Version:  2.0.40 2.2.26 2.4.37 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0

Linux/net/ipv4/ip_output.c

  1 /*
  2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
  3  *              operating system.  INET is implemented using the  BSD Socket
  4  *              interface as the means of communication with the user level.
  5  *
  6  *              The Internet Protocol (IP) output module.
  7  *
  8  * Authors:     Ross Biro
  9  *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 10  *              Donald Becker, <becker@super.org>
 11  *              Alan Cox, <Alan.Cox@linux.org>
 12  *              Richard Underwood
 13  *              Stefan Becker, <stefanb@yello.ping.de>
 14  *              Jorge Cwik, <jorge@laser.satlink.net>
 15  *              Arnt Gulbrandsen, <agulbra@nvg.unit.no>
 16  *              Hirokazu Takahashi, <taka@valinux.co.jp>
 17  *
 18  *      See ip_input.c for original log
 19  *
 20  *      Fixes:
 21  *              Alan Cox        :       Missing nonblock feature in ip_build_xmit.
 22  *              Mike Kilburn    :       htons() missing in ip_build_xmit.
 23  *              Bradford Johnson:       Fix faulty handling of some frames when
 24  *                                      no route is found.
 25  *              Alexander Demenshin:    Missing sk/skb free in ip_queue_xmit
 26  *                                      (in case if packet not accepted by
 27  *                                      output firewall rules)
 28  *              Mike McLagan    :       Routing by source
 29  *              Alexey Kuznetsov:       use new route cache
 30  *              Andi Kleen:             Fix broken PMTU recovery and remove
 31  *                                      some redundant tests.
 32  *      Vitaly E. Lavrov        :       Transparent proxy revived after year coma.
 33  *              Andi Kleen      :       Replace ip_reply with ip_send_reply.
 34  *              Andi Kleen      :       Split fast and slow ip_build_xmit path
 35  *                                      for decreased register pressure on x86
 36  *                                      and more readibility.
 37  *              Marc Boucher    :       When call_out_firewall returns FW_QUEUE,
 38  *                                      silently drop skb instead of failing with -EPERM.
 39  *              Detlev Wengorz  :       Copy protocol for fragments.
 40  *              Hirokazu Takahashi:     HW checksumming for outgoing UDP
 41  *                                      datagrams.
 42  *              Hirokazu Takahashi:     sendfile() on UDP works now.
 43  */
 44 
 45 #include <asm/uaccess.h>
 46 #include <linux/module.h>
 47 #include <linux/types.h>
 48 #include <linux/kernel.h>
 49 #include <linux/mm.h>
 50 #include <linux/string.h>
 51 #include <linux/errno.h>
 52 #include <linux/highmem.h>
 53 #include <linux/slab.h>
 54 
 55 #include <linux/socket.h>
 56 #include <linux/sockios.h>
 57 #include <linux/in.h>
 58 #include <linux/inet.h>
 59 #include <linux/netdevice.h>
 60 #include <linux/etherdevice.h>
 61 #include <linux/proc_fs.h>
 62 #include <linux/stat.h>
 63 #include <linux/init.h>
 64 
 65 #include <net/snmp.h>
 66 #include <net/ip.h>
 67 #include <net/protocol.h>
 68 #include <net/route.h>
 69 #include <net/xfrm.h>
 70 #include <linux/skbuff.h>
 71 #include <net/sock.h>
 72 #include <net/arp.h>
 73 #include <net/icmp.h>
 74 #include <net/checksum.h>
 75 #include <net/inetpeer.h>
 76 #include <linux/igmp.h>
 77 #include <linux/netfilter_ipv4.h>
 78 #include <linux/netfilter_bridge.h>
 79 #include <linux/mroute.h>
 80 #include <linux/netlink.h>
 81 #include <linux/tcp.h>
 82 
 83 int sysctl_ip_default_ttl __read_mostly = IPDEFTTL;
 84 EXPORT_SYMBOL(sysctl_ip_default_ttl);
 85 
 86 /* Generate a checksum for an outgoing IP datagram. */
 87 void ip_send_check(struct iphdr *iph)
 88 {
 89         iph->check = 0;
 90         iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
 91 }
 92 EXPORT_SYMBOL(ip_send_check);
 93 
 94 int __ip_local_out(struct sk_buff *skb)
 95 {
 96         struct iphdr *iph = ip_hdr(skb);
 97 
 98         iph->tot_len = htons(skb->len);
 99         ip_send_check(iph);
100         return nf_hook(NFPROTO_IPV4, NF_INET_LOCAL_OUT, skb, NULL,
101                        skb_dst(skb)->dev, dst_output);
102 }
103 
104 int ip_local_out_sk(struct sock *sk, struct sk_buff *skb)
105 {
106         int err;
107 
108         err = __ip_local_out(skb);
109         if (likely(err == 1))
110                 err = dst_output_sk(sk, skb);
111 
112         return err;
113 }
114 EXPORT_SYMBOL_GPL(ip_local_out_sk);
115 
116 static inline int ip_select_ttl(struct inet_sock *inet, struct dst_entry *dst)
117 {
118         int ttl = inet->uc_ttl;
119 
120         if (ttl < 0)
121                 ttl = ip4_dst_hoplimit(dst);
122         return ttl;
123 }
124 
125 /*
126  *              Add an ip header to a skbuff and send it out.
