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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(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 defined(CONFIG_IP_VS) || defined(CONFIG_IP_VS_MODULE)
426         to->ipvs_property = from->ipvs_property;
427 #endif
428         skb_copy_secmark(to, from);
429 }
430 
431 /*
432  *      This IP datagram is too large to be sent in one piece.  Break it up into
433  *      smaller pieces (each of size equal to IP header plus
434  *      a block of the data of the original IP data part) that will yet fit in a
435  *      single device frame, and queue such a frame for sending.
436  */
437 
438 int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
439 {
440         struct iphdr *iph;
441         int ptr;
442         struct net_device *dev;
443         struct sk_buff *skb2;
444         unsigned int mtu, hlen, left, len, ll_rs;
445         int offset;
446         __be16 not_last_frag;
447         struct rtable *rt = skb_rtable(skb);
448         int err = 0;
449         bool forwarding = IPCB(skb)->flags & IPSKB_FORWARDED;
450 
451         dev = rt->dst.dev;
452 
453         /*
454          *      Point into the IP datagram header.
455          */
456 
457         iph = ip_hdr(skb);
458 
459         mtu = ip_dst_mtu_maybe_forward(&rt->dst, forwarding);
460         if (unlikely(((iph->frag_off & htons(IP_DF)) && !skb->local_df) ||
461                      (IPCB(skb)->frag_max_size &&
462                       IPCB(skb)->frag_max_size > mtu))) {
463                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
464                 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
465                           htonl(mtu));
466                 kfree_skb(skb);
467                 return -EMSGSIZE;
468         }
469 
470         /*
471          *      Setup starting values.
472          */
473 
474         hlen = iph->ihl * 4;
475         mtu = mtu - hlen;       /* Size of data space */
476 #ifdef CONFIG_BRIDGE_NETFILTER
477         if (skb->nf_bridge)
478                 mtu -= nf_bridge_mtu_reduction(skb);
479 #endif
480         IPCB(skb)->flags |= IPSKB_FRAG_COMPLETE;
481 
482         /* When frag_list is given, use it. First, check its validity:
483          * some transformers could create wrong frag_list or break existing
484          * one, it is not prohibited. In this case fall back to copying.
485          *
486          * LATER: this step can be merged to real generation of fragments,
487          * we can switch to copy when see the first bad fragment.
488          */
489         if (skb_has_frag_list(skb)) {
490                 struct sk_buff *frag, *frag2;
491                 int first_len = skb_pagelen(skb);
492 
493                 if (first_len - hlen > mtu ||
494                     ((first_len - hlen) & 7) ||
495                     ip_is_fragment(iph) ||
496                     skb_cloned(skb))
497                         goto slow_path;
498 
499                 skb_walk_frags(skb, frag) {
500                         /* Correct geometry. */
501                         if (frag->len > mtu ||
502                             ((frag->len & 7) && frag->next) ||
503                             skb_headroom(frag) < hlen)
504                                 goto slow_path_clean;
505 
506                         /* Partially cloned skb? */
507                         if (skb_shared(frag))
508                                 goto slow_path_clean;
509 
510                         BUG_ON(frag->sk);
511                         if (skb->sk) {
512                                 frag->sk = skb->sk;
513                                 frag->destructor = sock_wfree;
514                         }
515                         skb->truesize -= frag->truesize;
516                 }
517 
518                 /* Everything is OK. Generate! */
519 
520                 err = 0;
521                 offset = 0;
522                 frag = skb_shinfo(skb)->frag_list;
523                 skb_frag_list_init(skb);
524                 skb->data_len = first_len - skb_headlen(skb);
525                 skb->len = first_len;
526                 iph->tot_len = htons(first_len);
527                 iph->frag_off = htons(IP_MF);
528                 ip_send_check(iph);
529 
530                 for (;;) {
531                         /* Prepare header of the next frame,
532                          * before previous one went down. */
533                         if (frag) {
534                                 frag->ip_summed = CHECKSUM_NONE;
535                                 skb_reset_transport_header(frag);
536                                 __skb_push(frag, hlen);
537                                 skb_reset_network_header(frag);
538                                 memcpy(skb_network_header(frag), iph, hlen);
539                                 iph = ip_hdr(frag);
540                                 iph->tot_len = htons(frag->len);
541                                 ip_copy_metadata(frag, skb);
542                                 if (offset == 0)
543                                         ip_options_fragment(frag);
544                                 offset += skb->len - hlen;
545                                 iph->frag_off = htons(offset>>3);
546                                 if (frag->next != NULL)
547                                         iph->frag_off |= htons(IP_MF);
548                                 /* Ready, complete checksum */
549                                 ip_send_check(iph);
550                         }
551 
552                         err = output(skb);
553 
554                         if (!err)
555                                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGCREATES);
556                         if (err || !frag)
557                                 break;
558 
559                         skb = frag;
560                         frag = skb->next;
561                         skb->next = NULL;
562                 }
563 
564                 if (err == 0) {
565                         IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGOKS);
566                         return 0;
567                 }
568 
569                 while (frag) {
570                         skb = frag->next;
571                         kfree_skb(frag);
572                         frag = skb;
573                 }
574                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
575                 return err;
576 
577 slow_path_clean:
578                 skb_walk_frags(skb, frag2) {
579                         if (frag2 == frag)
580                                 break;
581                         frag2->sk = NULL;
582                         frag2->destructor = NULL;
583                         skb->truesize += frag2->truesize;
584                 }
585         }
586 
587 slow_path:
588         /* for offloaded checksums cleanup checksum before fragmentation */
589         if ((skb->ip_summed == CHECKSUM_PARTIAL) && skb_checksum_help(skb))
590                 goto fail;
591         iph = ip_hdr(skb);
592 
593         left = skb->len - hlen;         /* Space per frame */
594         ptr = hlen;             /* Where to start from */
595 
596         /* for bridged IP traffic encapsulated inside f.e. a vlan header,
597          * we need to make room for the encapsulating header
598          */
599         ll_rs = LL_RESERVED_SPACE_EXTRA(rt->dst.dev, nf_bridge_pad(skb));
600 
601         /*
602          *      Fragment the datagram.
