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Linux/net/ipv4/ip_output.c

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  1 /*
  2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
  3  *              operating system.  INET is implemented using the  BSD Socket
  4  *              interface as the means of communication with the user level.
  5  *
  6  *              The Internet Protocol (IP) output module.
  7  *
  8  * Authors:     Ross Biro
  9  *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 10  *              Donald Becker, <becker@super.org>
 11  *              Alan Cox, <Alan.Cox@linux.org>
 12  *              Richard Underwood
 13  *              Stefan Becker, <stefanb@yello.ping.de>
 14  *              Jorge Cwik, <jorge@laser.satlink.net>
 15  *              Arnt Gulbrandsen, <agulbra@nvg.unit.no>
 16  *              Hirokazu Takahashi, <taka@valinux.co.jp>
 17  *
 18  *      See ip_input.c for original log
 19  *
 20  *      Fixes:
 21  *              Alan Cox        :       Missing nonblock feature in ip_build_xmit.
 22  *              Mike Kilburn    :       htons() missing in ip_build_xmit.
 23  *              Bradford Johnson:       Fix faulty handling of some frames when
 24  *                                      no route is found.
 25  *              Alexander Demenshin:    Missing sk/skb free in ip_queue_xmit
 26  *                                      (in case if packet not accepted by
 27  *                                      output firewall rules)
 28  *              Mike McLagan    :       Routing by source
 29  *              Alexey Kuznetsov:       use new route cache
 30  *              Andi Kleen:             Fix broken PMTU recovery and remove
 31  *                                      some redundant tests.
 32  *      Vitaly E. Lavrov        :       Transparent proxy revived after year coma.
 33  *              Andi Kleen      :       Replace ip_reply with ip_send_reply.
 34  *              Andi Kleen      :       Split fast and slow ip_build_xmit path
 35  *                                      for decreased register pressure on x86
 36  *                                      and more readibility.
 37  *              Marc Boucher    :       When call_out_firewall returns FW_QUEUE,
 38  *                                      silently drop skb instead of failing with -EPERM.
 39  *              Detlev Wengorz  :       Copy protocol for fragments.
 40  *              Hirokazu Takahashi:     HW checksumming for outgoing UDP
 41  *                                      datagrams.
 42  *              Hirokazu Takahashi:     sendfile() on UDP works now.
 43  */
 44 
 45 #include <asm/uaccess.h>
 46 #include <linux/module.h>
 47 #include <linux/types.h>
 48 #include <linux/kernel.h>
 49 #include <linux/mm.h>
 50 #include <linux/string.h>
 51 #include <linux/errno.h>
 52 #include <linux/highmem.h>
 53 #include <linux/slab.h>
 54 
 55 #include <linux/socket.h>
 56 #include <linux/sockios.h>
 57 #include <linux/in.h>
 58 #include <linux/inet.h>
 59 #include <linux/netdevice.h>
 60 #include <linux/etherdevice.h>
 61 #include <linux/proc_fs.h>
 62 #include <linux/stat.h>
 63 #include <linux/init.h>
 64 
 65 #include <net/snmp.h>
 66 #include <net/ip.h>
 67 #include <net/protocol.h>
 68 #include <net/route.h>
 69 #include <net/xfrm.h>
 70 #include <linux/skbuff.h>
 71 #include <net/sock.h>
 72 #include <net/arp.h>
 73 #include <net/icmp.h>
 74 #include <net/checksum.h>
 75 #include <net/inetpeer.h>
 76 #include <linux/igmp.h>
 77 #include <linux/netfilter_ipv4.h>
 78 #include <linux/netfilter_bridge.h>
 79 #include <linux/mroute.h>
 80 #include <linux/netlink.h>
 81 #include <linux/tcp.h>
 82 
 83 int sysctl_ip_default_ttl __read_mostly = IPDEFTTL;
 84 EXPORT_SYMBOL(sysctl_ip_default_ttl);
 85 
 86 static int ip_fragment(struct sock *sk, struct sk_buff *skb,
 87                        unsigned int mtu,
 88                        int (*output)(struct sock *, struct sk_buff *));
 89 
 90 /* Generate a checksum for an outgoing IP datagram. */
 91 void ip_send_check(struct iphdr *iph)
 92 {
 93         iph->check = 0;
 94         iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
 95 }
 96 EXPORT_SYMBOL(ip_send_check);
 97 
 98 static int __ip_local_out_sk(struct sock *sk, struct sk_buff *skb)
 99 {
100         struct iphdr *iph = ip_hdr(skb);
101 
102         iph->tot_len = htons(skb->len);
103         ip_send_check(iph);
104         return nf_hook(NFPROTO_IPV4, NF_INET_LOCAL_OUT, sk, skb, NULL,
105                        skb_dst(skb)->dev, dst_output_sk);
106 }
107 
108 int __ip_local_out(struct sk_buff *skb)
109 {
110         return __ip_local_out_sk(skb->sk, skb);
111 }
112 
113 int ip_local_out_sk(struct sock *sk, struct sk_buff *skb)
114 {
115         int err;
116 
117         err = __ip_local_out(skb);
118         if (likely(err == 1))
119                 err = dst_output_sk(sk, skb);
120 
121         return err;
122 }
123 EXPORT_SYMBOL_GPL(ip_local_out_sk);
124 
125 static inline int ip_select_ttl(struct inet_sock *inet, struct dst_entry *dst)
126 {
127         int ttl = inet->uc_ttl;
128 
129         if (ttl < 0)
130                 ttl = ip4_dst_hoplimit(dst);
131         return ttl;
132 }
133 
134 /*
135  *              Add an ip header to a skbuff and send it out.
