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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/netlink.h>
 80 #include <linux/tcp.h>
 81 
 82 static int
 83 ip_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
 84             unsigned int mtu,
 85             int (*output)(struct net *, struct sock *, struct sk_buff *));
 86 
 87 /* Generate a checksum for an outgoing IP datagram. */
 88 void ip_send_check(struct iphdr *iph)
 89 {
 90         iph->check = 0;
 91         iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
 92 }
 93 EXPORT_SYMBOL(ip_send_check);
 94 
 95 int __ip_local_out(struct net *net, struct sock *sk, struct sk_buff *skb)
 96 {
 97         struct iphdr *iph = ip_hdr(skb);
 98 
 99         iph->tot_len = htons(skb->len);
100         ip_send_check(iph);
101         return nf_hook(NFPROTO_IPV4, NF_INET_LOCAL_OUT,
102                        net, sk, skb, NULL, skb_dst(skb)->dev,
103                        dst_output);
104 }
105 
106 int ip_local_out(struct net *net, struct sock *sk, struct sk_buff *skb)
107 {
108         int err;
109 
110         err = __ip_local_out(net, sk, skb);
111         if (likely(err == 1))
112                 err = dst_output(net, sk, skb);
113 
114         return err;
115 }
116 EXPORT_SYMBOL_GPL(ip_local_out);
117 
118 static inline int ip_select_ttl(struct inet_sock *inet, struct dst_entry *dst)
119 {
120         int ttl = inet->uc_ttl;
121 
122         if (ttl < 0)
123                 ttl = ip4_dst_hoplimit(dst);
124         return ttl;
125 }
126 
127 /*
128  *              Add an ip header to a skbuff and send it out.
129  *
130  */
131 int ip_build_and_send_pkt(struct sk_buff *skb, const struct sock *sk,
132                           __be32 saddr, __be32 daddr, struct ip_options_rcu *opt)
133 {
134         struct inet_sock *inet = inet_sk(sk);
135         struct rtable *rt = skb_rtable(skb);
136         struct net *net = sock_net(sk);
137         struct iphdr *iph;
138 
139         /* Build the IP header. */
140         skb_push(skb, sizeof(struct iphdr) + (opt ? opt->opt.optlen : 0));
141         skb_reset_network_header(skb);
142         iph = ip_hdr(skb);
143         iph->version  = 4;
144         iph->ihl      = 5;
145         iph->tos      = inet->tos;
146         iph->ttl      = ip_select_ttl(inet, &rt->dst);
147         iph->daddr    = (opt && opt->opt.srr ? opt->opt.faddr : daddr);
148         iph->saddr    = saddr;
149         iph->protocol = sk->sk_protocol;
150         if (ip_dont_fragment(sk, &rt->dst)) {
151                 iph->frag_off = htons(IP_DF);
152                 iph->id = 0;
153         } else {
154                 iph->frag_off = 0;
155                 __ip_select_ident(net, iph, 1);
156         }
157 
158         if (opt && opt->opt.optlen) {
159                 iph->ihl += opt->opt.optlen>>2;
160                 ip_options_build(skb, &opt->opt, daddr, rt, 0);
161         }
162 
163         skb->priority = sk->sk_priority;
164         skb->mark = sk->sk_mark;
165 
166         /* Send it out. */
167         return ip_local_out(net, skb->sk, skb);
168 }
169 EXPORT_SYMBOL_GPL(ip_build_and_send_pkt);
170 
171 static int ip_finish_output2(struct net *net, struct sock *sk, struct sk_buff *skb)
172 {
173         struct dst_entry *dst = skb_dst(skb);
174         struct rtable *rt = (struct rtable *)dst;
175         struct net_device *dev = dst->dev;
176         unsigned int hh_len = LL_RESERVED_SPACE(dev);
177         struct neighbour *neigh;
178         u32 nexthop;
179 
180         if (rt->rt_type == RTN_MULTICAST) {
181                 IP_UPD_PO_STATS(net, IPSTATS_MIB_OUTMCAST, skb->len);
182         } else if (rt->rt_type == RTN_BROADCAST)
183                 IP_UPD_PO_STATS(net, IPSTATS_MIB_OUTBCAST, skb->len);
184 
185         /* Be paranoid, rather than too clever. */
186         if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) {
187                 struct sk_buff *skb2;
188 
189                 skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev));
190                 if (!skb2) {
191                         kfree_skb(skb);
192                         return -ENOMEM;
193                 }
194                 if (skb->sk)
195                         skb_set_owner_w(skb2, skb->sk);
196                 consume_skb(skb);
197                 skb = skb2;
198         }
199 
200         rcu_read_lock_bh();
201         nexthop = (__force u32) rt_nexthop(rt, ip_hdr(skb)->daddr);
202         neigh = __ipv4_neigh_lookup_noref(dev, nexthop);
203         if (unlikely(!neigh))
204                 neigh = __neigh_create(&arp_tbl, &nexthop, dev, false);
205         if (!IS_ERR(neigh)) {
206                 int res = dst_neigh_output(dst, neigh, skb);
207 
208                 rcu_read_unlock_bh();
209                 return res;
210         }
211         rcu_read_unlock_bh();
212 
213         net_dbg_ratelimited("%s: No header cache and no neighbour!\n",
214                             __func__);
215         kfree_skb(skb);
216         return -EINVAL;
217 }
218 
219 static int ip_finish_output_gso(struct net *net, struct sock *sk,
220                                 struct sk_buff *skb, unsigned int mtu)
221 {
222         netdev_features_t features;
223         struct sk_buff *segs;
224         int ret = 0;
225 
226         /* common case: locally created skb or seglen is <= mtu */
227         if (((IPCB(skb)->flags & IPSKB_FORWARDED) == 0) ||
228               skb_gso_network_seglen(skb) <= mtu)
229                 return ip_finish_output2(net, sk, skb);
230 
231         /* Slowpath -  GSO segment length is exceeding the dst MTU.
232          *
233          * This can happen in two cases:
234          * 1) TCP GRO packet, DF bit not set
235          * 2) skb arrived via virtio-net, we thus get TSO/GSO skbs directly
236          * from host network stack.