603          */
604 
605         offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3;
606         not_last_frag = iph->frag_off & htons(IP_MF);
607 
608         /*
609          *      Keep copying data until we run out.
610          */
611 
612         while (left > 0) {
613                 len = left;
614                 /* IF: it doesn't fit, use 'mtu' - the data space left */
615                 if (len > mtu)
616                         len = mtu;
617                 /* IF: we are not sending up to and including the packet end
618                    then align the next start on an eight byte boundary */
619                 if (len < left) {
620                         len &= ~7;
621                 }
622                 /*
623                  *      Allocate buffer.
624                  */
625 
626                 if ((skb2 = alloc_skb(len+hlen+ll_rs, GFP_ATOMIC)) == NULL) {
627                         NETDEBUG(KERN_INFO "IP: frag: no memory for new fragment!\n");
628                         err = -ENOMEM;
629                         goto fail;
630                 }
631 
632                 /*
633                  *      Set up data on packet
634                  */
635 
636                 ip_copy_metadata(skb2, skb);
637                 skb_reserve(skb2, ll_rs);
638                 skb_put(skb2, len + hlen);
639                 skb_reset_network_header(skb2);
640                 skb2->transport_header = skb2->network_header + hlen;
641 
642                 /*
643                  *      Charge the memory for the fragment to any owner
644                  *      it might possess
645                  */
646 
647                 if (skb->sk)
648                         skb_set_owner_w(skb2, skb->sk);
649 
650                 /*
651                  *      Copy the packet header into the new buffer.
652                  */
653 
654                 skb_copy_from_linear_data(skb, skb_network_header(skb2), hlen);
655 
656                 /*
657                  *      Copy a block of the IP datagram.
658                  */
659                 if (skb_copy_bits(skb, ptr, skb_transport_header(skb2), len))
660                         BUG();
661                 left -= len;
662 
663                 /*
664                  *      Fill in the new header fields.
665                  */
666                 iph = ip_hdr(skb2);
667                 iph->frag_off = htons((offset >> 3));
668 
669                 /* ANK: dirty, but effective trick. Upgrade options only if
670                  * the segment to be fragmented was THE FIRST (otherwise,
671                  * options are already fixed) and make it ONCE
672                  * on the initial skb, so that all the following fragments
673                  * will inherit fixed options.
674                  */
675                 if (offset == 0)
676                         ip_options_fragment(skb);
677 
678                 /*
679                  *      Added AC : If we are fragmenting a fragment that's not the
680                  *                 last fragment then keep MF on each bit
681                  */
682                 if (left > 0 || not_last_frag)
683                         iph->frag_off |= htons(IP_MF);
684                 ptr += len;
685                 offset += len;
686 
687                 /*
688                  *      Put this fragment into the sending queue.
