net/ipv4/ip_output.c

   1 /*
   2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
   3  *              operating system.  INET is implemented using the  BSD Socket
   4  *              interface as the means of communication with the user level.
   5  *
   6  *              The Internet Protocol (IP) output module.
   7  *
   8  * Authors:     Ross Biro
   9  *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
  10  *              Donald Becker, <becker@super.org>
  11  *              Alan Cox, <Alan.Cox@linux.org>
  12  *              Richard Underwood
  13  *              Stefan Becker, <stefanb@yello.ping.de>
  14  *              Jorge Cwik, <jorge@laser.satlink.net>
  15  *              Arnt Gulbrandsen, <agulbra@nvg.unit.no>
  16  *              Hirokazu Takahashi, <taka@valinux.co.jp>
  17  *
  18  *      See ip_input.c for original log
  19  *
  20  *      Fixes:
  21  *              Alan Cox        :       Missing nonblock feature in ip_build_xmit.
  22  *              Mike Kilburn    :       htons() missing in ip_build_xmit.
  23  *              Bradford Johnson:       Fix faulty handling of some frames when
  24  *                                      no route is found.
  25  *              Alexander Demenshin:    Missing sk/skb free in ip_queue_xmit
  26  *                                      (in case if packet not accepted by
  27  *                                      output firewall rules)
  28  *              Mike McLagan    :       Routing by source
  29  *              Alexey Kuznetsov:       use new route cache
  30  *              Andi Kleen:             Fix broken PMTU recovery and remove
  31  *                                      some redundant tests.
  32  *      Vitaly E. Lavrov        :       Transparent proxy revived after year coma.
  33  *              Andi Kleen      :       Replace ip_reply with ip_send_reply.
  34  *              Andi Kleen      :       Split fast and slow ip_build_xmit path
  35  *                                      for decreased register pressure on x86
  36  *                                      and more readibility.
  37  *              Marc Boucher    :       When call_out_firewall returns FW_QUEUE,
  38  *                                      silently drop skb instead of failing with -EPERM.
  39  *              Detlev Wengorz  :       Copy protocol for fragments.
  40  *              Hirokazu Takahashi:     HW checksumming for outgoing UDP
  41  *                                      datagrams.
  42  *              Hirokazu Takahashi:     sendfile() on UDP works now.
  43  */
  44
  45 #include <asm/uaccess.h>
  46 #include <linux/module.h>
  47 #include <linux/types.h>
  48 #include <linux/kernel.h>
  49 #include <linux/mm.h>
  50 #include <linux/string.h>
  51 #include <linux/errno.h>
  52 #include <linux/highmem.h>
  53 #include <linux/slab.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 EXPORT_SYMBOL(sysctl_ip_default_ttl);
  85
  86 /* Generate a checksum for an outgoing IP datagram. */
  87 void ip_send_check(struct iphdr *iph)
  88 {
  89         iph->check = 0;
  90         iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
  91 }
  92 EXPORT_SYMBOL(ip_send_check);
  93
  94 int __ip_local_out(struct sk_buff *skb)
  95 {
  96         struct iphdr *iph = ip_hdr(skb);
  97
  98         iph->tot_len = htons(skb->len);
  99         ip_send_check(iph);
 100         return nf_hook(NFPROTO_IPV4, NF_INET_LOCAL_OUT, skb, NULL,
 101                        skb_dst(skb)->dev, dst_output);
 102 }
 103
 104 int ip_local_out_sk(struct sock *sk, struct sk_buff *skb)
 105 {
 106         int err;
 107
 108         err = __ip_local_out(skb);
 109         if (likely(err == 1))
 110                 err = dst_output_sk(sk, skb);
 111
 112         return err;
 113 }
 114 EXPORT_SYMBOL_GPL(ip_local_out_sk);
 115
 116 static inline int ip_select_ttl(struct inet_sock *inet, struct dst_entry *dst)
 117 {
 118         int ttl = inet->uc_ttl;
 119
 120         if (ttl < 0)
 121                 ttl = ip4_dst_hoplimit(dst);
 122         return ttl;
 123 }
 124
 125 /*
 126  *              Add an ip header to a skbuff and send it out.
 127  *
 128  */
 129 int ip_build_and_send_pkt(struct sk_buff *skb, struct sock *sk,
 130                           __be32 saddr, __be32 daddr, struct ip_options_rcu *opt)
 131 {
 132         struct inet_sock *inet = inet_sk(sk);
 133         struct rtable *rt = skb_rtable(skb);
 134         struct iphdr *iph;
 135
 136         /* Build the IP header. */
 137         skb_push(skb, sizeof(struct iphdr) + (opt ? opt->opt.optlen : 0));
 138         skb_reset_network_header(skb);
 139         iph = ip_hdr(skb);
 140         iph->version  = 4;
 141         iph->ihl      = 5;
 142         iph->tos      = inet->tos;
 143         if (ip_dont_fragment(sk, &rt->dst))
 144                 iph->frag_off = htons(IP_DF);
 145         else
 146                 iph->frag_off = 0;
 147         iph->ttl      = ip_select_ttl(inet, &rt->dst);
 148         iph->daddr    = (opt && opt->opt.srr ? opt->opt.faddr : daddr);
 149         iph->saddr    = saddr;
 150         iph->protocol = sk->sk_protocol;
 151         ip_select_ident(skb, sk);
 152
 153         if (opt && opt->opt.optlen) {
 154                 iph->ihl += opt->opt.optlen>>2;
 155                 ip_options_build(skb, &opt->opt, daddr, rt, 0);
 156         }
 157
 158         skb->priority = sk->sk_priority;
 159         skb->mark = sk->sk_mark;
 160
 161         /* Send it out. */
 162         return ip_local_out(skb);
 163 }
 164 EXPORT_SYMBOL_GPL(ip_build_and_send_pkt);
 165
 166 static inline int ip_finish_output2(struct sk_buff *skb)
 167 {
 168         struct dst_entry *dst = skb_dst(skb);
 169         struct rtable *rt = (struct rtable *)dst;
 170         struct net_device *dev = dst->dev;
 171         unsigned int hh_len = LL_RESERVED_SPACE(dev);
 172         struct neighbour *neigh;
 173         u32 nexthop;
 174
 175         if (rt->rt_type == RTN_MULTICAST) {
 176                 IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUTMCAST, skb->len);
 177         } else if (rt->rt_type == RTN_BROADCAST)
 178                 IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUTBCAST, skb->len);
 179
 180         /* Be paranoid, rather than too clever. */
 181         if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) {
 182                 struct sk_buff *skb2;
 183
 184                 skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev));
 185                 if (skb2 == NULL) {
 186                         kfree_skb(skb);
 187                         return -ENOMEM;
 188                 }
 189                 if (skb->sk)
 190                         skb_set_owner_w(skb2, skb->sk);
 191                 consume_skb(skb);
 192                 skb = skb2;
 193         }
 194
 195         rcu_read_lock_bh();
 196         nexthop = (__force u32) rt_nexthop(rt, ip_hdr(skb)->daddr);
 197         neigh = __ipv4_neigh_lookup_noref(dev, nexthop);
 198         if (unlikely(!neigh))
 199                 neigh = __neigh_create(&arp_tbl, &nexthop, dev, false);
 200         if (!IS_ERR(neigh)) {
 201                 int res = dst_neigh_output(dst, neigh, skb);
 202
 203                 rcu_read_unlock_bh();
 204                 return res;
 205         }
 206         rcu_read_unlock_bh();
 207
 208         net_dbg_ratelimited("%s: No header cache and no neighbour!\n",
 209                             __func__);
 210         kfree_skb(skb);
 211         return -EINVAL;
 212 }
 213
 214 static int ip_finish_output_gso(struct sk_buff *skb)
 215 {
 216         netdev_features_t features;
 217         struct sk_buff *segs;
 218         int ret = 0;
 219
 220         /* common case: locally created skb or seglen is <= mtu */
 221         if (((IPCB(skb)->flags & IPSKB_FORWARDED) == 0) ||
 222               skb_gso_network_seglen(skb) <= ip_skb_dst_mtu(skb))
 223                 return ip_finish_output2(skb);
 224
 225         /* Slowpath -  GSO segment length is exceeding the dst MTU.