127  *
128  */
129 int ip_build_and_send_pkt(struct sk_buff *skb, struct sock *sk,
130                           __be32 saddr, __be32 daddr, struct ip_options_rcu *opt)
131 {
132         struct inet_sock *inet = inet_sk(sk);
133         struct rtable *rt = skb_rtable(skb);
134         struct iphdr *iph;
135 
136         /* Build the IP header. */
137         skb_push(skb, sizeof(struct iphdr) + (opt ? opt->opt.optlen : 0));
138         skb_reset_network_header(skb);
139         iph = ip_hdr(skb);
140         iph->version  = 4;
141         iph->ihl      = 5;
142         iph->tos      = inet->tos;
143         if (ip_dont_fragment(sk, &rt->dst))
144                 iph->frag_off = htons(IP_DF);
145         else
146                 iph->frag_off = 0;
147         iph->ttl      = ip_select_ttl(inet, &rt->dst);
148         iph->daddr    = (opt && opt->opt.srr ? opt->opt.faddr : daddr);
149         iph->saddr    = saddr;
150         iph->protocol = sk->sk_protocol;
151         ip_select_ident(skb, sk);
152 
153         if (opt && opt->opt.optlen) {
154                 iph->ihl += opt->opt.optlen>>2;
155                 ip_options_build(skb, &opt->opt, daddr, rt, 0);
156         }
157 
158         skb->priority = sk->sk_priority;
159         skb->mark = sk->sk_mark;
160 
161         /* Send it out. */
162         return ip_local_out(skb);
163 }
164 EXPORT_SYMBOL_GPL(ip_build_and_send_pkt);
165 
166 static inline int ip_finish_output2(struct sk_buff *skb)
167 {
168         struct dst_entry *dst = skb_dst(skb);
169         struct rtable *rt = (struct rtable *)dst;
170         struct net_device *dev = dst->dev;
171         unsigned int hh_len = LL_RESERVED_SPACE(dev);
172         struct neighbour *neigh;
173         u32 nexthop;
174 
175         if (rt->rt_type == RTN_MULTICAST) {
176                 IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUTMCAST, skb->len);
177         } else if (rt->rt_type == RTN_BROADCAST)
178                 IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUTBCAST, skb->len);
179 
180         /* Be paranoid, rather than too clever. */
181         if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) {
182                 struct sk_buff *skb2;
183 
184                 skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev));
185                 if (skb2 == NULL) {
186                         kfree_skb(skb);
187                         return -ENOMEM;
188                 }
189                 if (skb->sk)
190                         skb_set_owner_w(skb2, skb->sk);
191                 consume_skb(skb);
192                 skb = skb2;
193         }
194 
195         rcu_read_lock_bh();
196         nexthop = (__force u32) rt_nexthop(rt, ip_hdr(skb)->daddr);
197         neigh = __ipv4_neigh_lookup_noref(dev, nexthop);
198         if (unlikely(!neigh))
199                 neigh = __neigh_create(&arp_tbl, &nexthop, dev, false);
200         if (!IS_ERR(neigh)) {
201                 int res = dst_neigh_output(dst, neigh, skb);
202 
203                 rcu_read_unlock_bh();
204                 return res;
205         }
206         rcu_read_unlock_bh();
207 
208         net_dbg_ratelimited("%s: No header cache and no neighbour!\n",
209                             __func__);
210         kfree_skb(skb);
211         return -EINVAL;
212 }
213 
214 static int ip_finish_output_gso(struct sk_buff *skb)
215 {
216         netdev_features_t features;
217         struct sk_buff *segs;
218         int ret = 0;
219 
220         /* common case: locally created skb or seglen is <= mtu */
221         if (((IPCB(skb)->flags & IPSKB_FORWARDED) == 0) ||
222               skb_gso_network_seglen(skb) <= ip_skb_dst_mtu(skb))
223                 return ip_finish_output2(skb);
224 
225         /* Slowpath -  GSO segment length is exceeding the dst MTU.
226          *
227          * This can happen in two cases:
228          * 1) TCP GRO packet, DF bit not set
229          * 2) skb arrived via virtio-net, we thus get TSO/GSO skbs directly
230          * from host network stack.
231          */
232         features = netif_skb_features(skb);
233         segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK);
234         if (IS_ERR_OR_NULL(segs)) {
235                 kfree_skb(skb);
236                 return -ENOMEM;
237         }
238 
239         consume_skb(skb);
240 
241         do {
242                 struct sk_buff *nskb = segs->next;
243                 int err;
244 
245                 segs->next = NULL;
246                 err = ip_fragment(segs, ip_finish_output2);
247 
248                 if (err && ret == 0)
249                         ret = err;
250                 segs = nskb;
251         } while (segs);
252 
253         return ret;
254 }
255 
256 static int ip_finish_output(struct sk_buff *skb)
257 {
258 #if defined(CONFIG_NETFILTER) && defined(CONFIG_XFRM)
259         /* Policy lookup after SNAT yielded a new policy */
260         if (skb_dst(skb)->xfrm != NULL) {
261                 IPCB(skb)->flags |= IPSKB_REROUTED;
262                 return dst_output(skb);
263         }
264 #endif
265         if (skb_is_gso(skb))
266                 return ip_finish_output_gso(skb);
267 
268         if (skb->len > ip_skb_dst_mtu(skb))
269                 return ip_fragment(skb, ip_finish_output2);
270 
271         return ip_finish_output2(skb);
272 }
273 
274 int ip_mc_output(struct sock *sk, struct sk_buff *skb)
275 {
276         struct rtable *rt = skb_rtable(skb);
277         struct net_device *dev = rt->dst.dev;
278 
279         /*
280          *      If the indicated interface is up and running, send the packet.
281          */
282         IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUT, skb->len);
283 
284         skb->dev = dev;
285         skb->protocol = htons(ETH_P_IP);
286 
287         /*
288          *      Multicasts are looped back for other local users
289          */
290 
291         if (rt->rt_flags&RTCF_MULTICAST) {
292                 if (sk_mc_loop(sk)
293 #ifdef CONFIG_IP_MROUTE
294                 /* Small optimization: do not loopback not local frames,
295                    which returned after forwarding; they will be  dropped
296                    by ip_mr_input in any case.
297                    Note, that local frames are looped back to be delivered
298                    to local recipients.
299 
300                    This check is duplicated in ip_mr_input at the moment.
301                  */
302                     &&
303                     ((rt->rt_flags & RTCF_LOCAL) ||
304                      !(IPCB(skb)->flags & IPSKB_FORWARDED))
305 #endif
306                    ) {
307                         struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
308                         if (newskb)
309                                 NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING,
310                                         newskb, NULL, newskb->dev,
311                                         dev_loopback_xmit);
312                 }
313 
314                 /* Multicasts with ttl 0 must not go beyond the host */
315 
316                 if (ip_hdr(skb)->ttl == 0) {
317                         kfree_skb(skb);
318                         return 0;
319                 }
320         }
321 
322         if (rt->rt_flags&RTCF_BROADCAST) {
323                 struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
324                 if (newskb)
325                         NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING, newskb,
326                                 NULL, newskb->dev, dev_loopback_xmit);
327         }
328 
329         return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING, skb, NULL,
330                             skb->dev, ip_finish_output,
331                             !(IPCB(skb)->flags & IPSKB_REROUTED));
332 }
333 
334 int ip_output(struct sock *sk, struct sk_buff *skb)
335 {
336         struct net_device *dev = skb_dst(skb)->dev;
337 
338         IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUT, skb->len);
339 
340         skb->dev = dev;
341         skb->protocol = htons(ETH_P_IP);
342 
343         return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING, skb, NULL, dev,
344                             ip_finish_output,
345                             !(IPCB(skb)->flags & IPSKB_REROUTED));
346 }
347 
348 /*
349  * copy saddr and daddr, possibly using 64bit load/stores
350  * Equivalent to :
351  *   iph->saddr = fl4->saddr;
352  *   iph->daddr = fl4->daddr;
353  */
354 static void ip_copy_addrs(struct iphdr *iph, const struct flowi4 *fl4)
355 {
356         BUILD_BUG_ON(offsetof(typeof(*fl4), daddr) !=
357                      offsetof(typeof(*fl4), saddr) + sizeof(fl4->saddr));
358         memcpy(&iph->saddr, &fl4->saddr,
359                sizeof(fl4->saddr) + sizeof(fl4->daddr));
360 }
361 
362 /* Note: skb->sk can be different from sk, in case of tunnels */
363 int ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl)
364 {
365         struct inet_sock *inet = inet_sk(sk);
366         struct ip_options_rcu *inet_opt;
367         struct flowi4 *fl4;
368         struct rtable *rt;
369         struct iphdr *iph;
370         int res;
371 
372         /* Skip all of this if the packet is already routed,
373          * f.e. by something like SCTP.
