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Linux/net/ipv4/ip_output.c

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  1 /*
  2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
  3  *              operating system.  INET is implemented using the  BSD Socket
  4  *              interface as the means of communication with the user level.
  5  *
  6  *              The Internet Protocol (IP) output module.
  7  *
  8  * Authors:     Ross Biro
  9  *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 10  *              Donald Becker, <becker@super.org>
 11  *              Alan Cox, <Alan.Cox@linux.org>
 12  *              Richard Underwood
 13  *              Stefan Becker, <stefanb@yello.ping.de>
 14  *              Jorge Cwik, <jorge@laser.satlink.net>
 15  *              Arnt Gulbrandsen, <agulbra@nvg.unit.no>
 16  *              Hirokazu Takahashi, <taka@valinux.co.jp>
 17  *
 18  *      See ip_input.c for original log
 19  *
 20  *      Fixes:
 21  *              Alan Cox        :       Missing nonblock feature in ip_build_xmit.
 22  *              Mike Kilburn    :       htons() missing in ip_build_xmit.
 23  *              Bradford Johnson:       Fix faulty handling of some frames when
 24  *                                      no route is found.
 25  *              Alexander Demenshin:    Missing sk/skb free in ip_queue_xmit
 26  *                                      (in case if packet not accepted by
 27  *                                      output firewall rules)
 28  *              Mike McLagan    :       Routing by source
 29  *              Alexey Kuznetsov:       use new route cache
 30  *              Andi Kleen:             Fix broken PMTU recovery and remove
 31  *                                      some redundant tests.
 32  *      Vitaly E. Lavrov        :       Transparent proxy revived after year coma.
 33  *              Andi Kleen      :       Replace ip_reply with ip_send_reply.
 34  *              Andi Kleen      :       Split fast and slow ip_build_xmit path
 35  *                                      for decreased register pressure on x86
 36  *                                      and more readibility.
 37  *              Marc Boucher    :       When call_out_firewall returns FW_QUEUE,
 38  *                                      silently drop skb instead of failing with -EPERM.
 39  *              Detlev Wengorz  :       Copy protocol for fragments.
 40  *              Hirokazu Takahashi:     HW checksumming for outgoing UDP
 41  *                                      datagrams.
 42  *              Hirokazu Takahashi:     sendfile() on UDP works now.
 43  */
 44 
 45 #include <linux/uaccess.h>
 46 #include <linux/module.h>
 47 #include <linux/types.h>
 48 #include <linux/kernel.h>
 49 #include <linux/mm.h>
 50 #include <linux/string.h>
 51 #include <linux/errno.h>
 52 #include <linux/highmem.h>
 53 #include <linux/slab.h>
 54 
 55 #include <linux/socket.h>
 56 #include <linux/sockios.h>
 57 #include <linux/in.h>
 58 #include <linux/inet.h>
 59 #include <linux/netdevice.h>
 60 #include <linux/etherdevice.h>
 61 #include <linux/proc_fs.h>
 62 #include <linux/stat.h>
 63 #include <linux/init.h>
 64 
 65 #include <net/snmp.h>
 66 #include <net/ip.h>
 67 #include <net/protocol.h>
 68 #include <net/route.h>
 69 #include <net/xfrm.h>
 70 #include <linux/skbuff.h>
 71 #include <net/sock.h>
 72 #include <net/arp.h>
 73 #include <net/icmp.h>
 74 #include <net/checksum.h>
 75 #include <net/inetpeer.h>
 76 #include <net/lwtunnel.h>
 77 #include <linux/bpf-cgroup.h>
 78 #include <linux/igmp.h>
 79 #include <linux/netfilter_ipv4.h>
 80 #include <linux/netfilter_bridge.h>
 81 #include <linux/netlink.h>
 82 #include <linux/tcp.h>
 83 
 84 static int
 85 ip_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
 86             unsigned int mtu,
 87             int (*output)(struct net *, struct sock *, struct sk_buff *));
 88 
 89 /* Generate a checksum for an outgoing IP datagram. */
 90 void ip_send_check(struct iphdr *iph)
 91 {
 92         iph->check = 0;
 93         iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
 94 }
 95 EXPORT_SYMBOL(ip_send_check);
 96 
 97 int __ip_local_out(struct net *net, struct sock *sk, struct sk_buff *skb)
 98 {
 99         struct iphdr *iph = ip_hdr(skb);
100 
101         iph->tot_len = htons(skb->len);
102         ip_send_check(iph);
103 
104         /* if egress device is enslaved to an L3 master device pass the
105          * skb to its handler for processing
106          */
107         skb = l3mdev_ip_out(sk, skb);
108         if (unlikely(!skb))
109                 return 0;
110 
111         skb->protocol = htons(ETH_P_IP);
112 
113         return nf_hook(NFPROTO_IPV4, NF_INET_LOCAL_OUT,
114                        net, sk, skb, NULL, skb_dst(skb)->dev,
115                        dst_output);
116 }
117 
118 int ip_local_out(struct net *net, struct sock *sk, struct sk_buff *skb)
119 {
120         int err;
121 
122         err = __ip_local_out(net, sk, skb);
123         if (likely(err == 1))
124                 err = dst_output(net, sk, skb);
125 
126         return err;
127 }
128 EXPORT_SYMBOL_GPL(ip_local_out);
129 
130 static inline int ip_select_ttl(struct inet_sock *inet, struct dst_entry *dst)
131 {
132         int ttl = inet->uc_ttl;
133 
134         if (ttl < 0)
135                 ttl = ip4_dst_hoplimit(dst);
136         return ttl;
137 }
138 
139 /*
140  *              Add an ip header to a skbuff and send it out.
