linux/net/ipv4/ip_output.c
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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 <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
  83int sysctl_ip_default_ttl __read_mostly = IPDEFTTL;
  84EXPORT_SYMBOL(sysctl_ip_default_ttl);
  85
  86/* Generate a checksum for an outgoing IP datagram. */
  87__inline__ void ip_send_check(struct iphdr *iph)
  88{
  89        iph->check = 0;
  90        iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
  91}
  92EXPORT_SYMBOL(ip_send_check);
  93
  94int __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
 104int ip_local_out(struct sk_buff *skb)
 105{
 106        int err;
 107
 108        err = __ip_local_out(skb);
 109        if (likely(err == 1))
 110                err = dst_output(skb);
 111
 112        return err;
 113}
 114EXPORT_SYMBOL_GPL(ip_local_out);
 115
 116static 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 */
 129int 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(iph, &rt->dst, 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}
 164EXPORT_SYMBOL_GPL(ip_build_and_send_pkt);
 165
 166static 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
 214static inline int ip_skb_dst_mtu(struct sk_buff *skb)
 215{
 216        struct inet_sock *inet = skb->sk ? inet_sk(skb->sk) : NULL;
 217
 218        return (inet && inet->pmtudisc == IP_PMTUDISC_PROBE) ?
 219               skb_dst(skb)->dev->mtu : dst_mtu(skb_dst(skb));
 220}
 221
 222static int ip_finish_output(struct sk_buff *skb)
 223{
 224#if defined(CONFIG_NETFILTER) && defined(CONFIG_XFRM)
 225        /* Policy lookup after SNAT yielded a new policy */
 226        if (skb_dst(skb)->xfrm != NULL) {
 227                IPCB(skb)->flags |= IPSKB_REROUTED;
 228                return dst_output(skb);
 229        }
 230#endif
 231        if (skb->len > ip_skb_dst_mtu(skb) && !skb_is_gso(skb))
 232                return ip_fragment(skb, ip_finish_output2);
 233        else
 234                return ip_finish_output2(skb);
 235}
 236
 237int ip_mc_output(struct sk_buff *skb)
 238{
 239        struct sock *sk = skb->sk;
 240        struct rtable *rt = skb_rtable(skb);
 241        struct net_device *dev = rt->dst.dev;
 242
 243        /*
 244         *      If the indicated interface is up and running, send the packet.
 245         */
 246        IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUT, skb->len);
 247
 248        skb->dev = dev;
 249        skb->protocol = htons(ETH_P_IP);
 250
 251        /*
 252         *      Multicasts are looped back for other local users
 253         */
 254
 255        if (rt->rt_flags&RTCF_MULTICAST) {
 256                if (sk_mc_loop(sk)
 257#ifdef CONFIG_IP_MROUTE
 258                /* Small optimization: do not loopback not local frames,
 259                   which returned after forwarding; they will be  dropped
 260                   by ip_mr_input in any case.
 261                   Note, that local frames are looped back to be delivered
 262                   to local recipients.
 263
 264                   This check is duplicated in ip_mr_input at the moment.
 265                 */
 266                    &&
 267                    ((rt->rt_flags & RTCF_LOCAL) ||
 268                     !(IPCB(skb)->flags & IPSKB_FORWARDED))
 269#endif
 270                   ) {
 271                        struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
 272                        if (newskb)
 273                                NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING,
 274                                        newskb, NULL, newskb->dev,
 275                                        dev_loopback_xmit);
 276                }
 277
 278                /* Multicasts with ttl 0 must not go beyond the host */
 279
 280                if (ip_hdr(skb)->ttl == 0) {
 281                        kfree_skb(skb);
 282                        return 0;
 283                }
 284        }
 285
 286        if (rt->rt_flags&RTCF_BROADCAST) {
 287                struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
 288                if (newskb)
 289                        NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING, newskb,
 290                                NULL, newskb->dev, dev_loopback_xmit);
 291        }
 292
 293        return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING, skb, NULL,
 294                            skb->dev, ip_finish_output,
 295                            !(IPCB(skb)->flags & IPSKB_REROUTED));
 296}
 297
 298int ip_output(struct sk_buff *skb)
 299{
 300        struct net_device *dev = skb_dst(skb)->dev;
 301
 302        IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUT, skb->len);
 303
 304        skb->dev = dev;
 305        skb->protocol = htons(ETH_P_IP);
 306
 307        return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING, skb, NULL, dev,
 308                            ip_finish_output,
 309                            !(IPCB(skb)->flags & IPSKB_REROUTED));
 310}
 311
 312/*
 313 * copy saddr and daddr, possibly using 64bit load/stores
 314 * Equivalent to :
 315 *   iph->saddr = fl4->saddr;
 316 *   iph->daddr = fl4->daddr;
 317 */
 318static void ip_copy_addrs(struct iphdr *iph, const struct flowi4 *fl4)
 319{
 320        BUILD_BUG_ON(offsetof(typeof(*fl4), daddr) !=
 321                     offsetof(typeof(*fl4), saddr) + sizeof(fl4->saddr));
 322        memcpy(&iph->saddr, &fl4->saddr,
 323               sizeof(fl4->saddr) + sizeof(fl4->daddr));
 324}
 325
 326int ip_queue_xmit(struct sk_buff *skb, struct flowi *fl)
 327{
 328        struct sock *sk = skb->sk;
 329        struct inet_sock *inet = inet_sk(sk);
 330        struct ip_options_rcu *inet_opt;
 331        struct flowi4 *fl4;
 332        struct rtable *rt;
 333        struct iphdr *iph;
 334        int res;
 335
 336        /* Skip all of this if the packet is already routed,
 337         * f.e. by something like SCTP.
 338         */
 339        rcu_read_lock();
 340        inet_opt = rcu_dereference(inet->inet_opt);
 341        fl4 = &fl->u.ip4;
 342        rt = skb_rtable(skb);
 343        if (rt != NULL)
 344                goto packet_routed;
 345
 346        /* Make sure we can route this packet. */
 347        rt = (struct rtable *)__sk_dst_check(sk, 0);
 348        if (rt == NULL) {
 349                __be32 daddr;
 350
 351                /* Use correct destination address if we have options. */
 352                daddr = inet->inet_daddr;
 353                if (inet_opt && inet_opt->opt.srr)
 354                        daddr = inet_opt->opt.faddr;
 355
 356                /* If this fails, retransmit mechanism of transport layer will
 357                 * keep trying until route appears or the connection times
 358                 * itself out.