237          */
238         features = netif_skb_features(skb);
239         BUILD_BUG_ON(sizeof(*IPCB(skb)) > SKB_SGO_CB_OFFSET);
240         segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK);
241         if (IS_ERR_OR_NULL(segs)) {
242                 kfree_skb(skb);
243                 return -ENOMEM;
244         }
245 
246         consume_skb(skb);
247 
248         do {
249                 struct sk_buff *nskb = segs->next;
250                 int err;
251 
252                 segs->next = NULL;
253                 err = ip_fragment(net, sk, segs, mtu, ip_finish_output2);
254 
255                 if (err && ret == 0)
256                         ret = err;
257                 segs = nskb;
258         } while (segs);
259 
260         return ret;
261 }
262 
263 static int ip_finish_output(struct net *net, struct sock *sk, struct sk_buff *skb)
264 {
265         unsigned int mtu;
266 
267 #if defined(CONFIG_NETFILTER) && defined(CONFIG_XFRM)
268         /* Policy lookup after SNAT yielded a new policy */
269         if (skb_dst(skb)->xfrm) {
270                 IPCB(skb)->flags |= IPSKB_REROUTED;
271                 return dst_output(net, sk, skb);
272         }
273 #endif
274         mtu = ip_skb_dst_mtu(sk, skb);
275         if (skb_is_gso(skb))
276                 return ip_finish_output_gso(net, sk, skb, mtu);
277 
278         if (skb->len > mtu || (IPCB(skb)->flags & IPSKB_FRAG_PMTU))
279                 return ip_fragment(net, sk, skb, mtu, ip_finish_output2);
280 
281         return ip_finish_output2(net, sk, skb);
282 }
283 
284 int ip_mc_output(struct net *net, struct sock *sk, struct sk_buff *skb)
285 {
286         struct rtable *rt = skb_rtable(skb);
287         struct net_device *dev = rt->dst.dev;
288 
289         /*
290          *      If the indicated interface is up and running, send the packet.
291          */
292         IP_UPD_PO_STATS(net, IPSTATS_MIB_OUT, skb->len);
293 
294         skb->dev = dev;
295         skb->protocol = htons(ETH_P_IP);
296 
297         /*
298          *      Multicasts are looped back for other local users
299          */
300 
301         if (rt->rt_flags&RTCF_MULTICAST) {
302                 if (sk_mc_loop(sk)
303 #ifdef CONFIG_IP_MROUTE
304                 /* Small optimization: do not loopback not local frames,
305                    which returned after forwarding; they will be  dropped
306                    by ip_mr_input in any case.
307                    Note, that local frames are looped back to be delivered
308                    to local recipients.
309 
310                    This check is duplicated in ip_mr_input at the moment.
311                  */
312                     &&
313                     ((rt->rt_flags & RTCF_LOCAL) ||
314                      !(IPCB(skb)->flags & IPSKB_FORWARDED))
315 #endif
316                    ) {
317                         struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
318                         if (newskb)
319                                 NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING,
320                                         net, sk, newskb, NULL, newskb->dev,
321                                         dev_loopback_xmit);
322                 }
323 
324                 /* Multicasts with ttl 0 must not go beyond the host */
325 
326                 if (ip_hdr(skb)->ttl == 0) {
327                         kfree_skb(skb);
328                         return 0;
329                 }
330         }
331 
332         if (rt->rt_flags&RTCF_BROADCAST) {
333                 struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
334                 if (newskb)
335                         NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING,
336                                 net, sk, newskb, NULL, newskb->dev,
337                                 dev_loopback_xmit);
338         }
339 
340         return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
341                             net, sk, skb, NULL, skb->dev,
342                             ip_finish_output,
343                             !(IPCB(skb)->flags & IPSKB_REROUTED));
344 }
345 
346 int ip_output(struct net *net, struct sock *sk, struct sk_buff *skb)
347 {
348         struct net_device *dev = skb_dst(skb)->dev;
349 
350         IP_UPD_PO_STATS(net, IPSTATS_MIB_OUT, skb->len);
351 
352         skb->dev = dev;
353         skb->protocol = htons(ETH_P_IP);
354 
355         return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
356                             net, sk, skb, NULL, dev,
357                             ip_finish_output,
358                             !(IPCB(skb)->flags & IPSKB_REROUTED));
359 }
360 
361 /*
362  * copy saddr and daddr, possibly using 64bit load/stores
363  * Equivalent to :
364  *   iph->saddr = fl4->saddr;
365  *   iph->daddr = fl4->daddr;
366  */
367 static void ip_copy_addrs(struct iphdr *iph, const struct flowi4 *fl4)
368 {
369         BUILD_BUG_ON(offsetof(typeof(*fl4), daddr) !=
370                      offsetof(typeof(*fl4), saddr) + sizeof(fl4->saddr));
371         memcpy(&iph->saddr, &fl4->saddr,
372                sizeof(fl4->saddr) + sizeof(fl4->daddr));
373 }
374 
375 /* Note: skb->sk can be different from sk, in case of tunnels */
376 int ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl)
377 {
378         struct inet_sock *inet = inet_sk(sk);
379         struct net *net = sock_net(sk);
380         struct ip_options_rcu *inet_opt;
381         struct flowi4 *fl4;
382         struct rtable *rt;
383         struct iphdr *iph;
384         int res;
385 
386         /* Skip all of this if the packet is already routed,
387          * f.e. by something like SCTP.
388          */
389         rcu_read_lock();
390         inet_opt = rcu_dereference(inet->inet_opt);
391         fl4 = &fl->u.ip4;
392         rt = skb_rtable(skb);
393         if (rt)
394                 goto packet_routed;
395 
396         /* Make sure we can route this packet. */
397         rt = (struct rtable *)__sk_dst_check(sk, 0);
398         if (!rt) {
399                 __be32 daddr;
400 
401                 /* Use correct destination address if we have options. */
402                 daddr = inet->inet_daddr;
403                 if (inet_opt && inet_opt->opt.srr)
404                         daddr = inet_opt->opt.faddr;
405 
406                 /* If this fails, retransmit mechanism of transport layer will
407                  * keep trying until route appears or the connection times
408                  * itself out.