136  *
137  */
138 int ip_build_and_send_pkt(struct sk_buff *skb, struct sock *sk,
139                           __be32 saddr, __be32 daddr, struct ip_options_rcu *opt)
140 {
141         struct inet_sock *inet = inet_sk(sk);
142         struct rtable *rt = skb_rtable(skb);
143         struct iphdr *iph;
144 
145         /* Build the IP header. */
146         skb_push(skb, sizeof(struct iphdr) + (opt ? opt->opt.optlen : 0));
147         skb_reset_network_header(skb);
148         iph = ip_hdr(skb);
149         iph->version  = 4;
150         iph->ihl      = 5;
151         iph->tos      = inet->tos;
152         if (ip_dont_fragment(sk, &rt->dst))
153                 iph->frag_off = htons(IP_DF);
154         else
155                 iph->frag_off = 0;
156         iph->ttl      = ip_select_ttl(inet, &rt->dst);
157         iph->daddr    = (opt && opt->opt.srr ? opt->opt.faddr : daddr);
158         iph->saddr    = saddr;
159         iph->protocol = sk->sk_protocol;
160         ip_select_ident(sock_net(sk), skb, sk);
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(skb);
172 }
173 EXPORT_SYMBOL_GPL(ip_build_and_send_pkt);
174 
175 static int ip_finish_output2(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(dev_net(dev), IPSTATS_MIB_OUTMCAST, skb->len);
186         } else if (rt->rt_type == RTN_BROADCAST)
187                 IP_UPD_PO_STATS(dev_net(dev), 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 sock *sk, struct sk_buff *skb,
224                                 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(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(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 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_sk(sk, skb);
275         }
276 #endif
277         mtu = ip_skb_dst_mtu(skb);
278         if (skb_is_gso(skb))
279                 return ip_finish_output_gso(sk, skb, mtu);
280 
281         if (skb->len > mtu || (IPCB(skb)->flags & IPSKB_FRAG_PMTU))
282                 return ip_fragment(sk, skb, mtu, ip_finish_output2);
283 
284         return ip_finish_output2(sk, skb);
285 }
286 
287 int ip_mc_output(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(dev_net(dev), 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                                         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, sk, newskb,
339                                 NULL, newskb->dev, dev_loopback_xmit);
340         }
341 
342         return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING, sk, skb, NULL,
343                             skb->dev, ip_finish_output,
344                             !(IPCB(skb)->flags & IPSKB_REROUTED));
345 }
346 
347 int ip_output(struct sock *sk, struct sk_buff *skb)
348 {
349         struct net_device *dev = skb_dst(skb)->dev;
350 
351         IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUT, skb->len);
352 
353         skb->dev = dev;
354         skb->protocol = htons(ETH_P_IP);
355 
356         return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING, sk, skb,
357                             NULL, dev,
358                             ip_finish_output,
359                             !(IPCB(skb)->flags & IPSKB_REROUTED));
360 }
361 
362 /*
363  * copy saddr and daddr, possibly using 64bit load/stores
364  * Equivalent to :
365  *   iph->saddr = fl4->saddr;
366  *   iph->daddr = fl4->daddr;
367  */
368 static void ip_copy_addrs(struct iphdr *iph, const struct flowi4 *fl4)
369 {
370         BUILD_BUG_ON(offsetof(typeof(*fl4), daddr) !=
371                      offsetof(typeof(*fl4), saddr) + sizeof(fl4->saddr));
372         memcpy(&iph->saddr, &fl4->saddr,
373                sizeof(fl4->saddr) + sizeof(fl4->daddr));
374 }
375 
376 /* Note: skb->sk can be different from sk, in case of tunnels */
377 int ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl)
378 {
379         struct inet_sock *inet = inet_sk(sk);
380         struct ip_options_rcu *inet_opt;
381         struct flowi4 *fl4;
382         struct rtable *rt;
383         struct iphdr *iph;
384         int res;
385 
386         /* Skip all of this if the packet is already routed,
387          * f.e. by something like SCTP.
388          */
389         rcu_read_lock();
390         inet_opt = rcu_dereference(inet->inet_opt);
391         fl4 = &fl->u.ip4;
392         rt = skb_rtable(skb);
393         if (rt)
394                 goto packet_routed;
395 
396         /* Make sure we can route this packet. */
397         rt = (struct rtable *)__sk_dst_check(sk, 0);
398         if (!rt) {
399                 __be32 daddr;
400 
401                 /* Use correct destination address if we have options. */
402                 daddr = inet->inet_daddr;
403                 if (inet_opt && inet_opt->opt.srr)
404                         daddr = inet_opt->opt.faddr;
405 
406                 /* If this fails, retransmit mechanism of transport layer will
407                  * keep trying until route appears or the connection times
408                  * itself out.
409                  */
410                 rt = ip_route_output_ports(sock_net(sk), fl4, sk,
411                                            daddr, inet->inet_saddr,
412                                            inet->inet_dport,
413                                            inet->inet_sport,
414                                            sk->sk_protocol,
415                                            RT_CONN_FLAGS(sk),
416                                            sk->sk_bound_dev_if);
417                 if (IS_ERR(rt))
418                         goto no_route;
419                 sk_setup_caps(sk, &rt->dst);
420         }
421         skb_dst_set_noref(skb, &rt->dst);
422 
423 packet_routed:
424         if (inet_opt && inet_opt->opt.is_strictroute && rt->rt_uses_gateway)
425                 goto no_route;
426 
427         /* OK, we know where to send it, allocate and build IP header. */
428         skb_push(skb, sizeof(struct iphdr) + (inet_opt ? inet_opt->opt.optlen : 0));
429         skb_reset_network_header(skb);
430         iph = ip_hdr(skb);
431         *((__be16 *)iph) = htons((4 << 12) | (5 << 8) | (inet->tos & 0xff));
432         if (ip_dont_fragment(sk, &rt->dst) && !skb->ignore_df)
433                 iph->frag_off = htons(IP_DF);
434         else
435                 iph->frag_off = 0;
436         iph->ttl      = ip_select_ttl(inet, &rt->dst);
437         iph->protocol = sk->sk_protocol;
438         ip_copy_addrs(iph, fl4);
439 
440         /* Transport layer set skb->h.foo itself. */
441 
442         if (inet_opt && inet_opt->opt.optlen) {
443                 iph->ihl += inet_opt->opt.optlen >> 2;
444                 ip_options_build(skb, &inet_opt->opt, inet->inet_daddr, rt, 0);
445         }
446 
447         ip_select_ident_segs(sock_net(sk), skb, sk,
448                              skb_shinfo(skb)->gso_segs ?: 1);
449 
450         /* TODO : should we use skb->sk here instead of sk ? */
451         skb->priority = sk->sk_priority;
452         skb->mark = sk->sk_mark;
453 
454         res = ip_local_out(skb);
455         rcu_read_unlock();
456         return res;
457 
458 no_route:
459         rcu_read_unlock();
460         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);
461         kfree_skb(skb);
462         return -EHOSTUNREACH;
463 }
464 EXPORT_SYMBOL(ip_queue_xmit);
465 
466 static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
467 {
468         to->pkt_type = from->pkt_type;
469         to->priority = from->priority;
470         to->protocol = from->protocol;
471         skb_dst_drop(to);
472         skb_dst_copy(to, from);
473         to->dev = from->dev;
474         to->mark = from->mark;
475 
476         /* Copy the flags to each fragment. */
477         IPCB(to)->flags = IPCB(from)->flags;
478 
479 #ifdef CONFIG_NET_SCHED
480         to->tc_index = from->tc_index;
481 #endif
482         nf_copy(to, from);
483 #if defined(CONFIG_IP_VS) || defined(CONFIG_IP_VS_MODULE)
484         to->ipvs_property = from->ipvs_property;
485 #endif
486         skb_copy_secmark(to, from);
487 }
488 
489 static int ip_fragment(struct sock *sk, struct sk_buff *skb,
490                        unsigned int mtu,
491                        int (*output)(struct sock *, struct sk_buff *))
492 {
493         struct iphdr *iph = ip_hdr(skb);
494 
495         if ((iph->frag_off & htons(IP_DF)) == 0)
496                 return ip_do_fragment(sk, skb, output);
497 
498         if (unlikely(!skb->ignore_df ||
499                      (IPCB(skb)->frag_max_size &&
500                       IPCB(skb)->frag_max_size > mtu))) {
501                 struct rtable *rt = skb_rtable(skb);
502                 struct net_device *dev = rt->dst.dev;
503 
504                 IP_INC_STATS(dev_net(dev), 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(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 sock *sk, struct sk_buff *skb,
522                    int (*output)(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         /*
537          *      Point into the IP datagram header.
