net/ipv4/ip_output.c

/* [<][>][^][v][top][bottom][index][help] */
This source file includes following definitions.
ip_send_check
__ip_local_out
ip_local_out
ip_select_ttl
ip_build_and_send_pkt
ip_finish_output2
ip_finish_output_gso
__ip_finish_output
ip_finish_output
ip_mc_finish_output
ip_mc_output
ip_output
ip_copy_addrs
__ip_queue_xmit
ip_copy_metadata
ip_fragment
ip_fraglist_init
ip_fraglist_ipcb_prepare
ip_fraglist_prepare
ip_frag_init
ip_frag_ipcb
ip_frag_next
ip_do_fragment
ip_generic_getfrag
csum_page
__ip_append_data
ip_setup_cork
ip_append_data
ip_append_page
ip_cork_release
__ip_make_skb
ip_send_skb
ip_push_pending_frames
__ip_flush_pending_frames
ip_flush_pending_frames
ip_make_skb
ip_reply_glue_bits
ip_send_unicast_reply
ip_init
   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * INET         An implementation of the TCP/IP protocol suite for the LINUX
   4  *              operating system.  INET is implemented using the  BSD Socket
   5  *              interface as the means of communication with the user level.
   6  *
   7  *              The Internet Protocol (IP) output module.
   8  *
   9  * Authors:     Ross Biro
  10  *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
  11  *              Donald Becker, <becker@super.org>
  12  *              Alan Cox, <Alan.Cox@linux.org>
  13  *              Richard Underwood
  14  *              Stefan Becker, <stefanb@yello.ping.de>
  15  *              Jorge Cwik, <jorge@laser.satlink.net>
  16  *              Arnt Gulbrandsen, <agulbra@nvg.unit.no>
  17  *              Hirokazu Takahashi, <taka@valinux.co.jp>
  18  *
  19  *      See ip_input.c for original log
  20  *
  21  *      Fixes:
  22  *              Alan Cox        :       Missing nonblock feature in ip_build_xmit.
  23  *              Mike Kilburn    :       htons() missing in ip_build_xmit.
  24  *              Bradford Johnson:       Fix faulty handling of some frames when
  25  *                                      no route is found.
  26  *              Alexander Demenshin:    Missing sk/skb free in ip_queue_xmit
  27  *                                      (in case if packet not accepted by
  28  *                                      output firewall rules)
  29  *              Mike McLagan    :       Routing by source
  30  *              Alexey Kuznetsov:       use new route cache
  31  *              Andi Kleen:             Fix broken PMTU recovery and remove
  32  *                                      some redundant tests.
  33  *      Vitaly E. Lavrov        :       Transparent proxy revived after year coma.
  34  *              Andi Kleen      :       Replace ip_reply with ip_send_reply.
  35  *              Andi Kleen      :       Split fast and slow ip_build_xmit path
  36  *                                      for decreased register pressure on x86
  37  *                                      and more readibility.
  38  *              Marc Boucher    :       When call_out_firewall returns FW_QUEUE,
  39  *                                      silently drop skb instead of failing with -EPERM.
  40  *              Detlev Wengorz  :       Copy protocol for fragments.
  41  *              Hirokazu Takahashi:     HW checksumming for outgoing UDP
  42  *                                      datagrams.
  43  *              Hirokazu Takahashi:     sendfile() on UDP works now.
  44  */
  45 
  46 #include <linux/uaccess.h>
  47 #include <linux/module.h>
  48 #include <linux/types.h>
  49 #include <linux/kernel.h>
  50 #include <linux/mm.h>
  51 #include <linux/string.h>
  52 #include <linux/errno.h>
  53 #include <linux/highmem.h>
  54 #include <linux/slab.h>
  55 
  56 #include <linux/socket.h>
  57 #include <linux/sockios.h>
  58 #include <linux/in.h>
  59 #include <linux/inet.h>
  60 #include <linux/netdevice.h>
  61 #include <linux/etherdevice.h>
  62 #include <linux/proc_fs.h>
  63 #include <linux/stat.h>
  64 #include <linux/init.h>
  65 
  66 #include <net/snmp.h>
  67 #include <net/ip.h>
  68 #include <net/protocol.h>
  69 #include <net/route.h>
  70 #include <net/xfrm.h>
  71 #include <linux/skbuff.h>
  72 #include <net/sock.h>
  73 #include <net/arp.h>
  74 #include <net/icmp.h>
  75 #include <net/checksum.h>
  76 #include <net/inetpeer.h>
  77 #include <net/lwtunnel.h>
  78 #include <linux/bpf-cgroup.h>
  79 #include <linux/igmp.h>
  80 #include <linux/netfilter_ipv4.h>
  81 #include <linux/netfilter_bridge.h>
  82 #include <linux/netlink.h>
  83 #include <linux/tcp.h>
  84 
  85 static int
  86 ip_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
  87             unsigned int mtu,
  88             int (*output)(struct net *, struct sock *, struct sk_buff *));
  89 
  90 /* Generate a checksum for an outgoing IP datagram. */
  91 void ip_send_check(struct iphdr *iph)
  92 {
  93         iph->check = 0;
  94         iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
  95 }
  96 EXPORT_SYMBOL(ip_send_check);
  97 
  98 int __ip_local_out(struct net *net, struct sock *sk, struct sk_buff *skb)
  99 {
 100         struct iphdr *iph = ip_hdr(skb);
 101 
 102         iph->tot_len = htons(skb->len);
 103         ip_send_check(iph);
 104 
 105         /* if egress device is enslaved to an L3 master device pass the
 106          * skb to its handler for processing
 107          */
 108         skb = l3mdev_ip_out(sk, skb);
 109         if (unlikely(!skb))
 110                 return 0;
 111 
 112         skb->protocol = htons(ETH_P_IP);
 113 
 114         return nf_hook(NFPROTO_IPV4, NF_INET_LOCAL_OUT,
 115                        net, sk, skb, NULL, skb_dst(skb)->dev,
 116                        dst_output);
 117 }
 118 
 119 int ip_local_out(struct net *net, struct sock *sk, struct sk_buff *skb)
 120 {
 121         int err;
 122 
 123         err = __ip_local_out(net, sk, skb);
 124         if (likely(err == 1))
 125                 err = dst_output(net, sk, skb);
 126 
 127         return err;
 128 }
 129 EXPORT_SYMBOL_GPL(ip_local_out);
 130 
 131 static inline int ip_select_ttl(struct inet_sock *inet, struct dst_entry *dst)
 132 {
 133         int ttl = inet->uc_ttl;
 134 
 135         if (ttl < 0)
 136                 ttl = ip4_dst_hoplimit(dst);
 137         return ttl;
 138 }
 139 
 140 /*
 141  *              Add an ip header to a skbuff and send it out.
