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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                     &&
 268                     ((rt->rt_flags & RTCF_LOCAL) ||
 269                      !(IPCB(skb)->flags & IPSKB_FORWARDED))
 270 #endif
 271                    ) {
 272                         struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
 273                         if (newskb)
 274                                 NF_HOOK(PF_INET, NF_INET_POST_ROUTING, newskb,
 275                                         NULL, newskb->dev,
 276                                         ip_dev_loopback_xmit);
 277                 }
 278
 279                 /* Multicasts with ttl 0 must not go beyond the host */
 280
 281                 if (ip_hdr(skb)->ttl == 0) {
 282                         kfree_skb(skb);
 283                         return 0;
 284                 }
 285         }
 286
 287         if (rt->rt_flags&RTCF_BROADCAST) {
 288                 struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
 289                 if (newskb)
 290                         NF_HOOK(PF_INET, NF_INET_POST_ROUTING, newskb, NULL,
 291                                 newskb->dev, ip_dev_loopback_xmit);
 292         }
 293
 294         return NF_HOOK_COND(PF_INET, NF_INET_POST_ROUTING, skb, NULL, skb->dev,
 295                             ip_finish_output,
 296                             !(IPCB(skb)->flags & IPSKB_REROUTED));
 297 }
 298
 299 int ip_output(struct sk_buff *skb)
 300 {
 301         struct net_device *dev = skb_dst(skb)->dev;
 302
 303         IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUT, skb->len);
 304
 305         skb->dev = dev;
 306         skb->protocol = htons(ETH_P_IP);
 307
 308         return NF_HOOK_COND(PF_INET, NF_INET_POST_ROUTING, skb, NULL, dev,
 309                             ip_finish_output,
 310                             !(IPCB(skb)->flags & IPSKB_REROUTED));
 311 }
 312
 313 int ip_queue_xmit(struct sk_buff *skb, int ipfragok)
 314 {
 315         struct sock *sk = skb->sk;
 316         struct inet_sock *inet = inet_sk(sk);
 317         struct ip_options *opt = inet->opt;
 318         struct rtable *rt;
 319         struct iphdr *iph;
 320
 321         /* Skip all of this if the packet is already routed,
 322          * f.e. by something like SCTP.
 323          */
 324         rt = skb_rtable(skb);
 325         if (rt != NULL)
 326                 goto packet_routed;
 327
 328         /* Make sure we can route this packet. */
 329         rt = (struct rtable *)__sk_dst_check(sk, 0);
 330         if (rt == NULL) {
 331                 __be32 daddr;
 332
 333                 /* Use correct destination address if we have options. */
 334                 daddr = inet->inet_daddr;
 335                 if(opt && opt->srr)
 336                         daddr = opt->faddr;
 337
 338                 {
 339                         struct flowi fl = { .oif = sk->sk_bound_dev_if,
 340                                             .mark = sk->sk_mark,
 341                                             .nl_u = { .ip4_u =
 342                                                       { .daddr = daddr,
 343                                                         .saddr = inet->inet_saddr,
 344                                                         .tos = RT_CONN_FLAGS(sk) } },
 345                                             .proto = sk->sk_protocol,
 346                                             .flags = inet_sk_flowi_flags(sk),
 347                                             .uli_u = { .ports =
 348                                                        { .sport = inet->inet_sport,
 349                                                          .dport = inet->inet_dport } } };
 350
 351                         /* If this fails, retransmit mechanism of transport layer will
 352                          * keep trying until route appears or the connection times
 353                          * itself out.
 354                          */
 355                         security_sk_classify_flow(sk, &fl);
 356                         if (ip_route_output_flow(sock_net(sk), &rt, &fl, sk, 0))
 357                                 goto no_route;
 358                 }
 359                 sk_setup_caps(sk, &rt->u.dst);
 360         }
 361         skb_dst_set(skb, dst_clone(&rt->u.dst));
 362
 363 packet_routed:
 364         if (opt && opt->is_strictroute && rt->rt_dst != rt->rt_gateway)
 365                 goto no_route;
 366
 367         /* OK, we know where to send it, allocate and build IP header. */
 368         skb_push(skb, sizeof(struct iphdr) + (opt ? opt->optlen : 0));
 369         skb_reset_network_header(skb);
 370         iph = ip_hdr(skb);
 371         *((__be16 *)iph) = htons((4 << 12) | (5 << 8) | (inet->tos & 0xff));
 372         if (ip_dont_fragment(sk, &rt->u.dst) && !ipfragok)
 373                 iph->frag_off = htons(IP_DF);
 374         else
 375                 iph->frag_off = 0;
 376         iph->ttl      = ip_select_ttl(inet, &rt->u.dst);
 377         iph->protocol = sk->sk_protocol;
 378         iph->saddr    = rt->rt_src;
 379         iph->daddr    = rt->rt_dst;
 380         /* Transport layer set skb->h.foo itself. */
 381
 382         if (opt && opt->optlen) {
 383                 iph->ihl += opt->optlen >> 2;
 384                 ip_options_build(skb, opt, inet->inet_daddr, rt, 0);
 385         }
 386
 387         ip_select_ident_more(iph, &rt->u.dst, sk,
 388                              (skb_shinfo(skb)->gso_segs ?: 1) - 1);
 389
 390         skb->priority = sk->sk_priority;
 391         skb->mark = sk->sk_mark;
 392
 393         return ip_local_out(skb);
 394
 395 no_route:
 396         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);
 397         kfree_skb(skb);
 398         return -EHOSTUNREACH;
 399 }
 400
 401
 402 static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
 403 {
 404         to->pkt_type = from->pkt_type;
 405         to->priority = from->priority;
 406         to->protocol = from->protocol;
 407         skb_dst_drop(to);
 408         skb_dst_set(to, dst_clone(skb_dst(from)));
 409         to->dev = from->dev;
 410         to->mark = from->mark;
 411
 412         /* Copy the flags to each fragment. */
 413         IPCB(to)->flags = IPCB(from)->flags;
 414
 415 #ifdef CONFIG_NET_SCHED
 416         to->tc_index = from->tc_index;
 417 #endif
 418         nf_copy(to, from);
 419 #if defined(CONFIG_NETFILTER_XT_TARGET_TRACE) || \
 420     defined(CONFIG_NETFILTER_XT_TARGET_TRACE_MODULE)
 421         to->nf_trace = from->nf_trace;
 422 #endif
 423 #if defined(CONFIG_IP_VS) || defined(CONFIG_IP_VS_MODULE)
 424         to->ipvs_property = from->ipvs_property;
 425 #endif
 426         skb_copy_secmark(to, from);
 427 }
 428
 429 /*
 430  *      This IP datagram is too large to be sent in one piece.  Break it up into
 431  *      smaller pieces (each of size equal to IP header plus
 432  *      a block of the data of the original IP data part) that will yet fit in a
 433  *      single device frame, and queue such a frame for sending.