141  *
142  */
143 int ip_build_and_send_pkt(struct sk_buff *skb, const struct sock *sk,
144                           __be32 saddr, __be32 daddr, struct ip_options_rcu *opt)
145 {
146         struct inet_sock *inet = inet_sk(sk);
147         struct rtable *rt = skb_rtable(skb);
148         struct net *net = sock_net(sk);
149         struct iphdr *iph;
150 
151         /* Build the IP header. */
152         skb_push(skb, sizeof(struct iphdr) + (opt ? opt->opt.optlen : 0));
153         skb_reset_network_header(skb);
154         iph = ip_hdr(skb);
155         iph->version  = 4;
156         iph->ihl      = 5;
157         iph->tos      = inet->tos;
158         iph->ttl      = ip_select_ttl(inet, &rt->dst);
159         iph->daddr    = (opt && opt->opt.srr ? opt->opt.faddr : daddr);
160         iph->saddr    = saddr;
161         iph->protocol = sk->sk_protocol;
162         if (ip_dont_fragment(sk, &rt->dst)) {
163                 iph->frag_off = htons(IP_DF);
164                 iph->id = 0;
165         } else {
166                 iph->frag_off = 0;
167                 __ip_select_ident(net, iph, 1);
168         }
169 
170         if (opt && opt->opt.optlen) {
171                 iph->ihl += opt->opt.optlen>>2;
172                 ip_options_build(skb, &opt->opt, daddr, rt, 0);
173         }
174 
175         skb->priority = sk->sk_priority;
176         if (!skb->mark)
177                 skb->mark = sk->sk_mark;
178 
179         /* Send it out. */
180         return ip_local_out(net, skb->sk, skb);
181 }
182 EXPORT_SYMBOL_GPL(ip_build_and_send_pkt);
183 
184 static int ip_finish_output2(struct net *net, struct sock *sk, struct sk_buff *skb)
185 {
186         struct dst_entry *dst = skb_dst(skb);
187         struct rtable *rt = (struct rtable *)dst;
188         struct net_device *dev = dst->dev;
189         unsigned int hh_len = LL_RESERVED_SPACE(dev);
190         struct neighbour *neigh;
191         u32 nexthop;
192 
193         if (rt->rt_type == RTN_MULTICAST) {
194                 IP_UPD_PO_STATS(net, IPSTATS_MIB_OUTMCAST, skb->len);
195         } else if (rt->rt_type == RTN_BROADCAST)
196                 IP_UPD_PO_STATS(net, IPSTATS_MIB_OUTBCAST, skb->len);
197 
198         /* Be paranoid, rather than too clever. */
199         if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) {
200                 struct sk_buff *skb2;
201 
202                 skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev));
203                 if (!skb2) {
204                         kfree_skb(skb);
205                         return -ENOMEM;
206                 }
207                 if (skb->sk)
208                         skb_set_owner_w(skb2, skb->sk);
209                 consume_skb(skb);
210                 skb = skb2;
211         }
212 
213         if (lwtunnel_xmit_redirect(dst->lwtstate)) {
214                 int res = lwtunnel_xmit(skb);
215 
216                 if (res < 0 || res == LWTUNNEL_XMIT_DONE)
217                         return res;
218         }
219 
220         rcu_read_lock_bh();
221         nexthop = (__force u32) rt_nexthop(rt, ip_hdr(skb)->daddr);
222         neigh = __ipv4_neigh_lookup_noref(dev, nexthop);
223         if (unlikely(!neigh))
224                 neigh = __neigh_create(&arp_tbl, &nexthop, dev, false);
225         if (!IS_ERR(neigh)) {
226                 int res;
227 
228                 sock_confirm_neigh(skb, neigh);
229                 res = neigh_output(neigh, skb);
230 
231                 rcu_read_unlock_bh();
232                 return res;
233         }
234         rcu_read_unlock_bh();
235 
236         net_dbg_ratelimited("%s: No header cache and no neighbour!\n",
237                             __func__);
238         kfree_skb(skb);
239         return -EINVAL;
240 }
241 
242 static int ip_finish_output_gso(struct net *net, struct sock *sk,
243                                 struct sk_buff *skb, unsigned int mtu)
244 {
245         netdev_features_t features;
246         struct sk_buff *segs;
247         int ret = 0;
248 
249         /* common case: seglen is <= mtu
250          */
251         if (skb_gso_validate_mtu(skb, mtu))
252                 return ip_finish_output2(net, sk, skb);
253 
254         /* Slowpath -  GSO segment length exceeds the egress MTU.
255          *
256          * This can happen in several cases:
257          *  - Forwarding of a TCP GRO skb, when DF flag is not set.
258          *  - Forwarding of an skb that arrived on a virtualization interface
259          *    (virtio-net/vhost/tap) with TSO/GSO size set by other network
260          *    stack.
261          *  - Local GSO skb transmitted on an NETIF_F_TSO tunnel stacked over an
262          *    interface with a smaller MTU.
