Version:  2.0.40 2.2.26 2.4.37 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1 4.2 4.3 4.4

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 <linux/igmp.h>
 77 #include <linux/netfilter_ipv4.h>
 78 #include <linux/netfilter_bridge.h>
 79 #include <linux/mroute.h>
 80 #include <linux/netlink.h>
 81 #include <linux/tcp.h>
 82 
 83 int sysctl_ip_default_ttl __read_mostly = IPDEFTTL;
 84 EXPORT_SYMBOL(sysctl_ip_default_ttl);
 85 
 86 static int
 87 ip_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
 88             unsigned int mtu,
 89             int (*output)(struct net *, struct sock *, struct sk_buff *));
 90 
 91 /* Generate a checksum for an outgoing IP datagram. */
 92 void ip_send_check(struct iphdr *iph)
 93 {
 94         iph->check = 0;
 95         iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
 96 }
 97 EXPORT_SYMBOL(ip_send_check);
 98 
 99 int __ip_local_out(struct net *net, struct sock *sk, struct sk_buff *skb)
100 {
101         struct iphdr *iph = ip_hdr(skb);
102 
103         iph->tot_len = htons(skb->len);
104         ip_send_check(iph);
105         return nf_hook(NFPROTO_IPV4, NF_INET_LOCAL_OUT,
106                        net, sk, skb, NULL, skb_dst(skb)->dev,
107                        dst_output);
108 }
109 
110 int ip_local_out(struct net *net, struct sock *sk, struct sk_buff *skb)
111 {
112         int err;
113 
114         err = __ip_local_out(net, sk, skb);
115         if (likely(err == 1))
116                 err = dst_output(net, sk, skb);
117 
118         return err;
119 }
120 EXPORT_SYMBOL_GPL(ip_local_out);
121 
122 static inline int ip_select_ttl(struct inet_sock *inet, struct dst_entry *dst)
123 {
124         int ttl = inet->uc_ttl;
125 
126         if (ttl < 0)
127                 ttl = ip4_dst_hoplimit(dst);
128         return ttl;
129 }
130 
131 /*
132  *              Add an ip header to a skbuff and send it out.
133  *
134  */
135 int ip_build_and_send_pkt(struct sk_buff *skb, const struct sock *sk,
136                           __be32 saddr, __be32 daddr, struct ip_options_rcu *opt)
137 {
138         struct inet_sock *inet = inet_sk(sk);
139         struct rtable *rt = skb_rtable(skb);
140         struct net *net = sock_net(sk);
141         struct iphdr *iph;
142 
143         /* Build the IP header. */
144         skb_push(skb, sizeof(struct iphdr) + (opt ? opt->opt.optlen : 0));
145         skb_reset_network_header(skb);
146         iph = ip_hdr(skb);
147         iph->version  = 4;
148         iph->ihl      = 5;
149         iph->tos      = inet->tos;
150         iph->ttl      = ip_select_ttl(inet, &rt->dst);
151         iph->daddr    = (opt && opt->opt.srr ? opt->opt.faddr : daddr);
152         iph->saddr    = saddr;
153         iph->protocol = sk->sk_protocol;
154         if (ip_dont_fragment(sk, &rt->dst)) {
155                 iph->frag_off = htons(IP_DF);
156                 iph->id = 0;
157         } else {
158                 iph->frag_off = 0;
159                 __ip_select_ident(net, iph, 1);
160         }
161 
162         if (opt && opt->opt.optlen) {
163                 iph->ihl += opt->opt.optlen>>2;
164                 ip_options_build(skb, &opt->opt, daddr, rt, 0);
165         }
166 
167         skb->priority = sk->sk_priority;
168         skb->mark = sk->sk_mark;
169 
170         /* Send it out. */
171         return ip_local_out(net, skb->sk, skb);
172 }
173 EXPORT_SYMBOL_GPL(ip_build_and_send_pkt);
174 
175 static int ip_finish_output2(struct net *net, struct sock *sk, struct sk_buff *skb)
176 {
177         struct dst_entry *dst = skb_dst(skb);
178         struct rtable *rt = (struct rtable *)dst;
179         struct net_device *dev = dst->dev;
180         unsigned int hh_len = LL_RESERVED_SPACE(dev);
181         struct neighbour *neigh;
182         u32 nexthop;
183 
184         if (rt->rt_type == RTN_MULTICAST) {
185                 IP_UPD_PO_STATS(net, IPSTATS_MIB_OUTMCAST, skb->len);
186         } else if (rt->rt_type == RTN_BROADCAST)
187                 IP_UPD_PO_STATS(net, IPSTATS_MIB_OUTBCAST, skb->len);
188 
189         /* Be paranoid, rather than too clever. */
190         if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) {
191                 struct sk_buff *skb2;
192 
193                 skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev));
194                 if (!skb2) {
195                         kfree_skb(skb);
196                         return -ENOMEM;
197                 }
198                 if (skb->sk)
199                         skb_set_owner_w(skb2, skb->sk);
200                 consume_skb(skb);
201                 skb = skb2;
202         }
203 
204         rcu_read_lock_bh();
205         nexthop = (__force u32) rt_nexthop(rt, ip_hdr(skb)->daddr);
206         neigh = __ipv4_neigh_lookup_noref(dev, nexthop);
207         if (unlikely(!neigh))
208                 neigh = __neigh_create(&arp_tbl, &nexthop, dev, false);
209         if (!IS_ERR(neigh)) {
210                 int res = dst_neigh_output(dst, neigh, skb);
211 
212                 rcu_read_unlock_bh();
213                 return res;
214         }
215         rcu_read_unlock_bh();
216 
217         net_dbg_ratelimited("%s: No header cache and no neighbour!\n",
218                             __func__);
219         kfree_skb(skb);
220         return -EINVAL;
221 }
222 
223 static int ip_finish_output_gso(struct net *net, struct sock *sk,
224                                 struct sk_buff *skb, unsigned int mtu)
225 {
226         netdev_features_t features;
227         struct sk_buff *segs;
228         int ret = 0;
229 
230         /* common case: locally created skb or seglen is <= mtu */
231         if (((IPCB(skb)->flags & IPSKB_FORWARDED) == 0) ||
232               skb_gso_network_seglen(skb) <= mtu)
233                 return ip_finish_output2(net, sk, skb);
234 
235         /* Slowpath -  GSO segment length is exceeding the dst MTU.
236          *
237          * This can happen in two cases:
238          * 1) TCP GRO packet, DF bit not set
239          * 2) skb arrived via virtio-net, we thus get TSO/GSO skbs directly
240          * from host network stack.