374          */
375         rcu_read_lock();
376         inet_opt = rcu_dereference(inet->inet_opt);
377         fl4 = &fl->u.ip4;
378         rt = skb_rtable(skb);
379         if (rt != NULL)
380                 goto packet_routed;
381 
382         /* Make sure we can route this packet. */
383         rt = (struct rtable *)__sk_dst_check(sk, 0);
384         if (rt == NULL) {
385                 __be32 daddr;
386 
387                 /* Use correct destination address if we have options. */
388                 daddr = inet->inet_daddr;
389                 if (inet_opt && inet_opt->opt.srr)
390                         daddr = inet_opt->opt.faddr;
391 
392                 /* If this fails, retransmit mechanism of transport layer will
393                  * keep trying until route appears or the connection times
394                  * itself out.
395                  */
396                 rt = ip_route_output_ports(sock_net(sk), fl4, sk,
397                                            daddr, inet->inet_saddr,
398                                            inet->inet_dport,
399                                            inet->inet_sport,
400                                            sk->sk_protocol,
401                                            RT_CONN_FLAGS(sk),
402                                            sk->sk_bound_dev_if);
403                 if (IS_ERR(rt))
404                         goto no_route;
405                 sk_setup_caps(sk, &rt->dst);
406         }
407         skb_dst_set_noref(skb, &rt->dst);
408 
409 packet_routed:
410         if (inet_opt && inet_opt->opt.is_strictroute && rt->rt_uses_gateway)
411                 goto no_route;
412 
413         /* OK, we know where to send it, allocate and build IP header. */
414         skb_push(skb, sizeof(struct iphdr) + (inet_opt ? inet_opt->opt.optlen : 0));
415         skb_reset_network_header(skb);
416         iph = ip_hdr(skb);
417         *((__be16 *)iph) = htons((4 << 12) | (5 << 8) | (inet->tos & 0xff));
418         if (ip_dont_fragment(sk, &rt->dst) && !skb->ignore_df)
419                 iph->frag_off = htons(IP_DF);
420         else
421                 iph->frag_off = 0;
422         iph->ttl      = ip_select_ttl(inet, &rt->dst);
423         iph->protocol = sk->sk_protocol;
424         ip_copy_addrs(iph, fl4);
425 
426         /* Transport layer set skb->h.foo itself. */
427 
428         if (inet_opt && inet_opt->opt.optlen) {
429                 iph->ihl += inet_opt->opt.optlen >> 2;
430                 ip_options_build(skb, &inet_opt->opt, inet->inet_daddr, rt, 0);
431         }
432 
433         ip_select_ident_segs(skb, sk, skb_shinfo(skb)->gso_segs ?: 1);
434 
435         /* TODO : should we use skb->sk here instead of sk ? */
436         skb->priority = sk->sk_priority;
437         skb->mark = sk->sk_mark;
438 
439         res = ip_local_out(skb);
440         rcu_read_unlock();
441         return res;
442 
443 no_route:
444         rcu_read_unlock();
445         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);
446         kfree_skb(skb);
447         return -EHOSTUNREACH;
448 }
449 EXPORT_SYMBOL(ip_queue_xmit);
450 
451 
452 static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
453 {
454         to->pkt_type = from->pkt_type;
455         to->priority = from->priority;
456         to->protocol = from->protocol;
457         skb_dst_drop(to);
458         skb_dst_copy(to, from);
459         to->dev = from->dev;
460         to->mark = from->mark;
461 
462         /* Copy the flags to each fragment. */
463         IPCB(to)->flags = IPCB(from)->flags;
464 
465 #ifdef CONFIG_NET_SCHED
466         to->tc_index = from->tc_index;
467 #endif
468         nf_copy(to, from);
469 #if defined(CONFIG_IP_VS) || defined(CONFIG_IP_VS_MODULE)
470         to->ipvs_property = from->ipvs_property;
471 #endif
472         skb_copy_secmark(to, from);
473 }
474 
475 /*
476  *      This IP datagram is too large to be sent in one piece.  Break it up into
477  *      smaller pieces (each of size equal to IP header plus
478  *      a block of the data of the original IP data part) that will yet fit in a
479  *      single device frame, and queue such a frame for sending.
480  */
481 
482 int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
483 {
484         struct iphdr *iph;
485         int ptr;
486         struct net_device *dev;
487         struct sk_buff *skb2;
488         unsigned int mtu, hlen, left, len, ll_rs;
489         int offset;
490         __be16 not_last_frag;
491         struct rtable *rt = skb_rtable(skb);
492         int err = 0;
493 
494         dev = rt->dst.dev;
495 
496         /*
497          *      Point into the IP datagram header.
498          */
499 
500         iph = ip_hdr(skb);
501 
502         mtu = ip_skb_dst_mtu(skb);
503         if (unlikely(((iph->frag_off & htons(IP_DF)) && !skb->ignore_df) ||
504                      (IPCB(skb)->frag_max_size &&
505                       IPCB(skb)->frag_max_size > mtu))) {
506                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
507                 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
508                           htonl(mtu));
509                 kfree_skb(skb);
510                 return -EMSGSIZE;
511         }
512 
513         /*
514          *      Setup starting values.
515          */
516 
517         hlen = iph->ihl * 4;
518         mtu = mtu - hlen;       /* Size of data space */
519 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
520         if (skb->nf_bridge)
521                 mtu -= nf_bridge_mtu_reduction(skb);
522 #endif
523         IPCB(skb)->flags |= IPSKB_FRAG_COMPLETE;
524 
525         /* When frag_list is given, use it. First, check its validity:
526          * some transformers could create wrong frag_list or break existing
527          * one, it is not prohibited. In this case fall back to copying.
528          *
529          * LATER: this step can be merged to real generation of fragments,
530          * we can switch to copy when see the first bad fragment.
