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Linux/net/ipv4/ip_output.c

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  1 // SPDX-License-Identifier: GPL-2.0-only
  2 /*
  3  * INET         An implementation of the TCP/IP protocol suite for the LINUX
  4  *              operating system.  INET is implemented using the  BSD Socket
  5  *              interface as the means of communication with the user level.
  6  *
  7  *              The Internet Protocol (IP) output module.
  8  *
  9  * Authors:     Ross Biro
 10  *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 11  *              Donald Becker, <becker@super.org>
 12  *              Alan Cox, <Alan.Cox@linux.org>
 13  *              Richard Underwood
 14  *              Stefan Becker, <stefanb@yello.ping.de>
 15  *              Jorge Cwik, <jorge@laser.satlink.net>
 16  *              Arnt Gulbrandsen, <agulbra@nvg.unit.no>
 17  *              Hirokazu Takahashi, <taka@valinux.co.jp>
 18  *
 19  *      See ip_input.c for original log
 20  *
 21  *      Fixes:
 22  *              Alan Cox        :       Missing nonblock feature in ip_build_xmit.
 23  *              Mike Kilburn    :       htons() missing in ip_build_xmit.
 24  *              Bradford Johnson:       Fix faulty handling of some frames when
 25  *                                      no route is found.
 26  *              Alexander Demenshin:    Missing sk/skb free in ip_queue_xmit
 27  *                                      (in case if packet not accepted by
 28  *                                      output firewall rules)
 29  *              Mike McLagan    :       Routing by source
 30  *              Alexey Kuznetsov:       use new route cache
 31  *              Andi Kleen:             Fix broken PMTU recovery and remove
 32  *                                      some redundant tests.
 33  *      Vitaly E. Lavrov        :       Transparent proxy revived after year coma.
 34  *              Andi Kleen      :       Replace ip_reply with ip_send_reply.
 35  *              Andi Kleen      :       Split fast and slow ip_build_xmit path
 36  *                                      for decreased register pressure on x86
 37  *                                      and more readibility.
 38  *              Marc Boucher    :       When call_out_firewall returns FW_QUEUE,
 39  *                                      silently drop skb instead of failing with -EPERM.
 40  *              Detlev Wengorz  :       Copy protocol for fragments.
 41  *              Hirokazu Takahashi:     HW checksumming for outgoing UDP
 42  *                                      datagrams.
 43  *              Hirokazu Takahashi:     sendfile() on UDP works now.
 44  */
 45 
 46 #include <linux/uaccess.h>
 47 #include <linux/module.h>
 48 #include <linux/types.h>
 49 #include <linux/kernel.h>
 50 #include <linux/mm.h>
 51 #include <linux/string.h>
 52 #include <linux/errno.h>
 53 #include <linux/highmem.h>
 54 #include <linux/slab.h>
 55 
 56 #include <linux/socket.h>
 57 #include <linux/sockios.h>
 58 #include <linux/in.h>
 59 #include <linux/inet.h>
 60 #include <linux/netdevice.h>
 61 #include <linux/etherdevice.h>
 62 #include <linux/proc_fs.h>
 63 #include <linux/stat.h>
 64 #include <linux/init.h>
 65 
 66 #include <net/snmp.h>
 67 #include <net/ip.h>
 68 #include <net/protocol.h>
 69 #include <net/route.h>
 70 #include <net/xfrm.h>
 71 #include <linux/skbuff.h>
 72 #include <net/sock.h>
 73 #include <net/arp.h>
 74 #include <net/icmp.h>
 75 #include <net/checksum.h>
 76 #include <net/inetpeer.h>
 77 #include <net/lwtunnel.h>
 78 #include <linux/bpf-cgroup.h>
 79 #include <linux/igmp.h>
 80 #include <linux/netfilter_ipv4.h>
 81 #include <linux/netfilter_bridge.h>
 82 #include <linux/netlink.h>
 83 #include <linux/tcp.h>
 84 
 85 static int
 86 ip_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
 87             unsigned int mtu,
 88             int (*output)(struct net *, struct sock *, struct sk_buff *));
 89 
 90 /* Generate a checksum for an outgoing IP datagram. */
 91 void ip_send_check(struct iphdr *iph)
 92 {
 93         iph->check = 0;
 94         iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
 95 }
 96 EXPORT_SYMBOL(ip_send_check);
 97 
 98 int __ip_local_out(struct net *net, struct sock *sk, struct sk_buff *skb)
 99 {
100         struct iphdr *iph = ip_hdr(skb);
101 
102         iph->tot_len = htons(skb->len);
103         ip_send_check(iph);
104 
105         /* if egress device is enslaved to an L3 master device pass the
106          * skb to its handler for processing
107          */
108         skb = l3mdev_ip_out(sk, skb);
109         if (unlikely(!skb))
110                 return 0;
111 
112         skb->protocol = htons(ETH_P_IP);
113 
114         return nf_hook(NFPROTO_IPV4, NF_INET_LOCAL_OUT,
115                        net, sk, skb, NULL, skb_dst(skb)->dev,
116                        dst_output);
117 }
118 
119 int ip_local_out(struct net *net, struct sock *sk, struct sk_buff *skb)
120 {
121         int err;
122 
123         err = __ip_local_out(net, sk, skb);
124         if (likely(err == 1))
125                 err = dst_output(net, sk, skb);
126 
127         return err;
128 }
129 EXPORT_SYMBOL_GPL(ip_local_out);
130 
131 static inline int ip_select_ttl(struct inet_sock *inet, struct dst_entry *dst)
132 {
133         int ttl = inet->uc_ttl;
134 
135         if (ttl < 0)
136                 ttl = ip4_dst_hoplimit(dst);
137         return ttl;
138 }
139 
140 /*
141  *              Add an ip header to a skbuff and send it out.
142  *
143  */
144 int ip_build_and_send_pkt(struct sk_buff *skb, const struct sock *sk,
145                           __be32 saddr, __be32 daddr, struct ip_options_rcu *opt)
146 {
147         struct inet_sock *inet = inet_sk(sk);
148         struct rtable *rt = skb_rtable(skb);
149         struct net *net = sock_net(sk);
150         struct iphdr *iph;
151 
152         /* Build the IP header. */
153         skb_push(skb, sizeof(struct iphdr) + (opt ? opt->opt.optlen : 0));
154         skb_reset_network_header(skb);
155         iph = ip_hdr(skb);
156         iph->version  = 4;
157         iph->ihl      = 5;
158         iph->tos      = inet->tos;
159         iph->ttl      = ip_select_ttl(inet, &rt->dst);
160         iph->daddr    = (opt && opt->opt.srr ? opt->opt.faddr : daddr);
161         iph->saddr    = saddr;
162         iph->protocol = sk->sk_protocol;
163         if (ip_dont_fragment(sk, &rt->dst)) {
164                 iph->frag_off = htons(IP_DF);
165                 iph->id = 0;
166         } else {
167                 iph->frag_off = 0;
168                 __ip_select_ident(net, iph, 1);
169         }
170 
171         if (opt && opt->opt.optlen) {
172                 iph->ihl += opt->opt.optlen>>2;
173                 ip_options_build(skb, &opt->opt, daddr, rt, 0);
174         }
175 
176         skb->priority = sk->sk_priority;
177         if (!skb->mark)
178                 skb->mark = sk->sk_mark;
179 
180         /* Send it out. */
181         return ip_local_out(net, skb->sk, skb);
182 }
183 EXPORT_SYMBOL_GPL(ip_build_and_send_pkt);
184 
185 static int ip_finish_output2(struct net *net, struct sock *sk, struct sk_buff *skb)
186 {
187         struct dst_entry *dst = skb_dst(skb);
188         struct rtable *rt = (struct rtable *)dst;
189         struct net_device *dev = dst->dev;
190         unsigned int hh_len = LL_RESERVED_SPACE(dev);
191         struct neighbour *neigh;
192         bool is_v6gw = false;
193 
194         if (rt->rt_type == RTN_MULTICAST) {
195                 IP_UPD_PO_STATS(net, IPSTATS_MIB_OUTMCAST, skb->len);
196         } else if (rt->rt_type == RTN_BROADCAST)
197                 IP_UPD_PO_STATS(net, IPSTATS_MIB_OUTBCAST, skb->len);
198 
199         /* Be paranoid, rather than too clever. */
200         if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) {
201                 struct sk_buff *skb2;
202 
203                 skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev));
204                 if (!skb2) {
205                         kfree_skb(skb);
206                         return -ENOMEM;
207                 }
208                 if (skb->sk)
209                         skb_set_owner_w(skb2, skb->sk);
210                 consume_skb(skb);
211                 skb = skb2;
212         }
213 
214         if (lwtunnel_xmit_redirect(dst->lwtstate)) {
215                 int res = lwtunnel_xmit(skb);
216 
217                 if (res < 0 || res == LWTUNNEL_XMIT_DONE)
218                         return res;
219         }
220 
221         rcu_read_lock_bh();
222         neigh = ip_neigh_for_gw(rt, skb, &is_v6gw);
223         if (!IS_ERR(neigh)) {
224                 int res;
225 
226                 sock_confirm_neigh(skb, neigh);
227                 /* if crossing protocols, can not use the cached header */
228                 res = neigh_output(neigh, skb, is_v6gw);
229                 rcu_read_unlock_bh();
230                 return res;
231         }
232         rcu_read_unlock_bh();
233 
234         net_dbg_ratelimited("%s: No header cache and no neighbour!\n",
235                             __func__);
236         kfree_skb(skb);
237         return -EINVAL;
238 }
239 
240 static int ip_finish_output_gso(struct net *net, struct sock *sk,
241                                 struct sk_buff *skb, unsigned int mtu)
242 {
243         netdev_features_t features;
244         struct sk_buff *segs;
245         int ret = 0;
246 
247         /* common case: seglen is <= mtu
248          */
249         if (skb_gso_validate_network_len(skb, mtu))
250                 return ip_finish_output2(net, sk, skb);
251 
252         /* Slowpath -  GSO segment length exceeds the egress MTU.