 359                 */
 360                rt = ip_route_output_ports(sock_net(sk), fl4, sk,
 361                                           daddr, inet->inet_saddr,
 362                                           inet->inet_dport,
 363                                           inet->inet_sport,
 364                                           sk->sk_protocol,
 365                                           RT_CONN_FLAGS(sk),
 366                                           sk->sk_bound_dev_if);
 367                if (IS_ERR(rt))
 368                        goto no_route;
 369                sk_setup_caps(sk, &rt->dst);
 370        }
 371        skb_dst_set_noref(skb, &rt->dst);
 372
 373packet_routed:
 374        if (inet_opt && inet_opt->opt.is_strictroute && rt->rt_uses_gateway)
 375                goto no_route;
 376
 377        /* OK, we know where to send it, allocate and build IP header. */
 378        skb_push(skb, sizeof(struct iphdr) + (inet_opt ? inet_opt->opt.optlen : 0));
 379        skb_reset_network_header(skb);
 380        iph = ip_hdr(skb);
 381        *((__be16 *)iph) = htons((4 << 12) | (5 << 8) | (inet->tos & 0xff));
 382        if (ip_dont_fragment(sk, &rt->dst) && !skb->local_df)
 383                iph->frag_off = htons(IP_DF);
 384        else
 385                iph->frag_off = 0;
 386        iph->ttl      = ip_select_ttl(inet, &rt->dst);
 387        iph->protocol = sk->sk_protocol;
 388        ip_copy_addrs(iph, fl4);
 389
 390        /* Transport layer set skb->h.foo itself. */
 391
 392        if (inet_opt && inet_opt->opt.optlen) {
 393                iph->ihl += inet_opt->opt.optlen >> 2;
 394                ip_options_build(skb, &inet_opt->opt, inet->inet_daddr, rt, 0);
 395        }
 396
 397        ip_select_ident_more(iph, &rt->dst, sk,
 398                             (skb_shinfo(skb)->gso_segs ?: 1) - 1);
 399
 400        skb->priority = sk->sk_priority;
 401        skb->mark = sk->sk_mark;
 402
 403        res = ip_local_out(skb);
 404        rcu_read_unlock();
 405        return res;
 406
 407no_route:
 408        rcu_read_unlock();
 409        IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);
 410        kfree_skb(skb);
 411        return -EHOSTUNREACH;
 412}
 413EXPORT_SYMBOL(ip_queue_xmit);
 414
 415
 416static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
 417{
 418        to->pkt_type = from->pkt_type;
 419        to->priority = from->priority;
 420        to->protocol = from->protocol;
 421        skb_dst_drop(to);
 422        skb_dst_copy(to, from);
 423        to->dev = from->dev;
 424        to->mark = from->mark;
 425
 426        /* Copy the flags to each fragment. */
 427        IPCB(to)->flags = IPCB(from)->flags;
 428
 429#ifdef CONFIG_NET_SCHED
 430        to->tc_index = from->tc_index;
 431#endif
 432        nf_copy(to, from);
 433#if defined(CONFIG_NETFILTER_XT_TARGET_TRACE) || \
 434    defined(CONFIG_NETFILTER_XT_TARGET_TRACE_MODULE)
 435        to->nf_trace = from->nf_trace;
 436#endif
 437#if defined(CONFIG_IP_VS) || defined(CONFIG_IP_VS_MODULE)
 438        to->ipvs_property = from->ipvs_property;
 439#endif
 440        skb_copy_secmark(to, from);
 441}
 442
 443/*
 444 *      This IP datagram is too large to be sent in one piece.  Break it up into
 445 *      smaller pieces (each of size equal to IP header plus
 446 *      a block of the data of the original IP data part) that will yet fit in a
 447 *      single device frame, and queue such a frame for sending.
 448 */
 449
 450int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
 451{
 452        struct iphdr *iph;
 453        int ptr;
 454        struct net_device *dev;
 455        struct sk_buff *skb2;
 456        unsigned int mtu, hlen, left, len, ll_rs;
 457        int offset;
 458        __be16 not_last_frag;
 459        struct rtable *rt = skb_rtable(skb);
 460        int err = 0;
 461
 462        dev = rt->dst.dev;
 463
 464        /*
 465         *      Point into the IP datagram header.
 466         */
 467
 468        iph = ip_hdr(skb);
 469
 470        if (unlikely((iph->frag_off & htons(IP_DF)) && !skb->local_df)) {
 471                IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
 472                icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
 473                          htonl(ip_skb_dst_mtu(skb)));
 474                kfree_skb(skb);
 475                return -EMSGSIZE;
 476        }
 477
 478        /*
 479         *      Setup starting values.
 480         */
 481
 482        hlen = iph->ihl * 4;
 483        mtu = dst_mtu(&rt->dst) - hlen; /* Size of data space */
 484#ifdef CONFIG_BRIDGE_NETFILTER
 485        if (skb->nf_bridge)
 486                mtu -= nf_bridge_mtu_reduction(skb);
 487#endif
 488        IPCB(skb)->flags |= IPSKB_FRAG_COMPLETE;
 489
 490        /* When frag_list is given, use it. First, check its validity:
 491         * some transformers could create wrong frag_list or break existing
 492         * one, it is not prohibited. In this case fall back to copying.
 493         *
 494         * LATER: this step can be merged to real generation of fragments,
 495         * we can switch to copy when see the first bad fragment.