263          *  - Arriving GRO skb (or GSO skb in a virtualized environment) that is
264          *    bridged to a NETIF_F_TSO tunnel stacked over an interface with an
265          *    insufficent MTU.
266          */
267         features = netif_skb_features(skb);
268         BUILD_BUG_ON(sizeof(*IPCB(skb)) > SKB_SGO_CB_OFFSET);
269         segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK);
270         if (IS_ERR_OR_NULL(segs)) {
271                 kfree_skb(skb);
272                 return -ENOMEM;
273         }
274 
275         consume_skb(skb);
276 
277         do {
278                 struct sk_buff *nskb = segs->next;
279                 int err;
280 
281                 segs->next = NULL;
282                 err = ip_fragment(net, sk, segs, mtu, ip_finish_output2);
283 
284                 if (err && ret == 0)
285                         ret = err;
286                 segs = nskb;
287         } while (segs);
288 
289         return ret;
290 }
291 
292 static int ip_finish_output(struct net *net, struct sock *sk, struct sk_buff *skb)
293 {
294         unsigned int mtu;
295         int ret;
296 
297         ret = BPF_CGROUP_RUN_PROG_INET_EGRESS(sk, skb);
298         if (ret) {
299                 kfree_skb(skb);
300                 return ret;
301         }
302 
303 #if defined(CONFIG_NETFILTER) && defined(CONFIG_XFRM)
304         /* Policy lookup after SNAT yielded a new policy */
305         if (skb_dst(skb)->xfrm) {
306                 IPCB(skb)->flags |= IPSKB_REROUTED;
307                 return dst_output(net, sk, skb);
308         }
309 #endif
310         mtu = ip_skb_dst_mtu(sk, skb);
311         if (skb_is_gso(skb))
312                 return ip_finish_output_gso(net, sk, skb, mtu);
313 
314         if (skb->len > mtu || (IPCB(skb)->flags & IPSKB_FRAG_PMTU))
315                 return ip_fragment(net, sk, skb, mtu, ip_finish_output2);
316 
317         return ip_finish_output2(net, sk, skb);
318 }
319 
320 static int ip_mc_finish_output(struct net *net, struct sock *sk,
321                                struct sk_buff *skb)
322 {
323         int ret;
324 
325         ret = BPF_CGROUP_RUN_PROG_INET_EGRESS(sk, skb);
326         if (ret) {
327                 kfree_skb(skb);
328                 return ret;
329         }
330 
331         return dev_loopback_xmit(net, sk, skb);
332 }
333 
334 int ip_mc_output(struct net *net, struct sock *sk, struct sk_buff *skb)
335 {
336         struct rtable *rt = skb_rtable(skb);
337         struct net_device *dev = rt->dst.dev;
338 
339         /*
340          *      If the indicated interface is up and running, send the packet.
341          */
342         IP_UPD_PO_STATS(net, IPSTATS_MIB_OUT, skb->len);
343 
344         skb->dev = dev;
345         skb->protocol = htons(ETH_P_IP);
346 
347         /*
348          *      Multicasts are looped back for other local users
349          */
350 
351         if (rt->rt_flags&RTCF_MULTICAST) {
352                 if (sk_mc_loop(sk)
353 #ifdef CONFIG_IP_MROUTE
354                 /* Small optimization: do not loopback not local frames,
355                    which returned after forwarding; they will be  dropped
356                    by ip_mr_input in any case.
357                    Note, that local frames are looped back to be delivered
358                    to local recipients.
359 
360                    This check is duplicated in ip_mr_input at the moment.
361                  */
362                     &&
363                     ((rt->rt_flags & RTCF_LOCAL) ||
364                      !(IPCB(skb)->flags & IPSKB_FORWARDED))
365 #endif
366                    ) {
367                         struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
368                         if (newskb)
369                                 NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING,
370                                         net, sk, newskb, NULL, newskb->dev,
371                                         ip_mc_finish_output);
372                 }
373 
374                 /* Multicasts with ttl 0 must not go beyond the host */
375 
376                 if (ip_hdr(skb)->ttl == 0) {
377                         kfree_skb(skb);
378                         return 0;
379                 }
380         }
381 
382         if (rt->rt_flags&RTCF_BROADCAST) {
383                 struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
384                 if (newskb)
385                         NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING,
386                                 net, sk, newskb, NULL, newskb->dev,
387                                 ip_mc_finish_output);
388         }
389 
390         return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
391                             net, sk, skb, NULL, skb->dev,
392                             ip_finish_output,
393                             !(IPCB(skb)->flags & IPSKB_REROUTED));
394 }
395 
396 int ip_output(struct net *net, struct sock *sk, struct sk_buff *skb)
397 {
398         struct net_device *dev = skb_dst(skb)->dev;
399 
400         IP_UPD_PO_STATS(net, IPSTATS_MIB_OUT, skb->len);
401 
402         skb->dev = dev;
403         skb->protocol = htons(ETH_P_IP);
404 
405         return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
406                             net, sk, skb, NULL, dev,
407                             ip_finish_output,
408                             !(IPCB(skb)->flags & IPSKB_REROUTED));
409 }
410 
411 /*
412  * copy saddr and daddr, possibly using 64bit load/stores
413  * Equivalent to :
414  *   iph->saddr = fl4->saddr;
415  *   iph->daddr = fl4->daddr;
416  */
417 static void ip_copy_addrs(struct iphdr *iph, const struct flowi4 *fl4)
418 {
419         BUILD_BUG_ON(offsetof(typeof(*fl4), daddr) !=
420                      offsetof(typeof(*fl4), saddr) + sizeof(fl4->saddr));
421         memcpy(&iph->saddr, &fl4->saddr,
422                sizeof(fl4->saddr) + sizeof(fl4->daddr));
423 }
424 
425 /* Note: skb->sk can be different from sk, in case of tunnels */
426 int ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl)
427 {
428         struct inet_sock *inet = inet_sk(sk);
429         struct net *net = sock_net(sk);
430         struct ip_options_rcu *inet_opt;
431         struct flowi4 *fl4;
432         struct rtable *rt;
433         struct iphdr *iph;
434         int res;
435 
436         /* Skip all of this if the packet is already routed,
437          * f.e. by something like SCTP.