 434  */
 435
 436 int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
 437 {
 438         struct iphdr *iph;
 439         int raw = 0;
 440         int ptr;
 441         struct net_device *dev;
 442         struct sk_buff *skb2;
 443         unsigned int mtu, hlen, left, len, ll_rs, pad;
 444         int offset;
 445         __be16 not_last_frag;
 446         struct rtable *rt = skb_rtable(skb);
 447         int err = 0;
 448
 449         dev = rt->u.dst.dev;
 450
 451         /*
 452          *      Point into the IP datagram header.
 453          */
 454
 455         iph = ip_hdr(skb);
 456
 457         if (unlikely((iph->frag_off & htons(IP_DF)) && !skb->local_df)) {
 458                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
 459                 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
 460                           htonl(ip_skb_dst_mtu(skb)));
 461                 kfree_skb(skb);
 462                 return -EMSGSIZE;
 463         }
 464
 465         /*
 466          *      Setup starting values.
 467          */
 468
 469         hlen = iph->ihl * 4;
 470         mtu = dst_mtu(&rt->u.dst) - hlen;       /* Size of data space */
 471         IPCB(skb)->flags |= IPSKB_FRAG_COMPLETE;
 472
 473         /* When frag_list is given, use it. First, check its validity:
 474          * some transformers could create wrong frag_list or break existing
 475          * one, it is not prohibited. In this case fall back to copying.
 476          *
 477          * LATER: this step can be merged to real generation of fragments,
 478          * we can switch to copy when see the first bad fragment.
 479          */
 480         if (skb_has_frags(skb)) {
 481                 struct sk_buff *frag;
 482                 int first_len = skb_pagelen(skb);
 483                 int truesizes = 0;
 484
 485                 if (first_len - hlen > mtu ||
 486                     ((first_len - hlen) & 7) ||
 487                     (iph->frag_off & htons(IP_MF|IP_OFFSET)) ||
 488                     skb_cloned(skb))
 489                         goto slow_path;
 490
 491                 skb_walk_frags(skb, frag) {
 492                         /* Correct geometry. */
 493                         if (frag->len > mtu ||
 494                             ((frag->len & 7) && frag->next) ||
 495                             skb_headroom(frag) < hlen)
 496                             goto slow_path;
 497
 498                         /* Partially cloned skb? */
 499                         if (skb_shared(frag))
 500                                 goto slow_path;
 501
 502                         BUG_ON(frag->sk);
 503                         if (skb->sk) {
 504                                 frag->sk = skb->sk;
 505                                 frag->destructor = sock_wfree;
 506                         }
 507                         truesizes += frag->truesize;
 508                 }
 509
 510                 /* Everything is OK. Generate! */
 511
 512                 err = 0;
 513                 offset = 0;
 514                 frag = skb_shinfo(skb)->frag_list;
 515                 skb_frag_list_init(skb);
 516                 skb->data_len = first_len - skb_headlen(skb);
 517                 skb->truesize -= truesizes;
 518                 skb->len = first_len;
 519                 iph->tot_len = htons(first_len);
 520                 iph->frag_off = htons(IP_MF);
 521                 ip_send_check(iph);
 522
 523                 for (;;) {
 524                         /* Prepare header of the next frame,
 525                          * before previous one went down. */
 526                         if (frag) {
 527                                 frag->ip_summed = CHECKSUM_NONE;
 528                                 skb_reset_transport_header(frag);
 529                                 __skb_push(frag, hlen);
 530                                 skb_reset_network_header(frag);
 531                                 memcpy(skb_network_header(frag), iph, hlen);
 532                                 iph = ip_hdr(frag);
 533                                 iph->tot_len = htons(frag->len);
 534                                 ip_copy_metadata(frag, skb);
 535                                 if (offset == 0)
 536                                         ip_options_fragment(frag);
 537                                 offset += skb->len - hlen;
 538                                 iph->frag_off = htons(offset>>3);
 539                                 if (frag->next != NULL)
 540                                         iph->frag_off |= htons(IP_MF);
 541                                 /* Ready, complete checksum */
 542                                 ip_send_check(iph);
 543                         }
 544
 545                         err = output(skb);
 546
 547                         if (!err)
 548                                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGCREATES);
 549                         if (err || !frag)
 550                                 break;
 551
 552                         skb = frag;
 553                         frag = skb->next;
 554                         skb->next = NULL;
 555                 }
 556
 557                 if (err == 0) {
 558                         IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGOKS);
 559                         return 0;
 560                 }
 561
 562                 while (frag) {
 563                         skb = frag->next;
 564                         kfree_skb(frag);
 565                         frag = skb;
 566                 }
 567                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
 568                 return err;
 569         }
 570
 571 slow_path:
 572         left = skb->len - hlen;         /* Space per frame */
 573         ptr = raw + hlen;               /* Where to start from */
 574
 575         /* for bridged IP traffic encapsulated inside f.e. a vlan header,
 576          * we need to make room for the encapsulating header
 577          */
 578         pad = nf_bridge_pad(skb);
 579         ll_rs = LL_RESERVED_SPACE_EXTRA(rt->u.dst.dev, pad);
 580         mtu -= pad;
 581
 582         /*
 583          *      Fragment the datagram.
