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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 readability.
 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/inet_ecn.h>
 78 #include <net/lwtunnel.h>
 79 #include <linux/bpf-cgroup.h>
 80 #include <linux/igmp.h>
 81 #include <linux/netfilter_ipv4.h>
 82 #include <linux/netfilter_bridge.h>
 83 #include <linux/netlink.h>
 84 #include <linux/tcp.h>
 85 
 86 static int
 87 ip_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
 88             unsigned int mtu,
 89             int (*output)(struct net *, struct sock *, struct sk_buff *));
 90 
 91 /* Generate a checksum for an outgoing IP datagram. */
 92 void ip_send_check(struct iphdr *iph)
 93 {
 94         iph->check = 0;
 95         iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
 96 }
 97 EXPORT_SYMBOL(ip_send_check);
 98 
 99 int __ip_local_out(struct net *net, struct sock *sk, struct sk_buff *skb)
100 {
101         struct iphdr *iph = ip_hdr(skb);
102 
103         iph->tot_len = htons(skb->len);
104         ip_send_check(iph);
105 
106         /* if egress device is enslaved to an L3 master device pass the
107          * skb to its handler for processing
108          */
109         skb = l3mdev_ip_out(sk, skb);
110         if (unlikely(!skb))
111                 return 0;
112 
113         skb->protocol = htons(ETH_P_IP);
114 
115         return nf_hook(NFPROTO_IPV4, NF_INET_LOCAL_OUT,
116                        net, sk, skb, NULL, skb_dst(skb)->dev,
117                        dst_output);
118 }
119 
120 int ip_local_out(struct net *net, struct sock *sk, struct sk_buff *skb)
121 {
122         int err;
123 
124         err = __ip_local_out(net, sk, skb);
125         if (likely(err == 1))
126                 err = dst_output(net, sk, skb);
127 
128         return err;
129 }
130 EXPORT_SYMBOL_GPL(ip_local_out);
131 
132 static inline int ip_select_ttl(struct inet_sock *inet, struct dst_entry *dst)
133 {
134         int ttl = inet->uc_ttl;
135 
136         if (ttl < 0)
137                 ttl = ip4_dst_hoplimit(dst);
138         return ttl;
139 }
140 
141 /*
142  *              Add an ip header to a skbuff and send it out.
143  *
144  */
145 int ip_build_and_send_pkt(struct sk_buff *skb, const struct sock *sk,
146                           __be32 saddr, __be32 daddr, struct ip_options_rcu *opt,
147                           u8 tos)
148 {
149         struct inet_sock *inet = inet_sk(sk);
150         struct rtable *rt = skb_rtable(skb);
151         struct net *net = sock_net(sk);
152         struct iphdr *iph;
153 
154         /* Build the IP header. */
155         skb_push(skb, sizeof(struct iphdr) + (opt ? opt->opt.optlen : 0));
156         skb_reset_network_header(skb);
157         iph = ip_hdr(skb);
158         iph->version  = 4;
159         iph->ihl      = 5;
160         iph->tos      = tos;
161         iph->ttl      = ip_select_ttl(inet, &rt->dst);
162         iph->daddr    = (opt && opt->opt.srr ? opt->opt.faddr : daddr);
163         iph->saddr    = saddr;
164         iph->protocol = sk->sk_protocol;
165         /* Do not bother generating IPID for small packets (eg SYNACK) */
166         if (skb->len <= IPV4_MIN_MTU || ip_dont_fragment(sk, &rt->dst)) {
167                 iph->frag_off = htons(IP_DF);
168                 iph->id = 0;
169         } else {
170                 iph->frag_off = 0;
171                 /* TCP packets here are SYNACK with fat IPv4/TCP options.
172                  * Avoid using the hashed IP ident generator.
173                  */
174                 if (sk->sk_protocol == IPPROTO_TCP)
175                         iph->id = (__force __be16)prandom_u32();
176                 else
177                         __ip_select_ident(net, iph, 1);
178         }
179 
180         if (opt && opt->opt.optlen) {
181                 iph->ihl += opt->opt.optlen>>2;
182                 ip_options_build(skb, &opt->opt, daddr, rt, 0);
183         }
184 
185         skb->priority = sk->sk_priority;
186         if (!skb->mark)
187                 skb->mark = sk->sk_mark;
188 
189         /* Send it out. */
190         return ip_local_out(net, skb->sk, skb);
191 }
192 EXPORT_SYMBOL_GPL(ip_build_and_send_pkt);
193 
194 static int ip_finish_output2(struct net *net, struct sock *sk, struct sk_buff *skb)
195 {
196         struct dst_entry *dst = skb_dst(skb);
197         struct rtable *rt = (struct rtable *)dst;
198         struct net_device *dev = dst->dev;
199         unsigned int hh_len = LL_RESERVED_SPACE(dev);
200         struct neighbour *neigh;
201         bool is_v6gw = false;
202 
203         if (rt->rt_type == RTN_MULTICAST) {
204                 IP_UPD_PO_STATS(net, IPSTATS_MIB_OUTMCAST, skb->len);
205         } else if (rt->rt_type == RTN_BROADCAST)
206                 IP_UPD_PO_STATS(net, IPSTATS_MIB_OUTBCAST, skb->len);
207 
208         if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) {
209                 skb = skb_expand_head(skb, hh_len);
210                 if (!skb)
211                         return -ENOMEM;
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         struct sk_buff *segs, *nskb;
244         netdev_features_t features;
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          *    insufficient MTU.
264          */
265         features = netif_skb_features(skb);
266         BUILD_BUG_ON(sizeof(*IPCB(skb)) > SKB_GSO_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         skb_list_walk_safe(segs, segs, nskb) {
276                 int err;
277 
278                 skb_mark_not_on_list(segs);
279                 err = ip_fragment(net, sk, segs, mtu, ip_finish_output2);
280 
281                 if (err && ret == 0)
282                         ret = err;
283         }
284 
285         return ret;
286 }
287 
288 static int __ip_finish_output(struct net *net, struct sock *sk, struct sk_buff *skb)
289 {
290         unsigned int mtu;
291 
292 #if defined(CONFIG_NETFILTER) && defined(CONFIG_XFRM)
293         /* Policy lookup after SNAT yielded a new policy */
294         if (skb_dst(skb)->xfrm) {
295                 IPCB(skb)->flags |= IPSKB_REROUTED;
296                 return dst_output(net, sk, skb);
297         }
298 #endif
299         mtu = ip_skb_dst_mtu(sk, skb);
300         if (skb_is_gso(skb))
301                 return ip_finish_output_gso(net, sk, skb, mtu);
302 
303         if (skb->len > mtu || IPCB(skb)->frag_max_size)
304                 return ip_fragment(net, sk, skb, mtu, ip_finish_output2);
305 
306         return ip_finish_output2(net, sk, skb);
307 }
308 
309 static int ip_finish_output(struct net *net, struct sock *sk, struct sk_buff *skb)
310 {
311         int ret;
312 
313         ret = BPF_CGROUP_RUN_PROG_INET_EGRESS(sk, skb);
314         switch (ret) {
315         case NET_XMIT_SUCCESS:
316                 return __ip_finish_output(net, sk, skb);
317         case NET_XMIT_CN:
318                 return __ip_finish_output(net, sk, skb) ? : ret;
319         default:
320                 kfree_skb(skb);
321                 return ret;
322         }
323 }
324 
325 static int ip_mc_finish_output(struct net *net, struct sock *sk,
326                                struct sk_buff *skb)
327 {
328         struct rtable *new_rt;
329         bool do_cn = false;
330         int ret, err;
331 
332         ret = BPF_CGROUP_RUN_PROG_INET_EGRESS(sk, skb);
333         switch (ret) {
334         case NET_XMIT_CN:
335                 do_cn = true;
336                 fallthrough;
337         case NET_XMIT_SUCCESS:
338                 break;
339         default:
340                 kfree_skb(skb);
341                 return ret;
342         }
343 
344         /* Reset rt_iif so that inet_iif() will return skb->skb_iif. Setting
345          * this to non-zero causes ipi_ifindex in in_pktinfo to be overwritten,
346          * see ipv4_pktinfo_prepare().