253          *
254          * This can happen in several cases:
255          *  - Forwarding of a TCP GRO skb, when DF flag is not set.
256          *  - Forwarding of an skb that arrived on a virtualization interface
257          *    (virtio-net/vhost/tap) with TSO/GSO size set by other network
258          *    stack.
259          *  - Local GSO skb transmitted on an NETIF_F_TSO tunnel stacked over an
260          *    interface with a smaller MTU.
261          *  - Arriving GRO skb (or GSO skb in a virtualized environment) that is
262          *    bridged to a NETIF_F_TSO tunnel stacked over an interface with an
263          *    insufficent MTU.
264          */
265         features = netif_skb_features(skb);
266         BUILD_BUG_ON(sizeof(*IPCB(skb)) > SKB_SGO_CB_OFFSET);
267         segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK);
268         if (IS_ERR_OR_NULL(segs)) {
269                 kfree_skb(skb);
270                 return -ENOMEM;
271         }
272 
273         consume_skb(skb);
274 
275         do {
276                 struct sk_buff *nskb = segs->next;
277                 int err;
278 
279                 skb_mark_not_on_list(segs);
280                 err = ip_fragment(net, sk, segs, mtu, ip_finish_output2);
281 
282                 if (err && ret == 0)
283                         ret = err;
284                 segs = nskb;
285         } while (segs);
286 
287         return ret;
288 }
289 
290 static int __ip_finish_output(struct net *net, struct sock *sk, struct sk_buff *skb)
291 {
292         unsigned int mtu;
293 
294 #if defined(CONFIG_NETFILTER) && defined(CONFIG_XFRM)
295         /* Policy lookup after SNAT yielded a new policy */
296         if (skb_dst(skb)->xfrm) {
297                 IPCB(skb)->flags |= IPSKB_REROUTED;
298                 return dst_output(net, sk, skb);
299         }
300 #endif
301         mtu = ip_skb_dst_mtu(sk, skb);
302         if (skb_is_gso(skb))
303                 return ip_finish_output_gso(net, sk, skb, mtu);
304 
305         if (skb->len > mtu || (IPCB(skb)->flags & IPSKB_FRAG_PMTU))
306                 return ip_fragment(net, sk, skb, mtu, ip_finish_output2);
307 
308         return ip_finish_output2(net, sk, skb);
309 }
310 
311 static int ip_finish_output(struct net *net, struct sock *sk, struct sk_buff *skb)
312 {
313         int ret;
314 
315         ret = BPF_CGROUP_RUN_PROG_INET_EGRESS(sk, skb);
316         switch (ret) {
317         case NET_XMIT_SUCCESS:
318                 return __ip_finish_output(net, sk, skb);
319         case NET_XMIT_CN:
320                 return __ip_finish_output(net, sk, skb) ? : ret;
321         default:
322                 kfree_skb(skb);
323                 return ret;
324         }
325 }
326 
327 static int ip_mc_finish_output(struct net *net, struct sock *sk,
328                                struct sk_buff *skb)
329 {
330         struct rtable *new_rt;
331         bool do_cn = false;
332         int ret, err;
333 
334         ret = BPF_CGROUP_RUN_PROG_INET_EGRESS(sk, skb);
335         switch (ret) {
336         case NET_XMIT_CN:
337                 do_cn = true;
338                 /* fall through */
339         case NET_XMIT_SUCCESS:
340                 break;
341         default:
342                 kfree_skb(skb);
343                 return ret;
344         }
345 
346         /* Reset rt_iif so that inet_iif() will return skb->skb_iif. Setting
347          * this to non-zero causes ipi_ifindex in in_pktinfo to be overwritten,
348          * see ipv4_pktinfo_prepare().
349          */
350         new_rt = rt_dst_clone(net->loopback_dev, skb_rtable(skb));
351         if (new_rt) {
352                 new_rt->rt_iif = 0;
353                 skb_dst_drop(skb);
354                 skb_dst_set(skb, &new_rt->dst);
355         }
356 
357         err = dev_loopback_xmit(net, sk, skb);
358         return (do_cn && err) ? ret : err;
359 }
360 
361 int ip_mc_output(struct net *net, struct sock *sk, struct sk_buff *skb)
362 {
363         struct rtable *rt = skb_rtable(skb);
364         struct net_device *dev = rt->dst.dev;
365 
366         /*
367          *      If the indicated interface is up and running, send the packet.
368          */
369         IP_UPD_PO_STATS(net, IPSTATS_MIB_OUT, skb->len);
370 
371         skb->dev = dev;
372         skb->protocol = htons(ETH_P_IP);
373 
374         /*
375          *      Multicasts are looped back for other local users
376          */
377 
378         if (rt->rt_flags&RTCF_MULTICAST) {
379                 if (sk_mc_loop(sk)
380 #ifdef CONFIG_IP_MROUTE
381                 /* Small optimization: do not loopback not local frames,
382                    which returned after forwarding; they will be  dropped
383                    by ip_mr_input in any case.
384                    Note, that local frames are looped back to be delivered
385                    to local recipients.