241          */
242         features = netif_skb_features(skb);
243         segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK);
244         if (IS_ERR_OR_NULL(segs)) {
245                 kfree_skb(skb);
246                 return -ENOMEM;
247         }
248 
249         consume_skb(skb);
250 
251         do {
252                 struct sk_buff *nskb = segs->next;
253                 int err;
254 
255                 segs->next = NULL;
256                 err = ip_fragment(net, sk, segs, mtu, ip_finish_output2);
257 
258                 if (err && ret == 0)
259                         ret = err;
260                 segs = nskb;
261         } while (segs);
262 
263         return ret;
264 }
265 
266 static int ip_finish_output(struct net *net, struct sock *sk, struct sk_buff *skb)
267 {
268         unsigned int mtu;
269 
270 #if defined(CONFIG_NETFILTER) && defined(CONFIG_XFRM)
271         /* Policy lookup after SNAT yielded a new policy */
272         if (skb_dst(skb)->xfrm) {
273                 IPCB(skb)->flags |= IPSKB_REROUTED;
274                 return dst_output(net, sk, skb);
275         }
276 #endif
277         mtu = ip_skb_dst_mtu(skb);
278         if (skb_is_gso(skb))
279                 return ip_finish_output_gso(net, sk, skb, mtu);
280 
281         if (skb->len > mtu || (IPCB(skb)->flags & IPSKB_FRAG_PMTU))
282                 return ip_fragment(net, sk, skb, mtu, ip_finish_output2);
283 
284         return ip_finish_output2(net, sk, skb);
285 }
286 
287 int ip_mc_output(struct net *net, struct sock *sk, struct sk_buff *skb)
288 {
289         struct rtable *rt = skb_rtable(skb);
290         struct net_device *dev = rt->dst.dev;
291 
292         /*
293          *      If the indicated interface is up and running, send the packet.
294          */
295         IP_UPD_PO_STATS(net, IPSTATS_MIB_OUT, skb->len);
296 
297         skb->dev = dev;
298         skb->protocol = htons(ETH_P_IP);
299 
300         /*
301          *      Multicasts are looped back for other local users
302          */
303 
304         if (rt->rt_flags&RTCF_MULTICAST) {
305                 if (sk_mc_loop(sk)
306 #ifdef CONFIG_IP_MROUTE
307                 /* Small optimization: do not loopback not local frames,
308                    which returned after forwarding; they will be  dropped
309                    by ip_mr_input in any case.
310                    Note, that local frames are looped back to be delivered
311                    to local recipients.
312 
313                    This check is duplicated in ip_mr_input at the moment.
314                  */
315                     &&
316                     ((rt->rt_flags & RTCF_LOCAL) ||
317                      !(IPCB(skb)->flags & IPSKB_FORWARDED))
318 #endif
319                    ) {
320                         struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
321                         if (newskb)
322                                 NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING,
323                                         net, sk, newskb, NULL, newskb->dev,
324                                         dev_loopback_xmit);
325                 }
326 
327                 /* Multicasts with ttl 0 must not go beyond the host */
328 
329                 if (ip_hdr(skb)->ttl == 0) {
330                         kfree_skb(skb);
331                         return 0;
332                 }
333         }
334 
335         if (rt->rt_flags&RTCF_BROADCAST) {
336                 struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
337                 if (newskb)
338                         NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING,
339                                 net, sk, newskb, NULL, newskb->dev,
340                                 dev_loopback_xmit);
341         }
342 
343         return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
344                             net, sk, skb, NULL, skb->dev,
345                             ip_finish_output,
346                             !(IPCB(skb)->flags & IPSKB_REROUTED));
347 }
348 
349 int ip_output(struct net *net, struct sock *sk, struct sk_buff *skb)
350 {
351         struct net_device *dev = skb_dst(skb)->dev;
352 
353         IP_UPD_PO_STATS(net, IPSTATS_MIB_OUT, skb->len);
354 
355         skb->dev = dev;
356         skb->protocol = htons(ETH_P_IP);
357 
358         return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
359                             net, sk, skb, NULL, dev,
360                             ip_finish_output,
361                             !(IPCB(skb)->flags & IPSKB_REROUTED));
362 }
363 
364 /*
365  * copy saddr and daddr, possibly using 64bit load/stores
366  * Equivalent to :
367  *   iph->saddr = fl4->saddr;
368  *   iph->daddr = fl4->daddr;
369  */
370 static void ip_copy_addrs(struct iphdr *iph, const struct flowi4 *fl4)
371 {
372         BUILD_BUG_ON(offsetof(typeof(*fl4), daddr) !=
373                      offsetof(typeof(*fl4), saddr) + sizeof(fl4->saddr));
374         memcpy(&iph->saddr, &fl4->saddr,
375                sizeof(fl4->saddr) + sizeof(fl4->daddr));
376 }
377 
378 /* Note: skb->sk can be different from sk, in case of tunnels */
379 int ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl)
380 {
381         struct inet_sock *inet = inet_sk(sk);
382         struct net *net = sock_net(sk);
383         struct ip_options_rcu *inet_opt;
384         struct flowi4 *fl4;
385         struct rtable *rt;
386         struct iphdr *iph;
387         int res;
388 
389         /* Skip all of this if the packet is already routed,
390          * f.e. by something like SCTP.
391          */
392         rcu_read_lock();
393         inet_opt = rcu_dereference(inet->inet_opt);
394         fl4 = &fl->u.ip4;
395         rt = skb_rtable(skb);
396         if (rt)
397                 goto packet_routed;
398 
399         /* Make sure we can route this packet. */
400         rt = (struct rtable *)__sk_dst_check(sk, 0);
401         if (!rt) {
402                 __be32 daddr;
403 
404                 /* Use correct destination address if we have options. */
405                 daddr = inet->inet_daddr;
406                 if (inet_opt && inet_opt->opt.srr)
407                         daddr = inet_opt->opt.faddr;
408 
409                 /* If this fails, retransmit mechanism of transport layer will
410                  * keep trying until route appears or the connection times
411                  * itself out.
