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Linux/net/ipv4/ip_output.c

  1 /*
  2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
  3  *              operating system.  INET is implemented using the  BSD Socket
  4  *              interface as the means of communication with the user level.
  5  *
  6  *              The Internet Protocol (IP) output module.
  7  *
  8  * Authors:     Ross Biro
  9  *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 10  *              Donald Becker, <becker@super.org>
 11  *              Alan Cox, <Alan.Cox@linux.org>
 12  *              Richard Underwood
 13  *              Stefan Becker, <stefanb@yello.ping.de>
 14  *              Jorge Cwik, <jorge@laser.satlink.net>
 15  *              Arnt Gulbrandsen, <agulbra@nvg.unit.no>
 16  *              Hirokazu Takahashi, <taka@valinux.co.jp>
 17  *
 18  *      See ip_input.c for original log
 19  *
 20  *      Fixes:
 21  *              Alan Cox        :       Missing nonblock feature in ip_build_xmit.
 22  *              Mike Kilburn    :       htons() missing in ip_build_xmit.
 23  *              Bradford Johnson:       Fix faulty handling of some frames when
 24  *                                      no route is found.
 25  *              Alexander Demenshin:    Missing sk/skb free in ip_queue_xmit
 26  *                                      (in case if packet not accepted by
 27  *                                      output firewall rules)
 28  *              Mike McLagan    :       Routing by source
 29  *              Alexey Kuznetsov:       use new route cache
 30  *              Andi Kleen:             Fix broken PMTU recovery and remove
 31  *                                      some redundant tests.
 32  *      Vitaly E. Lavrov        :       Transparent proxy revived after year coma.
 33  *              Andi Kleen      :       Replace ip_reply with ip_send_reply.
 34  *              Andi Kleen      :       Split fast and slow ip_build_xmit path
 35  *                                      for decreased register pressure on x86
 36  *                                      and more readibility.
 37  *              Marc Boucher    :       When call_out_firewall returns FW_QUEUE,
 38  *                                      silently drop skb instead of failing with -EPERM.
 39  *              Detlev Wengorz  :       Copy protocol for fragments.
 40  *              Hirokazu Takahashi:     HW checksumming for outgoing UDP
 41  *                                      datagrams.
 42  *              Hirokazu Takahashi:     sendfile() on UDP works now.
 43  */
 44 
 45 #include <asm/uaccess.h>
 46 #include <linux/module.h>
 47 #include <linux/types.h>
 48 #include <linux/kernel.h>
 49 #include <linux/mm.h>
 50 #include <linux/string.h>
 51 #include <linux/errno.h>
 52 #include <linux/highmem.h>
 53 #include <linux/slab.h>
 54 
 55 #include <linux/socket.h>
 56 #include <linux/sockios.h>
 57 #include <linux/in.h>
 58 #include <linux/inet.h>
 59 #include <linux/netdevice.h>
 60 #include <linux/etherdevice.h>
 61 #include <linux/proc_fs.h>
 62 #include <linux/stat.h>
 63 #include <linux/init.h>
 64 
 65 #include <net/snmp.h>
 66 #include <net/ip.h>
 67 #include <net/protocol.h>
 68 #include <net/route.h>
 69 #include <net/xfrm.h>
 70 #include <linux/skbuff.h>
 71 #include <net/sock.h>
 72 #include <net/arp.h>
 73 #include <net/icmp.h>
 74 #include <net/checksum.h>
 75 #include <net/inetpeer.h>
 76 #include <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 /* Generate a checksum for an outgoing IP datagram. */
 87 void ip_send_check(struct iphdr *iph)
 88 {
 89         iph->check = 0;
 90         iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
 91 }
 92 EXPORT_SYMBOL(ip_send_check);
 93 
 94 int __ip_local_out(struct sk_buff *skb)
 95 {
 96         struct iphdr *iph = ip_hdr(skb);
 97 
 98         iph->tot_len = htons(skb->len);
 99         ip_send_check(iph);
100         return nf_hook(NFPROTO_IPV4, NF_INET_LOCAL_OUT, skb, NULL,
101                        skb_dst(skb)->dev, dst_output);
102 }
103 
104 int ip_local_out_sk(struct sock *sk, struct sk_buff *skb)
105 {
106         int err;
107 
108         err = __ip_local_out(skb);
109         if (likely(err == 1))
110                 err = dst_output_sk(sk, skb);
111 
112         return err;
113 }
114 EXPORT_SYMBOL_GPL(ip_local_out_sk);
115 
116 static inline int ip_select_ttl(struct inet_sock *inet, struct dst_entry *dst)
117 {
118         int ttl = inet->uc_ttl;
119 
120         if (ttl < 0)
121                 ttl = ip4_dst_hoplimit(dst);
122         return ttl;
123 }
124 
125 /*
126  *              Add an ip header to a skbuff and send it out.
127  *
128  */
129 int ip_build_and_send_pkt(struct sk_buff *skb, struct sock *sk,
130                           __be32 saddr, __be32 daddr, struct ip_options_rcu *opt)
131 {
132         struct inet_sock *inet = inet_sk(sk);
133         struct rtable *rt = skb_rtable(skb);
134         struct iphdr *iph;
135 
136         /* Build the IP header. */
137         skb_push(skb, sizeof(struct iphdr) + (opt ? opt->opt.optlen : 0));
138         skb_reset_network_header(skb);
139         iph = ip_hdr(skb);
140         iph->version  = 4;
141         iph->ihl      = 5;
142         iph->tos      = inet->tos;
143         if (ip_dont_fragment(sk, &rt->dst))
144                 iph->frag_off = htons(IP_DF);
145         else
146                 iph->frag_off = 0;
147         iph->ttl      = ip_select_ttl(inet, &rt->dst);
148         iph->daddr    = (opt && opt->opt.srr ? opt->opt.faddr : daddr);
149         iph->saddr    = saddr;
150         iph->protocol = sk->sk_protocol;
151         ip_select_ident(skb, &rt->dst, sk);
152 
153         if (opt && opt->opt.optlen) {
154                 iph->ihl += opt->opt.optlen>>2;
155                 ip_options_build(skb, &opt->opt, daddr, rt, 0);
156         }
157 
158         skb->priority = sk->sk_priority;
159         skb->mark = sk->sk_mark;
160 
161         /* Send it out. */
162         return ip_local_out(skb);
163 }
164 EXPORT_SYMBOL_GPL(ip_build_and_send_pkt);
165 
166 static inline int ip_finish_output2(struct sk_buff *skb)
167 {
168         struct dst_entry *dst = skb_dst(skb);
169         struct rtable *rt = (struct rtable *)dst;
170         struct net_device *dev = dst->dev;
171         unsigned int hh_len = LL_RESERVED_SPACE(dev);
172         struct neighbour *neigh;
173         u32 nexthop;
174 
175         if (rt->rt_type == RTN_MULTICAST) {
176                 IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUTMCAST, skb->len);
177         } else if (rt->rt_type == RTN_BROADCAST)
178                 IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUTBCAST, skb->len);
179 
180         /* Be paranoid, rather than too clever. */
181         if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) {
182                 struct sk_buff *skb2;
183 
184                 skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev));
185                 if (skb2 == NULL) {
186                         kfree_skb(skb);
187                         return -ENOMEM;
188                 }
189                 if (skb->sk)
190                         skb_set_owner_w(skb2, skb->sk);
191                 consume_skb(skb);
192                 skb = skb2;
193         }
194 
195         rcu_read_lock_bh();
196         nexthop = (__force u32) rt_nexthop(rt, ip_hdr(skb)->daddr);
197         neigh = __ipv4_neigh_lookup_noref(dev, nexthop);
198         if (unlikely(!neigh))
199                 neigh = __neigh_create(&arp_tbl, &nexthop, dev, false);
200         if (!IS_ERR(neigh)) {
201                 int res = dst_neigh_output(dst, neigh, skb);
202 
203                 rcu_read_unlock_bh();
204                 return res;
205         }
206         rcu_read_unlock_bh();
207 
208         net_dbg_ratelimited("%s: No header cache and no neighbour!\n",
209                             __func__);
210         kfree_skb(skb);
211         return -EINVAL;
212 }
213 
214 static int ip_finish_output_gso(struct sk_buff *skb)
215 {
216         netdev_features_t features;
217         struct sk_buff *segs;
218         int ret = 0;
219 
220         /* common case: locally created skb or seglen is <= mtu */
221         if (((IPCB(skb)->flags & IPSKB_FORWARDED) == 0) ||
222               skb_gso_network_seglen(skb) <= ip_skb_dst_mtu(skb))
223                 return ip_finish_output2(skb);
224 
225         /* Slowpath -  GSO segment length is exceeding the dst MTU.