 496         */
 497        if (skb_has_frag_list(skb)) {
 498                struct sk_buff *frag, *frag2;
 499                int first_len = skb_pagelen(skb);
 500
 501                if (first_len - hlen > mtu ||
 502                    ((first_len - hlen) & 7) ||
 503                    ip_is_fragment(iph) ||
 504                    skb_cloned(skb))
 505                        goto slow_path;
 506
 507                skb_walk_frags(skb, frag) {
 508                        /* Correct geometry. */
 509                        if (frag->len > mtu ||
 510                            ((frag->len & 7) && frag->next) ||
 511                            skb_headroom(frag) < hlen)
 512                                goto slow_path_clean;
 513
 514                        /* Partially cloned skb? */
 515                        if (skb_shared(frag))
 516                                goto slow_path_clean;
 517
 518                        BUG_ON(frag->sk);
 519                        if (skb->sk) {
 520                                frag->sk = skb->sk;
 521                                frag->destructor = sock_wfree;
 522                        }
 523                        skb->truesize -= frag->truesize;
 524                }
 525
 526                /* Everything is OK. Generate! */
 527
 528                err = 0;
 529                offset = 0;
 530                frag = skb_shinfo(skb)->frag_list;
 531                skb_frag_list_init(skb);
 532                skb->data_len = first_len - skb_headlen(skb);
 533                skb->len = first_len;
 534                iph->tot_len = htons(first_len);
 535                iph->frag_off = htons(IP_MF);
 536                ip_send_check(iph);
 537
 538                for (;;) {
 539                        /* Prepare header of the next frame,
 540                         * before previous one went down. */
 541                        if (frag) {
 542                                frag->ip_summed = CHECKSUM_NONE;
 543                                skb_reset_transport_header(frag);
 544                                __skb_push(frag, hlen);
 545                                skb_reset_network_header(frag);
 546                                memcpy(skb_network_header(frag), iph, hlen);
 547                                iph = ip_hdr(frag);
 548                                iph->tot_len = htons(frag->len);
 549                                ip_copy_metadata(frag, skb);
 550                                if (offset == 0)
 551                                        ip_options_fragment(frag);
 552                                offset += skb->len - hlen;
 553                                iph->frag_off = htons(offset>>3);
 554                                if (frag->next != NULL)
 555                                        iph->frag_off |= htons(IP_MF);
 556                                /* Ready, complete checksum */
 557                                ip_send_check(iph);
 558                        }
 559
 560                        err = output(skb);
 561
 562                        if (!err)
 563                                IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGCREATES);
 564                        if (err || !frag)
 565                                break;
 566
 567                        skb = frag;
 568                        frag = skb->next;
 569                        skb->next = NULL;
 570                }
 571
 572                if (err == 0) {
 573                        IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGOKS);
 574                        return 0;
 575                }
 576
 577                while (frag) {
 578                        skb = frag->next;
 579                        kfree_skb(frag);
 580                        frag = skb;
 581                }
 582                IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
 583                return err;
 584
 585slow_path_clean:
 586                skb_walk_frags(skb, frag2) {
 587                        if (frag2 == frag)
 588                                break;
 589                        frag2->sk = NULL;
 590                        frag2->destructor = NULL;
 591                        skb->truesize += frag2->truesize;
 592                }
 593        }
 594
 595slow_path:
 596        left = skb->len - hlen;         /* Space per frame */
 597        ptr = hlen;             /* Where to start from */
 598
 599        /* for bridged IP traffic encapsulated inside f.e. a vlan header,
 600         * we need to make room for the encapsulating header
 601         */
 602        ll_rs = LL_RESERVED_SPACE_EXTRA(rt->dst.dev, nf_bridge_pad(skb));
 603
 604        /*
 605         *      Fragment the datagram.
 606         */
 607
 608        offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3;
 609        not_last_frag = iph->frag_off & htons(IP_MF);
 610
 611        /*
 612         *      Keep copying data until we run out.
 613         */
 614
 615        while (left > 0) {
 616                len = left;
 617                /* IF: it doesn't fit, use 'mtu' - the data space left */
 618                if (len > mtu)
 619                        len = mtu;
 620                /* IF: we are not sending up to and including the packet end
 621                   then align the next start on an eight byte boundary */
 622                if (len < left) {
 623                        len &= ~7;
 624                }
 625                /*
 626                 *      Allocate buffer.
 627                 */
 628
 629                if ((skb2 = alloc_skb(len+hlen+ll_rs, GFP_ATOMIC)) == NULL) {
 630                        NETDEBUG(KERN_INFO "IP: frag: no memory for new fragment!\n");
 631                        err = -ENOMEM;
 632                        goto fail;
 633                }
 634
 635                /*
 636                 *      Set up data on packet
 637                 */
 638
 639                ip_copy_metadata(skb2, skb);
 640                skb_reserve(skb2, ll_rs);
 641                skb_put(skb2, len + hlen);
 642                skb_reset_network_header(skb2);
 643                skb2->transport_header = skb2->network_header + hlen;
 644
 645                /*
 646                 *      Charge the memory for the fragment to any owner
 647                 *      it might possess
 648                 */
 649
 650                if (skb->sk)
 651                        skb_set_owner_w(skb2, skb->sk);
 652
 653                /*
 654                 *      Copy the packet header into the new buffer.
 655                 */
 656
 657                skb_copy_from_linear_data(skb, skb_network_header(skb2), hlen);
 658
 659                /*
 660                 *      Copy a block of the IP datagram.
 661                 */
 662                if (skb_copy_bits(skb, ptr, skb_transport_header(skb2), len))
 663                        BUG();
 664                left -= len;
 665
 666                /*
 667                 *      Fill in the new header fields.
 668                 */
 669                iph = ip_hdr(skb2);
 670                iph->frag_off = htons((offset >> 3));
 671
 672                /* ANK: dirty, but effective trick. Upgrade options only if
 673                 * the segment to be fragmented was THE FIRST (otherwise,
 674                 * options are already fixed) and make it ONCE
 675                 * on the initial skb, so that all the following fragments
 676                 * will inherit fixed options.
 677                 */
 678                if (offset == 0)
 679                        ip_options_fragment(skb);
 680
 681                /*
 682                 *      Added AC : If we are fragmenting a fragment that's not the
 683                 *                 last fragment then keep MF on each bit
 684                 */
 685                if (left > 0 || not_last_frag)
 686                        iph->frag_off |= htons(IP_MF);
 687                ptr += len;
 688                offset += len;
 689
 690                /*
 691                 *      Put this fragment into the sending queue.