386 
387                    This check is duplicated in ip_mr_input at the moment.
388                  */
389                     &&
390                     ((rt->rt_flags & RTCF_LOCAL) ||
391                      !(IPCB(skb)->flags & IPSKB_FORWARDED))
392 #endif
393                    ) {
394                         struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
395                         if (newskb)
396                                 NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING,
397                                         net, sk, newskb, NULL, newskb->dev,
398                                         ip_mc_finish_output);
399                 }
400 
401                 /* Multicasts with ttl 0 must not go beyond the host */
402 
403                 if (ip_hdr(skb)->ttl == 0) {
404                         kfree_skb(skb);
405                         return 0;
406                 }
407         }
408 
409         if (rt->rt_flags&RTCF_BROADCAST) {
410                 struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
411                 if (newskb)
412                         NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING,
413                                 net, sk, newskb, NULL, newskb->dev,
414                                 ip_mc_finish_output);
415         }
416 
417         return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
418                             net, sk, skb, NULL, skb->dev,
419                             ip_finish_output,
420                             !(IPCB(skb)->flags & IPSKB_REROUTED));
421 }
422 
423 int ip_output(struct net *net, struct sock *sk, struct sk_buff *skb)
424 {
425         struct net_device *dev = skb_dst(skb)->dev;
426 
427         IP_UPD_PO_STATS(net, IPSTATS_MIB_OUT, skb->len);
428 
429         skb->dev = dev;
430         skb->protocol = htons(ETH_P_IP);
431 
432         return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
433                             net, sk, skb, NULL, dev,
434                             ip_finish_output,
435                             !(IPCB(skb)->flags & IPSKB_REROUTED));
436 }
437 
438 /*
439  * copy saddr and daddr, possibly using 64bit load/stores
440  * Equivalent to :
441  *   iph->saddr = fl4->saddr;
442  *   iph->daddr = fl4->daddr;
443  */
444 static void ip_copy_addrs(struct iphdr *iph, const struct flowi4 *fl4)
445 {
446         BUILD_BUG_ON(offsetof(typeof(*fl4), daddr) !=
447                      offsetof(typeof(*fl4), saddr) + sizeof(fl4->saddr));
448         memcpy(&iph->saddr, &fl4->saddr,
449                sizeof(fl4->saddr) + sizeof(fl4->daddr));
450 }
451 
452 /* Note: skb->sk can be different from sk, in case of tunnels */
453 int __ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl,
454                     __u8 tos)
455 {
456         struct inet_sock *inet = inet_sk(sk);
457         struct net *net = sock_net(sk);
458         struct ip_options_rcu *inet_opt;
459         struct flowi4 *fl4;
460         struct rtable *rt;
461         struct iphdr *iph;
462         int res;
463 
464         /* Skip all of this if the packet is already routed,
465          * f.e. by something like SCTP.
466          */
467         rcu_read_lock();
468         inet_opt = rcu_dereference(inet->inet_opt);
469         fl4 = &fl->u.ip4;
470         rt = skb_rtable(skb);
471         if (rt)
472                 goto packet_routed;
473 
474         /* Make sure we can route this packet. */
475         rt = (struct rtable *)__sk_dst_check(sk, 0);
476         if (!rt) {
477                 __be32 daddr;
478 
479                 /* Use correct destination address if we have options. */
480                 daddr = inet->inet_daddr;
481                 if (inet_opt && inet_opt->opt.srr)
482                         daddr = inet_opt->opt.faddr;
483 
484                 /* If this fails, retransmit mechanism of transport layer will
485                  * keep trying until route appears or the connection times
486                  * itself out.
487                  */
488                 rt = ip_route_output_ports(net, fl4, sk,
489                                            daddr, inet->inet_saddr,
490                                            inet->inet_dport,
491                                            inet->inet_sport,
492                                            sk->sk_protocol,
493                                            RT_CONN_FLAGS_TOS(sk, tos),
494                                            sk->sk_bound_dev_if);
495                 if (IS_ERR(rt))
496                         goto no_route;
497                 sk_setup_caps(sk, &rt->dst);
498         }
499         skb_dst_set_noref(skb, &rt->dst);
500 
501 packet_routed:
502         if (inet_opt && inet_opt->opt.is_strictroute && rt->rt_uses_gateway)
503                 goto no_route;
504 
505         /* OK, we know where to send it, allocate and build IP header. */
506         skb_push(skb, sizeof(struct iphdr) + (inet_opt ? inet_opt->opt.optlen : 0));
507         skb_reset_network_header(skb);
508         iph = ip_hdr(skb);
509         *((__be16 *)iph) = htons((4 << 12) | (5 << 8) | (tos & 0xff));
510         if (ip_dont_fragment(sk, &rt->dst) && !skb->ignore_df)
511                 iph->frag_off = htons(IP_DF);
512         else
513                 iph->frag_off = 0;
514         iph->ttl      = ip_select_ttl(inet, &rt->dst);
515         iph->protocol = sk->sk_protocol;
516         ip_copy_addrs(iph, fl4);
517 
518         /* Transport layer set skb->h.foo itself. */
519 
520         if (inet_opt && inet_opt->opt.optlen) {
521                 iph->ihl += inet_opt->opt.optlen >> 2;
522                 ip_options_build(skb, &inet_opt->opt, inet->inet_daddr, rt, 0);
523         }
524 
525         ip_select_ident_segs(net, skb, sk,
526                              skb_shinfo(skb)->gso_segs ?: 1);
527 
528         /* TODO : should we use skb->sk here instead of sk ? */
529         skb->priority = sk->sk_priority;
530         skb->mark = sk->sk_mark;
531 
532         res = ip_local_out(net, sk, skb);
533         rcu_read_unlock();
534         return res;
535 
536 no_route:
537         rcu_read_unlock();
538         IP_INC_STATS(net, IPSTATS_MIB_OUTNOROUTES);
539         kfree_skb(skb);
540         return -EHOSTUNREACH;
541 }
542 EXPORT_SYMBOL(__ip_queue_xmit);
543 
544 static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
545 {
546         to->pkt_type = from->pkt_type;
547         to->priority = from->priority;
548         to->protocol = from->protocol;
549         to->skb_iif = from->skb_iif;
550         skb_dst_drop(to);
551         skb_dst_copy(to, from);
552         to->dev = from->dev;
553         to->mark = from->mark;
554 
555         skb_copy_hash(to, from);
556 
557 #ifdef CONFIG_NET_SCHED
558         to->tc_index = from->tc_index;
559 #endif
560         nf_copy(to, from);
561         skb_ext_copy(to, from);
562 #if IS_ENABLED(CONFIG_IP_VS)
563         to->ipvs_property = from->ipvs_property;
564 #endif
565         skb_copy_secmark(to, from);
566 }
567 
568 static int ip_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
569                        unsigned int mtu,
570                        int (*output)(struct net *, struct sock *, struct sk_buff *))
571 {
572         struct iphdr *iph = ip_hdr(skb);
573 
574         if ((iph->frag_off & htons(IP_DF)) == 0)
575                 return ip_do_fragment(net, sk, skb, output);
576 
577         if (unlikely(!skb->ignore_df ||
578                      (IPCB(skb)->frag_max_size &&
579                       IPCB(skb)->frag_max_size > mtu))) {
580                 IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
581                 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
582                           htonl(mtu));
583                 kfree_skb(skb);
584                 return -EMSGSIZE;
585         }
586 
587         return ip_do_fragment(net, sk, skb, output);
588 }
589 
590 void ip_fraglist_init(struct sk_buff *skb, struct iphdr *iph,
591                       unsigned int hlen, struct ip_fraglist_iter *iter)
592 {
593         unsigned int first_len = skb_pagelen(skb);
594 
595         iter->frag = skb_shinfo(skb)->frag_list;
596         skb_frag_list_init(skb);
597 
598         iter->offset = 0;
599         iter->iph = iph;
600         iter->hlen = hlen;
601 
602         skb->data_len = first_len - skb_headlen(skb);
603         skb->len = first_len;
604         iph->tot_len = htons(first_len);
605         iph->frag_off = htons(IP_MF);
606         ip_send_check(iph);
607 }
608 EXPORT_SYMBOL(ip_fraglist_init);
609 
610 static void ip_fraglist_ipcb_prepare(struct sk_buff *skb,
611                                      struct ip_fraglist_iter *iter)
612 {
613         struct sk_buff *to = iter->frag;
614 
615         /* Copy the flags to each fragment. */
616         IPCB(to)->flags = IPCB(skb)->flags;
617 
618         if (iter->offset == 0)
619                 ip_options_fragment(to);
620 }
621 
622 void ip_fraglist_prepare(struct sk_buff *skb, struct ip_fraglist_iter *iter)
623 {
624         unsigned int hlen = iter->hlen;
625         struct iphdr *iph = iter->iph;
626         struct sk_buff *frag;
627 
628         frag = iter->frag;
629         frag->ip_summed = CHECKSUM_NONE;
630         skb_reset_transport_header(frag);
631         __skb_push(frag, hlen);
632         skb_reset_network_header(frag);
633         memcpy(skb_network_header(frag), iph, hlen);
634         iter->iph = ip_hdr(frag);
635         iph = iter->iph;
636         iph->tot_len = htons(frag->len);
637         ip_copy_metadata(frag, skb);
638         iter->offset += skb->len - hlen;
639         iph->frag_off = htons(iter->offset >> 3);
640         if (frag->next)
641                 iph->frag_off |= htons(IP_MF);
642         /* Ready, complete checksum */
643         ip_send_check(iph);
644 }
645 EXPORT_SYMBOL(ip_fraglist_prepare);
646 
647 void ip_frag_init(struct sk_buff *skb, unsigned int hlen,
648                   unsigned int ll_rs, unsigned int mtu, bool DF,
649                   struct ip_frag_state *state)
650 {
651         struct iphdr *iph = ip_hdr(skb);
652 
653         state->DF = DF;
654         state->hlen = hlen;
655         state->ll_rs = ll_rs;
656         state->mtu = mtu;
657 
658         state->left = skb->len - hlen;  /* Space per frame */
659         state->ptr = hlen;              /* Where to start from */
660 
661         state->offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3;
662         state->not_last_frag = iph->frag_off & htons(IP_MF);
663 }
664 EXPORT_SYMBOL(ip_frag_init);
665 
666 static void ip_frag_ipcb(struct sk_buff *from, struct sk_buff *to,
667                          bool first_frag, struct ip_frag_state *state)
668 {
669         /* Copy the flags to each fragment. */
670         IPCB(to)->flags = IPCB(from)->flags;
671 
672         /* ANK: dirty, but effective trick. Upgrade options only if
673          * the segment to be fragmented was THE FIRST (otherwise,
674          * options are already fixed) and make it ONCE
675          * on the initial skb, so that all the following fragments
676          * will inherit fixed options.