226          *
227          * This can happen in two cases:
228          * 1) TCP GRO packet, DF bit not set
229          * 2) skb arrived via virtio-net, we thus get TSO/GSO skbs directly
230          * from host network stack.
231          */
232         features = netif_skb_features(skb);
233         segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK);
234         if (IS_ERR(segs)) {
235                 kfree_skb(skb);
236                 return -ENOMEM;
237         }
238 
239         consume_skb(skb);
240 
241         do {
242                 struct sk_buff *nskb = segs->next;
243                 int err;
244 
245                 segs->next = NULL;
246                 err = ip_fragment(segs, ip_finish_output2);
247 
248                 if (err && ret == 0)
249                         ret = err;
250                 segs = nskb;
251         } while (segs);
252 
253         return ret;
254 }
255 
256 static int ip_finish_output(struct sk_buff *skb)
257 {
258 #if defined(CONFIG_NETFILTER) && defined(CONFIG_XFRM)
259         /* Policy lookup after SNAT yielded a new policy */
260         if (skb_dst(skb)->xfrm != NULL) {
261                 IPCB(skb)->flags |= IPSKB_REROUTED;
262                 return dst_output(skb);
263         }
264 #endif
265         if (skb_is_gso(skb))
266                 return ip_finish_output_gso(skb);
267 
268         if (skb->len > ip_skb_dst_mtu(skb))
269                 return ip_fragment(skb, ip_finish_output2);
270 
271         return ip_finish_output2(skb);
272 }
273 
274 int ip_mc_output(struct sock *sk, struct sk_buff *skb)
275 {
276         struct rtable *rt = skb_rtable(skb);
277         struct net_device *dev = rt->dst.dev;
278 
279         /*
280          *      If the indicated interface is up and running, send the packet.
281          */
282         IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUT, skb->len);
283 
284         skb->dev = dev;
285         skb->protocol = htons(ETH_P_IP);
286 
287         /*
288          *      Multicasts are looped back for other local users
289          */
290 
291         if (rt->rt_flags&RTCF_MULTICAST) {
292                 if (sk_mc_loop(sk)
293 #ifdef CONFIG_IP_MROUTE
294                 /* Small optimization: do not loopback not local frames,
295                    which returned after forwarding; they will be  dropped
296                    by ip_mr_input in any case.
297                    Note, that local frames are looped back to be delivered
298                    to local recipients.
299 
300                    This check is duplicated in ip_mr_input at the moment.
301                  */
302                     &&
303                     ((rt->rt_flags & RTCF_LOCAL) ||
304                      !(IPCB(skb)->flags & IPSKB_FORWARDED))
305 #endif
306                    ) {
307                         struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
308                         if (newskb)
309                                 NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING,
310                                         newskb, NULL, newskb->dev,
311                                         dev_loopback_xmit);
312                 }
313 
314                 /* Multicasts with ttl 0 must not go beyond the host */
315 
316                 if (ip_hdr(skb)->ttl == 0) {
317                         kfree_skb(skb);
318                         return 0;
319                 }
320         }
321 
322         if (rt->rt_flags&RTCF_BROADCAST) {
323                 struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
324                 if (newskb)
325                         NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING, newskb,
326                                 NULL, newskb->dev, dev_loopback_xmit);
327         }
328 
329         return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING, skb, NULL,
330                             skb->dev, ip_finish_output,
331                             !(IPCB(skb)->flags & IPSKB_REROUTED));
332 }
333 
334 int ip_output(struct sock *sk, struct sk_buff *skb)
335 {
336         struct net_device *dev = skb_dst(skb)->dev;
337 
338         IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUT, skb->len);
339 
340         skb->dev = dev;
341         skb->protocol = htons(ETH_P_IP);
342 
343         return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING, skb, NULL, dev,
344                             ip_finish_output,
345                             !(IPCB(skb)->flags & IPSKB_REROUTED));
346 }
347 
348 /*
349  * copy saddr and daddr, possibly using 64bit load/stores
350  * Equivalent to :
351  *   iph->saddr = fl4->saddr;
352  *   iph->daddr = fl4->daddr;
353  */
354 static void ip_copy_addrs(struct iphdr *iph, const struct flowi4 *fl4)
355 {
356         BUILD_BUG_ON(offsetof(typeof(*fl4), daddr) !=
357                      offsetof(typeof(*fl4), saddr) + sizeof(fl4->saddr));
358         memcpy(&iph->saddr, &fl4->saddr,
359                sizeof(fl4->saddr) + sizeof(fl4->daddr));
360 }
361 
362 /* Note: skb->sk can be different from sk, in case of tunnels */
363 int ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl)
364 {
365         struct inet_sock *inet = inet_sk(sk);
366         struct ip_options_rcu *inet_opt;
367         struct flowi4 *fl4;
368         struct rtable *rt;
369         struct iphdr *iph;
370         int res;
371 
372         /* Skip all of this if the packet is already routed,
373          * f.e. by something like SCTP.
374          */
375         rcu_read_lock();
376         inet_opt = rcu_dereference(inet->inet_opt);
377         fl4 = &fl->u.ip4;
378         rt = skb_rtable(skb);
379         if (rt != NULL)
380                 goto packet_routed;
381 
382         /* Make sure we can route this packet. */
383         rt = (struct rtable *)__sk_dst_check(sk, 0);
384         if (rt == NULL) {
385                 __be32 daddr;
386 
387                 /* Use correct destination address if we have options. */
388                 daddr = inet->inet_daddr;
389                 if (inet_opt && inet_opt->opt.srr)
390                         daddr = inet_opt->opt.faddr;
391 
392                 /* If this fails, retransmit mechanism of transport layer will
393                  * keep trying until route appears or the connection times
394                  * itself out.