538          */
539 
540         iph = ip_hdr(skb);
541 
542         mtu = ip_skb_dst_mtu(skb);
543         if (IPCB(skb)->frag_max_size && IPCB(skb)->frag_max_size < mtu)
544                 mtu = IPCB(skb)->frag_max_size;
545 
546         /*
547          *      Setup starting values.
548          */
549 
550         hlen = iph->ihl * 4;
551         mtu = mtu - hlen;       /* Size of data space */
552         IPCB(skb)->flags |= IPSKB_FRAG_COMPLETE;
553 
554         /* When frag_list is given, use it. First, check its validity:
555          * some transformers could create wrong frag_list or break existing
556          * one, it is not prohibited. In this case fall back to copying.
557          *
558          * LATER: this step can be merged to real generation of fragments,
559          * we can switch to copy when see the first bad fragment.
560          */
561         if (skb_has_frag_list(skb)) {
562                 struct sk_buff *frag, *frag2;
563                 int first_len = skb_pagelen(skb);
564 
565                 if (first_len - hlen > mtu ||
566                     ((first_len - hlen) & 7) ||
567                     ip_is_fragment(iph) ||
568                     skb_cloned(skb))
569                         goto slow_path;
570 
571                 skb_walk_frags(skb, frag) {
572                         /* Correct geometry. */
573                         if (frag->len > mtu ||
574                             ((frag->len & 7) && frag->next) ||
575                             skb_headroom(frag) < hlen)
576                                 goto slow_path_clean;
577 
578                         /* Partially cloned skb? */
579                         if (skb_shared(frag))
580                                 goto slow_path_clean;
581 
582                         BUG_ON(frag->sk);
583                         if (skb->sk) {
584                                 frag->sk = skb->sk;
585                                 frag->destructor = sock_wfree;
586                         }
587                         skb->truesize -= frag->truesize;
588                 }
589 
590                 /* Everything is OK. Generate! */
591 
592                 err = 0;
593                 offset = 0;
594                 frag = skb_shinfo(skb)->frag_list;
595                 skb_frag_list_init(skb);
596                 skb->data_len = first_len - skb_headlen(skb);
597                 skb->len = first_len;
598                 iph->tot_len = htons(first_len);
599                 iph->frag_off = htons(IP_MF);
600                 ip_send_check(iph);
601 
602                 for (;;) {
603                         /* Prepare header of the next frame,
604                          * before previous one went down. */
605                         if (frag) {
606                                 frag->ip_summed = CHECKSUM_NONE;
607                                 skb_reset_transport_header(frag);
608                                 __skb_push(frag, hlen);
609                                 skb_reset_network_header(frag);
610                                 memcpy(skb_network_header(frag), iph, hlen);
611                                 iph = ip_hdr(frag);
612                                 iph->tot_len = htons(frag->len);
613                                 ip_copy_metadata(frag, skb);
614                                 if (offset == 0)
615                                         ip_options_fragment(frag);
616                                 offset += skb->len - hlen;
617                                 iph->frag_off = htons(offset>>3);
618                                 if (frag->next)
619                                         iph->frag_off |= htons(IP_MF);
620                                 /* Ready, complete checksum */
621                                 ip_send_check(iph);
622                         }
623 
624                         err = output(sk, skb);
625 
626                         if (!err)
627                                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGCREATES);
628                         if (err || !frag)
629                                 break;
630 
631                         skb = frag;
632                         frag = skb->next;
633                         skb->next = NULL;
634                 }
635 
636                 if (err == 0) {
637                         IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGOKS);
638                         return 0;
639                 }
640 
641                 while (frag) {
642                         skb = frag->next;
643                         kfree_skb(frag);
644                         frag = skb;
645                 }
646                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
647                 return err;
648 
649 slow_path_clean:
650                 skb_walk_frags(skb, frag2) {
651                         if (frag2 == frag)
652                                 break;
653                         frag2->sk = NULL;
654                         frag2->destructor = NULL;
655                         skb->truesize += frag2->truesize;
656                 }
657         }
658 
659 slow_path:
660         /* for offloaded checksums cleanup checksum before fragmentation */
661         if ((skb->ip_summed == CHECKSUM_PARTIAL) && skb_checksum_help(skb))
662                 goto fail;
663         iph = ip_hdr(skb);
664 
665         left = skb->len - hlen;         /* Space per frame */
666         ptr = hlen;             /* Where to start from */
667 
668         ll_rs = LL_RESERVED_SPACE(rt->dst.dev);
669 
670         /*
671          *      Fragment the datagram.
672          */
673 
674         offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3;
675         not_last_frag = iph->frag_off & htons(IP_MF);
676 
677         /*
678          *      Keep copying data until we run out.
679          */
680 
681         while (left > 0) {
682                 len = left;
683                 /* IF: it doesn't fit, use 'mtu' - the data space left */
684                 if (len > mtu)
685                         len = mtu;
686                 /* IF: we are not sending up to and including the packet end
687                    then align the next start on an eight byte boundary */
688                 if (len < left) {
689                         len &= ~7;
690                 }
691 
692                 /* Allocate buffer */
693                 skb2 = alloc_skb(len + hlen + ll_rs, GFP_ATOMIC);
694                 if (!skb2) {
695                         err = -ENOMEM;
696                         goto fail;
697                 }
698 
699                 /*
700                  *      Set up data on packet
701                  */
702 
703                 ip_copy_metadata(skb2, skb);
704                 skb_reserve(skb2, ll_rs);
705                 skb_put(skb2, len + hlen);
706                 skb_reset_network_header(skb2);
707                 skb2->transport_header = skb2->network_header + hlen;
708 
709                 /*
710                  *      Charge the memory for the fragment to any owner
711                  *      it might possess
712                  */
713 
714                 if (skb->sk)
715                         skb_set_owner_w(skb2, skb->sk);
716 
717                 /*
718                  *      Copy the packet header into the new buffer.