347          */
348         new_rt = rt_dst_clone(net->loopback_dev, skb_rtable(skb));
349         if (new_rt) {
350                 new_rt->rt_iif = 0;
351                 skb_dst_drop(skb);
352                 skb_dst_set(skb, &new_rt->dst);
353         }
354 
355         err = dev_loopback_xmit(net, sk, skb);
356         return (do_cn && err) ? ret : err;
357 }
358 
359 int ip_mc_output(struct net *net, struct sock *sk, struct sk_buff *skb)
360 {
361         struct rtable *rt = skb_rtable(skb);
362         struct net_device *dev = rt->dst.dev;
363 
364         /*
365          *      If the indicated interface is up and running, send the packet.
366          */
367         IP_UPD_PO_STATS(net, IPSTATS_MIB_OUT, skb->len);
368 
369         skb->dev = dev;
370         skb->protocol = htons(ETH_P_IP);
371 
372         /*
373          *      Multicasts are looped back for other local users
374          */
375 
376         if (rt->rt_flags&RTCF_MULTICAST) {
377                 if (sk_mc_loop(sk)
378 #ifdef CONFIG_IP_MROUTE
379                 /* Small optimization: do not loopback not local frames,
380                    which returned after forwarding; they will be  dropped
381                    by ip_mr_input in any case.
382                    Note, that local frames are looped back to be delivered
383                    to local recipients.
384 
385                    This check is duplicated in ip_mr_input at the moment.
386                  */
387                     &&
388                     ((rt->rt_flags & RTCF_LOCAL) ||
389                      !(IPCB(skb)->flags & IPSKB_FORWARDED))
390 #endif
391                    ) {
392                         struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
393                         if (newskb)
394                                 NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING,
395                                         net, sk, newskb, NULL, newskb->dev,
396                                         ip_mc_finish_output);
397                 }
398 
399                 /* Multicasts with ttl 0 must not go beyond the host */
400 
401                 if (ip_hdr(skb)->ttl == 0) {
402                         kfree_skb(skb);
403                         return 0;
404                 }
405         }
406 
407         if (rt->rt_flags&RTCF_BROADCAST) {
408                 struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
409                 if (newskb)
410                         NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING,
411                                 net, sk, newskb, NULL, newskb->dev,
412                                 ip_mc_finish_output);
413         }
414 
415         return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
416                             net, sk, skb, NULL, skb->dev,
417                             ip_finish_output,
418                             !(IPCB(skb)->flags & IPSKB_REROUTED));
419 }
420 
421 int ip_output(struct net *net, struct sock *sk, struct sk_buff *skb)
422 {
423         struct net_device *dev = skb_dst(skb)->dev, *indev = skb->dev;
424 
425         IP_UPD_PO_STATS(net, IPSTATS_MIB_OUT, skb->len);
426 
427         skb->dev = dev;
428         skb->protocol = htons(ETH_P_IP);
429 
430         return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
431                             net, sk, skb, indev, dev,
432                             ip_finish_output,
433                             !(IPCB(skb)->flags & IPSKB_REROUTED));
434 }
435 EXPORT_SYMBOL(ip_output);
436 
437 /*
438  * copy saddr and daddr, possibly using 64bit load/stores
439  * Equivalent to :
440  *   iph->saddr = fl4->saddr;
441  *   iph->daddr = fl4->daddr;
442  */
443 static void ip_copy_addrs(struct iphdr *iph, const struct flowi4 *fl4)
444 {
445         BUILD_BUG_ON(offsetof(typeof(*fl4), daddr) !=
446                      offsetof(typeof(*fl4), saddr) + sizeof(fl4->saddr));
447 
448         iph->saddr = fl4->saddr;
449         iph->daddr = 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 int ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl)
545 {
546         return __ip_queue_xmit(sk, skb, fl, inet_sk(sk)->tos);
547 }
548 EXPORT_SYMBOL(ip_queue_xmit);
549 
550 static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
551 {
552         to->pkt_type = from->pkt_type;
553         to->priority = from->priority;
554         to->protocol = from->protocol;
555         to->skb_iif = from->skb_iif;
556         skb_dst_drop(to);
557         skb_dst_copy(to, from);
558         to->dev = from->dev;
559         to->mark = from->mark;
560 
561         skb_copy_hash(to, from);
562 
563 #ifdef CONFIG_NET_SCHED
564         to->tc_index = from->tc_index;
565 #endif
566         nf_copy(to, from);
567         skb_ext_copy(to, from);
568 #if IS_ENABLED(CONFIG_IP_VS)
569         to->ipvs_property = from->ipvs_property;
570 #endif
571         skb_copy_secmark(to, from);
572 }
573 
574 static int ip_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
575                        unsigned int mtu,
576                        int (*output)(struct net *, struct sock *, struct sk_buff *))
577 {
578         struct iphdr *iph = ip_hdr(skb);
579 
580         if ((iph->frag_off & htons(IP_DF)) == 0)
581                 return ip_do_fragment(net, sk, skb, output);
582 
583         if (unlikely(!skb->ignore_df ||
584                      (IPCB(skb)->frag_max_size &&
585                       IPCB(skb)->frag_max_size > mtu))) {
586                 IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
587                 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
588                           htonl(mtu));
589                 kfree_skb(skb);
590                 return -EMSGSIZE;
591         }
592 
593         return ip_do_fragment(net, sk, skb, output);
594 }
595 
596 void ip_fraglist_init(struct sk_buff *skb, struct iphdr *iph,
597                       unsigned int hlen, struct ip_fraglist_iter *iter)
598 {
599         unsigned int first_len = skb_pagelen(skb);
600 
601         iter->frag = skb_shinfo(skb)->frag_list;
602         skb_frag_list_init(skb);
603 
604         iter->offset = 0;
605         iter->iph = iph;
606         iter->hlen = hlen;
607 
608         skb->data_len = first_len - skb_headlen(skb);
609         skb->len = first_len;
610         iph->tot_len = htons(first_len);
611         iph->frag_off = htons(IP_MF);
612         ip_send_check(iph);
613 }
614 EXPORT_SYMBOL(ip_fraglist_init);
615 
616 void ip_fraglist_prepare(struct sk_buff *skb, struct ip_fraglist_iter *iter)
617 {
618         unsigned int hlen = iter->hlen;