 692                 */
 693                iph->tot_len = htons(len + hlen);
 694
 695                ip_send_check(iph);
 696
 697                err = output(skb2);
 698                if (err)
 699                        goto fail;
 700
 701                IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGCREATES);
 702        }
 703        consume_skb(skb);
 704        IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGOKS);
 705        return err;
 706
 707fail:
 708        kfree_skb(skb);
 709        IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
 710        return err;
 711}
 712EXPORT_SYMBOL(ip_fragment);
 713
 714int
 715ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
 716{
 717        struct iovec *iov = from;
 718
 719        if (skb->ip_summed == CHECKSUM_PARTIAL) {
 720                if (memcpy_fromiovecend(to, iov, offset, len) < 0)
 721                        return -EFAULT;
 722        } else {
 723                __wsum csum = 0;
 724                if (csum_partial_copy_fromiovecend(to, iov, offset, len, &csum) < 0)
 725                        return -EFAULT;
 726                skb->csum = csum_block_add(skb->csum, csum, odd);
 727        }
 728        return 0;
 729}
 730EXPORT_SYMBOL(ip_generic_getfrag);
 731
 732static inline __wsum
 733csum_page(struct page *page, int offset, int copy)
 734{
 735        char *kaddr;
 736        __wsum csum;
 737        kaddr = kmap(page);
 738        csum = csum_partial(kaddr + offset, copy, 0);
 739        kunmap(page);
 740        return csum;
 741}
 742
 743static inline int ip_ufo_append_data(struct sock *sk,
 744                        struct sk_buff_head *queue,
 745                        int getfrag(void *from, char *to, int offset, int len,
 746                               int odd, struct sk_buff *skb),
 747                        void *from, int length, int hh_len, int fragheaderlen,
 748                        int transhdrlen, int maxfraglen, unsigned int flags)
 749{
 750        struct sk_buff *skb;
 751        int err;
 752
 753        /* There is support for UDP fragmentation offload by network
 754         * device, so create one single skb packet containing complete
 755         * udp datagram
 756         */
 757        if ((skb = skb_peek_tail(queue)) == NULL) {
 758                skb = sock_alloc_send_skb(sk,
 759                        hh_len + fragheaderlen + transhdrlen + 20,
 760                        (flags & MSG_DONTWAIT), &err);
 761
 762                if (skb == NULL)
 763                        return err;
 764
 765                /* reserve space for Hardware header */
 766                skb_reserve(skb, hh_len);
 767
 768                /* create space for UDP/IP header */
 769                skb_put(skb, fragheaderlen + transhdrlen);
 770
 771                /* initialize network header pointer */
 772                skb_reset_network_header(skb);
 773
 774                /* initialize protocol header pointer */
 775                skb->transport_header = skb->network_header + fragheaderlen;
 776
 777                skb->ip_summed = CHECKSUM_PARTIAL;
 778                skb->csum = 0;
 779
 780                /* specify the length of each IP datagram fragment */
 781                skb_shinfo(skb)->gso_size = maxfraglen - fragheaderlen;
 782                skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
 783                __skb_queue_tail(queue, skb);
 784        }
 785
 786        return skb_append_datato_frags(sk, skb, getfrag, from,
 787                                       (length - transhdrlen));
 788}
 789
 790static int __ip_append_data(struct sock *sk,
 791                            struct flowi4 *fl4,
 792                            struct sk_buff_head *queue,
 793                            struct inet_cork *cork,
 794                            int getfrag(void *from, char *to, int offset,
 795                                        int len, int odd, struct sk_buff *skb),
 796                            void *from, int length, int transhdrlen,
 797                            unsigned int flags)
 798{
 799        struct inet_sock *inet = inet_sk(sk);
 800        struct sk_buff *skb;
 801
 802        struct ip_options *opt = cork->opt;
 803        int hh_len;
 804        int exthdrlen;
 805        int mtu;
 806        int copy;
 807        int err;
 808        int offset = 0;
 809        unsigned int maxfraglen, fragheaderlen;
 810        int csummode = CHECKSUM_NONE;
 811        struct rtable *rt = (struct rtable *)cork->dst;
 812
 813        skb = skb_peek_tail(queue);
 814
 815        exthdrlen = !skb ? rt->dst.header_len : 0;
 816        mtu = cork->fragsize;
 817
 818        hh_len = LL_RESERVED_SPACE(rt->dst.dev);
 819
 820        fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
 821        maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
 822
 823        if (cork->length + length > 0xFFFF - fragheaderlen) {
 824                ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
 825                               mtu-exthdrlen);
 826                return -EMSGSIZE;
 827        }
 828
 829        /*
 830         * transhdrlen > 0 means that this is the first fragment and we wish
 831         * it won't be fragmented in the future.
 832         */
 833        if (transhdrlen &&
 834            length + fragheaderlen <= mtu &&
 835            rt->dst.dev->features & NETIF_F_V4_CSUM &&
 836            !exthdrlen)
 837                csummode = CHECKSUM_PARTIAL;
 838
 839        cork->length += length;
 840        if (((length > mtu) || (skb && skb_is_gso(skb))) &&
 841            (sk->sk_protocol == IPPROTO_UDP) &&
 842            (rt->dst.dev->features & NETIF_F_UFO) && !rt->dst.header_len) {
 843                err = ip_ufo_append_data(sk, queue, getfrag, from, length,
 844                                         hh_len, fragheaderlen, transhdrlen,
 845                                         maxfraglen, flags);
 846                if (err)
 847                        goto error;
 848                return 0;
 849        }
 850
 851        /* So, what's going on in the loop below?
 852         *
 853         * We use calculated fragment length to generate chained skb,
 854         * each of segments is IP fragment ready for sending to network after
 855         * adding appropriate IP header.
 856         */
 857
 858        if (!skb)
 859                goto alloc_new_skb;
 860
 861        while (length > 0) {
 862                /* Check if the remaining data fits into current packet. */
 863                copy = mtu - skb->len;
 864                if (copy < length)
 865                        copy = maxfraglen - skb->len;
 866                if (copy <= 0) {
 867                        char *data;
 868                        unsigned int datalen;
 869                        unsigned int fraglen;
 870                        unsigned int fraggap;
 871                        unsigned int alloclen;
 872                        struct sk_buff *skb_prev;
 873alloc_new_skb:
 874                        skb_prev = skb;
 875                        if (skb_prev)
 876                                fraggap = skb_prev->len - maxfraglen;
 877                        else
 878                                fraggap = 0;
 879
 880                        /*
 881                         * If remaining data exceeds the mtu,
 882                         * we know we need more fragment(s).