677          */
678         if (first_frag)
679                 ip_options_fragment(from);
680 }
681 
682 struct sk_buff *ip_frag_next(struct sk_buff *skb, struct ip_frag_state *state)
683 {
684         unsigned int len = state->left;
685         struct sk_buff *skb2;
686         struct iphdr *iph;
687 
688         len = state->left;
689         /* IF: it doesn't fit, use 'mtu' - the data space left */
690         if (len > state->mtu)
691                 len = state->mtu;
692         /* IF: we are not sending up to and including the packet end
693            then align the next start on an eight byte boundary */
694         if (len < state->left)  {
695                 len &= ~7;
696         }
697 
698         /* Allocate buffer */
699         skb2 = alloc_skb(len + state->hlen + state->ll_rs, GFP_ATOMIC);
700         if (!skb2)
701                 return ERR_PTR(-ENOMEM);
702 
703         /*
704          *      Set up data on packet
705          */
706 
707         ip_copy_metadata(skb2, skb);
708         skb_reserve(skb2, state->ll_rs);
709         skb_put(skb2, len + state->hlen);
710         skb_reset_network_header(skb2);
711         skb2->transport_header = skb2->network_header + state->hlen;
712 
713         /*
714          *      Charge the memory for the fragment to any owner
715          *      it might possess
716          */
717 
718         if (skb->sk)
719                 skb_set_owner_w(skb2, skb->sk);
720 
721         /*
722          *      Copy the packet header into the new buffer.
723          */
724 
725         skb_copy_from_linear_data(skb, skb_network_header(skb2), state->hlen);
726 
727         /*
728          *      Copy a block of the IP datagram.
729          */
730         if (skb_copy_bits(skb, state->ptr, skb_transport_header(skb2), len))
731                 BUG();
732         state->left -= len;
733 
734         /*
735          *      Fill in the new header fields.
736          */
737         iph = ip_hdr(skb2);
738         iph->frag_off = htons((state->offset >> 3));
739         if (state->DF)
740                 iph->frag_off |= htons(IP_DF);
741 
742         /*
743          *      Added AC : If we are fragmenting a fragment that's not the
744          *                 last fragment then keep MF on each bit
745          */
746         if (state->left > 0 || state->not_last_frag)
747                 iph->frag_off |= htons(IP_MF);
748         state->ptr += len;
749         state->offset += len;
750 
751         iph->tot_len = htons(len + state->hlen);
752 
753         ip_send_check(iph);
754 
755         return skb2;
756 }
757 EXPORT_SYMBOL(ip_frag_next);
758 
759 /*
760  *      This IP datagram is too large to be sent in one piece.  Break it up into
761  *      smaller pieces (each of size equal to IP header plus
762  *      a block of the data of the original IP data part) that will yet fit in a
763  *      single device frame, and queue such a frame for sending.
764  */
765 
766 int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
767                    int (*output)(struct net *, struct sock *, struct sk_buff *))
768 {
769         struct iphdr *iph;
770         struct sk_buff *skb2;
771         struct rtable *rt = skb_rtable(skb);
772         unsigned int mtu, hlen, ll_rs;
773         struct ip_fraglist_iter iter;
774         ktime_t tstamp = skb->tstamp;
775         struct ip_frag_state state;
776         int err = 0;
777 
778         /* for offloaded checksums cleanup checksum before fragmentation */
779         if (skb->ip_summed == CHECKSUM_PARTIAL &&
780             (err = skb_checksum_help(skb)))
781                 goto fail;
782 
783         /*
784          *      Point into the IP datagram header.
785          */
786 
787         iph = ip_hdr(skb);
788 
789         mtu = ip_skb_dst_mtu(sk, skb);
790         if (IPCB(skb)->frag_max_size && IPCB(skb)->frag_max_size < mtu)
791                 mtu = IPCB(skb)->frag_max_size;
792 
793         /*
794          *      Setup starting values.
795          */
796 
797         hlen = iph->ihl * 4;
798         mtu = mtu - hlen;       /* Size of data space */
799         IPCB(skb)->flags |= IPSKB_FRAG_COMPLETE;
800         ll_rs = LL_RESERVED_SPACE(rt->dst.dev);
801 
802         /* When frag_list is given, use it. First, check its validity:
803          * some transformers could create wrong frag_list or break existing
804          * one, it is not prohibited. In this case fall back to copying.
805          *
806          * LATER: this step can be merged to real generation of fragments,
807          * we can switch to copy when see the first bad fragment.
808          */
809         if (skb_has_frag_list(skb)) {
810                 struct sk_buff *frag, *frag2;
811                 unsigned int first_len = skb_pagelen(skb);
812 
813                 if (first_len - hlen > mtu ||
814                     ((first_len - hlen) & 7) ||
815                     ip_is_fragment(iph) ||
816                     skb_cloned(skb) ||
817                     skb_headroom(skb) < ll_rs)
818                         goto slow_path;
819 
820                 skb_walk_frags(skb, frag) {
821                         /* Correct geometry. */
822                         if (frag->len > mtu ||
823                             ((frag->len & 7) && frag->next) ||
824                             skb_headroom(frag) < hlen + ll_rs)
825                                 goto slow_path_clean;
826 
827                         /* Partially cloned skb? */
828                         if (skb_shared(frag))
829                                 goto slow_path_clean;
830 
831                         BUG_ON(frag->sk);
832                         if (skb->sk) {
833                                 frag->sk = skb->sk;
834                                 frag->destructor = sock_wfree;
835                         }
836                         skb->truesize -= frag->truesize;
837                 }
838 
839                 /* Everything is OK. Generate! */
840                 ip_fraglist_init(skb, iph, hlen, &iter);
841 
842                 for (;;) {
843                         /* Prepare header of the next frame,
844                          * before previous one went down. */
845                         if (iter.frag) {
846                                 ip_fraglist_ipcb_prepare(skb, &iter);
847                                 ip_fraglist_prepare(skb, &iter);
848                         }
849 
850                         skb->tstamp = tstamp;
851                         err = output(net, sk, skb);
852 
853                         if (!err)
854                                 IP_INC_STATS(net, IPSTATS_MIB_FRAGCREATES);
855                         if (err || !iter.frag)
856                                 break;
857 
858                         skb = ip_fraglist_next(&iter);
859                 }
860 
861                 if (err == 0) {
862                         IP_INC_STATS(net, IPSTATS_MIB_FRAGOKS);
863                         return 0;
864                 }
865 
866                 kfree_skb_list(iter.frag);
867 
868                 IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
869                 return err;
870 
871 slow_path_clean:
872                 skb_walk_frags(skb, frag2) {
873                         if (frag2 == frag)
874                                 break;
875                         frag2->sk = NULL;
876                         frag2->destructor = NULL;
877                         skb->truesize += frag2->truesize;
878                 }
879         }
880 
881 slow_path:
882         /*
883          *      Fragment the datagram.