689                  */
690                 iph->tot_len = htons(len + hlen);
691 
692                 ip_send_check(iph);
693 
694                 err = output(skb2);
695                 if (err)
696                         goto fail;
697 
698                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGCREATES);
699         }
700         consume_skb(skb);
701         IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGOKS);
702         return err;
703 
704 fail:
705         kfree_skb(skb);
706         IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
707         return err;
708 }
709 EXPORT_SYMBOL(ip_fragment);
710 
711 int
712 ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
713 {
714         struct iovec *iov = from;
715 
716         if (skb->ip_summed == CHECKSUM_PARTIAL) {
717                 if (memcpy_fromiovecend(to, iov, offset, len) < 0)
718                         return -EFAULT;
719         } else {
720                 __wsum csum = 0;
721                 if (csum_partial_copy_fromiovecend(to, iov, offset, len, &csum) < 0)
722                         return -EFAULT;
723                 skb->csum = csum_block_add(skb->csum, csum, odd);
724         }
725         return 0;
726 }
727 EXPORT_SYMBOL(ip_generic_getfrag);
728 
729 static inline __wsum
730 csum_page(struct page *page, int offset, int copy)
731 {
732         char *kaddr;
733         __wsum csum;
734         kaddr = kmap(page);
735         csum = csum_partial(kaddr + offset, copy, 0);
736         kunmap(page);
737         return csum;
738 }
739 
740 static inline int ip_ufo_append_data(struct sock *sk,
741                         struct sk_buff_head *queue,
742                         int getfrag(void *from, char *to, int offset, int len,
743                                int odd, struct sk_buff *skb),
744                         void *from, int length, int hh_len, int fragheaderlen,
745                         int transhdrlen, int maxfraglen, unsigned int flags)
746 {
747         struct sk_buff *skb;
748         int err;
749 
750         /* There is support for UDP fragmentation offload by network
751          * device, so create one single skb packet containing complete
752          * udp datagram
753          */
754         if ((skb = skb_peek_tail(queue)) == NULL) {
755                 skb = sock_alloc_send_skb(sk,
756                         hh_len + fragheaderlen + transhdrlen + 20,
757                         (flags & MSG_DONTWAIT), &err);
758 
759                 if (skb == NULL)
760                         return err;
761 
762                 /* reserve space for Hardware header */
763                 skb_reserve(skb, hh_len);
764 
765                 /* create space for UDP/IP header */
766                 skb_put(skb, fragheaderlen + transhdrlen);
767 
768                 /* initialize network header pointer */
769                 skb_reset_network_header(skb);
770 
771                 /* initialize protocol header pointer */
772                 skb->transport_header = skb->network_header + fragheaderlen;
773 
774                 skb->csum = 0;
775 
776 
777                 __skb_queue_tail(queue, skb);
778         } else if (skb_is_gso(skb)) {
779                 goto append;
780         }
781 
782         skb->ip_summed = CHECKSUM_PARTIAL;
783         /* specify the length of each IP datagram fragment */
784         skb_shinfo(skb)->gso_size = maxfraglen - fragheaderlen;
785         skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
786 
787 append:
788         return skb_append_datato_frags(sk, skb, getfrag, from,
789                                        (length - transhdrlen));
790 }
791 
792 static int __ip_append_data(struct sock *sk,
793                             struct flowi4 *fl4,
794                             struct sk_buff_head *queue,
795                             struct inet_cork *cork,
796                             struct page_frag *pfrag,
797                             int getfrag(void *from, char *to, int offset,
798                                         int len, int odd, struct sk_buff *skb),
799                             void *from, int length, int transhdrlen,
800                             unsigned int flags)
801 {
802         struct inet_sock *inet = inet_sk(sk);
803         struct sk_buff *skb;
804 
805         struct ip_options *opt = cork->opt;
806         int hh_len;
807         int exthdrlen;
808         int mtu;
809         int copy;
810         int err;
811         int offset = 0;
812         unsigned int maxfraglen, fragheaderlen, maxnonfragsize;
813         int csummode = CHECKSUM_NONE;
814         struct rtable *rt = (struct rtable *)cork->dst;
815 
816         skb = skb_peek_tail(queue);
817 
818         exthdrlen = !skb ? rt->dst.header_len : 0;
819         mtu = cork->fragsize;
820 
821         hh_len = LL_RESERVED_SPACE(rt->dst.dev);
822 
823         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
824         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
825         maxnonfragsize = (inet->pmtudisc >= IP_PMTUDISC_DO) ?
826                          mtu : 0xFFFF;
827 
828         if (cork->length + length > maxnonfragsize - fragheaderlen) {
829                 ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
830                                mtu - (opt ? opt->optlen : 0));
831                 return -EMSGSIZE;
832         }
833 
834         /*
835          * transhdrlen > 0 means that this is the first fragment and we wish
836          * it won't be fragmented in the future.
837          */
838         if (transhdrlen &&
839             length + fragheaderlen <= mtu &&
840             rt->dst.dev->features & NETIF_F_V4_CSUM &&
841             !exthdrlen)
842                 csummode = CHECKSUM_PARTIAL;
843 
844         cork->length += length;
845         if (((length > mtu) || (skb && skb_is_gso(skb))) &&
846             (sk->sk_protocol == IPPROTO_UDP) &&
847             (rt->dst.dev->features & NETIF_F_UFO) && !rt->dst.header_len) {
848                 err = ip_ufo_append_data(sk, queue, getfrag, from, length,
849                                          hh_len, fragheaderlen, transhdrlen,
850                                          maxfraglen, flags);
851                 if (err)
852                         goto error;
853                 return 0;
854         }
855 
856         /* So, what's going on in the loop below?
857          *
858          * We use calculated fragment length to generate chained skb,
859          * each of segments is IP fragment ready for sending to network after
860          * adding appropriate IP header.
861          */
862 
863         if (!skb)
864                 goto alloc_new_skb;
865 
866         while (length > 0) {
867                 /* Check if the remaining data fits into current packet. */
868                 copy = mtu - skb->len;
869                 if (copy < length)
870                         copy = maxfraglen - skb->len;
871                 if (copy <= 0) {
872                         char *data;
873                         unsigned int datalen;
874                         unsigned int fraglen;
875                         unsigned int fraggap;
876                         unsigned int alloclen;
877                         struct sk_buff *skb_prev;
878 alloc_new_skb:
879                         skb_prev = skb;
880                         if (skb_prev)
881                                 fraggap = skb_prev->len - maxfraglen;
882                         else
883                                 fraggap = 0;
884 
885                         /*
886                          * If remaining data exceeds the mtu,
887                          * we know we need more fragment(s).