 883                         */
 884                        datalen = length + fraggap;
 885                        if (datalen > mtu - fragheaderlen)
 886                                datalen = maxfraglen - fragheaderlen;
 887                        fraglen = datalen + fragheaderlen;
 888
 889                        if ((flags & MSG_MORE) &&
 890                            !(rt->dst.dev->features&NETIF_F_SG))
 891                                alloclen = mtu;
 892                        else
 893                                alloclen = fraglen;
 894
 895                        alloclen += exthdrlen;
 896
 897                        /* The last fragment gets additional space at tail.
 898                         * Note, with MSG_MORE we overallocate on fragments,
 899                         * because we have no idea what fragment will be
 900                         * the last.
 901                         */
 902                        if (datalen == length + fraggap)
 903                                alloclen += rt->dst.trailer_len;
 904
 905                        if (transhdrlen) {
 906                                skb = sock_alloc_send_skb(sk,
 907                                                alloclen + hh_len + 15,
 908                                                (flags & MSG_DONTWAIT), &err);
 909                        } else {
 910                                skb = NULL;
 911                                if (atomic_read(&sk->sk_wmem_alloc) <=
 912                                    2 * sk->sk_sndbuf)
 913                                        skb = sock_wmalloc(sk,
 914                                                           alloclen + hh_len + 15, 1,
 915                                                           sk->sk_allocation);
 916                                if (unlikely(skb == NULL))
 917                                        err = -ENOBUFS;
 918                                else
 919                                        /* only the initial fragment is
 920                                           time stamped */
 921                                        cork->tx_flags = 0;
 922                        }
 923                        if (skb == NULL)
 924                                goto error;
 925
 926                        /*
 927                         *      Fill in the control structures
 928                         */
 929                        skb->ip_summed = csummode;
 930                        skb->csum = 0;
 931                        skb_reserve(skb, hh_len);
 932                        skb_shinfo(skb)->tx_flags = cork->tx_flags;
 933
 934                        /*
 935                         *      Find where to start putting bytes.
 936                         */
 937                        data = skb_put(skb, fraglen + exthdrlen);
 938                        skb_set_network_header(skb, exthdrlen);
 939                        skb->transport_header = (skb->network_header +
 940                                                 fragheaderlen);
 941                        data += fragheaderlen + exthdrlen;
 942
 943                        if (fraggap) {
 944                                skb->csum = skb_copy_and_csum_bits(
 945                                        skb_prev, maxfraglen,
 946                                        data + transhdrlen, fraggap, 0);
 947                                skb_prev->csum = csum_sub(skb_prev->csum,
 948                                                          skb->csum);
 949                                data += fraggap;
 950                                pskb_trim_unique(skb_prev, maxfraglen);
 951                        }
 952
 953                        copy = datalen - transhdrlen - fraggap;
 954                        if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
 955                                err = -EFAULT;
 956                                kfree_skb(skb);
 957                                goto error;
 958                        }
 959
 960                        offset += copy;
 961                        length -= datalen - fraggap;
 962                        transhdrlen = 0;
 963                        exthdrlen = 0;
 964                        csummode = CHECKSUM_NONE;
 965
 966                        /*
 967                         * Put the packet on the pending queue.
 968                         */
 969                        __skb_queue_tail(queue, skb);
 970                        continue;
 971                }
 972
 973                if (copy > length)
 974                        copy = length;
 975
 976                if (!(rt->dst.dev->features&NETIF_F_SG)) {
 977                        unsigned int off;
 978
 979                        off = skb->len;
 980                        if (getfrag(from, skb_put(skb, copy),
 981                                        offset, copy, off, skb) < 0) {
 982                                __skb_trim(skb, off);
 983                                err = -EFAULT;
 984                                goto error;
 985                        }
 986                } else {
 987                        int i = skb_shinfo(skb)->nr_frags;
 988                        skb_frag_t *frag = &skb_shinfo(skb)->frags[i-1];
 989                        struct page *page = cork->page;
 990                        int off = cork->off;
 991                        unsigned int left;
 992
 993                        if (page && (left = PAGE_SIZE - off) > 0) {
 994                                if (copy >= left)
 995                                        copy = left;
 996                                if (page != skb_frag_page(frag)) {
 997                                        if (i == MAX_SKB_FRAGS) {
 998                                                err = -EMSGSIZE;
 999                                                goto error;
1000                                        }
1001                                        skb_fill_page_desc(skb, i, page, off, 0);
1002                                        skb_frag_ref(skb, i);
1003                                        frag = &skb_shinfo(skb)->frags[i];
1004                                }
1005                        } else if (i < MAX_SKB_FRAGS) {
1006                                if (copy > PAGE_SIZE)
1007                                        copy = PAGE_SIZE;
1008                                page = alloc_pages(sk->sk_allocation, 0);
1009                                if (page == NULL)  {
1010                                        err = -ENOMEM;
1011                                        goto error;
1012                                }
1013                                cork->page = page;
1014                                cork->off = 0;
1015
1016                                skb_fill_page_desc(skb, i, page, 0, 0);
1017                                frag = &skb_shinfo(skb)->frags[i];
1018                        } else {
1019                                err = -EMSGSIZE;
1020                                goto error;
1021                        }
1022                        if (getfrag(from, skb_frag_address(frag)+skb_frag_size(frag),
1023                                    offset, copy, skb->len, skb) < 0) {
1024                                err = -EFAULT;
1025                                goto error;
1026                        }
1027                        cork->off += copy;
1028                        skb_frag_size_add(frag, copy);
1029                        skb->len += copy;
1030                        skb->data_len += copy;
1031                        skb->truesize += copy;
1032                        atomic_add(copy, &sk->sk_wmem_alloc);
1033                }
1034                offset += copy;
1035                length -= copy;
1036        }
1037
1038        return 0;
1039
1040error:
1041        cork->length -= length;
1042        IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1043        return err;
1044}
1045
1046static int ip_setup_cork(struct sock *sk, struct inet_cork *cork,
1047                         struct ipcm_cookie *ipc, struct rtable **rtp)
1048{
1049        struct inet_sock *inet = inet_sk(sk);
1050        struct ip_options_rcu *opt;
1051        struct rtable *rt;
1052
1053        /*
1054         * setup for corking.
