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Linux/net/ipv4/ip_output.c

  1 /*
  2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
  3  *              operating system.  INET is implemented using the  BSD Socket
  4  *              interface as the means of communication with the user level.
  5  *
  6  *              The Internet Protocol (IP) output module.
  7  *
  8  * Authors:     Ross Biro
  9  *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 10  *              Donald Becker, <becker@super.org>
 11  *              Alan Cox, <Alan.Cox@linux.org>
 12  *              Richard Underwood
 13  *              Stefan Becker, <stefanb@yello.ping.de>
 14  *              Jorge Cwik, <jorge@laser.satlink.net>
 15  *              Arnt Gulbrandsen, <agulbra@nvg.unit.no>
 16  *              Hirokazu Takahashi, <taka@valinux.co.jp>
 17  *
 18  *      See ip_input.c for original log
 19  *
 20  *      Fixes:
 21  *              Alan Cox        :       Missing nonblock feature in ip_build_xmit.
 22  *              Mike Kilburn    :       htons() missing in ip_build_xmit.
 23  *              Bradford Johnson:       Fix faulty handling of some frames when
 24  *                                      no route is found.
 25  *              Alexander Demenshin:    Missing sk/skb free in ip_queue_xmit
 26  *                                      (in case if packet not accepted by
 27  *                                      output firewall rules)
 28  *              Mike McLagan    :       Routing by source
 29  *              Alexey Kuznetsov:       use new route cache
 30  *              Andi Kleen:             Fix broken PMTU recovery and remove
 31  *                                      some redundant tests.
 32  *      Vitaly E. Lavrov        :       Transparent proxy revived after year coma.
 33  *              Andi Kleen      :       Replace ip_reply with ip_send_reply.
 34  *              Andi Kleen      :       Split fast and slow ip_build_xmit path
 35  *                                      for decreased register pressure on x86
 36  *                                      and more readibility.
 37  *              Marc Boucher    :       When call_out_firewall returns FW_QUEUE,
 38  *                                      silently drop skb instead of failing with -EPERM.
 39  *              Detlev Wengorz  :       Copy protocol for fragments.
 40  *              Hirokazu Takahashi:     HW checksumming for outgoing UDP
 41  *                                      datagrams.
 42  *              Hirokazu Takahashi:     sendfile() on UDP works now.
 43  */
 44 
 45 #include <asm/uaccess.h>
 46 #include <linux/module.h>
 47 #include <linux/types.h>
 48 #include <linux/kernel.h>
 49 #include <linux/mm.h>
 50 #include <linux/string.h>
 51 #include <linux/errno.h>
 52 #include <linux/highmem.h>
 53 #include <linux/slab.h>
 54 
 55 #include <linux/socket.h>
 56 #include <linux/sockios.h>
 57 #include <linux/in.h>
 58 #include <linux/inet.h>
 59 #include <linux/netdevice.h>
 60 #include <linux/etherdevice.h>
 61 #include <linux/proc_fs.h>
 62 #include <linux/stat.h>
 63 #include <linux/init.h>
 64 
 65 #include <net/snmp.h>
 66 #include <net/ip.h>
 67 #include <net/protocol.h>
 68 #include <net/route.h>
 69 #include <net/xfrm.h>
 70 #include <linux/skbuff.h>
 71 #include <net/sock.h>
 72 #include <net/arp.h>
 73 #include <net/icmp.h>
 74 #include <net/checksum.h>
 75 #include <net/inetpeer.h>
 76 #include <net/lwtunnel.h>
 77 #include <linux/igmp.h>
 78 #include <linux/netfilter_ipv4.h>
 79 #include <linux/netfilter_bridge.h>
 80 #include <linux/netlink.h>
 81 #include <linux/tcp.h>
 82 
 83 static int
 84 ip_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
 85             unsigned int mtu,
 86             int (*output)(struct net *, struct sock *, struct sk_buff *));
 87 
 88 /* Generate a checksum for an outgoing IP datagram. */
 89 void ip_send_check(struct iphdr *iph)
 90 {
 91         iph->check = 0;
 92         iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
 93 }
 94 EXPORT_SYMBOL(ip_send_check);
 95 
 96 int __ip_local_out(struct net *net, struct sock *sk, struct sk_buff *skb)
 97 {
 98         struct iphdr *iph = ip_hdr(skb);
 99 
100         iph->tot_len = htons(skb->len);
101         ip_send_check(iph);
102 
103         /* if egress device is enslaved to an L3 master device pass the
104          * skb to its handler for processing
105          */
106         skb = l3mdev_ip_out(sk, skb);
107         if (unlikely(!skb))
108                 return 0;
109 
110         skb->protocol = htons(ETH_P_IP);
111 
112         return nf_hook(NFPROTO_IPV4, NF_INET_LOCAL_OUT,
113                        net, sk, skb, NULL, skb_dst(skb)->dev,
114                        dst_output);
115 }
116 
117 int ip_local_out(struct net *net, struct sock *sk, struct sk_buff *skb)
118 {
119         int err;
120 
121         err = __ip_local_out(net, sk, skb);
122         if (likely(err == 1))
123                 err = dst_output(net, sk, skb);
124 
125         return err;
126 }
127 EXPORT_SYMBOL_GPL(ip_local_out);
128 
129 static inline int ip_select_ttl(struct inet_sock *inet, struct dst_entry *dst)
130 {
131         int ttl = inet->uc_ttl;
132 
133         if (ttl < 0)
134                 ttl = ip4_dst_hoplimit(dst);
135         return ttl;
136 }
137 
138 /*
139  *              Add an ip header to a skbuff and send it out.