719                  */
720 
721                 skb_copy_from_linear_data(skb, skb_network_header(skb2), hlen);
722 
723                 /*
724                  *      Copy a block of the IP datagram.
725                  */
726                 if (skb_copy_bits(skb, ptr, skb_transport_header(skb2), len))
727                         BUG();
728                 left -= len;
729 
730                 /*
731                  *      Fill in the new header fields.
732                  */
733                 iph = ip_hdr(skb2);
734                 iph->frag_off = htons((offset >> 3));
735 
736                 if (IPCB(skb)->flags & IPSKB_FRAG_PMTU)
737                         iph->frag_off |= htons(IP_DF);
738 
739                 /* ANK: dirty, but effective trick. Upgrade options only if
740                  * the segment to be fragmented was THE FIRST (otherwise,
741                  * options are already fixed) and make it ONCE
742                  * on the initial skb, so that all the following fragments
743                  * will inherit fixed options.
744                  */
745                 if (offset == 0)
746                         ip_options_fragment(skb);
747 
748                 /*
749                  *      Added AC : If we are fragmenting a fragment that's not the
750                  *                 last fragment then keep MF on each bit
751                  */
752                 if (left > 0 || not_last_frag)
753                         iph->frag_off |= htons(IP_MF);
754                 ptr += len;
755                 offset += len;
756 
757                 /*
758                  *      Put this fragment into the sending queue.
759                  */
760                 iph->tot_len = htons(len + hlen);
761 
762                 ip_send_check(iph);
763 
764                 err = output(sk, skb2);
765                 if (err)
766                         goto fail;
767 
768                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGCREATES);
769         }
770         consume_skb(skb);
771         IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGOKS);
772         return err;
773 
774 fail:
775         kfree_skb(skb);
776         IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
777         return err;
778 }
779 EXPORT_SYMBOL(ip_do_fragment);
780 
781 int
782 ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
783 {
784         struct msghdr *msg = from;
785 
786         if (skb->ip_summed == CHECKSUM_PARTIAL) {
787                 if (copy_from_iter(to, len, &msg->msg_iter) != len)
788                         return -EFAULT;
789         } else {
790                 __wsum csum = 0;
791                 if (csum_and_copy_from_iter(to, len, &csum, &msg->msg_iter) != len)
792                         return -EFAULT;
793                 skb->csum = csum_block_add(skb->csum, csum, odd);
794         }
795         return 0;
796 }
797 EXPORT_SYMBOL(ip_generic_getfrag);
798 
799 static inline __wsum
800 csum_page(struct page *page, int offset, int copy)
801 {
802         char *kaddr;
803         __wsum csum;
804         kaddr = kmap(page);
805         csum = csum_partial(kaddr + offset, copy, 0);
806         kunmap(page);
807         return csum;
808 }
809 
810 static inline int ip_ufo_append_data(struct sock *sk,
811                         struct sk_buff_head *queue,
812                         int getfrag(void *from, char *to, int offset, int len,
813                                int odd, struct sk_buff *skb),
814                         void *from, int length, int hh_len, int fragheaderlen,
815                         int transhdrlen, int maxfraglen, unsigned int flags)
816 {
817         struct sk_buff *skb;
818         int err;
819 
820         /* There is support for UDP fragmentation offload by network
821          * device, so create one single skb packet containing complete
822          * udp datagram
823          */
824         skb = skb_peek_tail(queue);
825         if (!skb) {
826                 skb = sock_alloc_send_skb(sk,
827                         hh_len + fragheaderlen + transhdrlen + 20,
828                         (flags & MSG_DONTWAIT), &err);
829 
830                 if (!skb)
831                         return err;
832 
833                 /* reserve space for Hardware header */
834                 skb_reserve(skb, hh_len);
835 
836                 /* create space for UDP/IP header */
837                 skb_put(skb, fragheaderlen + transhdrlen);
838 
839                 /* initialize network header pointer */
840                 skb_reset_network_header(skb);
841 
842                 /* initialize protocol header pointer */
843                 skb->transport_header = skb->network_header + fragheaderlen;
844 
845                 skb->csum = 0;
846 
847                 __skb_queue_tail(queue, skb);
848         } else if (skb_is_gso(skb)) {
849                 goto append;
850         }
851 
852         skb->ip_summed = CHECKSUM_PARTIAL;
853         /* specify the length of each IP datagram fragment */
854         skb_shinfo(skb)->gso_size = maxfraglen - fragheaderlen;
855         skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
856 
857 append:
858         return skb_append_datato_frags(sk, skb, getfrag, from,
859                                        (length - transhdrlen));
860 }
861 
862 static int __ip_append_data(struct sock *sk,
863                             struct flowi4 *fl4,
864                             struct sk_buff_head *queue,
865                             struct inet_cork *cork,
866                             struct page_frag *pfrag,
867                             int getfrag(void *from, char *to, int offset,
868                                         int len, int odd, struct sk_buff *skb),
869                             void *from, int length, int transhdrlen,
870                             unsigned int flags)
871 {
872         struct inet_sock *inet = inet_sk(sk);
873         struct sk_buff *skb;
874 
875         struct ip_options *opt = cork->opt;
876         int hh_len;
877         int exthdrlen;
878         int mtu;
879         int copy;
880         int err;
881         int offset = 0;
882         unsigned int maxfraglen, fragheaderlen, maxnonfragsize;
883         int csummode = CHECKSUM_NONE;
884         struct rtable *rt = (struct rtable *)cork->dst;
885         u32 tskey = 0;
886 
887         skb = skb_peek_tail(queue);
888 
889         exthdrlen = !skb ? rt->dst.header_len : 0;
890         mtu = cork->fragsize;
891         if (cork->tx_flags & SKBTX_ANY_SW_TSTAMP &&
892             sk->sk_tsflags & SOF_TIMESTAMPING_OPT_ID)
893                 tskey = sk->sk_tskey++;
894 
895         hh_len = LL_RESERVED_SPACE(rt->dst.dev);
896 
897         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
898         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
899         maxnonfragsize = ip_sk_ignore_df(sk) ? 0xFFFF : mtu;
900 
901         if (cork->length + length > maxnonfragsize - fragheaderlen) {
902                 ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
903                                mtu - (opt ? opt->optlen : 0));
904                 return -EMSGSIZE;
905         }
906 
907         /*
908          * transhdrlen > 0 means that this is the first fragment and we wish
909          * it won't be fragmented in the future.