 142  *
 143  */
 144 int ip_build_and_send_pkt(struct sk_buff *skb, const struct sock *sk,
 145                           __be32 saddr, __be32 daddr, struct ip_options_rcu *opt)
 146 {
 147         struct inet_sock *inet = inet_sk(sk);
 148         struct rtable *rt = skb_rtable(skb);
 149         struct net *net = sock_net(sk);
 150         struct iphdr *iph;
 151 
 152         /* Build the IP header. */
 153         skb_push(skb, sizeof(struct iphdr) + (opt ? opt->opt.optlen : 0));
 154         skb_reset_network_header(skb);
 155         iph = ip_hdr(skb);
 156         iph->version  = 4;
 157         iph->ihl      = 5;
 158         iph->tos      = inet->tos;
 159         iph->ttl      = ip_select_ttl(inet, &rt->dst);
 160         iph->daddr    = (opt && opt->opt.srr ? opt->opt.faddr : daddr);
 161         iph->saddr    = saddr;
 162         iph->protocol = sk->sk_protocol;
 163         if (ip_dont_fragment(sk, &rt->dst)) {
 164                 iph->frag_off = htons(IP_DF);
 165                 iph->id = 0;
 166         } else {
 167                 iph->frag_off = 0;
 168                 __ip_select_ident(net, iph, 1);
 169         }
 170 
 171         if (opt && opt->opt.optlen) {
 172                 iph->ihl += opt->opt.optlen>>2;
 173                 ip_options_build(skb, &opt->opt, daddr, rt, 0);
 174         }
 175 
 176         skb->priority = sk->sk_priority;
 177         if (!skb->mark)
 178                 skb->mark = sk->sk_mark;
 179 
 180         /* Send it out. */
 181         return ip_local_out(net, skb->sk, skb);
 182 }
 183 EXPORT_SYMBOL_GPL(ip_build_and_send_pkt);
 184 
 185 static int ip_finish_output2(struct net *net, struct sock *sk, struct sk_buff *skb)
 186 {
 187         struct dst_entry *dst = skb_dst(skb);
 188         struct rtable *rt = (struct rtable *)dst;
 189         struct net_device *dev = dst->dev;
 190         unsigned int hh_len = LL_RESERVED_SPACE(dev);
 191         struct neighbour *neigh;
 192         bool is_v6gw = false;
 193 
 194         if (rt->rt_type == RTN_MULTICAST) {
 195                 IP_UPD_PO_STATS(net, IPSTATS_MIB_OUTMCAST, skb->len);
 196         } else if (rt->rt_type == RTN_BROADCAST)
 197                 IP_UPD_PO_STATS(net, IPSTATS_MIB_OUTBCAST, skb->len);
 198 
 199         /* Be paranoid, rather than too clever. */
 200         if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) {
 201                 struct sk_buff *skb2;
 202 
 203                 skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev));
 204                 if (!skb2) {
 205                         kfree_skb(skb);
 206                         return -ENOMEM;
 207                 }
 208                 if (skb->sk)
 209                         skb_set_owner_w(skb2, skb->sk);
 210                 consume_skb(skb);
 211                 skb = skb2;
 212         }
 213 
 214         if (lwtunnel_xmit_redirect(dst->lwtstate)) {
 215                 int res = lwtunnel_xmit(skb);
 216 
 217                 if (res < 0 || res == LWTUNNEL_XMIT_DONE)
 218                         return res;
 219         }
 220 
 221         rcu_read_lock_bh();
 222         neigh = ip_neigh_for_gw(rt, skb, &is_v6gw);
 223         if (!IS_ERR(neigh)) {
 224                 int res;
 225 
 226                 sock_confirm_neigh(skb, neigh);
 227                 /* if crossing protocols, can not use the cached header */
 228                 res = neigh_output(neigh, skb, is_v6gw);
 229                 rcu_read_unlock_bh();
 230                 return res;
 231         }
 232         rcu_read_unlock_bh();
 233 
 234         net_dbg_ratelimited("%s: No header cache and no neighbour!\n",
 235                             __func__);
 236         kfree_skb(skb);
 237         return -EINVAL;
 238 }
 239 
 240 static int ip_finish_output_gso(struct net *net, struct sock *sk,
 241                                 struct sk_buff *skb, unsigned int mtu)
 242 {
 243         netdev_features_t features;
 244         struct sk_buff *segs;
 245         int ret = 0;
 246 
 247         /* common case: seglen is <= mtu
 248          */
 249         if (skb_gso_validate_network_len(skb, mtu))
 250                 return ip_finish_output2(net, sk, skb);
 251 
 252         /* Slowpath -  GSO segment length exceeds the egress MTU.
 253          *
 254          * This can happen in several cases:
 255          *  - Forwarding of a TCP GRO skb, when DF flag is not set.
 256          *  - Forwarding of an skb that arrived on a virtualization interface
 257          *    (virtio-net/vhost/tap) with TSO/GSO size set by other network
 258          *    stack.
 259          *  - Local GSO skb transmitted on an NETIF_F_TSO tunnel stacked over an
 260          *    interface with a smaller MTU.
 261          *  - Arriving GRO skb (or GSO skb in a virtualized environment) that is
 262          *    bridged to a NETIF_F_TSO tunnel stacked over an interface with an
 263          *    insufficent MTU.
 264          */
 265         features = netif_skb_features(skb);
 266         BUILD_BUG_ON(sizeof(*IPCB(skb)) > SKB_SGO_CB_OFFSET);
 267         segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK);
 268         if (IS_ERR_OR_NULL(segs)) {
 269                 kfree_skb(skb);
 270                 return -ENOMEM;
 271         }
 272 
 273         consume_skb(skb);
 274 
 275         do {
 276                 struct sk_buff *nskb = segs->next;
 277                 int err;
 278 
 279                 skb_mark_not_on_list(segs);
 280                 err = ip_fragment(net, sk, segs, mtu, ip_finish_output2);
 281 
 282                 if (err && ret == 0)
 283                         ret = err;
 284                 segs = nskb;
 285         } while (segs);
 286 
 287         return ret;
 288 }
 289 
 290 static int __ip_finish_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 291 {
 292         unsigned int mtu;
 293 
 294 #if defined(CONFIG_NETFILTER) && defined(CONFIG_XFRM)
 295         /* Policy lookup after SNAT yielded a new policy */
 296         if (skb_dst(skb)->xfrm) {
 297                 IPCB(skb)->flags |= IPSKB_REROUTED;
 298                 return dst_output(net, sk, skb);
 299         }
 300 #endif
 301         mtu = ip_skb_dst_mtu(sk, skb);
 302         if (skb_is_gso(skb))
 303                 return ip_finish_output_gso(net, sk, skb, mtu);
 304 
 305         if (skb->len > mtu || (IPCB(skb)->flags & IPSKB_FRAG_PMTU))
 306                 return ip_fragment(net, sk, skb, mtu, ip_finish_output2);
 307 
 308         return ip_finish_output2(net, sk, skb);
 309 }
 310 
 311 static int ip_finish_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 312 {
 313         int ret;
 314 
 315         ret = BPF_CGROUP_RUN_PROG_INET_EGRESS(sk, skb);
 316         switch (ret) {
 317         case NET_XMIT_SUCCESS:
 318                 return __ip_finish_output(net, sk, skb);
 319         case NET_XMIT_CN:
 320                 return __ip_finish_output(net, sk, skb) ? : ret;
 321         default:
 322                 kfree_skb(skb);
 323                 return ret;
 324         }
 325 }
 326 
 327 static int ip_mc_finish_output(struct net *net, struct sock *sk,
 328                                struct sk_buff *skb)
 329 {
 330         struct rtable *new_rt;
 331         bool do_cn = false;
 332         int ret, err;
 333 
 334         ret = BPF_CGROUP_RUN_PROG_INET_EGRESS(sk, skb);
 335         switch (ret) {
 336         case NET_XMIT_CN:
 337                 do_cn = true;
 338                 /* fall through */
 339         case NET_XMIT_SUCCESS:
 340                 break;
 341         default:
 342                 kfree_skb(skb);
 343                 return ret;
 344         }
 345 
 346         /* Reset rt_iif so that inet_iif() will return skb->skb_iif. Setting
 347          * this to non-zero causes ipi_ifindex in in_pktinfo to be overwritten,
 348          * see ipv4_pktinfo_prepare().
 349          */
 350         new_rt = rt_dst_clone(net->loopback_dev, skb_rtable(skb));
 351         if (new_rt) {
 352                 new_rt->rt_iif = 0;
 353                 skb_dst_drop(skb);
 354                 skb_dst_set(skb, &new_rt->dst);
 355         }
 356 
 357         err = dev_loopback_xmit(net, sk, skb);
 358         return (do_cn && err) ? ret : err;
 359 }
 360 
 361 int ip_mc_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 362 {
 363         struct rtable *rt = skb_rtable(skb);
 364         struct net_device *dev = rt->dst.dev;
 365 
 366         /*
 367          *      If the indicated interface is up and running, send the packet.
 368          */
 369         IP_UPD_PO_STATS(net, IPSTATS_MIB_OUT, skb->len);
 370 
 371         skb->dev = dev;
 372         skb->protocol = htons(ETH_P_IP);
 373 
 374         /*
 375          *      Multicasts are looped back for other local users
 376          */
 377 
 378         if (rt->rt_flags&RTCF_MULTICAST) {
 379                 if (sk_mc_loop(sk)
 380 #ifdef CONFIG_IP_MROUTE
 381                 /* Small optimization: do not loopback not local frames,
 382                    which returned after forwarding; they will be  dropped
 383                    by ip_mr_input in any case.
 384                    Note, that local frames are looped back to be delivered
 385                    to local recipients.