438          */
439         rcu_read_lock();
440         inet_opt = rcu_dereference(inet->inet_opt);
441         fl4 = &fl->u.ip4;
442         rt = skb_rtable(skb);
443         if (rt)
444                 goto packet_routed;
445 
446         /* Make sure we can route this packet. */
447         rt = (struct rtable *)__sk_dst_check(sk, 0);
448         if (!rt) {
449                 __be32 daddr;
450 
451                 /* Use correct destination address if we have options. */
452                 daddr = inet->inet_daddr;
453                 if (inet_opt && inet_opt->opt.srr)
454                         daddr = inet_opt->opt.faddr;
455 
456                 /* If this fails, retransmit mechanism of transport layer will
457                  * keep trying until route appears or the connection times
458                  * itself out.
459                  */
460                 rt = ip_route_output_ports(net, fl4, sk,
461                                            daddr, inet->inet_saddr,
462                                            inet->inet_dport,
463                                            inet->inet_sport,
464                                            sk->sk_protocol,
465                                            RT_CONN_FLAGS(sk),
466                                            sk->sk_bound_dev_if);
467                 if (IS_ERR(rt))
468                         goto no_route;
469                 sk_setup_caps(sk, &rt->dst);
470         }
471         skb_dst_set_noref(skb, &rt->dst);
472 
473 packet_routed:
474         if (inet_opt && inet_opt->opt.is_strictroute && rt->rt_uses_gateway)
475                 goto no_route;
476 
477         /* OK, we know where to send it, allocate and build IP header. */
478         skb_push(skb, sizeof(struct iphdr) + (inet_opt ? inet_opt->opt.optlen : 0));
479         skb_reset_network_header(skb);
480         iph = ip_hdr(skb);
481         *((__be16 *)iph) = htons((4 << 12) | (5 << 8) | (inet->tos & 0xff));
482         if (ip_dont_fragment(sk, &rt->dst) && !skb->ignore_df)
483                 iph->frag_off = htons(IP_DF);
484         else
485                 iph->frag_off = 0;
486         iph->ttl      = ip_select_ttl(inet, &rt->dst);
487         iph->protocol = sk->sk_protocol;
488         ip_copy_addrs(iph, fl4);
489 
490         /* Transport layer set skb->h.foo itself. */
491 
492         if (inet_opt && inet_opt->opt.optlen) {
493                 iph->ihl += inet_opt->opt.optlen >> 2;
494                 ip_options_build(skb, &inet_opt->opt, inet->inet_daddr, rt, 0);
495         }
496 
497         ip_select_ident_segs(net, skb, sk,
498                              skb_shinfo(skb)->gso_segs ?: 1);
499 
500         /* TODO : should we use skb->sk here instead of sk ? */
501         skb->priority = sk->sk_priority;
502         skb->mark = sk->sk_mark;
503 
504         res = ip_local_out(net, sk, skb);
505         rcu_read_unlock();
506         return res;
507 
508 no_route:
509         rcu_read_unlock();
510         IP_INC_STATS(net, IPSTATS_MIB_OUTNOROUTES);
511         kfree_skb(skb);
512         return -EHOSTUNREACH;
513 }
514 EXPORT_SYMBOL(ip_queue_xmit);
515 
516 static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
517 {
518         to->pkt_type = from->pkt_type;
519         to->priority = from->priority;
520         to->protocol = from->protocol;
521         skb_dst_drop(to);
522         skb_dst_copy(to, from);
523         to->dev = from->dev;
524         to->mark = from->mark;
525 
526         /* Copy the flags to each fragment. */
527         IPCB(to)->flags = IPCB(from)->flags;
528 
529 #ifdef CONFIG_NET_SCHED
530         to->tc_index = from->tc_index;
531 #endif
532         nf_copy(to, from);
533 #if IS_ENABLED(CONFIG_IP_VS)
534         to->ipvs_property = from->ipvs_property;
535 #endif
536         skb_copy_secmark(to, from);
537 }
538 
539 static int ip_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
540                        unsigned int mtu,
541                        int (*output)(struct net *, struct sock *, struct sk_buff *))
542 {
543         struct iphdr *iph = ip_hdr(skb);
544 
545         if ((iph->frag_off & htons(IP_DF)) == 0)
546                 return ip_do_fragment(net, sk, skb, output);
547 
548         if (unlikely(!skb->ignore_df ||
549                      (IPCB(skb)->frag_max_size &&
550                       IPCB(skb)->frag_max_size > mtu))) {
551                 IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
552                 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
553                           htonl(mtu));
554                 kfree_skb(skb);
555                 return -EMSGSIZE;
556         }
557 
558         return ip_do_fragment(net, sk, skb, output);
559 }
560 
561 /*
562  *      This IP datagram is too large to be sent in one piece.  Break it up into
563  *      smaller pieces (each of size equal to IP header plus
564  *      a block of the data of the original IP data part) that will yet fit in a
565  *      single device frame, and queue such a frame for sending.