412                  */
413                 rt = ip_route_output_ports(net, fl4, sk,
414                                            daddr, inet->inet_saddr,
415                                            inet->inet_dport,
416                                            inet->inet_sport,
417                                            sk->sk_protocol,
418                                            RT_CONN_FLAGS(sk),
419                                            sk->sk_bound_dev_if);
420                 if (IS_ERR(rt))
421                         goto no_route;
422                 sk_setup_caps(sk, &rt->dst);
423         }
424         skb_dst_set_noref(skb, &rt->dst);
425 
426 packet_routed:
427         if (inet_opt && inet_opt->opt.is_strictroute && rt->rt_uses_gateway)
428                 goto no_route;
429 
430         /* OK, we know where to send it, allocate and build IP header. */
431         skb_push(skb, sizeof(struct iphdr) + (inet_opt ? inet_opt->opt.optlen : 0));
432         skb_reset_network_header(skb);
433         iph = ip_hdr(skb);
434         *((__be16 *)iph) = htons((4 << 12) | (5 << 8) | (inet->tos & 0xff));
435         if (ip_dont_fragment(sk, &rt->dst) && !skb->ignore_df)
436                 iph->frag_off = htons(IP_DF);
437         else
438                 iph->frag_off = 0;
439         iph->ttl      = ip_select_ttl(inet, &rt->dst);
440         iph->protocol = sk->sk_protocol;
441         ip_copy_addrs(iph, fl4);
442 
443         /* Transport layer set skb->h.foo itself. */
444 
445         if (inet_opt && inet_opt->opt.optlen) {
446                 iph->ihl += inet_opt->opt.optlen >> 2;
447                 ip_options_build(skb, &inet_opt->opt, inet->inet_daddr, rt, 0);
448         }
449 
450         ip_select_ident_segs(net, skb, sk,
451                              skb_shinfo(skb)->gso_segs ?: 1);
452 
453         /* TODO : should we use skb->sk here instead of sk ? */
454         skb->priority = sk->sk_priority;
455         skb->mark = sk->sk_mark;
456 
457         res = ip_local_out(net, sk, skb);
458         rcu_read_unlock();
459         return res;
460 
461 no_route:
462         rcu_read_unlock();
463         IP_INC_STATS(net, IPSTATS_MIB_OUTNOROUTES);
464         kfree_skb(skb);
465         return -EHOSTUNREACH;
466 }
467 EXPORT_SYMBOL(ip_queue_xmit);
468 
469 static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
470 {
471         to->pkt_type = from->pkt_type;
472         to->priority = from->priority;
473         to->protocol = from->protocol;
474         skb_dst_drop(to);
475         skb_dst_copy(to, from);
476         to->dev = from->dev;
477         to->mark = from->mark;
478 
479         /* Copy the flags to each fragment. */
480         IPCB(to)->flags = IPCB(from)->flags;
481 
482 #ifdef CONFIG_NET_SCHED
483         to->tc_index = from->tc_index;
484 #endif
485         nf_copy(to, from);
486 #if defined(CONFIG_IP_VS) || defined(CONFIG_IP_VS_MODULE)
487         to->ipvs_property = from->ipvs_property;
488 #endif
489         skb_copy_secmark(to, from);
490 }
491 
492 static int ip_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
493                        unsigned int mtu,
494                        int (*output)(struct net *, struct sock *, struct sk_buff *))
495 {
496         struct iphdr *iph = ip_hdr(skb);
497 
498         if ((iph->frag_off & htons(IP_DF)) == 0)
499                 return ip_do_fragment(net, sk, skb, output);
500 
501         if (unlikely(!skb->ignore_df ||
502                      (IPCB(skb)->frag_max_size &&
503                       IPCB(skb)->frag_max_size > mtu))) {
504                 IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
505                 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
506                           htonl(mtu));
507                 kfree_skb(skb);
508                 return -EMSGSIZE;
509         }
510 
511         return ip_do_fragment(net, sk, skb, output);
512 }
513 
514 /*
515  *      This IP datagram is too large to be sent in one piece.  Break it up into
516  *      smaller pieces (each of size equal to IP header plus
517  *      a block of the data of the original IP data part) that will yet fit in a
518  *      single device frame, and queue such a frame for sending.
519  */
520 
521 int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
522                    int (*output)(struct net *, struct sock *, struct sk_buff *))
523 {
524         struct iphdr *iph;
525         int ptr;
526         struct net_device *dev;
527         struct sk_buff *skb2;
528         unsigned int mtu, hlen, left, len, ll_rs;
529         int offset;
530         __be16 not_last_frag;
531         struct rtable *rt = skb_rtable(skb);
532         int err = 0;
533 
534         dev = rt->dst.dev;
535 
536         /* for offloaded checksums cleanup checksum before fragmentation */
537         if (skb->ip_summed == CHECKSUM_PARTIAL &&
538             (err = skb_checksum_help(skb)))
539                 goto fail;
540 
541         /*
542          *      Point into the IP datagram header.
543          */
544 
545         iph = ip_hdr(skb);
546 
547         mtu = ip_skb_dst_mtu(skb);
548         if (IPCB(skb)->frag_max_size && IPCB(skb)->frag_max_size < mtu)
549                 mtu = IPCB(skb)->frag_max_size;
550 
551         /*
552          *      Setup starting values.
553          */
554 
555         hlen = iph->ihl * 4;
556         mtu = mtu - hlen;       /* Size of data space */
557         IPCB(skb)->flags |= IPSKB_FRAG_COMPLETE;
558 
559         /* When frag_list is given, use it. First, check its validity:
560          * some transformers could create wrong frag_list or break existing
561          * one, it is not prohibited. In this case fall back to copying.
562          *
563          * LATER: this step can be merged to real generation of fragments,
564          * we can switch to copy when see the first bad fragment.
565          */
566         if (skb_has_frag_list(skb)) {
567                 struct sk_buff *frag, *frag2;
568                 int first_len = skb_pagelen(skb);
569 
570                 if (first_len - hlen > mtu ||
571                     ((first_len - hlen) & 7) ||
572                     ip_is_fragment(iph) ||
573                     skb_cloned(skb))
574                         goto slow_path;
575 
576                 skb_walk_frags(skb, frag) {
577                         /* Correct geometry. */
578                         if (frag->len > mtu ||
579                             ((frag->len & 7) && frag->next) ||
580                             skb_headroom(frag) < hlen)
581                                 goto slow_path_clean;
582 
583                         /* Partially cloned skb? */
584                         if (skb_shared(frag))
585                                 goto slow_path_clean;
586 
587                         BUG_ON(frag->sk);
588                         if (skb->sk) {
589                                 frag->sk = skb->sk;
590                                 frag->destructor = sock_wfree;
591                         }
592                         skb->truesize -= frag->truesize;
593                 }
594 
595                 /* Everything is OK. Generate! */
596 
597                 err = 0;
598                 offset = 0;
599                 frag = skb_shinfo(skb)->frag_list;
600                 skb_frag_list_init(skb);
601                 skb->data_len = first_len - skb_headlen(skb);
602                 skb->len = first_len;
603                 iph->tot_len = htons(first_len);
604                 iph->frag_off = htons(IP_MF);
605                 ip_send_check(iph);
606 
607                 for (;;) {
608                         /* Prepare header of the next frame,
609                          * before previous one went down. */
610                         if (frag) {
611                                 frag->ip_summed = CHECKSUM_NONE;
612                                 skb_reset_transport_header(frag);
613                                 __skb_push(frag, hlen);
614                                 skb_reset_network_header(frag);
615                                 memcpy(skb_network_header(frag), iph, hlen);
616                                 iph = ip_hdr(frag);
617                                 iph->tot_len = htons(frag->len);
618                                 ip_copy_metadata(frag, skb);
619                                 if (offset == 0)
620                                         ip_options_fragment(frag);
621                                 offset += skb->len - hlen;
622                                 iph->frag_off = htons(offset>>3);
623                                 if (frag->next)
624                                         iph->frag_off |= htons(IP_MF);
625                                 /* Ready, complete checksum */
626                                 ip_send_check(iph);
627                         }
628 
629                         err = output(net, sk, skb);
630 
631                         if (!err)
632                                 IP_INC_STATS(net, IPSTATS_MIB_FRAGCREATES);
633                         if (err || !frag)
634                                 break;
635 
636                         skb = frag;
637                         frag = skb->next;
638                         skb->next = NULL;
639                 }
640 
641                 if (err == 0) {
642                         IP_INC_STATS(net, IPSTATS_MIB_FRAGOKS);
643                         return 0;
644                 }
645 
646                 while (frag) {
647                         skb = frag->next;
648                         kfree_skb(frag);
649                         frag = skb;
650                 }
651                 IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
652                 return err;
653 
654 slow_path_clean:
655                 skb_walk_frags(skb, frag2) {
656                         if (frag2 == frag)
657                                 break;
658                         frag2->sk = NULL;
659                         frag2->destructor = NULL;
660                         skb->truesize += frag2->truesize;
661                 }
662         }
663 
664 slow_path:
665         iph = ip_hdr(skb);
666 
667         left = skb->len - hlen;         /* Space per frame */
668         ptr = hlen;             /* Where to start from */
669 
670         ll_rs = LL_RESERVED_SPACE(rt->dst.dev);
671 
672         /*
673          *      Fragment the datagram.