395                  */
396                 rt = ip_route_output_ports(sock_net(sk), fl4, sk,
397                                            daddr, inet->inet_saddr,
398                                            inet->inet_dport,
399                                            inet->inet_sport,
400                                            sk->sk_protocol,
401                                            RT_CONN_FLAGS(sk),
402                                            sk->sk_bound_dev_if);
403                 if (IS_ERR(rt))
404                         goto no_route;
405                 sk_setup_caps(sk, &rt->dst);
406         }
407         skb_dst_set_noref(skb, &rt->dst);
408 
409 packet_routed:
410         if (inet_opt && inet_opt->opt.is_strictroute && rt->rt_uses_gateway)
411                 goto no_route;
412 
413         /* OK, we know where to send it, allocate and build IP header. */
414         skb_push(skb, sizeof(struct iphdr) + (inet_opt ? inet_opt->opt.optlen : 0));
415         skb_reset_network_header(skb);
416         iph = ip_hdr(skb);
417         *((__be16 *)iph) = htons((4 << 12) | (5 << 8) | (inet->tos & 0xff));
418         if (ip_dont_fragment(sk, &rt->dst) && !skb->local_df)
419                 iph->frag_off = htons(IP_DF);
420         else
421                 iph->frag_off = 0;
422         iph->ttl      = ip_select_ttl(inet, &rt->dst);
423         iph->protocol = sk->sk_protocol;
424         ip_copy_addrs(iph, fl4);
425 
426         /* Transport layer set skb->h.foo itself. */
427 
428         if (inet_opt && inet_opt->opt.optlen) {
429                 iph->ihl += inet_opt->opt.optlen >> 2;
430                 ip_options_build(skb, &inet_opt->opt, inet->inet_daddr, rt, 0);
431         }
432 
433         ip_select_ident_more(skb, &rt->dst, sk,
434                              (skb_shinfo(skb)->gso_segs ?: 1) - 1);
435 
436         /* TODO : should we use skb->sk here instead of sk ? */
437         skb->priority = sk->sk_priority;
438         skb->mark = sk->sk_mark;
439 
440         res = ip_local_out(skb);
441         rcu_read_unlock();
442         return res;
443 
444 no_route:
445         rcu_read_unlock();
446         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);
447         kfree_skb(skb);
448         return -EHOSTUNREACH;
449 }
450 EXPORT_SYMBOL(ip_queue_xmit);
451 
452 
453 static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
454 {
455         to->pkt_type = from->pkt_type;
456         to->priority = from->priority;
457         to->protocol = from->protocol;
458         skb_dst_drop(to);
459         skb_dst_copy(to, from);
460         to->dev = from->dev;
461         to->mark = from->mark;
462 
463         /* Copy the flags to each fragment. */
464         IPCB(to)->flags = IPCB(from)->flags;
465 
466 #ifdef CONFIG_NET_SCHED
467         to->tc_index = from->tc_index;
468 #endif
469         nf_copy(to, from);
470 #if defined(CONFIG_IP_VS) || defined(CONFIG_IP_VS_MODULE)
471         to->ipvs_property = from->ipvs_property;
472 #endif
473         skb_copy_secmark(to, from);
474 }
475 
476 /*
477  *      This IP datagram is too large to be sent in one piece.  Break it up into
478  *      smaller pieces (each of size equal to IP header plus
479  *      a block of the data of the original IP data part) that will yet fit in a
480  *      single device frame, and queue such a frame for sending.
481  */
482 
483 int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
484 {
485         struct iphdr *iph;
486         int ptr;
487         struct net_device *dev;
488         struct sk_buff *skb2;
489         unsigned int mtu, hlen, left, len, ll_rs;
490         int offset;
491         __be16 not_last_frag;
492         struct rtable *rt = skb_rtable(skb);
493         int err = 0;
494 
495         dev = rt->dst.dev;
496 
497         /*
498          *      Point into the IP datagram header.
499          */
500 
501         iph = ip_hdr(skb);
502 
503         mtu = ip_skb_dst_mtu(skb);
504         if (unlikely(((iph->frag_off & htons(IP_DF)) && !skb->local_df) ||
505                      (IPCB(skb)->frag_max_size &&
506                       IPCB(skb)->frag_max_size > mtu))) {
507                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
508                 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
509                           htonl(mtu));
510                 kfree_skb(skb);
511                 return -EMSGSIZE;
512         }
513 
514         /*
515          *      Setup starting values.
516          */
517 
518         hlen = iph->ihl * 4;
519         mtu = mtu - hlen;       /* Size of data space */
520 #ifdef CONFIG_BRIDGE_NETFILTER
521         if (skb->nf_bridge)
522                 mtu -= nf_bridge_mtu_reduction(skb);
523 #endif
524         IPCB(skb)->flags |= IPSKB_FRAG_COMPLETE;
525 
526         /* When frag_list is given, use it. First, check its validity:
527          * some transformers could create wrong frag_list or break existing
528          * one, it is not prohibited. In this case fall back to copying.
529          *
530          * LATER: this step can be merged to real generation of fragments,
531          * we can switch to copy when see the first bad fragment.
532          */
533         if (skb_has_frag_list(skb)) {
534                 struct sk_buff *frag, *frag2;
535                 int first_len = skb_pagelen(skb);
536 
537                 if (first_len - hlen > mtu ||
538                     ((first_len - hlen) & 7) ||
539                     ip_is_fragment(iph) ||
540                     skb_cloned(skb))
541                         goto slow_path;
542 
543                 skb_walk_frags(skb, frag) {
544                         /* Correct geometry. */
545                         if (frag->len > mtu ||
546                             ((frag->len & 7) && frag->next) ||
547                             skb_headroom(frag) < hlen)
548                                 goto slow_path_clean;
549 
550                         /* Partially cloned skb? */
551                         if (skb_shared(frag))
552                                 goto slow_path_clean;
553 
554                         BUG_ON(frag->sk);
555                         if (skb->sk) {
556                                 frag->sk = skb->sk;
557                                 frag->destructor = sock_wfree;
558                         }
559                         skb->truesize -= frag->truesize;
560                 }
561 
562                 /* Everything is OK. Generate! */
563 
564                 err = 0;
565                 offset = 0;
566                 frag = skb_shinfo(skb)->frag_list;
567                 skb_frag_list_init(skb);
568                 skb->data_len = first_len - skb_headlen(skb);
569                 skb->len = first_len;
570                 iph->tot_len = htons(first_len);
571                 iph->frag_off = htons(IP_MF);
572                 ip_send_check(iph);
573 
574                 for (;;) {
575                         /* Prepare header of the next frame,
576                          * before previous one went down. */
577                         if (frag) {
578                                 frag->ip_summed = CHECKSUM_NONE;
579                                 skb_reset_transport_header(frag);
580                                 __skb_push(frag, hlen);
581                                 skb_reset_network_header(frag);
582                                 memcpy(skb_network_header(frag), iph, hlen);
583                                 iph = ip_hdr(frag);
584                                 iph->tot_len = htons(frag->len);
585                                 ip_copy_metadata(frag, skb);
586                                 if (offset == 0)
587                                         ip_options_fragment(frag);
588                                 offset += skb->len - hlen;
589                                 iph->frag_off = htons(offset>>3);
590                                 if (frag->next != NULL)
591                                         iph->frag_off |= htons(IP_MF);
592                                 /* Ready, complete checksum */
593                                 ip_send_check(iph);
594                         }
595 
596                         err = output(skb);
597 
598                         if (!err)
599                                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGCREATES);
600                         if (err || !frag)
601                                 break;
602 
603                         skb = frag;
604                         frag = skb->next;
605                         skb->next = NULL;
606                 }
607 
608                 if (err == 0) {
609                         IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGOKS);
610                         return 0;
611                 }
612 
613                 while (frag) {
614                         skb = frag->next;
615                         kfree_skb(frag);
616                         frag = skb;
617                 }
618                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
619                 return err;
620 
621 slow_path_clean:
622                 skb_walk_frags(skb, frag2) {
623                         if (frag2 == frag)
624                                 break;
625                         frag2->sk = NULL;
626                         frag2->destructor = NULL;
627                         skb->truesize += frag2->truesize;
628                 }
629         }
630 
631 slow_path:
632         /* for offloaded checksums cleanup checksum before fragmentation */
633         if ((skb->ip_summed == CHECKSUM_PARTIAL) && skb_checksum_help(skb))
634                 goto fail;
635         iph = ip_hdr(skb);
636 
637         left = skb->len - hlen;         /* Space per frame */
638         ptr = hlen;             /* Where to start from */
639 
640         /* for bridged IP traffic encapsulated inside f.e. a vlan header,
641          * we need to make room for the encapsulating header
642          */
643         ll_rs = LL_RESERVED_SPACE_EXTRA(rt->dst.dev, nf_bridge_pad(skb));
644 
645         /*
646          *      Fragment the datagram.