409                  */
410                 rt = ip_route_output_ports(net, fl4, sk,
411                                            daddr, inet->inet_saddr,
412                                            inet->inet_dport,
413                                            inet->inet_sport,
414                                            sk->sk_protocol,
415                                            RT_CONN_FLAGS(sk),
416                                            sk->sk_bound_dev_if);
417                 if (IS_ERR(rt))
418                         goto no_route;
419                 sk_setup_caps(sk, &rt->dst);
420         }
421         skb_dst_set_noref(skb, &rt->dst);
422 
423 packet_routed:
424         if (inet_opt && inet_opt->opt.is_strictroute && rt->rt_uses_gateway)
425                 goto no_route;
426 
427         /* OK, we know where to send it, allocate and build IP header. */
428         skb_push(skb, sizeof(struct iphdr) + (inet_opt ? inet_opt->opt.optlen : 0));
429         skb_reset_network_header(skb);
430         iph = ip_hdr(skb);
431         *((__be16 *)iph) = htons((4 << 12) | (5 << 8) | (inet->tos & 0xff));
432         if (ip_dont_fragment(sk, &rt->dst) && !skb->ignore_df)
433                 iph->frag_off = htons(IP_DF);
434         else
435                 iph->frag_off = 0;
436         iph->ttl      = ip_select_ttl(inet, &rt->dst);
437         iph->protocol = sk->sk_protocol;
438         ip_copy_addrs(iph, fl4);
439 
440         /* Transport layer set skb->h.foo itself. */
441 
442         if (inet_opt && inet_opt->opt.optlen) {
443                 iph->ihl += inet_opt->opt.optlen >> 2;
444                 ip_options_build(skb, &inet_opt->opt, inet->inet_daddr, rt, 0);
445         }
446 
447         ip_select_ident_segs(net, skb, sk,
448                              skb_shinfo(skb)->gso_segs ?: 1);
449 
450         /* TODO : should we use skb->sk here instead of sk ? */
451         skb->priority = sk->sk_priority;
452         skb->mark = sk->sk_mark;
453 
454         res = ip_local_out(net, sk, skb);
455         rcu_read_unlock();
456         return res;
457 
458 no_route:
459         rcu_read_unlock();
460         IP_INC_STATS(net, IPSTATS_MIB_OUTNOROUTES);
461         kfree_skb(skb);
462         return -EHOSTUNREACH;
463 }
464 EXPORT_SYMBOL(ip_queue_xmit);
465 
466 static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
467 {
468         to->pkt_type = from->pkt_type;
469         to->priority = from->priority;
470         to->protocol = from->protocol;
471         skb_dst_drop(to);
472         skb_dst_copy(to, from);
473         to->dev = from->dev;
474         to->mark = from->mark;
475 
476         /* Copy the flags to each fragment. */
477         IPCB(to)->flags = IPCB(from)->flags;
478 
479 #ifdef CONFIG_NET_SCHED
480         to->tc_index = from->tc_index;
481 #endif
482         nf_copy(to, from);
483 #if defined(CONFIG_IP_VS) || defined(CONFIG_IP_VS_MODULE)
484         to->ipvs_property = from->ipvs_property;
485 #endif
486         skb_copy_secmark(to, from);
487 }
488 
489 static int ip_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
490                        unsigned int mtu,
491                        int (*output)(struct net *, struct sock *, struct sk_buff *))
492 {
493         struct iphdr *iph = ip_hdr(skb);
494 
495         if ((iph->frag_off & htons(IP_DF)) == 0)
496                 return ip_do_fragment(net, sk, skb, output);
497 
498         if (unlikely(!skb->ignore_df ||
499                      (IPCB(skb)->frag_max_size &&
500                       IPCB(skb)->frag_max_size > mtu))) {
501                 IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
502                 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
503                           htonl(mtu));
504                 kfree_skb(skb);
505                 return -EMSGSIZE;
506         }
507 
508         return ip_do_fragment(net, sk, skb, output);
509 }
510 
511 /*
512  *      This IP datagram is too large to be sent in one piece.  Break it up into
513  *      smaller pieces (each of size equal to IP header plus
514  *      a block of the data of the original IP data part) that will yet fit in a
515  *      single device frame, and queue such a frame for sending.
516  */
517 
518 int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
519                    int (*output)(struct net *, struct sock *, struct sk_buff *))
520 {
521         struct iphdr *iph;
522         int ptr;
523         struct net_device *dev;
524         struct sk_buff *skb2;
525         unsigned int mtu, hlen, left, len, ll_rs;
526         int offset;
527         __be16 not_last_frag;
528         struct rtable *rt = skb_rtable(skb);
529         int err = 0;
530 
531         dev = rt->dst.dev;
532 
533         /* for offloaded checksums cleanup checksum before fragmentation */
534         if (skb->ip_summed == CHECKSUM_PARTIAL &&
535             (err = skb_checksum_help(skb)))
536                 goto fail;
537 
538         /*
539          *      Point into the IP datagram header.
540          */
541 
542         iph = ip_hdr(skb);
543 
544         mtu = ip_skb_dst_mtu(sk, skb);
545         if (IPCB(skb)->frag_max_size && IPCB(skb)->frag_max_size < mtu)
546                 mtu = IPCB(skb)->frag_max_size;
547 
548         /*
549          *      Setup starting values.
550          */
551 
552         hlen = iph->ihl * 4;
553         mtu = mtu - hlen;       /* Size of data space */
554         IPCB(skb)->flags |= IPSKB_FRAG_COMPLETE;
555 
556         /* When frag_list is given, use it. First, check its validity:
557          * some transformers could create wrong frag_list or break existing
558          * one, it is not prohibited. In this case fall back to copying.
559          *
560          * LATER: this step can be merged to real generation of fragments,
561          * we can switch to copy when see the first bad fragment.
562          */
563         if (skb_has_frag_list(skb)) {
564                 struct sk_buff *frag, *frag2;
565                 int first_len = skb_pagelen(skb);
566 
567                 if (first_len - hlen > mtu ||
568                     ((first_len - hlen) & 7) ||
569                     ip_is_fragment(iph) ||
570                     skb_cloned(skb))
571                         goto slow_path;
572 
573                 skb_walk_frags(skb, frag) {
574                         /* Correct geometry. */
575                         if (frag->len > mtu ||
576                             ((frag->len & 7) && frag->next) ||
577                             skb_headroom(frag) < hlen)
578                                 goto slow_path_clean;
579 
580                         /* Partially cloned skb? */
581                         if (skb_shared(frag))
582                                 goto slow_path_clean;
583 
584                         BUG_ON(frag->sk);
585                         if (skb->sk) {
586                                 frag->sk = skb->sk;
587                                 frag->destructor = sock_wfree;
588                         }
589                         skb->truesize -= frag->truesize;
590                 }
591 
592                 /* Everything is OK. Generate! */
593 
594                 err = 0;
595                 offset = 0;
596                 frag = skb_shinfo(skb)->frag_list;
597                 skb_frag_list_init(skb);
598                 skb->data_len = first_len - skb_headlen(skb);
599                 skb->len = first_len;
600                 iph->tot_len = htons(first_len);
601                 iph->frag_off = htons(IP_MF);
602                 ip_send_check(iph);
603 
604                 for (;;) {
605                         /* Prepare header of the next frame,
606                          * before previous one went down. */
607                         if (frag) {
608                                 frag->ip_summed = CHECKSUM_NONE;
609                                 skb_reset_transport_header(frag);
610                                 __skb_push(frag, hlen);
611                                 skb_reset_network_header(frag);
612                                 memcpy(skb_network_header(frag), iph, hlen);
613                                 iph = ip_hdr(frag);
614                                 iph->tot_len = htons(frag->len);
615                                 ip_copy_metadata(frag, skb);
616                                 if (offset == 0)
617                                         ip_options_fragment(frag);
618                                 offset += skb->len - hlen;
619                                 iph->frag_off = htons(offset>>3);
620                                 if (frag->next)
621                                         iph->frag_off |= htons(IP_MF);
622                                 /* Ready, complete checksum */
623                                 ip_send_check(iph);
624                         }
625 
626                         err = output(net, sk, skb);
627 
628                         if (!err)
629                                 IP_INC_STATS(net, IPSTATS_MIB_FRAGCREATES);
630                         if (err || !frag)
631                                 break;
632 
633                         skb = frag;
634                         frag = skb->next;
635                         skb->next = NULL;
636                 }
637 
638                 if (err == 0) {
639                         IP_INC_STATS(net, IPSTATS_MIB_FRAGOKS);
640                         return 0;
641                 }
642 
643                 while (frag) {
644                         skb = frag->next;
645                         kfree_skb(frag);
646                         frag = skb;
647                 }
648                 IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
649                 return err;
650 
651 slow_path_clean:
652                 skb_walk_frags(skb, frag2) {
653                         if (frag2 == frag)
654                                 break;
655                         frag2->sk = NULL;
656                         frag2->destructor = NULL;
657                         skb->truesize += frag2->truesize;
658                 }
659         }
660 
661 slow_path:
662         iph = ip_hdr(skb);
663 
664         left = skb->len - hlen;         /* Space per frame */
665         ptr = hlen;             /* Where to start from */
666 
667         ll_rs = LL_RESERVED_SPACE(rt->dst.dev);
668 
669         /*
670          *      Fragment the datagram.