884          */
885 
886         ip_frag_init(skb, hlen, ll_rs, mtu, IPCB(skb)->flags & IPSKB_FRAG_PMTU,
887                      &state);
888 
889         /*
890          *      Keep copying data until we run out.
891          */
892 
893         while (state.left > 0) {
894                 bool first_frag = (state.offset == 0);
895 
896                 skb2 = ip_frag_next(skb, &state);
897                 if (IS_ERR(skb2)) {
898                         err = PTR_ERR(skb2);
899                         goto fail;
900                 }
901                 ip_frag_ipcb(skb, skb2, first_frag, &state);
902 
903                 /*
904                  *      Put this fragment into the sending queue.
905                  */
906                 skb2->tstamp = tstamp;
907                 err = output(net, sk, skb2);
908                 if (err)
909                         goto fail;
910 
911                 IP_INC_STATS(net, IPSTATS_MIB_FRAGCREATES);
912         }
913         consume_skb(skb);
914         IP_INC_STATS(net, IPSTATS_MIB_FRAGOKS);
915         return err;
916 
917 fail:
918         kfree_skb(skb);
919         IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
920         return err;
921 }
922 EXPORT_SYMBOL(ip_do_fragment);
923 
924 int
925 ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
926 {
927         struct msghdr *msg = from;
928 
929         if (skb->ip_summed == CHECKSUM_PARTIAL) {
930                 if (!copy_from_iter_full(to, len, &msg->msg_iter))
931                         return -EFAULT;
932         } else {
933                 __wsum csum = 0;
934                 if (!csum_and_copy_from_iter_full(to, len, &csum, &msg->msg_iter))
935                         return -EFAULT;
936                 skb->csum = csum_block_add(skb->csum, csum, odd);
937         }
938         return 0;
939 }
940 EXPORT_SYMBOL(ip_generic_getfrag);
941 
942 static inline __wsum
943 csum_page(struct page *page, int offset, int copy)
944 {
945         char *kaddr;
946         __wsum csum;
947         kaddr = kmap(page);
948         csum = csum_partial(kaddr + offset, copy, 0);
949         kunmap(page);
950         return csum;
951 }
952 
953 static int __ip_append_data(struct sock *sk,
954                             struct flowi4 *fl4,
955                             struct sk_buff_head *queue,
956                             struct inet_cork *cork,
957                             struct page_frag *pfrag,
958                             int getfrag(void *from, char *to, int offset,
959                                         int len, int odd, struct sk_buff *skb),
960                             void *from, int length, int transhdrlen,
961                             unsigned int flags)
962 {
963         struct inet_sock *inet = inet_sk(sk);
964         struct ubuf_info *uarg = NULL;
965         struct sk_buff *skb;
966 
967         struct ip_options *opt = cork->opt;
968         int hh_len;
969         int exthdrlen;
970         int mtu;
971         int copy;
972         int err;
973         int offset = 0;
974         unsigned int maxfraglen, fragheaderlen, maxnonfragsize;
975         int csummode = CHECKSUM_NONE;
976         struct rtable *rt = (struct rtable *)cork->dst;
977         unsigned int wmem_alloc_delta = 0;
978         bool paged, extra_uref = false;
979         u32 tskey = 0;
980 
981         skb = skb_peek_tail(queue);
982 
983         exthdrlen = !skb ? rt->dst.header_len : 0;
984         mtu = cork->gso_size ? IP_MAX_MTU : cork->fragsize;
985         paged = !!cork->gso_size;
986 
987         if (cork->tx_flags & SKBTX_ANY_SW_TSTAMP &&
988             sk->sk_tsflags & SOF_TIMESTAMPING_OPT_ID)
989                 tskey = sk->sk_tskey++;
990 
991         hh_len = LL_RESERVED_SPACE(rt->dst.dev);
992 
993         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
994         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
995         maxnonfragsize = ip_sk_ignore_df(sk) ? 0xFFFF : mtu;
996 
997         if (cork->length + length > maxnonfragsize - fragheaderlen) {
998                 ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
999                                mtu - (opt ? opt->optlen : 0));
1000                 return -EMSGSIZE;
1001         }
1002 
1003         /*
1004          * transhdrlen > 0 means that this is the first fragment and we wish
1005          * it won't be fragmented in the future.
1006          */
1007         if (transhdrlen &&
1008             length + fragheaderlen <= mtu &&
1009             rt->dst.dev->features & (NETIF_F_HW_CSUM | NETIF_F_IP_CSUM) &&
1010             (!(flags & MSG_MORE) || cork->gso_size) &&
1011             (!exthdrlen || (rt->dst.dev->features & NETIF_F_HW_ESP_TX_CSUM)))
1012                 csummode = CHECKSUM_PARTIAL;
1013 
1014         if (flags & MSG_ZEROCOPY && length && sock_flag(sk, SOCK_ZEROCOPY)) {
1015                 uarg = sock_zerocopy_realloc(sk, length, skb_zcopy(skb));
1016                 if (!uarg)
1017                         return -ENOBUFS;
1018                 extra_uref = !skb_zcopy(skb);   /* only ref on new uarg */
1019                 if (rt->dst.dev->features & NETIF_F_SG &&
1020                     csummode == CHECKSUM_PARTIAL) {
1021                         paged = true;
1022                 } else {
1023                         uarg->zerocopy = 0;
1024                         skb_zcopy_set(skb, uarg, &extra_uref);
1025                 }
1026         }
1027 
1028         cork->length += length;
1029 
1030         /* So, what's going on in the loop below?
1031          *
1032          * We use calculated fragment length to generate chained skb,
1033          * each of segments is IP fragment ready for sending to network after
1034          * adding appropriate IP header.
1035          */
1036 
1037         if (!skb)
1038                 goto alloc_new_skb;
1039 
1040         while (length > 0) {
1041                 /* Check if the remaining data fits into current packet. */
1042                 copy = mtu - skb->len;
1043                 if (copy < length)
1044                         copy = maxfraglen - skb->len;
1045                 if (copy <= 0) {
1046                         char *data;
1047                         unsigned int datalen;
1048                         unsigned int fraglen;
1049                         unsigned int fraggap;
1050                         unsigned int alloclen;
1051                         unsigned int pagedlen;
1052                         struct sk_buff *skb_prev;
1053 alloc_new_skb:
1054                         skb_prev = skb;
1055                         if (skb_prev)
1056                                 fraggap = skb_prev->len - maxfraglen;
1057                         else
1058                                 fraggap = 0;
1059 
1060                         /*
1061                          * If remaining data exceeds the mtu,
1062                          * we know we need more fragment(s).
1063                          */
1064                         datalen = length + fraggap;
1065                         if (datalen > mtu - fragheaderlen)
1066                                 datalen = maxfraglen - fragheaderlen;
1067                         fraglen = datalen + fragheaderlen;
1068                         pagedlen = 0;
1069 
1070                         if ((flags & MSG_MORE) &&
1071                             !(rt->dst.dev->features&NETIF_F_SG))
1072                                 alloclen = mtu;
1073                         else if (!paged)
1074                                 alloclen = fraglen;
1075                         else {
1076                                 alloclen = min_t(int, fraglen, MAX_HEADER);
1077                                 pagedlen = fraglen - alloclen;
1078                         }
1079 
1080                         alloclen += exthdrlen;
1081 
1082                         /* The last fragment gets additional space at tail.
1083                          * Note, with MSG_MORE we overallocate on fragments,
1084                          * because we have no idea what fragment will be
1085                          * the last.