647          */
648 
649         offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3;
650         not_last_frag = iph->frag_off & htons(IP_MF);
651 
652         /*
653          *      Keep copying data until we run out.
654          */
655 
656         while (left > 0) {
657                 len = left;
658                 /* IF: it doesn't fit, use 'mtu' - the data space left */
659                 if (len > mtu)
660                         len = mtu;
661                 /* IF: we are not sending up to and including the packet end
662                    then align the next start on an eight byte boundary */
663                 if (len < left) {
664                         len &= ~7;
665                 }
666                 /*
667                  *      Allocate buffer.
668                  */
669 
670                 if ((skb2 = alloc_skb(len+hlen+ll_rs, GFP_ATOMIC)) == NULL) {
671                         NETDEBUG(KERN_INFO "IP: frag: no memory for new fragment!\n");
672                         err = -ENOMEM;
673                         goto fail;
674                 }
675 
676                 /*
677                  *      Set up data on packet
678                  */
679 
680                 ip_copy_metadata(skb2, skb);
681                 skb_reserve(skb2, ll_rs);
682                 skb_put(skb2, len + hlen);
683                 skb_reset_network_header(skb2);
684                 skb2->transport_header = skb2->network_header + hlen;
685 
686                 /*
687                  *      Charge the memory for the fragment to any owner
688                  *      it might possess
689                  */
690 
691                 if (skb->sk)
692                         skb_set_owner_w(skb2, skb->sk);
693 
694                 /*
695                  *      Copy the packet header into the new buffer.
696                  */
697 
698                 skb_copy_from_linear_data(skb, skb_network_header(skb2), hlen);
699 
700                 /*
701                  *      Copy a block of the IP datagram.
702                  */
703                 if (skb_copy_bits(skb, ptr, skb_transport_header(skb2), len))
704                         BUG();
705                 left -= len;
706 
707                 /*
708                  *      Fill in the new header fields.
709                  */
710                 iph = ip_hdr(skb2);
711                 iph->frag_off = htons((offset >> 3));
712 
713                 /* ANK: dirty, but effective trick. Upgrade options only if
714                  * the segment to be fragmented was THE FIRST (otherwise,
715                  * options are already fixed) and make it ONCE
716                  * on the initial skb, so that all the following fragments
717                  * will inherit fixed options.
718                  */
719                 if (offset == 0)
720                         ip_options_fragment(skb);
721 
722                 /*
723                  *      Added AC : If we are fragmenting a fragment that's not the
724                  *                 last fragment then keep MF on each bit
725                  */
726                 if (left > 0 || not_last_frag)
727                         iph->frag_off |= htons(IP_MF);
728                 ptr += len;
729                 offset += len;
730 
731                 /*
732                  *      Put this fragment into the sending queue.
733                  */
734                 iph->tot_len = htons(len + hlen);
735 
736                 ip_send_check(iph);
737 
738                 err = output(skb2);
739                 if (err)
740                         goto fail;
741 
742                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGCREATES);
743         }
744         consume_skb(skb);
745         IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGOKS);
746         return err;
747 
748 fail:
749         kfree_skb(skb);
750         IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
751         return err;
752 }
753 EXPORT_SYMBOL(ip_fragment);
754 
755 int
756 ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
757 {
758         struct iovec *iov = from;
759 
760         if (skb->ip_summed == CHECKSUM_PARTIAL) {
761                 if (memcpy_fromiovecend(to, iov, offset, len) < 0)
762                         return -EFAULT;
763         } else {
764                 __wsum csum = 0;
765                 if (csum_partial_copy_fromiovecend(to, iov, offset, len, &csum) < 0)
766                         return -EFAULT;
767                 skb->csum = csum_block_add(skb->csum, csum, odd);
768         }
769         return 0;
770 }
771 EXPORT_SYMBOL(ip_generic_getfrag);
772 
773 static inline __wsum
774 csum_page(struct page *page, int offset, int copy)
775 {
776         char *kaddr;
777         __wsum csum;
778         kaddr = kmap(page);
779         csum = csum_partial(kaddr + offset, copy, 0);
780         kunmap(page);
781         return csum;
782 }
783 
784 static inline int ip_ufo_append_data(struct sock *sk,
785                         struct sk_buff_head *queue,
786                         int getfrag(void *from, char *to, int offset, int len,
787                                int odd, struct sk_buff *skb),
788                         void *from, int length, int hh_len, int fragheaderlen,
789                         int transhdrlen, int maxfraglen, unsigned int flags)
790 {
791         struct sk_buff *skb;
792         int err;
793 
794         /* There is support for UDP fragmentation offload by network
795          * device, so create one single skb packet containing complete
796          * udp datagram
797          */
798         if ((skb = skb_peek_tail(queue)) == NULL) {
799                 skb = sock_alloc_send_skb(sk,
800                         hh_len + fragheaderlen + transhdrlen + 20,
801                         (flags & MSG_DONTWAIT), &err);
802 
803                 if (skb == NULL)
804                         return err;
805 
806                 /* reserve space for Hardware header */
807                 skb_reserve(skb, hh_len);
808 
809                 /* create space for UDP/IP header */
810                 skb_put(skb, fragheaderlen + transhdrlen);
811 
812                 /* initialize network header pointer */
813                 skb_reset_network_header(skb);
814 
815                 /* initialize protocol header pointer */
816                 skb->transport_header = skb->network_header + fragheaderlen;
817 
818                 skb->csum = 0;
819 
820 
821                 __skb_queue_tail(queue, skb);
822         } else if (skb_is_gso(skb)) {
823                 goto append;
824         }
825 
826         skb->ip_summed = CHECKSUM_PARTIAL;
827         /* specify the length of each IP datagram fragment */
828         skb_shinfo(skb)->gso_size = maxfraglen - fragheaderlen;
829         skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
830 
831 append:
832         return skb_append_datato_frags(sk, skb, getfrag, from,
833                                        (length - transhdrlen));
834 }
835 
836 static int __ip_append_data(struct sock *sk,
837                             struct flowi4 *fl4,
838                             struct sk_buff_head *queue,
839                             struct inet_cork *cork,
840                             struct page_frag *pfrag,
841                             int getfrag(void *from, char *to, int offset,
842                                         int len, int odd, struct sk_buff *skb),
843                             void *from, int length, int transhdrlen,
844                             unsigned int flags)
845 {
846         struct inet_sock *inet = inet_sk(sk);
847         struct sk_buff *skb;
848 
849         struct ip_options *opt = cork->opt;
850         int hh_len;
851         int exthdrlen;
852         int mtu;
853         int copy;
854         int err;
855         int offset = 0;
856         unsigned int maxfraglen, fragheaderlen, maxnonfragsize;
857         int csummode = CHECKSUM_NONE;
858         struct rtable *rt = (struct rtable *)cork->dst;
859 
860         skb = skb_peek_tail(queue);
861 
862         exthdrlen = !skb ? rt->dst.header_len : 0;
863         mtu = cork->fragsize;
864 
865         hh_len = LL_RESERVED_SPACE(rt->dst.dev);
866 
867         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
868         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
869         maxnonfragsize = ip_sk_local_df(sk) ? 0xFFFF : mtu;
870 
871         if (cork->length + length > maxnonfragsize - fragheaderlen) {
872                 ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
873                                mtu - (opt ? opt->optlen : 0));
874                 return -EMSGSIZE;
875         }
876 
877         /*
878          * transhdrlen > 0 means that this is the first fragment and we wish
879          * it won't be fragmented in the future.