910          */
911         if (transhdrlen &&
912             length + fragheaderlen <= mtu &&
913             rt->dst.dev->features & NETIF_F_V4_CSUM &&
914             !exthdrlen)
915                 csummode = CHECKSUM_PARTIAL;
916 
917         cork->length += length;
918         if (((length > mtu) || (skb && skb_is_gso(skb))) &&
919             (sk->sk_protocol == IPPROTO_UDP) &&
920             (rt->dst.dev->features & NETIF_F_UFO) && !rt->dst.header_len &&
921             (sk->sk_type == SOCK_DGRAM)) {
922                 err = ip_ufo_append_data(sk, queue, getfrag, from, length,
923                                          hh_len, fragheaderlen, transhdrlen,
924                                          maxfraglen, flags);
925                 if (err)
926                         goto error;
927                 return 0;
928         }
929 
930         /* So, what's going on in the loop below?
931          *
932          * We use calculated fragment length to generate chained skb,
933          * each of segments is IP fragment ready for sending to network after
934          * adding appropriate IP header.
935          */
936 
937         if (!skb)
938                 goto alloc_new_skb;
939 
940         while (length > 0) {
941                 /* Check if the remaining data fits into current packet. */
942                 copy = mtu - skb->len;
943                 if (copy < length)
944                         copy = maxfraglen - skb->len;
945                 if (copy <= 0) {
946                         char *data;
947                         unsigned int datalen;
948                         unsigned int fraglen;
949                         unsigned int fraggap;
950                         unsigned int alloclen;
951                         struct sk_buff *skb_prev;
952 alloc_new_skb:
953                         skb_prev = skb;
954                         if (skb_prev)
955                                 fraggap = skb_prev->len - maxfraglen;
956                         else
957                                 fraggap = 0;
958 
959                         /*
960                          * If remaining data exceeds the mtu,
961                          * we know we need more fragment(s).
962                          */
963                         datalen = length + fraggap;
964                         if (datalen > mtu - fragheaderlen)
965                                 datalen = maxfraglen - fragheaderlen;
966                         fraglen = datalen + fragheaderlen;
967 
968                         if ((flags & MSG_MORE) &&
969                             !(rt->dst.dev->features&NETIF_F_SG))
970                                 alloclen = mtu;
971                         else
972                                 alloclen = fraglen;
973 
974                         alloclen += exthdrlen;
975 
976                         /* The last fragment gets additional space at tail.
977                          * Note, with MSG_MORE we overallocate on fragments,
978                          * because we have no idea what fragment will be
979                          * the last.
980                          */
981                         if (datalen == length + fraggap)
982                                 alloclen += rt->dst.trailer_len;
983 
984                         if (transhdrlen) {
985                                 skb = sock_alloc_send_skb(sk,
986                                                 alloclen + hh_len + 15,
987                                                 (flags & MSG_DONTWAIT), &err);
988                         } else {
989                                 skb = NULL;
990                                 if (atomic_read(&sk->sk_wmem_alloc) <=
991                                     2 * sk->sk_sndbuf)
992                                         skb = sock_wmalloc(sk,
993                                                            alloclen + hh_len + 15, 1,
994                                                            sk->sk_allocation);
995                                 if (unlikely(!skb))
996                                         err = -ENOBUFS;
997                         }
998                         if (!skb)
999                                 goto error;
1000 
1001                         /*
1002                          *      Fill in the control structures
1003                          */
1004                         skb->ip_summed = csummode;
1005                         skb->csum = 0;
1006                         skb_reserve(skb, hh_len);
1007 
1008                         /* only the initial fragment is time stamped */
1009                         skb_shinfo(skb)->tx_flags = cork->tx_flags;
1010                         cork->tx_flags = 0;
1011                         skb_shinfo(skb)->tskey = tskey;
1012                         tskey = 0;
1013 
1014                         /*
1015                          *      Find where to start putting bytes.
1016                          */
1017                         data = skb_put(skb, fraglen + exthdrlen);
1018                         skb_set_network_header(skb, exthdrlen);
1019                         skb->transport_header = (skb->network_header +
1020                                                  fragheaderlen);
1021                         data += fragheaderlen + exthdrlen;
1022 
1023                         if (fraggap) {
1024                                 skb->csum = skb_copy_and_csum_bits(
1025                                         skb_prev, maxfraglen,
1026                                         data + transhdrlen, fraggap, 0);
1027                                 skb_prev->csum = csum_sub(skb_prev->csum,
1028                                                           skb->csum);
1029                                 data += fraggap;
1030                                 pskb_trim_unique(skb_prev, maxfraglen);
1031                         }
1032 
1033                         copy = datalen - transhdrlen - fraggap;
1034                         if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
1035                                 err = -EFAULT;
1036                                 kfree_skb(skb);
1037                                 goto error;
1038                         }
1039 
1040                         offset += copy;
1041                         length -= datalen - fraggap;
1042                         transhdrlen = 0;
1043                         exthdrlen = 0;
1044                         csummode = CHECKSUM_NONE;
1045 
1046                         /*
1047                          * Put the packet on the pending queue.
1048                          */
1049                         __skb_queue_tail(queue, skb);
1050                         continue;
1051                 }
1052 
1053                 if (copy > length)
1054                         copy = length;
1055 
1056                 if (!(rt->dst.dev->features&NETIF_F_SG)) {
1057                         unsigned int off;
1058 
1059                         off = skb->len;
1060                         if (getfrag(from, skb_put(skb, copy),
1061                                         offset, copy, off, skb) < 0) {
1062                                 __skb_trim(skb, off);
1063                                 err = -EFAULT;
1064                                 goto error;
1065                         }
1066                 } else {
1067                         int i = skb_shinfo(skb)->nr_frags;
1068 
1069                         err = -ENOMEM;
1070                         if (!sk_page_frag_refill(sk, pfrag))
1071                                 goto error;
1072 
1073                         if (!skb_can_coalesce(skb, i, pfrag->page,
1074                                               pfrag->offset)) {
1075                                 err = -EMSGSIZE;
1076                                 if (i == MAX_SKB_FRAGS)
1077                                         goto error;
1078 
1079                                 __skb_fill_page_desc(skb, i, pfrag->page,
1080                                                      pfrag->offset, 0);
1081                                 skb_shinfo(skb)->nr_frags = ++i;
1082                                 get_page(pfrag->page);
1083                         }
1084                         copy = min_t(int, copy, pfrag->size - pfrag->offset);
1085                         if (getfrag(from,
1086                                     page_address(pfrag->page) + pfrag->offset,
1087                                     offset, copy, skb->len, skb) < 0)
1088                                 goto error_efault;
1089 
1090                         pfrag->offset += copy;
1091                         skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
1092                         skb->len += copy;
1093                         skb->data_len += copy;
1094                         skb->truesize += copy;
1095                         atomic_add(copy, &sk->sk_wmem_alloc);
1096                 }
1097                 offset += copy;
1098                 length -= copy;
1099         }
1100 
1101         return 0;
1102 
1103 error_efault:
1104         err = -EFAULT;
1105 error:
1106         cork->length -= length;
1107         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1108         return err;
1109 }
1110 
1111 static int ip_setup_cork(struct sock *sk, struct inet_cork *cork,
1112                          struct ipcm_cookie *ipc, struct rtable **rtp)
1113 {
1114         struct ip_options_rcu *opt;
1115         struct rtable *rt;
1116 
1117         /*
1118          * setup for corking.
