 700                 __wsum csum = 0;
 701                 if (csum_partial_copy_fromiovecend(to, iov, offset, len, &csum) < 0)
 702                         return -EFAULT;
 703                 skb->csum = csum_block_add(skb->csum, csum, odd);
 704         }
 705         return 0;
 706 }
 707
 708 static inline __wsum
 709 csum_page(struct page *page, int offset, int copy)
 710 {
 711         char *kaddr;
 712         __wsum csum;
 713         kaddr = kmap(page);
 714         csum = csum_partial(kaddr + offset, copy, 0);
 715         kunmap(page);
 716         return csum;
 717 }
 718
 719 static inline int ip_ufo_append_data(struct sock *sk,
 720                         int getfrag(void *from, char *to, int offset, int len,
 721                                int odd, struct sk_buff *skb),
 722                         void *from, int length, int hh_len, int fragheaderlen,
 723                         int transhdrlen, int mtu, unsigned int flags)
 724 {
 725         struct sk_buff *skb;
 726         int err;
 727
 728         /* There is support for UDP fragmentation offload by network
 729          * device, so create one single skb packet containing complete
 730          * udp datagram
 731          */
 732         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL) {
 733                 skb = sock_alloc_send_skb(sk,
 734                         hh_len + fragheaderlen + transhdrlen + 20,
 735                         (flags & MSG_DONTWAIT), &err);
 736
 737                 if (skb == NULL)
 738                         return err;
 739
 740                 /* reserve space for Hardware header */
 741                 skb_reserve(skb, hh_len);
 742
 743                 /* create space for UDP/IP header */
 744                 skb_put(skb, fragheaderlen + transhdrlen);
 745
 746                 /* initialize network header pointer */
 747                 skb_reset_network_header(skb);
 748
 749                 /* initialize protocol header pointer */
 750                 skb->transport_header = skb->network_header + fragheaderlen;
 751
 752                 skb->ip_summed = CHECKSUM_PARTIAL;
 753                 skb->csum = 0;
 754                 sk->sk_sndmsg_off = 0;
 755
 756                 /* specify the length of each IP datagram fragment */
 757                 skb_shinfo(skb)->gso_size = mtu - fragheaderlen;
 758                 skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
 759                 __skb_queue_tail(&sk->sk_write_queue, skb);
 760         }
 761
 762         return skb_append_datato_frags(sk, skb, getfrag, from,
 763                                        (length - transhdrlen));
 764 }
 765
 766 /*
 767  *      ip_append_data() and ip_append_page() can make one large IP datagram
 768  *      from many pieces of data. Each pieces will be holded on the socket
 769  *      until ip_push_pending_frames() is called. Each piece can be a page
 770  *      or non-page data.
 771  *
 772  *      Not only UDP, other transport protocols - e.g. raw sockets - can use
 773  *      this interface potentially.
 774  *
 775  *      LATER: length must be adjusted by pad at tail, when it is required.
 776  */
 777 int ip_append_data(struct sock *sk,
 778                    int getfrag(void *from, char *to, int offset, int len,
 779                                int odd, struct sk_buff *skb),
 780                    void *from, int length, int transhdrlen,
 781                    struct ipcm_cookie *ipc, struct rtable **rtp,
 782                    unsigned int flags)
 783 {
 784         struct inet_sock *inet = inet_sk(sk);
 785         struct sk_buff *skb;
 786
 787         struct ip_options *opt = NULL;
 788         int hh_len;
 789         int exthdrlen;
 790         int mtu;
 791         int copy;
 792         int err;
 793         int offset = 0;
 794         unsigned int maxfraglen, fragheaderlen;
 795         int csummode = CHECKSUM_NONE;
 796         struct rtable *rt;
 797
 798         if (flags&MSG_PROBE)
 799                 return 0;
 800
 801         if (skb_queue_empty(&sk->sk_write_queue)) {
 802                 /*
 803                  * setup for corking.