 386 
 387                    This check is duplicated in ip_mr_input at the moment.
 388                  */
 389                     &&
 390                     ((rt->rt_flags & RTCF_LOCAL) ||
 391                      !(IPCB(skb)->flags & IPSKB_FORWARDED))
 392 #endif
 393                    ) {
 394                         struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
 395                         if (newskb)
 396                                 NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING,
 397                                         net, sk, newskb, NULL, newskb->dev,
 398                                         ip_mc_finish_output);
 399                 }
 400 
 401                 /* Multicasts with ttl 0 must not go beyond the host */
 402 
 403                 if (ip_hdr(skb)->ttl == 0) {
 404                         kfree_skb(skb);
 405                         return 0;
 406                 }
 407         }
 408 
 409         if (rt->rt_flags&RTCF_BROADCAST) {
 410                 struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
 411                 if (newskb)
 412                         NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING,
 413                                 net, sk, newskb, NULL, newskb->dev,
 414                                 ip_mc_finish_output);
 415         }
 416 
 417         return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
 418                             net, sk, skb, NULL, skb->dev,
 419                             ip_finish_output,
 420                             !(IPCB(skb)->flags & IPSKB_REROUTED));
 421 }
 422 
 423 int ip_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 424 {
 425         struct net_device *dev = skb_dst(skb)->dev;
 426 
 427         IP_UPD_PO_STATS(net, IPSTATS_MIB_OUT, skb->len);
 428 
 429         skb->dev = dev;
 430         skb->protocol = htons(ETH_P_IP);
 431 
 432         return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
 433                             net, sk, skb, NULL, dev,
 434                             ip_finish_output,
 435                             !(IPCB(skb)->flags & IPSKB_REROUTED));
 436 }
 437 
 438 /*
 439  * copy saddr and daddr, possibly using 64bit load/stores
 440  * Equivalent to :
 441  *   iph->saddr = fl4->saddr;
 442  *   iph->daddr = fl4->daddr;
 443  */
 444 static void ip_copy_addrs(struct iphdr *iph, const struct flowi4 *fl4)
 445 {
 446         BUILD_BUG_ON(offsetof(typeof(*fl4), daddr) !=
 447                      offsetof(typeof(*fl4), saddr) + sizeof(fl4->saddr));
 448         memcpy(&iph->saddr, &fl4->saddr,
 449                sizeof(fl4->saddr) + sizeof(fl4->daddr));
 450 }
 451 
 452 /* Note: skb->sk can be different from sk, in case of tunnels */
 453 int __ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl,
 454                     __u8 tos)
 455 {
 456         struct inet_sock *inet = inet_sk(sk);
 457         struct net *net = sock_net(sk);
 458         struct ip_options_rcu *inet_opt;
 459         struct flowi4 *fl4;
 460         struct rtable *rt;
 461         struct iphdr *iph;
 462         int res;
 463 
 464         /* Skip all of this if the packet is already routed,
 465          * f.e. by something like SCTP.
 466          */
 467         rcu_read_lock();
 468         inet_opt = rcu_dereference(inet->inet_opt);
 469         fl4 = &fl->u.ip4;
 470         rt = skb_rtable(skb);
 471         if (rt)
 472                 goto packet_routed;
 473 
 474         /* Make sure we can route this packet. */
 475         rt = (struct rtable *)__sk_dst_check(sk, 0);
 476         if (!rt) {
 477                 __be32 daddr;
 478 
 479                 /* Use correct destination address if we have options. */
 480                 daddr = inet->inet_daddr;
 481                 if (inet_opt && inet_opt->opt.srr)
 482                         daddr = inet_opt->opt.faddr;
 483 
 484                 /* If this fails, retransmit mechanism of transport layer will
 485                  * keep trying until route appears or the connection times
 486                  * itself out.
 487                  */
 488                 rt = ip_route_output_ports(net, fl4, sk,
 489                                            daddr, inet->inet_saddr,
 490                                            inet->inet_dport,
 491                                            inet->inet_sport,
 492                                            sk->sk_protocol,
 493                                            RT_CONN_FLAGS_TOS(sk, tos),
 494                                            sk->sk_bound_dev_if);
 495                 if (IS_ERR(rt))
 496                         goto no_route;
 497                 sk_setup_caps(sk, &rt->dst);
 498         }
 499         skb_dst_set_noref(skb, &rt->dst);
 500 
 501 packet_routed:
 502         if (inet_opt && inet_opt->opt.is_strictroute && rt->rt_uses_gateway)
 503                 goto no_route;
 504 
 505         /* OK, we know where to send it, allocate and build IP header. */
 506         skb_push(skb, sizeof(struct iphdr) + (inet_opt ? inet_opt->opt.optlen : 0));
 507         skb_reset_network_header(skb);
 508         iph = ip_hdr(skb);
 509         *((__be16 *)iph) = htons((4 << 12) | (5 << 8) | (tos & 0xff));
 510         if (ip_dont_fragment(sk, &rt->dst) && !skb->ignore_df)
 511                 iph->frag_off = htons(IP_DF);
 512         else
 513                 iph->frag_off = 0;
 514         iph->ttl      = ip_select_ttl(inet, &rt->dst);
 515         iph->protocol = sk->sk_protocol;
 516         ip_copy_addrs(iph, fl4);
 517 
 518         /* Transport layer set skb->h.foo itself. */
 519 
 520         if (inet_opt && inet_opt->opt.optlen) {
 521                 iph->ihl += inet_opt->opt.optlen >> 2;
 522                 ip_options_build(skb, &inet_opt->opt, inet->inet_daddr, rt, 0);
 523         }
 524 
 525         ip_select_ident_segs(net, skb, sk,
 526                              skb_shinfo(skb)->gso_segs ?: 1);
 527 
 528         /* TODO : should we use skb->sk here instead of sk ? */
 529         skb->priority = sk->sk_priority;
 530         skb->mark = sk->sk_mark;
 531 
 532         res = ip_local_out(net, sk, skb);
 533         rcu_read_unlock();
 534         return res;
 535 
 536 no_route:
 537         rcu_read_unlock();
 538         IP_INC_STATS(net, IPSTATS_MIB_OUTNOROUTES);
 539         kfree_skb(skb);
 540         return -EHOSTUNREACH;
 541 }
 542 EXPORT_SYMBOL(__ip_queue_xmit);
 543 
 544 static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
 545 {
 546         to->pkt_type = from->pkt_type;
 547         to->priority = from->priority;
 548         to->protocol = from->protocol;
 549         to->skb_iif = from->skb_iif;
 550         skb_dst_drop(to);
 551         skb_dst_copy(to, from);
 552         to->dev = from->dev;
 553         to->mark = from->mark;
 554 
 555         skb_copy_hash(to, from);
 556 
 557 #ifdef CONFIG_NET_SCHED
 558         to->tc_index = from->tc_index;
 559 #endif
 560         nf_copy(to, from);
 561         skb_ext_copy(to, from);
 562 #if IS_ENABLED(CONFIG_IP_VS)
 563         to->ipvs_property = from->ipvs_property;
 564 #endif
 565         skb_copy_secmark(to, from);
 566 }
 567 
 568 static int ip_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
 569                        unsigned int mtu,
 570                        int (*output)(struct net *, struct sock *, struct sk_buff *))
 571 {
 572         struct iphdr *iph = ip_hdr(skb);
 573 
 574         if ((iph->frag_off & htons(IP_DF)) == 0)
 575                 return ip_do_fragment(net, sk, skb, output);
 576 
 577         if (unlikely(!skb->ignore_df ||
 578                      (IPCB(skb)->frag_max_size &&
 579                       IPCB(skb)->frag_max_size > mtu))) {
 580                 IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
 581                 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
 582                           htonl(mtu));
 583                 kfree_skb(skb);
 584                 return -EMSGSIZE;
 585         }
 586 
 587         return ip_do_fragment(net, sk, skb, output);
 588 }
 589 
 590 void ip_fraglist_init(struct sk_buff *skb, struct iphdr *iph,
 591                       unsigned int hlen, struct ip_fraglist_iter *iter)
 592 {
 593         unsigned int first_len = skb_pagelen(skb);
 594 
 595         iter->frag = skb_shinfo(skb)->frag_list;
 596         skb_frag_list_init(skb);
 597 
 598         iter->offset = 0;
 599         iter->iph = iph;
 600         iter->hlen = hlen;
 601 
 602         skb->data_len = first_len - skb_headlen(skb);
 603         skb->len = first_len;
 604         iph->tot_len = htons(first_len);
 605         iph->frag_off = htons(IP_MF);
 606         ip_send_check(iph);
 607 }
 608 EXPORT_SYMBOL(ip_fraglist_init);
 609 
 610 static void ip_fraglist_ipcb_prepare(struct sk_buff *skb,
 611                                      struct ip_fraglist_iter *iter)
 612 {
 613         struct sk_buff *to = iter->frag;
 614 
 615         /* Copy the flags to each fragment. */
 616         IPCB(to)->flags = IPCB(skb)->flags;
 617 
 618         if (iter->offset == 0)
 619                 ip_options_fragment(to);
 620 }
 621 
 622 void ip_fraglist_prepare(struct sk_buff *skb, struct ip_fraglist_iter *iter)
 623 {
 624         unsigned int hlen = iter->hlen;
 625         struct iphdr *iph = iter->iph;
 626         struct sk_buff *frag;
 627 
 628         frag = iter->frag;