531          */
532         if (skb_has_frag_list(skb)) {
533                 struct sk_buff *frag, *frag2;
534                 int first_len = skb_pagelen(skb);
535 
536                 if (first_len - hlen > mtu ||
537                     ((first_len - hlen) & 7) ||
538                     ip_is_fragment(iph) ||
539                     skb_cloned(skb))
540                         goto slow_path;
541 
542                 skb_walk_frags(skb, frag) {
543                         /* Correct geometry. */
544                         if (frag->len > mtu ||
545                             ((frag->len & 7) && frag->next) ||
546                             skb_headroom(frag) < hlen)
547                                 goto slow_path_clean;
548 
549                         /* Partially cloned skb? */
550                         if (skb_shared(frag))
551                                 goto slow_path_clean;
552 
553                         BUG_ON(frag->sk);
554                         if (skb->sk) {
555                                 frag->sk = skb->sk;
556                                 frag->destructor = sock_wfree;
557                         }
558                         skb->truesize -= frag->truesize;
559                 }
560 
561                 /* Everything is OK. Generate! */
562 
563                 err = 0;
564                 offset = 0;
565                 frag = skb_shinfo(skb)->frag_list;
566                 skb_frag_list_init(skb);
567                 skb->data_len = first_len - skb_headlen(skb);
568                 skb->len = first_len;
569                 iph->tot_len = htons(first_len);
570                 iph->frag_off = htons(IP_MF);
571                 ip_send_check(iph);
572 
573                 for (;;) {
574                         /* Prepare header of the next frame,
575                          * before previous one went down. */
576                         if (frag) {
577                                 frag->ip_summed = CHECKSUM_NONE;
578                                 skb_reset_transport_header(frag);
579                                 __skb_push(frag, hlen);
580                                 skb_reset_network_header(frag);
581                                 memcpy(skb_network_header(frag), iph, hlen);
582                                 iph = ip_hdr(frag);
583                                 iph->tot_len = htons(frag->len);
584                                 ip_copy_metadata(frag, skb);
585                                 if (offset == 0)
586                                         ip_options_fragment(frag);
587                                 offset += skb->len - hlen;
588                                 iph->frag_off = htons(offset>>3);
589                                 if (frag->next != NULL)
590                                         iph->frag_off |= htons(IP_MF);
591                                 /* Ready, complete checksum */
592                                 ip_send_check(iph);
593                         }
594 
595                         err = output(skb);
596 
597                         if (!err)
598                                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGCREATES);
599                         if (err || !frag)
600                                 break;
601 
602                         skb = frag;
603                         frag = skb->next;
604                         skb->next = NULL;
605                 }
606 
607                 if (err == 0) {
608                         IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGOKS);
609                         return 0;
610                 }
611 
612                 while (frag) {
613                         skb = frag->next;
614                         kfree_skb(frag);
615                         frag = skb;
616                 }
617                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
618                 return err;
619 
620 slow_path_clean:
621                 skb_walk_frags(skb, frag2) {
622                         if (frag2 == frag)
623                                 break;
624                         frag2->sk = NULL;
625                         frag2->destructor = NULL;
626                         skb->truesize += frag2->truesize;
627                 }
628         }
629 
630 slow_path:
631         /* for offloaded checksums cleanup checksum before fragmentation */
632         if ((skb->ip_summed == CHECKSUM_PARTIAL) && skb_checksum_help(skb))
633                 goto fail;
634         iph = ip_hdr(skb);
635 
636         left = skb->len - hlen;         /* Space per frame */
637         ptr = hlen;             /* Where to start from */
638 
639         /* for bridged IP traffic encapsulated inside f.e. a vlan header,
640          * we need to make room for the encapsulating header
641          */
642         ll_rs = LL_RESERVED_SPACE_EXTRA(rt->dst.dev, nf_bridge_pad(skb));
643 
644         /*
645          *      Fragment the datagram.
646          */
647 
648         offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3;
649         not_last_frag = iph->frag_off & htons(IP_MF);
650 
651         /*
652          *      Keep copying data until we run out.
653          */
654 
655         while (left > 0) {
656                 len = left;
657                 /* IF: it doesn't fit, use 'mtu' - the data space left */
658                 if (len > mtu)
659                         len = mtu;
660                 /* IF: we are not sending up to and including the packet end
661                    then align the next start on an eight byte boundary */
662                 if (len < left) {
663                         len &= ~7;
664                 }
665 
666                 /* Allocate buffer */
667                 skb2 = alloc_skb(len + hlen + ll_rs, GFP_ATOMIC);
668                 if (!skb2) {
669                         err = -ENOMEM;
670                         goto fail;
671                 }
672 
673                 /*
674                  *      Set up data on packet
675                  */
676 
677                 ip_copy_metadata(skb2, skb);
678                 skb_reserve(skb2, ll_rs);
679                 skb_put(skb2, len + hlen);
680                 skb_reset_network_header(skb2);
681                 skb2->transport_header = skb2->network_header + hlen;
682 
683                 /*
684                  *      Charge the memory for the fragment to any owner
685                  *      it might possess
686                  */
687 
688                 if (skb->sk)
689                         skb_set_owner_w(skb2, skb->sk);
690 
691                 /*
692                  *      Copy the packet header into the new buffer.
693                  */
694 
695                 skb_copy_from_linear_data(skb, skb_network_header(skb2), hlen);
696 
697                 /*
698                  *      Copy a block of the IP datagram.
699                  */
700                 if (skb_copy_bits(skb, ptr, skb_transport_header(skb2), len))
701                         BUG();
702                 left -= len;
703 
704                 /*
705                  *      Fill in the new header fields.
706                  */
707                 iph = ip_hdr(skb2);
708                 iph->frag_off = htons((offset >> 3));
709 
710                 /* ANK: dirty, but effective trick. Upgrade options only if
711                  * the segment to be fragmented was THE FIRST (otherwise,
712                  * options are already fixed) and make it ONCE
713                  * on the initial skb, so that all the following fragments
714                  * will inherit fixed options.
715                  */
716                 if (offset == 0)
717                         ip_options_fragment(skb);
718 
719                 /*
720                  *      Added AC : If we are fragmenting a fragment that's not the
721                  *                 last fragment then keep MF on each bit
722                  */
723                 if (left > 0 || not_last_frag)
724                         iph->frag_off |= htons(IP_MF);
725                 ptr += len;
726                 offset += len;
727 
728                 /*
729                  *      Put this fragment into the sending queue.
730                  */
731                 iph->tot_len = htons(len + hlen);
732 
733                 ip_send_check(iph);
734 
735                 err = output(skb2);
736                 if (err)
737                         goto fail;
738 
739                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGCREATES);
740         }
741         consume_skb(skb);
742         IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGOKS);
743         return err;
744 
745 fail:
746         kfree_skb(skb);
747         IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
748         return err;
749 }
750 EXPORT_SYMBOL(ip_fragment);
751 
752 int
753 ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
754 {
755         struct msghdr *msg = from;
756 
757         if (skb->ip_summed == CHECKSUM_PARTIAL) {
758                 if (copy_from_iter(to, len, &msg->msg_iter) != len)
759                         return -EFAULT;
760         } else {
761                 __wsum csum = 0;
762                 if (csum_and_copy_from_iter(to, len, &csum, &msg->msg_iter) != len)
763                         return -EFAULT;
764                 skb->csum = csum_block_add(skb->csum, csum, odd);
765         }
766         return 0;
767 }
768 EXPORT_SYMBOL(ip_generic_getfrag);
769 
770 static inline __wsum
771 csum_page(struct page *page, int offset, int copy)
772 {
773         char *kaddr;
774         __wsum csum;
775         kaddr = kmap(page);
776         csum = csum_partial(kaddr + offset, copy, 0);
777         kunmap(page);
778         return csum;
779 }
780 
781 static inline int ip_ufo_append_data(struct sock *sk,
782                         struct sk_buff_head *queue,
783                         int getfrag(void *from, char *to, int offset, int len,
784                                int odd, struct sk_buff *skb),
785                         void *from, int length, int hh_len, int fragheaderlen,
786                         int transhdrlen, int maxfraglen, unsigned int flags)
787 {
788         struct sk_buff *skb;