 584          */
 585
 586         offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3;
 587         not_last_frag = iph->frag_off & htons(IP_MF);
 588
 589         /*
 590          *      Keep copying data until we run out.
 591          */
 592
 593         while (left > 0) {
 594                 len = left;
 595                 /* IF: it doesn't fit, use 'mtu' - the data space left */
 596                 if (len > mtu)
 597                         len = mtu;
 598                 /* IF: we are not sending upto and including the packet end
 599                    then align the next start on an eight byte boundary */
 600                 if (len < left) {
 601                         len &= ~7;
 602                 }
 603                 /*
 604                  *      Allocate buffer.
 605                  */
 606
 607                 if ((skb2 = alloc_skb(len+hlen+ll_rs, GFP_ATOMIC)) == NULL) {
 608                         NETDEBUG(KERN_INFO "IP: frag: no memory for new fragment!\n");
 609                         err = -ENOMEM;
 610                         goto fail;
 611                 }
 612
 613                 /*
 614                  *      Set up data on packet
 615                  */
 616
 617                 ip_copy_metadata(skb2, skb);
 618                 skb_reserve(skb2, ll_rs);
 619                 skb_put(skb2, len + hlen);
 620                 skb_reset_network_header(skb2);
 621                 skb2->transport_header = skb2->network_header + hlen;
 622
 623                 /*
 624                  *      Charge the memory for the fragment to any owner
 625                  *      it might possess
 626                  */
 627
 628                 if (skb->sk)
 629                         skb_set_owner_w(skb2, skb->sk);
 630
 631                 /*
 632                  *      Copy the packet header into the new buffer.
 633                  */
 634
 635                 skb_copy_from_linear_data(skb, skb_network_header(skb2), hlen);
 636
 637                 /*
 638                  *      Copy a block of the IP datagram.
 639                  */
 640                 if (skb_copy_bits(skb, ptr, skb_transport_header(skb2), len))
 641                         BUG();
 642                 left -= len;
 643
 644                 /*
 645                  *      Fill in the new header fields.
 646                  */
 647                 iph = ip_hdr(skb2);
 648                 iph->frag_off = htons((offset >> 3));
 649
 650                 /* ANK: dirty, but effective trick. Upgrade options only if
 651                  * the segment to be fragmented was THE FIRST (otherwise,
 652                  * options are already fixed) and make it ONCE
 653                  * on the initial skb, so that all the following fragments
 654                  * will inherit fixed options.
 655                  */
 656                 if (offset == 0)
 657                         ip_options_fragment(skb);
 658
 659                 /*
 660                  *      Added AC : If we are fragmenting a fragment that's not the
 661                  *                 last fragment then keep MF on each bit
 662                  */
 663                 if (left > 0 || not_last_frag)
 664                         iph->frag_off |= htons(IP_MF);
 665                 ptr += len;
 666                 offset += len;
 667
 668                 /*
 669                  *      Put this fragment into the sending queue.