671          */
672 
673         offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3;
674         not_last_frag = iph->frag_off & htons(IP_MF);
675 
676         /*
677          *      Keep copying data until we run out.
678          */
679 
680         while (left > 0) {
681                 len = left;
682                 /* IF: it doesn't fit, use 'mtu' - the data space left */
683                 if (len > mtu)
684                         len = mtu;
685                 /* IF: we are not sending up to and including the packet end
686                    then align the next start on an eight byte boundary */
687                 if (len < left) {
688                         len &= ~7;
689                 }
690 
691                 /* Allocate buffer */
692                 skb2 = alloc_skb(len + hlen + ll_rs, GFP_ATOMIC);
693                 if (!skb2) {
694                         err = -ENOMEM;
695                         goto fail;
696                 }
697 
698                 /*
699                  *      Set up data on packet
700                  */
701 
702                 ip_copy_metadata(skb2, skb);
703                 skb_reserve(skb2, ll_rs);
704                 skb_put(skb2, len + hlen);
705                 skb_reset_network_header(skb2);
706                 skb2->transport_header = skb2->network_header + hlen;
707 
708                 /*
709                  *      Charge the memory for the fragment to any owner
710                  *      it might possess
711                  */
712 
713                 if (skb->sk)
714                         skb_set_owner_w(skb2, skb->sk);
715 
716                 /*
717                  *      Copy the packet header into the new buffer.
718                  */
719 
720                 skb_copy_from_linear_data(skb, skb_network_header(skb2), hlen);
721 
722                 /*
723                  *      Copy a block of the IP datagram.
724                  */
725                 if (skb_copy_bits(skb, ptr, skb_transport_header(skb2), len))
726                         BUG();
727                 left -= len;
728 
729                 /*
730                  *      Fill in the new header fields.
731                  */
732                 iph = ip_hdr(skb2);
733                 iph->frag_off = htons((offset >> 3));
734 
735                 if (IPCB(skb)->flags & IPSKB_FRAG_PMTU)
736                         iph->frag_off |= htons(IP_DF);
737 
738                 /* ANK: dirty, but effective trick. Upgrade options only if
739                  * the segment to be fragmented was THE FIRST (otherwise,
740                  * options are already fixed) and make it ONCE
741                  * on the initial skb, so that all the following fragments
742                  * will inherit fixed options.
743                  */
744                 if (offset == 0)
745                         ip_options_fragment(skb);
746 
747                 /*
748                  *      Added AC : If we are fragmenting a fragment that's not the
749                  *                 last fragment then keep MF on each bit
750                  */
751                 if (left > 0 || not_last_frag)
752                         iph->frag_off |= htons(IP_MF);
753                 ptr += len;
754                 offset += len;
755 
756                 /*
757                  *      Put this fragment into the sending queue.
758                  */
759                 iph->tot_len = htons(len + hlen);
760 
761                 ip_send_check(iph);
762 
763                 err = output(net, sk, skb2);
764                 if (err)
765                         goto fail;
766 
767                 IP_INC_STATS(net, IPSTATS_MIB_FRAGCREATES);
768         }
769         consume_skb(skb);
770         IP_INC_STATS(net, IPSTATS_MIB_FRAGOKS);
771         return err;
772 
773 fail:
774         kfree_skb(skb);
775         IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
776         return err;
777 }
778 EXPORT_SYMBOL(ip_do_fragment);
779 
780 int
781 ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
782 {
783         struct msghdr *msg = from;
784 
785         if (skb->ip_summed == CHECKSUM_PARTIAL) {
786                 if (copy_from_iter(to, len, &msg->msg_iter) != len)
787                         return -EFAULT;
788         } else {
789                 __wsum csum = 0;
790                 if (csum_and_copy_from_iter(to, len, &csum, &msg->msg_iter) != len)
791                         return -EFAULT;
792                 skb->csum = csum_block_add(skb->csum, csum, odd);
793         }
794         return 0;
795 }
796 EXPORT_SYMBOL(ip_generic_getfrag);
797 
798 static inline __wsum
799 csum_page(struct page *page, int offset, int copy)
800 {
801         char *kaddr;
802         __wsum csum;
803         kaddr = kmap(page);
804         csum = csum_partial(kaddr + offset, copy, 0);
805         kunmap(page);
806         return csum;
807 }
808 
809 static inline int ip_ufo_append_data(struct sock *sk,
810                         struct sk_buff_head *queue,
811                         int getfrag(void *from, char *to, int offset, int len,
812                                int odd, struct sk_buff *skb),
813                         void *from, int length, int hh_len, int fragheaderlen,
814                         int transhdrlen, int maxfraglen, unsigned int flags)
815 {
816         struct sk_buff *skb;
817         int err;
818 
819         /* There is support for UDP fragmentation offload by network
820          * device, so create one single skb packet containing complete
821          * udp datagram
822          */
823         skb = skb_peek_tail(queue);
824         if (!skb) {
825                 skb = sock_alloc_send_skb(sk,
826                         hh_len + fragheaderlen + transhdrlen + 20,
827                         (flags & MSG_DONTWAIT), &err);
828 
829                 if (!skb)
830                         return err;
831 
832                 /* reserve space for Hardware header */
833                 skb_reserve(skb, hh_len);
834 
835                 /* create space for UDP/IP header */
836                 skb_put(skb, fragheaderlen + transhdrlen);
837 
838                 /* initialize network header pointer */
839                 skb_reset_network_header(skb);
840 
841                 /* initialize protocol header pointer */
842                 skb->transport_header = skb->network_header + fragheaderlen;
843 
844                 skb->csum = 0;
845 
846                 __skb_queue_tail(queue, skb);
847         } else if (skb_is_gso(skb)) {
848                 goto append;
849         }
850 
851         skb->ip_summed = CHECKSUM_PARTIAL;
852         /* specify the length of each IP datagram fragment */
853         skb_shinfo(skb)->gso_size = maxfraglen - fragheaderlen;
854         skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
855 
856 append:
857         return skb_append_datato_frags(sk, skb, getfrag, from,
858                                        (length - transhdrlen));
859 }
860 
861 static int __ip_append_data(struct sock *sk,
862                             struct flowi4 *fl4,
863                             struct sk_buff_head *queue,
864                             struct inet_cork *cork,
865                             struct page_frag *pfrag,
866                             int getfrag(void *from, char *to, int offset,
867                                         int len, int odd, struct sk_buff *skb),
868                             void *from, int length, int transhdrlen,
869                             unsigned int flags)
870 {
871         struct inet_sock *inet = inet_sk(sk);
872         struct sk_buff *skb;
873 
874         struct ip_options *opt = cork->opt;
875         int hh_len;
876         int exthdrlen;
877         int mtu;
878         int copy;
879         int err;
880         int offset = 0;
881         unsigned int maxfraglen, fragheaderlen, maxnonfragsize;
882         int csummode = CHECKSUM_NONE;
883         struct rtable *rt = (struct rtable *)cork->dst;
884         u32 tskey = 0;
885 
886         skb = skb_peek_tail(queue);
887 
888         exthdrlen = !skb ? rt->dst.header_len : 0;
889         mtu = cork->fragsize;
890         if (cork->tx_flags & SKBTX_ANY_SW_TSTAMP &&
891             sk->sk_tsflags & SOF_TIMESTAMPING_OPT_ID)
892                 tskey = sk->sk_tskey++;
893 
894         hh_len = LL_RESERVED_SPACE(rt->dst.dev);
895 
896         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
897         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
898         maxnonfragsize = ip_sk_ignore_df(sk) ? 0xFFFF : mtu;
899 
900         if (cork->length + length > maxnonfragsize - fragheaderlen) {
901                 ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
902                                mtu - (opt ? opt->optlen : 0));
903                 return -EMSGSIZE;
904         }
905 
906         /*
907          * transhdrlen > 0 means that this is the first fragment and we wish
908          * it won't be fragmented in the future.