1086                          */
1087                         if (datalen == length + fraggap)
1088                                 alloclen += rt->dst.trailer_len;
1089 
1090                         if (transhdrlen) {
1091                                 skb = sock_alloc_send_skb(sk,
1092                                                 alloclen + hh_len + 15,
1093                                                 (flags & MSG_DONTWAIT), &err);
1094                         } else {
1095                                 skb = NULL;
1096                                 if (refcount_read(&sk->sk_wmem_alloc) + wmem_alloc_delta <=
1097                                     2 * sk->sk_sndbuf)
1098                                         skb = alloc_skb(alloclen + hh_len + 15,
1099                                                         sk->sk_allocation);
1100                                 if (unlikely(!skb))
1101                                         err = -ENOBUFS;
1102                         }
1103                         if (!skb)
1104                                 goto error;
1105 
1106                         /*
1107                          *      Fill in the control structures
1108                          */
1109                         skb->ip_summed = csummode;
1110                         skb->csum = 0;
1111                         skb_reserve(skb, hh_len);
1112 
1113                         /*
1114                          *      Find where to start putting bytes.
1115                          */
1116                         data = skb_put(skb, fraglen + exthdrlen - pagedlen);
1117                         skb_set_network_header(skb, exthdrlen);
1118                         skb->transport_header = (skb->network_header +
1119                                                  fragheaderlen);
1120                         data += fragheaderlen + exthdrlen;
1121 
1122                         if (fraggap) {
1123                                 skb->csum = skb_copy_and_csum_bits(
1124                                         skb_prev, maxfraglen,
1125                                         data + transhdrlen, fraggap, 0);
1126                                 skb_prev->csum = csum_sub(skb_prev->csum,
1127                                                           skb->csum);
1128                                 data += fraggap;
1129                                 pskb_trim_unique(skb_prev, maxfraglen);
1130                         }
1131 
1132                         copy = datalen - transhdrlen - fraggap - pagedlen;
1133                         if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
1134                                 err = -EFAULT;
1135                                 kfree_skb(skb);
1136                                 goto error;
1137                         }
1138 
1139                         offset += copy;
1140                         length -= copy + transhdrlen;
1141                         transhdrlen = 0;
1142                         exthdrlen = 0;
1143                         csummode = CHECKSUM_NONE;
1144 
1145                         /* only the initial fragment is time stamped */
1146                         skb_shinfo(skb)->tx_flags = cork->tx_flags;
1147                         cork->tx_flags = 0;
1148                         skb_shinfo(skb)->tskey = tskey;
1149                         tskey = 0;
1150                         skb_zcopy_set(skb, uarg, &extra_uref);
1151 
1152                         if ((flags & MSG_CONFIRM) && !skb_prev)
1153                                 skb_set_dst_pending_confirm(skb, 1);
1154 
1155                         /*
1156                          * Put the packet on the pending queue.
1157                          */
1158                         if (!skb->destructor) {
1159                                 skb->destructor = sock_wfree;
1160                                 skb->sk = sk;
1161                                 wmem_alloc_delta += skb->truesize;
1162                         }
1163                         __skb_queue_tail(queue, skb);
1164                         continue;
1165                 }
1166 
1167                 if (copy > length)
1168                         copy = length;
1169 
1170                 if (!(rt->dst.dev->features&NETIF_F_SG) &&
1171                     skb_tailroom(skb) >= copy) {
1172                         unsigned int off;
1173 
1174                         off = skb->len;
1175                         if (getfrag(from, skb_put(skb, copy),
1176                                         offset, copy, off, skb) < 0) {
1177                                 __skb_trim(skb, off);
1178                                 err = -EFAULT;
1179                                 goto error;
1180                         }
1181                 } else if (!uarg || !uarg->zerocopy) {
1182                         int i = skb_shinfo(skb)->nr_frags;
1183 
1184                         err = -ENOMEM;
1185                         if (!sk_page_frag_refill(sk, pfrag))
1186                                 goto error;
1187 
1188                         if (!skb_can_coalesce(skb, i, pfrag->page,
1189                                               pfrag->offset)) {
1190                                 err = -EMSGSIZE;
1191                                 if (i == MAX_SKB_FRAGS)
1192                                         goto error;
1193 
1194                                 __skb_fill_page_desc(skb, i, pfrag->page,
1195                                                      pfrag->offset, 0);
1196                                 skb_shinfo(skb)->nr_frags = ++i;
1197                                 get_page(pfrag->page);
1198                         }
1199                         copy = min_t(int, copy, pfrag->size - pfrag->offset);
1200                         if (getfrag(from,
1201                                     page_address(pfrag->page) + pfrag->offset,
1202                                     offset, copy, skb->len, skb) < 0)
1203                                 goto error_efault;
1204 
1205                         pfrag->offset += copy;
1206                         skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
1207                         skb->len += copy;
1208                         skb->data_len += copy;
1209                         skb->truesize += copy;
1210                         wmem_alloc_delta += copy;
1211                 } else {
1212                         err = skb_zerocopy_iter_dgram(skb, from, copy);
1213                         if (err < 0)
1214                                 goto error;
1215                 }
1216                 offset += copy;
1217                 length -= copy;
1218         }
1219 
1220         if (wmem_alloc_delta)
1221                 refcount_add(wmem_alloc_delta, &sk->sk_wmem_alloc);
1222         return 0;
1223 
1224 error_efault:
1225         err = -EFAULT;
1226 error:
1227         if (uarg)
1228                 sock_zerocopy_put_abort(uarg, extra_uref);
1229         cork->length -= length;
1230         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1231         refcount_add(wmem_alloc_delta, &sk->sk_wmem_alloc);
1232         return err;
1233 }
1234 
1235 static int ip_setup_cork(struct sock *sk, struct inet_cork *cork,
1236                          struct ipcm_cookie *ipc, struct rtable **rtp)
1237 {
1238         struct ip_options_rcu *opt;
1239         struct rtable *rt;
1240 
1241         rt = *rtp;
1242         if (unlikely(!rt))
1243                 return -EFAULT;
1244 
1245         /*
1246          * setup for corking.
1247          */
1248         opt = ipc->opt;
1249         if (opt) {
1250                 if (!cork->opt) {
1251                         cork->opt = kmalloc(sizeof(struct ip_options) + 40,
1252                                             sk->sk_allocation);
1253                         if (unlikely(!cork->opt))
1254                                 return -ENOBUFS;
1255                 }
1256                 memcpy(cork->opt, &opt->opt, sizeof(struct ip_options) + opt->opt.optlen);
1257                 cork->flags |= IPCORK_OPT;
1258                 cork->addr = ipc->addr;
1259         }
1260 
1261         cork->fragsize = ip_sk_use_pmtu(sk) ?
1262                          dst_mtu(&rt->dst) : READ_ONCE(rt->dst.dev->mtu);
1263 
1264         if (!inetdev_valid_mtu(cork->fragsize))
1265                 return -ENETUNREACH;
1266 
1267         cork->gso_size = ipc->gso_size;
1268 
1269         cork->dst = &rt->dst;
1270         /* We stole this route, caller should not release it. */
1271         *rtp = NULL;
1272 
1273         cork->length = 0;
1274         cork->ttl = ipc->ttl;
1275         cork->tos = ipc->tos;
1276         cork->priority = ipc->priority;
1277         cork->transmit_time = ipc->sockc.transmit_time;
1278         cork->tx_flags = 0;
1279         sock_tx_timestamp(sk, ipc->sockc.tsflags, &cork->tx_flags);
1280 
1281         return 0;
1282 }
1283 
1284 /*
1285  *      ip_append_data() and ip_append_page() can make one large IP datagram
1286  *      from many pieces of data. Each pieces will be holded on the socket
1287  *      until ip_push_pending_frames() is called. Each piece can be a page
1288  *      or non-page data.
1289  *
1290  *      Not only UDP, other transport protocols - e.g. raw sockets - can use
1291  *      this interface potentially.
1292  *
1293  *      LATER: length must be adjusted by pad at tail, when it is required.