 226          *
 227          * This can happen in two cases:
 228          * 1) TCP GRO packet, DF bit not set
 229          * 2) skb arrived via virtio-net, we thus get TSO/GSO skbs directly
 230          * from host network stack.
 231          */
 232         features = netif_skb_features(skb);
 233         segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK);
 234         if (IS_ERR_OR_NULL(segs)) {
 235                 kfree_skb(skb);
 236                 return -ENOMEM;
 237         }
 238
 239         consume_skb(skb);
 240
 241         do {
 242                 struct sk_buff *nskb = segs->next;
 243                 int err;
 244
 245                 segs->next = NULL;
 246                 err = ip_fragment(segs, ip_finish_output2);
 247
 248                 if (err && ret == 0)
 249                         ret = err;
 250                 segs = nskb;
 251         } while (segs);
 252
 253         return ret;
 254 }
 255
 256 static int ip_finish_output(struct sk_buff *skb)
 257 {
 258 #if defined(CONFIG_NETFILTER) && defined(CONFIG_XFRM)
 259         /* Policy lookup after SNAT yielded a new policy */
 260         if (skb_dst(skb)->xfrm != NULL) {
 261                 IPCB(skb)->flags |= IPSKB_REROUTED;
 262                 return dst_output(skb);
 263         }
 264 #endif
 265         if (skb_is_gso(skb))
 266                 return ip_finish_output_gso(skb);
 267
 268         if (skb->len > ip_skb_dst_mtu(skb))
 269                 return ip_fragment(skb, ip_finish_output2);
 270
 271         return ip_finish_output2(skb);
 272 }
 273
 274 int ip_mc_output(struct sock *sk, struct sk_buff *skb)
 275 {
 276         struct rtable *rt = skb_rtable(skb);
 277         struct net_device *dev = rt->dst.dev;
 278
 279         /*
 280          *      If the indicated interface is up and running, send the packet.
 281          */
 282         IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUT, skb->len);
 283
 284         skb->dev = dev;
 285         skb->protocol = htons(ETH_P_IP);
 286
 287         /*
 288          *      Multicasts are looped back for other local users
 289          */
 290
 291         if (rt->rt_flags&RTCF_MULTICAST) {
 292                 if (sk_mc_loop(sk)
 293 #ifdef CONFIG_IP_MROUTE
 294                 /* Small optimization: do not loopback not local frames,
 295                    which returned after forwarding; they will be  dropped
 296                    by ip_mr_input in any case.
 297                    Note, that local frames are looped back to be delivered
 298                    to local recipients.
 299
 300                    This check is duplicated in ip_mr_input at the moment.
 301                  */
 302                     &&
 303                     ((rt->rt_flags & RTCF_LOCAL) ||
 304                      !(IPCB(skb)->flags & IPSKB_FORWARDED))
 305 #endif
 306                    ) {
 307                         struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
 308                         if (newskb)
 309                                 NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING,
 310                                         newskb, NULL, newskb->dev,
 311                                         dev_loopback_xmit);
 312                 }
 313
 314                 /* Multicasts with ttl 0 must not go beyond the host */
 315
 316                 if (ip_hdr(skb)->ttl == 0) {
 317                         kfree_skb(skb);
 318                         return 0;
 319                 }
 320         }
 321
 322         if (rt->rt_flags&RTCF_BROADCAST) {
 323                 struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
 324                 if (newskb)
 325                         NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING, newskb,
 326                                 NULL, newskb->dev, dev_loopback_xmit);
 327         }
 328
 329         return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING, skb, NULL,
 330                             skb->dev, ip_finish_output,
 331                             !(IPCB(skb)->flags & IPSKB_REROUTED));
 332 }
 333
 334 int ip_output(struct sock *sk, struct sk_buff *skb)
 335 {
 336         struct net_device *dev = skb_dst(skb)->dev;
 337
 338         IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUT, skb->len);
 339
 340         skb->dev = dev;
 341         skb->protocol = htons(ETH_P_IP);
 342
 343         return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING, skb, NULL, dev,
 344                             ip_finish_output,
 345                             !(IPCB(skb)->flags & IPSKB_REROUTED));
 346 }
 347
 348 /*
 349  * copy saddr and daddr, possibly using 64bit load/stores
 350  * Equivalent to :
 351  *   iph->saddr = fl4->saddr;
 352  *   iph->daddr = fl4->daddr;
 353  */
 354 static void ip_copy_addrs(struct iphdr *iph, const struct flowi4 *fl4)
 355 {
 356         BUILD_BUG_ON(offsetof(typeof(*fl4), daddr) !=
 357                      offsetof(typeof(*fl4), saddr) + sizeof(fl4->saddr));
 358         memcpy(&iph->saddr, &fl4->saddr,
 359                sizeof(fl4->saddr) + sizeof(fl4->daddr));
 360 }
 361
 362 /* Note: skb->sk can be different from sk, in case of tunnels */
 363 int ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl)
 364 {
 365         struct inet_sock *inet = inet_sk(sk);
 366         struct ip_options_rcu *inet_opt;
 367         struct flowi4 *fl4;
 368         struct rtable *rt;
 369         struct iphdr *iph;
 370         int res;
 371
 372         /* Skip all of this if the packet is already routed,
 373          * f.e. by something like SCTP.
 374          */
 375         rcu_read_lock();
 376         inet_opt = rcu_dereference(inet->inet_opt);
 377         fl4 = &fl->u.ip4;
 378         rt = skb_rtable(skb);
 379         if (rt != NULL)
 380                 goto packet_routed;
 381
 382         /* Make sure we can route this packet. */
 383         rt = (struct rtable *)__sk_dst_check(sk, 0);
 384         if (rt == NULL) {
 385                 __be32 daddr;
 386
 387                 /* Use correct destination address if we have options. */
 388                 daddr = inet->inet_daddr;
 389                 if (inet_opt && inet_opt->opt.srr)
 390                         daddr = inet_opt->opt.faddr;
 391
 392                 /* If this fails, retransmit mechanism of transport layer will
 393                  * keep trying until route appears or the connection times
 394                  * itself out.