789         int err;
790 
791         /* There is support for UDP fragmentation offload by network
792          * device, so create one single skb packet containing complete
793          * udp datagram
794          */
795         if ((skb = skb_peek_tail(queue)) == NULL) {
796                 skb = sock_alloc_send_skb(sk,
797                         hh_len + fragheaderlen + transhdrlen + 20,
798                         (flags & MSG_DONTWAIT), &err);
799 
800                 if (skb == NULL)
801                         return err;
802 
803                 /* reserve space for Hardware header */
804                 skb_reserve(skb, hh_len);
805 
806                 /* create space for UDP/IP header */
807                 skb_put(skb, fragheaderlen + transhdrlen);
808 
809                 /* initialize network header pointer */
810                 skb_reset_network_header(skb);
811 
812                 /* initialize protocol header pointer */
813                 skb->transport_header = skb->network_header + fragheaderlen;
814 
815                 skb->csum = 0;
816 
817 
818                 __skb_queue_tail(queue, skb);
819         } else if (skb_is_gso(skb)) {
820                 goto append;
821         }
822 
823         skb->ip_summed = CHECKSUM_PARTIAL;
824         /* specify the length of each IP datagram fragment */
825         skb_shinfo(skb)->gso_size = maxfraglen - fragheaderlen;
826         skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
827 
828 append:
829         return skb_append_datato_frags(sk, skb, getfrag, from,
830                                        (length - transhdrlen));
831 }
832 
833 static int __ip_append_data(struct sock *sk,
834                             struct flowi4 *fl4,
835                             struct sk_buff_head *queue,
836                             struct inet_cork *cork,
837                             struct page_frag *pfrag,
838                             int getfrag(void *from, char *to, int offset,
839                                         int len, int odd, struct sk_buff *skb),
840                             void *from, int length, int transhdrlen,
841                             unsigned int flags)
842 {
843         struct inet_sock *inet = inet_sk(sk);
844         struct sk_buff *skb;
845 
846         struct ip_options *opt = cork->opt;
847         int hh_len;
848         int exthdrlen;
849         int mtu;
850         int copy;
851         int err;
852         int offset = 0;
853         unsigned int maxfraglen, fragheaderlen, maxnonfragsize;
854         int csummode = CHECKSUM_NONE;
855         struct rtable *rt = (struct rtable *)cork->dst;
856         u32 tskey = 0;
857 
858         skb = skb_peek_tail(queue);
859 
860         exthdrlen = !skb ? rt->dst.header_len : 0;
861         mtu = cork->fragsize;
862         if (cork->tx_flags & SKBTX_ANY_SW_TSTAMP &&
863             sk->sk_tsflags & SOF_TIMESTAMPING_OPT_ID)
864                 tskey = sk->sk_tskey++;
865 
866         hh_len = LL_RESERVED_SPACE(rt->dst.dev);
867 
868         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
869         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
870         maxnonfragsize = ip_sk_ignore_df(sk) ? 0xFFFF : mtu;
871 
872         if (cork->length + length > maxnonfragsize - fragheaderlen) {
873                 ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
874                                mtu - (opt ? opt->optlen : 0));
875                 return -EMSGSIZE;
876         }
877 
878         /*
879          * transhdrlen > 0 means that this is the first fragment and we wish
880          * it won't be fragmented in the future.
881          */
882         if (transhdrlen &&
883             length + fragheaderlen <= mtu &&
884             rt->dst.dev->features & NETIF_F_V4_CSUM &&
885             !exthdrlen)
886                 csummode = CHECKSUM_PARTIAL;
887 
888         cork->length += length;
889         if (((length > mtu) || (skb && skb_is_gso(skb))) &&
890             (sk->sk_protocol == IPPROTO_UDP) &&
891             (rt->dst.dev->features & NETIF_F_UFO) && !rt->dst.header_len &&
892             (sk->sk_type == SOCK_DGRAM)) {
893                 err = ip_ufo_append_data(sk, queue, getfrag, from, length,
894                                          hh_len, fragheaderlen, transhdrlen,
895                                          maxfraglen, flags);
896                 if (err)
897                         goto error;
898                 return 0;
899         }
900 
901         /* So, what's going on in the loop below?
902          *
903          * We use calculated fragment length to generate chained skb,
904          * each of segments is IP fragment ready for sending to network after
905          * adding appropriate IP header.
906          */
907 
908         if (!skb)
909                 goto alloc_new_skb;
910 
911         while (length > 0) {
912                 /* Check if the remaining data fits into current packet. */
913                 copy = mtu - skb->len;
914                 if (copy < length)
915                         copy = maxfraglen - skb->len;
916                 if (copy <= 0) {
917                         char *data;
918                         unsigned int datalen;
919                         unsigned int fraglen;
920                         unsigned int fraggap;
921                         unsigned int alloclen;
922                         struct sk_buff *skb_prev;
923 alloc_new_skb:
924                         skb_prev = skb;
925                         if (skb_prev)
926                                 fraggap = skb_prev->len - maxfraglen;
927                         else
928                                 fraggap = 0;
929 
930                         /*
931                          * If remaining data exceeds the mtu,
932                          * we know we need more fragment(s).
933                          */
934                         datalen = length + fraggap;
935                         if (datalen > mtu - fragheaderlen)
936                                 datalen = maxfraglen - fragheaderlen;
937                         fraglen = datalen + fragheaderlen;
938 
939                         if ((flags & MSG_MORE) &&
940                             !(rt->dst.dev->features&NETIF_F_SG))
941                                 alloclen = mtu;
942                         else
943                                 alloclen = fraglen;
944 
945                         alloclen += exthdrlen;
946 
947                         /* The last fragment gets additional space at tail.
948                          * Note, with MSG_MORE we overallocate on fragments,
949                          * because we have no idea what fragment will be
950                          * the last.
951                          */
952                         if (datalen == length + fraggap)
953                                 alloclen += rt->dst.trailer_len;
954 
955                         if (transhdrlen) {
956                                 skb = sock_alloc_send_skb(sk,
957                                                 alloclen + hh_len + 15,
958                                                 (flags & MSG_DONTWAIT), &err);
959                         } else {
960                                 skb = NULL;
961                                 if (atomic_read(&sk->sk_wmem_alloc) <=
962                                     2 * sk->sk_sndbuf)
963                                         skb = sock_wmalloc(sk,
964                                                            alloclen + hh_len + 15, 1,
965                                                            sk->sk_allocation);
966                                 if (unlikely(skb == NULL))
967                                         err = -ENOBUFS;
968                         }
969                         if (skb == NULL)
970                                 goto error;
971 
972                         /*
973                          *      Fill in the control structures
974                          */
975                         skb->ip_summed = csummode;
976                         skb->csum = 0;
977                         skb_reserve(skb, hh_len);
978 
979                         /* only the initial fragment is time stamped */
980                         skb_shinfo(skb)->tx_flags = cork->tx_flags;
981                         cork->tx_flags = 0;
982                         skb_shinfo(skb)->tskey = tskey;
983                         tskey = 0;
984 
985                         /*
986                          *      Find where to start putting bytes.
987                          */
988                         data = skb_put(skb, fraglen + exthdrlen);
989                         skb_set_network_header(skb, exthdrlen);
990                         skb->transport_header = (skb->network_header +
991                                                  fragheaderlen);
992                         data += fragheaderlen + exthdrlen;
993 
994                         if (fraggap) {
995                                 skb->csum = skb_copy_and_csum_bits(
996                                         skb_prev, maxfraglen,
997                                         data + transhdrlen, fraggap, 0);
998                                 skb_prev->csum = csum_sub(skb_prev->csum,
999                                                           skb->csum);
1000                                 data += fraggap;
1001                                 pskb_trim_unique(skb_prev, maxfraglen);
1002                         }
1003 
1004                         copy = datalen - transhdrlen - fraggap;
1005                         if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
1006                                 err = -EFAULT;
1007                                 kfree_skb(skb);
1008                                 goto error;
1009                         }
1010 
1011                         offset += copy;
1012                         length -= datalen - fraggap;
1013                         transhdrlen = 0;
1014                         exthdrlen = 0;
1015                         csummode = CHECKSUM_NONE;
1016 
1017                         /*
1018                          * Put the packet on the pending queue.