 670                  */
 671                 iph->tot_len = htons(len + hlen);
 672
 673                 ip_send_check(iph);
 674
 675                 err = output(skb2);
 676                 if (err)
 677                         goto fail;
 678
 679                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGCREATES);
 680         }
 681         kfree_skb(skb);
 682         IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGOKS);
 683         return err;
 684
 685 fail:
 686         kfree_skb(skb);
 687         IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
 688         return err;
 689 }
 690
 691 EXPORT_SYMBOL(ip_fragment);
 692
 693 int
 694 ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
 695 {
 696         struct iovec *iov = from;
 697
 698         if (skb->ip_summed == CHECKSUM_PARTIAL) {
 699                 if (memcpy_fromiovecend(to, iov, offset, len) < 0)
 700                         return -EFAULT;
 701         } else {
 702                 __wsum csum = 0;
 703                 if (csum_partial_copy_fromiovecend(to, iov, offset, len, &csum) < 0)
 704                         return -EFAULT;
 705                 skb->csum = csum_block_add(skb->csum, csum, odd);
 706         }
 707         return 0;
 708 }
 709
 710 static inline __wsum
 711 csum_page(struct page *page, int offset, int copy)
 712 {
 713         char *kaddr;
 714         __wsum csum;
 715         kaddr = kmap(page);
 716         csum = csum_partial(kaddr + offset, copy, 0);
 717         kunmap(page);
 718         return csum;
 719 }
 720
 721 static inline int ip_ufo_append_data(struct sock *sk,
 722                         int getfrag(void *from, char *to, int offset, int len,
 723                                int odd, struct sk_buff *skb),
 724                         void *from, int length, int hh_len, int fragheaderlen,
 725                         int transhdrlen, int mtu, unsigned int flags)
 726 {
 727         struct sk_buff *skb;
 728         int err;
 729
 730         /* There is support for UDP fragmentation offload by network
 731          * device, so create one single skb packet containing complete
 732          * udp datagram
 733          */
 734         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL) {
 735                 skb = sock_alloc_send_skb(sk,
 736                         hh_len + fragheaderlen + transhdrlen + 20,
 737                         (flags & MSG_DONTWAIT), &err);
 738
 739                 if (skb == NULL)
 740                         return err;
 741
 742                 /* reserve space for Hardware header */
 743                 skb_reserve(skb, hh_len);
 744
 745                 /* create space for UDP/IP header */
 746                 skb_put(skb, fragheaderlen + transhdrlen);
 747
 748                 /* initialize network header pointer */
 749                 skb_reset_network_header(skb);
 750
 751                 /* initialize protocol header pointer */
 752                 skb->transport_header = skb->network_header + fragheaderlen;
 753
 754                 skb->ip_summed = CHECKSUM_PARTIAL;
 755                 skb->csum = 0;
 756                 sk->sk_sndmsg_off = 0;
 757
 758                 /* specify the length of each IP datagram fragment */
 759                 skb_shinfo(skb)->gso_size = mtu - fragheaderlen;
 760                 skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
 761                 __skb_queue_tail(&sk->sk_write_queue, skb);
 762         }
 763
 764         return skb_append_datato_frags(sk, skb, getfrag, from,
 765                                        (length - transhdrlen));
 766 }
 767
 768 /*
 769  *      ip_append_data() and ip_append_page() can make one large IP datagram
 770  *      from many pieces of data. Each pieces will be holded on the socket
 771  *      until ip_push_pending_frames() is called. Each piece can be a page
 772  *      or non-page data.
 773  *
 774  *      Not only UDP, other transport protocols - e.g. raw sockets - can use
 775  *      this interface potentially.
 776  *
 777  *      LATER: length must be adjusted by pad at tail, when it is required.
 778  */
 779 int ip_append_data(struct sock *sk,
 780                    int getfrag(void *from, char *to, int offset, int len,
 781                                int odd, struct sk_buff *skb),
 782                    void *from, int length, int transhdrlen,
 783                    struct ipcm_cookie *ipc, struct rtable **rtp,
 784                    unsigned int flags)
 785 {
 786         struct inet_sock *inet = inet_sk(sk);
 787         struct sk_buff *skb;
 788
 789         struct ip_options *opt = NULL;
 790         int hh_len;
 791         int exthdrlen;
 792         int mtu;
 793         int copy;
 794         int err;
 795         int offset = 0;
 796         unsigned int maxfraglen, fragheaderlen;
 797         int csummode = CHECKSUM_NONE;
 798         struct rtable *rt;
 799
 800         if (flags&MSG_PROBE)
 801                 return 0;
 802
 803         if (skb_queue_empty(&sk->sk_write_queue)) {
 804                 /*
 805                  * setup for corking.
 806                  */
 807                 opt = ipc->opt;
 808                 if (opt) {
 809                         if (inet->cork.opt == NULL) {
 810                                 inet->cork.opt = kmalloc(sizeof(struct ip_options) + 40, sk->sk_allocation);
 811                                 if (unlikely(inet->cork.opt == NULL))
 812                                         return -ENOBUFS;
 813                         }
 814                         memcpy(inet->cork.opt, opt, sizeof(struct ip_options)+opt->optlen);
 815                         inet->cork.flags |= IPCORK_OPT;
 816                         inet->cork.addr = ipc->addr;
 817                 }
 818                 rt = *rtp;
 819                 if (unlikely(!rt))
 820                         return -EFAULT;
 821                 /*
 822                  * We steal reference to this route, caller should not release it
 823                  */
 824                 *rtp = NULL;
 825                 inet->cork.fragsize = mtu = inet->pmtudisc == IP_PMTUDISC_PROBE ?
 826                                             rt->u.dst.dev->mtu :
 827                                             dst_mtu(rt->u.dst.path);
 828                 inet->cork.dst = &rt->u.dst;
 829                 inet->cork.length = 0;
 830                 sk->sk_sndmsg_page = NULL;
 831                 sk->sk_sndmsg_off = 0;
 832                 if ((exthdrlen = rt->u.dst.header_len) != 0) {
 833                         length += exthdrlen;
 834                         transhdrlen += exthdrlen;
 835                 }
 836         } else {
 837                 rt = (struct rtable *)inet->cork.dst;
 838                 if (inet->cork.flags & IPCORK_OPT)
 839                         opt = inet->cork.opt;
 840
 841                 transhdrlen = 0;
 842                 exthdrlen = 0;
 843                 mtu = inet->cork.fragsize;
 844         }
 845         hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
 846
 847         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
 848         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
 849
 850         if (inet->cork.length + length > 0xFFFF - fragheaderlen) {
 851                 ip_local_error(sk, EMSGSIZE, rt->rt_dst, inet->inet_dport,
 852                                mtu-exthdrlen);
 853                 return -EMSGSIZE;
 854         }
 855
 856         /*
 857          * transhdrlen > 0 means that this is the first fragment and we wish
 858          * it won't be fragmented in the future.