674          */
675 
676         offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3;
677         not_last_frag = iph->frag_off & htons(IP_MF);
678 
679         /*
680          *      Keep copying data until we run out.
681          */
682 
683         while (left > 0) {
684                 len = left;
685                 /* IF: it doesn't fit, use 'mtu' - the data space left */
686                 if (len > mtu)
687                         len = mtu;
688                 /* IF: we are not sending up to and including the packet end
689                    then align the next start on an eight byte boundary */
690                 if (len < left) {
691                         len &= ~7;
692                 }
693 
694                 /* Allocate buffer */
695                 skb2 = alloc_skb(len + hlen + ll_rs, GFP_ATOMIC);
696                 if (!skb2) {
697                         err = -ENOMEM;
698                         goto fail;
699                 }
700 
701                 /*
702                  *      Set up data on packet
703                  */
704 
705                 ip_copy_metadata(skb2, skb);
706                 skb_reserve(skb2, ll_rs);
707                 skb_put(skb2, len + hlen);
708                 skb_reset_network_header(skb2);
709                 skb2->transport_header = skb2->network_header + hlen;
710 
711                 /*
712                  *      Charge the memory for the fragment to any owner
713                  *      it might possess
714                  */
715 
716                 if (skb->sk)
717                         skb_set_owner_w(skb2, skb->sk);
718 
719                 /*
720                  *      Copy the packet header into the new buffer.
721                  */
722 
723                 skb_copy_from_linear_data(skb, skb_network_header(skb2), hlen);
724 
725                 /*
726                  *      Copy a block of the IP datagram.
727                  */
728                 if (skb_copy_bits(skb, ptr, skb_transport_header(skb2), len))
729                         BUG();
730                 left -= len;
731 
732                 /*
733                  *      Fill in the new header fields.
734                  */
735                 iph = ip_hdr(skb2);
736                 iph->frag_off = htons((offset >> 3));
737 
738                 if (IPCB(skb)->flags & IPSKB_FRAG_PMTU)
739                         iph->frag_off |= htons(IP_DF);
740 
741                 /* ANK: dirty, but effective trick. Upgrade options only if
742                  * the segment to be fragmented was THE FIRST (otherwise,
743                  * options are already fixed) and make it ONCE
744                  * on the initial skb, so that all the following fragments
745                  * will inherit fixed options.
746                  */
747                 if (offset == 0)
748                         ip_options_fragment(skb);
749 
750                 /*
751                  *      Added AC : If we are fragmenting a fragment that's not the
752                  *                 last fragment then keep MF on each bit
753                  */
754                 if (left > 0 || not_last_frag)
755                         iph->frag_off |= htons(IP_MF);
756                 ptr += len;
757                 offset += len;
758 
759                 /*
760                  *      Put this fragment into the sending queue.
761                  */
762                 iph->tot_len = htons(len + hlen);
763 
764                 ip_send_check(iph);
765 
766                 err = output(net, sk, skb2);
767                 if (err)
768                         goto fail;
769 
770                 IP_INC_STATS(net, IPSTATS_MIB_FRAGCREATES);
771         }
772         consume_skb(skb);
773         IP_INC_STATS(net, IPSTATS_MIB_FRAGOKS);
774         return err;
775 
776 fail:
777         kfree_skb(skb);
778         IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
779         return err;
780 }
781 EXPORT_SYMBOL(ip_do_fragment);
782 
783 int
784 ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
785 {
786         struct msghdr *msg = from;
787 
788         if (skb->ip_summed == CHECKSUM_PARTIAL) {
789                 if (copy_from_iter(to, len, &msg->msg_iter) != len)
790                         return -EFAULT;
791         } else {
792                 __wsum csum = 0;
793                 if (csum_and_copy_from_iter(to, len, &csum, &msg->msg_iter) != len)
794                         return -EFAULT;
795                 skb->csum = csum_block_add(skb->csum, csum, odd);
796         }
797         return 0;
798 }
799 EXPORT_SYMBOL(ip_generic_getfrag);
800 
801 static inline __wsum
802 csum_page(struct page *page, int offset, int copy)
803 {
804         char *kaddr;
805         __wsum csum;
806         kaddr = kmap(page);
807         csum = csum_partial(kaddr + offset, copy, 0);
808         kunmap(page);
809         return csum;
810 }
811 
812 static inline int ip_ufo_append_data(struct sock *sk,
813                         struct sk_buff_head *queue,
814                         int getfrag(void *from, char *to, int offset, int len,
815                                int odd, struct sk_buff *skb),
816                         void *from, int length, int hh_len, int fragheaderlen,
817                         int transhdrlen, int maxfraglen, unsigned int flags)
818 {
819         struct sk_buff *skb;
820         int err;
821 
822         /* There is support for UDP fragmentation offload by network
823          * device, so create one single skb packet containing complete
824          * udp datagram
825          */
826         skb = skb_peek_tail(queue);
827         if (!skb) {
828                 skb = sock_alloc_send_skb(sk,
829                         hh_len + fragheaderlen + transhdrlen + 20,
830                         (flags & MSG_DONTWAIT), &err);
831 
832                 if (!skb)
833                         return err;
834 
835                 /* reserve space for Hardware header */
836                 skb_reserve(skb, hh_len);
837 
838                 /* create space for UDP/IP header */
839                 skb_put(skb, fragheaderlen + transhdrlen);
840 
841                 /* initialize network header pointer */
842                 skb_reset_network_header(skb);
843 
844                 /* initialize protocol header pointer */
845                 skb->transport_header = skb->network_header + fragheaderlen;
846 
847                 skb->csum = 0;
848 
849                 __skb_queue_tail(queue, skb);
850         } else if (skb_is_gso(skb)) {
851                 goto append;
852         }
853 
854         skb->ip_summed = CHECKSUM_PARTIAL;
855         /* specify the length of each IP datagram fragment */
856         skb_shinfo(skb)->gso_size = maxfraglen - fragheaderlen;
857         skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
858 
859 append:
860         return skb_append_datato_frags(sk, skb, getfrag, from,
861                                        (length - transhdrlen));
862 }
863 
864 static int __ip_append_data(struct sock *sk,
865                             struct flowi4 *fl4,
866                             struct sk_buff_head *queue,
867                             struct inet_cork *cork,
868                             struct page_frag *pfrag,
869                             int getfrag(void *from, char *to, int offset,
870                                         int len, int odd, struct sk_buff *skb),
871                             void *from, int length, int transhdrlen,
872                             unsigned int flags)
873 {
874         struct inet_sock *inet = inet_sk(sk);
875         struct sk_buff *skb;
876 
877         struct ip_options *opt = cork->opt;
878         int hh_len;
879         int exthdrlen;
880         int mtu;
881         int copy;
882         int err;
883         int offset = 0;
884         unsigned int maxfraglen, fragheaderlen, maxnonfragsize;
885         int csummode = CHECKSUM_NONE;
886         struct rtable *rt = (struct rtable *)cork->dst;
887         u32 tskey = 0;
888 
889         skb = skb_peek_tail(queue);
890 
891         exthdrlen = !skb ? rt->dst.header_len : 0;
892         mtu = cork->fragsize;
893         if (cork->tx_flags & SKBTX_ANY_SW_TSTAMP &&
894             sk->sk_tsflags & SOF_TIMESTAMPING_OPT_ID)
895                 tskey = sk->sk_tskey++;
896 
897         hh_len = LL_RESERVED_SPACE(rt->dst.dev);
898 
899         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
900         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
901         maxnonfragsize = ip_sk_ignore_df(sk) ? 0xFFFF : mtu;
902 
903         if (cork->length + length > maxnonfragsize - fragheaderlen) {
904                 ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
905                                mtu - (opt ? opt->optlen : 0));
906                 return -EMSGSIZE;
907         }
908 
909         /*
910          * transhdrlen > 0 means that this is the first fragment and we wish
911          * it won't be fragmented in the future.