140  *
141  */
142 int ip_build_and_send_pkt(struct sk_buff *skb, const struct sock *sk,
143                           __be32 saddr, __be32 daddr, struct ip_options_rcu *opt)
144 {
145         struct inet_sock *inet = inet_sk(sk);
146         struct rtable *rt = skb_rtable(skb);
147         struct net *net = sock_net(sk);
148         struct iphdr *iph;
149 
150         /* Build the IP header. */
151         skb_push(skb, sizeof(struct iphdr) + (opt ? opt->opt.optlen : 0));
152         skb_reset_network_header(skb);
153         iph = ip_hdr(skb);
154         iph->version  = 4;
155         iph->ihl      = 5;
156         iph->tos      = inet->tos;
157         iph->ttl      = ip_select_ttl(inet, &rt->dst);
158         iph->daddr    = (opt && opt->opt.srr ? opt->opt.faddr : daddr);
159         iph->saddr    = saddr;
160         iph->protocol = sk->sk_protocol;
161         if (ip_dont_fragment(sk, &rt->dst)) {
162                 iph->frag_off = htons(IP_DF);
163                 iph->id = 0;
164         } else {
165                 iph->frag_off = 0;
166                 __ip_select_ident(net, iph, 1);
167         }
168 
169         if (opt && opt->opt.optlen) {
170                 iph->ihl += opt->opt.optlen>>2;
171                 ip_options_build(skb, &opt->opt, daddr, rt, 0);
172         }
173 
174         skb->priority = sk->sk_priority;
175         skb->mark = sk->sk_mark;
176 
177         /* Send it out. */
178         return ip_local_out(net, skb->sk, skb);
179 }
180 EXPORT_SYMBOL_GPL(ip_build_and_send_pkt);
181 
182 static int ip_finish_output2(struct net *net, struct sock *sk, struct sk_buff *skb)
183 {
184         struct dst_entry *dst = skb_dst(skb);
185         struct rtable *rt = (struct rtable *)dst;
186         struct net_device *dev = dst->dev;
187         unsigned int hh_len = LL_RESERVED_SPACE(dev);
188         struct neighbour *neigh;
189         u32 nexthop;
190 
191         if (rt->rt_type == RTN_MULTICAST) {
192                 IP_UPD_PO_STATS(net, IPSTATS_MIB_OUTMCAST, skb->len);
193         } else if (rt->rt_type == RTN_BROADCAST)
194                 IP_UPD_PO_STATS(net, IPSTATS_MIB_OUTBCAST, skb->len);
195 
196         /* Be paranoid, rather than too clever. */
197         if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) {
198                 struct sk_buff *skb2;
199 
200                 skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev));
201                 if (!skb2) {
202                         kfree_skb(skb);
203                         return -ENOMEM;
204                 }
205                 if (skb->sk)
206                         skb_set_owner_w(skb2, skb->sk);
207                 consume_skb(skb);
208                 skb = skb2;
209         }
210 
211         if (lwtunnel_xmit_redirect(dst->lwtstate)) {
212                 int res = lwtunnel_xmit(skb);
213 
214                 if (res < 0 || res == LWTUNNEL_XMIT_DONE)
215                         return res;
216         }
217 
218         rcu_read_lock_bh();
219         nexthop = (__force u32) rt_nexthop(rt, ip_hdr(skb)->daddr);
220         neigh = __ipv4_neigh_lookup_noref(dev, nexthop);
221         if (unlikely(!neigh))
222                 neigh = __neigh_create(&arp_tbl, &nexthop, dev, false);
223         if (!IS_ERR(neigh)) {
224                 int res = dst_neigh_output(dst, neigh, skb);
225 
226                 rcu_read_unlock_bh();
227                 return res;
228         }
229         rcu_read_unlock_bh();
230 
231         net_dbg_ratelimited("%s: No header cache and no neighbour!\n",
232                             __func__);
233         kfree_skb(skb);
234         return -EINVAL;
235 }
236 
237 static int ip_finish_output_gso(struct net *net, struct sock *sk,
238                                 struct sk_buff *skb, unsigned int mtu)
239 {
240         netdev_features_t features;
241         struct sk_buff *segs;
242         int ret = 0;
243 
244         /* common case: seglen is <= mtu
245          */
246         if (skb_gso_validate_mtu(skb, mtu))
247                 return ip_finish_output2(net, sk, skb);
248 
249         /* Slowpath -  GSO segment length exceeds the egress MTU.
250          *
251          * This can happen in several cases:
252          *  - Forwarding of a TCP GRO skb, when DF flag is not set.
253          *  - Forwarding of an skb that arrived on a virtualization interface
254          *    (virtio-net/vhost/tap) with TSO/GSO size set by other network
255          *    stack.
256          *  - Local GSO skb transmitted on an NETIF_F_TSO tunnel stacked over an
257          *    interface with a smaller MTU.
258          *  - Arriving GRO skb (or GSO skb in a virtualized environment) that is
259          *    bridged to a NETIF_F_TSO tunnel stacked over an interface with an
260          *    insufficent MTU.
261          */
262         features = netif_skb_features(skb);
263         BUILD_BUG_ON(sizeof(*IPCB(skb)) > SKB_SGO_CB_OFFSET);
264         segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK);
265         if (IS_ERR_OR_NULL(segs)) {
266                 kfree_skb(skb);
267                 return -ENOMEM;
268         }
269 
270         consume_skb(skb);
271 
272         do {
273                 struct sk_buff *nskb = segs->next;
274                 int err;
275 
276                 segs->next = NULL;
277                 err = ip_fragment(net, sk, segs, mtu, ip_finish_output2);
278 
279                 if (err && ret == 0)
280                         ret = err;
281                 segs = nskb;
282         } while (segs);
283 
284         return ret;
285 }
286 
287 static int ip_finish_output(struct net *net, struct sock *sk, struct sk_buff *skb)
288 {
289         unsigned int mtu;
290 
291 #if defined(CONFIG_NETFILTER) && defined(CONFIG_XFRM)
292         /* Policy lookup after SNAT yielded a new policy */
293         if (skb_dst(skb)->xfrm) {
294                 IPCB(skb)->flags |= IPSKB_REROUTED;
295                 return dst_output(net, sk, skb);
296         }
297 #endif
298         mtu = ip_skb_dst_mtu(sk, skb);
299         if (skb_is_gso(skb))
300                 return ip_finish_output_gso(net, sk, skb, mtu);
301 
302         if (skb->len > mtu || (IPCB(skb)->flags & IPSKB_FRAG_PMTU))
303                 return ip_fragment(net, sk, skb, mtu, ip_finish_output2);
304 
305         return ip_finish_output2(net, sk, skb);
306 }
307 
308 int ip_mc_output(struct net *net, struct sock *sk, struct sk_buff *skb)
309 {
310         struct rtable *rt = skb_rtable(skb);
311         struct net_device *dev = rt->dst.dev;
312 
313         /*
314          *      If the indicated interface is up and running, send the packet.
315          */
316         IP_UPD_PO_STATS(net, IPSTATS_MIB_OUT, skb->len);
317 
318         skb->dev = dev;
319         skb->protocol = htons(ETH_P_IP);
320 
321         /*
322          *      Multicasts are looped back for other local users
323          */
324 
325         if (rt->rt_flags&RTCF_MULTICAST) {
326                 if (sk_mc_loop(sk)
327 #ifdef CONFIG_IP_MROUTE
328                 /* Small optimization: do not loopback not local frames,
329                    which returned after forwarding; they will be  dropped
330                    by ip_mr_input in any case.
331                    Note, that local frames are looped back to be delivered
332                    to local recipients.
333 
334                    This check is duplicated in ip_mr_input at the moment.
335                  */
336                     &&
337                     ((rt->rt_flags & RTCF_LOCAL) ||
338                      !(IPCB(skb)->flags & IPSKB_FORWARDED))
339 #endif
340                    ) {
341                         struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
342                         if (newskb)
343                                 NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING,
344                                         net, sk, newskb, NULL, newskb->dev,
345                                         dev_loopback_xmit);
346                 }
347 
348                 /* Multicasts with ttl 0 must not go beyond the host */
349 
350                 if (ip_hdr(skb)->ttl == 0) {
351                         kfree_skb(skb);
352                         return 0;
353                 }
354         }
355 
356         if (rt->rt_flags&RTCF_BROADCAST) {
357                 struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
358                 if (newskb)
359                         NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING,
360                                 net, sk, newskb, NULL, newskb->dev,
361                                 dev_loopback_xmit);
362         }
363 
364         return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
365                             net, sk, skb, NULL, skb->dev,
366                             ip_finish_output,
367                             !(IPCB(skb)->flags & IPSKB_REROUTED));
368 }
369 
370 int ip_output(struct net *net, struct sock *sk, struct sk_buff *skb)
371 {
372         struct net_device *dev = skb_dst(skb)->dev;
373 
374         IP_UPD_PO_STATS(net, IPSTATS_MIB_OUT, skb->len);
375 
376         skb->dev = dev;
377         skb->protocol = htons(ETH_P_IP);
378 
379         return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
380                             net, sk, skb, NULL, dev,
381                             ip_finish_output,
382                             !(IPCB(skb)->flags & IPSKB_REROUTED));
383 }
384 
385 /*
386  * copy saddr and daddr, possibly using 64bit load/stores
387  * Equivalent to :
388  *   iph->saddr = fl4->saddr;
389  *   iph->daddr = fl4->daddr;
390  */
391 static void ip_copy_addrs(struct iphdr *iph, const struct flowi4 *fl4)
392 {
393         BUILD_BUG_ON(offsetof(typeof(*fl4), daddr) !=
394                      offsetof(typeof(*fl4), saddr) + sizeof(fl4->saddr));
395         memcpy(&iph->saddr, &fl4->saddr,
396                sizeof(fl4->saddr) + sizeof(fl4->daddr));
397 }
398 
399 /* Note: skb->sk can be different from sk, in case of tunnels */
400 int ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl)
401 {
402         struct inet_sock *inet = inet_sk(sk);
403         struct net *net = sock_net(sk);
404         struct ip_options_rcu *inet_opt;
405         struct flowi4 *fl4;
406         struct rtable *rt;
407         struct iphdr *iph;
408         int res;
409 
410         /* Skip all of this if the packet is already routed,
411          * f.e. by something like SCTP.