 629         frag->ip_summed = CHECKSUM_NONE;
 630         skb_reset_transport_header(frag);
 631         __skb_push(frag, hlen);
 632         skb_reset_network_header(frag);
 633         memcpy(skb_network_header(frag), iph, hlen);
 634         iter->iph = ip_hdr(frag);
 635         iph = iter->iph;
 636         iph->tot_len = htons(frag->len);
 637         ip_copy_metadata(frag, skb);
 638         iter->offset += skb->len - hlen;
 639         iph->frag_off = htons(iter->offset >> 3);
 640         if (frag->next)
 641                 iph->frag_off |= htons(IP_MF);
 642         /* Ready, complete checksum */
 643         ip_send_check(iph);
 644 }
 645 EXPORT_SYMBOL(ip_fraglist_prepare);
 646 
 647 void ip_frag_init(struct sk_buff *skb, unsigned int hlen,
 648                   unsigned int ll_rs, unsigned int mtu, bool DF,
 649                   struct ip_frag_state *state)
 650 {
 651         struct iphdr *iph = ip_hdr(skb);
 652 
 653         state->DF = DF;
 654         state->hlen = hlen;
 655         state->ll_rs = ll_rs;
 656         state->mtu = mtu;
 657 
 658         state->left = skb->len - hlen;  /* Space per frame */
 659         state->ptr = hlen;              /* Where to start from */
 660 
 661         state->offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3;
 662         state->not_last_frag = iph->frag_off & htons(IP_MF);
 663 }
 664 EXPORT_SYMBOL(ip_frag_init);
 665 
 666 static void ip_frag_ipcb(struct sk_buff *from, struct sk_buff *to,
 667                          bool first_frag, struct ip_frag_state *state)
 668 {
 669         /* Copy the flags to each fragment. */
 670         IPCB(to)->flags = IPCB(from)->flags;
 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 (first_frag)
 679                 ip_options_fragment(from);
 680 }
 681 
 682 struct sk_buff *ip_frag_next(struct sk_buff *skb, struct ip_frag_state *state)
 683 {
 684         unsigned int len = state->left;
 685         struct sk_buff *skb2;
 686         struct iphdr *iph;
 687 
 688         len = state->left;
 689         /* IF: it doesn't fit, use 'mtu' - the data space left */
 690         if (len > state->mtu)
 691                 len = state->mtu;
 692         /* IF: we are not sending up to and including the packet end
 693            then align the next start on an eight byte boundary */
 694         if (len < state->left)  {
 695                 len &= ~7;
 696         }
 697 
 698         /* Allocate buffer */
 699         skb2 = alloc_skb(len + state->hlen + state->ll_rs, GFP_ATOMIC);
 700         if (!skb2)
 701                 return ERR_PTR(-ENOMEM);
 702 
 703         /*
 704          *      Set up data on packet
 705          */
 706 
 707         ip_copy_metadata(skb2, skb);
 708         skb_reserve(skb2, state->ll_rs);
 709         skb_put(skb2, len + state->hlen);
 710         skb_reset_network_header(skb2);
 711         skb2->transport_header = skb2->network_header + state->hlen;
 712 
 713         /*
 714          *      Charge the memory for the fragment to any owner
 715          *      it might possess
 716          */
 717 
 718         if (skb->sk)
 719                 skb_set_owner_w(skb2, skb->sk);
 720 
 721         /*
 722          *      Copy the packet header into the new buffer.
 723          */
 724 
 725         skb_copy_from_linear_data(skb, skb_network_header(skb2), state->hlen);
 726 
 727         /*
 728          *      Copy a block of the IP datagram.
 729          */
 730         if (skb_copy_bits(skb, state->ptr, skb_transport_header(skb2), len))
 731                 BUG();
 732         state->left -= len;
 733 
 734         /*
 735          *      Fill in the new header fields.
 736          */
 737         iph = ip_hdr(skb2);
 738         iph->frag_off = htons((state->offset >> 3));
 739         if (state->DF)
 740                 iph->frag_off |= htons(IP_DF);
 741 
 742         /*
 743          *      Added AC : If we are fragmenting a fragment that's not the
 744          *                 last fragment then keep MF on each bit
 745          */
 746         if (state->left > 0 || state->not_last_frag)
 747                 iph->frag_off |= htons(IP_MF);
 748         state->ptr += len;
 749         state->offset += len;
 750 
 751         iph->tot_len = htons(len + state->hlen);
 752 
 753         ip_send_check(iph);
 754 
 755         return skb2;
 756 }
 757 EXPORT_SYMBOL(ip_frag_next);
 758 
 759 /*
 760  *      This IP datagram is too large to be sent in one piece.  Break it up into
 761  *      smaller pieces (each of size equal to IP header plus
 762  *      a block of the data of the original IP data part) that will yet fit in a
 763  *      single device frame, and queue such a frame for sending.
 764  */
 765 
 766 int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
 767                    int (*output)(struct net *, struct sock *, struct sk_buff *))
 768 {
 769         struct iphdr *iph;
 770         struct sk_buff *skb2;
 771         struct rtable *rt = skb_rtable(skb);
 772         unsigned int mtu, hlen, ll_rs;
 773         struct ip_fraglist_iter iter;
 774         ktime_t tstamp = skb->tstamp;
 775         struct ip_frag_state state;
 776         int err = 0;
 777 
 778         /* for offloaded checksums cleanup checksum before fragmentation */
 779         if (skb->ip_summed == CHECKSUM_PARTIAL &&
 780             (err = skb_checksum_help(skb)))
 781                 goto fail;
 782 
 783         /*
 784          *      Point into the IP datagram header.
 785          */
 786 
 787         iph = ip_hdr(skb);
 788 
 789         mtu = ip_skb_dst_mtu(sk, skb);
 790         if (IPCB(skb)->frag_max_size && IPCB(skb)->frag_max_size < mtu)
 791                 mtu = IPCB(skb)->frag_max_size;
 792 
 793         /*
 794          *      Setup starting values.
 795          */
 796 
 797         hlen = iph->ihl * 4;
 798         mtu = mtu - hlen;       /* Size of data space */
 799         IPCB(skb)->flags |= IPSKB_FRAG_COMPLETE;
 800         ll_rs = LL_RESERVED_SPACE(rt->dst.dev);
 801 
 802         /* When frag_list is given, use it. First, check its validity:
 803          * some transformers could create wrong frag_list or break existing
 804          * one, it is not prohibited. In this case fall back to copying.
 805          *
 806          * LATER: this step can be merged to real generation of fragments,
 807          * we can switch to copy when see the first bad fragment.
 808          */
 809         if (skb_has_frag_list(skb)) {
 810                 struct sk_buff *frag, *frag2;
 811                 unsigned int first_len = skb_pagelen(skb);
 812 
 813                 if (first_len - hlen > mtu ||
 814                     ((first_len - hlen) & 7) ||
 815                     ip_is_fragment(iph) ||
 816                     skb_cloned(skb) ||
 817                     skb_headroom(skb) < ll_rs)
 818                         goto slow_path;
 819 
 820                 skb_walk_frags(skb, frag) {
 821                         /* Correct geometry. */
 822                         if (frag->len > mtu ||
 823                             ((frag->len & 7) && frag->next) ||
 824                             skb_headroom(frag) < hlen + ll_rs)
 825                                 goto slow_path_clean;
 826 
 827                         /* Partially cloned skb? */
 828                         if (skb_shared(frag))
 829                                 goto slow_path_clean;
 830 
 831                         BUG_ON(frag->sk);
 832                         if (skb->sk) {
 833                                 frag->sk = skb->sk;
 834                                 frag->destructor = sock_wfree;
 835                         }
 836                         skb->truesize -= frag->truesize;
 837                 }
 838 
 839                 /* Everything is OK. Generate! */
 840                 ip_fraglist_init(skb, iph, hlen, &iter);
 841 
 842                 for (;;) {
 843                         /* Prepare header of the next frame,
 844                          * before previous one went down. */
 845                         if (iter.frag) {
 846                                 ip_fraglist_ipcb_prepare(skb, &iter);
 847                                 ip_fraglist_prepare(skb, &iter);
 848                         }
 849 
 850                         skb->tstamp = tstamp;
 851                         err = output(net, sk, skb);
 852 
 853                         if (!err)
 854                                 IP_INC_STATS(net, IPSTATS_MIB_FRAGCREATES);
 855                         if (err || !iter.frag)
 856                                 break;
 857 
 858                         skb = ip_fraglist_next(&iter);
 859                 }
 860 
 861                 if (err == 0) {
 862                         IP_INC_STATS(net, IPSTATS_MIB_FRAGOKS);
 863                         return 0;
 864                 }
 865 
 866                 kfree_skb_list(iter.frag);
 867 
 868                 IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
 869                 return err;
 870 
 871 slow_path_clean:
 872                 skb_walk_frags(skb, frag2) {
 873                         if (frag2 == frag)
 874                                 break;
 875                         frag2->sk = NULL;
 876                         frag2->destructor = NULL;
 877                         skb->truesize += frag2->truesize;
 878                 }
 879         }
 880 
 881 slow_path:
 882         /*
 883          *      Fragment the datagram.