1055         */
1056        opt = ipc->opt;
1057        if (opt) {
1058                if (cork->opt == NULL) {
1059                        cork->opt = kmalloc(sizeof(struct ip_options) + 40,
1060                                            sk->sk_allocation);
1061                        if (unlikely(cork->opt == NULL))
1062                                return -ENOBUFS;
1063                }
1064                memcpy(cork->opt, &opt->opt, sizeof(struct ip_options) + opt->opt.optlen);
1065                cork->flags |= IPCORK_OPT;
1066                cork->addr = ipc->addr;
1067        }
1068        rt = *rtp;
1069        if (unlikely(!rt))
1070                return -EFAULT;
1071        /*
1072         * We steal reference to this route, caller should not release it
1073         */
1074        *rtp = NULL;
1075        cork->fragsize = inet->pmtudisc == IP_PMTUDISC_PROBE ?
1076                         rt->dst.dev->mtu : dst_mtu(&rt->dst);
1077        cork->dst = &rt->dst;
1078        cork->length = 0;
1079        cork->tx_flags = ipc->tx_flags;
1080        cork->page = NULL;
1081        cork->off = 0;
1082
1083        return 0;
1084}
1085
1086/*
1087 *      ip_append_data() and ip_append_page() can make one large IP datagram
1088 *      from many pieces of data. Each pieces will be holded on the socket
1089 *      until ip_push_pending_frames() is called. Each piece can be a page
1090 *      or non-page data.
1091 *
1092 *      Not only UDP, other transport protocols - e.g. raw sockets - can use
1093 *      this interface potentially.
1094 *
1095 *      LATER: length must be adjusted by pad at tail, when it is required.
1096 */
1097int ip_append_data(struct sock *sk, struct flowi4 *fl4,
1098                   int getfrag(void *from, char *to, int offset, int len,
1099                               int odd, struct sk_buff *skb),
1100                   void *from, int length, int transhdrlen,
1101                   struct ipcm_cookie *ipc, struct rtable **rtp,
1102                   unsigned int flags)
1103{
1104        struct inet_sock *inet = inet_sk(sk);
1105        int err;
1106
1107        if (flags&MSG_PROBE)
1108                return 0;
1109
1110        if (skb_queue_empty(&sk->sk_write_queue)) {
1111                err = ip_setup_cork(sk, &inet->cork.base, ipc, rtp);
1112                if (err)
1113                        return err;
1114        } else {
1115                transhdrlen = 0;
1116        }
1117
1118        return __ip_append_data(sk, fl4, &sk->sk_write_queue, &inet->cork.base, getfrag,
1119                                from, length, transhdrlen, flags);
1120}
1121
1122ssize_t ip_append_page(struct sock *sk, struct flowi4 *fl4, struct page *page,
1123                       int offset, size_t size, int flags)
1124{
1125        struct inet_sock *inet = inet_sk(sk);
1126        struct sk_buff *skb;
1127        struct rtable *rt;
1128        struct ip_options *opt = NULL;
1129        struct inet_cork *cork;
1130        int hh_len;
1131        int mtu;
1132        int len;
1133        int err;
1134        unsigned int maxfraglen, fragheaderlen, fraggap;
1135
1136        if (inet->hdrincl)
1137                return -EPERM;
1138
1139        if (flags&MSG_PROBE)
1140                return 0;
1141
1142        if (skb_queue_empty(&sk->sk_write_queue))
1143                return -EINVAL;
1144
1145        cork = &inet->cork.base;
1146        rt = (struct rtable *)cork->dst;
1147        if (cork->flags & IPCORK_OPT)
1148                opt = cork->opt;
1149
1150        if (!(rt->dst.dev->features&NETIF_F_SG))
1151                return -EOPNOTSUPP;
1152
1153        hh_len = LL_RESERVED_SPACE(rt->dst.dev);
1154        mtu = cork->fragsize;
1155
1156        fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
1157        maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
1158
1159        if (cork->length + size > 0xFFFF - fragheaderlen) {
1160                ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport, mtu);
1161                return -EMSGSIZE;
1162        }
1163
1164        if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
1165                return -EINVAL;
1166
1167        cork->length += size;
1168        if ((size + skb->len > mtu) &&
1169            (sk->sk_protocol == IPPROTO_UDP) &&
1170            (rt->dst.dev->features & NETIF_F_UFO)) {
1171                skb_shinfo(skb)->gso_size = mtu - fragheaderlen;
1172                skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
1173        }
1174
1175
1176        while (size > 0) {
1177                int i;
1178
1179                if (skb_is_gso(skb))
1180                        len = size;
1181                else {
1182
1183                        /* Check if the remaining data fits into current packet. */
1184                        len = mtu - skb->len;
1185                        if (len < size)
1186                                len = maxfraglen - skb->len;
1187                }
1188                if (len <= 0) {
1189                        struct sk_buff *skb_prev;
1190                        int alloclen;
1191
1192                        skb_prev = skb;
1193                        fraggap = skb_prev->len - maxfraglen;
1194
1195                        alloclen = fragheaderlen + hh_len + fraggap + 15;
1196                        skb = sock_wmalloc(sk, alloclen, 1, sk->sk_allocation);
1197                        if (unlikely(!skb)) {
1198                                err = -ENOBUFS;
1199                                goto error;
1200                        }
1201
1202                        /*
1203                         *      Fill in the control structures
1204                         */
1205                        skb->ip_summed = CHECKSUM_NONE;
1206                        skb->csum = 0;
1207                        skb_reserve(skb, hh_len);
1208
1209                        /*
1210                         *      Find where to start putting bytes.
1211                         */
1212                        skb_put(skb, fragheaderlen + fraggap);
1213                        skb_reset_network_header(skb);
1214                        skb->transport_header = (skb->network_header +
1215                                                 fragheaderlen);
1216                        if (fraggap) {
1217                                skb->csum = skb_copy_and_csum_bits(skb_prev,
1218                                                                   maxfraglen,
1219                                                    skb_transport_header(skb),
1220                                                                   fraggap, 0);
1221                                skb_prev->csum = csum_sub(skb_prev->csum,
1222                                                          skb->csum);
1223                                pskb_trim_unique(skb_prev, maxfraglen);
1224                        }
1225
1226                        /*
1227                         * Put the packet on the pending queue.