412          */
413         rcu_read_lock();
414         inet_opt = rcu_dereference(inet->inet_opt);
415         fl4 = &fl->u.ip4;
416         rt = skb_rtable(skb);
417         if (rt)
418                 goto packet_routed;
419 
420         /* Make sure we can route this packet. */
421         rt = (struct rtable *)__sk_dst_check(sk, 0);
422         if (!rt) {
423                 __be32 daddr;
424 
425                 /* Use correct destination address if we have options. */
426                 daddr = inet->inet_daddr;
427                 if (inet_opt && inet_opt->opt.srr)
428                         daddr = inet_opt->opt.faddr;
429 
430                 /* If this fails, retransmit mechanism of transport layer will
431                  * keep trying until route appears or the connection times
432                  * itself out.
433                  */
434                 rt = ip_route_output_ports(net, fl4, sk,
435                                            daddr, inet->inet_saddr,
436                                            inet->inet_dport,
437                                            inet->inet_sport,
438                                            sk->sk_protocol,
439                                            RT_CONN_FLAGS(sk),
440                                            sk->sk_bound_dev_if);
441                 if (IS_ERR(rt))
442                         goto no_route;
443                 sk_setup_caps(sk, &rt->dst);
444         }
445         skb_dst_set_noref(skb, &rt->dst);
446 
447 packet_routed:
448         if (inet_opt && inet_opt->opt.is_strictroute && rt->rt_uses_gateway)
449                 goto no_route;
450 
451         /* OK, we know where to send it, allocate and build IP header. */
452         skb_push(skb, sizeof(struct iphdr) + (inet_opt ? inet_opt->opt.optlen : 0));
453         skb_reset_network_header(skb);
454         iph = ip_hdr(skb);
455         *((__be16 *)iph) = htons((4 << 12) | (5 << 8) | (inet->tos & 0xff));
456         if (ip_dont_fragment(sk, &rt->dst) && !skb->ignore_df)
457                 iph->frag_off = htons(IP_DF);
458         else
459                 iph->frag_off = 0;
460         iph->ttl      = ip_select_ttl(inet, &rt->dst);
461         iph->protocol = sk->sk_protocol;
462         ip_copy_addrs(iph, fl4);
463 
464         /* Transport layer set skb->h.foo itself. */
465 
466         if (inet_opt && inet_opt->opt.optlen) {
467                 iph->ihl += inet_opt->opt.optlen >> 2;
468                 ip_options_build(skb, &inet_opt->opt, inet->inet_daddr, rt, 0);
469         }
470 
471         ip_select_ident_segs(net, skb, sk,
472                              skb_shinfo(skb)->gso_segs ?: 1);
473 
474         /* TODO : should we use skb->sk here instead of sk ? */
475         skb->priority = sk->sk_priority;
476         skb->mark = sk->sk_mark;
477 
478         res = ip_local_out(net, sk, skb);
479         rcu_read_unlock();
480         return res;
481 
482 no_route:
483         rcu_read_unlock();
484         IP_INC_STATS(net, IPSTATS_MIB_OUTNOROUTES);
485         kfree_skb(skb);
486         return -EHOSTUNREACH;
487 }
488 EXPORT_SYMBOL(ip_queue_xmit);
489 
490 static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
491 {
492         to->pkt_type = from->pkt_type;
493         to->priority = from->priority;
494         to->protocol = from->protocol;
495         skb_dst_drop(to);
496         skb_dst_copy(to, from);
497         to->dev = from->dev;
498         to->mark = from->mark;
499 
500         /* Copy the flags to each fragment. */
501         IPCB(to)->flags = IPCB(from)->flags;
502 
503 #ifdef CONFIG_NET_SCHED
504         to->tc_index = from->tc_index;
505 #endif
506         nf_copy(to, from);
507 #if IS_ENABLED(CONFIG_IP_VS)
508         to->ipvs_property = from->ipvs_property;
509 #endif
510         skb_copy_secmark(to, from);
511 }
512 
513 static int ip_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
514                        unsigned int mtu,
515                        int (*output)(struct net *, struct sock *, struct sk_buff *))
516 {
517         struct iphdr *iph = ip_hdr(skb);
518 
519         if ((iph->frag_off & htons(IP_DF)) == 0)
520                 return ip_do_fragment(net, sk, skb, output);
521 
522         if (unlikely(!skb->ignore_df ||
523                      (IPCB(skb)->frag_max_size &&
524                       IPCB(skb)->frag_max_size > mtu))) {
525                 IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
526                 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
527                           htonl(mtu));
528                 kfree_skb(skb);
529                 return -EMSGSIZE;
530         }
531 
532         return ip_do_fragment(net, sk, skb, output);
533 }
534 
535 /*
536  *      This IP datagram is too large to be sent in one piece.  Break it up into
537  *      smaller pieces (each of size equal to IP header plus
538  *      a block of the data of the original IP data part) that will yet fit in a
539  *      single device frame, and queue such a frame for sending.
540  */
541 
542 int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
543                    int (*output)(struct net *, struct sock *, struct sk_buff *))
544 {
545         struct iphdr *iph;
546         int ptr;
547         struct sk_buff *skb2;
548         unsigned int mtu, hlen, left, len, ll_rs;
549         int offset;
550         __be16 not_last_frag;
551         struct rtable *rt = skb_rtable(skb);
552         int err = 0;
553 
554         /* for offloaded checksums cleanup checksum before fragmentation */
555         if (skb->ip_summed == CHECKSUM_PARTIAL &&
556             (err = skb_checksum_help(skb)))
557                 goto fail;
558 
559         /*
560          *      Point into the IP datagram header.
561          */
562 
563         iph = ip_hdr(skb);
564 
565         mtu = ip_skb_dst_mtu(sk, skb);
566         if (IPCB(skb)->frag_max_size && IPCB(skb)->frag_max_size < mtu)
567                 mtu = IPCB(skb)->frag_max_size;
568 
569         /*
570          *      Setup starting values.
571          */
572 
573         hlen = iph->ihl * 4;
574         mtu = mtu - hlen;       /* Size of data space */
575         IPCB(skb)->flags |= IPSKB_FRAG_COMPLETE;
576 
577         /* When frag_list is given, use it. First, check its validity:
578          * some transformers could create wrong frag_list or break existing
579          * one, it is not prohibited. In this case fall back to copying.
580          *
581          * LATER: this step can be merged to real generation of fragments,
582          * we can switch to copy when see the first bad fragment.