912          */
913         if (transhdrlen &&
914             length + fragheaderlen <= mtu &&
915             rt->dst.dev->features & NETIF_F_V4_CSUM &&
916             !(flags & MSG_MORE) &&
917             !exthdrlen)
918                 csummode = CHECKSUM_PARTIAL;
919 
920         cork->length += length;
921         if (((length > mtu) || (skb && skb_is_gso(skb))) &&
922             (sk->sk_protocol == IPPROTO_UDP) &&
923             (rt->dst.dev->features & NETIF_F_UFO) && !rt->dst.header_len &&
924             (sk->sk_type == SOCK_DGRAM)) {
925                 err = ip_ufo_append_data(sk, queue, getfrag, from, length,
926                                          hh_len, fragheaderlen, transhdrlen,
927                                          maxfraglen, flags);
928                 if (err)
929                         goto error;
930                 return 0;
931         }
932 
933         /* So, what's going on in the loop below?
934          *
935          * We use calculated fragment length to generate chained skb,
936          * each of segments is IP fragment ready for sending to network after
937          * adding appropriate IP header.
938          */
939 
940         if (!skb)
941                 goto alloc_new_skb;
942 
943         while (length > 0) {
944                 /* Check if the remaining data fits into current packet. */
945                 copy = mtu - skb->len;
946                 if (copy < length)
947                         copy = maxfraglen - skb->len;
948                 if (copy <= 0) {
949                         char *data;
950                         unsigned int datalen;
951                         unsigned int fraglen;
952                         unsigned int fraggap;
953                         unsigned int alloclen;
954                         struct sk_buff *skb_prev;
955 alloc_new_skb:
956                         skb_prev = skb;
957                         if (skb_prev)
958                                 fraggap = skb_prev->len - maxfraglen;
959                         else
960                                 fraggap = 0;
961 
962                         /*
963                          * If remaining data exceeds the mtu,
964                          * we know we need more fragment(s).
965                          */
966                         datalen = length + fraggap;
967                         if (datalen > mtu - fragheaderlen)
968                                 datalen = maxfraglen - fragheaderlen;
969                         fraglen = datalen + fragheaderlen;
970 
971                         if ((flags & MSG_MORE) &&
972                             !(rt->dst.dev->features&NETIF_F_SG))
973                                 alloclen = mtu;
974                         else
975                                 alloclen = fraglen;
976 
977                         alloclen += exthdrlen;
978 
979                         /* The last fragment gets additional space at tail.
980                          * Note, with MSG_MORE we overallocate on fragments,
981                          * because we have no idea what fragment will be
982                          * the last.
983                          */
984                         if (datalen == length + fraggap)
985                                 alloclen += rt->dst.trailer_len;
986 
987                         if (transhdrlen) {
988                                 skb = sock_alloc_send_skb(sk,
989                                                 alloclen + hh_len + 15,
990                                                 (flags & MSG_DONTWAIT), &err);
991                         } else {
992                                 skb = NULL;
993                                 if (atomic_read(&sk->sk_wmem_alloc) <=
994                                     2 * sk->sk_sndbuf)
995                                         skb = sock_wmalloc(sk,
996                                                            alloclen + hh_len + 15, 1,
997                                                            sk->sk_allocation);
998                                 if (unlikely(!skb))
999                                         err = -ENOBUFS;
1000                         }
1001                         if (!skb)
1002                                 goto error;
1003 
1004                         /*
1005                          *      Fill in the control structures
1006                          */
1007                         skb->ip_summed = csummode;
1008                         skb->csum = 0;
1009                         skb_reserve(skb, hh_len);
1010 
1011                         /* only the initial fragment is time stamped */
1012                         skb_shinfo(skb)->tx_flags = cork->tx_flags;
1013                         cork->tx_flags = 0;
1014                         skb_shinfo(skb)->tskey = tskey;
1015                         tskey = 0;
1016 
1017                         /*
1018                          *      Find where to start putting bytes.
1019                          */
1020                         data = skb_put(skb, fraglen + exthdrlen);
1021                         skb_set_network_header(skb, exthdrlen);
1022                         skb->transport_header = (skb->network_header +
1023                                                  fragheaderlen);
1024                         data += fragheaderlen + exthdrlen;
1025 
1026                         if (fraggap) {
1027                                 skb->csum = skb_copy_and_csum_bits(
1028                                         skb_prev, maxfraglen,
1029                                         data + transhdrlen, fraggap, 0);
1030                                 skb_prev->csum = csum_sub(skb_prev->csum,
1031                                                           skb->csum);
1032                                 data += fraggap;
1033                                 pskb_trim_unique(skb_prev, maxfraglen);
1034                         }
1035 
1036                         copy = datalen - transhdrlen - fraggap;
1037                         if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
1038                                 err = -EFAULT;
1039                                 kfree_skb(skb);
1040                                 goto error;
1041                         }
1042 
1043                         offset += copy;
1044                         length -= datalen - fraggap;
1045                         transhdrlen = 0;
1046                         exthdrlen = 0;
1047                         csummode = CHECKSUM_NONE;
1048 
1049                         /*
1050                          * Put the packet on the pending queue.