 395                  */
 396                 rt = ip_route_output_ports(sock_net(sk), fl4, sk,
 397                                            daddr, inet->inet_saddr,
 398                                            inet->inet_dport,
 399                                            inet->inet_sport,
 400                                            sk->sk_protocol,
 401                                            RT_CONN_FLAGS(sk),
 402                                            sk->sk_bound_dev_if);
 403                 if (IS_ERR(rt))
 404                         goto no_route;
 405                 sk_setup_caps(sk, &rt->dst);
 406         }
 407         skb_dst_set_noref(skb, &rt->dst);
 408
 409 packet_routed:
 410         if (inet_opt && inet_opt->opt.is_strictroute && rt->rt_uses_gateway)
 411                 goto no_route;
 412
 413         /* OK, we know where to send it, allocate and build IP header. */
 414         skb_push(skb, sizeof(struct iphdr) + (inet_opt ? inet_opt->opt.optlen : 0));
 415         skb_reset_network_header(skb);
 416         iph = ip_hdr(skb);
 417         *((__be16 *)iph) = htons((4 << 12) | (5 << 8) | (inet->tos & 0xff));
 418         if (ip_dont_fragment(sk, &rt->dst) && !skb->ignore_df)
 419                 iph->frag_off = htons(IP_DF);
 420         else
 421                 iph->frag_off = 0;
 422         iph->ttl      = ip_select_ttl(inet, &rt->dst);
 423         iph->protocol = sk->sk_protocol;
 424         ip_copy_addrs(iph, fl4);
 425
 426         /* Transport layer set skb->h.foo itself. */
 427
 428         if (inet_opt && inet_opt->opt.optlen) {
 429                 iph->ihl += inet_opt->opt.optlen >> 2;
 430                 ip_options_build(skb, &inet_opt->opt, inet->inet_daddr, rt, 0);
 431         }
 432
 433         ip_select_ident_segs(skb, sk, skb_shinfo(skb)->gso_segs ?: 1);
 434
 435         /* TODO : should we use skb->sk here instead of sk ? */
 436         skb->priority = sk->sk_priority;
 437         skb->mark = sk->sk_mark;
 438
 439         res = ip_local_out(skb);
 440         rcu_read_unlock();
 441         return res;
 442
 443 no_route:
 444         rcu_read_unlock();
 445         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);
 446         kfree_skb(skb);
 447         return -EHOSTUNREACH;
 448 }
 449 EXPORT_SYMBOL(ip_queue_xmit);
 450
 451
 452 static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
 453 {
 454         to->pkt_type = from->pkt_type;
 455         to->priority = from->priority;
 456         to->protocol = from->protocol;
 457         skb_dst_drop(to);
 458         skb_dst_copy(to, from);
 459         to->dev = from->dev;
 460         to->mark = from->mark;
 461
 462         /* Copy the flags to each fragment. */
 463         IPCB(to)->flags = IPCB(from)->flags;
 464
 465 #ifdef CONFIG_NET_SCHED
 466         to->tc_index = from->tc_index;
 467 #endif
 468         nf_copy(to, from);
 469 #if defined(CONFIG_IP_VS) || defined(CONFIG_IP_VS_MODULE)
 470         to->ipvs_property = from->ipvs_property;
 471 #endif
 472         skb_copy_secmark(to, from);
 473 }
 474
 475 /*
 476  *      This IP datagram is too large to be sent in one piece.  Break it up into
 477  *      smaller pieces (each of size equal to IP header plus
 478  *      a block of the data of the original IP data part) that will yet fit in a
 479  *      single device frame, and queue such a frame for sending.
 480  */
 481
 482 int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
 483 {
 484         struct iphdr *iph;
 485         int ptr;
 486         struct net_device *dev;
 487         struct sk_buff *skb2;
 488         unsigned int mtu, hlen, left, len, ll_rs;
 489         int offset;
 490         __be16 not_last_frag;
 491         struct rtable *rt = skb_rtable(skb);
 492         int err = 0;
 493
 494         dev = rt->dst.dev;
 495
 496         /*
 497          *      Point into the IP datagram header.
 498          */
 499
 500         iph = ip_hdr(skb);
 501
 502         mtu = ip_skb_dst_mtu(skb);
 503         if (unlikely(((iph->frag_off & htons(IP_DF)) && !skb->ignore_df) ||
 504                      (IPCB(skb)->frag_max_size &&
 505                       IPCB(skb)->frag_max_size > mtu))) {
 506                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
 507                 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
 508                           htonl(mtu));
 509                 kfree_skb(skb);
 510                 return -EMSGSIZE;
 511         }
 512
 513         /*
 514          *      Setup starting values.
 515          */
 516
 517         hlen = iph->ihl * 4;
 518         mtu = mtu - hlen;       /* Size of data space */
 519 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
 520         if (skb->nf_bridge)
 521                 mtu -= nf_bridge_mtu_reduction(skb);
 522 #endif
 523         IPCB(skb)->flags |= IPSKB_FRAG_COMPLETE;
 524
 525         /* When frag_list is given, use it. First, check its validity:
 526          * some transformers could create wrong frag_list or break existing
 527          * one, it is not prohibited. In this case fall back to copying.
 528          *
 529          * LATER: this step can be merged to real generation of fragments,
 530          * we can switch to copy when see the first bad fragment.
 531          */
 532         if (skb_has_frag_list(skb)) {
 533                 struct sk_buff *frag, *frag2;
 534                 int first_len = skb_pagelen(skb);
 535
 536                 if (first_len - hlen > mtu ||
 537                     ((first_len - hlen) & 7) ||
 538                     ip_is_fragment(iph) ||
 539                     skb_cloned(skb))
 540                         goto slow_path;
 541
 542                 skb_walk_frags(skb, frag) {
 543                         /* Correct geometry. */
 544                         if (frag->len > mtu ||
 545                             ((frag->len & 7) && frag->next) ||
 546                             skb_headroom(frag) < hlen)
 547                                 goto slow_path_clean;
 548
 549                         /* Partially cloned skb? */
 550                         if (skb_shared(frag))
 551                                 goto slow_path_clean;
 552
 553                         BUG_ON(frag->sk);
 554                         if (skb->sk) {
 555                                 frag->sk = skb->sk;
 556                                 frag->destructor = sock_wfree;
 557                         }
 558                         skb->truesize -= frag->truesize;
 559                 }
 560
 561                 /* Everything is OK. Generate! */
 562
 563                 err = 0;
 564                 offset = 0;
 565                 frag = skb_shinfo(skb)->frag_list;
 566                 skb_frag_list_init(skb);
 567                 skb->data_len = first_len - skb_headlen(skb);
 568                 skb->len = first_len;
 569                 iph->tot_len = htons(first_len);
 570                 iph->frag_off = htons(IP_MF);
 571                 ip_send_check(iph);
 572
 573                 for (;;) {
 574                         /* Prepare header of the next frame,
 575                          * before previous one went down. */
 576                         if (frag) {
 577                                 frag->ip_summed = CHECKSUM_NONE;
 578                                 skb_reset_transport_header(frag);
 579                                 __skb_push(frag, hlen);
 580                                 skb_reset_network_header(frag);
 581                                 memcpy(skb_network_header(frag), iph, hlen);
 582                                 iph = ip_hdr(frag);
 583                                 iph->tot_len = htons(frag->len);
 584                                 ip_copy_metadata(frag, skb);
 585                                 if (offset == 0)
 586                                         ip_options_fragment(frag);
 587                                 offset += skb->len - hlen;
 588                                 iph->frag_off = htons(offset>>3);
 589                                 if (frag->next != NULL)
 590                                         iph->frag_off |= htons(IP_MF);
 591                                 /* Ready, complete checksum */
 592                                 ip_send_check(iph);
 593                         }
 594
 595                         err = output(skb);
 596
 597                         if (!err)
 598                                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGCREATES);
 599                         if (err || !frag)
 600                                 break;
 601
 602                         skb = frag;
 603                         frag = skb->next;
 604                         skb->next = NULL;
 605                 }
 606
 607                 if (err == 0) {
 608                         IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGOKS);
 609                         return 0;
 610                 }
 611
 612                 while (frag) {
 613                         skb = frag->next;
 614                         kfree_skb(frag);
 615                         frag = skb;
 616                 }
 617                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
 618                 return err;
 619
 620 slow_path_clean:
 621                 skb_walk_frags(skb, frag2) {
 622                         if (frag2 == frag)
 623                                 break;
 624                         frag2->sk = NULL;
 625                         frag2->destructor = NULL;
 626                         skb->truesize += frag2->truesize;
 627                 }
 628         }
 629
 630 slow_path:
 631         /* for offloaded checksums cleanup checksum before fragmentation */
 632         if ((skb->ip_summed == CHECKSUM_PARTIAL) && skb_checksum_help(skb))
 633                 goto fail;
 634         iph = ip_hdr(skb);
 635
 636         left = skb->len - hlen;         /* Space per frame */
 637         ptr = hlen;             /* Where to start from */
 638
 639         /* for bridged IP traffic encapsulated inside f.e. a vlan header,
 640          * we need to make room for the encapsulating header
 641          */
 642         ll_rs = LL_RESERVED_SPACE_EXTRA(rt->dst.dev, nf_bridge_pad(skb));
 643
 644         /*
 645          *      Fragment the datagram.