583          */
584         if (skb_has_frag_list(skb)) {
585                 struct sk_buff *frag, *frag2;
586                 int first_len = skb_pagelen(skb);
587 
588                 if (first_len - hlen > mtu ||
589                     ((first_len - hlen) & 7) ||
590                     ip_is_fragment(iph) ||
591                     skb_cloned(skb))
592                         goto slow_path;
593 
594                 skb_walk_frags(skb, frag) {
595                         /* Correct geometry. */
596                         if (frag->len > mtu ||
597                             ((frag->len & 7) && frag->next) ||
598                             skb_headroom(frag) < hlen)
599                                 goto slow_path_clean;
600 
601                         /* Partially cloned skb? */
602                         if (skb_shared(frag))
603                                 goto slow_path_clean;
604 
605                         BUG_ON(frag->sk);
606                         if (skb->sk) {
607                                 frag->sk = skb->sk;
608                                 frag->destructor = sock_wfree;
609                         }
610                         skb->truesize -= frag->truesize;
611                 }
612 
613                 /* Everything is OK. Generate! */
614 
615                 err = 0;
616                 offset = 0;
617                 frag = skb_shinfo(skb)->frag_list;
618                 skb_frag_list_init(skb);
619                 skb->data_len = first_len - skb_headlen(skb);
620                 skb->len = first_len;
621                 iph->tot_len = htons(first_len);
622                 iph->frag_off = htons(IP_MF);
623                 ip_send_check(iph);
624 
625                 for (;;) {
626                         /* Prepare header of the next frame,
627                          * before previous one went down. */
628                         if (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                                 iph = ip_hdr(frag);
635                                 iph->tot_len = htons(frag->len);
636                                 ip_copy_metadata(frag, skb);
637                                 if (offset == 0)
638                                         ip_options_fragment(frag);
639                                 offset += skb->len - hlen;
640                                 iph->frag_off = htons(offset>>3);
641                                 if (frag->next)
642                                         iph->frag_off |= htons(IP_MF);
643                                 /* Ready, complete checksum */
644                                 ip_send_check(iph);
645                         }
646 
647                         err = output(net, sk, skb);
648 
649                         if (!err)
650                                 IP_INC_STATS(net, IPSTATS_MIB_FRAGCREATES);
651                         if (err || !frag)
652                                 break;
653 
654                         skb = frag;
655                         frag = skb->next;
656                         skb->next = NULL;
657                 }
658 
659                 if (err == 0) {
660                         IP_INC_STATS(net, IPSTATS_MIB_FRAGOKS);
661                         return 0;
662                 }
663 
664                 while (frag) {
665                         skb = frag->next;
666                         kfree_skb(frag);
667                         frag = skb;
668                 }
669                 IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
670                 return err;
671 
672 slow_path_clean:
673                 skb_walk_frags(skb, frag2) {
674                         if (frag2 == frag)
675                                 break;
676                         frag2->sk = NULL;
677                         frag2->destructor = NULL;
678                         skb->truesize += frag2->truesize;
679                 }
680         }
681 
682 slow_path:
683         iph = ip_hdr(skb);
684 
685         left = skb->len - hlen;         /* Space per frame */
686         ptr = hlen;             /* Where to start from */
687 
688         ll_rs = LL_RESERVED_SPACE(rt->dst.dev);
689 
690         /*
691          *      Fragment the datagram.
692          */
693 
694         offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3;
695         not_last_frag = iph->frag_off & htons(IP_MF);
696 
697         /*
698          *      Keep copying data until we run out.
699          */
700 
701         while (left > 0) {
702                 len = left;
703                 /* IF: it doesn't fit, use 'mtu' - the data space left */
704                 if (len > mtu)
705                         len = mtu;
706                 /* IF: we are not sending up to and including the packet end
707                    then align the next start on an eight byte boundary */
708                 if (len < left) {
709                         len &= ~7;
710                 }
711 
712                 /* Allocate buffer */
713                 skb2 = alloc_skb(len + hlen + ll_rs, GFP_ATOMIC);
714                 if (!skb2) {
715                         err = -ENOMEM;
716                         goto fail;
717                 }
718 
719                 /*
720                  *      Set up data on packet
721                  */
722 
723                 ip_copy_metadata(skb2, skb);
724                 skb_reserve(skb2, ll_rs);
725                 skb_put(skb2, len + hlen);
726                 skb_reset_network_header(skb2);
727                 skb2->transport_header = skb2->network_header + hlen;
728 
729                 /*
730                  *      Charge the memory for the fragment to any owner
731                  *      it might possess
732                  */
733 
734                 if (skb->sk)
735                         skb_set_owner_w(skb2, skb->sk);
736 
737                 /*
738                  *      Copy the packet header into the new buffer.
739                  */
740 
741                 skb_copy_from_linear_data(skb, skb_network_header(skb2), hlen);
742 
743                 /*
744                  *      Copy a block of the IP datagram.
745                  */
746                 if (skb_copy_bits(skb, ptr, skb_transport_header(skb2), len))
747                         BUG();
748                 left -= len;
749 
750                 /*
751                  *      Fill in the new header fields.
752                  */
753                 iph = ip_hdr(skb2);
754                 iph->frag_off = htons((offset >> 3));
755 
756                 if (IPCB(skb)->flags & IPSKB_FRAG_PMTU)
757                         iph->frag_off |= htons(IP_DF);
758 
759                 /* ANK: dirty, but effective trick. Upgrade options only if
760                  * the segment to be fragmented was THE FIRST (otherwise,
761                  * options are already fixed) and make it ONCE
762                  * on the initial skb, so that all the following fragments
763                  * will inherit fixed options.
764                  */
765                 if (offset == 0)
766                         ip_options_fragment(skb);
767 
768                 /*
769                  *      Added AC : If we are fragmenting a fragment that's not the
770                  *                 last fragment then keep MF on each bit
771                  */
772                 if (left > 0 || not_last_frag)
773                         iph->frag_off |= htons(IP_MF);
774                 ptr += len;
775                 offset += len;
776 
777                 /*
778                  *      Put this fragment into the sending queue.