 804                  */
 805                 opt = ipc->opt;
 806                 if (opt) {
 807                         if (inet->cork.opt == NULL) {
 808                                 inet->cork.opt = kmalloc(sizeof(struct ip_options) + 40, sk->sk_allocation);
 809                                 if (unlikely(inet->cork.opt == NULL))
 810                                         return -ENOBUFS;
 811                         }
 812                         memcpy(inet->cork.opt, opt, sizeof(struct ip_options)+opt->optlen);
 813                         inet->cork.flags |= IPCORK_OPT;
 814                         inet->cork.addr = ipc->addr;
 815                 }
 816                 rt = *rtp;
 817                 if (unlikely(!rt))
 818                         return -EFAULT;
 819                 /*
 820                  * We steal reference to this route, caller should not release it
 821                  */
 822                 *rtp = NULL;
 823                 inet->cork.fragsize = mtu = inet->pmtudisc == IP_PMTUDISC_PROBE ?
 824                                             rt->u.dst.dev->mtu :
 825                                             dst_mtu(rt->u.dst.path);
 826                 inet->cork.dst = &rt->u.dst;
 827                 inet->cork.length = 0;
 828                 sk->sk_sndmsg_page = NULL;
 829                 sk->sk_sndmsg_off = 0;
 830                 if ((exthdrlen = rt->u.dst.header_len) != 0) {
 831                         length += exthdrlen;
 832                         transhdrlen += exthdrlen;
 833                 }
 834         } else {
 835                 rt = (struct rtable *)inet->cork.dst;
 836                 if (inet->cork.flags & IPCORK_OPT)
 837                         opt = inet->cork.opt;
 838
 839                 transhdrlen = 0;
 840                 exthdrlen = 0;
 841                 mtu = inet->cork.fragsize;
 842         }
 843         hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
 844
 845         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
 846         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
 847
 848         if (inet->cork.length + length > 0xFFFF - fragheaderlen) {
 849                 ip_local_error(sk, EMSGSIZE, rt->rt_dst, inet->inet_dport,
 850                                mtu-exthdrlen);
 851                 return -EMSGSIZE;
 852         }
 853
 854         /*
 855          * transhdrlen > 0 means that this is the first fragment and we wish
 856          * it won't be fragmented in the future.
 857          */
 858         if (transhdrlen &&
 859             length + fragheaderlen <= mtu &&
 860             rt->u.dst.dev->features & NETIF_F_V4_CSUM &&
 861             !exthdrlen)
 862                 csummode = CHECKSUM_PARTIAL;
 863
 864         inet->cork.length += length;
 865         if (((length> mtu) || !skb_queue_empty(&sk->sk_write_queue)) &&
 866             (sk->sk_protocol == IPPROTO_UDP) &&
 867             (rt->u.dst.dev->features & NETIF_F_UFO)) {
 868                 err = ip_ufo_append_data(sk, getfrag, from, length, hh_len,
 869                                          fragheaderlen, transhdrlen, mtu,
 870                                          flags);
 871                 if (err)
 872                         goto error;
 873                 return 0;
 874         }
 875
 876         /* So, what's going on in the loop below?
 877          *
 878          * We use calculated fragment length to generate chained skb,
 879          * each of segments is IP fragment ready for sending to network after
 880          * adding appropriate IP header.
 881          */
 882
 883         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
 884                 goto alloc_new_skb;
 885
 886         while (length > 0) {
 887                 /* Check if the remaining data fits into current packet. */
 888                 copy = mtu - skb->len;
 889                 if (copy < length)
 890                         copy = maxfraglen - skb->len;
 891                 if (copy <= 0) {
 892                         char *data;
 893                         unsigned int datalen;
 894                         unsigned int fraglen;
 895                         unsigned int fraggap;
 896                         unsigned int alloclen;
 897                         struct sk_buff *skb_prev;
 898 alloc_new_skb:
 899                         skb_prev = skb;
 900                         if (skb_prev)
 901                                 fraggap = skb_prev->len - maxfraglen;
 902                         else
 903                                 fraggap = 0;
 904
 905                         /*
 906                          * If remaining data exceeds the mtu,
 907                          * we know we need more fragment(s).