909          */
910         if (transhdrlen &&
911             length + fragheaderlen <= mtu &&
912             rt->dst.dev->features & (NETIF_F_HW_CSUM | NETIF_F_IP_CSUM) &&
913             !(flags & MSG_MORE) &&
914             !exthdrlen)
915                 csummode = CHECKSUM_PARTIAL;
916 
917         cork->length += length;
918         if (((length > mtu) || (skb && skb_is_gso(skb))) &&
919             (sk->sk_protocol == IPPROTO_UDP) &&
920             (rt->dst.dev->features & NETIF_F_UFO) && !rt->dst.header_len &&
921             (sk->sk_type == SOCK_DGRAM) && !sk->sk_no_check_tx) {
922                 err = ip_ufo_append_data(sk, queue, getfrag, from, length,
923                                          hh_len, fragheaderlen, transhdrlen,
924                                          maxfraglen, flags);
925                 if (err)
926                         goto error;
927                 return 0;
928         }
929 
930         /* So, what's going on in the loop below?
931          *
932          * We use calculated fragment length to generate chained skb,
933          * each of segments is IP fragment ready for sending to network after
934          * adding appropriate IP header.
935          */
936 
937         if (!skb)
938                 goto alloc_new_skb;
939 
940         while (length > 0) {
941                 /* Check if the remaining data fits into current packet. */
942                 copy = mtu - skb->len;
943                 if (copy < length)
944                         copy = maxfraglen - skb->len;
945                 if (copy <= 0) {
946                         char *data;
947                         unsigned int datalen;
948                         unsigned int fraglen;
949                         unsigned int fraggap;
950                         unsigned int alloclen;
951                         struct sk_buff *skb_prev;
952 alloc_new_skb:
953                         skb_prev = skb;
954                         if (skb_prev)
955                                 fraggap = skb_prev->len - maxfraglen;
956                         else
957                                 fraggap = 0;
958 
959                         /*
960                          * If remaining data exceeds the mtu,
961                          * we know we need more fragment(s).
962                          */
963                         datalen = length + fraggap;
964                         if (datalen > mtu - fragheaderlen)
965                                 datalen = maxfraglen - fragheaderlen;
966                         fraglen = datalen + fragheaderlen;
967 
968                         if ((flags & MSG_MORE) &&
969                             !(rt->dst.dev->features&NETIF_F_SG))
970                                 alloclen = mtu;
971                         else
972                                 alloclen = fraglen;
973 
974                         alloclen += exthdrlen;
975 
976                         /* The last fragment gets additional space at tail.
977                          * Note, with MSG_MORE we overallocate on fragments,
978                          * because we have no idea what fragment will be
979                          * the last.
980                          */
981                         if (datalen == length + fraggap)
982                                 alloclen += rt->dst.trailer_len;
983 
984                         if (transhdrlen) {
985                                 skb = sock_alloc_send_skb(sk,
986                                                 alloclen + hh_len + 15,
987                                                 (flags & MSG_DONTWAIT), &err);
988                         } else {
989                                 skb = NULL;
990                                 if (atomic_read(&sk->sk_wmem_alloc) <=
991                                     2 * sk->sk_sndbuf)
992                                         skb = sock_wmalloc(sk,
993                                                            alloclen + hh_len + 15, 1,
994                                                            sk->sk_allocation);
995                                 if (unlikely(!skb))
996                                         err = -ENOBUFS;
997                         }
998                         if (!skb)
999                                 goto error;
1000 
1001                         /*
1002                          *      Fill in the control structures
1003                          */
1004                         skb->ip_summed = csummode;
1005                         skb->csum = 0;
1006                         skb_reserve(skb, hh_len);
1007 
1008                         /* only the initial fragment is time stamped */
1009                         skb_shinfo(skb)->tx_flags = cork->tx_flags;
1010                         cork->tx_flags = 0;
1011                         skb_shinfo(skb)->tskey = tskey;
1012                         tskey = 0;
1013 
1014                         /*
1015                          *      Find where to start putting bytes.
1016                          */
1017                         data = skb_put(skb, fraglen + exthdrlen);
1018                         skb_set_network_header(skb, exthdrlen);
1019                         skb->transport_header = (skb->network_header +
1020                                                  fragheaderlen);
1021                         data += fragheaderlen + exthdrlen;
1022 
1023                         if (fraggap) {
1024                                 skb->csum = skb_copy_and_csum_bits(
1025                                         skb_prev, maxfraglen,
1026                                         data + transhdrlen, fraggap, 0);
1027                                 skb_prev->csum = csum_sub(skb_prev->csum,
1028                                                           skb->csum);
1029                                 data += fraggap;
1030                                 pskb_trim_unique(skb_prev, maxfraglen);
1031                         }
1032 
1033                         copy = datalen - transhdrlen - fraggap;
1034                         if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
1035                                 err = -EFAULT;
1036                                 kfree_skb(skb);
1037                                 goto error;
1038                         }
1039 
1040                         offset += copy;
1041                         length -= datalen - fraggap;
1042                         transhdrlen = 0;
1043                         exthdrlen = 0;
1044                         csummode = CHECKSUM_NONE;
1045 
1046                         /*
1047                          * Put the packet on the pending queue.