619         struct iphdr *iph = iter->iph;
620         struct sk_buff *frag;
621 
622         frag = iter->frag;
623         frag->ip_summed = CHECKSUM_NONE;
624         skb_reset_transport_header(frag);
625         __skb_push(frag, hlen);
626         skb_reset_network_header(frag);
627         memcpy(skb_network_header(frag), iph, hlen);
628         iter->iph = ip_hdr(frag);
629         iph = iter->iph;
630         iph->tot_len = htons(frag->len);
631         ip_copy_metadata(frag, skb);
632         iter->offset += skb->len - hlen;
633         iph->frag_off = htons(iter->offset >> 3);
634         if (frag->next)
635                 iph->frag_off |= htons(IP_MF);
636         /* Ready, complete checksum */
637         ip_send_check(iph);
638 }
639 EXPORT_SYMBOL(ip_fraglist_prepare);
640 
641 void ip_frag_init(struct sk_buff *skb, unsigned int hlen,
642                   unsigned int ll_rs, unsigned int mtu, bool DF,
643                   struct ip_frag_state *state)
644 {
645         struct iphdr *iph = ip_hdr(skb);
646 
647         state->DF = DF;
648         state->hlen = hlen;
649         state->ll_rs = ll_rs;
650         state->mtu = mtu;
651 
652         state->left = skb->len - hlen;  /* Space per frame */
653         state->ptr = hlen;              /* Where to start from */
654 
655         state->offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3;
656         state->not_last_frag = iph->frag_off & htons(IP_MF);
657 }
658 EXPORT_SYMBOL(ip_frag_init);
659 
660 static void ip_frag_ipcb(struct sk_buff *from, struct sk_buff *to,
661                          bool first_frag)
662 {
663         /* Copy the flags to each fragment. */
664         IPCB(to)->flags = IPCB(from)->flags;
665 
666         /* ANK: dirty, but effective trick. Upgrade options only if
667          * the segment to be fragmented was THE FIRST (otherwise,
668          * options are already fixed) and make it ONCE
669          * on the initial skb, so that all the following fragments
670          * will inherit fixed options.
671          */
672         if (first_frag)
673                 ip_options_fragment(from);
674 }
675 
676 struct sk_buff *ip_frag_next(struct sk_buff *skb, struct ip_frag_state *state)
677 {
678         unsigned int len = state->left;
679         struct sk_buff *skb2;
680         struct iphdr *iph;
681 
682         len = state->left;
683         /* IF: it doesn't fit, use 'mtu' - the data space left */
684         if (len > state->mtu)
685                 len = state->mtu;
686         /* IF: we are not sending up to and including the packet end
687            then align the next start on an eight byte boundary */
688         if (len < state->left)  {
689                 len &= ~7;
690         }
691 
692         /* Allocate buffer */
693         skb2 = alloc_skb(len + state->hlen + state->ll_rs, GFP_ATOMIC);
694         if (!skb2)
695                 return ERR_PTR(-ENOMEM);
696 
697         /*
698          *      Set up data on packet
699          */
700 
701         ip_copy_metadata(skb2, skb);
702         skb_reserve(skb2, state->ll_rs);
703         skb_put(skb2, len + state->hlen);
704         skb_reset_network_header(skb2);
705         skb2->transport_header = skb2->network_header + state->hlen;
706 
707         /*
708          *      Charge the memory for the fragment to any owner
709          *      it might possess
710          */
711 
712         if (skb->sk)
713                 skb_set_owner_w(skb2, skb->sk);
714 
715         /*
716          *      Copy the packet header into the new buffer.
717          */
718 
719         skb_copy_from_linear_data(skb, skb_network_header(skb2), state->hlen);
720 
721         /*
722          *      Copy a block of the IP datagram.
723          */
724         if (skb_copy_bits(skb, state->ptr, skb_transport_header(skb2), len))
725                 BUG();
726         state->left -= len;
727 
728         /*
729          *      Fill in the new header fields.
730          */
731         iph = ip_hdr(skb2);
732         iph->frag_off = htons((state->offset >> 3));
733         if (state->DF)
734                 iph->frag_off |= htons(IP_DF);
735 
736         /*
737          *      Added AC : If we are fragmenting a fragment that's not the
738          *                 last fragment then keep MF on each bit
739          */
740         if (state->left > 0 || state->not_last_frag)
741                 iph->frag_off |= htons(IP_MF);
742         state->ptr += len;
743         state->offset += len;
744 
745         iph->tot_len = htons(len + state->hlen);
746 
747         ip_send_check(iph);
748 
749         return skb2;
750 }
751 EXPORT_SYMBOL(ip_frag_next);
752 
753 /*
754  *      This IP datagram is too large to be sent in one piece.  Break it up into
755  *      smaller pieces (each of size equal to IP header plus
756  *      a block of the data of the original IP data part) that will yet fit in a
757  *      single device frame, and queue such a frame for sending.
758  */
759 
760 int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
761                    int (*output)(struct net *, struct sock *, struct sk_buff *))
762 {
763         struct iphdr *iph;
764         struct sk_buff *skb2;
765         struct rtable *rt = skb_rtable(skb);
766         unsigned int mtu, hlen, ll_rs;
767         struct ip_fraglist_iter iter;
768         ktime_t tstamp = skb->tstamp;
769         struct ip_frag_state state;
770         int err = 0;
771 
772         /* for offloaded checksums cleanup checksum before fragmentation */
773         if (skb->ip_summed == CHECKSUM_PARTIAL &&
774             (err = skb_checksum_help(skb)))
775                 goto fail;
776 
777         /*
778          *      Point into the IP datagram header.
779          */
780 
781         iph = ip_hdr(skb);
782 
783         mtu = ip_skb_dst_mtu(sk, skb);
784         if (IPCB(skb)->frag_max_size && IPCB(skb)->frag_max_size < mtu)
785                 mtu = IPCB(skb)->frag_max_size;
786 
787         /*
788          *      Setup starting values.
789          */
790 
791         hlen = iph->ihl * 4;
792         mtu = mtu - hlen;       /* Size of data space */
793         IPCB(skb)->flags |= IPSKB_FRAG_COMPLETE;
794         ll_rs = LL_RESERVED_SPACE(rt->dst.dev);
795 
796         /* When frag_list is given, use it. First, check its validity:
797          * some transformers could create wrong frag_list or break existing
798          * one, it is not prohibited. In this case fall back to copying.
799          *
800          * LATER: this step can be merged to real generation of fragments,
801          * we can switch to copy when see the first bad fragment.