1051                          */
1052                         __skb_queue_tail(queue, skb);
1053                         continue;
1054                 }
1055 
1056                 if (copy > length)
1057                         copy = length;
1058 
1059                 if (!(rt->dst.dev->features&NETIF_F_SG)) {
1060                         unsigned int off;
1061 
1062                         off = skb->len;
1063                         if (getfrag(from, skb_put(skb, copy),
1064                                         offset, copy, off, skb) < 0) {
1065                                 __skb_trim(skb, off);
1066                                 err = -EFAULT;
1067                                 goto error;
1068                         }
1069                 } else {
1070                         int i = skb_shinfo(skb)->nr_frags;
1071 
1072                         err = -ENOMEM;
1073                         if (!sk_page_frag_refill(sk, pfrag))
1074                                 goto error;
1075 
1076                         if (!skb_can_coalesce(skb, i, pfrag->page,
1077                                               pfrag->offset)) {
1078                                 err = -EMSGSIZE;
1079                                 if (i == MAX_SKB_FRAGS)
1080                                         goto error;
1081 
1082                                 __skb_fill_page_desc(skb, i, pfrag->page,
1083                                                      pfrag->offset, 0);
1084                                 skb_shinfo(skb)->nr_frags = ++i;
1085                                 get_page(pfrag->page);
1086                         }
1087                         copy = min_t(int, copy, pfrag->size - pfrag->offset);
1088                         if (getfrag(from,
1089                                     page_address(pfrag->page) + pfrag->offset,
1090                                     offset, copy, skb->len, skb) < 0)
1091                                 goto error_efault;
1092 
1093                         pfrag->offset += copy;
1094                         skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
1095                         skb->len += copy;
1096                         skb->data_len += copy;
1097                         skb->truesize += copy;
1098                         atomic_add(copy, &sk->sk_wmem_alloc);
1099                 }
1100                 offset += copy;
1101                 length -= copy;
1102         }
1103 
1104         return 0;
1105 
1106 error_efault:
1107         err = -EFAULT;
1108 error:
1109         cork->length -= length;
1110         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1111         return err;
1112 }
1113 
1114 static int ip_setup_cork(struct sock *sk, struct inet_cork *cork,
1115                          struct ipcm_cookie *ipc, struct rtable **rtp)
1116 {
1117         struct ip_options_rcu *opt;
1118         struct rtable *rt;
1119 
1120         /*
1121          * setup for corking.
1122          */
1123         opt = ipc->opt;
1124         if (opt) {
1125                 if (!cork->opt) {
1126                         cork->opt = kmalloc(sizeof(struct ip_options) + 40,
1127                                             sk->sk_allocation);
1128                         if (unlikely(!cork->opt))
1129                                 return -ENOBUFS;
1130                 }
1131                 memcpy(cork->opt, &opt->opt, sizeof(struct ip_options) + opt->opt.optlen);
1132                 cork->flags |= IPCORK_OPT;
1133                 cork->addr = ipc->addr;
1134         }
1135         rt = *rtp;
1136         if (unlikely(!rt))
1137                 return -EFAULT;
1138         /*
1139          * We steal reference to this route, caller should not release it
1140          */
1141         *rtp = NULL;
1142         cork->fragsize = ip_sk_use_pmtu(sk) ?
1143                          dst_mtu(&rt->dst) : rt->dst.dev->mtu;
1144         cork->dst = &rt->dst;
1145         cork->length = 0;
1146         cork->ttl = ipc->ttl;
1147         cork->tos = ipc->tos;
1148         cork->priority = ipc->priority;
1149         cork->tx_flags = ipc->tx_flags;
1150 
1151         return 0;
1152 }
1153 
1154 /*
1155  *      ip_append_data() and ip_append_page() can make one large IP datagram
1156  *      from many pieces of data. Each pieces will be holded on the socket
1157  *      until ip_push_pending_frames() is called. Each piece can be a page
1158  *      or non-page data.
1159  *
1160  *      Not only UDP, other transport protocols - e.g. raw sockets - can use
1161  *      this interface potentially.
1162  *
1163  *      LATER: length must be adjusted by pad at tail, when it is required.
1164  */
1165 int ip_append_data(struct sock *sk, struct flowi4 *fl4,
1166                    int getfrag(void *from, char *to, int offset, int len,
1167                                int odd, struct sk_buff *skb),
1168                    void *from, int length, int transhdrlen,
1169                    struct ipcm_cookie *ipc, struct rtable **rtp,
1170                    unsigned int flags)
1171 {
1172         struct inet_sock *inet = inet_sk(sk);
1173         int err;
1174 
1175         if (flags&MSG_PROBE)
1176                 return 0;
1177 
1178         if (skb_queue_empty(&sk->sk_write_queue)) {
1179                 err = ip_setup_cork(sk, &inet->cork.base, ipc, rtp);
1180                 if (err)
1181                         return err;
1182         } else {
1183                 transhdrlen = 0;
1184         }
1185 
1186         return __ip_append_data(sk, fl4, &sk->sk_write_queue, &inet->cork.base,
1187                                 sk_page_frag(sk), getfrag,
1188                                 from, length, transhdrlen, flags);
1189 }
1190 
1191 ssize_t ip_append_page(struct sock *sk, struct flowi4 *fl4, struct page *page,
1192                        int offset, size_t size, int flags)
1193 {
1194         struct inet_sock *inet = inet_sk(sk);
1195         struct sk_buff *skb;
1196         struct rtable *rt;
1197         struct ip_options *opt = NULL;
1198         struct inet_cork *cork;
1199         int hh_len;
1200         int mtu;
1201         int len;
1202         int err;
1203         unsigned int maxfraglen, fragheaderlen, fraggap, maxnonfragsize;
1204 
1205         if (inet->hdrincl)
1206                 return -EPERM;
1207 
1208         if (flags&MSG_PROBE)
1209                 return 0;
1210 
1211         if (skb_queue_empty(&sk->sk_write_queue))
1212                 return -EINVAL;
1213 
1214         cork = &inet->cork.base;
1215         rt = (struct rtable *)cork->dst;
1216         if (cork->flags & IPCORK_OPT)
1217                 opt = cork->opt;
1218 
1219         if (!(rt->dst.dev->features&NETIF_F_SG))
1220                 return -EOPNOTSUPP;
1221 
1222         hh_len = LL_RESERVED_SPACE(rt->dst.dev);
1223         mtu = cork->fragsize;
1224 
1225         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
1226         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
1227         maxnonfragsize = ip_sk_ignore_df(sk) ? 0xFFFF : mtu;
1228 
1229         if (cork->length + size > maxnonfragsize - fragheaderlen) {
1230                 ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
1231                                mtu - (opt ? opt->optlen : 0));
1232                 return -EMSGSIZE;
1233         }
1234 
1235         skb = skb_peek_tail(&sk->sk_write_queue);
1236         if (!skb)
1237                 return -EINVAL;
1238 
1239         cork->length += size;
1240         if ((size + skb->len > mtu) &&
1241             (sk->sk_protocol == IPPROTO_UDP) &&
1242             (rt->dst.dev->features & NETIF_F_UFO)) {
1243                 skb_shinfo(skb)->gso_size = mtu - fragheaderlen;
1244                 skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
1245         }
1246 
1247         while (size > 0) {
1248                 if (skb_is_gso(skb)) {
1249                         len = size;
1250                 } else {
1251 
1252                         /* Check if the remaining data fits into current packet. */
1253                         len = mtu - skb->len;
1254                         if (len < size)
1255                                 len = maxfraglen - skb->len;
1256                 }
1257                 if (len <= 0) {
1258                         struct sk_buff *skb_prev;
1259                         int alloclen;
1260 
1261                         skb_prev = skb;
1262                         fraggap = skb_prev->len - maxfraglen;
1263 
1264                         alloclen = fragheaderlen + hh_len + fraggap + 15;
1265                         skb = sock_wmalloc(sk, alloclen, 1, sk->sk_allocation);
1266                         if (unlikely(!skb)) {
1267                                 err = -ENOBUFS;
1268                                 goto error;
1269                         }
1270 
1271                         /*
1272                          *      Fill in the control structures
1273                          */
1274                         skb->ip_summed = CHECKSUM_NONE;
1275                         skb->csum = 0;
1276                         skb_reserve(skb, hh_len);
1277 
1278                         /*
1279                          *      Find where to start putting bytes.