1048                          */
1049                         __skb_queue_tail(queue, skb);
1050                         continue;
1051                 }
1052 
1053                 if (copy > length)
1054                         copy = length;
1055 
1056                 if (!(rt->dst.dev->features&NETIF_F_SG)) {
1057                         unsigned int off;
1058 
1059                         off = skb->len;
1060                         if (getfrag(from, skb_put(skb, copy),
1061                                         offset, copy, off, skb) < 0) {
1062                                 __skb_trim(skb, off);
1063                                 err = -EFAULT;
1064                                 goto error;
1065                         }
1066                 } else {
1067                         int i = skb_shinfo(skb)->nr_frags;
1068 
1069                         err = -ENOMEM;
1070                         if (!sk_page_frag_refill(sk, pfrag))
1071                                 goto error;
1072 
1073                         if (!skb_can_coalesce(skb, i, pfrag->page,
1074                                               pfrag->offset)) {
1075                                 err = -EMSGSIZE;
1076                                 if (i == MAX_SKB_FRAGS)
1077                                         goto error;
1078 
1079                                 __skb_fill_page_desc(skb, i, pfrag->page,
1080                                                      pfrag->offset, 0);
1081                                 skb_shinfo(skb)->nr_frags = ++i;
1082                                 get_page(pfrag->page);
1083                         }
1084                         copy = min_t(int, copy, pfrag->size - pfrag->offset);
1085                         if (getfrag(from,
1086                                     page_address(pfrag->page) + pfrag->offset,
1087                                     offset, copy, skb->len, skb) < 0)
1088                                 goto error_efault;
1089 
1090                         pfrag->offset += copy;
1091                         skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
1092                         skb->len += copy;
1093                         skb->data_len += copy;
1094                         skb->truesize += copy;
1095                         atomic_add(copy, &sk->sk_wmem_alloc);
1096                 }
1097                 offset += copy;
1098                 length -= copy;
1099         }
1100 
1101         return 0;
1102 
1103 error_efault:
1104         err = -EFAULT;
1105 error:
1106         cork->length -= length;
1107         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1108         return err;
1109 }
1110 
1111 static int ip_setup_cork(struct sock *sk, struct inet_cork *cork,
1112                          struct ipcm_cookie *ipc, struct rtable **rtp)
1113 {
1114         struct ip_options_rcu *opt;
1115         struct rtable *rt;
1116 
1117         /*
1118          * setup for corking.
1119          */
1120         opt = ipc->opt;
1121         if (opt) {
1122                 if (!cork->opt) {
1123                         cork->opt = kmalloc(sizeof(struct ip_options) + 40,
1124                                             sk->sk_allocation);
1125                         if (unlikely(!cork->opt))
1126                                 return -ENOBUFS;
1127                 }
1128                 memcpy(cork->opt, &opt->opt, sizeof(struct ip_options) + opt->opt.optlen);
1129                 cork->flags |= IPCORK_OPT;
1130                 cork->addr = ipc->addr;
1131         }
1132         rt = *rtp;
1133         if (unlikely(!rt))
1134                 return -EFAULT;
1135         /*
1136          * We steal reference to this route, caller should not release it
1137          */
1138         *rtp = NULL;
1139         cork->fragsize = ip_sk_use_pmtu(sk) ?
1140                          dst_mtu(&rt->dst) : rt->dst.dev->mtu;
1141         cork->dst = &rt->dst;
1142         cork->length = 0;
1143         cork->ttl = ipc->ttl;
1144         cork->tos = ipc->tos;
1145         cork->priority = ipc->priority;
1146         cork->tx_flags = ipc->tx_flags;
1147 
1148         return 0;
1149 }
1150 
1151 /*
1152  *      ip_append_data() and ip_append_page() can make one large IP datagram
1153  *      from many pieces of data. Each pieces will be holded on the socket
1154  *      until ip_push_pending_frames() is called. Each piece can be a page
1155  *      or non-page data.
1156  *
1157  *      Not only UDP, other transport protocols - e.g. raw sockets - can use
1158  *      this interface potentially.
1159  *
1160  *      LATER: length must be adjusted by pad at tail, when it is required.
1161  */
1162 int ip_append_data(struct sock *sk, struct flowi4 *fl4,
1163                    int getfrag(void *from, char *to, int offset, int len,
1164                                int odd, struct sk_buff *skb),
1165                    void *from, int length, int transhdrlen,
1166                    struct ipcm_cookie *ipc, struct rtable **rtp,
1167                    unsigned int flags)
1168 {
1169         struct inet_sock *inet = inet_sk(sk);
1170         int err;
1171 
1172         if (flags&MSG_PROBE)
1173                 return 0;
1174 
1175         if (skb_queue_empty(&sk->sk_write_queue)) {
1176                 err = ip_setup_cork(sk, &inet->cork.base, ipc, rtp);
1177                 if (err)
1178                         return err;
1179         } else {
1180                 transhdrlen = 0;
1181         }
1182 
1183         return __ip_append_data(sk, fl4, &sk->sk_write_queue, &inet->cork.base,
1184                                 sk_page_frag(sk), getfrag,
1185                                 from, length, transhdrlen, flags);
1186 }
1187 
1188 ssize_t ip_append_page(struct sock *sk, struct flowi4 *fl4, struct page *page,
1189                        int offset, size_t size, int flags)
1190 {
1191         struct inet_sock *inet = inet_sk(sk);
1192         struct sk_buff *skb;
1193         struct rtable *rt;
1194         struct ip_options *opt = NULL;
1195         struct inet_cork *cork;
1196         int hh_len;
1197         int mtu;
1198         int len;
1199         int err;
1200         unsigned int maxfraglen, fragheaderlen, fraggap, maxnonfragsize;
1201 
1202         if (inet->hdrincl)
1203                 return -EPERM;
1204 
1205         if (flags&MSG_PROBE)
1206                 return 0;
1207 
1208         if (skb_queue_empty(&sk->sk_write_queue))
1209                 return -EINVAL;
1210 
1211         cork = &inet->cork.base;
1212         rt = (struct rtable *)cork->dst;
1213         if (cork->flags & IPCORK_OPT)
1214                 opt = cork->opt;
1215 
1216         if (!(rt->dst.dev->features&NETIF_F_SG))
1217                 return -EOPNOTSUPP;
1218 
1219         hh_len = LL_RESERVED_SPACE(rt->dst.dev);
1220         mtu = cork->fragsize;
1221 
1222         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
1223         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
1224         maxnonfragsize = ip_sk_ignore_df(sk) ? 0xFFFF : mtu;
1225 
1226         if (cork->length + size > maxnonfragsize - fragheaderlen) {
1227                 ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
1228                                mtu - (opt ? opt->optlen : 0));
1229                 return -EMSGSIZE;
1230         }
1231 
1232         skb = skb_peek_tail(&sk->sk_write_queue);
1233         if (!skb)
1234                 return -EINVAL;
1235 
1236         if ((size + skb->len > mtu) &&
1237             (sk->sk_protocol == IPPROTO_UDP) &&
1238             (rt->dst.dev->features & NETIF_F_UFO)) {
1239                 if (skb->ip_summed != CHECKSUM_PARTIAL)
1240                         return -EOPNOTSUPP;
1241 
1242                 skb_shinfo(skb)->gso_size = mtu - fragheaderlen;
1243                 skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
1244         }
1245         cork->length += size;
1246 
1247         while (size > 0) {
1248                 if (skb_is_gso(skb)) {
1249                         len = size;
1250                 } else {
1251 
1252                         /* Check if the remaining data fits into current packet. */
1253                         len = mtu - skb->len;
1254                         if (len < size)
1255                                 len = maxfraglen - skb->len;
1256                 }
1257                 if (len <= 0) {
1258                         struct sk_buff *skb_prev;
1259                         int alloclen;
1260 
1261                         skb_prev = skb;
1262                         fraggap = skb_prev->len - maxfraglen;
1263 
1264                         alloclen = fragheaderlen + hh_len + fraggap + 15;
1265                         skb = sock_wmalloc(sk, alloclen, 1, sk->sk_allocation);
1266                         if (unlikely(!skb)) {
1267                                 err = -ENOBUFS;
1268                                 goto error;
1269                         }
1270 
1271                         /*
1272                          *      Fill in the control structures
1273                          */
1274                         skb->ip_summed = CHECKSUM_NONE;
1275                         skb->csum = 0;
1276                         skb_reserve(skb, hh_len);
1277 
1278                         /*
1279                          *      Find where to start putting bytes.