888                          */
889                         datalen = length + fraggap;
890                         if (datalen > mtu - fragheaderlen)
891                                 datalen = maxfraglen - fragheaderlen;
892                         fraglen = datalen + fragheaderlen;
893 
894                         if ((flags & MSG_MORE) &&
895                             !(rt->dst.dev->features&NETIF_F_SG))
896                                 alloclen = mtu;
897                         else
898                                 alloclen = fraglen;
899 
900                         alloclen += exthdrlen;
901 
902                         /* The last fragment gets additional space at tail.
903                          * Note, with MSG_MORE we overallocate on fragments,
904                          * because we have no idea what fragment will be
905                          * the last.
906                          */
907                         if (datalen == length + fraggap)
908                                 alloclen += rt->dst.trailer_len;
909 
910                         if (transhdrlen) {
911                                 skb = sock_alloc_send_skb(sk,
912                                                 alloclen + hh_len + 15,
913                                                 (flags & MSG_DONTWAIT), &err);
914                         } else {
915                                 skb = NULL;
916                                 if (atomic_read(&sk->sk_wmem_alloc) <=
917                                     2 * sk->sk_sndbuf)
918                                         skb = sock_wmalloc(sk,
919                                                            alloclen + hh_len + 15, 1,
920                                                            sk->sk_allocation);
921                                 if (unlikely(skb == NULL))
922                                         err = -ENOBUFS;
923                                 else
924                                         /* only the initial fragment is
925                                            time stamped */
926                                         cork->tx_flags = 0;
927                         }
928                         if (skb == NULL)
929                                 goto error;
930 
931                         /*
932                          *      Fill in the control structures
933                          */
934                         skb->ip_summed = csummode;
935                         skb->csum = 0;
936                         skb_reserve(skb, hh_len);
937                         skb_shinfo(skb)->tx_flags = cork->tx_flags;
938 
939                         /*
940                          *      Find where to start putting bytes.
941                          */
942                         data = skb_put(skb, fraglen + exthdrlen);
943                         skb_set_network_header(skb, exthdrlen);
944                         skb->transport_header = (skb->network_header +
945                                                  fragheaderlen);
946                         data += fragheaderlen + exthdrlen;
947 
948                         if (fraggap) {
949                                 skb->csum = skb_copy_and_csum_bits(
950                                         skb_prev, maxfraglen,
951                                         data + transhdrlen, fraggap, 0);
952                                 skb_prev->csum = csum_sub(skb_prev->csum,
953                                                           skb->csum);
954                                 data += fraggap;
955                                 pskb_trim_unique(skb_prev, maxfraglen);
956                         }
957 
958                         copy = datalen - transhdrlen - fraggap;
959                         if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
960                                 err = -EFAULT;
961                                 kfree_skb(skb);
962                                 goto error;
963                         }
964 
965                         offset += copy;
966                         length -= datalen - fraggap;
967                         transhdrlen = 0;
968                         exthdrlen = 0;
969                         csummode = CHECKSUM_NONE;
970 
971                         /*
972                          * Put the packet on the pending queue.
973                          */
974                         __skb_queue_tail(queue, skb);
975                         continue;
976                 }
977 
978                 if (copy > length)
979                         copy = length;
980 
981                 if (!(rt->dst.dev->features&NETIF_F_SG)) {
982                         unsigned int off;
983 
984                         off = skb->len;
985                         if (getfrag(from, skb_put(skb, copy),
986                                         offset, copy, off, skb) < 0) {
987                                 __skb_trim(skb, off);
988                                 err = -EFAULT;
989                                 goto error;
990                         }
991                 } else {
992                         int i = skb_shinfo(skb)->nr_frags;
993 
994                         err = -ENOMEM;
995                         if (!sk_page_frag_refill(sk, pfrag))
996                                 goto error;
997 
998                         if (!skb_can_coalesce(skb, i, pfrag->page,
999                                               pfrag->offset)) {
1000                                 err = -EMSGSIZE;
1001                                 if (i == MAX_SKB_FRAGS)
1002                                         goto error;
1003 
1004                                 __skb_fill_page_desc(skb, i, pfrag->page,
1005                                                      pfrag->offset, 0);
1006                                 skb_shinfo(skb)->nr_frags = ++i;
1007                                 get_page(pfrag->page);
1008                         }
1009                         copy = min_t(int, copy, pfrag->size - pfrag->offset);
1010                         if (getfrag(from,
1011                                     page_address(pfrag->page) + pfrag->offset,
1012                                     offset, copy, skb->len, skb) < 0)
1013                                 goto error_efault;
1014 
1015                         pfrag->offset += copy;
1016                         skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
1017                         skb->len += copy;
1018                         skb->data_len += copy;
1019                         skb->truesize += copy;
1020                         atomic_add(copy, &sk->sk_wmem_alloc);
1021                 }
1022                 offset += copy;
1023                 length -= copy;
1024         }
1025 
1026         return 0;
1027 
1028 error_efault:
1029         err = -EFAULT;
1030 error:
1031         cork->length -= length;
1032         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1033         return err;
1034 }
1035 
1036 static int ip_setup_cork(struct sock *sk, struct inet_cork *cork,
1037                          struct ipcm_cookie *ipc, struct rtable **rtp)
1038 {
1039         struct ip_options_rcu *opt;
1040         struct rtable *rt;
1041 
1042         /*
1043          * setup for corking.