 646          */
 647
 648         offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3;
 649         not_last_frag = iph->frag_off & htons(IP_MF);
 650
 651         /*
 652          *      Keep copying data until we run out.
 653          */
 654
 655         while (left > 0) {
 656                 len = left;
 657                 /* IF: it doesn't fit, use 'mtu' - the data space left */
 658                 if (len > mtu)
 659                         len = mtu;
 660                 /* IF: we are not sending up to and including the packet end
 661                    then align the next start on an eight byte boundary */
 662                 if (len < left) {
 663                         len &= ~7;
 664                 }
 665
 666                 /* Allocate buffer */
 667                 skb2 = alloc_skb(len + hlen + ll_rs, GFP_ATOMIC);
 668                 if (!skb2) {
 669                         err = -ENOMEM;
 670                         goto fail;
 671                 }
 672
 673                 /*
 674                  *      Set up data on packet
 675                  */
 676
 677                 ip_copy_metadata(skb2, skb);
 678                 skb_reserve(skb2, ll_rs);
 679                 skb_put(skb2, len + hlen);
 680                 skb_reset_network_header(skb2);
 681                 skb2->transport_header = skb2->network_header + hlen;
 682
 683                 /*
 684                  *      Charge the memory for the fragment to any owner
 685                  *      it might possess
 686                  */
 687
 688                 if (skb->sk)
 689                         skb_set_owner_w(skb2, skb->sk);
 690
 691                 /*
 692                  *      Copy the packet header into the new buffer.
 693                  */
 694
 695                 skb_copy_from_linear_data(skb, skb_network_header(skb2), hlen);
 696
 697                 /*
 698                  *      Copy a block of the IP datagram.
 699                  */
 700                 if (skb_copy_bits(skb, ptr, skb_transport_header(skb2), len))
 701                         BUG();
 702                 left -= len;
 703
 704                 /*
 705                  *      Fill in the new header fields.
 706                  */
 707                 iph = ip_hdr(skb2);
 708                 iph->frag_off = htons((offset >> 3));
 709
 710                 /* ANK: dirty, but effective trick. Upgrade options only if
 711                  * the segment to be fragmented was THE FIRST (otherwise,
 712                  * options are already fixed) and make it ONCE
 713                  * on the initial skb, so that all the following fragments
 714                  * will inherit fixed options.
 715                  */
 716                 if (offset == 0)
 717                         ip_options_fragment(skb);
 718
 719                 /*
 720                  *      Added AC : If we are fragmenting a fragment that's not the
 721                  *                 last fragment then keep MF on each bit
 722                  */
 723                 if (left > 0 || not_last_frag)
 724                         iph->frag_off |= htons(IP_MF);
 725                 ptr += len;
 726                 offset += len;
 727
 728                 /*
 729                  *      Put this fragment into the sending queue.
 730                  */
 731                 iph->tot_len = htons(len + hlen);
 732
 733                 ip_send_check(iph);
 734
 735                 err = output(skb2);
 736                 if (err)
 737                         goto fail;
 738
 739                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGCREATES);
 740         }
 741         consume_skb(skb);
 742         IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGOKS);
 743         return err;
 744
 745 fail:
 746         kfree_skb(skb);
 747         IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
 748         return err;
 749 }
 750 EXPORT_SYMBOL(ip_fragment);
 751
 752 int
 753 ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
 754 {
 755         struct msghdr *msg = from;
 756
 757         if (skb->ip_summed == CHECKSUM_PARTIAL) {
 758                 /* XXX: stripping const */
 759                 if (memcpy_fromiovecend(to, (struct iovec *)msg->msg_iter.iov, offset, len) < 0)
 760                         return -EFAULT;
 761         } else {
 762                 __wsum csum = 0;
 763                 /* XXX: stripping const */
 764                 if (csum_partial_copy_fromiovecend(to, (struct iovec *)msg->msg_iter.iov, offset, len, &csum) < 0)
 765                         return -EFAULT;
 766                 skb->csum = csum_block_add(skb->csum, csum, odd);
 767         }
 768         return 0;
 769 }
 770 EXPORT_SYMBOL(ip_generic_getfrag);
 771
 772 static inline __wsum
 773 csum_page(struct page *page, int offset, int copy)
 774 {
 775         char *kaddr;
 776         __wsum csum;
 777         kaddr = kmap(page);
 778         csum = csum_partial(kaddr + offset, copy, 0);
 779         kunmap(page);
 780         return csum;
 781 }
 782
 783 static inline int ip_ufo_append_data(struct sock *sk,
 784                         struct sk_buff_head *queue,
 785                         int getfrag(void *from, char *to, int offset, int len,
 786                                int odd, struct sk_buff *skb),
 787                         void *from, int length, int hh_len, int fragheaderlen,
 788                         int transhdrlen, int maxfraglen, unsigned int flags)
 789 {
 790         struct sk_buff *skb;
 791         int err;
 792
 793         /* There is support for UDP fragmentation offload by network
 794          * device, so create one single skb packet containing complete
 795          * udp datagram
 796          */
 797         if ((skb = skb_peek_tail(queue)) == NULL) {
 798                 skb = sock_alloc_send_skb(sk,
 799                         hh_len + fragheaderlen + transhdrlen + 20,
 800                         (flags & MSG_DONTWAIT), &err);
 801
 802                 if (skb == NULL)
 803                         return err;
 804
 805                 /* reserve space for Hardware header */
 806                 skb_reserve(skb, hh_len);
 807
 808                 /* create space for UDP/IP header */
 809                 skb_put(skb, fragheaderlen + transhdrlen);
 810
 811                 /* initialize network header pointer */
 812                 skb_reset_network_header(skb);
 813
 814                 /* initialize protocol header pointer */
 815                 skb->transport_header = skb->network_header + fragheaderlen;
 816
 817                 skb->csum = 0;
 818
 819
 820                 __skb_queue_tail(queue, skb);
 821         } else if (skb_is_gso(skb)) {
 822                 goto append;
 823         }
 824
 825         skb->ip_summed = CHECKSUM_PARTIAL;
 826         /* specify the length of each IP datagram fragment */
 827         skb_shinfo(skb)->gso_size = maxfraglen - fragheaderlen;
 828         skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
 829
 830 append:
 831         return skb_append_datato_frags(sk, skb, getfrag, from,