880          */
881         if (transhdrlen &&
882             length + fragheaderlen <= mtu &&
883             rt->dst.dev->features & NETIF_F_V4_CSUM &&
884             !exthdrlen)
885                 csummode = CHECKSUM_PARTIAL;
886 
887         cork->length += length;
888         if (((length > mtu) || (skb && skb_is_gso(skb))) &&
889             (sk->sk_protocol == IPPROTO_UDP) &&
890             (rt->dst.dev->features & NETIF_F_UFO) && !rt->dst.header_len) {
891                 err = ip_ufo_append_data(sk, queue, getfrag, from, length,
892                                          hh_len, fragheaderlen, transhdrlen,
893                                          maxfraglen, flags);
894                 if (err)
895                         goto error;
896                 return 0;
897         }
898 
899         /* So, what's going on in the loop below?
900          *
901          * We use calculated fragment length to generate chained skb,
902          * each of segments is IP fragment ready for sending to network after
903          * adding appropriate IP header.
904          */
905 
906         if (!skb)
907                 goto alloc_new_skb;
908 
909         while (length > 0) {
910                 /* Check if the remaining data fits into current packet. */
911                 copy = mtu - skb->len;
912                 if (copy < length)
913                         copy = maxfraglen - skb->len;
914                 if (copy <= 0) {
915                         char *data;
916                         unsigned int datalen;
917                         unsigned int fraglen;
918                         unsigned int fraggap;
919                         unsigned int alloclen;
920                         struct sk_buff *skb_prev;
921 alloc_new_skb:
922                         skb_prev = skb;
923                         if (skb_prev)
924                                 fraggap = skb_prev->len - maxfraglen;
925                         else
926                                 fraggap = 0;
927 
928                         /*
929                          * If remaining data exceeds the mtu,
930                          * we know we need more fragment(s).
931                          */
932                         datalen = length + fraggap;
933                         if (datalen > mtu - fragheaderlen)
934                                 datalen = maxfraglen - fragheaderlen;
935                         fraglen = datalen + fragheaderlen;
936 
937                         if ((flags & MSG_MORE) &&
938                             !(rt->dst.dev->features&NETIF_F_SG))
939                                 alloclen = mtu;
940                         else
941                                 alloclen = fraglen;
942 
943                         alloclen += exthdrlen;
944 
945                         /* The last fragment gets additional space at tail.
946                          * Note, with MSG_MORE we overallocate on fragments,
947                          * because we have no idea what fragment will be
948                          * the last.
949                          */
950                         if (datalen == length + fraggap)
951                                 alloclen += rt->dst.trailer_len;
952 
953                         if (transhdrlen) {
954                                 skb = sock_alloc_send_skb(sk,
955                                                 alloclen + hh_len + 15,
956                                                 (flags & MSG_DONTWAIT), &err);
957                         } else {
958                                 skb = NULL;
959                                 if (atomic_read(&sk->sk_wmem_alloc) <=
960                                     2 * sk->sk_sndbuf)
961                                         skb = sock_wmalloc(sk,
962                                                            alloclen + hh_len + 15, 1,
963                                                            sk->sk_allocation);
964                                 if (unlikely(skb == NULL))
965                                         err = -ENOBUFS;
966                                 else
967                                         /* only the initial fragment is
968                                            time stamped */
969                                         cork->tx_flags = 0;
970                         }
971                         if (skb == NULL)
972                                 goto error;
973 
974                         /*
975                          *      Fill in the control structures
976                          */
977                         skb->ip_summed = csummode;
978                         skb->csum = 0;
979                         skb_reserve(skb, hh_len);
980                         skb_shinfo(skb)->tx_flags = cork->tx_flags;
981 
982                         /*
983                          *      Find where to start putting bytes.
984                          */
985                         data = skb_put(skb, fraglen + exthdrlen);
986                         skb_set_network_header(skb, exthdrlen);
987                         skb->transport_header = (skb->network_header +
988                                                  fragheaderlen);
989                         data += fragheaderlen + exthdrlen;
990 
991                         if (fraggap) {
992                                 skb->csum = skb_copy_and_csum_bits(
993                                         skb_prev, maxfraglen,
994                                         data + transhdrlen, fraggap, 0);
995                                 skb_prev->csum = csum_sub(skb_prev->csum,
996                                                           skb->csum);
997                                 data += fraggap;
998                                 pskb_trim_unique(skb_prev, maxfraglen);
999                         }
1000 
1001                         copy = datalen - transhdrlen - fraggap;
1002                         if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
1003                                 err = -EFAULT;
1004                                 kfree_skb(skb);
1005                                 goto error;
1006                         }
1007 
1008                         offset += copy;
1009                         length -= datalen - fraggap;
1010                         transhdrlen = 0;
1011                         exthdrlen = 0;
1012                         csummode = CHECKSUM_NONE;
1013 
1014                         /*
1015                          * Put the packet on the pending queue.