566  */
567 
568 int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
569                    int (*output)(struct net *, struct sock *, struct sk_buff *))
570 {
571         struct iphdr *iph;
572         int ptr;
573         struct sk_buff *skb2;
574         unsigned int mtu, hlen, left, len, ll_rs;
575         int offset;
576         __be16 not_last_frag;
577         struct rtable *rt = skb_rtable(skb);
578         int err = 0;
579 
580         /* for offloaded checksums cleanup checksum before fragmentation */
581         if (skb->ip_summed == CHECKSUM_PARTIAL &&
582             (err = skb_checksum_help(skb)))
583                 goto fail;
584 
585         /*
586          *      Point into the IP datagram header.
587          */
588 
589         iph = ip_hdr(skb);
590 
591         mtu = ip_skb_dst_mtu(sk, skb);
592         if (IPCB(skb)->frag_max_size && IPCB(skb)->frag_max_size < mtu)
593                 mtu = IPCB(skb)->frag_max_size;
594 
595         /*
596          *      Setup starting values.
597          */
598 
599         hlen = iph->ihl * 4;
600         mtu = mtu - hlen;       /* Size of data space */
601         IPCB(skb)->flags |= IPSKB_FRAG_COMPLETE;
602         ll_rs = LL_RESERVED_SPACE(rt->dst.dev);
603 
604         /* When frag_list is given, use it. First, check its validity:
605          * some transformers could create wrong frag_list or break existing
606          * one, it is not prohibited. In this case fall back to copying.
607          *
608          * LATER: this step can be merged to real generation of fragments,
609          * we can switch to copy when see the first bad fragment.
610          */
611         if (skb_has_frag_list(skb)) {
612                 struct sk_buff *frag, *frag2;
613                 unsigned int first_len = skb_pagelen(skb);
614 
615                 if (first_len - hlen > mtu ||
616                     ((first_len - hlen) & 7) ||
617                     ip_is_fragment(iph) ||
618                     skb_cloned(skb) ||
619                     skb_headroom(skb) < ll_rs)
620                         goto slow_path;
621 
622                 skb_walk_frags(skb, frag) {
623                         /* Correct geometry. */
624                         if (frag->len > mtu ||
625                             ((frag->len & 7) && frag->next) ||
626                             skb_headroom(frag) < hlen + ll_rs)
627                                 goto slow_path_clean;
628 
629                         /* Partially cloned skb? */
630                         if (skb_shared(frag))
631                                 goto slow_path_clean;
632 
633                         BUG_ON(frag->sk);
634                         if (skb->sk) {
635                                 frag->sk = skb->sk;
636                                 frag->destructor = sock_wfree;
637                         }
638                         skb->truesize -= frag->truesize;
639                 }
640 
641                 /* Everything is OK. Generate! */
642 
643                 err = 0;
644                 offset = 0;
645                 frag = skb_shinfo(skb)->frag_list;
646                 skb_frag_list_init(skb);
647                 skb->data_len = first_len - skb_headlen(skb);
648                 skb->len = first_len;
649                 iph->tot_len = htons(first_len);
650                 iph->frag_off = htons(IP_MF);
651                 ip_send_check(iph);
652 
653                 for (;;) {
654                         /* Prepare header of the next frame,
655                          * before previous one went down. */
656                         if (frag) {
657                                 frag->ip_summed = CHECKSUM_NONE;
658                                 skb_reset_transport_header(frag);
659                                 __skb_push(frag, hlen);
660                                 skb_reset_network_header(frag);
661                                 memcpy(skb_network_header(frag), iph, hlen);
662                                 iph = ip_hdr(frag);
663                                 iph->tot_len = htons(frag->len);
664                                 ip_copy_metadata(frag, skb);
665                                 if (offset == 0)
666                                         ip_options_fragment(frag);
667                                 offset += skb->len - hlen;
668                                 iph->frag_off = htons(offset>>3);
669                                 if (frag->next)
670                                         iph->frag_off |= htons(IP_MF);
671                                 /* Ready, complete checksum */
672                                 ip_send_check(iph);
673                         }
674 
675                         err = output(net, sk, skb);
676 
677                         if (!err)
678                                 IP_INC_STATS(net, IPSTATS_MIB_FRAGCREATES);
679                         if (err || !frag)
680                                 break;
681 
682                         skb = frag;
683                         frag = skb->next;
684                         skb->next = NULL;
685                 }
686 
687                 if (err == 0) {
688                         IP_INC_STATS(net, IPSTATS_MIB_FRAGOKS);
689                         return 0;
690                 }
691 
692                 while (frag) {
693                         skb = frag->next;
694                         kfree_skb(frag);
695                         frag = skb;
696                 }
697                 IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
698                 return err;
699 
700 slow_path_clean:
701                 skb_walk_frags(skb, frag2) {
702                         if (frag2 == frag)
703                                 break;
704                         frag2->sk = NULL;
705                         frag2->destructor = NULL;
706                         skb->truesize += frag2->truesize;
707                 }
708         }
709 
710 slow_path:
711         iph = ip_hdr(skb);
712 
713         left = skb->len - hlen;         /* Space per frame */
714         ptr = hlen;             /* Where to start from */
715 
716         /*
717          *      Fragment the datagram.