 832                                        (length - transhdrlen));
 833 }
 834
 835 static int __ip_append_data(struct sock *sk,
 836                             struct flowi4 *fl4,
 837                             struct sk_buff_head *queue,
 838                             struct inet_cork *cork,
 839                             struct page_frag *pfrag,
 840                             int getfrag(void *from, char *to, int offset,
 841                                         int len, int odd, struct sk_buff *skb),
 842                             void *from, int length, int transhdrlen,
 843                             unsigned int flags)
 844 {
 845         struct inet_sock *inet = inet_sk(sk);
 846         struct sk_buff *skb;
 847
 848         struct ip_options *opt = cork->opt;
 849         int hh_len;
 850         int exthdrlen;
 851         int mtu;
 852         int copy;
 853         int err;
 854         int offset = 0;
 855         unsigned int maxfraglen, fragheaderlen, maxnonfragsize;
 856         int csummode = CHECKSUM_NONE;
 857         struct rtable *rt = (struct rtable *)cork->dst;
 858         u32 tskey = 0;
 859
 860         skb = skb_peek_tail(queue);
 861
 862         exthdrlen = !skb ? rt->dst.header_len : 0;
 863         mtu = cork->fragsize;
 864         if (cork->tx_flags & SKBTX_ANY_SW_TSTAMP &&
 865             sk->sk_tsflags & SOF_TIMESTAMPING_OPT_ID)
 866                 tskey = sk->sk_tskey++;
 867
 868         hh_len = LL_RESERVED_SPACE(rt->dst.dev);
 869
 870         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
 871         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
 872         maxnonfragsize = ip_sk_ignore_df(sk) ? 0xFFFF : mtu;
 873
 874         if (cork->length + length > maxnonfragsize - fragheaderlen) {
 875                 ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
 876                                mtu - (opt ? opt->optlen : 0));
 877                 return -EMSGSIZE;
 878         }
 879
 880         /*
 881          * transhdrlen > 0 means that this is the first fragment and we wish
 882          * it won't be fragmented in the future.
 883          */
 884         if (transhdrlen &&
 885             length + fragheaderlen <= mtu &&
 886             rt->dst.dev->features & NETIF_F_V4_CSUM &&
 887             !exthdrlen)
 888                 csummode = CHECKSUM_PARTIAL;
 889
 890         cork->length += length;
 891         if (((length > mtu) || (skb && skb_is_gso(skb))) &&
 892             (sk->sk_protocol == IPPROTO_UDP) &&
 893             (rt->dst.dev->features & NETIF_F_UFO) && !rt->dst.header_len) {
 894                 err = ip_ufo_append_data(sk, queue, getfrag, from, length,
 895                                          hh_len, fragheaderlen, transhdrlen,
 896                                          maxfraglen, flags);
 897                 if (err)
 898                         goto error;
 899                 return 0;
 900         }
 901
 902         /* So, what's going on in the loop below?
 903          *
 904          * We use calculated fragment length to generate chained skb,
 905          * each of segments is IP fragment ready for sending to network after
 906          * adding appropriate IP header.
 907          */
 908
 909         if (!skb)
 910                 goto alloc_new_skb;
 911
 912         while (length > 0) {
 913                 /* Check if the remaining data fits into current packet. */
 914                 copy = mtu - skb->len;
 915                 if (copy < length)
 916                         copy = maxfraglen - skb->len;
 917                 if (copy <= 0) {
 918                         char *data;
 919                         unsigned int datalen;
 920                         unsigned int fraglen;
 921                         unsigned int fraggap;
 922                         unsigned int alloclen;
 923                         struct sk_buff *skb_prev;
 924 alloc_new_skb:
 925                         skb_prev = skb;
 926                         if (skb_prev)
 927                                 fraggap = skb_prev->len - maxfraglen;
 928                         else
 929                                 fraggap = 0;
 930
 931                         /*
 932                          * If remaining data exceeds the mtu,
 933                          * we know we need more fragment(s).
 934                          */
 935                         datalen = length + fraggap;
 936                         if (datalen > mtu - fragheaderlen)
 937                                 datalen = maxfraglen - fragheaderlen;
 938                         fraglen = datalen + fragheaderlen;
 939
 940                         if ((flags & MSG_MORE) &&
 941                             !(rt->dst.dev->features&NETIF_F_SG))
 942                                 alloclen = mtu;
 943                         else
 944                                 alloclen = fraglen;
 945
 946                         alloclen += exthdrlen;
 947
 948                         /* The last fragment gets additional space at tail.
 949                          * Note, with MSG_MORE we overallocate on fragments,
 950                          * because we have no idea what fragment will be
 951                          * the last.
 952                          */
 953                         if (datalen == length + fraggap)
 954                                 alloclen += rt->dst.trailer_len;
 955
 956                         if (transhdrlen) {
 957                                 skb = sock_alloc_send_skb(sk,
 958                                                 alloclen + hh_len + 15,
 959                                                 (flags & MSG_DONTWAIT), &err);
 960                         } else {
 961                                 skb = NULL;
 962                                 if (atomic_read(&sk->sk_wmem_alloc) <=
 963                                     2 * sk->sk_sndbuf)
 964                                         skb = sock_wmalloc(sk,
 965                                                            alloclen + hh_len + 15, 1,
 966                                                            sk->sk_allocation);
 967                                 if (unlikely(skb == NULL))
 968                                         err = -ENOBUFS;
 969                         }
 970                         if (skb == NULL)
 971                                 goto error;
 972
 973                         /*
 974                          *      Fill in the control structures
 975                          */
 976                         skb->ip_summed = csummode;
 977                         skb->csum = 0;
 978                         skb_reserve(skb, hh_len);
 979
 980                         /* only the initial fragment is time stamped */
 981                         skb_shinfo(skb)->tx_flags = cork->tx_flags;
 982                         cork->tx_flags = 0;
 983                         skb_shinfo(skb)->tskey = tskey;
 984                         tskey = 0;
 985
 986                         /*
 987                          *      Find where to start putting bytes.