779                  */
780                 iph->tot_len = htons(len + hlen);
781 
782                 ip_send_check(iph);
783 
784                 err = output(net, sk, skb2);
785                 if (err)
786                         goto fail;
787 
788                 IP_INC_STATS(net, IPSTATS_MIB_FRAGCREATES);
789         }
790         consume_skb(skb);
791         IP_INC_STATS(net, IPSTATS_MIB_FRAGOKS);
792         return err;
793 
794 fail:
795         kfree_skb(skb);
796         IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
797         return err;
798 }
799 EXPORT_SYMBOL(ip_do_fragment);
800 
801 int
802 ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
803 {
804         struct msghdr *msg = from;
805 
806         if (skb->ip_summed == CHECKSUM_PARTIAL) {
807                 if (copy_from_iter(to, len, &msg->msg_iter) != len)
808                         return -EFAULT;
809         } else {
810                 __wsum csum = 0;
811                 if (csum_and_copy_from_iter(to, len, &csum, &msg->msg_iter) != len)
812                         return -EFAULT;
813                 skb->csum = csum_block_add(skb->csum, csum, odd);
814         }
815         return 0;
816 }
817 EXPORT_SYMBOL(ip_generic_getfrag);
818 
819 static inline __wsum
820 csum_page(struct page *page, int offset, int copy)
821 {
822         char *kaddr;
823         __wsum csum;
824         kaddr = kmap(page);
825         csum = csum_partial(kaddr + offset, copy, 0);
826         kunmap(page);
827         return csum;
828 }
829 
830 static inline int ip_ufo_append_data(struct sock *sk,
831                         struct sk_buff_head *queue,
832                         int getfrag(void *from, char *to, int offset, int len,
833                                int odd, struct sk_buff *skb),
834                         void *from, int length, int hh_len, int fragheaderlen,
835                         int transhdrlen, int maxfraglen, unsigned int flags)
836 {
837         struct sk_buff *skb;
838         int err;
839 
840         /* There is support for UDP fragmentation offload by network
841          * device, so create one single skb packet containing complete
842          * udp datagram
843          */
844         skb = skb_peek_tail(queue);
845         if (!skb) {
846                 skb = sock_alloc_send_skb(sk,
847                         hh_len + fragheaderlen + transhdrlen + 20,
848                         (flags & MSG_DONTWAIT), &err);
849 
850                 if (!skb)
851                         return err;
852 
853                 /* reserve space for Hardware header */
854                 skb_reserve(skb, hh_len);
855 
856                 /* create space for UDP/IP header */
857                 skb_put(skb, fragheaderlen + transhdrlen);
858 
859                 /* initialize network header pointer */
860                 skb_reset_network_header(skb);
861 
862                 /* initialize protocol header pointer */
863                 skb->transport_header = skb->network_header + fragheaderlen;
864 
865                 skb->csum = 0;
866 
867                 __skb_queue_tail(queue, skb);
868         } else if (skb_is_gso(skb)) {
869                 goto append;
870         }
871 
872         skb->ip_summed = CHECKSUM_PARTIAL;
873         /* specify the length of each IP datagram fragment */
874         skb_shinfo(skb)->gso_size = maxfraglen - fragheaderlen;
875         skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
876 
877 append:
878         return skb_append_datato_frags(sk, skb, getfrag, from,
879                                        (length - transhdrlen));
880 }
881 
882 static int __ip_append_data(struct sock *sk,
883                             struct flowi4 *fl4,
884                             struct sk_buff_head *queue,
885                             struct inet_cork *cork,
886                             struct page_frag *pfrag,
887                             int getfrag(void *from, char *to, int offset,
888                                         int len, int odd, struct sk_buff *skb),
889                             void *from, int length, int transhdrlen,
890                             unsigned int flags)
891 {
892         struct inet_sock *inet = inet_sk(sk);
893         struct sk_buff *skb;
894 
895         struct ip_options *opt = cork->opt;
896         int hh_len;
897         int exthdrlen;
898         int mtu;
899         int copy;
900         int err;
901         int offset = 0;
902         unsigned int maxfraglen, fragheaderlen, maxnonfragsize;
903         int csummode = CHECKSUM_NONE;
904         struct rtable *rt = (struct rtable *)cork->dst;
905         u32 tskey = 0;
906 
907         skb = skb_peek_tail(queue);
908 
909         exthdrlen = !skb ? rt->dst.header_len : 0;
910         mtu = cork->fragsize;
911         if (cork->tx_flags & SKBTX_ANY_SW_TSTAMP &&
912             sk->sk_tsflags & SOF_TIMESTAMPING_OPT_ID)
913                 tskey = sk->sk_tskey++;
914 
915         hh_len = LL_RESERVED_SPACE(rt->dst.dev);
916 
917         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
918         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
919         maxnonfragsize = ip_sk_ignore_df(sk) ? 0xFFFF : mtu;
920 
921         if (cork->length + length > maxnonfragsize - fragheaderlen) {
922                 ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
923                                mtu - (opt ? opt->optlen : 0));
924                 return -EMSGSIZE;
925         }
926 
927         /*
928          * transhdrlen > 0 means that this is the first fragment and we wish
929          * it won't be fragmented in the future.
930          */
931         if (transhdrlen &&
932             length + fragheaderlen <= mtu &&
933             rt->dst.dev->features & (NETIF_F_HW_CSUM | NETIF_F_IP_CSUM) &&
934             !(flags & MSG_MORE) &&
935             !exthdrlen)
936                 csummode = CHECKSUM_PARTIAL;
937 
938         cork->length += length;
939         if (((length > mtu) || (skb && skb_is_gso(skb))) &&
940             (sk->sk_protocol == IPPROTO_UDP) &&
941             (rt->dst.dev->features & NETIF_F_UFO) && !rt->dst.header_len &&
942             (sk->sk_type == SOCK_DGRAM) && !sk->sk_no_check_tx) {
943                 err = ip_ufo_append_data(sk, queue, getfrag, from, length,
944                                          hh_len, fragheaderlen, transhdrlen,
945                                          maxfraglen, flags);
946                 if (err)
947                         goto error;
948                 return 0;
949         }
950 
951         /* So, what's going on in the loop below?
952          *
953          * We use calculated fragment length to generate chained skb,
954          * each of segments is IP fragment ready for sending to network after
955          * adding appropriate IP header.
956          */
957 
958         if (!skb)
959                 goto alloc_new_skb;
960 
961         while (length > 0) {
962                 /* Check if the remaining data fits into current packet. */
963                 copy = mtu - skb->len;
964                 if (copy < length)
965                         copy = maxfraglen - skb->len;
966                 if (copy <= 0) {
967                         char *data;
968                         unsigned int datalen;
969                         unsigned int fraglen;
970                         unsigned int fraggap;
971                         unsigned int alloclen;
972                         struct sk_buff *skb_prev;
973 alloc_new_skb:
974                         skb_prev = skb;
975                         if (skb_prev)
976                                 fraggap = skb_prev->len - maxfraglen;
977                         else
978                                 fraggap = 0;
979 
980                         /*
981                          * If remaining data exceeds the mtu,
982                          * we know we need more fragment(s).
983                          */
984                         datalen = length + fraggap;
985                         if (datalen > mtu - fragheaderlen)
986                                 datalen = maxfraglen - fragheaderlen;
987                         fraglen = datalen + fragheaderlen;
988 
989                         if ((flags & MSG_MORE) &&
990                             !(rt->dst.dev->features&NETIF_F_SG))
991                                 alloclen = mtu;
992                         else
993                                 alloclen = fraglen;
994 
995                         alloclen += exthdrlen;
996 
997                         /* The last fragment gets additional space at tail.
998                          * Note, with MSG_MORE we overallocate on fragments,
999                          * because we have no idea what fragment will be
1000                          * the last.
1001                          */
1002                         if (datalen == length + fraggap)
1003                                 alloclen += rt->dst.trailer_len;
1004 
1005                         if (transhdrlen) {
1006                                 skb = sock_alloc_send_skb(sk,
1007                                                 alloclen + hh_len + 15,
1008                                                 (flags & MSG_DONTWAIT), &err);
1009                         } else {
1010                                 skb = NULL;
1011                                 if (atomic_read(&sk->sk_wmem_alloc) <=
1012                                     2 * sk->sk_sndbuf)
1013                                         skb = sock_wmalloc(sk,
1014                                                            alloclen + hh_len + 15, 1,
1015                                                            sk->sk_allocation);
1016                                 if (unlikely(!skb))
1017                                         err = -ENOBUFS;
1018                         }
1019                         if (!skb)
1020                                 goto error;
1021 
1022                         /*
1023                          *      Fill in the control structures
1024                          */
1025                         skb->ip_summed = csummode;
1026                         skb->csum = 0;
1027                         skb_reserve(skb, hh_len);
1028 
1029                         /* only the initial fragment is time stamped */
1030                         skb_shinfo(skb)->tx_flags = cork->tx_flags;
1031                         cork->tx_flags = 0;
1032                         skb_shinfo(skb)->tskey = tskey;
1033                         tskey = 0;
1034 
1035                         /*
1036                          *      Find where to start putting bytes.