 908                          */
 909                         datalen = length + fraggap;
 910                         if (datalen > mtu - fragheaderlen)
 911                                 datalen = maxfraglen - fragheaderlen;
 912                         fraglen = datalen + fragheaderlen;
 913
 914                         if ((flags & MSG_MORE) &&
 915                             !(rt->u.dst.dev->features&NETIF_F_SG))
 916                                 alloclen = mtu;
 917                         else
 918                                 alloclen = datalen + fragheaderlen;
 919
 920                         /* The last fragment gets additional space at tail.
 921                          * Note, with MSG_MORE we overallocate on fragments,
 922                          * because we have no idea what fragment will be
 923                          * the last.
 924                          */
 925                         if (datalen == length + fraggap)
 926                                 alloclen += rt->u.dst.trailer_len;
 927
 928                         if (transhdrlen) {
 929                                 skb = sock_alloc_send_skb(sk,
 930                                                 alloclen + hh_len + 15,
 931                                                 (flags & MSG_DONTWAIT), &err);
 932                         } else {
 933                                 skb = NULL;
 934                                 if (atomic_read(&sk->sk_wmem_alloc) <=
 935                                     2 * sk->sk_sndbuf)
 936                                         skb = sock_wmalloc(sk,
 937                                                            alloclen + hh_len + 15, 1,
 938                                                            sk->sk_allocation);
 939                                 if (unlikely(skb == NULL))
 940                                         err = -ENOBUFS;
 941                                 else
 942                                         /* only the initial fragment is
 943                                            time stamped */
 944                                         ipc->shtx.flags = 0;
 945                         }
 946                         if (skb == NULL)
 947                                 goto error;
 948
 949                         /*
 950                          *      Fill in the control structures
 951                          */
 952                         skb->ip_summed = csummode;
 953                         skb->csum = 0;
 954                         skb_reserve(skb, hh_len);
 955                         *skb_tx(skb) = ipc->shtx;
 956
 957                         /*
 958                          *      Find where to start putting bytes.
 959                          */
 960                         data = skb_put(skb, fraglen);
 961                         skb_set_network_header(skb, exthdrlen);
 962                         skb->transport_header = (skb->network_header +
 963                                                  fragheaderlen);
 964                         data += fragheaderlen;
 965
 966                         if (fraggap) {
 967                                 skb->csum = skb_copy_and_csum_bits(
 968                                         skb_prev, maxfraglen,
 969                                         data + transhdrlen, fraggap, 0);
 970                                 skb_prev->csum = csum_sub(skb_prev->csum,
 971                                                           skb->csum);
 972                                 data += fraggap;
 973                                 pskb_trim_unique(skb_prev, maxfraglen);
 974                         }
 975
 976                         copy = datalen - transhdrlen - fraggap;
 977                         if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
 978                                 err = -EFAULT;
 979                                 kfree_skb(skb);
 980                                 goto error;
 981                         }
 982
 983                         offset += copy;
 984                         length -= datalen - fraggap;
 985                         transhdrlen = 0;
 986                         exthdrlen = 0;
 987                         csummode = CHECKSUM_NONE;
 988
 989                         /*
 990                          * Put the packet on the pending queue.