 988                          */
 989                         data = skb_put(skb, fraglen + exthdrlen);
 990                         skb_set_network_header(skb, exthdrlen);
 991                         skb->transport_header = (skb->network_header +
 992                                                  fragheaderlen);
 993                         data += fragheaderlen + exthdrlen;
 994
 995                         if (fraggap) {
 996                                 skb->csum = skb_copy_and_csum_bits(
 997                                         skb_prev, maxfraglen,
 998                                         data + transhdrlen, fraggap, 0);
 999                                 skb_prev->csum = csum_sub(skb_prev->csum,
1000                                                           skb->csum);
1001                                 data += fraggap;
1002                                 pskb_trim_unique(skb_prev, maxfraglen);
1003                         }
1004
1005                         copy = datalen - transhdrlen - fraggap;
1006                         if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
1007                                 err = -EFAULT;
1008                                 kfree_skb(skb);
1009                                 goto error;
1010                         }
1011
1012                         offset += copy;
1013                         length -= datalen - fraggap;
1014                         transhdrlen = 0;
1015                         exthdrlen = 0;
1016                         csummode = CHECKSUM_NONE;
1017
1018                         /*
1019                          * Put the packet on the pending queue.
1020                          */
1021                         __skb_queue_tail(queue, skb);
1022                         continue;
1023                 }
1024
1025                 if (copy > length)
1026                         copy = length;
1027
1028                 if (!(rt->dst.dev->features&NETIF_F_SG)) {
1029                         unsigned int off;
1030
1031                         off = skb->len;
1032                         if (getfrag(from, skb_put(skb, copy),
1033                                         offset, copy, off, skb) < 0) {
1034                                 __skb_trim(skb, off);
1035                                 err = -EFAULT;
1036                                 goto error;
1037                         }
1038                 } else {
1039                         int i = skb_shinfo(skb)->nr_frags;
1040
1041                         err = -ENOMEM;
1042                         if (!sk_page_frag_refill(sk, pfrag))
1043                                 goto error;
1044
1045                         if (!skb_can_coalesce(skb, i, pfrag->page,
1046                                               pfrag->offset)) {
1047                                 err = -EMSGSIZE;
1048                                 if (i == MAX_SKB_FRAGS)
1049                                         goto error;
1050
1051                                 __skb_fill_page_desc(skb, i, pfrag->page,
1052                                                      pfrag->offset, 0);
1053                                 skb_shinfo(skb)->nr_frags = ++i;
1054                                 get_page(pfrag->page);
1055                         }
1056                         copy = min_t(int, copy, pfrag->size - pfrag->offset);
1057                         if (getfrag(from,
1058                                     page_address(pfrag->page) + pfrag->offset,
1059                                     offset, copy, skb->len, skb) < 0)
1060                                 goto error_efault;
1061
1062                         pfrag->offset += copy;
1063                         skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
1064                         skb->len += copy;
1065                         skb->data_len += copy;
1066                         skb->truesize += copy;
1067                         atomic_add(copy, &sk->sk_wmem_alloc);
1068                 }
1069                 offset += copy;
1070                 length -= copy;
1071         }
1072
1073         return 0;
1074
1075 error_efault:
1076         err = -EFAULT;
1077 error:
1078         cork->length -= length;
1079         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1080         return err;
1081 }
1082
1083 static int ip_setup_cork(struct sock *sk, struct inet_cork *cork,
1084                          struct ipcm_cookie *ipc, struct rtable **rtp)
1085 {
1086         struct ip_options_rcu *opt;
1087         struct rtable *rt;
1088
1089         /*
1090          * setup for corking.
1091          */
1092         opt = ipc->opt;
1093         if (opt) {
1094                 if (cork->opt == NULL) {
1095                         cork->opt = kmalloc(sizeof(struct ip_options) + 40,
1096                                             sk->sk_allocation);
1097                         if (unlikely(cork->opt == NULL))
1098                                 return -ENOBUFS;
1099                 }
1100                 memcpy(cork->opt, &opt->opt, sizeof(struct ip_options) + opt->opt.optlen);
1101                 cork->flags |= IPCORK_OPT;
1102                 cork->addr = ipc->addr;
1103         }
1104         rt = *rtp;
1105         if (unlikely(!rt))
1106                 return -EFAULT;
1107         /*
1108          * We steal reference to this route, caller should not release it
1109          */
1110         *rtp = NULL;
1111         cork->fragsize = ip_sk_use_pmtu(sk) ?
1112                          dst_mtu(&rt->dst) : rt->dst.dev->mtu;
1113         cork->dst = &rt->dst;
1114         cork->length = 0;
1115         cork->ttl = ipc->ttl;
1116         cork->tos = ipc->tos;
1117         cork->priority = ipc->priority;
1118         cork->tx_flags = ipc->tx_flags;
1119
1120         return 0;
1121 }
1122
1123 /*
1124  *      ip_append_data() and ip_append_page() can make one large IP datagram
1125  *      from many pieces of data. Each pieces will be holded on the socket
1126  *      until ip_push_pending_frames() is called. Each piece can be a page
1127  *      or non-page data.
1128  *
1129  *      Not only UDP, other transport protocols - e.g. raw sockets - can use
1130  *      this interface potentially.
1131  *
1132  *      LATER: length must be adjusted by pad at tail, when it is required.
1133  */
1134 int ip_append_data(struct sock *sk, struct flowi4 *fl4,
1135                    int getfrag(void *from, char *to, int offset, int len,
1136                                int odd, struct sk_buff *skb),
1137                    void *from, int length, int transhdrlen,
1138                    struct ipcm_cookie *ipc, struct rtable **rtp,
1139                    unsigned int flags)
1140 {
1141         struct inet_sock *inet = inet_sk(sk);
1142         int err;
1143
1144         if (flags&MSG_PROBE)
1145                 return 0;
1146
1147         if (skb_queue_empty(&sk->sk_write_queue)) {
1148                 err = ip_setup_cork(sk, &inet->cork.base, ipc, rtp);
1149                 if (err)
1150                         return err;
1151         } else {
1152                 transhdrlen = 0;
1153         }
1154
1155         return __ip_append_data(sk, fl4, &sk->sk_write_queue, &inet->cork.base,
1156                                 sk_page_frag(sk), getfrag,
1157                                 from, length, transhdrlen, flags);
1158 }
1159
1160 ssize_t ip_append_page(struct sock *sk, struct flowi4 *fl4, struct page *page,
1161                        int offset, size_t size, int flags)
1162 {
1163         struct inet_sock *inet = inet_sk(sk);
1164         struct sk_buff *skb;
1165         struct rtable *rt;
1166         struct ip_options *opt = NULL;
1167         struct inet_cork *cork;
1168         int hh_len;
1169         int mtu;
1170         int len;
1171         int err;
1172         unsigned int maxfraglen, fragheaderlen, fraggap, maxnonfragsize;
1173
1174         if (inet->hdrincl)
1175                 return -EPERM;
1176
1177         if (flags&MSG_PROBE)
1178                 return 0;
1179
1180         if (skb_queue_empty(&sk->sk_write_queue))
1181                 return -EINVAL;
1182
1183         cork = &inet->cork.base;
1184         rt = (struct rtable *)cork->dst;
1185         if (cork->flags & IPCORK_OPT)
1186                 opt = cork->opt;
1187
1188         if (!(rt->dst.dev->features&NETIF_F_SG))
1189                 return -EOPNOTSUPP;
1190
1191         hh_len = LL_RESERVED_SPACE(rt->dst.dev);
1192         mtu = cork->fragsize;
1193
1194         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
1195         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
1196         maxnonfragsize = ip_sk_ignore_df(sk) ? 0xFFFF : mtu;
1197
1198         if (cork->length + size > maxnonfragsize - fragheaderlen) {
1199                 ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
1200                                mtu - (opt ? opt->optlen : 0));
1201                 return -EMSGSIZE;
1202         }
1203
1204         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
1205                 return -EINVAL;
1206
1207         cork->length += size;
1208         if ((size + skb->len > mtu) &&
1209             (sk->sk_protocol == IPPROTO_UDP) &&
1210             (rt->dst.dev->features & NETIF_F_UFO)) {
1211                 skb_shinfo(skb)->gso_size = mtu - fragheaderlen;
1212                 skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
1213         }
1214
1215
1216         while (size > 0) {
1217                 int i;
1218
1219                 if (skb_is_gso(skb))
1220                         len = size;
1221                 else {
1222
1223                         /* Check if the remaining data fits into current packet. */
1224                         len = mtu - skb->len;
1225                         if (len < size)
1226                                 len = maxfraglen - skb->len;
1227                 }
1228                 if (len <= 0) {
1229                         struct sk_buff *skb_prev;
1230                         int alloclen;
1231
1232                         skb_prev = skb;
1233                         fraggap = skb_prev->len - maxfraglen;
1234
1235                         alloclen = fragheaderlen + hh_len + fraggap + 15;
1236                         skb = sock_wmalloc(sk, alloclen, 1, sk->sk_allocation);
1237                         if (unlikely(!skb)) {
1238                                 err = -ENOBUFS;
1239                                 goto error;
1240                         }
1241
1242                         /*
1243                          *      Fill in the control structures
1244                          */
1245                         skb->ip_summed = CHECKSUM_NONE;
1246                         skb->csum = 0;
1247                         skb_reserve(skb, hh_len);
1248
1249                         /*
1250                          *      Find where to start putting bytes.