1228                         */
1229                        __skb_queue_tail(&sk->sk_write_queue, skb);
1230                        continue;
1231                }
1232
1233                i = skb_shinfo(skb)->nr_frags;
1234                if (len > size)
1235                        len = size;
1236                if (skb_can_coalesce(skb, i, page, offset)) {
1237                        skb_frag_size_add(&skb_shinfo(skb)->frags[i-1], len);
1238                } else if (i < MAX_SKB_FRAGS) {
1239                        get_page(page);
1240                        skb_fill_page_desc(skb, i, page, offset, len);
1241                } else {
1242                        err = -EMSGSIZE;
1243                        goto error;
1244                }
1245
1246                if (skb->ip_summed == CHECKSUM_NONE) {
1247                        __wsum csum;
1248                        csum = csum_page(page, offset, len);
1249                        skb->csum = csum_block_add(skb->csum, csum, skb->len);
1250                }
1251
1252                skb->len += len;
1253                skb->data_len += len;
1254                skb->truesize += len;
1255                atomic_add(len, &sk->sk_wmem_alloc);
1256                offset += len;
1257                size -= len;
1258        }
1259        return 0;
1260
1261error:
1262        cork->length -= size;
1263        IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1264        return err;
1265}
1266
1267static void ip_cork_release(struct inet_cork *cork)
1268{
1269        cork->flags &= ~IPCORK_OPT;
1270        kfree(cork->opt);
1271        cork->opt = NULL;
1272        dst_release(cork->dst);
1273        cork->dst = NULL;
1274}
1275
1276/*
1277 *      Combined all pending IP fragments on the socket as one IP datagram
1278 *      and push them out.
1279 */
1280struct sk_buff *__ip_make_skb(struct sock *sk,
1281                              struct flowi4 *fl4,
1282                              struct sk_buff_head *queue,
1283                              struct inet_cork *cork)
1284{
1285        struct sk_buff *skb, *tmp_skb;
1286        struct sk_buff **tail_skb;
1287        struct inet_sock *inet = inet_sk(sk);
1288        struct net *net = sock_net(sk);
1289        struct ip_options *opt = NULL;
1290        struct rtable *rt = (struct rtable *)cork->dst;
1291        struct iphdr *iph;
1292        __be16 df = 0;
1293        __u8 ttl;
1294
1295        if ((skb = __skb_dequeue(queue)) == NULL)
1296                goto out;
1297        tail_skb = &(skb_shinfo(skb)->frag_list);
1298
1299        /* move skb->data to ip header from ext header */
1300        if (skb->data < skb_network_header(skb))
1301                __skb_pull(skb, skb_network_offset(skb));
1302        while ((tmp_skb = __skb_dequeue(queue)) != NULL) {
1303                __skb_pull(tmp_skb, skb_network_header_len(skb));
1304                *tail_skb = tmp_skb;
1305                tail_skb = &(tmp_skb->next);
1306                skb->len += tmp_skb->len;
1307                skb->data_len += tmp_skb->len;
1308                skb->truesize += tmp_skb->truesize;
1309                tmp_skb->destructor = NULL;
1310                tmp_skb->sk = NULL;
1311        }
1312
1313        /* Unless user demanded real pmtu discovery (IP_PMTUDISC_DO), we allow
1314         * to fragment the frame generated here. No matter, what transforms
1315         * how transforms change size of the packet, it will come out.
1316         */
1317        if (inet->pmtudisc < IP_PMTUDISC_DO)
1318                skb->local_df = 1;
1319
1320        /* DF bit is set when we want to see DF on outgoing frames.
1321         * If local_df is set too, we still allow to fragment this frame
1322         * locally. */
1323        if (inet->pmtudisc >= IP_PMTUDISC_DO ||
1324            (skb->len <= dst_mtu(&rt->dst) &&
1325             ip_dont_fragment(sk, &rt->dst)))
1326                df = htons(IP_DF);
1327
1328        if (cork->flags & IPCORK_OPT)
1329                opt = cork->opt;
1330
1331        if (rt->rt_type == RTN_MULTICAST)
1332                ttl = inet->mc_ttl;
1333        else
1334                ttl = ip_select_ttl(inet, &rt->dst);
1335
1336        iph = (struct iphdr *)skb->data;
1337        iph->version = 4;
1338        iph->ihl = 5;
1339        iph->tos = inet->tos;
1340        iph->frag_off = df;
1341        iph->ttl = ttl;
1342        iph->protocol = sk->sk_protocol;
1343        ip_copy_addrs(iph, fl4);
1344        ip_select_ident(iph, &rt->dst, sk);
1345
1346        if (opt) {
1347                iph->ihl += opt->optlen>>2;
1348                ip_options_build(skb, opt, cork->addr, rt, 0);
1349        }
1350
1351        skb->priority = sk->sk_priority;
1352        skb->mark = sk->sk_mark;
1353        /*
1354         * Steal rt from cork.dst to avoid a pair of atomic_inc/atomic_dec
1355         * on dst refcount
1356         */
1357        cork->dst = NULL;
1358        skb_dst_set(skb, &rt->dst);
1359
1360        if (iph->protocol == IPPROTO_ICMP)
1361                icmp_out_count(net, ((struct icmphdr *)
1362                        skb_transport_header(skb))->type);
1363
1364        ip_cork_release(cork);
1365out:
1366        return skb;
1367}
1368
1369int ip_send_skb(struct net *net, struct sk_buff *skb)
1370{
1371        int err;
1372
1373        err = ip_local_out(skb);
1374        if (err) {
1375                if (err > 0)
1376                        err = net_xmit_errno(err);
1377                if (err)
1378                        IP_INC_STATS(net, IPSTATS_MIB_OUTDISCARDS);
1379        }
1380
1381        return err;
1382}
1383
1384int ip_push_pending_frames(struct sock *sk, struct flowi4 *fl4)
1385{
1386        struct sk_buff *skb;
1387
1388        skb = ip_finish_skb(sk, fl4);
1389        if (!skb)
1390                return 0;
1391
1392        /* Netfilter gets whole the not fragmented skb. */
1393        return ip_send_skb(sock_net(sk), skb);
1394}
1395
1396/*
1397 *      Throw away all pending data on the socket.