1037                          */
1038                         data = skb_put(skb, fraglen + exthdrlen);
1039                         skb_set_network_header(skb, exthdrlen);
1040                         skb->transport_header = (skb->network_header +
1041                                                  fragheaderlen);
1042                         data += fragheaderlen + exthdrlen;
1043 
1044                         if (fraggap) {
1045                                 skb->csum = skb_copy_and_csum_bits(
1046                                         skb_prev, maxfraglen,
1047                                         data + transhdrlen, fraggap, 0);
1048                                 skb_prev->csum = csum_sub(skb_prev->csum,
1049                                                           skb->csum);
1050                                 data += fraggap;
1051                                 pskb_trim_unique(skb_prev, maxfraglen);
1052                         }
1053 
1054                         copy = datalen - transhdrlen - fraggap;
1055                         if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
1056                                 err = -EFAULT;
1057                                 kfree_skb(skb);
1058                                 goto error;
1059                         }
1060 
1061                         offset += copy;
1062                         length -= datalen - fraggap;
1063                         transhdrlen = 0;
1064                         exthdrlen = 0;
1065                         csummode = CHECKSUM_NONE;
1066 
1067                         /*
1068                          * Put the packet on the pending queue.
1069                          */
1070                         __skb_queue_tail(queue, skb);
1071                         continue;
1072                 }
1073 
1074                 if (copy > length)
1075                         copy = length;
1076 
1077                 if (!(rt->dst.dev->features&NETIF_F_SG)) {
1078                         unsigned int off;
1079 
1080                         off = skb->len;
1081                         if (getfrag(from, skb_put(skb, copy),
1082                                         offset, copy, off, skb) < 0) {
1083                                 __skb_trim(skb, off);
1084                                 err = -EFAULT;
1085                                 goto error;
1086                         }
1087                 } else {
1088                         int i = skb_shinfo(skb)->nr_frags;
1089 
1090                         err = -ENOMEM;
1091                         if (!sk_page_frag_refill(sk, pfrag))
1092                                 goto error;
1093 
1094                         if (!skb_can_coalesce(skb, i, pfrag->page,
1095                                               pfrag->offset)) {
1096                                 err = -EMSGSIZE;
1097                                 if (i == MAX_SKB_FRAGS)
1098                                         goto error;
1099 
1100                                 __skb_fill_page_desc(skb, i, pfrag->page,
1101                                                      pfrag->offset, 0);
1102                                 skb_shinfo(skb)->nr_frags = ++i;
1103                                 get_page(pfrag->page);
1104                         }
1105                         copy = min_t(int, copy, pfrag->size - pfrag->offset);
1106                         if (getfrag(from,
1107                                     page_address(pfrag->page) + pfrag->offset,
1108                                     offset, copy, skb->len, skb) < 0)
1109                                 goto error_efault;
1110 
1111                         pfrag->offset += copy;
1112                         skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
1113                         skb->len += copy;
1114                         skb->data_len += copy;
1115                         skb->truesize += copy;
1116                         atomic_add(copy, &sk->sk_wmem_alloc);
1117                 }
1118                 offset += copy;
1119                 length -= copy;
1120         }
1121 
1122         return 0;
1123 
1124 error_efault:
1125         err = -EFAULT;
1126 error:
1127         cork->length -= length;
1128         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1129         return err;
1130 }
1131 
1132 static int ip_setup_cork(struct sock *sk, struct inet_cork *cork,
1133                          struct ipcm_cookie *ipc, struct rtable **rtp)
1134 {
1135         struct ip_options_rcu *opt;
1136         struct rtable *rt;
1137 
1138         /*
1139          * setup for corking.
1140          */
1141         opt = ipc->opt;
1142         if (opt) {
1143                 if (!cork->opt) {
1144                         cork->opt = kmalloc(sizeof(struct ip_options) + 40,
1145                                             sk->sk_allocation);
1146                         if (unlikely(!cork->opt))
1147                                 return -ENOBUFS;
1148                 }
1149                 memcpy(cork->opt, &opt->opt, sizeof(struct ip_options) + opt->opt.optlen);
1150                 cork->flags |= IPCORK_OPT;
1151                 cork->addr = ipc->addr;
1152         }
1153         rt = *rtp;
1154         if (unlikely(!rt))
1155                 return -EFAULT;
1156         /*
1157          * We steal reference to this route, caller should not release it
1158          */
1159         *rtp = NULL;
1160         cork->fragsize = ip_sk_use_pmtu(sk) ?
1161                          dst_mtu(&rt->dst) : rt->dst.dev->mtu;
1162         cork->dst = &rt->dst;
1163         cork->length = 0;
1164         cork->ttl = ipc->ttl;
1165         cork->tos = ipc->tos;
1166         cork->priority = ipc->priority;
1167         cork->tx_flags = ipc->tx_flags;
1168 
1169         return 0;
1170 }
1171 
1172 /*
1173  *      ip_append_data() and ip_append_page() can make one large IP datagram
1174  *      from many pieces of data. Each pieces will be holded on the socket
1175  *      until ip_push_pending_frames() is called. Each piece can be a page
1176  *      or non-page data.
1177  *
1178  *      Not only UDP, other transport protocols - e.g. raw sockets - can use
1179  *      this interface potentially.
1180  *
1181  *      LATER: length must be adjusted by pad at tail, when it is required.
1182  */
1183 int ip_append_data(struct sock *sk, struct flowi4 *fl4,
1184                    int getfrag(void *from, char *to, int offset, int len,
1185                                int odd, struct sk_buff *skb),
1186                    void *from, int length, int transhdrlen,
1187                    struct ipcm_cookie *ipc, struct rtable **rtp,
1188                    unsigned int flags)
1189 {
1190         struct inet_sock *inet = inet_sk(sk);
1191         int err;
1192 
1193         if (flags&MSG_PROBE)
1194                 return 0;
1195 
1196         if (skb_queue_empty(&sk->sk_write_queue)) {
1197                 err = ip_setup_cork(sk, &inet->cork.base, ipc, rtp);
1198                 if (err)
1199                         return err;
1200         } else {
1201                 transhdrlen = 0;
1202         }
1203 
1204         return __ip_append_data(sk, fl4, &sk->sk_write_queue, &inet->cork.base,
1205                                 sk_page_frag(sk), getfrag,
1206                                 from, length, transhdrlen, flags);
1207 }
1208 
1209 ssize_t ip_append_page(struct sock *sk, struct flowi4 *fl4, struct page *page,
1210                        int offset, size_t size, int flags)
1211 {
1212         struct inet_sock *inet = inet_sk(sk);
1213         struct sk_buff *skb;
1214         struct rtable *rt;
1215         struct ip_options *opt = NULL;
1216         struct inet_cork *cork;
1217         int hh_len;
1218         int mtu;
1219         int len;
1220         int err;
1221         unsigned int maxfraglen, fragheaderlen, fraggap, maxnonfragsize;
1222 
1223         if (inet->hdrincl)
1224                 return -EPERM;
1225 
1226         if (flags&MSG_PROBE)
1227                 return 0;
1228 
1229         if (skb_queue_empty(&sk->sk_write_queue))
1230                 return -EINVAL;
1231 
1232         cork = &inet->cork.base;
1233         rt = (struct rtable *)cork->dst;
1234         if (cork->flags & IPCORK_OPT)
1235                 opt = cork->opt;
1236 
1237         if (!(rt->dst.dev->features&NETIF_F_SG))
1238                 return -EOPNOTSUPP;
1239 
1240         hh_len = LL_RESERVED_SPACE(rt->dst.dev);
1241         mtu = cork->fragsize;
1242 
1243         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
1244         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
1245         maxnonfragsize = ip_sk_ignore_df(sk) ? 0xFFFF : mtu;
1246 
1247         if (cork->length + size > maxnonfragsize - fragheaderlen) {
1248                 ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
1249                                mtu - (opt ? opt->optlen : 0));
1250                 return -EMSGSIZE;
1251         }
1252 
1253         skb = skb_peek_tail(&sk->sk_write_queue);
1254         if (!skb)
1255                 return -EINVAL;
1256 
1257         if ((size + skb->len > mtu) &&
1258             (sk->sk_protocol == IPPROTO_UDP) &&
1259             (rt->dst.dev->features & NETIF_F_UFO)) {
1260                 if (skb->ip_summed != CHECKSUM_PARTIAL)
1261                         return -EOPNOTSUPP;
1262 
1263                 skb_shinfo(skb)->gso_size = mtu - fragheaderlen;
1264                 skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
1265         }
1266         cork->length += size;
1267 
1268         while (size > 0) {
1269                 if (skb_is_gso(skb)) {
1270                         len = size;
1271                 } else {
1272 
1273                         /* Check if the remaining data fits into current packet. */
1274                         len = mtu - skb->len;
1275                         if (len < size)
1276                                 len = maxfraglen - skb->len;
1277                 }
1278                 if (len <= 0) {
1279                         struct sk_buff *skb_prev;
1280                         int alloclen;
1281 
1282                         skb_prev = skb;
1283                         fraggap = skb_prev->len - maxfraglen;
1284 
1285                         alloclen = fragheaderlen + hh_len + fraggap + 15;
1286                         skb = sock_wmalloc(sk, alloclen, 1, sk->sk_allocation);
1287                         if (unlikely(!skb)) {
1288                                 err = -ENOBUFS;
1289                                 goto error;
1290                         }
1291 
1292                         /*
1293                          *      Fill in the control structures
1294                          */
1295                         skb->ip_summed = CHECKSUM_NONE;
1296                         skb->csum = 0;
1297                         skb_reserve(skb, hh_len);
1298 
1299                         /*
1300                          *      Find where to start putting bytes.