1280                          */
1281                         skb_put(skb, fragheaderlen + fraggap);
1282                         skb_reset_network_header(skb);
1283                         skb->transport_header = (skb->network_header +
1284                                                  fragheaderlen);
1285                         if (fraggap) {
1286                                 skb->csum = skb_copy_and_csum_bits(skb_prev,
1287                                                                    maxfraglen,
1288                                                     skb_transport_header(skb),
1289                                                                    fraggap, 0);
1290                                 skb_prev->csum = csum_sub(skb_prev->csum,
1291                                                           skb->csum);
1292                                 pskb_trim_unique(skb_prev, maxfraglen);
1293                         }
1294 
1295                         /*
1296                          * Put the packet on the pending queue.
1297                          */
1298                         __skb_queue_tail(&sk->sk_write_queue, skb);
1299                         continue;
1300                 }
1301 
1302                 if (len > size)
1303                         len = size;
1304 
1305                 if (skb_append_pagefrags(skb, page, offset, len)) {
1306                         err = -EMSGSIZE;
1307                         goto error;
1308                 }
1309 
1310                 if (skb->ip_summed == CHECKSUM_NONE) {
1311                         __wsum csum;
1312                         csum = csum_page(page, offset, len);
1313                         skb->csum = csum_block_add(skb->csum, csum, skb->len);
1314                 }
1315 
1316                 skb->len += len;
1317                 skb->data_len += len;
1318                 skb->truesize += len;
1319                 atomic_add(len, &sk->sk_wmem_alloc);
1320                 offset += len;
1321                 size -= len;
1322         }
1323         return 0;
1324 
1325 error:
1326         cork->length -= size;
1327         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1328         return err;
1329 }
1330 
1331 static void ip_cork_release(struct inet_cork *cork)
1332 {
1333         cork->flags &= ~IPCORK_OPT;
1334         kfree(cork->opt);
1335         cork->opt = NULL;
1336         dst_release(cork->dst);
1337         cork->dst = NULL;
1338 }
1339 
1340 /*
1341  *      Combined all pending IP fragments on the socket as one IP datagram
1342  *      and push them out.
1343  */
1344 struct sk_buff *__ip_make_skb(struct sock *sk,
1345                               struct flowi4 *fl4,
1346                               struct sk_buff_head *queue,
1347                               struct inet_cork *cork)
1348 {
1349         struct sk_buff *skb, *tmp_skb;
1350         struct sk_buff **tail_skb;
1351         struct inet_sock *inet = inet_sk(sk);
1352         struct net *net = sock_net(sk);
1353         struct ip_options *opt = NULL;
1354         struct rtable *rt = (struct rtable *)cork->dst;
1355         struct iphdr *iph;
1356         __be16 df = 0;
1357         __u8 ttl;
1358 
1359         skb = __skb_dequeue(queue);
1360         if (!skb)
1361                 goto out;
1362         tail_skb = &(skb_shinfo(skb)->frag_list);
1363 
1364         /* move skb->data to ip header from ext header */
1365         if (skb->data < skb_network_header(skb))
1366                 __skb_pull(skb, skb_network_offset(skb));
1367         while ((tmp_skb = __skb_dequeue(queue)) != NULL) {
1368                 __skb_pull(tmp_skb, skb_network_header_len(skb));
1369                 *tail_skb = tmp_skb;
1370                 tail_skb = &(tmp_skb->next);
1371                 skb->len += tmp_skb->len;
1372                 skb->data_len += tmp_skb->len;
1373                 skb->truesize += tmp_skb->truesize;
1374                 tmp_skb->destructor = NULL;
1375                 tmp_skb->sk = NULL;
1376         }
1377 
1378         /* Unless user demanded real pmtu discovery (IP_PMTUDISC_DO), we allow
1379          * to fragment the frame generated here. No matter, what transforms
1380          * how transforms change size of the packet, it will come out.
1381          */
1382         skb->ignore_df = ip_sk_ignore_df(sk);
1383 
1384         /* DF bit is set when we want to see DF on outgoing frames.
1385          * If ignore_df is set too, we still allow to fragment this frame
1386          * locally. */
1387         if (inet->pmtudisc == IP_PMTUDISC_DO ||
1388             inet->pmtudisc == IP_PMTUDISC_PROBE ||
1389             (skb->len <= dst_mtu(&rt->dst) &&
1390              ip_dont_fragment(sk, &rt->dst)))
1391                 df = htons(IP_DF);
1392 
1393         if (cork->flags & IPCORK_OPT)
1394                 opt = cork->opt;
1395 
1396         if (cork->ttl != 0)
1397                 ttl = cork->ttl;
1398         else if (rt->rt_type == RTN_MULTICAST)
1399                 ttl = inet->mc_ttl;
1400         else
1401                 ttl = ip_select_ttl(inet, &rt->dst);
1402 
1403         iph = ip_hdr(skb);
1404         iph->version = 4;
1405         iph->ihl = 5;
1406         iph->tos = (cork->tos != -1) ? cork->tos : inet->tos;
1407         iph->frag_off = df;
1408         iph->ttl = ttl;
1409         iph->protocol = sk->sk_protocol;
1410         ip_copy_addrs(iph, fl4);
1411         ip_select_ident(net, skb, sk);
1412 
1413         if (opt) {
1414                 iph->ihl += opt->optlen>>2;
1415                 ip_options_build(skb, opt, cork->addr, rt, 0);
1416         }
1417 
1418         skb->priority = (cork->tos != -1) ? cork->priority: sk->sk_priority;
1419         skb->mark = sk->sk_mark;
1420         /*
1421          * Steal rt from cork.dst to avoid a pair of atomic_inc/atomic_dec
1422          * on dst refcount
1423          */
1424         cork->dst = NULL;
1425         skb_dst_set(skb, &rt->dst);
1426 
1427         if (iph->protocol == IPPROTO_ICMP)
1428                 icmp_out_count(net, ((struct icmphdr *)
1429                         skb_transport_header(skb))->type);
1430 
1431         ip_cork_release(cork);
1432 out:
1433         return skb;
1434 }
1435 
1436 int ip_send_skb(struct net *net, struct sk_buff *skb)
1437 {
1438         int err;
1439 
1440         err = ip_local_out(net, skb->sk, skb);
1441         if (err) {
1442                 if (err > 0)
1443                         err = net_xmit_errno(err);
1444                 if (err)
1445                         IP_INC_STATS(net, IPSTATS_MIB_OUTDISCARDS);
1446         }
1447 
1448         return err;
1449 }
1450 
1451 int ip_push_pending_frames(struct sock *sk, struct flowi4 *fl4)
1452 {
1453         struct sk_buff *skb;
1454 
1455         skb = ip_finish_skb(sk, fl4);
1456         if (!skb)
1457                 return 0;
1458 
1459         /* Netfilter gets whole the not fragmented skb. */
1460         return ip_send_skb(sock_net(sk), skb);
1461 }
1462 
1463 /*
1464  *      Throw away all pending data on the socket.