 859          */
 860         if (transhdrlen &&
 861             length + fragheaderlen <= mtu &&
 862             rt->u.dst.dev->features & NETIF_F_V4_CSUM &&
 863             !exthdrlen)
 864                 csummode = CHECKSUM_PARTIAL;
 865
 866         inet->cork.length += length;
 867         if (((length> mtu) || !skb_queue_empty(&sk->sk_write_queue)) &&
 868             (sk->sk_protocol == IPPROTO_UDP) &&
 869             (rt->u.dst.dev->features & NETIF_F_UFO)) {
 870                 err = ip_ufo_append_data(sk, getfrag, from, length, hh_len,
 871                                          fragheaderlen, transhdrlen, mtu,
 872                                          flags);
 873                 if (err)
 874                         goto error;
 875                 return 0;
 876         }
 877
 878         /* So, what's going on in the loop below?
 879          *
 880          * We use calculated fragment length to generate chained skb,
 881          * each of segments is IP fragment ready for sending to network after
 882          * adding appropriate IP header.
 883          */
 884
 885         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
 886                 goto alloc_new_skb;
 887
 888         while (length > 0) {
 889                 /* Check if the remaining data fits into current packet. */
 890                 copy = mtu - skb->len;
 891                 if (copy < length)
 892                         copy = maxfraglen - skb->len;
 893                 if (copy <= 0) {
 894                         char *data;
 895                         unsigned int datalen;
 896                         unsigned int fraglen;
 897                         unsigned int fraggap;
 898                         unsigned int alloclen;
 899                         struct sk_buff *skb_prev;
 900 alloc_new_skb:
 901                         skb_prev = skb;
 902                         if (skb_prev)
 903                                 fraggap = skb_prev->len - maxfraglen;
 904                         else
 905                                 fraggap = 0;
 906
 907                         /*
 908                          * If remaining data exceeds the mtu,
 909                          * we know we need more fragment(s).
 910                          */
 911                         datalen = length + fraggap;
 912                         if (datalen > mtu - fragheaderlen)
 913                                 datalen = maxfraglen - fragheaderlen;
 914                         fraglen = datalen + fragheaderlen;
 915
 916                         if ((flags & MSG_MORE) &&
 917                             !(rt->u.dst.dev->features&NETIF_F_SG))
 918                                 alloclen = mtu;
 919                         else
 920                                 alloclen = datalen + fragheaderlen;
 921
 922                         /* The last fragment gets additional space at tail.
 923                          * Note, with MSG_MORE we overallocate on fragments,
 924                          * because we have no idea what fragment will be
 925                          * the last.
 926                          */
 927                         if (datalen == length + fraggap)
 928                                 alloclen += rt->u.dst.trailer_len;
 929
 930                         if (transhdrlen) {
 931                                 skb = sock_alloc_send_skb(sk,
 932                                                 alloclen + hh_len + 15,
 933                                                 (flags & MSG_DONTWAIT), &err);
 934                         } else {
 935                                 skb = NULL;
 936                                 if (atomic_read(&sk->sk_wmem_alloc) <=
 937                                     2 * sk->sk_sndbuf)
 938                                         skb = sock_wmalloc(sk,
 939                                                            alloclen + hh_len + 15, 1,
 940                                                            sk->sk_allocation);
 941                                 if (unlikely(skb == NULL))
 942                                         err = -ENOBUFS;
 943                                 else
 944                                         /* only the initial fragment is
 945                                            time stamped */
 946                                         ipc->shtx.flags = 0;
 947                         }
 948                         if (skb == NULL)
 949                                 goto error;
 950
 951                         /*
 952                          *      Fill in the control structures
 953                          */
 954                         skb->ip_summed = csummode;
 955                         skb->csum = 0;
 956                         skb_reserve(skb, hh_len);
 957                         *skb_tx(skb) = ipc->shtx;
 958
 959                         /*
 960                          *      Find where to start putting bytes.
 961                          */
 962                         data = skb_put(skb, fraglen);
 963                         skb_set_network_header(skb, exthdrlen);
 964                         skb->transport_header = (skb->network_header +
 965                                                  fragheaderlen);
 966                         data += fragheaderlen;
 967
 968                         if (fraggap) {
 969                                 skb->csum = skb_copy_and_csum_bits(
 970                                         skb_prev, maxfraglen,
 971                                         data + transhdrlen, fraggap, 0);
 972                                 skb_prev->csum = csum_sub(skb_prev->csum,
 973                                                           skb->csum);
 974                                 data += fraggap;
 975                                 pskb_trim_unique(skb_prev, maxfraglen);
 976                         }
 977
 978                         copy = datalen - transhdrlen - fraggap;
 979                         if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
 980                                 err = -EFAULT;
 981                                 kfree_skb(skb);
 982                                 goto error;
 983                         }
 984
 985                         offset += copy;
 986                         length -= datalen - fraggap;
 987                         transhdrlen = 0;
 988                         exthdrlen = 0;
 989                         csummode = CHECKSUM_NONE;
 990
 991                         /*
 992                          * Put the packet on the pending queue.