1044          */
1045         opt = ipc->opt;
1046         if (opt) {
1047                 if (cork->opt == NULL) {
1048                         cork->opt = kmalloc(sizeof(struct ip_options) + 40,
1049                                             sk->sk_allocation);
1050                         if (unlikely(cork->opt == NULL))
1051                                 return -ENOBUFS;
1052                 }
1053                 memcpy(cork->opt, &opt->opt, sizeof(struct ip_options) + opt->opt.optlen);
1054                 cork->flags |= IPCORK_OPT;
1055                 cork->addr = ipc->addr;
1056         }
1057         rt = *rtp;
1058         if (unlikely(!rt))
1059                 return -EFAULT;
1060         /*
1061          * We steal reference to this route, caller should not release it
1062          */
1063         *rtp = NULL;
1064         cork->fragsize = ip_sk_use_pmtu(sk) ?
1065                          dst_mtu(&rt->dst) : rt->dst.dev->mtu;
1066         cork->dst = &rt->dst;
1067         cork->length = 0;
1068         cork->ttl = ipc->ttl;
1069         cork->tos = ipc->tos;
1070         cork->priority = ipc->priority;
1071         cork->tx_flags = ipc->tx_flags;
1072 
1073         return 0;
1074 }
1075 
1076 /*
1077  *      ip_append_data() and ip_append_page() can make one large IP datagram
1078  *      from many pieces of data. Each pieces will be holded on the socket
1079  *      until ip_push_pending_frames() is called. Each piece can be a page
1080  *      or non-page data.
1081  *
1082  *      Not only UDP, other transport protocols - e.g. raw sockets - can use
1083  *      this interface potentially.
1084  *
1085  *      LATER: length must be adjusted by pad at tail, when it is required.
1086  */
1087 int ip_append_data(struct sock *sk, struct flowi4 *fl4,
1088                    int getfrag(void *from, char *to, int offset, int len,
1089                                int odd, struct sk_buff *skb),
1090                    void *from, int length, int transhdrlen,
1091                    struct ipcm_cookie *ipc, struct rtable **rtp,
1092                    unsigned int flags)
1093 {
1094         struct inet_sock *inet = inet_sk(sk);
1095         int err;
1096 
1097         if (flags&MSG_PROBE)
1098                 return 0;
1099 
1100         if (skb_queue_empty(&sk->sk_write_queue)) {
1101                 err = ip_setup_cork(sk, &inet->cork.base, ipc, rtp);
1102                 if (err)
1103                         return err;
1104         } else {
1105                 transhdrlen = 0;
1106         }
1107 
1108         return __ip_append_data(sk, fl4, &sk->sk_write_queue, &inet->cork.base,
1109                                 sk_page_frag(sk), getfrag,
1110                                 from, length, transhdrlen, flags);
1111 }
1112 
1113 ssize_t ip_append_page(struct sock *sk, struct flowi4 *fl4, struct page *page,
1114                        int offset, size_t size, int flags)
1115 {
1116         struct inet_sock *inet = inet_sk(sk);
1117         struct sk_buff *skb;
1118         struct rtable *rt;
1119         struct ip_options *opt = NULL;
1120         struct inet_cork *cork;
1121         int hh_len;
1122         int mtu;
1123         int len;
1124         int err;
1125         unsigned int maxfraglen, fragheaderlen, fraggap, maxnonfragsize;
1126 
1127         if (inet->hdrincl)
1128                 return -EPERM;
1129 
1130         if (flags&MSG_PROBE)
1131                 return 0;
1132 
1133         if (skb_queue_empty(&sk->sk_write_queue))
1134                 return -EINVAL;
1135 
1136         cork = &inet->cork.base;
1137         rt = (struct rtable *)cork->dst;
1138         if (cork->flags & IPCORK_OPT)
1139                 opt = cork->opt;
1140 
1141         if (!(rt->dst.dev->features&NETIF_F_SG))
1142                 return -EOPNOTSUPP;
1143 
1144         hh_len = LL_RESERVED_SPACE(rt->dst.dev);
1145         mtu = cork->fragsize;
1146 
1147         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
1148         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
1149         maxnonfragsize = (inet->pmtudisc >= IP_PMTUDISC_DO) ?