1016                          */
1017                         __skb_queue_tail(queue, skb);
1018                         continue;
1019                 }
1020 
1021                 if (copy > length)
1022                         copy = length;
1023 
1024                 if (!(rt->dst.dev->features&NETIF_F_SG)) {
1025                         unsigned int off;
1026 
1027                         off = skb->len;
1028                         if (getfrag(from, skb_put(skb, copy),
1029                                         offset, copy, off, skb) < 0) {
1030                                 __skb_trim(skb, off);
1031                                 err = -EFAULT;
1032                                 goto error;
1033                         }
1034                 } else {
1035                         int i = skb_shinfo(skb)->nr_frags;
1036 
1037                         err = -ENOMEM;
1038                         if (!sk_page_frag_refill(sk, pfrag))
1039                                 goto error;
1040 
1041                         if (!skb_can_coalesce(skb, i, pfrag->page,
1042                                               pfrag->offset)) {
1043                                 err = -EMSGSIZE;
1044                                 if (i == MAX_SKB_FRAGS)
1045                                         goto error;
1046 
1047                                 __skb_fill_page_desc(skb, i, pfrag->page,
1048                                                      pfrag->offset, 0);
1049                                 skb_shinfo(skb)->nr_frags = ++i;
1050                                 get_page(pfrag->page);
1051                         }
1052                         copy = min_t(int, copy, pfrag->size - pfrag->offset);
1053                         if (getfrag(from,
1054                                     page_address(pfrag->page) + pfrag->offset,
1055                                     offset, copy, skb->len, skb) < 0)
1056                                 goto error_efault;
1057 
1058                         pfrag->offset += copy;
1059                         skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
1060                         skb->len += copy;
1061                         skb->data_len += copy;
1062                         skb->truesize += copy;
1063                         atomic_add(copy, &sk->sk_wmem_alloc);
1064                 }
1065                 offset += copy;
1066                 length -= copy;
1067         }
1068 
1069         return 0;
1070 
1071 error_efault:
1072         err = -EFAULT;
1073 error:
1074         cork->length -= length;
1075         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1076         return err;
1077 }
1078 
1079 static int ip_setup_cork(struct sock *sk, struct inet_cork *cork,
1080                          struct ipcm_cookie *ipc, struct rtable **rtp)
1081 {
1082         struct ip_options_rcu *opt;
1083         struct rtable *rt;
1084 
1085         /*
1086          * setup for corking.
1087          */
1088         opt = ipc->opt;
1089         if (opt) {
1090                 if (cork->opt == NULL) {
1091                         cork->opt = kmalloc(sizeof(struct ip_options) + 40,
1092                                             sk->sk_allocation);
1093                         if (unlikely(cork->opt == NULL))
1094                                 return -ENOBUFS;
1095                 }
1096                 memcpy(cork->opt, &opt->opt, sizeof(struct ip_options) + opt->opt.optlen);
1097                 cork->flags |= IPCORK_OPT;
1098                 cork->addr = ipc->addr;
1099         }
1100         rt = *rtp;
1101         if (unlikely(!rt))
1102                 return -EFAULT;
1103         /*
1104          * We steal reference to this route, caller should not release it
1105          */
1106         *rtp = NULL;
1107         cork->fragsize = ip_sk_use_pmtu(sk) ?
1108                          dst_mtu(&rt->dst) : rt->dst.dev->mtu;
1109         cork->dst = &rt->dst;
1110         cork->length = 0;
1111         cork->ttl = ipc->ttl;
1112         cork->tos = ipc->tos;
1113         cork->priority = ipc->priority;
1114         cork->tx_flags = ipc->tx_flags;
1115 
1116         return 0;
1117 }
1118 
1119 /*
1120  *      ip_append_data() and ip_append_page() can make one large IP datagram
1121  *      from many pieces of data. Each pieces will be holded on the socket
1122  *      until ip_push_pending_frames() is called. Each piece can be a page
1123  *      or non-page data.
1124  *
1125  *      Not only UDP, other transport protocols - e.g. raw sockets - can use
1126  *      this interface potentially.
1127  *
1128  *      LATER: length must be adjusted by pad at tail, when it is required.
1129  */
1130 int ip_append_data(struct sock *sk, struct flowi4 *fl4,
1131                    int getfrag(void *from, char *to, int offset, int len,
1132                                int odd, struct sk_buff *skb),
1133                    void *from, int length, int transhdrlen,
1134                    struct ipcm_cookie *ipc, struct rtable **rtp,
1135                    unsigned int flags)
1136 {
1137         struct inet_sock *inet = inet_sk(sk);
1138         int err;
1139 
1140         if (flags&MSG_PROBE)
1141                 return 0;
1142 
1143         if (skb_queue_empty(&sk->sk_write_queue)) {
1144                 err = ip_setup_cork(sk, &inet->cork.base, ipc, rtp);
1145                 if (err)
1146                         return err;
1147         } else {
1148                 transhdrlen = 0;
1149         }
1150 
1151         return __ip_append_data(sk, fl4, &sk->sk_write_queue, &inet->cork.base,
1152                                 sk_page_frag(sk), getfrag,
1153                                 from, length, transhdrlen, flags);
1154 }
1155 
1156 ssize_t ip_append_page(struct sock *sk, struct flowi4 *fl4, struct page *page,
1157                        int offset, size_t size, int flags)
1158 {
1159         struct inet_sock *inet = inet_sk(sk);
1160         struct sk_buff *skb;
1161         struct rtable *rt;
1162         struct ip_options *opt = NULL;
1163         struct inet_cork *cork;
1164         int hh_len;
1165         int mtu;
1166         int len;
1167         int err;
1168         unsigned int maxfraglen, fragheaderlen, fraggap, maxnonfragsize;
1169 
1170         if (inet->hdrincl)
1171                 return -EPERM;
1172 
1173         if (flags&MSG_PROBE)
1174                 return 0;
1175 
1176         if (skb_queue_empty(&sk->sk_write_queue))
1177                 return -EINVAL;
1178 
1179         cork = &inet->cork.base;
1180         rt = (struct rtable *)cork->dst;
1181         if (cork->flags & IPCORK_OPT)
1182                 opt = cork->opt;
1183 
1184         if (!(rt->dst.dev->features&NETIF_F_SG))
1185                 return -EOPNOTSUPP;
1186 
1187         hh_len = LL_RESERVED_SPACE(rt->dst.dev);
1188         mtu = cork->fragsize;
1189 
1190         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
1191         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
1192         maxnonfragsize = ip_sk_local_df(sk) ? 0xFFFF : mtu;
1193 
1194         if (cork->length + size > maxnonfragsize - fragheaderlen) {
1195                 ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
1196                                mtu - (opt ? opt->optlen : 0));
1197                 return -EMSGSIZE;
1198         }
1199 
1200         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
1201                 return -EINVAL;
1202 
1203         cork->length += size;
1204         if ((size + skb->len > mtu) &&
1205             (sk->sk_protocol == IPPROTO_UDP) &&
1206             (rt->dst.dev->features & NETIF_F_UFO)) {
1207                 skb_shinfo(skb)->gso_size = mtu - fragheaderlen;
1208                 skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
1209         }
1210 
1211 
1212         while (size > 0) {
1213                 int i;
1214 
1215                 if (skb_is_gso(skb))
1216                         len = size;
1217                 else {
1218 
1219                         /* Check if the remaining data fits into current packet. */
1220                         len = mtu - skb->len;
1221                         if (len < size)
1222                                 len = maxfraglen - skb->len;
1223                 }
1224                 if (len <= 0) {
1225                         struct sk_buff *skb_prev;
1226                         int alloclen;
1227 
1228                         skb_prev = skb;
1229                         fraggap = skb_prev->len - maxfraglen;
1230 
1231                         alloclen = fragheaderlen + hh_len + fraggap + 15;
1232                         skb = sock_wmalloc(sk, alloclen, 1, sk->sk_allocation);
1233                         if (unlikely(!skb)) {
1234                                 err = -ENOBUFS;
1235                                 goto error;
1236                         }
1237 
1238                         /*
1239                          *      Fill in the control structures
1240                          */
1241                         skb->ip_summed = CHECKSUM_NONE;
1242                         skb->csum = 0;
1243                         skb_reserve(skb, hh_len);
1244 
1245                         /*
1246                          *      Find where to start putting bytes.