 993                          */
 994                         __skb_queue_tail(&sk->sk_write_queue, skb);
 995                         continue;
 996                 }
 997
 998                 if (copy > length)
 999                         copy = length;
1000
1001                 if (!(rt->u.dst.dev->features&NETIF_F_SG)) {
1002                         unsigned int off;
1003
1004                         off = skb->len;
1005                         if (getfrag(from, skb_put(skb, copy),
1006                                         offset, copy, off, skb) < 0) {
1007                                 __skb_trim(skb, off);
1008                                 err = -EFAULT;
1009                                 goto error;
1010                         }
1011                 } else {
1012                         int i = skb_shinfo(skb)->nr_frags;
1013                         skb_frag_t *frag = &skb_shinfo(skb)->frags[i-1];
1014                         struct page *page = sk->sk_sndmsg_page;
1015                         int off = sk->sk_sndmsg_off;
1016                         unsigned int left;
1017
1018                         if (page && (left = PAGE_SIZE - off) > 0) {
1019                                 if (copy >= left)
1020                                         copy = left;
1021                                 if (page != frag->page) {
1022                                         if (i == MAX_SKB_FRAGS) {
1023                                                 err = -EMSGSIZE;
1024                                                 goto error;
1025                                         }
1026                                         get_page(page);
1027                                         skb_fill_page_desc(skb, i, page, sk->sk_sndmsg_off, 0);
1028                                         frag = &skb_shinfo(skb)->frags[i];
1029                                 }
1030                         } else if (i < MAX_SKB_FRAGS) {
1031                                 if (copy > PAGE_SIZE)
1032                                         copy = PAGE_SIZE;
1033                                 page = alloc_pages(sk->sk_allocation, 0);
1034                                 if (page == NULL)  {
1035                                         err = -ENOMEM;
1036                                         goto error;
1037                                 }
1038                                 sk->sk_sndmsg_page = page;
1039                                 sk->sk_sndmsg_off = 0;
1040
1041                                 skb_fill_page_desc(skb, i, page, 0, 0);
1042                                 frag = &skb_shinfo(skb)->frags[i];
1043                         } else {
1044                                 err = -EMSGSIZE;
1045                                 goto error;
1046                         }
1047                         if (getfrag(from, page_address(frag->page)+frag->page_offset+frag->size, offset, copy, skb->len, skb) < 0) {
1048                                 err = -EFAULT;
1049                                 goto error;
1050                         }
1051                         sk->sk_sndmsg_off += copy;
1052                         frag->size += copy;
1053                         skb->len += copy;
1054                         skb->data_len += copy;
1055                         skb->truesize += copy;
1056                         atomic_add(copy, &sk->sk_wmem_alloc);
1057                 }
1058                 offset += copy;
1059                 length -= copy;
1060         }
1061
1062         return 0;
1063
1064 error:
1065         inet->cork.length -= length;
1066         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1067         return err;
1068 }
1069
1070 ssize_t ip_append_page(struct sock *sk, struct page *page,
1071                        int offset, size_t size, int flags)
1072 {
1073         struct inet_sock *inet = inet_sk(sk);
1074         struct sk_buff *skb;
1075         struct rtable *rt;
1076         struct ip_options *opt = NULL;
1077         int hh_len;
1078         int mtu;
1079         int len;
1080         int err;
1081         unsigned int maxfraglen, fragheaderlen, fraggap;
1082
1083         if (inet->hdrincl)
1084                 return -EPERM;
1085
1086         if (flags&MSG_PROBE)
1087                 return 0;
1088
1089         if (skb_queue_empty(&sk->sk_write_queue))
1090                 return -EINVAL;
1091
1092         rt = (struct rtable *)inet->cork.dst;
1093         if (inet->cork.flags & IPCORK_OPT)
1094                 opt = inet->cork.opt;
1095
1096         if (!(rt->u.dst.dev->features&NETIF_F_SG))
1097                 return -EOPNOTSUPP;
1098
1099         hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
1100         mtu = inet->cork.fragsize;
1101
1102         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
1103         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
1104
1105         if (inet->cork.length + size > 0xFFFF - fragheaderlen) {
1106                 ip_local_error(sk, EMSGSIZE, rt->rt_dst, inet->inet_dport, mtu);
1107                 return -EMSGSIZE;
1108         }
1109
1110         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
1111                 return -EINVAL;
1112
1113         inet->cork.length += size;
1114         if ((sk->sk_protocol == IPPROTO_UDP) &&
1115             (rt->u.dst.dev->features & NETIF_F_UFO)) {
1116                 skb_shinfo(skb)->gso_size = mtu - fragheaderlen;
1117                 skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
1118         }
1119
1120
1121         while (size > 0) {
1122                 int i;
1123
1124                 if (skb_is_gso(skb))
1125                         len = size;
1126                 else {
1127
1128                         /* Check if the remaining data fits into current packet. */
1129                         len = mtu - skb->len;
1130                         if (len < size)
1131                                 len = maxfraglen - skb->len;
1132                 }
1133                 if (len <= 0) {
1134                         struct sk_buff *skb_prev;
1135                         int alloclen;
1136
1137                         skb_prev = skb;
1138                         fraggap = skb_prev->len - maxfraglen;
1139
1140                         alloclen = fragheaderlen + hh_len + fraggap + 15;
1141                         skb = sock_wmalloc(sk, alloclen, 1, sk->sk_allocation);
1142                         if (unlikely(!skb)) {
1143                                 err = -ENOBUFS;
1144                                 goto error;
1145                         }
1146
1147                         /*
1148                          *      Fill in the control structures
1149                          */
1150                         skb->ip_summed = CHECKSUM_NONE;
1151                         skb->csum = 0;
1152                         skb_reserve(skb, hh_len);
1153
1154                         /*
1155                          *      Find where to start putting bytes.