 991                          */
 992                         __skb_queue_tail(&sk->sk_write_queue, skb);
 993                         continue;
 994                 }
 995
 996                 if (copy > length)
 997                         copy = length;
 998
 999                 if (!(rt->u.dst.dev->features&NETIF_F_SG)) {
1000                         unsigned int off;
1001
1002                         off = skb->len;
1003                         if (getfrag(from, skb_put(skb, copy),
1004                                         offset, copy, off, skb) < 0) {
1005                                 __skb_trim(skb, off);
1006                                 err = -EFAULT;
1007                                 goto error;
1008                         }
1009                 } else {
1010                         int i = skb_shinfo(skb)->nr_frags;
1011                         skb_frag_t *frag = &skb_shinfo(skb)->frags[i-1];
1012                         struct page *page = sk->sk_sndmsg_page;
1013                         int off = sk->sk_sndmsg_off;
1014                         unsigned int left;
1015
1016                         if (page && (left = PAGE_SIZE - off) > 0) {
1017                                 if (copy >= left)
1018                                         copy = left;
1019                                 if (page != frag->page) {
1020                                         if (i == MAX_SKB_FRAGS) {
1021                                                 err = -EMSGSIZE;
1022                                                 goto error;
1023                                         }
1024                                         get_page(page);
1025                                         skb_fill_page_desc(skb, i, page, sk->sk_sndmsg_off, 0);
1026                                         frag = &skb_shinfo(skb)->frags[i];
1027                                 }
1028                         } else if (i < MAX_SKB_FRAGS) {
1029                                 if (copy > PAGE_SIZE)
1030                                         copy = PAGE_SIZE;
1031                                 page = alloc_pages(sk->sk_allocation, 0);
1032                                 if (page == NULL)  {
1033                                         err = -ENOMEM;
1034                                         goto error;
1035                                 }
1036                                 sk->sk_sndmsg_page = page;
1037                                 sk->sk_sndmsg_off = 0;
1038
1039                                 skb_fill_page_desc(skb, i, page, 0, 0);
1040                                 frag = &skb_shinfo(skb)->frags[i];
1041                         } else {
1042                                 err = -EMSGSIZE;
1043                                 goto error;
1044                         }
1045                         if (getfrag(from, page_address(frag->page)+frag->page_offset+frag->size, offset, copy, skb->len, skb) < 0) {
1046                                 err = -EFAULT;
1047                                 goto error;
1048                         }
1049                         sk->sk_sndmsg_off += copy;
1050                         frag->size += copy;
1051                         skb->len += copy;
1052                         skb->data_len += copy;
1053                         skb->truesize += copy;
1054                         atomic_add(copy, &sk->sk_wmem_alloc);
1055                 }
1056                 offset += copy;
1057                 length -= copy;
1058         }
1059
1060         return 0;
1061
1062 error:
1063         inet->cork.length -= length;
1064         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1065         return err;
1066 }
1067
1068 ssize_t ip_append_page(struct sock *sk, struct page *page,
1069                        int offset, size_t size, int flags)
1070 {
1071         struct inet_sock *inet = inet_sk(sk);
1072         struct sk_buff *skb;
1073         struct rtable *rt;
1074         struct ip_options *opt = NULL;
1075         int hh_len;
1076         int mtu;
1077         int len;
1078         int err;
1079         unsigned int maxfraglen, fragheaderlen, fraggap;
1080
1081         if (inet->hdrincl)
1082                 return -EPERM;
1083
1084         if (flags&MSG_PROBE)
1085                 return 0;
1086
1087         if (skb_queue_empty(&sk->sk_write_queue))
1088                 return -EINVAL;
1089
1090         rt = (struct rtable *)inet->cork.dst;
1091         if (inet->cork.flags & IPCORK_OPT)
1092                 opt = inet->cork.opt;
1093
1094         if (!(rt->u.dst.dev->features&NETIF_F_SG))
1095                 return -EOPNOTSUPP;
1096
1097         hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
1098         mtu = inet->cork.fragsize;
1099
1100         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
1101         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
1102
1103         if (inet->cork.length + size > 0xFFFF - fragheaderlen) {
1104                 ip_local_error(sk, EMSGSIZE, rt->rt_dst, inet->inet_dport, mtu);
1105                 return -EMSGSIZE;
1106         }
1107
1108         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
1109                 return -EINVAL;
1110
1111         inet->cork.length += size;
1112         if ((sk->sk_protocol == IPPROTO_UDP) &&
1113             (rt->u.dst.dev->features & NETIF_F_UFO)) {
1114                 skb_shinfo(skb)->gso_size = mtu - fragheaderlen;
1115                 skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
1116         }
1117
1118
1119         while (size > 0) {
1120                 int i;
1121
1122                 if (skb_is_gso(skb))
1123                         len = size;
1124                 else {
1125
1126                         /* Check if the remaining data fits into current packet. */
1127                         len = mtu - skb->len;
1128                         if (len < size)
1129                                 len = maxfraglen - skb->len;
1130                 }
1131                 if (len <= 0) {
1132                         struct sk_buff *skb_prev;
1133                         int alloclen;
1134
1135                         skb_prev = skb;
1136                         fraggap = skb_prev->len - maxfraglen;
1137
1138                         alloclen = fragheaderlen + hh_len + fraggap + 15;
1139                         skb = sock_wmalloc(sk, alloclen, 1, sk->sk_allocation);
1140                         if (unlikely(!skb)) {
1141                                 err = -ENOBUFS;
1142                                 goto error;
1143                         }
1144
1145                         /*
1146                          *      Fill in the control structures
1147                          */
1148                         skb->ip_summed = CHECKSUM_NONE;
1149                         skb->csum = 0;
1150                         skb_reserve(skb, hh_len);
1151
1152                         /*
1153                          *      Find where to start putting bytes.