802          */
803         if (skb_has_frag_list(skb)) {
804                 struct sk_buff *frag, *frag2;
805                 unsigned int first_len = skb_pagelen(skb);
806 
807                 if (first_len - hlen > mtu ||
808                     ((first_len - hlen) & 7) ||
809                     ip_is_fragment(iph) ||
810                     skb_cloned(skb) ||
811                     skb_headroom(skb) < ll_rs)
812                         goto slow_path;
813 
814                 skb_walk_frags(skb, frag) {
815                         /* Correct geometry. */
816                         if (frag->len > mtu ||
817                             ((frag->len & 7) && frag->next) ||
818                             skb_headroom(frag) < hlen + ll_rs)
819                                 goto slow_path_clean;
820 
821                         /* Partially cloned skb? */
822                         if (skb_shared(frag))
823                                 goto slow_path_clean;
824 
825                         BUG_ON(frag->sk);
826                         if (skb->sk) {
827                                 frag->sk = skb->sk;
828                                 frag->destructor = sock_wfree;
829                         }
830                         skb->truesize -= frag->truesize;
831                 }
832 
833                 /* Everything is OK. Generate! */
834                 ip_fraglist_init(skb, iph, hlen, &iter);
835 
836                 for (;;) {
837                         /* Prepare header of the next frame,
838                          * before previous one went down. */
839                         if (iter.frag) {
840                                 bool first_frag = (iter.offset == 0);
841 
842                                 IPCB(iter.frag)->flags = IPCB(skb)->flags;
843                                 ip_fraglist_prepare(skb, &iter);
844                                 if (first_frag && IPCB(skb)->opt.optlen) {
845                                         /* ipcb->opt is not populated for frags
846                                          * coming from __ip_make_skb(),
847                                          * ip_options_fragment() needs optlen
848                                          */
849                                         IPCB(iter.frag)->opt.optlen =
850                                                 IPCB(skb)->opt.optlen;
851                                         ip_options_fragment(iter.frag);
852                                         ip_send_check(iter.iph);
853                                 }
854                         }
855 
856                         skb->tstamp = tstamp;
857                         err = output(net, sk, skb);
858 
859                         if (!err)
860                                 IP_INC_STATS(net, IPSTATS_MIB_FRAGCREATES);
861                         if (err || !iter.frag)
862                                 break;
863 
864                         skb = ip_fraglist_next(&iter);
865                 }
866 
867                 if (err == 0) {
868                         IP_INC_STATS(net, IPSTATS_MIB_FRAGOKS);
869                         return 0;
870                 }
871 
872                 kfree_skb_list(iter.frag);
873 
874                 IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
875                 return err;
876 
877 slow_path_clean:
878                 skb_walk_frags(skb, frag2) {
879                         if (frag2 == frag)
880                                 break;
881                         frag2->sk = NULL;
882                         frag2->destructor = NULL;
883                         skb->truesize += frag2->truesize;
884                 }
885         }
886 
887 slow_path:
888         /*
889          *      Fragment the datagram.
890          */
891 
892         ip_frag_init(skb, hlen, ll_rs, mtu, IPCB(skb)->flags & IPSKB_FRAG_PMTU,
893                      &state);
894 
895         /*
896          *      Keep copying data until we run out.
897          */
898 
899         while (state.left > 0) {
900                 bool first_frag = (state.offset == 0);
901 
902                 skb2 = ip_frag_next(skb, &state);
903                 if (IS_ERR(skb2)) {
904                         err = PTR_ERR(skb2);
905                         goto fail;
906                 }
907                 ip_frag_ipcb(skb, skb2, first_frag);
908 
909                 /*
910                  *      Put this fragment into the sending queue.
911                  */
912                 skb2->tstamp = tstamp;
913                 err = output(net, sk, skb2);
914                 if (err)
915                         goto fail;
916 
917                 IP_INC_STATS(net, IPSTATS_MIB_FRAGCREATES);
918         }
919         consume_skb(skb);
920         IP_INC_STATS(net, IPSTATS_MIB_FRAGOKS);
921         return err;
922 
923 fail:
924         kfree_skb(skb);
925         IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
926         return err;
927 }
928 EXPORT_SYMBOL(ip_do_fragment);
929 
930 int
931 ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
932 {
933         struct msghdr *msg = from;
934 
935         if (skb->ip_summed == CHECKSUM_PARTIAL) {
936                 if (!copy_from_iter_full(to, len, &msg->msg_iter))
937                         return -EFAULT;
938         } else {
939                 __wsum csum = 0;
940                 if (!csum_and_copy_from_iter_full(to, len, &csum, &msg->msg_iter))
941                         return -EFAULT;
942                 skb->csum = csum_block_add(skb->csum, csum, odd);
943         }
944         return 0;
945 }
946 EXPORT_SYMBOL(ip_generic_getfrag);
947 
948 static inline __wsum
949 csum_page(struct page *page, int offset, int copy)
950 {
951         char *kaddr;
952         __wsum csum;
953         kaddr = kmap(page);
954         csum = csum_partial(kaddr + offset, copy, 0);
955         kunmap(page);
956         return csum;
957 }
958 
959 static int __ip_append_data(struct sock *sk,
960                             struct flowi4 *fl4,
961                             struct sk_buff_head *queue,
962                             struct inet_cork *cork,
963                             struct page_frag *pfrag,
964                             int getfrag(void *from, char *to, int offset,
965                                         int len, int odd, struct sk_buff *skb),
966                             void *from, int length, int transhdrlen,
967                             unsigned int flags)
968 {
969         struct inet_sock *inet = inet_sk(sk);
970         struct ubuf_info *uarg = NULL;
971         struct sk_buff *skb;
972 
973         struct ip_options *opt = cork->opt;
974         int hh_len;
975         int exthdrlen;
976         int mtu;
977         int copy;
978         int err;
979         int offset = 0;
980         unsigned int maxfraglen, fragheaderlen, maxnonfragsize;
981         int csummode = CHECKSUM_NONE;
982         struct rtable *rt = (struct rtable *)cork->dst;
983         unsigned int wmem_alloc_delta = 0;
984         bool paged, extra_uref = false;
985         u32 tskey = 0;
986 
987         skb = skb_peek_tail(queue);
988 
989         exthdrlen = !skb ? rt->dst.header_len : 0;
990         mtu = cork->gso_size ? IP_MAX_MTU : cork->fragsize;
991         paged = !!cork->gso_size;
992 
993         if (cork->tx_flags & SKBTX_ANY_SW_TSTAMP &&
994             sk->sk_tsflags & SOF_TIMESTAMPING_OPT_ID)
995                 tskey = atomic_inc_return(&sk->sk_tskey) - 1;
996 
997         hh_len = LL_RESERVED_SPACE(rt->dst.dev);
998 
999         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
1000         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
1001         maxnonfragsize = ip_sk_ignore_df(sk) ? IP_MAX_MTU : mtu;
1002 
1003         if (cork->length + length > maxnonfragsize - fragheaderlen) {
1004                 ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
1005                                mtu - (opt ? opt->optlen : 0));
1006                 return -EMSGSIZE;
1007         }
1008 
1009         /*
1010          * transhdrlen > 0 means that this is the first fragment and we wish
1011          * it won't be fragmented in the future.