718          */
719 
720         offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3;
721         not_last_frag = iph->frag_off & htons(IP_MF);
722 
723         /*
724          *      Keep copying data until we run out.
725          */
726 
727         while (left > 0) {
728                 len = left;
729                 /* IF: it doesn't fit, use 'mtu' - the data space left */
730                 if (len > mtu)
731                         len = mtu;
732                 /* IF: we are not sending up to and including the packet end
733                    then align the next start on an eight byte boundary */
734                 if (len < left) {
735                         len &= ~7;
736                 }
737 
738                 /* Allocate buffer */
739                 skb2 = alloc_skb(len + hlen + ll_rs, GFP_ATOMIC);
740                 if (!skb2) {
741                         err = -ENOMEM;
742                         goto fail;
743                 }
744 
745                 /*
746                  *      Set up data on packet
747                  */
748 
749                 ip_copy_metadata(skb2, skb);
750                 skb_reserve(skb2, ll_rs);
751                 skb_put(skb2, len + hlen);
752                 skb_reset_network_header(skb2);
753                 skb2->transport_header = skb2->network_header + hlen;
754 
755                 /*
756                  *      Charge the memory for the fragment to any owner
757                  *      it might possess
758                  */
759 
760                 if (skb->sk)
761                         skb_set_owner_w(skb2, skb->sk);
762 
763                 /*
764                  *      Copy the packet header into the new buffer.
765                  */
766 
767                 skb_copy_from_linear_data(skb, skb_network_header(skb2), hlen);
768 
769                 /*
770                  *      Copy a block of the IP datagram.
771                  */
772                 if (skb_copy_bits(skb, ptr, skb_transport_header(skb2), len))
773                         BUG();
774                 left -= len;
775 
776                 /*
777                  *      Fill in the new header fields.
778                  */
779                 iph = ip_hdr(skb2);
780                 iph->frag_off = htons((offset >> 3));
781 
782                 if (IPCB(skb)->flags & IPSKB_FRAG_PMTU)
783                         iph->frag_off |= htons(IP_DF);
784 
785                 /* ANK: dirty, but effective trick. Upgrade options only if
786                  * the segment to be fragmented was THE FIRST (otherwise,
787                  * options are already fixed) and make it ONCE
788                  * on the initial skb, so that all the following fragments
789                  * will inherit fixed options.
790                  */
791                 if (offset == 0)
792                         ip_options_fragment(skb);
793 
794                 /*
795                  *      Added AC : If we are fragmenting a fragment that's not the
796                  *                 last fragment then keep MF on each bit
797                  */
798                 if (left > 0 || not_last_frag)
799                         iph->frag_off |= htons(IP_MF);
800                 ptr += len;
801                 offset += len;
802 
803                 /*
804                  *      Put this fragment into the sending queue.
805                  */
806                 iph->tot_len = htons(len + hlen);
807 
808                 ip_send_check(iph);
809 
810                 err = output(net, sk, skb2);
811                 if (err)
812                         goto fail;
813 
814                 IP_INC_STATS(net, IPSTATS_MIB_FRAGCREATES);
815         }
816         consume_skb(skb);
817         IP_INC_STATS(net, IPSTATS_MIB_FRAGOKS);
818         return err;
819 
820 fail:
821         kfree_skb(skb);
822         IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
823         return err;
824 }
825 EXPORT_SYMBOL(ip_do_fragment);
826 
827 int
828 ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
829 {
830         struct msghdr *msg = from;
831 
832         if (skb->ip_summed == CHECKSUM_PARTIAL) {
833                 if (!copy_from_iter_full(to, len, &msg->msg_iter))
834                         return -EFAULT;
835         } else {
836                 __wsum csum = 0;
837                 if (!csum_and_copy_from_iter_full(to, len, &csum, &msg->msg_iter))
838                         return -EFAULT;
839                 skb->csum = csum_block_add(skb->csum, csum, odd);
840         }
841         return 0;
842 }
843 EXPORT_SYMBOL(ip_generic_getfrag);
844 
845 static inline __wsum
846 csum_page(struct page *page, int offset, int copy)
847 {
848         char *kaddr;
849         __wsum csum;
850         kaddr = kmap(page);
851         csum = csum_partial(kaddr + offset, copy, 0);
852         kunmap(page);
853         return csum;
854 }
855 
856 static inline int ip_ufo_append_data(struct sock *sk,
857                         struct sk_buff_head *queue,
858                         int getfrag(void *from, char *to, int offset, int len,
859                                int odd, struct sk_buff *skb),
860                         void *from, int length, int hh_len, int fragheaderlen,
861                         int transhdrlen, int maxfraglen, unsigned int flags)
862 {
863         struct sk_buff *skb;
864         int err;
865 
866         /* There is support for UDP fragmentation offload by network
867          * device, so create one single skb packet containing complete
868          * udp datagram
869          */
870         skb = skb_peek_tail(queue);
871         if (!skb) {
872                 skb = sock_alloc_send_skb(sk,
873                         hh_len + fragheaderlen + transhdrlen + 20,