1119          */
1120         opt = ipc->opt;
1121         if (opt) {
1122                 if (!cork->opt) {
1123                         cork->opt = kmalloc(sizeof(struct ip_options) + 40,
1124                                             sk->sk_allocation);
1125                         if (unlikely(!cork->opt))
1126                                 return -ENOBUFS;
1127                 }
1128                 memcpy(cork->opt, &opt->opt, sizeof(struct ip_options) + opt->opt.optlen);
1129                 cork->flags |= IPCORK_OPT;
1130                 cork->addr = ipc->addr;
1131         }
1132         rt = *rtp;
1133         if (unlikely(!rt))
1134                 return -EFAULT;
1135         /*
1136          * We steal reference to this route, caller should not release it
1137          */
1138         *rtp = NULL;
1139         cork->fragsize = ip_sk_use_pmtu(sk) ?
1140                          dst_mtu(&rt->dst) : rt->dst.dev->mtu;
1141         cork->dst = &rt->dst;
1142         cork->length = 0;
1143         cork->ttl = ipc->ttl;
1144         cork->tos = ipc->tos;
1145         cork->priority = ipc->priority;
1146         cork->tx_flags = ipc->tx_flags;
1147 
1148         return 0;
1149 }
1150 
1151 /*
1152  *      ip_append_data() and ip_append_page() can make one large IP datagram
1153  *      from many pieces of data. Each pieces will be holded on the socket
1154  *      until ip_push_pending_frames() is called. Each piece can be a page
1155  *      or non-page data.
1156  *
1157  *      Not only UDP, other transport protocols - e.g. raw sockets - can use
1158  *      this interface potentially.
1159  *
1160  *      LATER: length must be adjusted by pad at tail, when it is required.
1161  */
1162 int ip_append_data(struct sock *sk, struct flowi4 *fl4,
1163                    int getfrag(void *from, char *to, int offset, int len,
1164                                int odd, struct sk_buff *skb),
1165                    void *from, int length, int transhdrlen,
1166                    struct ipcm_cookie *ipc, struct rtable **rtp,
1167                    unsigned int flags)
1168 {
1169         struct inet_sock *inet = inet_sk(sk);
1170         int err;
1171 
1172         if (flags&MSG_PROBE)
1173                 return 0;
1174 
1175         if (skb_queue_empty(&sk->sk_write_queue)) {
1176                 err = ip_setup_cork(sk, &inet->cork.base, ipc, rtp);
1177                 if (err)
1178                         return err;
1179         } else {
1180                 transhdrlen = 0;
1181         }
1182 
1183         return __ip_append_data(sk, fl4, &sk->sk_write_queue, &inet->cork.base,
1184                                 sk_page_frag(sk), getfrag,
1185                                 from, length, transhdrlen, flags);
1186 }
1187 
1188 ssize_t ip_append_page(struct sock *sk, struct flowi4 *fl4, struct page *page,
1189                        int offset, size_t size, int flags)
1190 {
1191         struct inet_sock *inet = inet_sk(sk);
1192         struct sk_buff *skb;
1193         struct rtable *rt;
1194         struct ip_options *opt = NULL;
1195         struct inet_cork *cork;
1196         int hh_len;
1197         int mtu;
1198         int len;
1199         int err;
1200         unsigned int maxfraglen, fragheaderlen, fraggap, maxnonfragsize;
1201 
1202         if (inet->hdrincl)
1203                 return -EPERM;
1204 
1205         if (flags&MSG_PROBE)
1206                 return 0;
1207 
1208         if (skb_queue_empty(&sk->sk_write_queue))
1209                 return -EINVAL;
1210 
1211         cork = &inet->cork.base;
1212         rt = (struct rtable *)cork->dst;
1213         if (cork->flags & IPCORK_OPT)
1214                 opt = cork->opt;
1215 
1216         if (!(rt->dst.dev->features&NETIF_F_SG))
1217                 return -EOPNOTSUPP;
1218 
1219         hh_len = LL_RESERVED_SPACE(rt->dst.dev);
1220         mtu = cork->fragsize;
1221 
1222         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
1223         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
1224         maxnonfragsize = ip_sk_ignore_df(sk) ? 0xFFFF : mtu;
1225 
1226         if (cork->length + size > maxnonfragsize - fragheaderlen) {
1227                 ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
1228                                mtu - (opt ? opt->optlen : 0));
1229                 return -EMSGSIZE;
1230         }
1231 
1232         skb = skb_peek_tail(&sk->sk_write_queue);
1233         if (!skb)
1234                 return -EINVAL;
1235 
1236         cork->length += size;
1237         if ((size + skb->len > mtu) &&
1238             (sk->sk_protocol == IPPROTO_UDP) &&
1239             (rt->dst.dev->features & NETIF_F_UFO)) {
1240                 skb_shinfo(skb)->gso_size = mtu - fragheaderlen;
1241                 skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
1242         }
1243 
1244         while (size > 0) {
1245                 if (skb_is_gso(skb)) {
1246                         len = size;
1247                 } else {
1248 
1249                         /* Check if the remaining data fits into current packet. */
1250                         len = mtu - skb->len;
1251                         if (len < size)
1252                                 len = maxfraglen - skb->len;
1253                 }
1254                 if (len <= 0) {
1255                         struct sk_buff *skb_prev;
1256                         int alloclen;
1257 
1258                         skb_prev = skb;
1259                         fraggap = skb_prev->len - maxfraglen;
1260 
1261                         alloclen = fragheaderlen + hh_len + fraggap + 15;
1262                         skb = sock_wmalloc(sk, alloclen, 1, sk->sk_allocation);
1263                         if (unlikely(!skb)) {
1264                                 err = -ENOBUFS;
1265                                 goto error;
1266                         }
1267 
1268                         /*
1269                          *      Fill in the control structures
1270                          */
1271                         skb->ip_summed = CHECKSUM_NONE;
1272                         skb->csum = 0;
1273                         skb_reserve(skb, hh_len);
1274 
1275                         /*
1276                          *      Find where to start putting bytes.