1156                          */
1157                         skb_put(skb, fragheaderlen + fraggap);
1158                         skb_reset_network_header(skb);
1159                         skb->transport_header = (skb->network_header +
1160                                                  fragheaderlen);
1161                         if (fraggap) {
1162                                 skb->csum = skb_copy_and_csum_bits(skb_prev,
1163                                                                    maxfraglen,
1164                                                     skb_transport_header(skb),
1165                                                                    fraggap, 0);
1166                                 skb_prev->csum = csum_sub(skb_prev->csum,
1167                                                           skb->csum);
1168                                 pskb_trim_unique(skb_prev, maxfraglen);
1169                         }
1170
1171                         /*
1172                          * Put the packet on the pending queue.
1173                          */
1174                         __skb_queue_tail(&sk->sk_write_queue, skb);
1175                         continue;
1176                 }
1177
1178                 i = skb_shinfo(skb)->nr_frags;
1179                 if (len > size)
1180                         len = size;
1181                 if (skb_can_coalesce(skb, i, page, offset)) {
1182                         skb_shinfo(skb)->frags[i-1].size += len;
1183                 } else if (i < MAX_SKB_FRAGS) {
1184                         get_page(page);
1185                         skb_fill_page_desc(skb, i, page, offset, len);
1186                 } else {
1187                         err = -EMSGSIZE;
1188                         goto error;
1189                 }
1190
1191                 if (skb->ip_summed == CHECKSUM_NONE) {
1192                         __wsum csum;
1193                         csum = csum_page(page, offset, len);
1194                         skb->csum = csum_block_add(skb->csum, csum, skb->len);
1195                 }
1196
1197                 skb->len += len;
1198                 skb->data_len += len;
1199                 skb->truesize += len;
1200                 atomic_add(len, &sk->sk_wmem_alloc);
1201                 offset += len;
1202                 size -= len;
1203         }
1204         return 0;
1205
1206 error:
1207         inet->cork.length -= size;
1208         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1209         return err;
1210 }
1211
1212 static void ip_cork_release(struct inet_sock *inet)
1213 {
1214         inet->cork.flags &= ~IPCORK_OPT;
1215         kfree(inet->cork.opt);
1216         inet->cork.opt = NULL;
1217         dst_release(inet->cork.dst);
1218         inet->cork.dst = NULL;
1219 }
1220
1221 /*
1222  *      Combined all pending IP fragments on the socket as one IP datagram
1223  *      and push them out.
1224  */
1225 int ip_push_pending_frames(struct sock *sk)
1226 {
1227         struct sk_buff *skb, *tmp_skb;
1228         struct sk_buff **tail_skb;
1229         struct inet_sock *inet = inet_sk(sk);
1230         struct net *net = sock_net(sk);
1231         struct ip_options *opt = NULL;
1232         struct rtable *rt = (struct rtable *)inet->cork.dst;
1233         struct iphdr *iph;
1234         __be16 df = 0;
1235         __u8 ttl;
1236         int err = 0;
1237
1238         if ((skb = __skb_dequeue(&sk->sk_write_queue)) == NULL)
1239                 goto out;
1240         tail_skb = &(skb_shinfo(skb)->frag_list);
1241
1242         /* move skb->data to ip header from ext header */
1243         if (skb->data < skb_network_header(skb))
1244                 __skb_pull(skb, skb_network_offset(skb));
1245         while ((tmp_skb = __skb_dequeue(&sk->sk_write_queue)) != NULL) {
1246                 __skb_pull(tmp_skb, skb_network_header_len(skb));
1247                 *tail_skb = tmp_skb;
1248                 tail_skb = &(tmp_skb->next);
1249                 skb->len += tmp_skb->len;
1250                 skb->data_len += tmp_skb->len;
1251                 skb->truesize += tmp_skb->truesize;
1252                 tmp_skb->destructor = NULL;
1253                 tmp_skb->sk = NULL;
1254         }
1255
1256         /* Unless user demanded real pmtu discovery (IP_PMTUDISC_DO), we allow
1257          * to fragment the frame generated here. No matter, what transforms
1258          * how transforms change size of the packet, it will come out.
1259          */
1260         if (inet->pmtudisc < IP_PMTUDISC_DO)
1261                 skb->local_df = 1;
1262
1263         /* DF bit is set when we want to see DF on outgoing frames.
1264          * If local_df is set too, we still allow to fragment this frame
1265          * locally. */
1266         if (inet->pmtudisc >= IP_PMTUDISC_DO ||
1267             (skb->len <= dst_mtu(&rt->u.dst) &&
1268              ip_dont_fragment(sk, &rt->u.dst)))
1269                 df = htons(IP_DF);
1270
1271         if (inet->cork.flags & IPCORK_OPT)
1272                 opt = inet->cork.opt;
1273
1274         if (rt->rt_type == RTN_MULTICAST)
1275                 ttl = inet->mc_ttl;
1276         else
1277                 ttl = ip_select_ttl(inet, &rt->u.dst);
1278
1279         iph = (struct iphdr *)skb->data;
1280         iph->version = 4;
1281         iph->ihl = 5;
1282         if (opt) {
1283                 iph->ihl += opt->optlen>>2;
1284                 ip_options_build(skb, opt, inet->cork.addr, rt, 0);
1285         }
1286         iph->tos = inet->tos;
1287         iph->frag_off = df;
1288         ip_select_ident(iph, &rt->u.dst, sk);
1289         iph->ttl = ttl;
1290         iph->protocol = sk->sk_protocol;
1291         iph->saddr = rt->rt_src;
1292         iph->daddr = rt->rt_dst;
1293
1294         skb->priority = sk->sk_priority;
1295         skb->mark = sk->sk_mark;
1296         /*
1297          * Steal rt from cork.dst to avoid a pair of atomic_inc/atomic_dec
1298          * on dst refcount
1299          */
1300         inet->cork.dst = NULL;
1301         skb_dst_set(skb, &rt->u.dst);
1302
1303         if (iph->protocol == IPPROTO_ICMP)
1304                 icmp_out_count(net, ((struct icmphdr *)
1305                         skb_transport_header(skb))->type);
1306
1307         /* Netfilter gets whole the not fragmented skb. */
1308         err = ip_local_out(skb);
1309         if (err) {
1310                 if (err > 0)
1311                         err = net_xmit_errno(err);
1312                 if (err)
1313                         goto error;
1314         }
1315
1316 out:
1317         ip_cork_release(inet);
1318         return err;
1319
1320 error:
1321         IP_INC_STATS(net, IPSTATS_MIB_OUTDISCARDS);
1322         goto out;
1323 }
1324
1325 /*
1326  *      Throw away all pending data on the socket.