1251                          */
1252                         skb_put(skb, fragheaderlen + fraggap);
1253                         skb_reset_network_header(skb);
1254                         skb->transport_header = (skb->network_header +
1255                                                  fragheaderlen);
1256                         if (fraggap) {
1257                                 skb->csum = skb_copy_and_csum_bits(skb_prev,
1258                                                                    maxfraglen,
1259                                                     skb_transport_header(skb),
1260                                                                    fraggap, 0);
1261                                 skb_prev->csum = csum_sub(skb_prev->csum,
1262                                                           skb->csum);
1263                                 pskb_trim_unique(skb_prev, maxfraglen);
1264                         }
1265
1266                         /*
1267                          * Put the packet on the pending queue.
1268                          */
1269                         __skb_queue_tail(&sk->sk_write_queue, skb);
1270                         continue;
1271                 }
1272
1273                 i = skb_shinfo(skb)->nr_frags;
1274                 if (len > size)
1275                         len = size;
1276                 if (skb_can_coalesce(skb, i, page, offset)) {
1277                         skb_frag_size_add(&skb_shinfo(skb)->frags[i-1], len);
1278                 } else if (i < MAX_SKB_FRAGS) {
1279                         get_page(page);
1280                         skb_fill_page_desc(skb, i, page, offset, len);
1281                 } else {
1282                         err = -EMSGSIZE;
1283                         goto error;
1284                 }
1285
1286                 if (skb->ip_summed == CHECKSUM_NONE) {
1287                         __wsum csum;
1288                         csum = csum_page(page, offset, len);
1289                         skb->csum = csum_block_add(skb->csum, csum, skb->len);
1290                 }
1291
1292                 skb->len += len;
1293                 skb->data_len += len;
1294                 skb->truesize += len;
1295                 atomic_add(len, &sk->sk_wmem_alloc);
1296                 offset += len;
1297                 size -= len;
1298         }
1299         return 0;
1300
1301 error:
1302         cork->length -= size;
1303         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1304         return err;
1305 }
1306
1307 static void ip_cork_release(struct inet_cork *cork)
1308 {
1309         cork->flags &= ~IPCORK_OPT;
1310         kfree(cork->opt);
1311         cork->opt = NULL;
1312         dst_release(cork->dst);
1313         cork->dst = NULL;
1314 }
1315
1316 /*
1317  *      Combined all pending IP fragments on the socket as one IP datagram
1318  *      and push them out.
1319  */
1320 struct sk_buff *__ip_make_skb(struct sock *sk,
1321                               struct flowi4 *fl4,
1322                               struct sk_buff_head *queue,
1323                               struct inet_cork *cork)
1324 {
1325         struct sk_buff *skb, *tmp_skb;
1326         struct sk_buff **tail_skb;
1327         struct inet_sock *inet = inet_sk(sk);
1328         struct net *net = sock_net(sk);
1329         struct ip_options *opt = NULL;
1330         struct rtable *rt = (struct rtable *)cork->dst;
1331         struct iphdr *iph;
1332         __be16 df = 0;
1333         __u8 ttl;
1334
1335         if ((skb = __skb_dequeue(queue)) == NULL)
1336                 goto out;
1337         tail_skb = &(skb_shinfo(skb)->frag_list);
1338
1339         /* move skb->data to ip header from ext header */
1340         if (skb->data < skb_network_header(skb))
1341                 __skb_pull(skb, skb_network_offset(skb));
1342         while ((tmp_skb = __skb_dequeue(queue)) != NULL) {
1343                 __skb_pull(tmp_skb, skb_network_header_len(skb));
1344                 *tail_skb = tmp_skb;
1345                 tail_skb = &(tmp_skb->next);
1346                 skb->len += tmp_skb->len;
1347                 skb->data_len += tmp_skb->len;
1348                 skb->truesize += tmp_skb->truesize;
1349                 tmp_skb->destructor = NULL;
1350                 tmp_skb->sk = NULL;
1351         }
1352
1353         /* Unless user demanded real pmtu discovery (IP_PMTUDISC_DO), we allow
1354          * to fragment the frame generated here. No matter, what transforms
1355          * how transforms change size of the packet, it will come out.
1356          */
1357         skb->ignore_df = ip_sk_ignore_df(sk);
1358
1359         /* DF bit is set when we want to see DF on outgoing frames.