1277                          */
1278                         skb_put(skb, fragheaderlen + fraggap);
1279                         skb_reset_network_header(skb);
1280                         skb->transport_header = (skb->network_header +
1281                                                  fragheaderlen);
1282                         if (fraggap) {
1283                                 skb->csum = skb_copy_and_csum_bits(skb_prev,
1284                                                                    maxfraglen,
1285                                                     skb_transport_header(skb),
1286                                                                    fraggap, 0);
1287                                 skb_prev->csum = csum_sub(skb_prev->csum,
1288                                                           skb->csum);
1289                                 pskb_trim_unique(skb_prev, maxfraglen);
1290                         }
1291 
1292                         /*
1293                          * Put the packet on the pending queue.
1294                          */
1295                         __skb_queue_tail(&sk->sk_write_queue, skb);
1296                         continue;
1297                 }
1298 
1299                 if (len > size)
1300                         len = size;
1301 
1302                 if (skb_append_pagefrags(skb, page, offset, len)) {
1303                         err = -EMSGSIZE;
1304                         goto error;
1305                 }
1306 
1307                 if (skb->ip_summed == CHECKSUM_NONE) {
1308                         __wsum csum;
1309                         csum = csum_page(page, offset, len);
1310                         skb->csum = csum_block_add(skb->csum, csum, skb->len);
1311                 }
1312 
1313                 skb->len += len;
1314                 skb->data_len += len;
1315                 skb->truesize += len;
1316                 atomic_add(len, &sk->sk_wmem_alloc);
1317                 offset += len;
1318                 size -= len;
1319         }
1320         return 0;
1321 
1322 error:
1323         cork->length -= size;
1324         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1325         return err;
1326 }
1327 
1328 static void ip_cork_release(struct inet_cork *cork)
1329 {
1330         cork->flags &= ~IPCORK_OPT;
1331         kfree(cork->opt);
1332         cork->opt = NULL;
1333         dst_release(cork->dst);
1334         cork->dst = NULL;
1335 }
1336 
1337 /*
1338  *      Combined all pending IP fragments on the socket as one IP datagram
1339  *      and push them out.
1340  */
1341 struct sk_buff *__ip_make_skb(struct sock *sk,
1342                               struct flowi4 *fl4,
1343                               struct sk_buff_head *queue,
1344                               struct inet_cork *cork)
1345 {
1346         struct sk_buff *skb, *tmp_skb;
1347         struct sk_buff **tail_skb;
1348         struct inet_sock *inet = inet_sk(sk);
1349         struct net *net = sock_net(sk);
1350         struct ip_options *opt = NULL;
1351         struct rtable *rt = (struct rtable *)cork->dst;
1352         struct iphdr *iph;
1353         __be16 df = 0;
1354         __u8 ttl;
1355 
1356         skb = __skb_dequeue(queue);
1357         if (!skb)
1358                 goto out;
1359         tail_skb = &(skb_shinfo(skb)->frag_list);
1360 
1361         /* move skb->data to ip header from ext header */
1362         if (skb->data < skb_network_header(skb))
1363                 __skb_pull(skb, skb_network_offset(skb));
1364         while ((tmp_skb = __skb_dequeue(queue)) != NULL) {
1365                 __skb_pull(tmp_skb, skb_network_header_len(skb));
1366                 *tail_skb = tmp_skb;
1367                 tail_skb = &(tmp_skb->next);
1368                 skb->len += tmp_skb->len;
1369                 skb->data_len += tmp_skb->len;
1370                 skb->truesize += tmp_skb->truesize;
1371                 tmp_skb->destructor = NULL;
1372                 tmp_skb->sk = NULL;
1373         }
1374 
1375         /* Unless user demanded real pmtu discovery (IP_PMTUDISC_DO), we allow
1376          * to fragment the frame generated here. No matter, what transforms
1377          * how transforms change size of the packet, it will come out.
1378          */
1379         skb->ignore_df = ip_sk_ignore_df(sk);
1380 
1381         /* DF bit is set when we want to see DF on outgoing frames.
1382          * If ignore_df is set too, we still allow to fragment this frame
1383          * locally. */
1384         if (inet->pmtudisc == IP_PMTUDISC_DO ||
1385             inet->pmtudisc == IP_PMTUDISC_PROBE ||
1386             (skb->len <= dst_mtu(&rt->dst) &&
1387              ip_dont_fragment(sk, &rt->dst)))
1388                 df = htons(IP_DF);
1389 
1390         if (cork->flags & IPCORK_OPT)
1391                 opt = cork->opt;
1392 
1393         if (cork->ttl != 0)
1394                 ttl = cork->ttl;
1395         else if (rt->rt_type == RTN_MULTICAST)
1396                 ttl = inet->mc_ttl;
1397         else
1398                 ttl = ip_select_ttl(inet, &rt->dst);
1399 
1400         iph = ip_hdr(skb);
1401         iph->version = 4;
1402         iph->ihl = 5;
1403         iph->tos = (cork->tos != -1) ? cork->tos : inet->tos;
1404         iph->frag_off = df;
1405         iph->ttl = ttl;
1406         iph->protocol = sk->sk_protocol;
1407         ip_copy_addrs(iph, fl4);
1408         ip_select_ident(net, skb, sk);
1409 
1410         if (opt) {
1411                 iph->ihl += opt->optlen>>2;
1412                 ip_options_build(skb, opt, cork->addr, rt, 0);
1413         }
1414 
1415         skb->priority = (cork->tos != -1) ? cork->priority: sk->sk_priority;
1416         skb->mark = sk->sk_mark;
1417         /*
1418          * Steal rt from cork.dst to avoid a pair of atomic_inc/atomic_dec
1419          * on dst refcount
1420          */
1421         cork->dst = NULL;
1422         skb_dst_set(skb, &rt->dst);
1423 
1424         if (iph->protocol == IPPROTO_ICMP)
1425                 icmp_out_count(net, ((struct icmphdr *)
1426                         skb_transport_header(skb))->type);
1427 
1428         ip_cork_release(cork);
1429 out:
1430         return skb;
1431 }
1432 
1433 int ip_send_skb(struct net *net, struct sk_buff *skb)
1434 {
1435         int err;
1436 
1437         err = ip_local_out(skb);
1438         if (err) {
1439                 if (err > 0)
1440                         err = net_xmit_errno(err);
1441                 if (err)
1442                         IP_INC_STATS(net, IPSTATS_MIB_OUTDISCARDS);
1443         }
1444 
1445         return err;
1446 }
1447 
1448 int ip_push_pending_frames(struct sock *sk, struct flowi4 *fl4)
1449 {
1450         struct sk_buff *skb;
1451 
1452         skb = ip_finish_skb(sk, fl4);
1453         if (!skb)
1454                 return 0;
1455 
1456         /* Netfilter gets whole the not fragmented skb. */
1457         return ip_send_skb(sock_net(sk), skb);
1458 }
1459 
1460 /*
1461  *      Throw away all pending data on the socket.