1327  */
1328 void ip_flush_pending_frames(struct sock *sk)
1329 {
1330         struct sk_buff *skb;
1331
1332         while ((skb = __skb_dequeue_tail(&sk->sk_write_queue)) != NULL)
1333                 kfree_skb(skb);
1334
1335         ip_cork_release(inet_sk(sk));
1336 }
1337
1338
1339 /*
1340  *      Fetch data from kernel space and fill in checksum if needed.
1341  */
1342 static int ip_reply_glue_bits(void *dptr, char *to, int offset,
1343                               int len, int odd, struct sk_buff *skb)
1344 {
1345         __wsum csum;
1346
1347         csum = csum_partial_copy_nocheck(dptr+offset, to, len, 0);
1348         skb->csum = csum_block_add(skb->csum, csum, odd);
1349         return 0;
1350 }
1351
1352 /*
1353  *      Generic function to send a packet as reply to another packet.
1354  *      Used to send TCP resets so far. ICMP should use this function too.
1355  *
1356  *      Should run single threaded per socket because it uses the sock
1357  *      structure to pass arguments.
1358  */
1359 void ip_send_reply(struct sock *sk, struct sk_buff *skb, struct ip_reply_arg *arg,
1360                    unsigned int len)
1361 {
1362         struct inet_sock *inet = inet_sk(sk);
1363         struct {
1364                 struct ip_options       opt;
1365                 char                    data[40];
1366         } replyopts;
1367         struct ipcm_cookie ipc;
1368         __be32 daddr;
1369         struct rtable *rt = skb_rtable(skb);
1370
1371         if (ip_options_echo(&replyopts.opt, skb))
1372                 return;
1373
1374         daddr = ipc.addr = rt->rt_src;
1375         ipc.opt = NULL;
1376         ipc.shtx.flags = 0;
1377
1378         if (replyopts.opt.optlen) {
1379                 ipc.opt = &replyopts.opt;
1380
1381                 if (ipc.opt->srr)
1382                         daddr = replyopts.opt.faddr;
1383         }
1384
1385         {
1386                 struct flowi fl = { .oif = arg->bound_dev_if,
1387                                     .nl_u = { .ip4_u =
1388                                               { .daddr = daddr,
1389                                                 .saddr = rt->rt_spec_dst,
1390                                                 .tos = RT_TOS(ip_hdr(skb)->tos) } },
1391                                     /* Not quite clean, but right. */
1392                                     .uli_u = { .ports =
1393                                                { .sport = tcp_hdr(skb)->dest,
1394                                                  .dport = tcp_hdr(skb)->source } },
1395                                     .proto = sk->sk_protocol,
1396                                     .flags = ip_reply_arg_flowi_flags(arg) };
1397                 security_skb_classify_flow(skb, &fl);
1398                 if (ip_route_output_key(sock_net(sk), &rt, &fl))
1399                         return;
1400         }
1401
1402         /* And let IP do all the hard work.
1403
1404            This chunk is not reenterable, hence spinlock.
1405            Note that it uses the fact, that this function is called
1406            with locally disabled BH and that sk cannot be already spinlocked.
1407          */
1408         bh_lock_sock(sk);
1409         inet->tos = ip_hdr(skb)->tos;
1410         sk->sk_priority = skb->priority;
1411         sk->sk_protocol = ip_hdr(skb)->protocol;
1412         sk->sk_bound_dev_if = arg->bound_dev_if;
1413         ip_append_data(sk, ip_reply_glue_bits, arg->iov->iov_base, len, 0,
1414                        &ipc, &rt, MSG_DONTWAIT);
1415         if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {
1416                 if (arg->csumoffset >= 0)
1417                         *((__sum16 *)skb_transport_header(skb) +
1418                           arg->csumoffset) = csum_fold(csum_add(skb->csum,
1419                                                                 arg->csum));
1420                 skb->ip_summed = CHECKSUM_NONE;
1421                 ip_push_pending_frames(sk);
1422         }
1423
1424         bh_unlock_sock(sk);
1425
1426         ip_rt_put(rt);
1427 }
1428
1429 void __init ip_init(void)
1430 {
1431         ip_rt_init();
1432         inet_initpeers();
1433
1434 #if defined(CONFIG_IP_MULTICAST) && defined(CONFIG_PROC_FS)
1435         igmp_mc_proc_init();
1436 #endif
1437 }
1438
1439 EXPORT_SYMBOL(ip_generic_getfrag);
1440 EXPORT_SYMBOL(ip_queue_xmit);
1441 EXPORT_SYMBOL(ip_send_check);