1012          */
1013         if (transhdrlen &&
1014             length + fragheaderlen <= mtu &&
1015             rt->dst.dev->features & (NETIF_F_HW_CSUM | NETIF_F_IP_CSUM) &&
1016             (!(flags & MSG_MORE) || cork->gso_size) &&
1017             (!exthdrlen || (rt->dst.dev->features & NETIF_F_HW_ESP_TX_CSUM)))
1018                 csummode = CHECKSUM_PARTIAL;
1019 
1020         if (flags & MSG_ZEROCOPY && length && sock_flag(sk, SOCK_ZEROCOPY)) {
1021                 uarg = msg_zerocopy_realloc(sk, length, skb_zcopy(skb));
1022                 if (!uarg)
1023                         return -ENOBUFS;
1024                 extra_uref = !skb_zcopy(skb);   /* only ref on new uarg */
1025                 if (rt->dst.dev->features & NETIF_F_SG &&
1026                     csummode == CHECKSUM_PARTIAL) {
1027                         paged = true;
1028                 } else {
1029                         uarg->zerocopy = 0;
1030                         skb_zcopy_set(skb, uarg, &extra_uref);
1031                 }
1032         }
1033 
1034         cork->length += length;
1035 
1036         /* So, what's going on in the loop below?
1037          *
1038          * We use calculated fragment length to generate chained skb,
1039          * each of segments is IP fragment ready for sending to network after
1040          * adding appropriate IP header.
1041          */
1042 
1043         if (!skb)
1044                 goto alloc_new_skb;
1045 
1046         while (length > 0) {
1047                 /* Check if the remaining data fits into current packet. */
1048                 copy = mtu - skb->len;
1049                 if (copy < length)
1050                         copy = maxfraglen - skb->len;
1051                 if (copy <= 0) {
1052                         char *data;
1053                         unsigned int datalen;
1054                         unsigned int fraglen;
1055                         unsigned int fraggap;
1056                         unsigned int alloclen, alloc_extra;
1057                         unsigned int pagedlen;
1058                         struct sk_buff *skb_prev;
1059 alloc_new_skb:
1060                         skb_prev = skb;
1061                         if (skb_prev)
1062                                 fraggap = skb_prev->len - maxfraglen;
1063                         else
1064                                 fraggap = 0;
1065 
1066                         /*
1067                          * If remaining data exceeds the mtu,
1068                          * we know we need more fragment(s).
1069                          */
1070                         datalen = length + fraggap;
1071                         if (datalen > mtu - fragheaderlen)
1072                                 datalen = maxfraglen - fragheaderlen;
1073                         fraglen = datalen + fragheaderlen;
1074                         pagedlen = 0;
1075 
1076                         alloc_extra = hh_len + 15;
1077                         alloc_extra += exthdrlen;
1078 
1079                         /* The last fragment gets additional space at tail.
1080                          * Note, with MSG_MORE we overallocate on fragments,
1081                          * because we have no idea what fragment will be
1082                          * the last.
1083                          */
1084                         if (datalen == length + fraggap)
1085                                 alloc_extra += rt->dst.trailer_len;
1086 
1087                         if ((flags & MSG_MORE) &&
1088                             !(rt->dst.dev->features&NETIF_F_SG))
1089                                 alloclen = mtu;
1090                         else if (!paged &&
1091                                  (fraglen + alloc_extra < SKB_MAX_ALLOC ||
1092                                   !(rt->dst.dev->features & NETIF_F_SG)))
1093                                 alloclen = fraglen;
1094                         else {
1095                                 alloclen = min_t(int, fraglen, MAX_HEADER);
1096                                 pagedlen = fraglen - alloclen;
1097                         }
1098 
1099                         alloclen += alloc_extra;
1100 
1101                         if (transhdrlen) {
1102                                 skb = sock_alloc_send_skb(sk, alloclen,
1103                                                 (flags & MSG_DONTWAIT), &err);
1104                         } else {
1105                                 skb = NULL;
1106                                 if (refcount_read(&sk->sk_wmem_alloc) + wmem_alloc_delta <=
1107                                     2 * sk->sk_sndbuf)
1108                                         skb = alloc_skb(alloclen,
1109                                                         sk->sk_allocation);
1110                                 if (unlikely(!skb))
1111                                         err = -ENOBUFS;
1112                         }
1113                         if (!skb)
1114                                 goto error;
1115 
1116                         /*
1117                          *      Fill in the control structures
1118                          */
1119                         skb->ip_summed = csummode;
1120                         skb->csum = 0;
1121                         skb_reserve(skb, hh_len);
1122 
1123                         /*
1124                          *      Find where to start putting bytes.
1125                          */
1126                         data = skb_put(skb, fraglen + exthdrlen - pagedlen);
1127                         skb_set_network_header(skb, exthdrlen);
1128                         skb->transport_header = (skb->network_header +
1129                                                  fragheaderlen);
1130                         data += fragheaderlen + exthdrlen;
1131 
1132                         if (fraggap) {
1133                                 skb->csum = skb_copy_and_csum_bits(
1134                                         skb_prev, maxfraglen,
1135                                         data + transhdrlen, fraggap);
1136                                 skb_prev->csum = csum_sub(skb_prev->csum,
1137                                                           skb->csum);
1138                                 data += fraggap;
1139                                 pskb_trim_unique(skb_prev, maxfraglen);
1140                         }
1141 
1142                         copy = datalen - transhdrlen - fraggap - pagedlen;
1143                         if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
1144                                 err = -EFAULT;
1145                                 kfree_skb(skb);
1146                                 goto error;
1147                         }
1148 
1149                         offset += copy;
1150                         length -= copy + transhdrlen;
1151                         transhdrlen = 0;
1152                         exthdrlen = 0;
1153                         csummode = CHECKSUM_NONE;
1154 
1155                         /* only the initial fragment is time stamped */
1156                         skb_shinfo(skb)->tx_flags = cork->tx_flags;
1157                         cork->tx_flags = 0;
1158                         skb_shinfo(skb)->tskey = tskey;
1159                         tskey = 0;
1160                         skb_zcopy_set(skb, uarg, &extra_uref);
1161 
1162                         if ((flags & MSG_CONFIRM) && !skb_prev)
1163                                 skb_set_dst_pending_confirm(skb, 1);
1164 
1165                         /*
1166                          * Put the packet on the pending queue.