1301                          */
1302                         skb_put(skb, fragheaderlen + fraggap);
1303                         skb_reset_network_header(skb);
1304                         skb->transport_header = (skb->network_header +
1305                                                  fragheaderlen);
1306                         if (fraggap) {
1307                                 skb->csum = skb_copy_and_csum_bits(skb_prev,
1308                                                                    maxfraglen,
1309                                                     skb_transport_header(skb),
1310                                                                    fraggap, 0);
1311                                 skb_prev->csum = csum_sub(skb_prev->csum,
1312                                                           skb->csum);
1313                                 pskb_trim_unique(skb_prev, maxfraglen);
1314                         }
1315 
1316                         /*
1317                          * Put the packet on the pending queue.
1318                          */
1319                         __skb_queue_tail(&sk->sk_write_queue, skb);
1320                         continue;
1321                 }
1322 
1323                 if (len > size)
1324                         len = size;
1325 
1326                 if (skb_append_pagefrags(skb, page, offset, len)) {
1327                         err = -EMSGSIZE;
1328                         goto error;
1329                 }
1330 
1331                 if (skb->ip_summed == CHECKSUM_NONE) {
1332                         __wsum csum;
1333                         csum = csum_page(page, offset, len);
1334                         skb->csum = csum_block_add(skb->csum, csum, skb->len);
1335                 }
1336 
1337                 skb->len += len;
1338                 skb->data_len += len;
1339                 skb->truesize += len;
1340                 atomic_add(len, &sk->sk_wmem_alloc);
1341                 offset += len;
1342                 size -= len;
1343         }
1344         return 0;
1345 
1346 error:
1347         cork->length -= size;
1348         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1349         return err;
1350 }
1351 
1352 static void ip_cork_release(struct inet_cork *cork)
1353 {
1354         cork->flags &= ~IPCORK_OPT;
1355         kfree(cork->opt);
1356         cork->opt = NULL;
1357         dst_release(cork->dst);
1358         cork->dst = NULL;
1359 }
1360 
1361 /*
1362  *      Combined all pending IP fragments on the socket as one IP datagram
1363  *      and push them out.
1364  */
1365 struct sk_buff *__ip_make_skb(struct sock *sk,
1366                               struct flowi4 *fl4,
1367                               struct sk_buff_head *queue,
1368                               struct inet_cork *cork)
1369 {
1370         struct sk_buff *skb, *tmp_skb;
1371         struct sk_buff **tail_skb;
1372         struct inet_sock *inet = inet_sk(sk);
1373         struct net *net = sock_net(sk);
1374         struct ip_options *opt = NULL;
1375         struct rtable *rt = (struct rtable *)cork->dst;
1376         struct iphdr *iph;
1377         __be16 df = 0;
1378         __u8 ttl;
1379 
1380         skb = __skb_dequeue(queue);
1381         if (!skb)
1382                 goto out;
1383         tail_skb = &(skb_shinfo(skb)->frag_list);
1384 
1385         /* move skb->data to ip header from ext header */
1386         if (skb->data < skb_network_header(skb))
1387                 __skb_pull(skb, skb_network_offset(skb));
1388         while ((tmp_skb = __skb_dequeue(queue)) != NULL) {
1389                 __skb_pull(tmp_skb, skb_network_header_len(skb));
1390                 *tail_skb = tmp_skb;
1391                 tail_skb = &(tmp_skb->next);
1392                 skb->len += tmp_skb->len;
1393                 skb->data_len += tmp_skb->len;
1394                 skb->truesize += tmp_skb->truesize;
1395                 tmp_skb->destructor = NULL;
1396                 tmp_skb->sk = NULL;
1397         }
1398 
1399         /* Unless user demanded real pmtu discovery (IP_PMTUDISC_DO), we allow
1400          * to fragment the frame generated here. No matter, what transforms
1401          * how transforms change size of the packet, it will come out.
1402          */
1403         skb->ignore_df = ip_sk_ignore_df(sk);
1404 
1405         /* DF bit is set when we want to see DF on outgoing frames.