 884          */
 885 
 886         ip_frag_init(skb, hlen, ll_rs, mtu, IPCB(skb)->flags & IPSKB_FRAG_PMTU,
 887                      &state);
 888 
 889         /*
 890          *      Keep copying data until we run out.
 891          */
 892 
 893         while (state.left > 0) {
 894                 bool first_frag = (state.offset == 0);
 895 
 896                 skb2 = ip_frag_next(skb, &state);
 897                 if (IS_ERR(skb2)) {
 898                         err = PTR_ERR(skb2);
 899                         goto fail;
 900                 }
 901                 ip_frag_ipcb(skb, skb2, first_frag, &state);
 902 
 903                 /*
 904                  *      Put this fragment into the sending queue.
 905                  */
 906                 skb2->tstamp = tstamp;
 907                 err = output(net, sk, skb2);
 908                 if (err)
 909                         goto fail;
 910 
 911                 IP_INC_STATS(net, IPSTATS_MIB_FRAGCREATES);
 912         }
 913         consume_skb(skb);
 914         IP_INC_STATS(net, IPSTATS_MIB_FRAGOKS);
 915         return err;
 916 
 917 fail:
 918         kfree_skb(skb);
 919         IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
 920         return err;
 921 }
 922 EXPORT_SYMBOL(ip_do_fragment);
 923 
 924 int
 925 ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
 926 {
 927         struct msghdr *msg = from;
 928 
 929         if (skb->ip_summed == CHECKSUM_PARTIAL) {
 930                 if (!copy_from_iter_full(to, len, &msg->msg_iter))
 931                         return -EFAULT;
 932         } else {
 933                 __wsum csum = 0;
 934                 if (!csum_and_copy_from_iter_full(to, len, &csum, &msg->msg_iter))
 935                         return -EFAULT;
 936                 skb->csum = csum_block_add(skb->csum, csum, odd);
 937         }
 938         return 0;
 939 }
 940 EXPORT_SYMBOL(ip_generic_getfrag);
 941 
 942 static inline __wsum
 943 csum_page(struct page *page, int offset, int copy)
 944 {
 945         char *kaddr;
 946         __wsum csum;
 947         kaddr = kmap(page);
 948         csum = csum_partial(kaddr + offset, copy, 0);
 949         kunmap(page);
 950         return csum;
 951 }
 952 
 953 static int __ip_append_data(struct sock *sk,
 954                             struct flowi4 *fl4,
 955                             struct sk_buff_head *queue,
 956                             struct inet_cork *cork,
 957                             struct page_frag *pfrag,
 958                             int getfrag(void *from, char *to, int offset,
 959                                         int len, int odd, struct sk_buff *skb),
 960                             void *from, int length, int transhdrlen,
 961                             unsigned int flags)
 962 {
 963         struct inet_sock *inet = inet_sk(sk);
 964         struct ubuf_info *uarg = NULL;
 965         struct sk_buff *skb;
 966 
 967         struct ip_options *opt = cork->opt;
 968         int hh_len;
 969         int exthdrlen;
 970         int mtu;
 971         int copy;
 972         int err;
 973         int offset = 0;
 974         unsigned int maxfraglen, fragheaderlen, maxnonfragsize;
 975         int csummode = CHECKSUM_NONE;
 976         struct rtable *rt = (struct rtable *)cork->dst;
 977         unsigned int wmem_alloc_delta = 0;
 978         bool paged, extra_uref = false;
 979         u32 tskey = 0;
 980 
 981         skb = skb_peek_tail(queue);
 982 
 983         exthdrlen = !skb ? rt->dst.header_len : 0;
 984         mtu = cork->gso_size ? IP_MAX_MTU : cork->fragsize;
 985         paged = !!cork->gso_size;
 986 
 987         if (cork->tx_flags & SKBTX_ANY_SW_TSTAMP &&
 988             sk->sk_tsflags & SOF_TIMESTAMPING_OPT_ID)
 989                 tskey = sk->sk_tskey++;
 990 
 991         hh_len = LL_RESERVED_SPACE(rt->dst.dev);
 992 
 993         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
 994         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
 995         maxnonfragsize = ip_sk_ignore_df(sk) ? 0xFFFF : mtu;
 996 
 997         if (cork->length + length > maxnonfragsize - fragheaderlen) {
 998                 ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
 999                                mtu - (opt ? opt->optlen : 0));
1000                 return -EMSGSIZE;
1001         }
1002 
1003         /*
1004          * transhdrlen > 0 means that this is the first fragment and we wish
1005          * it won't be fragmented in the future.
1006          */
1007         if (transhdrlen &&
1008             length + fragheaderlen <= mtu &&
1009             rt->dst.dev->features & (NETIF_F_HW_CSUM | NETIF_F_IP_CSUM) &&
1010             (!(flags & MSG_MORE) || cork->gso_size) &&
1011             (!exthdrlen || (rt->dst.dev->features & NETIF_F_HW_ESP_TX_CSUM)))
1012                 csummode = CHECKSUM_PARTIAL;
1013 
1014         if (flags & MSG_ZEROCOPY && length && sock_flag(sk, SOCK_ZEROCOPY)) {
1015                 uarg = sock_zerocopy_realloc(sk, length, skb_zcopy(skb));
1016                 if (!uarg)
1017                         return -ENOBUFS;
1018                 extra_uref = !skb_zcopy(skb);   /* only ref on new uarg */
1019                 if (rt->dst.dev->features & NETIF_F_SG &&
1020                     csummode == CHECKSUM_PARTIAL) {
1021                         paged = true;
1022                 } else {
1023                         uarg->zerocopy = 0;
1024                         skb_zcopy_set(skb, uarg, &extra_uref);
1025                 }
1026         }
1027 
1028         cork->length += length;
1029 
1030         /* So, what's going on in the loop below?
1031          *
1032          * We use calculated fragment length to generate chained skb,
1033          * each of segments is IP fragment ready for sending to network after
1034          * adding appropriate IP header.
1035          */
1036 
1037         if (!skb)
1038                 goto alloc_new_skb;
1039 
1040         while (length > 0) {
1041                 /* Check if the remaining data fits into current packet. */
1042                 copy = mtu - skb->len;
1043                 if (copy < length)
1044                         copy = maxfraglen - skb->len;
1045                 if (copy <= 0) {
1046                         char *data;
1047                         unsigned int datalen;
1048                         unsigned int fraglen;
1049                         unsigned int fraggap;
1050                         unsigned int alloclen;
1051                         unsigned int pagedlen;
1052                         struct sk_buff *skb_prev;
1053 alloc_new_skb:
1054                         skb_prev = skb;
1055                         if (skb_prev)
1056                                 fraggap = skb_prev->len - maxfraglen;
1057                         else
1058                                 fraggap = 0;
1059 
1060                         /*
1061                          * If remaining data exceeds the mtu,
1062                          * we know we need more fragment(s).
1063                          */
1064                         datalen = length + fraggap;
1065                         if (datalen > mtu - fragheaderlen)
1066                                 datalen = maxfraglen - fragheaderlen;
1067                         fraglen = datalen + fragheaderlen;
1068                         pagedlen = 0;
1069 
1070                         if ((flags & MSG_MORE) &&
1071                             !(rt->dst.dev->features&NETIF_F_SG))
1072                                 alloclen = mtu;
1073                         else if (!paged)
1074                                 alloclen = fraglen;
1075                         else {
1076                                 alloclen = min_t(int, fraglen, MAX_HEADER);
1077                                 pagedlen = fraglen - alloclen;
1078                         }
1079 
1080                         alloclen += exthdrlen;
1081 
1082                         /* The last fragment gets additional space at tail.