1167                          */
1168                         if (!skb->destructor) {
1169                                 skb->destructor = sock_wfree;
1170                                 skb->sk = sk;
1171                                 wmem_alloc_delta += skb->truesize;
1172                         }
1173                         __skb_queue_tail(queue, skb);
1174                         continue;
1175                 }
1176 
1177                 if (copy > length)
1178                         copy = length;
1179 
1180                 if (!(rt->dst.dev->features&NETIF_F_SG) &&
1181                     skb_tailroom(skb) >= copy) {
1182                         unsigned int off;
1183 
1184                         off = skb->len;
1185                         if (getfrag(from, skb_put(skb, copy),
1186                                         offset, copy, off, skb) < 0) {
1187                                 __skb_trim(skb, off);
1188                                 err = -EFAULT;
1189                                 goto error;
1190                         }
1191                 } else if (!uarg || !uarg->zerocopy) {
1192                         int i = skb_shinfo(skb)->nr_frags;
1193 
1194                         err = -ENOMEM;
1195                         if (!sk_page_frag_refill(sk, pfrag))
1196                                 goto error;
1197 
1198                         if (!skb_can_coalesce(skb, i, pfrag->page,
1199                                               pfrag->offset)) {
1200                                 err = -EMSGSIZE;
1201                                 if (i == MAX_SKB_FRAGS)
1202                                         goto error;
1203 
1204                                 __skb_fill_page_desc(skb, i, pfrag->page,
1205                                                      pfrag->offset, 0);
1206                                 skb_shinfo(skb)->nr_frags = ++i;
1207                                 get_page(pfrag->page);
1208                         }
1209                         copy = min_t(int, copy, pfrag->size - pfrag->offset);
1210                         if (getfrag(from,
1211                                     page_address(pfrag->page) + pfrag->offset,
1212                                     offset, copy, skb->len, skb) < 0)
1213                                 goto error_efault;
1214 
1215                         pfrag->offset += copy;
1216                         skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
1217                         skb->len += copy;
1218                         skb->data_len += copy;
1219                         skb->truesize += copy;
1220                         wmem_alloc_delta += copy;
1221                 } else {
1222                         err = skb_zerocopy_iter_dgram(skb, from, copy);
1223                         if (err < 0)
1224                                 goto error;
1225                 }
1226                 offset += copy;
1227                 length -= copy;
1228         }
1229 
1230         if (wmem_alloc_delta)
1231                 refcount_add(wmem_alloc_delta, &sk->sk_wmem_alloc);
1232         return 0;
1233 
1234 error_efault:
1235         err = -EFAULT;
1236 error:
1237         net_zcopy_put_abort(uarg, extra_uref);
1238         cork->length -= length;
1239         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1240         refcount_add(wmem_alloc_delta, &sk->sk_wmem_alloc);
1241         return err;
1242 }
1243 
1244 static int ip_setup_cork(struct sock *sk, struct inet_cork *cork,
1245                          struct ipcm_cookie *ipc, struct rtable **rtp)
1246 {
1247         struct ip_options_rcu *opt;
1248         struct rtable *rt;
1249 
1250         rt = *rtp;
1251         if (unlikely(!rt))
1252                 return -EFAULT;
1253 
1254         /*
1255          * setup for corking.
1256          */
1257         opt = ipc->opt;
1258         if (opt) {
1259                 if (!cork->opt) {
1260                         cork->opt = kmalloc(sizeof(struct ip_options) + 40,
1261                                             sk->sk_allocation);
1262                         if (unlikely(!cork->opt))
1263                                 return -ENOBUFS;
1264                 }
1265                 memcpy(cork->opt, &opt->opt, sizeof(struct ip_options) + opt->opt.optlen);
1266                 cork->flags |= IPCORK_OPT;
1267                 cork->addr = ipc->addr;
1268         }
1269 
1270         cork->fragsize = ip_sk_use_pmtu(sk) ?
1271                          dst_mtu(&rt->dst) : READ_ONCE(rt->dst.dev->mtu);
1272 
1273         if (!inetdev_valid_mtu(cork->fragsize))
1274                 return -ENETUNREACH;
1275 
1276         cork->gso_size = ipc->gso_size;
1277 
1278         cork->dst = &rt->dst;
1279         /* We stole this route, caller should not release it. */
1280         *rtp = NULL;
1281 
1282         cork->length = 0;
1283         cork->ttl = ipc->ttl;
1284         cork->tos = ipc->tos;
1285         cork->mark = ipc->sockc.mark;
1286         cork->priority = ipc->priority;
1287         cork->transmit_time = ipc->sockc.transmit_time;
1288         cork->tx_flags = 0;
1289         sock_tx_timestamp(sk, ipc->sockc.tsflags, &cork->tx_flags);
1290 
1291         return 0;
1292 }
1293 
1294 /*
1295  *      ip_append_data() and ip_append_page() can make one large IP datagram
1296  *      from many pieces of data. Each pieces will be holded on the socket
1297  *      until ip_push_pending_frames() is called. Each piece can be a page
1298  *      or non-page data.
1299  *
1300  *      Not only UDP, other transport protocols - e.g. raw sockets - can use
1301  *      this interface potentially.
1302  *
1303  *      LATER: length must be adjusted by pad at tail, when it is required.
1304  */
1305 int ip_append_data(struct sock *sk, struct flowi4 *fl4,
1306                    int getfrag(void *from, char *to, int offset, int len,
1307                                int odd, struct sk_buff *skb),
1308                    void *from, int length, int transhdrlen,
1309                    struct ipcm_cookie *ipc, struct rtable **rtp,
1310                    unsigned int flags)
1311 {
1312         struct inet_sock *inet = inet_sk(sk);
1313         int err;
1314 
1315         if (flags&MSG_PROBE)
1316                 return 0;
1317 
1318         if (skb_queue_empty(&sk->sk_write_queue)) {
1319                 err = ip_setup_cork(sk, &inet->cork.base, ipc, rtp);
1320                 if (err)
1321                         return err;
1322         } else {
1323                 transhdrlen = 0;
1324         }
1325 
1326         return __ip_append_data(sk, fl4, &sk->sk_write_queue, &inet->cork.base,
1327                                 sk_page_frag(sk), getfrag,
1328                                 from, length, transhdrlen, flags);
1329 }
1330 
1331 ssize_t ip_append_page(struct sock *sk, struct flowi4 *fl4, struct page *page,
1332                        int offset, size_t size, int flags)
1333 {
1334         struct inet_sock *inet = inet_sk(sk);
1335         struct sk_buff *skb;
1336         struct rtable *rt;
1337         struct ip_options *opt = NULL;
1338         struct inet_cork *cork;
1339         int hh_len;
1340         int mtu;
1341         int len;
1342         int err;
1343         unsigned int maxfraglen, fragheaderlen, fraggap, maxnonfragsize;
1344 
1345         if (inet->hdrincl)
1346                 return -EPERM;
1347 
1348         if (flags&MSG_PROBE)
1349                 return 0;
1350 
1351         if (skb_queue_empty(&sk->sk_write_queue))
1352                 return -EINVAL;
1353 
1354         cork = &inet->cork.base;
1355         rt = (struct rtable *)cork->dst;
1356         if (cork->flags & IPCORK_OPT)
1357                 opt = cork->opt;
1358 
1359         if (!(rt->dst.dev->features & NETIF_F_SG))
1360                 return -EOPNOTSUPP;
1361 
1362         hh_len = LL_RESERVED_SPACE(rt->dst.dev);
1363         mtu = cork->gso_size ? IP_MAX_MTU : cork->fragsize;
1364 
1365         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
1366         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
1367         maxnonfragsize = ip_sk_ignore_df(sk) ? 0xFFFF : mtu;
1368 
1369         if (cork->length + size > maxnonfragsize - fragheaderlen) {
1370                 ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
1371                                mtu - (opt ? opt->optlen : 0));
1372                 return -EMSGSIZE;
1373         }
1374 
1375         skb = skb_peek_tail(&sk->sk_write_queue);
1376         if (!skb)
1377                 return -EINVAL;
1378 
1379         cork->length += size;
1380 
1381         while (size > 0) {
1382                 /* Check if the remaining data fits into current packet. */
1383                 len = mtu - skb->len;
1384                 if (len < size)
1385                         len = maxfraglen - skb->len;
1386 
1387                 if (len <= 0) {
1388                         struct sk_buff *skb_prev;
1389                         int alloclen;
1390 
1391                         skb_prev = skb;
1392                         fraggap = skb_prev->len - maxfraglen;
1393 
1394                         alloclen = fragheaderlen + hh_len + fraggap + 15;
1395                         skb = sock_wmalloc(sk, alloclen, 1, sk->sk_allocation);
1396                         if (unlikely(!skb)) {
1397                                 err = -ENOBUFS;
1398                                 goto error;
1399                         }
1400 
1401                         /*
1402                          *      Fill in the control structures
1403                          */
1404                         skb->ip_summed = CHECKSUM_NONE;
1405                         skb->csum = 0;
1406                         skb_reserve(skb, hh_len);
1407 
1408                         /*
1409                          *      Find where to start putting bytes.