1019                          */
1020                         __skb_queue_tail(queue, skb);
1021                         continue;
1022                 }
1023 
1024                 if (copy > length)
1025                         copy = length;
1026 
1027                 if (!(rt->dst.dev->features&NETIF_F_SG)) {
1028                         unsigned int off;
1029 
1030                         off = skb->len;
1031                         if (getfrag(from, skb_put(skb, copy),
1032                                         offset, copy, off, skb) < 0) {
1033                                 __skb_trim(skb, off);
1034                                 err = -EFAULT;
1035                                 goto error;
1036                         }
1037                 } else {
1038                         int i = skb_shinfo(skb)->nr_frags;
1039 
1040                         err = -ENOMEM;
1041                         if (!sk_page_frag_refill(sk, pfrag))
1042                                 goto error;
1043 
1044                         if (!skb_can_coalesce(skb, i, pfrag->page,
1045                                               pfrag->offset)) {
1046                                 err = -EMSGSIZE;
1047                                 if (i == MAX_SKB_FRAGS)
1048                                         goto error;
1049 
1050                                 __skb_fill_page_desc(skb, i, pfrag->page,
1051                                                      pfrag->offset, 0);
1052                                 skb_shinfo(skb)->nr_frags = ++i;
1053                                 get_page(pfrag->page);
1054                         }
1055                         copy = min_t(int, copy, pfrag->size - pfrag->offset);
1056                         if (getfrag(from,
1057                                     page_address(pfrag->page) + pfrag->offset,
1058                                     offset, copy, skb->len, skb) < 0)
1059                                 goto error_efault;
1060 
1061                         pfrag->offset += copy;
1062                         skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
1063                         skb->len += copy;
1064                         skb->data_len += copy;
1065                         skb->truesize += copy;
1066                         atomic_add(copy, &sk->sk_wmem_alloc);
1067                 }
1068                 offset += copy;
1069                 length -= copy;
1070         }
1071 
1072         return 0;
1073 
1074 error_efault:
1075         err = -EFAULT;
1076 error:
1077         cork->length -= length;
1078         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1079         return err;
1080 }
1081 
1082 static int ip_setup_cork(struct sock *sk, struct inet_cork *cork,
1083                          struct ipcm_cookie *ipc, struct rtable **rtp)
1084 {
1085         struct ip_options_rcu *opt;
1086         struct rtable *rt;
1087 
1088         /*
1089          * setup for corking.
1090          */
1091         opt = ipc->opt;
1092         if (opt) {
1093                 if (cork->opt == NULL) {
1094                         cork->opt = kmalloc(sizeof(struct ip_options) + 40,
1095                                             sk->sk_allocation);
1096                         if (unlikely(cork->opt == NULL))
1097                                 return -ENOBUFS;
1098                 }
1099                 memcpy(cork->opt, &opt->opt, sizeof(struct ip_options) + opt->opt.optlen);
1100                 cork->flags |= IPCORK_OPT;
1101                 cork->addr = ipc->addr;
1102         }
1103         rt = *rtp;
1104         if (unlikely(!rt))
1105                 return -EFAULT;
1106         /*
1107          * We steal reference to this route, caller should not release it
1108          */
1109         *rtp = NULL;
1110         cork->fragsize = ip_sk_use_pmtu(sk) ?
1111                          dst_mtu(&rt->dst) : rt->dst.dev->mtu;
1112         cork->dst = &rt->dst;
1113         cork->length = 0;
1114         cork->ttl = ipc->ttl;
1115         cork->tos = ipc->tos;
1116         cork->priority = ipc->priority;
1117         cork->tx_flags = ipc->tx_flags;
1118 
1119         return 0;
1120 }
1121 
1122 /*
1123  *      ip_append_data() and ip_append_page() can make one large IP datagram
1124  *      from many pieces of data. Each pieces will be holded on the socket
1125  *      until ip_push_pending_frames() is called. Each piece can be a page
1126  *      or non-page data.
1127  *
1128  *      Not only UDP, other transport protocols - e.g. raw sockets - can use
1129  *      this interface potentially.
1130  *
1131  *      LATER: length must be adjusted by pad at tail, when it is required.
1132  */
1133 int ip_append_data(struct sock *sk, struct flowi4 *fl4,
1134                    int getfrag(void *from, char *to, int offset, int len,
1135                                int odd, struct sk_buff *skb),
1136                    void *from, int length, int transhdrlen,
1137                    struct ipcm_cookie *ipc, struct rtable **rtp,
1138                    unsigned int flags)
1139 {
1140         struct inet_sock *inet = inet_sk(sk);
1141         int err;
1142 
1143         if (flags&MSG_PROBE)
1144                 return 0;
1145 
1146         if (skb_queue_empty(&sk->sk_write_queue)) {
1147                 err = ip_setup_cork(sk, &inet->cork.base, ipc, rtp);
1148                 if (err)
1149                         return err;
1150         } else {
1151                 transhdrlen = 0;
1152         }
1153 
1154         return __ip_append_data(sk, fl4, &sk->sk_write_queue, &inet->cork.base,
1155                                 sk_page_frag(sk), getfrag,
1156                                 from, length, transhdrlen, flags);
1157 }
1158 
1159 ssize_t ip_append_page(struct sock *sk, struct flowi4 *fl4, struct page *page,
1160                        int offset, size_t size, int flags)
1161 {
1162         struct inet_sock *inet = inet_sk(sk);
1163         struct sk_buff *skb;
1164         struct rtable *rt;
1165         struct ip_options *opt = NULL;
1166         struct inet_cork *cork;
1167         int hh_len;
1168         int mtu;
1169         int len;
1170         int err;
1171         unsigned int maxfraglen, fragheaderlen, fraggap, maxnonfragsize;
1172 
1173         if (inet->hdrincl)
1174                 return -EPERM;
1175 
1176         if (flags&MSG_PROBE)
1177                 return 0;
1178 
1179         if (skb_queue_empty(&sk->sk_write_queue))
1180                 return -EINVAL;
1181 
1182         cork = &inet->cork.base;
1183         rt = (struct rtable *)cork->dst;
1184         if (cork->flags & IPCORK_OPT)
1185                 opt = cork->opt;
1186 
1187         if (!(rt->dst.dev->features&NETIF_F_SG))
1188                 return -EOPNOTSUPP;
1189 
1190         hh_len = LL_RESERVED_SPACE(rt->dst.dev);
1191         mtu = cork->fragsize;
1192 
1193         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
1194         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
1195         maxnonfragsize = ip_sk_ignore_df(sk) ? 0xFFFF : mtu;
1196 
1197         if (cork->length + size > maxnonfragsize - fragheaderlen) {
1198                 ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
1199                                mtu - (opt ? opt->optlen : 0));
1200                 return -EMSGSIZE;
1201         }
1202 
1203         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
1204                 return -EINVAL;
1205 
1206         cork->length += size;
1207         if ((size + skb->len > mtu) &&
1208             (sk->sk_protocol == IPPROTO_UDP) &&
1209             (rt->dst.dev->features & NETIF_F_UFO)) {
1210                 skb_shinfo(skb)->gso_size = mtu - fragheaderlen;
1211                 skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
1212         }
1213 
1214 
1215         while (size > 0) {
1216                 int i;
1217 
1218                 if (skb_is_gso(skb))
1219                         len = size;
1220                 else {
1221 
1222                         /* Check if the remaining data fits into current packet. */
1223                         len = mtu - skb->len;
1224                         if (len < size)
1225                                 len = maxfraglen - skb->len;
1226                 }
1227                 if (len <= 0) {
1228                         struct sk_buff *skb_prev;
1229                         int alloclen;
1230 
1231                         skb_prev = skb;
1232                         fraggap = skb_prev->len - maxfraglen;
1233 
1234                         alloclen = fragheaderlen + hh_len + fraggap + 15;
1235                         skb = sock_wmalloc(sk, alloclen, 1, sk->sk_allocation);
1236                         if (unlikely(!skb)) {
1237                                 err = -ENOBUFS;
1238                                 goto error;
1239                         }
1240 
1241                         /*
1242                          *      Fill in the control structures
1243                          */
1244                         skb->ip_summed = CHECKSUM_NONE;
1245                         skb->csum = 0;
1246                         skb_reserve(skb, hh_len);
1247 
1248                         /*
1249                          *      Find where to start putting bytes.