874                         (flags & MSG_DONTWAIT), &err);
875 
876                 if (!skb)
877                         return err;
878 
879                 /* reserve space for Hardware header */
880                 skb_reserve(skb, hh_len);
881 
882                 /* create space for UDP/IP header */
883                 skb_put(skb, fragheaderlen + transhdrlen);
884 
885                 /* initialize network header pointer */
886                 skb_reset_network_header(skb);
887 
888                 /* initialize protocol header pointer */
889                 skb->transport_header = skb->network_header + fragheaderlen;
890 
891                 skb->csum = 0;
892 
893                 if (flags & MSG_CONFIRM)
894                         skb_set_dst_pending_confirm(skb, 1);
895 
896                 __skb_queue_tail(queue, skb);
897         } else if (skb_is_gso(skb)) {
898                 goto append;
899         }
900 
901         skb->ip_summed = CHECKSUM_PARTIAL;
902         /* specify the length of each IP datagram fragment */
903         skb_shinfo(skb)->gso_size = maxfraglen - fragheaderlen;
904         skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
905 
906 append:
907         return skb_append_datato_frags(sk, skb, getfrag, from,
908                                        (length - transhdrlen));
909 }
910 
911 static int __ip_append_data(struct sock *sk,
912                             struct flowi4 *fl4,
913                             struct sk_buff_head *queue,
914                             struct inet_cork *cork,
915                             struct page_frag *pfrag,
916                             int getfrag(void *from, char *to, int offset,
917                                         int len, int odd, struct sk_buff *skb),
918                             void *from, int length, int transhdrlen,
919                             unsigned int flags)
920 {
921         struct inet_sock *inet = inet_sk(sk);
922         struct sk_buff *skb;
923 
924         struct ip_options *opt = cork->opt;
925         int hh_len;
926         int exthdrlen;
927         int mtu;
928         int copy;
929         int err;
930         int offset = 0;
931         unsigned int maxfraglen, fragheaderlen, maxnonfragsize;
932         int csummode = CHECKSUM_NONE;
933         struct rtable *rt = (struct rtable *)cork->dst;
934         u32 tskey = 0;
935 
936         skb = skb_peek_tail(queue);
937 
938         exthdrlen = !skb ? rt->dst.header_len : 0;
939         mtu = cork->fragsize;
940         if (cork->tx_flags & SKBTX_ANY_SW_TSTAMP &&
941             sk->sk_tsflags & SOF_TIMESTAMPING_OPT_ID)
942                 tskey = sk->sk_tskey++;
943 
944         hh_len = LL_RESERVED_SPACE(rt->dst.dev);
945 
946         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
947         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
948         maxnonfragsize = ip_sk_ignore_df(sk) ? 0xFFFF : mtu;
949 
950         if (cork->length + length > maxnonfragsize - fragheaderlen) {
951                 ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
952                                mtu - (opt ? opt->optlen : 0));
953                 return -EMSGSIZE;
954         }
955 
956         /*
957          * transhdrlen > 0 means that this is the first fragment and we wish
958          * it won't be fragmented in the future.
959          */
960         if (transhdrlen &&
961             length + fragheaderlen <= mtu &&
962             rt->dst.dev->features & (NETIF_F_HW_CSUM | NETIF_F_IP_CSUM) &&
963             !(flags & MSG_MORE) &&
964             !exthdrlen)
965                 csummode = CHECKSUM_PARTIAL;
966 
967         cork->length += length;
968         if ((skb && skb_is_gso(skb)) ||
969             (((length + (skb ? skb->len : fragheaderlen)) > mtu) &&
970             (skb_queue_len(queue) <= 1) &&
971             (sk->sk_protocol == IPPROTO_UDP) &&
972             (rt->dst.dev->features & NETIF_F_UFO) && !dst_xfrm(&rt->dst) &&
973             (sk->sk_type == SOCK_DGRAM) && !sk->sk_no_check_tx)) {
974                 err = ip_ufo_append_data(sk, queue, getfrag, from, length,
975                                          hh_len, fragheaderlen, transhdrlen,
976                                          maxfraglen, flags);
977                 if (err)
978                         goto error;
979                 return 0;
980         }
981 
982         /* So, what's going on in the loop below?
983          *
984          * We use calculated fragment length to generate chained skb,
985          * each of segments is IP fragment ready for sending to network after
986          * adding appropriate IP header.
987          */
988 
989         if (!skb)
990                 goto alloc_new_skb;
991 
992         while (length > 0) {
993                 /* Check if the remaining data fits into current packet. */
994                 copy = mtu - skb->len;
995                 if (copy < length)
996                         copy = maxfraglen - skb->len;
997                 if (copy <= 0) {
998                         char *data;
999                         unsigned int datalen;
1000                         unsigned int fraglen;
1001                         unsigned int fraggap;
1002                         unsigned int alloclen;
1003                         struct sk_buff *skb_prev;
1004 alloc_new_skb:
1005                         skb_prev = skb;
1006                         if (skb_prev)
1007                                 fraggap = skb_prev->len - maxfraglen;
1008                         else
1009                                 fraggap = 0;
1010 
1011                         /*
1012                          * If remaining data exceeds the mtu,
1013                          * we know we need more fragment(s).
