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

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