1410                          */
1411                         skb_put(skb, fragheaderlen + fraggap);
1412                         skb_reset_network_header(skb);
1413                         skb->transport_header = (skb->network_header +
1414                                                  fragheaderlen);
1415                         if (fraggap) {
1416                                 skb->csum = skb_copy_and_csum_bits(skb_prev,
1417                                                                    maxfraglen,
1418                                                     skb_transport_header(skb),
1419                                                                    fraggap);
1420                                 skb_prev->csum = csum_sub(skb_prev->csum,
1421                                                           skb->csum);
1422                                 pskb_trim_unique(skb_prev, maxfraglen);
1423                         }
1424 
1425                         /*
1426                          * Put the packet on the pending queue.
1427                          */
1428                         __skb_queue_tail(&sk->sk_write_queue, skb);
1429                         continue;
1430                 }
1431 
1432                 if (len > size)
1433                         len = size;
1434 
1435                 if (skb_append_pagefrags(skb, page, offset, len)) {
1436                         err = -EMSGSIZE;
1437                         goto error;
1438                 }
1439 
1440                 if (skb->ip_summed == CHECKSUM_NONE) {
1441                         __wsum csum;
1442                         csum = csum_page(page, offset, len);
1443                         skb->csum = csum_block_add(skb->csum, csum, skb->len);
1444                 }
1445 
1446                 skb->len += len;
1447                 skb->data_len += len;
1448                 skb->truesize += len;
1449                 refcount_add(len, &sk->sk_wmem_alloc);
1450                 offset += len;
1451                 size -= len;
1452         }
1453         return 0;
1454 
1455 error:
1456         cork->length -= size;
1457         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1458         return err;
1459 }
1460 
1461 static void ip_cork_release(struct inet_cork *cork)
1462 {
1463         cork->flags &= ~IPCORK_OPT;
1464         kfree(cork->opt);
1465         cork->opt = NULL;
1466         dst_release(cork->dst);
1467         cork->dst = NULL;
1468 }
1469 
1470 /*
1471  *      Combined all pending IP fragments on the socket as one IP datagram
1472  *      and push them out.
1473  */
1474 struct sk_buff *__ip_make_skb(struct sock *sk,
1475                               struct flowi4 *fl4,
1476                               struct sk_buff_head *queue,
1477                               struct inet_cork *cork)
1478 {
1479         struct sk_buff *skb, *tmp_skb;
1480         struct sk_buff **tail_skb;
1481         struct inet_sock *inet = inet_sk(sk);
1482         struct net *net = sock_net(sk);
1483         struct ip_options *opt = NULL;
1484         struct rtable *rt = (struct rtable *)cork->dst;
1485         struct iphdr *iph;
1486         __be16 df = 0;
1487         __u8 ttl;
1488 
1489         skb = __skb_dequeue(queue);
1490         if (!skb)
1491                 goto out;
1492         tail_skb = &(skb_shinfo(skb)->frag_list);
1493 
1494         /* move skb->data to ip header from ext header */
1495         if (skb->data < skb_network_header(skb))
1496                 __skb_pull(skb, skb_network_offset(skb));
1497         while ((tmp_skb = __skb_dequeue(queue)) != NULL) {
1498                 __skb_pull(tmp_skb, skb_network_header_len(skb));
1499                 *tail_skb = tmp_skb;
1500                 tail_skb = &(tmp_skb->next);
1501                 skb->len += tmp_skb->len;
1502                 skb->data_len += tmp_skb->len;
1503                 skb->truesize += tmp_skb->truesize;
1504                 tmp_skb->destructor = NULL;
1505                 tmp_skb->sk = NULL;
1506         }
1507 
1508         /* Unless user demanded real pmtu discovery (IP_PMTUDISC_DO), we allow
1509          * to fragment the frame generated here. No matter, what transforms
1510          * how transforms change size of the packet, it will come out.
1511          */
1512         skb->ignore_df = ip_sk_ignore_df(sk);
1513 
1514         /* DF bit is set when we want to see DF on outgoing frames.
1515          * If ignore_df is set too, we still allow to fragment this frame
1516          * locally. */
1517         if (inet->pmtudisc == IP_PMTUDISC_DO ||
1518             inet->pmtudisc == IP_PMTUDISC_PROBE ||
1519             (skb->len <= dst_mtu(&rt->dst) &&
1520              ip_dont_fragment(sk, &rt->dst)))
1521                 df = htons(IP_DF);
1522 
1523         if (cork->flags & IPCORK_OPT)
1524                 opt = cork->opt;
1525 
1526         if (cork->ttl != 0)
1527                 ttl = cork->ttl;
1528         else if (rt->rt_type == RTN_MULTICAST)
1529                 ttl = inet->mc_ttl;
1530         else
1531                 ttl = ip_select_ttl(inet, &rt->dst);
1532 
1533         iph = ip_hdr(skb);
1534         iph->version = 4;
1535         iph->ihl = 5;
1536         iph->tos = (cork->tos != -1) ? cork->tos : inet->tos;
1537         iph->frag_off = df;
1538         iph->ttl = ttl;
1539         iph->protocol = sk->sk_protocol;
1540         ip_copy_addrs(iph, fl4);
1541         ip_select_ident(net, skb, sk);
1542 
1543         if (opt) {
1544                 iph->ihl += opt->optlen >> 2;
1545                 ip_options_build(skb, opt, cork->addr, rt, 0);
1546         }
1547 
1548         skb->priority = (cork->tos != -1) ? cork->priority: sk->sk_priority;
1549         skb->mark = cork->mark;
1550         skb->tstamp = cork->transmit_time;
1551         /*
1552          * Steal rt from cork.dst to avoid a pair of atomic_inc/atomic_dec
1553          * on dst refcount
1554          */
1555         cork->dst = NULL;
1556         skb_dst_set(skb, &rt->dst);
1557 
1558         if (iph->protocol == IPPROTO_ICMP)
1559                 icmp_out_count(net, ((struct icmphdr *)
1560                         skb_transport_header(skb))->type);
1561 
1562         ip_cork_release(cork);
1563 out:
1564         return skb;
1565 }
1566 
1567 int ip_send_skb(struct net *net, struct sk_buff *skb)
1568 {
1569         int err;
1570 
1571         err = ip_local_out(net, skb->sk, skb);
1572         if (err) {
1573                 if (err > 0)
1574                         err = net_xmit_errno(err);
1575                 if (err)
1576                         IP_INC_STATS(net, IPSTATS_MIB_OUTDISCARDS);
1577         }
1578 
1579         return err;
1580 }
1581 
1582 int ip_push_pending_frames(struct sock *sk, struct flowi4 *fl4)
1583 {
1584         struct sk_buff *skb;
1585 
1586         skb = ip_finish_skb(sk, fl4);
1587         if (!skb)
1588                 return 0;
1589 
1590         /* Netfilter gets whole the not fragmented skb. */
1591         return ip_send_skb(sock_net(sk), skb);
1592 }
1593 
1594 /*
1595  *      Throw away all pending data on the socket.