1250                          */
1251                         skb_put(skb, fragheaderlen + fraggap);
1252                         skb_reset_network_header(skb);
1253                         skb->transport_header = (skb->network_header +
1254                                                  fragheaderlen);
1255                         if (fraggap) {
1256                                 skb->csum = skb_copy_and_csum_bits(skb_prev,
1257                                                                    maxfraglen,
1258                                                     skb_transport_header(skb),
1259                                                                    fraggap, 0);
1260                                 skb_prev->csum = csum_sub(skb_prev->csum,
1261                                                           skb->csum);
1262                                 pskb_trim_unique(skb_prev, maxfraglen);
1263                         }
1264 
1265                         /*
1266                          * Put the packet on the pending queue.
1267                          */
1268                         __skb_queue_tail(&sk->sk_write_queue, skb);
1269                         continue;
1270                 }
1271 
1272                 i = skb_shinfo(skb)->nr_frags;
1273                 if (len > size)
1274                         len = size;
1275                 if (skb_can_coalesce(skb, i, page, offset)) {
1276                         skb_frag_size_add(&skb_shinfo(skb)->frags[i-1], len);
1277                 } else if (i < MAX_SKB_FRAGS) {
1278                         get_page(page);
1279                         skb_fill_page_desc(skb, i, page, offset, len);
1280                 } else {
1281                         err = -EMSGSIZE;
1282                         goto error;
1283                 }
1284 
1285                 if (skb->ip_summed == CHECKSUM_NONE) {
1286                         __wsum csum;
1287                         csum = csum_page(page, offset, len);
1288                         skb->csum = csum_block_add(skb->csum, csum, skb->len);
1289                 }
1290 
1291                 skb->len += len;
1292                 skb->data_len += len;
1293                 skb->truesize += len;
1294                 atomic_add(len, &sk->sk_wmem_alloc);
1295                 offset += len;
1296                 size -= len;
1297         }
1298         return 0;
1299 
1300 error:
1301         cork->length -= size;
1302         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1303         return err;
1304 }
1305 
1306 static void ip_cork_release(struct inet_cork *cork)
1307 {
1308         cork->flags &= ~IPCORK_OPT;
1309         kfree(cork->opt);
1310         cork->opt = NULL;
1311         dst_release(cork->dst);
1312         cork->dst = NULL;
1313 }
1314 
1315 /*
1316  *      Combined all pending IP fragments on the socket as one IP datagram
1317  *      and push them out.
1318  */
1319 struct sk_buff *__ip_make_skb(struct sock *sk,
1320                               struct flowi4 *fl4,
1321                               struct sk_buff_head *queue,
1322                               struct inet_cork *cork)
1323 {
1324         struct sk_buff *skb, *tmp_skb;
1325         struct sk_buff **tail_skb;
1326         struct inet_sock *inet = inet_sk(sk);
1327         struct net *net = sock_net(sk);
1328         struct ip_options *opt = NULL;
1329         struct rtable *rt = (struct rtable *)cork->dst;
1330         struct iphdr *iph;
1331         __be16 df = 0;
1332         __u8 ttl;
1333 
1334         if ((skb = __skb_dequeue(queue)) == NULL)
1335                 goto out;
1336         tail_skb = &(skb_shinfo(skb)->frag_list);
1337 
1338         /* move skb->data to ip header from ext header */
1339         if (skb->data < skb_network_header(skb))
1340                 __skb_pull(skb, skb_network_offset(skb));
1341         while ((tmp_skb = __skb_dequeue(queue)) != NULL) {
1342                 __skb_pull(tmp_skb, skb_network_header_len(skb));
1343                 *tail_skb = tmp_skb;
1344                 tail_skb = &(tmp_skb->next);
1345                 skb->len += tmp_skb->len;
1346                 skb->data_len += tmp_skb->len;
1347                 skb->truesize += tmp_skb->truesize;
1348                 tmp_skb->destructor = NULL;
1349                 tmp_skb->sk = NULL;
1350         }
1351 
1352         /* Unless user demanded real pmtu discovery (IP_PMTUDISC_DO), we allow
1353          * to fragment the frame generated here. No matter, what transforms
1354          * how transforms change size of the packet, it will come out.
1355          */
1356         skb->ignore_df = ip_sk_ignore_df(sk);
1357 
1358         /* DF bit is set when we want to see DF on outgoing frames.
1359          * If ignore_df is set too, we still allow to fragment this frame
1360          * locally. */
1361         if (inet->pmtudisc == IP_PMTUDISC_DO ||
1362             inet->pmtudisc == IP_PMTUDISC_PROBE ||
1363             (skb->len <= dst_mtu(&rt->dst) &&
1364              ip_dont_fragment(sk, &rt->dst)))
1365                 df = htons(IP_DF);
1366 
1367         if (cork->flags & IPCORK_OPT)
1368                 opt = cork->opt;
1369 
1370         if (cork->ttl != 0)
1371                 ttl = cork->ttl;
1372         else if (rt->rt_type == RTN_MULTICAST)
1373                 ttl = inet->mc_ttl;
1374         else
1375                 ttl = ip_select_ttl(inet, &rt->dst);
1376 
1377         iph = ip_hdr(skb);
1378         iph->version = 4;
1379         iph->ihl = 5;
1380         iph->tos = (cork->tos != -1) ? cork->tos : inet->tos;
1381         iph->frag_off = df;
1382         iph->ttl = ttl;
1383         iph->protocol = sk->sk_protocol;
1384         ip_copy_addrs(iph, fl4);
1385         ip_select_ident(skb, sk);
1386 
1387         if (opt) {
1388                 iph->ihl += opt->optlen>>2;
1389                 ip_options_build(skb, opt, cork->addr, rt, 0);
1390         }
1391 
1392         skb->priority = (cork->tos != -1) ? cork->priority: sk->sk_priority;
1393         skb->mark = sk->sk_mark;
1394         /*
1395          * Steal rt from cork.dst to avoid a pair of atomic_inc/atomic_dec
1396          * on dst refcount
1397          */
1398         cork->dst = NULL;
1399         skb_dst_set(skb, &rt->dst);
1400 
1401         if (iph->protocol == IPPROTO_ICMP)
1402                 icmp_out_count(net, ((struct icmphdr *)
1403                         skb_transport_header(skb))->type);
1404 
1405         ip_cork_release(cork);
1406 out:
1407         return skb;
1408 }
1409 
1410 int ip_send_skb(struct net *net, struct sk_buff *skb)
1411 {
1412         int err;
1413 
1414         err = ip_local_out(skb);
1415         if (err) {
1416                 if (err > 0)
1417                         err = net_xmit_errno(err);
1418                 if (err)
1419                         IP_INC_STATS(net, IPSTATS_MIB_OUTDISCARDS);
1420         }
1421 
1422         return err;
1423 }
1424 
1425 int ip_push_pending_frames(struct sock *sk, struct flowi4 *fl4)
1426 {
1427         struct sk_buff *skb;
1428 
1429         skb = ip_finish_skb(sk, fl4);
1430         if (!skb)
1431                 return 0;
1432 
1433         /* Netfilter gets whole the not fragmented skb. */
1434         return ip_send_skb(sock_net(sk), skb);
1435 }
1436 
1437 /*
1438  *      Throw away all pending data on the socket.