1406          * If ignore_df is set too, we still allow to fragment this frame
1407          * locally. */
1408         if (inet->pmtudisc == IP_PMTUDISC_DO ||
1409             inet->pmtudisc == IP_PMTUDISC_PROBE ||
1410             (skb->len <= dst_mtu(&rt->dst) &&
1411              ip_dont_fragment(sk, &rt->dst)))
1412                 df = htons(IP_DF);
1413 
1414         if (cork->flags & IPCORK_OPT)
1415                 opt = cork->opt;
1416 
1417         if (cork->ttl != 0)
1418                 ttl = cork->ttl;
1419         else if (rt->rt_type == RTN_MULTICAST)
1420                 ttl = inet->mc_ttl;
1421         else
1422                 ttl = ip_select_ttl(inet, &rt->dst);
1423 
1424         iph = ip_hdr(skb);
1425         iph->version = 4;
1426         iph->ihl = 5;
1427         iph->tos = (cork->tos != -1) ? cork->tos : inet->tos;
1428         iph->frag_off = df;
1429         iph->ttl = ttl;
1430         iph->protocol = sk->sk_protocol;
1431         ip_copy_addrs(iph, fl4);
1432         ip_select_ident(net, skb, sk);
1433 
1434         if (opt) {
1435                 iph->ihl += opt->optlen>>2;
1436                 ip_options_build(skb, opt, cork->addr, rt, 0);
1437         }
1438 
1439         skb->priority = (cork->tos != -1) ? cork->priority: sk->sk_priority;
1440         skb->mark = sk->sk_mark;
1441         /*
1442          * Steal rt from cork.dst to avoid a pair of atomic_inc/atomic_dec
1443          * on dst refcount
1444          */
1445         cork->dst = NULL;
1446         skb_dst_set(skb, &rt->dst);
1447 
1448         if (iph->protocol == IPPROTO_ICMP)
1449                 icmp_out_count(net, ((struct icmphdr *)
1450                         skb_transport_header(skb))->type);
1451 
1452         ip_cork_release(cork);
1453 out:
1454         return skb;
1455 }
1456 
1457 int ip_send_skb(struct net *net, struct sk_buff *skb)
1458 {
1459         int err;
1460 
1461         err = ip_local_out(net, skb->sk, skb);
1462         if (err) {
1463                 if (err > 0)
1464                         err = net_xmit_errno(err);
1465                 if (err)
1466                         IP_INC_STATS(net, IPSTATS_MIB_OUTDISCARDS);
1467         }
1468 
1469         return err;
1470 }
1471 
1472 int ip_push_pending_frames(struct sock *sk, struct flowi4 *fl4)
1473 {
1474         struct sk_buff *skb;
1475 
1476         skb = ip_finish_skb(sk, fl4);
1477         if (!skb)
1478                 return 0;
1479 
1480         /* Netfilter gets whole the not fragmented skb. */
1481         return ip_send_skb(sock_net(sk), skb);
1482 }
1483 
1484 /*
1485  *      Throw away all pending data on the socket.
1486  */
1487 static void __ip_flush_pending_frames(struct sock *sk,
1488                                       struct sk_buff_head *queue,
1489                                       struct inet_cork *cork)
1490 {
1491         struct sk_buff *skb;
1492 
1493         while ((skb = __skb_dequeue_tail(queue)) != NULL)
1494                 kfree_skb(skb);
1495 
1496         ip_cork_release(cork);
1497 }
1498 
1499 void ip_flush_pending_frames(struct sock *sk)
1500 {
1501         __ip_flush_pending_frames(sk, &sk->sk_write_queue, &inet_sk(sk)->cork.base);
1502 }
1503 
1504 struct sk_buff *ip_make_skb(struct sock *sk,
1505                             struct flowi4 *fl4,
1506                             int getfrag(void *from, char *to, int offset,
1507                                         int len, int odd, struct sk_buff *skb),
1508                             void *from, int length, int transhdrlen,
1509                             struct ipcm_cookie *ipc, struct rtable **rtp,
1510                             unsigned int flags)
1511 {
1512         struct inet_cork cork;
1513         struct sk_buff_head queue;
1514         int err;
1515 
1516         if (flags & MSG_PROBE)
1517                 return NULL;
1518 
1519         __skb_queue_head_init(&queue);
1520 
1521         cork.flags = 0;
1522         cork.addr = 0;
1523         cork.opt = NULL;
1524         err = ip_setup_cork(sk, &cork, ipc, rtp);
1525         if (err)
1526                 return ERR_PTR(err);
1527 
1528         err = __ip_append_data(sk, fl4, &queue, &cork,
1529                                &current->task_frag, getfrag,
1530                                from, length, transhdrlen, flags);
1531         if (err) {
1532                 __ip_flush_pending_frames(sk, &queue, &cork);
1533                 return ERR_PTR(err);
1534         }
1535 
1536         return __ip_make_skb(sk, fl4, &queue, &cork);
1537 }
1538 
1539 /*
1540  *      Fetch data from kernel space and fill in checksum if needed.
1541  */
1542 static int ip_reply_glue_bits(void *dptr, char *to, int offset,
1543                               int len, int odd, struct sk_buff *skb)
1544 {
1545         __wsum csum;
1546 
1547         csum = csum_partial_copy_nocheck(dptr+offset, to, len, 0);
1548         skb->csum = csum_block_add(skb->csum, csum, odd);
1549         return 0;
1550 }
1551 
1552 /*
1553  *      Generic function to send a packet as reply to another packet.
1554  *      Used to send some TCP resets/acks so far.
1555  */
1556 void ip_send_unicast_reply(struct sock *sk, struct sk_buff *skb,
1557                            const struct ip_options *sopt,
1558                            __be32 daddr, __be32 saddr,
1559                            const struct ip_reply_arg *arg,
1560                            unsigned int len)
1561 {
1562         struct ip_options_data replyopts;
1563         struct ipcm_cookie ipc;
1564         struct flowi4 fl4;
1565         struct rtable *rt = skb_rtable(skb);
1566         struct net *net = sock_net(sk);
1567         struct sk_buff *nskb;
1568         int err;
1569         int oif;
1570 
1571         if (__ip_options_echo(&replyopts.opt.opt, skb, sopt))
1572                 return;
1573 
1574         ipc.addr = daddr;
1575         ipc.opt = NULL;
1576         ipc.tx_flags = 0;
1577         ipc.ttl = 0;
1578         ipc.tos = -1;
1579 
1580         if (replyopts.opt.opt.optlen) {
1581                 ipc.opt = &replyopts.opt;
1582 
1583                 if (replyopts.opt.opt.srr)
1584                         daddr = replyopts.opt.opt.faddr;
1585         }
1586 
1587         oif = arg->bound_dev_if;
1588         if (!oif && netif_index_is_l3_master(net, skb->skb_iif))
1589                 oif = skb->skb_iif;
1590 
1591         flowi4_init_output(&fl4, oif,
1592                            IP4_REPLY_MARK(net, skb->mark),
1593                            RT_TOS(arg->tos),
1594                            RT_SCOPE_UNIVERSE, ip_hdr(skb)->protocol,
1595                            ip_reply_arg_flowi_flags(arg),
1596                            daddr, saddr,
1597                            tcp_hdr(skb)->source, tcp_hdr(skb)->dest);
1598         security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
1599         rt = ip_route_output_key(net, &fl4);
1600         if (IS_ERR(rt))
1601                 return;
1602 
1603         inet_sk(sk)->tos = arg->tos;
1604 
1605         sk->sk_priority = skb->priority;
1606         sk->sk_protocol = ip_hdr(skb)->protocol;
1607         sk->sk_bound_dev_if = arg->bound_dev_if;
1608         sk->sk_sndbuf = sysctl_wmem_default;
1609         err = ip_append_data(sk, &fl4, ip_reply_glue_bits, arg->iov->iov_base,
1610                              len, 0, &ipc, &rt, MSG_DONTWAIT);
1611         if (unlikely(err)) {
1612                 ip_flush_pending_frames(sk);
1613                 goto out;
1614         }
1615 
1616         nskb = skb_peek(&sk->sk_write_queue);
1617         if (nskb) {
1618                 if (arg->csumoffset >= 0)
1619                         *((__sum16 *)skb_transport_header(nskb) +
1620                           arg->csumoffset) = csum_fold(csum_add(nskb->csum,
1621                                                                 arg->csum));
1622                 nskb->ip_summed = CHECKSUM_NONE;
1623                 ip_push_pending_frames(sk, &fl4);
1624         }
1625 out:
1626         ip_rt_put(rt);
1627 }
1628 
1629 void __init ip_init(void)
1630 {
1631         ip_rt_init();
1632         inet_initpeers();
1633 
1634 #if defined(CONFIG_IP_MULTICAST)
1635         igmp_mc_init();
1636 #endif
1637 }
1638 

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