1154                          */
1155                         skb_put(skb, fragheaderlen + fraggap);
1156                         skb_reset_network_header(skb);
1157                         skb->transport_header = (skb->network_header +
1158                                                  fragheaderlen);
1159                         if (fraggap) {
1160                                 skb->csum = skb_copy_and_csum_bits(skb_prev,
1161                                                                    maxfraglen,
1162                                                     skb_transport_header(skb),
1163                                                                    fraggap, 0);
1164                                 skb_prev->csum = csum_sub(skb_prev->csum,
1165                                                           skb->csum);
1166                                 pskb_trim_unique(skb_prev, maxfraglen);
1167                         }
1168
1169                         /*
1170                          * Put the packet on the pending queue.
1171                          */
1172                         __skb_queue_tail(&sk->sk_write_queue, skb);
1173                         continue;
1174                 }
1175
1176                 i = skb_shinfo(skb)->nr_frags;
1177                 if (len > size)
1178                         len = size;
1179                 if (skb_can_coalesce(skb, i, page, offset)) {
1180                         skb_shinfo(skb)->frags[i-1].size += len;
1181                 } else if (i < MAX_SKB_FRAGS) {
1182                         get_page(page);
1183                         skb_fill_page_desc(skb, i, page, offset, len);
1184                 } else {
1185                         err = -EMSGSIZE;
1186                         goto error;
1187                 }
1188
1189                 if (skb->ip_summed == CHECKSUM_NONE) {
1190                         __wsum csum;
1191                         csum = csum_page(page, offset, len);
1192                         skb->csum = csum_block_add(skb->csum, csum, skb->len);
1193                 }
1194
1195                 skb->len += len;
1196                 skb->data_len += len;
1197                 skb->truesize += len;
1198                 atomic_add(len, &sk->sk_wmem_alloc);
1199                 offset += len;
1200                 size -= len;
1201         }
1202         return 0;
1203
1204 error:
1205         inet->cork.length -= size;
1206         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1207         return err;
1208 }
1209
1210 static void ip_cork_release(struct inet_sock *inet)
1211 {
1212         inet->cork.flags &= ~IPCORK_OPT;
1213         kfree(inet->cork.opt);
1214         inet->cork.opt = NULL;
1215         dst_release(inet->cork.dst);
1216         inet->cork.dst = NULL;
1217 }
1218
1219 /*
1220  *      Combined all pending IP fragments on the socket as one IP datagram
1221  *      and push them out.