1247                          */
1248                         skb_put(skb, fragheaderlen + fraggap);
1249                         skb_reset_network_header(skb);
1250                         skb->transport_header = (skb->network_header +
1251                                                  fragheaderlen);
1252                         if (fraggap) {
1253                                 skb->csum = skb_copy_and_csum_bits(skb_prev,
1254                                                                    maxfraglen,
1255                                                     skb_transport_header(skb),
1256                                                                    fraggap, 0);
1257                                 skb_prev->csum = csum_sub(skb_prev->csum,
1258                                                           skb->csum);
1259                                 pskb_trim_unique(skb_prev, maxfraglen);
1260                         }
1261 
1262                         /*
1263                          * Put the packet on the pending queue.
1264                          */
1265                         __skb_queue_tail(&sk->sk_write_queue, skb);
1266                         continue;
1267                 }
1268 
1269                 i = skb_shinfo(skb)->nr_frags;
1270                 if (len > size)
1271                         len = size;
1272                 if (skb_can_coalesce(skb, i, page, offset)) {
1273                         skb_frag_size_add(&skb_shinfo(skb)->frags[i-1], len);
1274                 } else if (i < MAX_SKB_FRAGS) {
1275                         get_page(page);
1276                         skb_fill_page_desc(skb, i, page, offset, len);
1277                 } else {
1278                         err = -EMSGSIZE;
1279                         goto error;
1280                 }
1281 
1282                 if (skb->ip_summed == CHECKSUM_NONE) {
1283                         __wsum csum;
1284                         csum = csum_page(page, offset, len);
1285                         skb->csum = csum_block_add(skb->csum, csum, skb->len);
1286                 }
1287 
1288                 skb->len += len;
1289                 skb->data_len += len;
1290                 skb->truesize += len;
1291                 atomic_add(len, &sk->sk_wmem_alloc);
1292                 offset += len;
1293                 size -= len;
1294         }
1295         return 0;
1296 
1297 error:
1298         cork->length -= size;
1299         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1300         return err;
1301 }
1302 
1303 static void ip_cork_release(struct inet_cork *cork)
1304 {
1305         cork->flags &= ~IPCORK_OPT;
1306         kfree(cork->opt);
1307         cork->opt = NULL;
1308         dst_release(cork->dst);
1309         cork->dst = NULL;
1310 }
1311 
1312 /*
1313  *      Combined all pending IP fragments on the socket as one IP datagram
1314  *      and push them out.
1315  */
1316 struct sk_buff *__ip_make_skb(struct sock *sk,
1317                               struct flowi4 *fl4,
1318                               struct sk_buff_head *queue,
1319                               struct inet_cork *cork)
1320 {
1321         struct sk_buff *skb, *tmp_skb;
1322         struct sk_buff **tail_skb;
1323         struct inet_sock *inet = inet_sk(sk);
1324         struct net *net = sock_net(sk);
1325         struct ip_options *opt = NULL;
1326         struct rtable *rt = (struct rtable *)cork->dst;
1327         struct iphdr *iph;
1328         __be16 df = 0;
1329         __u8 ttl;
1330 
1331         if ((skb = __skb_dequeue(queue)) == NULL)
1332                 goto out;
1333         tail_skb = &(skb_shinfo(skb)->frag_list);
1334 
1335         /* move skb->data to ip header from ext header */
1336         if (skb->data < skb_network_header(skb))
1337                 __skb_pull(skb, skb_network_offset(skb));
1338         while ((tmp_skb = __skb_dequeue(queue)) != NULL) {
1339                 __skb_pull(tmp_skb, skb_network_header_len(skb));
1340                 *tail_skb = tmp_skb;
1341                 tail_skb = &(tmp_skb->next);
1342                 skb->len += tmp_skb->len;
1343                 skb->data_len += tmp_skb->len;
1344                 skb->truesize += tmp_skb->truesize;
1345                 tmp_skb->destructor = NULL;
1346                 tmp_skb->sk = NULL;
1347         }
1348 
1349         /* Unless user demanded real pmtu discovery (IP_PMTUDISC_DO), we allow
1350          * to fragment the frame generated here. No matter, what transforms
1351          * how transforms change size of the packet, it will come out.
1352          */
1353         skb->local_df = ip_sk_local_df(sk);
1354 
1355         /* DF bit is set when we want to see DF on outgoing frames.
1356          * If local_df is set too, we still allow to fragment this frame
1357          * locally. */
1358         if (inet->pmtudisc == IP_PMTUDISC_DO ||
1359             inet->pmtudisc == IP_PMTUDISC_PROBE ||
1360             (skb->len <= dst_mtu(&rt->dst) &&
1361              ip_dont_fragment(sk, &rt->dst)))
1362                 df = htons(IP_DF);
1363 
1364         if (cork->flags & IPCORK_OPT)
1365                 opt = cork->opt;
1366 
1367         if (cork->ttl != 0)
1368                 ttl = cork->ttl;
1369         else if (rt->rt_type == RTN_MULTICAST)
1370                 ttl = inet->mc_ttl;
1371         else
1372                 ttl = ip_select_ttl(inet, &rt->dst);
1373 
1374         iph = ip_hdr(skb);
1375         iph->version = 4;
1376         iph->ihl = 5;
1377         iph->tos = (cork->tos != -1) ? cork->tos : inet->tos;
1378         iph->frag_off = df;
1379         iph->ttl = ttl;
1380         iph->protocol = sk->sk_protocol;
1381         ip_copy_addrs(iph, fl4);
1382         ip_select_ident(skb, &rt->dst, sk);
1383 
1384         if (opt) {
1385                 iph->ihl += opt->optlen>>2;
1386                 ip_options_build(skb, opt, cork->addr, rt, 0);
1387         }
1388 
1389         skb->priority = (cork->tos != -1) ? cork->priority: sk->sk_priority;
1390         skb->mark = sk->sk_mark;
1391         /*
1392          * Steal rt from cork.dst to avoid a pair of atomic_inc/atomic_dec
1393          * on dst refcount
1394          */
1395         cork->dst = NULL;
1396         skb_dst_set(skb, &rt->dst);
1397 
1398         if (iph->protocol == IPPROTO_ICMP)
1399                 icmp_out_count(net, ((struct icmphdr *)
1400                         skb_transport_header(skb))->type);
1401 
1402         ip_cork_release(cork);
1403 out:
1404         return skb;
1405 }
1406 
1407 int ip_send_skb(struct net *net, struct sk_buff *skb)
1408 {
1409         int err;
1410 
1411         err = ip_local_out(skb);
1412         if (err) {
1413                 if (err > 0)
1414                         err = net_xmit_errno(err);
1415                 if (err)
1416                         IP_INC_STATS(net, IPSTATS_MIB_OUTDISCARDS);
1417         }
1418 
1419         return err;
1420 }
1421 
1422 int ip_push_pending_frames(struct sock *sk, struct flowi4 *fl4)
1423 {
1424         struct sk_buff *skb;
1425 
1426         skb = ip_finish_skb(sk, fl4);
1427         if (!skb)
1428                 return 0;
1429 
1430         /* Netfilter gets whole the not fragmented skb. */
1431         return ip_send_skb(sock_net(sk), skb);
1432 }
1433 
1434 /*
1435  *      Throw away all pending data on the socket.