1462  */
1463 static void __ip_flush_pending_frames(struct sock *sk,
1464                                       struct sk_buff_head *queue,
1465                                       struct inet_cork *cork)
1466 {
1467         struct sk_buff *skb;
1468 
1469         while ((skb = __skb_dequeue_tail(queue)) != NULL)
1470                 kfree_skb(skb);
1471 
1472         ip_cork_release(cork);
1473 }
1474 
1475 void ip_flush_pending_frames(struct sock *sk)
1476 {
1477         __ip_flush_pending_frames(sk, &sk->sk_write_queue, &inet_sk(sk)->cork.base);
1478 }
1479 
1480 struct sk_buff *ip_make_skb(struct sock *sk,
1481                             struct flowi4 *fl4,
1482                             int getfrag(void *from, char *to, int offset,
1483                                         int len, int odd, struct sk_buff *skb),
1484                             void *from, int length, int transhdrlen,
1485                             struct ipcm_cookie *ipc, struct rtable **rtp,
1486                             unsigned int flags)
1487 {
1488         struct inet_cork cork;
1489         struct sk_buff_head queue;
1490         int err;
1491 
1492         if (flags & MSG_PROBE)
1493                 return NULL;
1494 
1495         __skb_queue_head_init(&queue);
1496 
1497         cork.flags = 0;
1498         cork.addr = 0;
1499         cork.opt = NULL;
1500         err = ip_setup_cork(sk, &cork, ipc, rtp);
1501         if (err)
1502                 return ERR_PTR(err);
1503 
1504         err = __ip_append_data(sk, fl4, &queue, &cork,
1505                                &current->task_frag, getfrag,
1506                                from, length, transhdrlen, flags);
1507         if (err) {
1508                 __ip_flush_pending_frames(sk, &queue, &cork);
1509                 return ERR_PTR(err);
1510         }
1511 
1512         return __ip_make_skb(sk, fl4, &queue, &cork);
1513 }
1514 
1515 /*
1516  *      Fetch data from kernel space and fill in checksum if needed.
1517  */
1518 static int ip_reply_glue_bits(void *dptr, char *to, int offset,
1519                               int len, int odd, struct sk_buff *skb)
1520 {
1521         __wsum csum;
1522 
1523         csum = csum_partial_copy_nocheck(dptr+offset, to, len, 0);
1524         skb->csum = csum_block_add(skb->csum, csum, odd);
1525         return 0;
1526 }
1527 
1528 /*
1529  *      Generic function to send a packet as reply to another packet.
1530  *      Used to send some TCP resets/acks so far.
1531  */
1532 void ip_send_unicast_reply(struct sock *sk, struct sk_buff *skb,
1533                            const struct ip_options *sopt,
1534                            __be32 daddr, __be32 saddr,
1535                            const struct ip_reply_arg *arg,
1536                            unsigned int len)
1537 {
1538         struct ip_options_data replyopts;
1539         struct ipcm_cookie ipc;
1540         struct flowi4 fl4;
1541         struct rtable *rt = skb_rtable(skb);
1542         struct net *net = sock_net(sk);
1543         struct sk_buff *nskb;
1544         int err;
1545 
1546         if (__ip_options_echo(&replyopts.opt.opt, skb, sopt))
1547                 return;
1548 
1549         ipc.addr = daddr;
1550         ipc.opt = NULL;
1551         ipc.tx_flags = 0;
1552         ipc.ttl = 0;
1553         ipc.tos = -1;
1554 
1555         if (replyopts.opt.opt.optlen) {
1556                 ipc.opt = &replyopts.opt;
1557 
1558                 if (replyopts.opt.opt.srr)
1559                         daddr = replyopts.opt.opt.faddr;
1560         }
1561 
1562         flowi4_init_output(&fl4, arg->bound_dev_if,
1563                            IP4_REPLY_MARK(net, skb->mark),
1564                            RT_TOS(arg->tos),
1565                            RT_SCOPE_UNIVERSE, ip_hdr(skb)->protocol,
1566                            ip_reply_arg_flowi_flags(arg),
1567                            daddr, saddr,
1568                            tcp_hdr(skb)->source, tcp_hdr(skb)->dest);
1569         security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
1570         rt = ip_route_output_key(net, &fl4);
1571         if (IS_ERR(rt))
1572                 return;
1573 
1574         inet_sk(sk)->tos = arg->tos;
1575 
1576         sk->sk_priority = skb->priority;
1577         sk->sk_protocol = ip_hdr(skb)->protocol;
1578         sk->sk_bound_dev_if = arg->bound_dev_if;
1579         sk->sk_sndbuf = sysctl_wmem_default;
1580         err = ip_append_data(sk, &fl4, ip_reply_glue_bits, arg->iov->iov_base,
1581                              len, 0, &ipc, &rt, MSG_DONTWAIT);
1582         if (unlikely(err)) {
1583                 ip_flush_pending_frames(sk);
1584                 goto out;
1585         }
1586 
1587         nskb = skb_peek(&sk->sk_write_queue);
1588         if (nskb) {
1589                 if (arg->csumoffset >= 0)
1590                         *((__sum16 *)skb_transport_header(nskb) +
1591                           arg->csumoffset) = csum_fold(csum_add(nskb->csum,
1592                                                                 arg->csum));
1593                 nskb->ip_summed = CHECKSUM_NONE;
1594                 skb_set_queue_mapping(nskb, skb_get_queue_mapping(skb));
1595                 ip_push_pending_frames(sk, &fl4);
1596         }
1597 out:
1598         ip_rt_put(rt);
1599 }
1600 
1601 void __init ip_init(void)
1602 {
1603         ip_rt_init();
1604         inet_initpeers();
1605 
1606 #if defined(CONFIG_IP_MULTICAST)
1607         igmp_mc_init();
1608 #endif
1609 }
1610 

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