1222  */
1223 int ip_push_pending_frames(struct sock *sk)
1224 {
1225         struct sk_buff *skb, *tmp_skb;
1226         struct sk_buff **tail_skb;
1227         struct inet_sock *inet = inet_sk(sk);
1228         struct net *net = sock_net(sk);
1229         struct ip_options *opt = NULL;
1230         struct rtable *rt = (struct rtable *)inet->cork.dst;
1231         struct iphdr *iph;
1232         __be16 df = 0;
1233         __u8 ttl;
1234         int err = 0;
1235
1236         if ((skb = __skb_dequeue(&sk->sk_write_queue)) == NULL)
1237                 goto out;
1238         tail_skb = &(skb_shinfo(skb)->frag_list);
1239
1240         /* move skb->data to ip header from ext header */
1241         if (skb->data < skb_network_header(skb))
1242                 __skb_pull(skb, skb_network_offset(skb));
1243         while ((tmp_skb = __skb_dequeue(&sk->sk_write_queue)) != NULL) {
1244                 __skb_pull(tmp_skb, skb_network_header_len(skb));
1245                 *tail_skb = tmp_skb;
1246                 tail_skb = &(tmp_skb->next);
1247                 skb->len += tmp_skb->len;
1248                 skb->data_len += tmp_skb->len;
1249                 skb->truesize += tmp_skb->truesize;
1250                 tmp_skb->destructor = NULL;
1251                 tmp_skb->sk = NULL;
1252         }
1253
1254         /* Unless user demanded real pmtu discovery (IP_PMTUDISC_DO), we allow
1255          * to fragment the frame generated here. No matter, what transforms
1256          * how transforms change size of the packet, it will come out.
1257          */
1258         if (inet->pmtudisc < IP_PMTUDISC_DO)
1259                 skb->local_df = 1;
1260
1261         /* DF bit is set when we want to see DF on outgoing frames.
1262          * If local_df is set too, we still allow to fragment this frame
1263          * locally. */
1264         if (inet->pmtudisc >= IP_PMTUDISC_DO ||
1265             (skb->len <= dst_mtu(&rt->u.dst) &&
1266              ip_dont_fragment(sk, &rt->u.dst)))
1267                 df = htons(IP_DF);
1268
1269         if (inet->cork.flags & IPCORK_OPT)
1270                 opt = inet->cork.opt;
1271
1272         if (rt->rt_type == RTN_MULTICAST)
1273                 ttl = inet->mc_ttl;
1274         else
1275                 ttl = ip_select_ttl(inet, &rt->u.dst);
1276
1277         iph = (struct iphdr *)skb->data;
1278         iph->version = 4;
1279         iph->ihl = 5;
1280         if (opt) {
1281                 iph->ihl += opt->optlen>>2;
1282                 ip_options_build(skb, opt, inet->cork.addr, rt, 0);
1283         }
1284         iph->tos = inet->tos;
1285         iph->frag_off = df;
1286         ip_select_ident(iph, &rt->u.dst, sk);
1287         iph->ttl = ttl;
1288         iph->protocol = sk->sk_protocol;
1289         iph->saddr = rt->rt_src;
1290         iph->daddr = rt->rt_dst;
1291
1292         skb->priority = sk->sk_priority;
1293         skb->mark = sk->sk_mark;
1294         /*
1295          * Steal rt from cork.dst to avoid a pair of atomic_inc/atomic_dec
1296          * on dst refcount
1297          */
1298         inet->cork.dst = NULL;
1299         skb_dst_set(skb, &rt->u.dst);
1300
1301         if (iph->protocol == IPPROTO_ICMP)
1302                 icmp_out_count(net, ((struct icmphdr *)
1303                         skb_transport_header(skb))->type);
1304
1305         /* Netfilter gets whole the not fragmented skb. */
1306         err = ip_local_out(skb);
1307         if (err) {
1308                 if (err > 0)
1309                         err = net_xmit_errno(err);
1310                 if (err)
1311                         goto error;
1312         }
1313
1314 out:
1315         ip_cork_release(inet);
1316         return err;
1317
1318 error:
1319         IP_INC_STATS(net, IPSTATS_MIB_OUTDISCARDS);
1320         goto out;
1321 }
1322
1323 /*
1324  *      Throw away all pending data on the socket.
1325  */
1326 void ip_flush_pending_frames(struct sock *sk)
1327 {
1328         struct sk_buff *skb;
1329
1330         while ((skb = __skb_dequeue_tail(&sk->sk_write_queue)) != NULL)
1331                 kfree_skb(skb);
1332
1333         ip_cork_release(inet_sk(sk));
1334 }
1335
1336
1337 /*
1338  *      Fetch data from kernel space and fill in checksum if needed.