1280                          */
1281                         skb_put(skb, fragheaderlen + fraggap);
1282                         skb_reset_network_header(skb);
1283                         skb->transport_header = (skb->network_header +
1284                                                  fragheaderlen);
1285                         if (fraggap) {
1286                                 skb->csum = skb_copy_and_csum_bits(skb_prev,
1287                                                                    maxfraglen,
1288                                                     skb_transport_header(skb),
1289                                                                    fraggap, 0);
1290                                 skb_prev->csum = csum_sub(skb_prev->csum,
1291                                                           skb->csum);
1292                                 pskb_trim_unique(skb_prev, maxfraglen);
1293                         }
1294 
1295                         /*
1296                          * Put the packet on the pending queue.
1297                          */
1298                         __skb_queue_tail(&sk->sk_write_queue, skb);
1299                         continue;
1300                 }
1301 
1302                 if (len > size)
1303                         len = size;
1304 
1305                 if (skb_append_pagefrags(skb, page, offset, len)) {
1306                         err = -EMSGSIZE;
1307                         goto error;
1308                 }
1309 
1310                 if (skb->ip_summed == CHECKSUM_NONE) {
1311                         __wsum csum;
1312                         csum = csum_page(page, offset, len);
1313                         skb->csum = csum_block_add(skb->csum, csum, skb->len);
1314                 }
1315 
1316                 skb->len += len;
1317                 skb->data_len += len;
1318                 skb->truesize += len;
1319                 atomic_add(len, &sk->sk_wmem_alloc);
1320                 offset += len;
1321                 size -= len;
1322         }
1323         return 0;
1324 
1325 error:
1326         cork->length -= size;
1327         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1328         return err;
1329 }
1330 
1331 static void ip_cork_release(struct inet_cork *cork)
1332 {
1333         cork->flags &= ~IPCORK_OPT;
1334         kfree(cork->opt);
1335         cork->opt = NULL;
1336         dst_release(cork->dst);
1337         cork->dst = NULL;
1338 }
1339 
1340 /*
1341  *      Combined all pending IP fragments on the socket as one IP datagram
1342  *      and push them out.
1343  */
1344 struct sk_buff *__ip_make_skb(struct sock *sk,
1345                               struct flowi4 *fl4,
1346                               struct sk_buff_head *queue,
1347                               struct inet_cork *cork)
1348 {
1349         struct sk_buff *skb, *tmp_skb;
1350         struct sk_buff **tail_skb;
1351         struct inet_sock *inet = inet_sk(sk);
1352         struct net *net = sock_net(sk);
1353         struct ip_options *opt = NULL;
1354         struct rtable *rt = (struct rtable *)cork->dst;
1355         struct iphdr *iph;
1356         __be16 df = 0;
1357         __u8 ttl;
1358 
1359         skb = __skb_dequeue(queue);
1360         if (!skb)
1361                 goto out;
1362         tail_skb = &(skb_shinfo(skb)->frag_list);
1363 
1364         /* move skb->data to ip header from ext header */
1365         if (skb->data < skb_network_header(skb))
1366                 __skb_pull(skb, skb_network_offset(skb));
1367         while ((tmp_skb = __skb_dequeue(queue)) != NULL) {
1368                 __skb_pull(tmp_skb, skb_network_header_len(skb));
1369                 *tail_skb = tmp_skb;
1370                 tail_skb = &(tmp_skb->next);
1371                 skb->len += tmp_skb->len;
1372                 skb->data_len += tmp_skb->len;
1373                 skb->truesize += tmp_skb->truesize;
1374                 tmp_skb->destructor = NULL;
1375                 tmp_skb->sk = NULL;
1376         }
1377 
1378         /* Unless user demanded real pmtu discovery (IP_PMTUDISC_DO), we allow
1379          * to fragment the frame generated here. No matter, what transforms
1380          * how transforms change size of the packet, it will come out.
1381          */
1382         skb->ignore_df = ip_sk_ignore_df(sk);
1383 
1384         /* DF bit is set when we want to see DF on outgoing frames.
1385          * If ignore_df is set too, we still allow to fragment this frame
1386          * locally. */
1387         if (inet->pmtudisc == IP_PMTUDISC_DO ||
1388             inet->pmtudisc == IP_PMTUDISC_PROBE ||
1389             (skb->len <= dst_mtu(&rt->dst) &&
1390              ip_dont_fragment(sk, &rt->dst)))
1391                 df = htons(IP_DF);
1392 
1393         if (cork->flags & IPCORK_OPT)
1394                 opt = cork->opt;
1395 
1396         if (cork->ttl != 0)
1397                 ttl = cork->ttl;
1398         else if (rt->rt_type == RTN_MULTICAST)
1399                 ttl = inet->mc_ttl;
1400         else
1401                 ttl = ip_select_ttl(inet, &rt->dst);
1402 
1403         iph = ip_hdr(skb);
1404         iph->version = 4;
1405         iph->ihl = 5;
1406         iph->tos = (cork->tos != -1) ? cork->tos : inet->tos;
1407         iph->frag_off = df;
1408         iph->ttl = ttl;
1409         iph->protocol = sk->sk_protocol;
1410         ip_copy_addrs(iph, fl4);
1411         ip_select_ident(net, skb, sk);
1412 
1413         if (opt) {
1414                 iph->ihl += opt->optlen>>2;
1415                 ip_options_build(skb, opt, cork->addr, rt, 0);
1416         }
1417 
1418         skb->priority = (cork->tos != -1) ? cork->priority: sk->sk_priority;
1419         skb->mark = sk->sk_mark;
1420         /*
1421          * Steal rt from cork.dst to avoid a pair of atomic_inc/atomic_dec
1422          * on dst refcount
1423          */
1424         cork->dst = NULL;
1425         skb_dst_set(skb, &rt->dst);
1426 
1427         if (iph->protocol == IPPROTO_ICMP)
1428                 icmp_out_count(net, ((struct icmphdr *)
1429                         skb_transport_header(skb))->type);
1430 
1431         ip_cork_release(cork);
1432 out:
1433         return skb;
1434 }
1435 
1436 int ip_send_skb(struct net *net, struct sk_buff *skb)
1437 {
1438         int err;
1439 
1440         err = ip_local_out(net, skb->sk, skb);
1441         if (err) {
1442                 if (err > 0)
1443                         err = net_xmit_errno(err);
1444                 if (err)
1445                         IP_INC_STATS(net, IPSTATS_MIB_OUTDISCARDS);
1446         }
1447 
1448         return err;
1449 }
1450 
1451 int ip_push_pending_frames(struct sock *sk, struct flowi4 *fl4)
1452 {
1453         struct sk_buff *skb;
1454 
1455         skb = ip_finish_skb(sk, fl4);
1456         if (!skb)
1457                 return 0;
1458 
1459         /* Netfilter gets whole the not fragmented skb. */
1460         return ip_send_skb(sock_net(sk), skb);
1461 }
1462 
1463 /*
1464  *      Throw away all pending data on the socket.