1294  */
1295 int ip_append_data(struct sock *sk, struct flowi4 *fl4,
1296                    int getfrag(void *from, char *to, int offset, int len,
1297                                int odd, struct sk_buff *skb),
1298                    void *from, int length, int transhdrlen,
1299                    struct ipcm_cookie *ipc, struct rtable **rtp,
1300                    unsigned int flags)
1301 {
1302         struct inet_sock *inet = inet_sk(sk);
1303         int err;
1304 
1305         if (flags&MSG_PROBE)
1306                 return 0;
1307 
1308         if (skb_queue_empty(&sk->sk_write_queue)) {
1309                 err = ip_setup_cork(sk, &inet->cork.base, ipc, rtp);
1310                 if (err)
1311                         return err;
1312         } else {
1313                 transhdrlen = 0;
1314         }
1315 
1316         return __ip_append_data(sk, fl4, &sk->sk_write_queue, &inet->cork.base,
1317                                 sk_page_frag(sk), getfrag,
1318                                 from, length, transhdrlen, flags);
1319 }
1320 
1321 ssize_t ip_append_page(struct sock *sk, struct flowi4 *fl4, struct page *page,
1322                        int offset, size_t size, int flags)
1323 {
1324         struct inet_sock *inet = inet_sk(sk);
1325         struct sk_buff *skb;
1326         struct rtable *rt;
1327         struct ip_options *opt = NULL;
1328         struct inet_cork *cork;
1329         int hh_len;
1330         int mtu;
1331         int len;
1332         int err;
1333         unsigned int maxfraglen, fragheaderlen, fraggap, maxnonfragsize;
1334 
1335         if (inet->hdrincl)
1336                 return -EPERM;
1337 
1338         if (flags&MSG_PROBE)
1339                 return 0;
1340 
1341         if (skb_queue_empty(&sk->sk_write_queue))
1342                 return -EINVAL;
1343 
1344         cork = &inet->cork.base;
1345         rt = (struct rtable *)cork->dst;
1346         if (cork->flags & IPCORK_OPT)
1347                 opt = cork->opt;
1348 
1349         if (!(rt->dst.dev->features&NETIF_F_SG))
1350                 return -EOPNOTSUPP;
1351 
1352         hh_len = LL_RESERVED_SPACE(rt->dst.dev);
1353         mtu = cork->gso_size ? IP_MAX_MTU : cork->fragsize;
1354 
1355         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
1356         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
1357         maxnonfragsize = ip_sk_ignore_df(sk) ? 0xFFFF : mtu;
1358 
1359         if (cork->length + size > maxnonfragsize - fragheaderlen) {
1360                 ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
1361                                mtu - (opt ? opt->optlen : 0));
1362                 return -EMSGSIZE;
1363         }
1364 
1365         skb = skb_peek_tail(&sk->sk_write_queue);
1366         if (!skb)
1367                 return -EINVAL;
1368 
1369         cork->length += size;
1370 
1371         while (size > 0) {
1372                 /* Check if the remaining data fits into current packet. */
1373                 len = mtu - skb->len;
1374                 if (len < size)
1375                         len = maxfraglen - skb->len;
1376 
1377                 if (len <= 0) {
1378                         struct sk_buff *skb_prev;
1379                         int alloclen;
1380 
1381                         skb_prev = skb;
1382                         fraggap = skb_prev->len - maxfraglen;
1383 
1384                         alloclen = fragheaderlen + hh_len + fraggap + 15;
1385                         skb = sock_wmalloc(sk, alloclen, 1, sk->sk_allocation);
1386                         if (unlikely(!skb)) {
1387                                 err = -ENOBUFS;
1388                                 goto error;
1389                         }
1390 
1391                         /*
1392                          *      Fill in the control structures
1393                          */
1394                         skb->ip_summed = CHECKSUM_NONE;
1395                         skb->csum = 0;
1396                         skb_reserve(skb, hh_len);
1397 
1398                         /*
1399                          *      Find where to start putting bytes.
1400                          */
1401                         skb_put(skb, fragheaderlen + fraggap);
1402                         skb_reset_network_header(skb);
1403                         skb->transport_header = (skb->network_header +
1404                                                  fragheaderlen);
1405                         if (fraggap) {
1406                                 skb->csum = skb_copy_and_csum_bits(skb_prev,
1407                                                                    maxfraglen,
1408                                                     skb_transport_header(skb),
1409                                                                    fraggap, 0);
1410                                 skb_prev->csum = csum_sub(skb_prev->csum,
1411                                                           skb->csum);
1412                                 pskb_trim_unique(skb_prev, maxfraglen);
1413                         }
1414 
1415                         /*
1416                          * Put the packet on the pending queue.
1417                          */
1418                         __skb_queue_tail(&sk->sk_write_queue, skb);
1419                         continue;
1420                 }
1421 
1422                 if (len > size)
1423                         len = size;
1424 
1425                 if (skb_append_pagefrags(skb, page, offset, len)) {
1426                         err = -EMSGSIZE;
1427                         goto error;
1428                 }
1429 
1430                 if (skb->ip_summed == CHECKSUM_NONE) {
1431                         __wsum csum;
1432                         csum = csum_page(page, offset, len);
1433                         skb->csum = csum_block_add(skb->csum, csum, skb->len);
1434                 }
1435 
1436                 skb->len += len;
1437                 skb->data_len += len;
1438                 skb->truesize += len;
1439                 refcount_add(len, &sk->sk_wmem_alloc);
1440                 offset += len;
1441                 size -= len;
1442         }
1443         return 0;
1444 
1445 error:
1446         cork->length -= size;
1447         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1448         return err;
1449 }
1450 
1451 static void ip_cork_release(struct inet_cork *cork)
1452 {
1453         cork->flags &= ~IPCORK_OPT;
1454         kfree(cork->opt);
1455         cork->opt = NULL;
1456         dst_release(cork->dst);
1457         cork->dst = NULL;
1458 }
1459 
1460 /*
1461  *      Combined all pending IP fragments on the socket as one IP datagram
1462  *      and push them out.
1463  */
1464 struct sk_buff *__ip_make_skb(struct sock *sk,
1465                               struct flowi4 *fl4,
1466                               struct sk_buff_head *queue,
1467                               struct inet_cork *cork)
1468 {
1469         struct sk_buff *skb, *tmp_skb;
1470         struct sk_buff **tail_skb;
1471         struct inet_sock *inet = inet_sk(sk);
1472         struct net *net = sock_net(sk);
1473         struct ip_options *opt = NULL;
1474         struct rtable *rt = (struct rtable *)cork->dst;
1475         struct iphdr *iph;
1476         __be16 df = 0;
1477         __u8 ttl;
1478 
1479         skb = __skb_dequeue(queue);
1480         if (!skb)
1481                 goto out;
1482         tail_skb = &(skb_shinfo(skb)->frag_list);
1483 
1484         /* move skb->data to ip header from ext header */
1485         if (skb->data < skb_network_header(skb))
1486                 __skb_pull(skb, skb_network_offset(skb));
1487         while ((tmp_skb = __skb_dequeue(queue)) != NULL) {
1488                 __skb_pull(tmp_skb, skb_network_header_len(skb));
1489                 *tail_skb = tmp_skb;
1490                 tail_skb = &(tmp_skb->next);
1491                 skb->len += tmp_skb->len;
1492                 skb->data_len += tmp_skb->len;
1493                 skb->truesize += tmp_skb->truesize;
1494                 tmp_skb->destructor = NULL;
1495                 tmp_skb->sk = NULL;
1496         }
1497 
1498         /* Unless user demanded real pmtu discovery (IP_PMTUDISC_DO), we allow
1499          * to fragment the frame generated here. No matter, what transforms
1500          * how transforms change size of the packet, it will come out.
1501          */
1502         skb->ignore_df = ip_sk_ignore_df(sk);
1503 
1504         /* DF bit is set when we want to see DF on outgoing frames.