1083                          * Note, with MSG_MORE we overallocate on fragments,
1084                          * because we have no idea what fragment will be
1085                          * the last.
1086                          */
1087                         if (datalen == length + fraggap)
1088                                 alloclen += rt->dst.trailer_len;
1089 
1090                         if (transhdrlen) {
1091                                 skb = sock_alloc_send_skb(sk,
1092                                                 alloclen + hh_len + 15,
1093                                                 (flags & MSG_DONTWAIT), &err);
1094                         } else {
1095                                 skb = NULL;
1096                                 if (refcount_read(&sk->sk_wmem_alloc) + wmem_alloc_delta <=
1097                                     2 * sk->sk_sndbuf)
1098                                         skb = alloc_skb(alloclen + hh_len + 15,
1099                                                         sk->sk_allocation);
1100                                 if (unlikely(!skb))
1101                                         err = -ENOBUFS;
1102                         }
1103                         if (!skb)
1104                                 goto error;
1105 
1106                         /*
1107                          *      Fill in the control structures
1108                          */
1109                         skb->ip_summed = csummode;
1110                         skb->csum = 0;
1111                         skb_reserve(skb, hh_len);
1112 
1113                         /*
1114                          *      Find where to start putting bytes.
1115                          */
1116                         data = skb_put(skb, fraglen + exthdrlen - pagedlen);
1117                         skb_set_network_header(skb, exthdrlen);
1118                         skb->transport_header = (skb->network_header +
1119                                                  fragheaderlen);
1120                         data += fragheaderlen + exthdrlen;
1121 
1122                         if (fraggap) {
1123                                 skb->csum = skb_copy_and_csum_bits(
1124                                         skb_prev, maxfraglen,
1125                                         data + transhdrlen, fraggap, 0);
1126                                 skb_prev->csum = csum_sub(skb_prev->csum,
1127                                                           skb->csum);
1128                                 data += fraggap;
1129                                 pskb_trim_unique(skb_prev, maxfraglen);
1130                         }
1131 
1132                         copy = datalen - transhdrlen - fraggap - pagedlen;
1133                         if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
1134                                 err = -EFAULT;
1135                                 kfree_skb(skb);
1136                                 goto error;
1137                         }
1138 
1139                         offset += copy;
1140                         length -= copy + transhdrlen;
1141                         transhdrlen = 0;
1142                         exthdrlen = 0;
1143                         csummode = CHECKSUM_NONE;
1144 
1145                         /* only the initial fragment is time stamped */
1146                         skb_shinfo(skb)->tx_flags = cork->tx_flags;
1147                         cork->tx_flags = 0;
1148                         skb_shinfo(skb)->tskey = tskey;
1149                         tskey = 0;
1150                         skb_zcopy_set(skb, uarg, &extra_uref);
1151 
1152                         if ((flags & MSG_CONFIRM) && !skb_prev)
1153                                 skb_set_dst_pending_confirm(skb, 1);
1154 
1155                         /*
1156                          * Put the packet on the pending queue.
1157                          */
1158                         if (!skb->destructor) {
1159                                 skb->destructor = sock_wfree;
1160                                 skb->sk = sk;
1161                                 wmem_alloc_delta += skb->truesize;
1162                         }
1163                         __skb_queue_tail(queue, skb);
1164                         continue;
1165                 }
1166 
1167                 if (copy > length)
1168                         copy = length;
1169 
1170                 if (!(rt->dst.dev->features&NETIF_F_SG) &&
1171                     skb_tailroom(skb) >= copy) {
1172                         unsigned int off;
1173 
1174                         off = skb->len;
1175                         if (getfrag(from, skb_put(skb, copy),
1176                                         offset, copy, off, skb) < 0) {
1177                                 __skb_trim(skb, off);
1178                                 err = -EFAULT;
1179                                 goto error;
1180                         }
1181                 } else if (!uarg || !uarg->zerocopy) {
1182                         int i = skb_shinfo(skb)->nr_frags;
1183 
1184                         err = -ENOMEM;
1185                         if (!sk_page_frag_refill(sk, pfrag))
1186                                 goto error;
1187 
1188                         if (!skb_can_coalesce(skb, i, pfrag->page,
1189                                               pfrag->offset)) {
1190                                 err = -EMSGSIZE;
1191                                 if (i == MAX_SKB_FRAGS)
1192                                         goto error;
1193 
1194                                 __skb_fill_page_desc(skb, i, pfrag->page,
1195                                                      pfrag->offset, 0);
1196                                 skb_shinfo(skb)->nr_frags = ++i;
1197                                 get_page(pfrag->page);
1198                         }
1199                         copy = min_t(int, copy, pfrag->size - pfrag->offset);
1200                         if (getfrag(from,
1201                                     page_address(pfrag->page) + pfrag->offset,
1202                                     offset, copy, skb->len, skb) < 0)
1203                                 goto error_efault;
1204 
1205                         pfrag->offset += copy;
1206                         skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
1207                         skb->len += copy;
1208                         skb->data_len += copy;
1209                         skb->truesize += copy;
1210                         wmem_alloc_delta += copy;
1211                 } else {
1212                         err = skb_zerocopy_iter_dgram(skb, from, copy);
1213                         if (err < 0)
1214                                 goto error;
1215                 }
1216                 offset += copy;
1217                 length -= copy;
1218         }
1219 
1220         if (wmem_alloc_delta)
1221                 refcount_add(wmem_alloc_delta, &sk->sk_wmem_alloc);
1222         return 0;
1223 
1224 error_efault:
1225         err = -EFAULT;
1226 error:
1227         if (uarg)
1228                 sock_zerocopy_put_abort(uarg, extra_uref);
1229         cork->length -= length;
1230         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1231         refcount_add(wmem_alloc_delta, &sk->sk_wmem_alloc);
1232         return err;
1233 }
1234 
1235 static int ip_setup_cork(struct sock *sk, struct inet_cork *cork,
1236                          struct ipcm_cookie *ipc, struct rtable **rtp)
1237 {
1238         struct ip_options_rcu *opt;
1239         struct rtable *rt;
1240 
1241         rt = *rtp;
1242         if (unlikely(!rt))
1243                 return -EFAULT;
1244 
1245         /*
1246          * setup for corking.
1247          */
1248         opt = ipc->opt;
1249         if (opt) {
1250                 if (!cork->opt) {
1251                         cork->opt = kmalloc(sizeof(struct ip_options) + 40,
1252                                             sk->sk_allocation);
1253                         if (unlikely(!cork->opt))
1254                                 return -ENOBUFS;
1255                 }
1256                 memcpy(cork->opt, &opt->opt, sizeof(struct ip_options) + opt->opt.optlen);
1257                 cork->flags |= IPCORK_OPT;
1258                 cork->addr = ipc->addr;
1259         }
1260 
1261         cork->fragsize = ip_sk_use_pmtu(sk) ?
1262                          dst_mtu(&rt->dst) : READ_ONCE(rt->dst.dev->mtu);
1263 
1264         if (!inetdev_valid_mtu(cork->fragsize))
1265                 return -ENETUNREACH;
1266 
1267         cork->gso_size = ipc->gso_size;
1268 
1269         cork->dst = &rt->dst;
1270         /* We stole this route, caller should not release it. */
1271         *rtp = NULL;
1272 
1273         cork->length = 0;
1274         cork->ttl = ipc->ttl;
1275         cork->tos = ipc->tos;
1276         cork->mark = ipc->sockc.mark;
1277         cork->priority = ipc->priority;
1278         cork->transmit_time = ipc->sockc.transmit_time;
1279         cork->tx_flags = 0;
1280         sock_tx_timestamp(sk, ipc->sockc.tsflags, &cork->tx_flags);
1281 
1282         return 0;
1283 }
1284 
1285 /*
1286  *      ip_append_data() and ip_append_page() can make one large IP datagram
1287  *      from many pieces of data. Each pieces will be holded on the socket
1288  *      until ip_push_pending_frames() is called. Each piece can be a page
1289  *      or non-page data.
1290  *
1291  *      Not only UDP, other transport protocols - e.g. raw sockets - can use
1292  *      this interface potentially.
1293  *
1294  *      LATER: length must be adjusted by pad at tail, when it is required.