1596  */
1597 static void __ip_flush_pending_frames(struct sock *sk,
1598                                       struct sk_buff_head *queue,
1599                                       struct inet_cork *cork)
1600 {
1601         struct sk_buff *skb;
1602 
1603         while ((skb = __skb_dequeue_tail(queue)) != NULL)
1604                 kfree_skb(skb);
1605 
1606         ip_cork_release(cork);
1607 }
1608 
1609 void ip_flush_pending_frames(struct sock *sk)
1610 {
1611         __ip_flush_pending_frames(sk, &sk->sk_write_queue, &inet_sk(sk)->cork.base);
1612 }
1613 
1614 struct sk_buff *ip_make_skb(struct sock *sk,
1615                             struct flowi4 *fl4,
1616                             int getfrag(void *from, char *to, int offset,
1617                                         int len, int odd, struct sk_buff *skb),
1618                             void *from, int length, int transhdrlen,
1619                             struct ipcm_cookie *ipc, struct rtable **rtp,
1620                             struct inet_cork *cork, unsigned int flags)
1621 {
1622         struct sk_buff_head queue;
1623         int err;
1624 
1625         if (flags & MSG_PROBE)
1626                 return NULL;
1627 
1628         __skb_queue_head_init(&queue);
1629 
1630         cork->flags = 0;
1631         cork->addr = 0;
1632         cork->opt = NULL;
1633         err = ip_setup_cork(sk, cork, ipc, rtp);
1634         if (err)
1635                 return ERR_PTR(err);
1636 
1637         err = __ip_append_data(sk, fl4, &queue, cork,
1638                                &current->task_frag, getfrag,
1639                                from, length, transhdrlen, flags);
1640         if (err) {
1641                 __ip_flush_pending_frames(sk, &queue, cork);
1642                 return ERR_PTR(err);
1643         }
1644 
1645         return __ip_make_skb(sk, fl4, &queue, cork);
1646 }
1647 
1648 /*
1649  *      Fetch data from kernel space and fill in checksum if needed.
1650  */
1651 static int ip_reply_glue_bits(void *dptr, char *to, int offset,
1652                               int len, int odd, struct sk_buff *skb)
1653 {
1654         __wsum csum;
1655 
1656         csum = csum_partial_copy_nocheck(dptr+offset, to, len);
1657         skb->csum = csum_block_add(skb->csum, csum, odd);
1658         return 0;
1659 }
1660 
1661 /*
1662  *      Generic function to send a packet as reply to another packet.
1663  *      Used to send some TCP resets/acks so far.
1664  */
1665 void ip_send_unicast_reply(struct sock *sk, struct sk_buff *skb,
1666                            const struct ip_options *sopt,
1667                            __be32 daddr, __be32 saddr,
1668                            const struct ip_reply_arg *arg,
1669                            unsigned int len, u64 transmit_time)
1670 {
1671         struct ip_options_data replyopts;
1672         struct ipcm_cookie ipc;
1673         struct flowi4 fl4;
1674         struct rtable *rt = skb_rtable(skb);
1675         struct net *net = sock_net(sk);
1676         struct sk_buff *nskb;
1677         int err;
1678         int oif;
1679 
1680         if (__ip_options_echo(net, &replyopts.opt.opt, skb, sopt))
1681                 return;
1682 
1683         ipcm_init(&ipc);
1684         ipc.addr = daddr;
1685         ipc.sockc.transmit_time = transmit_time;
1686 
1687         if (replyopts.opt.opt.optlen) {
1688                 ipc.opt = &replyopts.opt;
1689 
1690                 if (replyopts.opt.opt.srr)
1691                         daddr = replyopts.opt.opt.faddr;
1692         }
1693 
1694         oif = arg->bound_dev_if;
1695         if (!oif && netif_index_is_l3_master(net, skb->skb_iif))
1696                 oif = skb->skb_iif;
1697 
1698         flowi4_init_output(&fl4, oif,
1699                            IP4_REPLY_MARK(net, skb->mark) ?: sk->sk_mark,
1700                            RT_TOS(arg->tos),
1701                            RT_SCOPE_UNIVERSE, ip_hdr(skb)->protocol,
1702                            ip_reply_arg_flowi_flags(arg),
1703                            daddr, saddr,
1704                            tcp_hdr(skb)->source, tcp_hdr(skb)->dest,
1705                            arg->uid);
1706         security_skb_classify_flow(skb, flowi4_to_flowi_common(&fl4));
1707         rt = ip_route_output_key(net, &fl4);
1708         if (IS_ERR(rt))
1709                 return;
1710 
1711         inet_sk(sk)->tos = arg->tos & ~INET_ECN_MASK;
1712 
1713         sk->sk_protocol = ip_hdr(skb)->protocol;
1714         sk->sk_bound_dev_if = arg->bound_dev_if;
1715         sk->sk_sndbuf = sysctl_wmem_default;
1716         ipc.sockc.mark = fl4.flowi4_mark;
1717         err = ip_append_data(sk, &fl4, ip_reply_glue_bits, arg->iov->iov_base,
1718                              len, 0, &ipc, &rt, MSG_DONTWAIT);
1719         if (unlikely(err)) {
1720                 ip_flush_pending_frames(sk);
1721                 goto out;
1722         }
1723 
1724         nskb = skb_peek(&sk->sk_write_queue);
1725         if (nskb) {
1726                 if (arg->csumoffset >= 0)
1727                         *((__sum16 *)skb_transport_header(nskb) +
1728                           arg->csumoffset) = csum_fold(csum_add(nskb->csum,
1729                                                                 arg->csum));
1730                 nskb->ip_summed = CHECKSUM_NONE;
1731                 ip_push_pending_frames(sk, &fl4);
1732         }
1733 out:
1734         ip_rt_put(rt);
1735 }
1736 
1737 void __init ip_init(void)
1738 {
1739         ip_rt_init();
1740         inet_initpeers();
1741 
1742 #if defined(CONFIG_IP_MULTICAST)
1743         igmp_mc_init();
1744 #endif
1745 }
1746 

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