1465  */
1466 static void __ip_flush_pending_frames(struct sock *sk,
1467                                       struct sk_buff_head *queue,
1468                                       struct inet_cork *cork)
1469 {
1470         struct sk_buff *skb;
1471 
1472         while ((skb = __skb_dequeue_tail(queue)) != NULL)
1473                 kfree_skb(skb);
1474 
1475         ip_cork_release(cork);
1476 }
1477 
1478 void ip_flush_pending_frames(struct sock *sk)
1479 {
1480         __ip_flush_pending_frames(sk, &sk->sk_write_queue, &inet_sk(sk)->cork.base);
1481 }
1482 
1483 struct sk_buff *ip_make_skb(struct sock *sk,
1484                             struct flowi4 *fl4,
1485                             int getfrag(void *from, char *to, int offset,
1486                                         int len, int odd, struct sk_buff *skb),
1487                             void *from, int length, int transhdrlen,
1488                             struct ipcm_cookie *ipc, struct rtable **rtp,
1489                             unsigned int flags)
1490 {
1491         struct inet_cork cork;
1492         struct sk_buff_head queue;
1493         int err;
1494 
1495         if (flags & MSG_PROBE)
1496                 return NULL;
1497 
1498         __skb_queue_head_init(&queue);
1499 
1500         cork.flags = 0;
1501         cork.addr = 0;
1502         cork.opt = NULL;
1503         err = ip_setup_cork(sk, &cork, ipc, rtp);
1504         if (err)
1505                 return ERR_PTR(err);
1506 
1507         err = __ip_append_data(sk, fl4, &queue, &cork,
1508                                &current->task_frag, getfrag,
1509                                from, length, transhdrlen, flags);
1510         if (err) {
1511                 __ip_flush_pending_frames(sk, &queue, &cork);
1512                 return ERR_PTR(err);
1513         }
1514 
1515         return __ip_make_skb(sk, fl4, &queue, &cork);
1516 }
1517 
1518 /*
1519  *      Fetch data from kernel space and fill in checksum if needed.
1520  */
1521 static int ip_reply_glue_bits(void *dptr, char *to, int offset,
1522                               int len, int odd, struct sk_buff *skb)
1523 {
1524         __wsum csum;
1525 
1526         csum = csum_partial_copy_nocheck(dptr+offset, to, len, 0);
1527         skb->csum = csum_block_add(skb->csum, csum, odd);
1528         return 0;
1529 }
1530 
1531 /*
1532  *      Generic function to send a packet as reply to another packet.
1533  *      Used to send some TCP resets/acks so far.
1534  */
1535 void ip_send_unicast_reply(struct sock *sk, struct sk_buff *skb,
1536                            const struct ip_options *sopt,
1537                            __be32 daddr, __be32 saddr,
1538                            const struct ip_reply_arg *arg,
1539                            unsigned int len)
1540 {
1541         struct ip_options_data replyopts;
1542         struct ipcm_cookie ipc;
1543         struct flowi4 fl4;
1544         struct rtable *rt = skb_rtable(skb);
1545         struct net *net = sock_net(sk);
1546         struct sk_buff *nskb;
1547         int err;
1548         int oif;
1549 
1550         if (__ip_options_echo(&replyopts.opt.opt, skb, sopt))
1551                 return;
1552 
1553         ipc.addr = daddr;
1554         ipc.opt = NULL;
1555         ipc.tx_flags = 0;
1556         ipc.ttl = 0;
1557         ipc.tos = -1;
1558 
1559         if (replyopts.opt.opt.optlen) {
1560                 ipc.opt = &replyopts.opt;
1561 
1562                 if (replyopts.opt.opt.srr)
1563                         daddr = replyopts.opt.opt.faddr;
1564         }
1565 
1566         oif = arg->bound_dev_if;
1567         if (!oif && netif_index_is_l3_master(net, skb->skb_iif))
1568                 oif = skb->skb_iif;
1569 
1570         flowi4_init_output(&fl4, oif,
1571                            IP4_REPLY_MARK(net, skb->mark),
1572                            RT_TOS(arg->tos),
1573                            RT_SCOPE_UNIVERSE, ip_hdr(skb)->protocol,
1574                            ip_reply_arg_flowi_flags(arg),
1575                            daddr, saddr,
1576                            tcp_hdr(skb)->source, tcp_hdr(skb)->dest);
1577         security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
1578         rt = ip_route_output_key(net, &fl4);
1579         if (IS_ERR(rt))
1580                 return;
1581 
1582         inet_sk(sk)->tos = arg->tos;
1583 
1584         sk->sk_priority = skb->priority;
1585         sk->sk_protocol = ip_hdr(skb)->protocol;
1586         sk->sk_bound_dev_if = arg->bound_dev_if;
1587         sk->sk_sndbuf = sysctl_wmem_default;
1588         err = ip_append_data(sk, &fl4, ip_reply_glue_bits, arg->iov->iov_base,
1589                              len, 0, &ipc, &rt, MSG_DONTWAIT);
1590         if (unlikely(err)) {
1591                 ip_flush_pending_frames(sk);
1592                 goto out;
1593         }
1594 
1595         nskb = skb_peek(&sk->sk_write_queue);
1596         if (nskb) {
1597                 if (arg->csumoffset >= 0)
1598                         *((__sum16 *)skb_transport_header(nskb) +
1599                           arg->csumoffset) = csum_fold(csum_add(nskb->csum,
1600                                                                 arg->csum));
1601                 nskb->ip_summed = CHECKSUM_NONE;
1602                 ip_push_pending_frames(sk, &fl4);
1603         }
1604 out:
1605         ip_rt_put(rt);
1606 }
1607 
1608 void __init ip_init(void)
1609 {
1610         ip_rt_init();
1611         inet_initpeers();
1612 
1613 #if defined(CONFIG_IP_MULTICAST)
1614         igmp_mc_init();
1615 #endif
1616 }
1617 

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