1295  */
1296 int ip_append_data(struct sock *sk, struct flowi4 *fl4,
1297                    int getfrag(void *from, char *to, int offset, int len,
1298                                int odd, struct sk_buff *skb),
1299                    void *from, int length, int transhdrlen,
1300                    struct ipcm_cookie *ipc, struct rtable **rtp,
1301                    unsigned int flags)
1302 {
1303         struct inet_sock *inet = inet_sk(sk);
1304         int err;
1305 
1306         if (flags&MSG_PROBE)
1307                 return 0;
1308 
1309         if (skb_queue_empty(&sk->sk_write_queue)) {
1310                 err = ip_setup_cork(sk, &inet->cork.base, ipc, rtp);
1311                 if (err)
1312                         return err;
1313         } else {
1314                 transhdrlen = 0;
1315         }
1316 
1317         return __ip_append_data(sk, fl4, &sk->sk_write_queue, &inet->cork.base,
1318                                 sk_page_frag(sk), getfrag,
1319                                 from, length, transhdrlen, flags);
1320 }
1321 
1322 ssize_t ip_append_page(struct sock *sk, struct flowi4 *fl4, struct page *page,
1323                        int offset, size_t size, int flags)
1324 {
1325         struct inet_sock *inet = inet_sk(sk);
1326         struct sk_buff *skb;
1327         struct rtable *rt;
1328         struct ip_options *opt = NULL;
1329         struct inet_cork *cork;
1330         int hh_len;
1331         int mtu;
1332         int len;
1333         int err;
1334         unsigned int maxfraglen, fragheaderlen, fraggap, maxnonfragsize;
1335 
1336         if (inet->hdrincl)
1337                 return -EPERM;
1338 
1339         if (flags&MSG_PROBE)
1340                 return 0;
1341 
1342         if (skb_queue_empty(&sk->sk_write_queue))
1343                 return -EINVAL;
1344 
1345         cork = &inet->cork.base;
1346         rt = (struct rtable *)cork->dst;
1347         if (cork->flags & IPCORK_OPT)
1348                 opt = cork->opt;
1349 
1350         if (!(rt->dst.dev->features&NETIF_F_SG))
1351                 return -EOPNOTSUPP;
1352 
1353         hh_len = LL_RESERVED_SPACE(rt->dst.dev);
1354         mtu = cork->gso_size ? IP_MAX_MTU : cork->fragsize;
1355 
1356         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
1357         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
1358         maxnonfragsize = ip_sk_ignore_df(sk) ? 0xFFFF : mtu;
1359 
1360         if (cork->length + size > maxnonfragsize - fragheaderlen) {
1361                 ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
1362                                mtu - (opt ? opt->optlen : 0));
1363                 return -EMSGSIZE;
1364         }
1365 
1366         skb = skb_peek_tail(&sk->sk_write_queue);
1367         if (!skb)
1368                 return -EINVAL;
1369 
1370         cork->length += size;
1371 
1372         while (size > 0) {
1373                 /* Check if the remaining data fits into current packet. */
1374                 len = mtu - skb->len;
1375                 if (len < size)
1376                         len = maxfraglen - skb->len;
1377 
1378                 if (len <= 0) {
1379                         struct sk_buff *skb_prev;
1380                         int alloclen;
1381 
1382                         skb_prev = skb;
1383                         fraggap = skb_prev->len - maxfraglen;
1384 
1385                         alloclen = fragheaderlen + hh_len + fraggap + 15;
1386                         skb = sock_wmalloc(sk, alloclen, 1, sk->sk_allocation);
1387                         if (unlikely(!skb)) {
1388                                 err = -ENOBUFS;
1389                                 goto error;
1390                         }
1391 
1392                         /*
1393                          *      Fill in the control structures
1394                          */
1395                         skb->ip_summed = CHECKSUM_NONE;
1396                         skb->csum = 0;
1397                         skb_reserve(skb, hh_len);
1398 
1399                         /*
1400                          *      Find where to start putting bytes.
1401                          */
1402                         skb_put(skb, fragheaderlen + fraggap);
1403                         skb_reset_network_header(skb);
1404                         skb->transport_header = (skb->network_header +
1405                                                  fragheaderlen);
1406                         if (fraggap) {
1407                                 skb->csum = skb_copy_and_csum_bits(skb_prev,
1408                                                                    maxfraglen,
1409                                                     skb_transport_header(skb),
1410                                                                    fraggap, 0);
1411                                 skb_prev->csum = csum_sub(skb_prev->csum,
1412                                                           skb->csum);
1413                                 pskb_trim_unique(skb_prev, maxfraglen);
1414                         }
1415 
1416                         /*
1417                          * Put the packet on the pending queue.
1418                          */
1419                         __skb_queue_tail(&sk->sk_write_queue, skb);
1420                         continue;
1421                 }
1422 
1423                 if (len > size)
1424                         len = size;
1425 
1426                 if (skb_append_pagefrags(skb, page, offset, len)) {
1427                         err = -EMSGSIZE;
1428                         goto error;
1429                 }
1430 
1431                 if (skb->ip_summed == CHECKSUM_NONE) {
1432                         __wsum csum;
1433                         csum = csum_page(page, offset, len);
1434                         skb->csum = csum_block_add(skb->csum, csum, skb->len);
1435                 }
1436 
1437                 skb->len += len;
1438                 skb->data_len += len;
1439                 skb->truesize += len;
1440                 refcount_add(len, &sk->sk_wmem_alloc);
1441                 offset += len;
1442                 size -= len;
1443         }
1444         return 0;
1445 
1446 error:
1447         cork->length -= size;
1448         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1449         return err;
1450 }
1451 
1452 static void ip_cork_release(struct inet_cork *cork)
1453 {
1454         cork->flags &= ~IPCORK_OPT;
1455         kfree(cork->opt);
1456         cork->opt = NULL;
1457         dst_release(cork->dst);
1458         cork->dst = NULL;
1459 }
1460 
1461 /*
1462  *      Combined all pending IP fragments on the socket as one IP datagram
1463  *      and push them out.
1464  */
1465 struct sk_buff *__ip_make_skb(struct sock *sk,
1466                               struct flowi4 *fl4,
1467                               struct sk_buff_head *queue,
1468                               struct inet_cork *cork)
1469 {
1470         struct sk_buff *skb, *tmp_skb;
1471         struct sk_buff **tail_skb;
1472         struct inet_sock *inet = inet_sk(sk);
1473         struct net *net = sock_net(sk);
1474         struct ip_options *opt = NULL;
1475         struct rtable *rt = (struct rtable *)cork->dst;
1476         struct iphdr *iph;
1477         __be16 df = 0;
1478         __u8 ttl;
1479 
1480         skb = __skb_dequeue(queue);
1481         if (!skb)
1482                 goto out;
1483         tail_skb = &(skb_shinfo(skb)->frag_list);
1484 
1485         /* move skb->data to ip header from ext header */
1486         if (skb->data < skb_network_header(skb))
1487                 __skb_pull(skb, skb_network_offset(skb));
1488         while ((tmp_skb = __skb_dequeue(queue)) != NULL) {
1489                 __skb_pull(tmp_skb, skb_network_header_len(skb));
1490                 *tail_skb = tmp_skb;
1491                 tail_skb = &(tmp_skb->next);
1492                 skb->len += tmp_skb->len;
1493                 skb->data_len += tmp_skb->len;
1494                 skb->truesize += tmp_skb->truesize;
1495                 tmp_skb->destructor = NULL;
1496                 tmp_skb->sk = NULL;
1497         }
1498 
1499         /* Unless user demanded real pmtu discovery (IP_PMTUDISC_DO), we allow
1500          * to fragment the frame generated here. No matter, what transforms
1501          * how transforms change size of the packet, it will come out.
1502          */
1503         skb->ignore_df = ip_sk_ignore_df(sk);
1504 
1505         /* DF bit is set when we want to see DF on outgoing frames.