1150                          mtu : 0xFFFF;
1151 
1152         if (cork->length + size > maxnonfragsize - fragheaderlen) {
1153                 ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
1154                                mtu - (opt ? opt->optlen : 0));
1155                 return -EMSGSIZE;
1156         }
1157 
1158         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
1159                 return -EINVAL;
1160 
1161         cork->length += size;
1162         if ((size + skb->len > mtu) &&
1163             (sk->sk_protocol == IPPROTO_UDP) &&
1164             (rt->dst.dev->features & NETIF_F_UFO)) {
1165                 skb_shinfo(skb)->gso_size = mtu - fragheaderlen;
1166                 skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
1167         }
1168 
1169 
1170         while (size > 0) {
1171                 int i;
1172 
1173                 if (skb_is_gso(skb))
1174                         len = size;
1175                 else {
1176 
1177                         /* Check if the remaining data fits into current packet. */
1178                         len = mtu - skb->len;
1179                         if (len < size)
1180                                 len = maxfraglen - skb->len;
1181                 }
1182                 if (len <= 0) {
1183                         struct sk_buff *skb_prev;
1184                         int alloclen;
1185 
1186                         skb_prev = skb;
1187                         fraggap = skb_prev->len - maxfraglen;
1188 
1189                         alloclen = fragheaderlen + hh_len + fraggap + 15;
1190                         skb = sock_wmalloc(sk, alloclen, 1, sk->sk_allocation);
1191                         if (unlikely(!skb)) {
1192                                 err = -ENOBUFS;
1193                                 goto error;
1194                         }
1195 
1196                         /*
1197                          *      Fill in the control structures
1198                          */
1199                         skb->ip_summed = CHECKSUM_NONE;
1200                         skb->csum = 0;
1201                         skb_reserve(skb, hh_len);
1202 
1203                         /*
1204                          *      Find where to start putting bytes.
1205                          */
1206                         skb_put(skb, fragheaderlen + fraggap);
1207                         skb_reset_network_header(skb);
1208                         skb->transport_header = (skb->network_header +
1209                                                  fragheaderlen);
1210                         if (fraggap) {
1211                                 skb->csum = skb_copy_and_csum_bits(skb_prev,
1212                                                                    maxfraglen,
1213                                                     skb_transport_header(skb),
1214                                                                    fraggap, 0);
1215                                 skb_prev->csum = csum_sub(skb_prev->csum,
1216                                                           skb->csum);
1217                                 pskb_trim_unique(skb_prev, maxfraglen);
1218                         }
1219 
1220                         /*
1221                          * Put the packet on the pending queue.
1222                          */
1223                         __skb_queue_tail(&sk->sk_write_queue, skb);
1224                         continue;
1225                 }
1226 
1227                 i = skb_shinfo(skb)->nr_frags;
1228                 if (len > size)
1229                         len = size;
1230                 if (skb_can_coalesce(skb, i, page, offset)) {
1231                         skb_frag_size_add(&skb_shinfo(skb)->frags[i-1], len);
1232                 } else if (i < MAX_SKB_FRAGS) {
1233                         get_page(page);
1234                         skb_fill_page_desc(skb, i, page, offset, len);
1235                 } else {
1236                         err = -EMSGSIZE;
1237                         goto error;
1238                 }
1239 
1240                 if (skb->ip_summed == CHECKSUM_NONE) {
1241                         __wsum csum;
1242                         csum = csum_page(page, offset, len);
1243                         skb->csum = csum_block_add(skb->csum, csum, skb->len);
1244                 }
1245 
1246                 skb->len += len;
1247                 skb->data_len += len;
1248                 skb->truesize += len;
1249                 atomic_add(len, &sk->sk_wmem_alloc);
1250                 offset += len;
1251                 size -= len;
1252         }
1253         return 0;
1254 
1255 error:
1256         cork->length -= size;
1257         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1258         return err;
1259 }
1260 
1261 static void ip_cork_release(struct inet_cork *cork)
1262 {
1263         cork->flags &= ~IPCORK_OPT;
1264         kfree(cork->opt);
1265         cork->opt = NULL;
1266         dst_release(cork->dst);
1267         cork->dst = NULL;
1268 }
1269 
1270 /*
1271  *      Combined all pending IP fragments on the socket as one IP datagram
1272  *      and push them out.
1273  */
1274 struct sk_buff *__ip_make_skb(struct sock *sk,
1275                               struct flowi4 *fl4,
1276                               struct sk_buff_head *queue,
1277                               struct inet_cork *cork)
1278 {
1279         struct sk_buff *skb, *tmp_skb;
1280         struct sk_buff **tail_skb;
1281         struct inet_sock *inet = inet_sk(sk);
1282         struct net *net = sock_net(sk);
1283         struct ip_options *opt = NULL;
1284         struct rtable *rt = (struct rtable *)cork->dst;
1285         struct iphdr *iph;
1286         __be16 df = 0;
1287         __u8 ttl;
1288 
1289         if ((skb = __skb_dequeue(queue)) == NULL)
1290                 goto out;
1291         tail_skb = &(skb_shinfo(skb)->frag_list);
1292 
1293         /* move skb->data to ip header from ext header */
1294         if (skb->data < skb_network_header(skb))
1295                 __skb_pull(skb, skb_network_offset(skb));
1296         while ((tmp_skb = __skb_dequeue(queue)) != NULL) {
1297                 __skb_pull(tmp_skb, skb_network_header_len(skb));
1298                 *tail_skb = tmp_skb;
1299                 tail_skb = &(tmp_skb->next);
1300                 skb->len += tmp_skb->len;
1301                 skb->data_len += tmp_skb->len;
1302                 skb->truesize += tmp_skb->truesize;
1303                 tmp_skb->destructor = NULL;
1304                 tmp_skb->sk = NULL;
1305         }
1306 
1307         /* Unless user demanded real pmtu discovery (IP_PMTUDISC_DO), we allow
1308          * to fragment the frame generated here. No matter, what transforms
1309          * how transforms change size of the packet, it will come out.