1505          * If ignore_df is set too, we still allow to fragment this frame
1506          * locally. */
1507         if (inet->pmtudisc == IP_PMTUDISC_DO ||
1508             inet->pmtudisc == IP_PMTUDISC_PROBE ||
1509             (skb->len <= dst_mtu(&rt->dst) &&
1510              ip_dont_fragment(sk, &rt->dst)))
1511                 df = htons(IP_DF);
1512 
1513         if (cork->flags & IPCORK_OPT)
1514                 opt = cork->opt;
1515 
1516         if (cork->ttl != 0)
1517                 ttl = cork->ttl;
1518         else if (rt->rt_type == RTN_MULTICAST)
1519                 ttl = inet->mc_ttl;
1520         else
1521                 ttl = ip_select_ttl(inet, &rt->dst);
1522 
1523         iph = ip_hdr(skb);
1524         iph->version = 4;
1525         iph->ihl = 5;
1526         iph->tos = (cork->tos != -1) ? cork->tos : inet->tos;
1527         iph->frag_off = df;
1528         iph->ttl = ttl;
1529         iph->protocol = sk->sk_protocol;
1530         ip_copy_addrs(iph, fl4);
1531         ip_select_ident(net, skb, sk);
1532 
1533         if (opt) {
1534                 iph->ihl += opt->optlen>>2;
1535                 ip_options_build(skb, opt, cork->addr, rt, 0);
1536         }
1537 
1538         skb->priority = (cork->tos != -1) ? cork->priority: sk->sk_priority;
1539         skb->mark = sk->sk_mark;
1540         skb->tstamp = cork->transmit_time;
1541         /*
1542          * Steal rt from cork.dst to avoid a pair of atomic_inc/atomic_dec
1543          * on dst refcount
1544          */
1545         cork->dst = NULL;
1546         skb_dst_set(skb, &rt->dst);
1547 
1548         if (iph->protocol == IPPROTO_ICMP)
1549                 icmp_out_count(net, ((struct icmphdr *)
1550                         skb_transport_header(skb))->type);
1551 
1552         ip_cork_release(cork);
1553 out:
1554         return skb;
1555 }
1556 
1557 int ip_send_skb(struct net *net, struct sk_buff *skb)
1558 {
1559         int err;
1560 
1561         err = ip_local_out(net, skb->sk, skb);
1562         if (err) {
1563                 if (err > 0)
1564                         err = net_xmit_errno(err);
1565                 if (err)
1566                         IP_INC_STATS(net, IPSTATS_MIB_OUTDISCARDS);
1567         }
1568 
1569         return err;
1570 }
1571 
1572 int ip_push_pending_frames(struct sock *sk, struct flowi4 *fl4)
1573 {
1574         struct sk_buff *skb;
1575 
1576         skb = ip_finish_skb(sk, fl4);
1577         if (!skb)
1578                 return 0;
1579 
1580         /* Netfilter gets whole the not fragmented skb. */
1581         return ip_send_skb(sock_net(sk), skb);
1582 }
1583 
1584 /*
1585  *      Throw away all pending data on the socket.
1586  */
1587 static void __ip_flush_pending_frames(struct sock *sk,
1588                                       struct sk_buff_head *queue,
1589                                       struct inet_cork *cork)
1590 {
1591         struct sk_buff *skb;
1592 
1593         while ((skb = __skb_dequeue_tail(queue)) != NULL)
1594                 kfree_skb(skb);
1595 
1596         ip_cork_release(cork);
1597 }
1598 
1599 void ip_flush_pending_frames(struct sock *sk)
1600 {
1601         __ip_flush_pending_frames(sk, &sk->sk_write_queue, &inet_sk(sk)->cork.base);
1602 }
1603 
1604 struct sk_buff *ip_make_skb(struct sock *sk,
1605                             struct flowi4 *fl4,
1606                             int getfrag(void *from, char *to, int offset,
1607                                         int len, int odd, struct sk_buff *skb),
1608                             void *from, int length, int transhdrlen,
1609                             struct ipcm_cookie *ipc, struct rtable **rtp,
1610                             struct inet_cork *cork, unsigned int flags)
1611 {
1612         struct sk_buff_head queue;
1613         int err;
1614 
1615         if (flags & MSG_PROBE)
1616                 return NULL;
1617 
1618         __skb_queue_head_init(&queue);
1619 
1620         cork->flags = 0;
1621         cork->addr = 0;
1622         cork->opt = NULL;
1623         err = ip_setup_cork(sk, cork, ipc, rtp);
1624         if (err)
1625                 return ERR_PTR(err);
1626 
1627         err = __ip_append_data(sk, fl4, &queue, cork,
1628                                &current->task_frag, getfrag,
1629                                from, length, transhdrlen, flags);
1630         if (err) {
1631                 __ip_flush_pending_frames(sk, &queue, cork);
1632                 return ERR_PTR(err);
1633         }
1634 
1635         return __ip_make_skb(sk, fl4, &queue, cork);
1636 }
1637 
1638 /*
1639  *      Fetch data from kernel space and fill in checksum if needed.
1640  */
1641 static int ip_reply_glue_bits(void *dptr, char *to, int offset,
1642                               int len, int odd, struct sk_buff *skb)
1643 {
1644         __wsum csum;
1645 
1646         csum = csum_partial_copy_nocheck(dptr+offset, to, len, 0);
1647         skb->csum = csum_block_add(skb->csum, csum, odd);
1648         return 0;
1649 }
1650 
1651 /*
1652  *      Generic function to send a packet as reply to another packet.
1653  *      Used to send some TCP resets/acks so far.
1654  */
1655 void ip_send_unicast_reply(struct sock *sk, struct sk_buff *skb,
1656                            const struct ip_options *sopt,
1657                            __be32 daddr, __be32 saddr,
1658                            const struct ip_reply_arg *arg,
1659                            unsigned int len, u64 transmit_time)
1660 {
1661         struct ip_options_data replyopts;
1662         struct ipcm_cookie ipc;
1663         struct flowi4 fl4;
1664         struct rtable *rt = skb_rtable(skb);
1665         struct net *net = sock_net(sk);
1666         struct sk_buff *nskb;
1667         int err;
1668         int oif;
1669 
1670         if (__ip_options_echo(net, &replyopts.opt.opt, skb, sopt))
1671                 return;
1672 
1673         ipcm_init(&ipc);
1674         ipc.addr = daddr;
1675         ipc.sockc.transmit_time = transmit_time;
1676 
1677         if (replyopts.opt.opt.optlen) {
1678                 ipc.opt = &replyopts.opt;
1679 
1680                 if (replyopts.opt.opt.srr)
1681                         daddr = replyopts.opt.opt.faddr;
1682         }
1683 
1684         oif = arg->bound_dev_if;
1685         if (!oif && netif_index_is_l3_master(net, skb->skb_iif))
1686                 oif = skb->skb_iif;
1687 
1688         flowi4_init_output(&fl4, oif,
1689                            IP4_REPLY_MARK(net, skb->mark) ?: sk->sk_mark,
1690                            RT_TOS(arg->tos),
1691                            RT_SCOPE_UNIVERSE, ip_hdr(skb)->protocol,
1692                            ip_reply_arg_flowi_flags(arg),
1693                            daddr, saddr,
1694                            tcp_hdr(skb)->source, tcp_hdr(skb)->dest,
1695                            arg->uid);
1696         security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
1697         rt = ip_route_output_key(net, &fl4);
1698         if (IS_ERR(rt))
1699                 return;
1700 
1701         inet_sk(sk)->tos = arg->tos;
1702 
1703         sk->sk_priority = skb->priority;
1704         sk->sk_protocol = ip_hdr(skb)->protocol;
1705         sk->sk_bound_dev_if = arg->bound_dev_if;
1706         sk->sk_sndbuf = sysctl_wmem_default;
1707         sk->sk_mark = fl4.flowi4_mark;
1708         err = ip_append_data(sk, &fl4, ip_reply_glue_bits, arg->iov->iov_base,
1709                              len, 0, &ipc, &rt, MSG_DONTWAIT);
1710         if (unlikely(err)) {
1711                 ip_flush_pending_frames(sk);
1712                 goto out;
1713         }
1714 
1715         nskb = skb_peek(&sk->sk_write_queue);
1716         if (nskb) {
1717                 if (arg->csumoffset >= 0)
1718                         *((__sum16 *)skb_transport_header(nskb) +
1719                           arg->csumoffset) = csum_fold(csum_add(nskb->csum,
1720                                                                 arg->csum));
1721                 nskb->ip_summed = CHECKSUM_NONE;
1722                 ip_push_pending_frames(sk, &fl4);
1723         }
1724 out:
1725         ip_rt_put(rt);
1726 }
1727 
1728 void __init ip_init(void)
1729 {
1730         ip_rt_init();
1731         inet_initpeers();
1732 
1733 #if defined(CONFIG_IP_MULTICAST)
1734         igmp_mc_init();
1735 #endif
1736 }
1737 

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