1339  */
1340 static int ip_reply_glue_bits(void *dptr, char *to, int offset,
1341                               int len, int odd, struct sk_buff *skb)
1342 {
1343         __wsum csum;
1344
1345         csum = csum_partial_copy_nocheck(dptr+offset, to, len, 0);
1346         skb->csum = csum_block_add(skb->csum, csum, odd);
1347         return 0;
1348 }
1349
1350 /*
1351  *      Generic function to send a packet as reply to another packet.
1352  *      Used to send TCP resets so far. ICMP should use this function too.
1353  *
1354  *      Should run single threaded per socket because it uses the sock
1355  *      structure to pass arguments.
1356  */
1357 void ip_send_reply(struct sock *sk, struct sk_buff *skb, struct ip_reply_arg *arg,
1358                    unsigned int len)
1359 {
1360         struct inet_sock *inet = inet_sk(sk);
1361         struct {
1362                 struct ip_options       opt;
1363                 char                    data[40];
1364         } replyopts;
1365         struct ipcm_cookie ipc;
1366         __be32 daddr;
1367         struct rtable *rt = skb_rtable(skb);
1368
1369         if (ip_options_echo(&replyopts.opt, skb))
1370                 return;
1371
1372         daddr = ipc.addr = rt->rt_src;
1373         ipc.opt = NULL;
1374         ipc.shtx.flags = 0;
1375
1376         if (replyopts.opt.optlen) {
1377                 ipc.opt = &replyopts.opt;
1378
1379                 if (ipc.opt->srr)
1380                         daddr = replyopts.opt.faddr;
1381         }
1382
1383         {
1384                 struct flowi fl = { .oif = arg->bound_dev_if,
1385                                     .nl_u = { .ip4_u =
1386                                               { .daddr = daddr,
1387                                                 .saddr = rt->rt_spec_dst,
1388                                                 .tos = RT_TOS(ip_hdr(skb)->tos) } },
1389                                     /* Not quite clean, but right. */
1390                                     .uli_u = { .ports =
1391                                                { .sport = tcp_hdr(skb)->dest,
1392                                                  .dport = tcp_hdr(skb)->source } },
1393                                     .proto = sk->sk_protocol,
1394                                     .flags = ip_reply_arg_flowi_flags(arg) };
1395                 security_skb_classify_flow(skb, &fl);
1396                 if (ip_route_output_key(sock_net(sk), &rt, &fl))
1397                         return;
1398         }
1399
1400         /* And let IP do all the hard work.
1401
1402            This chunk is not reenterable, hence spinlock.
1403            Note that it uses the fact, that this function is called
1404            with locally disabled BH and that sk cannot be already spinlocked.
1405          */
1406         bh_lock_sock(sk);
1407         inet->tos = ip_hdr(skb)->tos;
1408         sk->sk_priority = skb->priority;
1409         sk->sk_protocol = ip_hdr(skb)->protocol;
1410         sk->sk_bound_dev_if = arg->bound_dev_if;
1411         ip_append_data(sk, ip_reply_glue_bits, arg->iov->iov_base, len, 0,
1412                        &ipc, &rt, MSG_DONTWAIT);
1413         if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {
1414                 if (arg->csumoffset >= 0)
1415                         *((__sum16 *)skb_transport_header(skb) +
1416                           arg->csumoffset) = csum_fold(csum_add(skb->csum,
1417                                                                 arg->csum));
1418                 skb->ip_summed = CHECKSUM_NONE;
1419                 ip_push_pending_frames(sk);
1420         }
1421
1422         bh_unlock_sock(sk);
1423
1424         ip_rt_put(rt);
1425 }
1426
1427 void __init ip_init(void)
1428 {
1429         ip_rt_init();
1430         inet_initpeers();
1431
1432 #if defined(CONFIG_IP_MULTICAST) && defined(CONFIG_PROC_FS)
1433         igmp_mc_proc_init();
1434 #endif
1435 }
1436
1437 EXPORT_SYMBOL(ip_generic_getfrag);
1438 EXPORT_SYMBOL(ip_queue_xmit);
1439 EXPORT_SYMBOL(ip_send_check);