1436  */
1437 static void __ip_flush_pending_frames(struct sock *sk,
1438                                       struct sk_buff_head *queue,
1439                                       struct inet_cork *cork)
1440 {
1441         struct sk_buff *skb;
1442 
1443         while ((skb = __skb_dequeue_tail(queue)) != NULL)
1444                 kfree_skb(skb);
1445 
1446         ip_cork_release(cork);
1447 }
1448 
1449 void ip_flush_pending_frames(struct sock *sk)
1450 {
1451         __ip_flush_pending_frames(sk, &sk->sk_write_queue, &inet_sk(sk)->cork.base);
1452 }
1453 
1454 struct sk_buff *ip_make_skb(struct sock *sk,
1455                             struct flowi4 *fl4,
1456                             int getfrag(void *from, char *to, int offset,
1457                                         int len, int odd, struct sk_buff *skb),
1458                             void *from, int length, int transhdrlen,
1459                             struct ipcm_cookie *ipc, struct rtable **rtp,
1460                             unsigned int flags)
1461 {
1462         struct inet_cork cork;
1463         struct sk_buff_head queue;
1464         int err;
1465 
1466         if (flags & MSG_PROBE)
1467                 return NULL;
1468 
1469         __skb_queue_head_init(&queue);
1470 
1471         cork.flags = 0;
1472         cork.addr = 0;
1473         cork.opt = NULL;
1474         err = ip_setup_cork(sk, &cork, ipc, rtp);
1475         if (err)
1476                 return ERR_PTR(err);
1477 
1478         err = __ip_append_data(sk, fl4, &queue, &cork,
1479                                &current->task_frag, getfrag,
1480                                from, length, transhdrlen, flags);
1481         if (err) {
1482                 __ip_flush_pending_frames(sk, &queue, &cork);
1483                 return ERR_PTR(err);
1484         }
1485 
1486         return __ip_make_skb(sk, fl4, &queue, &cork);
1487 }
1488 
1489 /*
1490  *      Fetch data from kernel space and fill in checksum if needed.
1491  */
1492 static int ip_reply_glue_bits(void *dptr, char *to, int offset,
1493                               int len, int odd, struct sk_buff *skb)
1494 {
1495         __wsum csum;
1496 
1497         csum = csum_partial_copy_nocheck(dptr+offset, to, len, 0);
1498         skb->csum = csum_block_add(skb->csum, csum, odd);
1499         return 0;
1500 }
1501 
1502 /*
1503  *      Generic function to send a packet as reply to another packet.
1504  *      Used to send some TCP resets/acks so far.
1505  *
1506  *      Use a fake percpu inet socket to avoid false sharing and contention.
1507  */
1508 static DEFINE_PER_CPU(struct inet_sock, unicast_sock) = {
1509         .sk = {
1510                 .__sk_common = {
1511                         .skc_refcnt = ATOMIC_INIT(1),
1512                 },
1513                 .sk_wmem_alloc  = ATOMIC_INIT(1),
1514                 .sk_allocation  = GFP_ATOMIC,
1515                 .sk_flags       = (1UL << SOCK_USE_WRITE_QUEUE),
1516         },
1517         .pmtudisc       = IP_PMTUDISC_WANT,
1518         .uc_ttl         = -1,
1519 };
1520 
1521 void ip_send_unicast_reply(struct net *net, struct sk_buff *skb, __be32 daddr,
1522                            __be32 saddr, const struct ip_reply_arg *arg,
1523                            unsigned int len)
1524 {
1525         struct ip_options_data replyopts;
1526         struct ipcm_cookie ipc;
1527         struct flowi4 fl4;
1528         struct rtable *rt = skb_rtable(skb);
1529         struct sk_buff *nskb;
1530         struct sock *sk;
1531         struct inet_sock *inet;
1532 
1533         if (ip_options_echo(&replyopts.opt.opt, skb))
1534                 return;
1535 
1536         ipc.addr = daddr;
1537         ipc.opt = NULL;
1538         ipc.tx_flags = 0;
1539         ipc.ttl = 0;
1540         ipc.tos = -1;
1541 
1542         if (replyopts.opt.opt.optlen) {
1543                 ipc.opt = &replyopts.opt;
1544 
1545                 if (replyopts.opt.opt.srr)
1546                         daddr = replyopts.opt.opt.faddr;
1547         }
1548 
1549         flowi4_init_output(&fl4, arg->bound_dev_if, 0,
1550                            RT_TOS(arg->tos),
1551                            RT_SCOPE_UNIVERSE, ip_hdr(skb)->protocol,
1552                            ip_reply_arg_flowi_flags(arg),
1553                            daddr, saddr,
1554                            tcp_hdr(skb)->source, tcp_hdr(skb)->dest);
1555         security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
1556         rt = ip_route_output_key(net, &fl4);
1557         if (IS_ERR(rt))
1558                 return;
1559 
1560         inet = &get_cpu_var(unicast_sock);
1561 
1562         inet->tos = arg->tos;
1563         sk = &inet->sk;
1564         sk->sk_priority = skb->priority;
1565         sk->sk_protocol = ip_hdr(skb)->protocol;
1566         sk->sk_bound_dev_if = arg->bound_dev_if;
1567         sock_net_set(sk, net);
1568         __skb_queue_head_init(&sk->sk_write_queue);
1569         sk->sk_sndbuf = sysctl_wmem_default;
1570         ip_append_data(sk, &fl4, ip_reply_glue_bits, arg->iov->iov_base, len, 0,
1571                        &ipc, &rt, MSG_DONTWAIT);
1572         nskb = skb_peek(&sk->sk_write_queue);
1573         if (nskb) {
1574                 if (arg->csumoffset >= 0)
1575                         *((__sum16 *)skb_transport_header(nskb) +
1576                           arg->csumoffset) = csum_fold(csum_add(nskb->csum,
1577                                                                 arg->csum));
1578                 nskb->ip_summed = CHECKSUM_NONE;
1579                 skb_orphan(nskb);
1580                 skb_set_queue_mapping(nskb, skb_get_queue_mapping(skb));
1581                 ip_push_pending_frames(sk, &fl4);
1582         }
1583 
1584         put_cpu_var(unicast_sock);
1585 
1586         ip_rt_put(rt);
1587 }
1588 
1589 void __init ip_init(void)
1590 {
1591         ip_rt_init();
1592         inet_initpeers();
1593 
1594 #if defined(CONFIG_IP_MULTICAST)
1595         igmp_mc_init();
1596 #endif
1597 }
1598 

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