1310          */
1311         if (inet->pmtudisc < IP_PMTUDISC_DO)
1312                 skb->local_df = 1;
1313 
1314         /* DF bit is set when we want to see DF on outgoing frames.
1315          * If local_df is set too, we still allow to fragment this frame
1316          * locally. */
1317         if (inet->pmtudisc == IP_PMTUDISC_DO ||
1318             inet->pmtudisc == IP_PMTUDISC_PROBE ||
1319             (skb->len <= dst_mtu(&rt->dst) &&
1320              ip_dont_fragment(sk, &rt->dst)))
1321                 df = htons(IP_DF);
1322 
1323         if (cork->flags & IPCORK_OPT)
1324                 opt = cork->opt;
1325 
1326         if (cork->ttl != 0)
1327                 ttl = cork->ttl;
1328         else if (rt->rt_type == RTN_MULTICAST)
1329                 ttl = inet->mc_ttl;
1330         else
1331                 ttl = ip_select_ttl(inet, &rt->dst);
1332 
1333         iph = ip_hdr(skb);
1334         iph->version = 4;
1335         iph->ihl = 5;
1336         iph->tos = (cork->tos != -1) ? cork->tos : inet->tos;
1337         iph->frag_off = df;
1338         iph->ttl = ttl;
1339         iph->protocol = sk->sk_protocol;
1340         ip_copy_addrs(iph, fl4);
1341         ip_select_ident(skb, &rt->dst, sk);
1342 
1343         if (opt) {
1344                 iph->ihl += opt->optlen>>2;
1345                 ip_options_build(skb, opt, cork->addr, rt, 0);
1346         }
1347 
1348         skb->priority = (cork->tos != -1) ? cork->priority: sk->sk_priority;
1349         skb->mark = sk->sk_mark;
1350         /*
1351          * Steal rt from cork.dst to avoid a pair of atomic_inc/atomic_dec
1352          * on dst refcount
1353          */
1354         cork->dst = NULL;
1355         skb_dst_set(skb, &rt->dst);
1356 
1357         if (iph->protocol == IPPROTO_ICMP)
1358                 icmp_out_count(net, ((struct icmphdr *)
1359                         skb_transport_header(skb))->type);
1360 
1361         ip_cork_release(cork);
1362 out:
1363         return skb;
1364 }
1365 
1366 int ip_send_skb(struct net *net, struct sk_buff *skb)
1367 {
1368         int err;
1369 
1370         err = ip_local_out(skb);
1371         if (err) {
1372                 if (err > 0)
1373                         err = net_xmit_errno(err);
1374                 if (err)
1375                         IP_INC_STATS(net, IPSTATS_MIB_OUTDISCARDS);
1376         }
1377 
1378         return err;
1379 }
1380 
1381 int ip_push_pending_frames(struct sock *sk, struct flowi4 *fl4)
1382 {
1383         struct sk_buff *skb;
1384 
1385         skb = ip_finish_skb(sk, fl4);
1386         if (!skb)
1387                 return 0;
1388 
1389         /* Netfilter gets whole the not fragmented skb. */
1390         return ip_send_skb(sock_net(sk), skb);
1391 }
1392 
1393 /*
1394  *      Throw away all pending data on the socket.
1395  */
1396 static void __ip_flush_pending_frames(struct sock *sk,
1397                                       struct sk_buff_head *queue,
1398                                       struct inet_cork *cork)
1399 {
1400         struct sk_buff *skb;
1401 
1402         while ((skb = __skb_dequeue_tail(queue)) != NULL)
1403                 kfree_skb(skb);
1404 
1405         ip_cork_release(cork);
1406 }
1407 
1408 void ip_flush_pending_frames(struct sock *sk)
1409 {
1410         __ip_flush_pending_frames(sk, &sk->sk_write_queue, &inet_sk(sk)->cork.base);
1411 }
1412 
1413 struct sk_buff *ip_make_skb(struct sock *sk,
1414                             struct flowi4 *fl4,
1415                             int getfrag(void *from, char *to, int offset,
1416                                         int len, int odd, struct sk_buff *skb),
1417                             void *from, int length, int transhdrlen,
1418                             struct ipcm_cookie *ipc, struct rtable **rtp,
1419                             unsigned int flags)
1420 {
1421         struct inet_cork cork;
1422         struct sk_buff_head queue;
1423         int err;
1424 
1425         if (flags & MSG_PROBE)
1426                 return NULL;
1427 
1428         __skb_queue_head_init(&queue);
1429 
1430         cork.flags = 0;
1431         cork.addr = 0;
1432         cork.opt = NULL;
1433         err = ip_setup_cork(sk, &cork, ipc, rtp);
1434         if (err)
1435                 return ERR_PTR(err);
1436 
1437         err = __ip_append_data(sk, fl4, &queue, &cork,
1438                                &current->task_frag, getfrag,
1439                                from, length, transhdrlen, flags);
1440         if (err) {
1441                 __ip_flush_pending_frames(sk, &queue, &cork);
1442                 return ERR_PTR(err);
1443         }
1444 
1445         return __ip_make_skb(sk, fl4, &queue, &cork);
1446 }
1447 
1448 /*
1449  *      Fetch data from kernel space and fill in checksum if needed.