1506          * If ignore_df is set too, we still allow to fragment this frame
1507          * locally. */
1508         if (inet->pmtudisc == IP_PMTUDISC_DO ||
1509             inet->pmtudisc == IP_PMTUDISC_PROBE ||
1510             (skb->len <= dst_mtu(&rt->dst) &&
1511              ip_dont_fragment(sk, &rt->dst)))
1512                 df = htons(IP_DF);
1513 
1514         if (cork->flags & IPCORK_OPT)
1515                 opt = cork->opt;
1516 
1517         if (cork->ttl != 0)
1518                 ttl = cork->ttl;
1519         else if (rt->rt_type == RTN_MULTICAST)
1520                 ttl = inet->mc_ttl;
1521         else
1522                 ttl = ip_select_ttl(inet, &rt->dst);
1523 
1524         iph = ip_hdr(skb);
1525         iph->version = 4;
1526         iph->ihl = 5;
1527         iph->tos = (cork->tos != -1) ? cork->tos : inet->tos;
1528         iph->frag_off = df;
1529         iph->ttl = ttl;
1530         iph->protocol = sk->sk_protocol;
1531         ip_copy_addrs(iph, fl4);
1532         ip_select_ident(net, skb, sk);
1533 
1534         if (opt) {
1535                 iph->ihl += opt->optlen>>2;
1536                 ip_options_build(skb, opt, cork->addr, rt, 0);
1537         }
1538 
1539         skb->priority = (cork->tos != -1) ? cork->priority: sk->sk_priority;
1540         skb->mark = cork->mark;
1541         skb->tstamp = cork->transmit_time;
1542         /*
1543          * Steal rt from cork.dst to avoid a pair of atomic_inc/atomic_dec
1544          * on dst refcount
1545          */
1546         cork->dst = NULL;
1547         skb_dst_set(skb, &rt->dst);
1548 
1549         if (iph->protocol == IPPROTO_ICMP)
1550                 icmp_out_count(net, ((struct icmphdr *)
1551                         skb_transport_header(skb))->type);
1552 
1553         ip_cork_release(cork);
1554 out:
1555         return skb;
1556 }
1557 
1558 int ip_send_skb(struct net *net, struct sk_buff *skb)
1559 {
1560         int err;
1561 
1562         err = ip_local_out(net, skb->sk, skb);
1563         if (err) {
1564                 if (err > 0)
1565                         err = net_xmit_errno(err);
1566                 if (err)
1567                         IP_INC_STATS(net, IPSTATS_MIB_OUTDISCARDS);
1568         }
1569 
1570         return err;
1571 }
1572 
1573 int ip_push_pending_frames(struct sock *sk, struct flowi4 *fl4)
1574 {
1575         struct sk_buff *skb;
1576 
1577         skb = ip_finish_skb(sk, fl4);
1578         if (!skb)
1579                 return 0;
1580 
1581         /* Netfilter gets whole the not fragmented skb. */
1582         return ip_send_skb(sock_net(sk), skb);
1583 }
1584 
1585 /*
1586  *      Throw away all pending data on the socket.
1587  */
1588 static void __ip_flush_pending_frames(struct sock *sk,
1589                                       struct sk_buff_head *queue,
1590                                       struct inet_cork *cork)
1591 {
1592         struct sk_buff *skb;
1593 
1594         while ((skb = __skb_dequeue_tail(queue)) != NULL)
1595                 kfree_skb(skb);
1596 
1597         ip_cork_release(cork);
1598 }
1599 
1600 void ip_flush_pending_frames(struct sock *sk)
1601 {
1602         __ip_flush_pending_frames(sk, &sk->sk_write_queue, &inet_sk(sk)->cork.base);
1603 }
1604 
1605 struct sk_buff *ip_make_skb(struct sock *sk,
1606                             struct flowi4 *fl4,
1607                             int getfrag(void *from, char *to, int offset,
1608                                         int len, int odd, struct sk_buff *skb),
1609                             void *from, int length, int transhdrlen,
1610                             struct ipcm_cookie *ipc, struct rtable **rtp,
1611                             struct inet_cork *cork, unsigned int flags)
1612 {
1613         struct sk_buff_head queue;
1614         int err;
1615 
1616         if (flags & MSG_PROBE)
1617                 return NULL;
1618 
1619         __skb_queue_head_init(&queue);
1620 
1621         cork->flags = 0;
1622         cork->addr = 0;
1623         cork->opt = NULL;
1624         err = ip_setup_cork(sk, cork, ipc, rtp);
1625         if (err)
1626                 return ERR_PTR(err);
1627 
1628         err = __ip_append_data(sk, fl4, &queue, cork,
1629                                &current->task_frag, getfrag,
1630                                from, length, transhdrlen, flags);
1631         if (err) {
1632                 __ip_flush_pending_frames(sk, &queue, cork);
1633                 return ERR_PTR(err);
1634         }
1635 
1636         return __ip_make_skb(sk, fl4, &queue, cork);
1637 }
1638 
1639 /*
1640  *      Fetch data from kernel space and fill in checksum if needed.
1641  */
1642 static int ip_reply_glue_bits(void *dptr, char *to, int offset,
1643                               int len, int odd, struct sk_buff *skb)
1644 {
1645         __wsum csum;
1646 
1647         csum = csum_partial_copy_nocheck(dptr+offset, to, len, 0);
1648         skb->csum = csum_block_add(skb->csum, csum, odd);
1649         return 0;
1650 }
1651 
1652 /*
1653  *      Generic function to send a packet as reply to another packet.
1654  *      Used to send some TCP resets/acks so far.
1655  */
1656 void ip_send_unicast_reply(struct sock *sk, struct sk_buff *skb,
1657                            const struct ip_options *sopt,
1658                            __be32 daddr, __be32 saddr,
1659                            const struct ip_reply_arg *arg,
1660                            unsigned int len, u64 transmit_time)
1661 {
1662         struct ip_options_data replyopts;
1663         struct ipcm_cookie ipc;
1664         struct flowi4 fl4;
1665         struct rtable *rt = skb_rtable(skb);
1666         struct net *net = sock_net(sk);
1667         struct sk_buff *nskb;
1668         int err;
1669         int oif;
1670 
1671         if (__ip_options_echo(net, &replyopts.opt.opt, skb, sopt))
1672                 return;
1673 
1674         ipcm_init(&ipc);
1675         ipc.addr = daddr;
1676         ipc.sockc.transmit_time = transmit_time;
1677 
1678         if (replyopts.opt.opt.optlen) {
1679                 ipc.opt = &replyopts.opt;
1680 
1681                 if (replyopts.opt.opt.srr)
1682                         daddr = replyopts.opt.opt.faddr;
1683         }
1684 
1685         oif = arg->bound_dev_if;
1686         if (!oif && netif_index_is_l3_master(net, skb->skb_iif))
1687                 oif = skb->skb_iif;
1688 
1689         flowi4_init_output(&fl4, oif,
1690                            IP4_REPLY_MARK(net, skb->mark) ?: sk->sk_mark,
1691                            RT_TOS(arg->tos),
1692                            RT_SCOPE_UNIVERSE, ip_hdr(skb)->protocol,
1693                            ip_reply_arg_flowi_flags(arg),
1694                            daddr, saddr,
1695                            tcp_hdr(skb)->source, tcp_hdr(skb)->dest,
1696                            arg->uid);
1697         security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
1698         rt = ip_route_output_key(net, &fl4);
1699         if (IS_ERR(rt))
1700                 return;
1701 
1702         inet_sk(sk)->tos = arg->tos;
1703 
1704         sk->sk_protocol = ip_hdr(skb)->protocol;
1705         sk->sk_bound_dev_if = arg->bound_dev_if;
1706         sk->sk_sndbuf = sysctl_wmem_default;
1707         sk->sk_mark = fl4.flowi4_mark;
1708         err = ip_append_data(sk, &fl4, ip_reply_glue_bits, arg->iov->iov_base,
1709                              len, 0, &ipc, &rt, MSG_DONTWAIT);
1710         if (unlikely(err)) {
1711                 ip_flush_pending_frames(sk);
1712                 goto out;
1713         }
1714 
1715         nskb = skb_peek(&sk->sk_write_queue);
1716         if (nskb) {
1717                 if (arg->csumoffset >= 0)
1718                         *((__sum16 *)skb_transport_header(nskb) +
1719                           arg->csumoffset) = csum_fold(csum_add(nskb->csum,
1720                                                                 arg->csum));
1721                 nskb->ip_summed = CHECKSUM_NONE;
1722                 ip_push_pending_frames(sk, &fl4);
1723         }
1724 out:
1725         ip_rt_put(rt);
1726 }
1727 
1728 void __init ip_init(void)
1729 {
1730         ip_rt_init();
1731         inet_initpeers();
1732 
1733 #if defined(CONFIG_IP_MULTICAST)
1734         igmp_mc_init();
1735 #endif
1736 }
/* [<][>][^][v][top][bottom][index][help] */
root/net/ipv4/ip_output.c

DEFINITIONS