1465  */
1466 static void __ip_flush_pending_frames(struct sock *sk,
1467                                       struct sk_buff_head *queue,
1468                                       struct inet_cork *cork)
1469 {
1470         struct sk_buff *skb;
1471 
1472         while ((skb = __skb_dequeue_tail(queue)) != NULL)
1473                 kfree_skb(skb);
1474 
1475         ip_cork_release(cork);
1476 }
1477 
1478 void ip_flush_pending_frames(struct sock *sk)
1479 {
1480         __ip_flush_pending_frames(sk, &sk->sk_write_queue, &inet_sk(sk)->cork.base);
1481 }
1482 
1483 struct sk_buff *ip_make_skb(struct sock *sk,
1484                             struct flowi4 *fl4,
1485                             int getfrag(void *from, char *to, int offset,
1486                                         int len, int odd, struct sk_buff *skb),
1487                             void *from, int length, int transhdrlen,
1488                             struct ipcm_cookie *ipc, struct rtable **rtp,
1489                             unsigned int flags)
1490 {
1491         struct inet_cork cork;
1492         struct sk_buff_head queue;
1493         int err;
1494 
1495         if (flags & MSG_PROBE)
1496                 return NULL;
1497 
1498         __skb_queue_head_init(&queue);
1499 
1500         cork.flags = 0;
1501         cork.addr = 0;
1502         cork.opt = NULL;
1503         err = ip_setup_cork(sk, &cork, ipc, rtp);
1504         if (err)
1505                 return ERR_PTR(err);
1506 
1507         err = __ip_append_data(sk, fl4, &queue, &cork,
1508                                &current->task_frag, getfrag,
1509                                from, length, transhdrlen, flags);
1510         if (err) {
1511                 __ip_flush_pending_frames(sk, &queue, &cork);
1512                 return ERR_PTR(err);
1513         }
1514 
1515         return __ip_make_skb(sk, fl4, &queue, &cork);
1516 }
1517 
1518 /*
1519  *      Fetch data from kernel space and fill in checksum if needed.
1520  */
1521 static int ip_reply_glue_bits(void *dptr, char *to, int offset,
1522                               int len, int odd, struct sk_buff *skb)
1523 {
1524         __wsum csum;
1525 
1526         csum = csum_partial_copy_nocheck(dptr+offset, to, len, 0);
1527         skb->csum = csum_block_add(skb->csum, csum, odd);
1528         return 0;
1529 }
1530 
1531 /*
1532  *      Generic function to send a packet as reply to another packet.
1533  *      Used to send some TCP resets/acks so far.
1534  */
1535 void ip_send_unicast_reply(struct sock *sk, struct sk_buff *skb,
1536                            const struct ip_options *sopt,
1537                            __be32 daddr, __be32 saddr,
1538                            const struct ip_reply_arg *arg,
1539                            unsigned int len)
1540 {
1541         struct ip_options_data replyopts;
1542         struct ipcm_cookie ipc;
1543         struct flowi4 fl4;
1544         struct rtable *rt = skb_rtable(skb);
1545         struct net *net = sock_net(sk);
1546         struct sk_buff *nskb;
1547         int err;
1548         int oif;
1549 
1550         if (__ip_options_echo(&replyopts.opt.opt, skb, sopt))
1551                 return;
1552 
1553         ipc.addr = daddr;
1554         ipc.opt = NULL;
1555         ipc.tx_flags = 0;
1556         ipc.ttl = 0;
1557         ipc.tos = -1;
1558 
1559         if (replyopts.opt.opt.optlen) {
1560                 ipc.opt = &replyopts.opt;
1561 
1562                 if (replyopts.opt.opt.srr)
1563                         daddr = replyopts.opt.opt.faddr;
1564         }
1565 
1566         oif = arg->bound_dev_if;
1567         if (!oif && netif_index_is_l3_master(net, skb->skb_iif))
1568                 oif = skb->skb_iif;
1569 
1570         flowi4_init_output(&fl4, oif,
1571                            IP4_REPLY_MARK(net, skb->mark),
1572                            RT_TOS(arg->tos),
1573                            RT_SCOPE_UNIVERSE, ip_hdr(skb)->protocol,
1574                            ip_reply_arg_flowi_flags(arg),
1575                            daddr, saddr,
1576                            tcp_hdr(skb)->source, tcp_hdr(skb)->dest);
1577         security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
1578         rt = ip_route_output_key(net, &fl4);
1579         if (IS_ERR(rt))
1580                 return;
1581 
1582         inet_sk(sk)->tos = arg->tos;
1583 
1584         sk->sk_priority = skb->priority;
1585         sk->sk_protocol = ip_hdr(skb)->protocol;
1586         sk->sk_bound_dev_if = arg->bound_dev_if;
1587         sk->sk_sndbuf = sysctl_wmem_default;
1588         err = ip_append_data(sk, &fl4, ip_reply_glue_bits, arg->iov->iov_base,
1589                              len, 0, &ipc, &rt, MSG_DONTWAIT);
1590         if (unlikely(err)) {
1591                 ip_flush_pending_frames(sk);
1592                 goto out;
1593         }
1594 
1595         nskb = skb_peek(&sk->sk_write_queue);
1596         if (nskb) {
1597                 if (arg->csumoffset >= 0)
1598                         *((__sum16 *)skb_transport_header(nskb) +
1599                           arg->csumoffset) = csum_fold(csum_add(nskb->csum,
1600                                                                 arg->csum));
1601                 nskb->ip_summed = CHECKSUM_NONE;
1602                 ip_push_pending_frames(sk, &fl4);
1603         }
1604 out:
1605         ip_rt_put(rt);
1606 }
1607 
1608 void __init ip_init(void)
1609 {
1610         ip_rt_init();
1611         inet_initpeers();
1612 
1613 #if defined(CONFIG_IP_MULTICAST)
1614         igmp_mc_init();
1615 #endif
1616 }
1617 

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