1450  */
1451 static int ip_reply_glue_bits(void *dptr, char *to, int offset,
1452                               int len, int odd, struct sk_buff *skb)
1453 {
1454         __wsum csum;
1455 
1456         csum = csum_partial_copy_nocheck(dptr+offset, to, len, 0);
1457         skb->csum = csum_block_add(skb->csum, csum, odd);
1458         return 0;
1459 }
1460 
1461 /*
1462  *      Generic function to send a packet as reply to another packet.
1463  *      Used to send some TCP resets/acks so far.
1464  *
1465  *      Use a fake percpu inet socket to avoid false sharing and contention.
1466  */
1467 static DEFINE_PER_CPU(struct inet_sock, unicast_sock) = {
1468         .sk = {
1469                 .__sk_common = {
1470                         .skc_refcnt = ATOMIC_INIT(1),
1471                 },
1472                 .sk_wmem_alloc  = ATOMIC_INIT(1),
1473                 .sk_allocation  = GFP_ATOMIC,
1474                 .sk_flags       = (1UL << SOCK_USE_WRITE_QUEUE),
1475         },
1476         .pmtudisc       = IP_PMTUDISC_WANT,
1477         .uc_ttl         = -1,
1478 };
1479 
1480 void ip_send_unicast_reply(struct net *net, struct sk_buff *skb, __be32 daddr,
1481                            __be32 saddr, const struct ip_reply_arg *arg,
1482                            unsigned int len)
1483 {
1484         struct ip_options_data replyopts;
1485         struct ipcm_cookie ipc;
1486         struct flowi4 fl4;
1487         struct rtable *rt = skb_rtable(skb);
1488         struct sk_buff *nskb;
1489         struct sock *sk;
1490         struct inet_sock *inet;
1491 
1492         if (ip_options_echo(&replyopts.opt.opt, skb))
1493                 return;
1494 
1495         ipc.addr = daddr;
1496         ipc.opt = NULL;
1497         ipc.tx_flags = 0;
1498         ipc.ttl = 0;
1499         ipc.tos = -1;
1500 
1501         if (replyopts.opt.opt.optlen) {
1502                 ipc.opt = &replyopts.opt;
1503 
1504                 if (replyopts.opt.opt.srr)
1505                         daddr = replyopts.opt.opt.faddr;
1506         }
1507 
1508         flowi4_init_output(&fl4, arg->bound_dev_if, 0,
1509                            RT_TOS(arg->tos),
1510                            RT_SCOPE_UNIVERSE, ip_hdr(skb)->protocol,
1511                            ip_reply_arg_flowi_flags(arg),
1512                            daddr, saddr,
1513                            tcp_hdr(skb)->source, tcp_hdr(skb)->dest);
1514         security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
1515         rt = ip_route_output_key(net, &fl4);
1516         if (IS_ERR(rt))
1517                 return;
1518 
1519         inet = &get_cpu_var(unicast_sock);
1520 
1521         inet->tos = arg->tos;
1522         sk = &inet->sk;
1523         sk->sk_priority = skb->priority;
1524         sk->sk_protocol = ip_hdr(skb)->protocol;
1525         sk->sk_bound_dev_if = arg->bound_dev_if;
1526         sock_net_set(sk, net);
1527         __skb_queue_head_init(&sk->sk_write_queue);
1528         sk->sk_sndbuf = sysctl_wmem_default;
1529         ip_append_data(sk, &fl4, ip_reply_glue_bits, arg->iov->iov_base, len, 0,
1530                        &ipc, &rt, MSG_DONTWAIT);
1531         nskb = skb_peek(&sk->sk_write_queue);
1532         if (nskb) {
1533                 if (arg->csumoffset >= 0)
1534                         *((__sum16 *)skb_transport_header(nskb) +
1535                           arg->csumoffset) = csum_fold(csum_add(nskb->csum,
1536                                                                 arg->csum));
1537                 nskb->ip_summed = CHECKSUM_NONE;
1538                 skb_orphan(nskb);
1539                 skb_set_queue_mapping(nskb, skb_get_queue_mapping(skb));
1540                 ip_push_pending_frames(sk, &fl4);
1541         }
1542 
1543         put_cpu_var(unicast_sock);
1544 
1545         ip_rt_put(rt);
1546 }
1547 
1548 void __init ip_init(void)
1549 {
1550         ip_rt_init();
1551         inet_initpeers();
1552 
1553 #if defined(CONFIG_IP_MULTICAST)
1554         igmp_mc_init();
1555 #endif
1556 }
1557 

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