1398 */
1399static void __ip_flush_pending_frames(struct sock *sk,
1400                                      struct sk_buff_head *queue,
1401                                      struct inet_cork *cork)
1402{
1403        struct sk_buff *skb;
1404
1405        while ((skb = __skb_dequeue_tail(queue)) != NULL)
1406                kfree_skb(skb);
1407
1408        ip_cork_release(cork);
1409}
1410
1411void ip_flush_pending_frames(struct sock *sk)
1412{
1413        __ip_flush_pending_frames(sk, &sk->sk_write_queue, &inet_sk(sk)->cork.base);
1414}
1415
1416struct sk_buff *ip_make_skb(struct sock *sk,
1417                            struct flowi4 *fl4,
1418                            int getfrag(void *from, char *to, int offset,
1419                                        int len, int odd, struct sk_buff *skb),
1420                            void *from, int length, int transhdrlen,
1421                            struct ipcm_cookie *ipc, struct rtable **rtp,
1422                            unsigned int flags)
1423{
1424        struct inet_cork cork;
1425        struct sk_buff_head queue;
1426        int err;
1427
1428        if (flags & MSG_PROBE)
1429                return NULL;
1430
1431        __skb_queue_head_init(&queue);
1432
1433        cork.flags = 0;
1434        cork.addr = 0;
1435        cork.opt = NULL;
1436        err = ip_setup_cork(sk, &cork, ipc, rtp);
1437        if (err)
1438                return ERR_PTR(err);
1439
1440        err = __ip_append_data(sk, fl4, &queue, &cork, getfrag,
1441                               from, length, transhdrlen, flags);
1442        if (err) {
1443                __ip_flush_pending_frames(sk, &queue, &cork);
1444                return ERR_PTR(err);
1445        }
1446
1447        return __ip_make_skb(sk, fl4, &queue, &cork);
1448}
1449
1450/*
1451 *      Fetch data from kernel space and fill in checksum if needed.
1452 */
1453static int ip_reply_glue_bits(void *dptr, char *to, int offset,
1454                              int len, int odd, struct sk_buff *skb)
1455{
1456        __wsum csum;
1457
1458        csum = csum_partial_copy_nocheck(dptr+offset, to, len, 0);
1459        skb->csum = csum_block_add(skb->csum, csum, odd);
1460        return 0;
1461}
1462
1463/*
1464 *      Generic function to send a packet as reply to another packet.
1465 *      Used to send some TCP resets/acks so far.
1466 *
1467 *      Use a fake percpu inet socket to avoid false sharing and contention.
1468 */
1469static DEFINE_PER_CPU(struct inet_sock, unicast_sock) = {
1470        .sk = {
1471                .__sk_common = {
1472                        .skc_refcnt = ATOMIC_INIT(1),
1473                },
1474                .sk_wmem_alloc  = ATOMIC_INIT(1),
1475                .sk_allocation  = GFP_ATOMIC,
1476                .sk_flags       = (1UL << SOCK_USE_WRITE_QUEUE),
1477        },
1478        .pmtudisc       = IP_PMTUDISC_WANT,
1479        .uc_ttl         = -1,
1480};
1481
1482void ip_send_unicast_reply(struct net *net, struct sk_buff *skb, __be32 daddr,
1483                           __be32 saddr, const struct ip_reply_arg *arg,
1484                           unsigned int len)
1485{
1486        struct ip_options_data replyopts;
1487        struct ipcm_cookie ipc;
1488        struct flowi4 fl4;
1489        struct rtable *rt = skb_rtable(skb);
1490        struct sk_buff *nskb;
1491        struct sock *sk;
1492        struct inet_sock *inet;
1493
1494        if (ip_options_echo(&replyopts.opt.opt, skb))
1495                return;
1496
1497        ipc.addr = daddr;
1498        ipc.opt = NULL;
1499        ipc.tx_flags = 0;
1500
1501        if (replyopts.opt.opt.optlen) {
1502                ipc.opt = &replyopts.opt;
1503
1504                if (replyopts.opt.opt.srr)
1505                        daddr = replyopts.opt.opt.faddr;
1506        }
1507
1508        flowi4_init_output(&fl4, arg->bound_dev_if, 0,
1509                           RT_TOS(arg->tos),
1510                           RT_SCOPE_UNIVERSE, ip_hdr(skb)->protocol,
1511                           ip_reply_arg_flowi_flags(arg),
1512                           daddr, saddr,
1513                           tcp_hdr(skb)->source, tcp_hdr(skb)->dest);
1514        security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
1515        rt = ip_route_output_key(net, &fl4);
1516        if (IS_ERR(rt))
1517                return;
1518
1519        inet = &get_cpu_var(unicast_sock);
1520
1521        inet->tos = arg->tos;
1522        sk = &inet->sk;
1523        sk->sk_priority = skb->priority;
1524        sk->sk_protocol = ip_hdr(skb)->protocol;
1525        sk->sk_bound_dev_if = arg->bound_dev_if;
1526        sock_net_set(sk, net);
1527        __skb_queue_head_init(&sk->sk_write_queue);
1528        sk->sk_sndbuf = sysctl_wmem_default;
1529        ip_append_data(sk, &fl4, ip_reply_glue_bits, arg->iov->iov_base, len, 0,
1530                       &ipc, &rt, MSG_DONTWAIT);
1531        nskb = skb_peek(&sk->sk_write_queue);
1532        if (nskb) {
1533                if (arg->csumoffset >= 0)
1534                        *((__sum16 *)skb_transport_header(nskb) +
1535                          arg->csumoffset) = csum_fold(csum_add(nskb->csum,
1536                                                                arg->csum));
1537                nskb->ip_summed = CHECKSUM_NONE;
1538                skb_orphan(nskb);
1539                skb_set_queue_mapping(nskb, skb_get_queue_mapping(skb));
1540                ip_push_pending_frames(sk, &fl4);
1541        }
1542
1543        put_cpu_var(unicast_sock);
1544
1545        ip_rt_put(rt);
1546}
1547
1548void __init ip_init(void)
1549{
1550        ip_rt_init();
1551        inet_initpeers();
1552
1553#if defined(CONFIG_IP_MULTICAST) && defined(CONFIG_PROC_FS)
1554        igmp_mc_proc_init();
1555#endif
1556}
1557
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