1439  */
1440 static void __ip_flush_pending_frames(struct sock *sk,
1441                                       struct sk_buff_head *queue,
1442                                       struct inet_cork *cork)
1443 {
1444         struct sk_buff *skb;
1445 
1446         while ((skb = __skb_dequeue_tail(queue)) != NULL)
1447                 kfree_skb(skb);
1448 
1449         ip_cork_release(cork);
1450 }
1451 
1452 void ip_flush_pending_frames(struct sock *sk)
1453 {
1454         __ip_flush_pending_frames(sk, &sk->sk_write_queue, &inet_sk(sk)->cork.base);
1455 }
1456 
1457 struct sk_buff *ip_make_skb(struct sock *sk,
1458                             struct flowi4 *fl4,
1459                             int getfrag(void *from, char *to, int offset,
1460                                         int len, int odd, struct sk_buff *skb),
1461                             void *from, int length, int transhdrlen,
1462                             struct ipcm_cookie *ipc, struct rtable **rtp,
1463                             unsigned int flags)
1464 {
1465         struct inet_cork cork;
1466         struct sk_buff_head queue;
1467         int err;
1468 
1469         if (flags & MSG_PROBE)
1470                 return NULL;
1471 
1472         __skb_queue_head_init(&queue);
1473 
1474         cork.flags = 0;
1475         cork.addr = 0;
1476         cork.opt = NULL;
1477         err = ip_setup_cork(sk, &cork, ipc, rtp);
1478         if (err)
1479                 return ERR_PTR(err);
1480 
1481         err = __ip_append_data(sk, fl4, &queue, &cork,
1482                                &current->task_frag, getfrag,
1483                                from, length, transhdrlen, flags);
1484         if (err) {
1485                 __ip_flush_pending_frames(sk, &queue, &cork);
1486                 return ERR_PTR(err);
1487         }
1488 
1489         return __ip_make_skb(sk, fl4, &queue, &cork);
1490 }
1491 
1492 /*
1493  *      Fetch data from kernel space and fill in checksum if needed.
1494  */
1495 static int ip_reply_glue_bits(void *dptr, char *to, int offset,
1496                               int len, int odd, struct sk_buff *skb)
1497 {
1498         __wsum csum;
1499 
1500         csum = csum_partial_copy_nocheck(dptr+offset, to, len, 0);
1501         skb->csum = csum_block_add(skb->csum, csum, odd);
1502         return 0;
1503 }
1504 
1505 /*
1506  *      Generic function to send a packet as reply to another packet.
1507  *      Used to send some TCP resets/acks so far.
1508  */
1509 void ip_send_unicast_reply(struct sock *sk, struct sk_buff *skb,
1510                            const struct ip_options *sopt,
1511                            __be32 daddr, __be32 saddr,
1512                            const struct ip_reply_arg *arg,
1513                            unsigned int len)
1514 {
1515         struct ip_options_data replyopts;
1516         struct ipcm_cookie ipc;
1517         struct flowi4 fl4;
1518         struct rtable *rt = skb_rtable(skb);
1519         struct net *net = sock_net(sk);
1520         struct sk_buff *nskb;
1521         int err;
1522 
1523         if (__ip_options_echo(&replyopts.opt.opt, skb, sopt))
1524                 return;
1525 
1526         ipc.addr = daddr;
1527         ipc.opt = NULL;
1528         ipc.tx_flags = 0;
1529         ipc.ttl = 0;
1530         ipc.tos = -1;
1531 
1532         if (replyopts.opt.opt.optlen) {
1533                 ipc.opt = &replyopts.opt;
1534 
1535                 if (replyopts.opt.opt.srr)
1536                         daddr = replyopts.opt.opt.faddr;
1537         }
1538 
1539         flowi4_init_output(&fl4, arg->bound_dev_if,
1540                            IP4_REPLY_MARK(net, skb->mark),
1541                            RT_TOS(arg->tos),
1542                            RT_SCOPE_UNIVERSE, ip_hdr(skb)->protocol,
1543                            ip_reply_arg_flowi_flags(arg),
1544                            daddr, saddr,
1545                            tcp_hdr(skb)->source, tcp_hdr(skb)->dest);
1546         security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
1547         rt = ip_route_output_key(net, &fl4);
1548         if (IS_ERR(rt))
1549                 return;
1550 
1551         inet_sk(sk)->tos = arg->tos;
1552 
1553         sk->sk_priority = skb->priority;
1554         sk->sk_protocol = ip_hdr(skb)->protocol;
1555         sk->sk_bound_dev_if = arg->bound_dev_if;
1556         sk->sk_sndbuf = sysctl_wmem_default;
1557         err = ip_append_data(sk, &fl4, ip_reply_glue_bits, arg->iov->iov_base,
1558                              len, 0, &ipc, &rt, MSG_DONTWAIT);
1559         if (unlikely(err)) {
1560                 ip_flush_pending_frames(sk);
1561                 goto out;
1562         }
1563 
1564         nskb = skb_peek(&sk->sk_write_queue);
1565         if (nskb) {
1566                 if (arg->csumoffset >= 0)
1567                         *((__sum16 *)skb_transport_header(nskb) +
1568                           arg->csumoffset) = csum_fold(csum_add(nskb->csum,
1569                                                                 arg->csum));
1570                 nskb->ip_summed = CHECKSUM_NONE;
1571                 skb_set_queue_mapping(nskb, skb_get_queue_mapping(skb));
1572                 ip_push_pending_frames(sk, &fl4);
1573         }
1574 out:
1575         ip_rt_put(rt);
1576 }
1577 
1578 void __init ip_init(void)
1579 {
1580         ip_rt_init();
1581         inet_initpeers();
1582 
1583 #if defined(CONFIG_IP_MULTICAST)
1584         igmp_mc_init();
1585 #endif
1586 }
1587 

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