1360          * If ignore_df is set too, we still allow to fragment this frame
1361          * locally. */
1362         if (inet->pmtudisc == IP_PMTUDISC_DO ||
1363             inet->pmtudisc == IP_PMTUDISC_PROBE ||
1364             (skb->len <= dst_mtu(&rt->dst) &&
1365              ip_dont_fragment(sk, &rt->dst)))
1366                 df = htons(IP_DF);
1367
1368         if (cork->flags & IPCORK_OPT)
1369                 opt = cork->opt;
1370
1371         if (cork->ttl != 0)
1372                 ttl = cork->ttl;
1373         else if (rt->rt_type == RTN_MULTICAST)
1374                 ttl = inet->mc_ttl;
1375         else
1376                 ttl = ip_select_ttl(inet, &rt->dst);
1377
1378         iph = ip_hdr(skb);
1379         iph->version = 4;
1380         iph->ihl = 5;
1381         iph->tos = (cork->tos != -1) ? cork->tos : inet->tos;
1382         iph->frag_off = df;
1383         iph->ttl = ttl;
1384         iph->protocol = sk->sk_protocol;
1385         ip_copy_addrs(iph, fl4);
1386         ip_select_ident(skb, sk);
1387
1388         if (opt) {
1389                 iph->ihl += opt->optlen>>2;
1390                 ip_options_build(skb, opt, cork->addr, rt, 0);
1391         }
1392
1393         skb->priority = (cork->tos != -1) ? cork->priority: sk->sk_priority;
1394         skb->mark = sk->sk_mark;
1395         /*
1396          * Steal rt from cork.dst to avoid a pair of atomic_inc/atomic_dec
1397          * on dst refcount
1398          */
1399         cork->dst = NULL;
1400         skb_dst_set(skb, &rt->dst);
1401
1402         if (iph->protocol == IPPROTO_ICMP)
1403                 icmp_out_count(net, ((struct icmphdr *)
1404                         skb_transport_header(skb))->type);
1405
1406         ip_cork_release(cork);
1407 out:
1408         return skb;
1409 }
1410
1411 int ip_send_skb(struct net *net, struct sk_buff *skb)
1412 {
1413         int err;
1414
1415         err = ip_local_out(skb);
1416         if (err) {
1417                 if (err > 0)
1418                         err = net_xmit_errno(err);
1419                 if (err)
1420                         IP_INC_STATS(net, IPSTATS_MIB_OUTDISCARDS);
1421         }
1422
1423         return err;
1424 }
1425
1426 int ip_push_pending_frames(struct sock *sk, struct flowi4 *fl4)
1427 {
1428         struct sk_buff *skb;
1429
1430         skb = ip_finish_skb(sk, fl4);
1431         if (!skb)
1432                 return 0;
1433
1434         /* Netfilter gets whole the not fragmented skb. */
1435         return ip_send_skb(sock_net(sk), skb);
1436 }
1437
1438 /*
1439  *      Throw away all pending data on the socket.
1440  */
1441 static void __ip_flush_pending_frames(struct sock *sk,
1442                                       struct sk_buff_head *queue,
1443                                       struct inet_cork *cork)
1444 {
1445         struct sk_buff *skb;
1446
1447         while ((skb = __skb_dequeue_tail(queue)) != NULL)
1448                 kfree_skb(skb);
1449
1450         ip_cork_release(cork);
1451 }
1452
1453 void ip_flush_pending_frames(struct sock *sk)
1454 {
1455         __ip_flush_pending_frames(sk, &sk->sk_write_queue, &inet_sk(sk)->cork.base);
1456 }
1457
1458 struct sk_buff *ip_make_skb(struct sock *sk,
1459                             struct flowi4 *fl4,
1460                             int getfrag(void *from, char *to, int offset,
1461                                         int len, int odd, struct sk_buff *skb),
1462                             void *from, int length, int transhdrlen,
1463                             struct ipcm_cookie *ipc, struct rtable **rtp,
1464                             unsigned int flags)
1465 {
1466         struct inet_cork cork;
1467         struct sk_buff_head queue;
1468         int err;
1469
1470         if (flags & MSG_PROBE)
1471                 return NULL;
1472
1473         __skb_queue_head_init(&queue);
1474
1475         cork.flags = 0;
1476         cork.addr = 0;
1477         cork.opt = NULL;
1478         err = ip_setup_cork(sk, &cork, ipc, rtp);
1479         if (err)
1480                 return ERR_PTR(err);
1481
1482         err = __ip_append_data(sk, fl4, &queue, &cork,
1483                                &current->task_frag, getfrag,
1484                                from, length, transhdrlen, flags);
1485         if (err) {
1486                 __ip_flush_pending_frames(sk, &queue, &cork);
1487                 return ERR_PTR(err);
1488         }
1489
1490         return __ip_make_skb(sk, fl4, &queue, &cork);
1491 }
1492
1493 /*
1494  *      Fetch data from kernel space and fill in checksum if needed.
1495  */
1496 static int ip_reply_glue_bits(void *dptr, char *to, int offset,
1497                               int len, int odd, struct sk_buff *skb)
1498 {
1499         __wsum csum;
1500
1501         csum = csum_partial_copy_nocheck(dptr+offset, to, len, 0);
1502         skb->csum = csum_block_add(skb->csum, csum, odd);
1503         return 0;
1504 }
1505
1506 /*
1507  *      Generic function to send a packet as reply to another packet.
1508  *      Used to send some TCP resets/acks so far.
1509  */
1510 void ip_send_unicast_reply(struct sock *sk, struct sk_buff *skb,
1511                            const struct ip_options *sopt,
1512                            __be32 daddr, __be32 saddr,
1513                            const struct ip_reply_arg *arg,
1514                            unsigned int len)
1515 {
1516         struct ip_options_data replyopts;
1517         struct ipcm_cookie ipc;
1518         struct flowi4 fl4;
1519         struct rtable *rt = skb_rtable(skb);
1520         struct net *net = sock_net(sk);
1521         struct sk_buff *nskb;
1522         int err;
1523
1524         if (__ip_options_echo(&replyopts.opt.opt, skb, sopt))
1525                 return;
1526
1527         ipc.addr = daddr;
1528         ipc.opt = NULL;
1529         ipc.tx_flags = 0;
1530         ipc.ttl = 0;
1531         ipc.tos = -1;
1532
1533         if (replyopts.opt.opt.optlen) {
1534                 ipc.opt = &replyopts.opt;
1535
1536                 if (replyopts.opt.opt.srr)
1537                         daddr = replyopts.opt.opt.faddr;
1538         }
1539
1540         flowi4_init_output(&fl4, arg->bound_dev_if,
1541                            IP4_REPLY_MARK(net, skb->mark),
1542                            RT_TOS(arg->tos),
1543                            RT_SCOPE_UNIVERSE, ip_hdr(skb)->protocol,
1544                            ip_reply_arg_flowi_flags(arg),
1545                            daddr, saddr,
1546                            tcp_hdr(skb)->source, tcp_hdr(skb)->dest);
1547         security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
1548         rt = ip_route_output_key(net, &fl4);
1549         if (IS_ERR(rt))
1550                 return;
1551
1552         inet_sk(sk)->tos = arg->tos;
1553
1554         sk->sk_priority = skb->priority;
1555         sk->sk_protocol = ip_hdr(skb)->protocol;
1556         sk->sk_bound_dev_if = arg->bound_dev_if;
1557         sk->sk_sndbuf = sysctl_wmem_default;
1558         err = ip_append_data(sk, &fl4, ip_reply_glue_bits, arg->iov->iov_base,
1559                              len, 0, &ipc, &rt, MSG_DONTWAIT);
1560         if (unlikely(err)) {
1561                 ip_flush_pending_frames(sk);
1562                 goto out;
1563         }
1564
1565         nskb = skb_peek(&sk->sk_write_queue);
1566         if (nskb) {
1567                 if (arg->csumoffset >= 0)
1568                         *((__sum16 *)skb_transport_header(nskb) +
1569                           arg->csumoffset) = csum_fold(csum_add(nskb->csum,
1570                                                                 arg->csum));
1571                 nskb->ip_summed = CHECKSUM_NONE;
1572                 skb_set_queue_mapping(nskb, skb_get_queue_mapping(skb));
1573                 ip_push_pending_frames(sk, &fl4);
1574         }
1575 out:
1576         ip_rt_put(rt);
1577 }
1578
1579 void __init ip_init(void)
1580 {
1581         ip_rt_init();
1582         inet_initpeers();
1583
1584 #if defined(CONFIG_IP_MULTICAST)
1585         igmp_mc_init();
1586 #endif
1587 }