1014                          */
1015                         datalen = length + fraggap;
1016                         if (datalen > mtu - fragheaderlen)
1017                                 datalen = maxfraglen - fragheaderlen;
1018                         fraglen = datalen + fragheaderlen;
1019 
1020                         if ((flags & MSG_MORE) &&
1021                             !(rt->dst.dev->features&NETIF_F_SG))
1022                                 alloclen = mtu;
1023                         else
1024                                 alloclen = fraglen;
1025 
1026                         alloclen += exthdrlen;
1027 
1028                         /* The last fragment gets additional space at tail.
1029                          * Note, with MSG_MORE we overallocate on fragments,
1030                          * because we have no idea what fragment will be
1031                          * the last.
1032                          */
1033                         if (datalen == length + fraggap)
1034                                 alloclen += rt->dst.trailer_len;
1035 
1036                         if (transhdrlen) {
1037                                 skb = sock_alloc_send_skb(sk,
1038                                                 alloclen + hh_len + 15,
1039                                                 (flags & MSG_DONTWAIT), &err);
1040                         } else {
1041                                 skb = NULL;
1042                                 if (refcount_read(&sk->sk_wmem_alloc) <=
1043                                     2 * sk->sk_sndbuf)
1044                                         skb = sock_wmalloc(sk,
1045                                                            alloclen + hh_len + 15, 1,
1046                                                            sk->sk_allocation);
1047                                 if (unlikely(!skb))
1048                                         err = -ENOBUFS;
1049                         }
1050                         if (!skb)
1051                                 goto error;
1052 
1053                         /*
1054                          *      Fill in the control structures
1055                          */
1056                         skb->ip_summed = csummode;
1057                         skb->csum = 0;
1058                         skb_reserve(skb, hh_len);
1059 
1060                         /* only the initial fragment is time stamped */
1061                         skb_shinfo(skb)->tx_flags = cork->tx_flags;
1062                         cork->tx_flags = 0;
1063                         skb_shinfo(skb)->tskey = tskey;
1064                         tskey = 0;
1065 
1066                         /*
1067                          *      Find where to start putting bytes.
1068                          */
1069                         data = skb_put(skb, fraglen + exthdrlen);
1070                         skb_set_network_header(skb, exthdrlen);
1071                         skb->transport_header = (skb->network_header +
1072                                                  fragheaderlen);
1073                         data += fragheaderlen + exthdrlen;
1074 
1075                         if (fraggap) {
1076                                 skb->csum = skb_copy_and_csum_bits(
1077                                         skb_prev, maxfraglen,
1078                                         data + transhdrlen, fraggap, 0);
1079                                 skb_prev->csum = csum_sub(skb_prev->csum,
1080                                                           skb->csum);
1081                                 data += fraggap;
1082                                 pskb_trim_unique(skb_prev, maxfraglen);
1083                         }
1084 
1085                         copy = datalen - transhdrlen - fraggap;
1086                         if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
1087                                 err = -EFAULT;
1088                                 kfree_skb(skb);
1089                                 goto error;
1090                         }
1091 
1092                         offset += copy;
1093                         length -= datalen - fraggap;
1094                         transhdrlen = 0;
1095                         exthdrlen = 0;
1096                         csummode = CHECKSUM_NONE;
1097 
1098                         if ((flags & MSG_CONFIRM) && !skb_prev)
1099                                 skb_set_dst_pending_confirm(skb, 1);
1100 
1101                         /*
1102                          * Put the packet on the pending queue.
1103                          */
1104                         __skb_queue_tail(queue, skb);
1105                         continue;
1106                 }
1107 
1108                 if (copy > length)
1109                         copy = length;
1110 
1111                 if (!(rt->dst.dev->features&NETIF_F_SG)) {
1112                         unsigned int off;
1113 
1114                         off = skb->len;
1115                         if (getfrag(from, skb_put(skb, copy),
1116                                         offset, copy, off, skb) < 0) {
1117                                 __skb_trim(skb, off);
1118                                 err = -EFAULT;
1119                                 goto error;
1120                         }
1121                 } else {
1122                         int i = skb_shinfo(skb)->nr_frags;
1123 
1124                         err = -ENOMEM;
1125                         if (!sk_page_frag_refill(sk, pfrag))
1126                                 goto error;
1127 
1128                         if (!skb_can_coalesce(skb, i, pfrag->page,
1129                                               pfrag->offset)) {
1130                                 err = -EMSGSIZE;
1131                                 if (i == MAX_SKB_FRAGS)
1132                                         goto error;
1133 
1134                                 __skb_fill_page_desc(skb, i, pfrag->page,
1135                                                      pfrag->offset, 0);
1136                                 skb_shinfo(skb)->nr_frags = ++i;
1137                                 get_page(pfrag->page);
1138                         }
1139                         copy = min_t(int, copy, pfrag->size - pfrag->offset);
1140                         if (getfrag(from,
1141                                     page_address(pfrag->page) + pfrag->offset,
1142                                     offset, copy, skb->len, skb) < 0)
1143                                 goto error_efault;
1144 
1145                         pfrag->offset += copy;
1146                         skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
1147                         skb->len += copy;
1148                         skb->data_len += copy;
1149                         skb->truesize += copy;
1150                         refcount_add(copy, &sk->sk_wmem_alloc);
1151                 }
1152                 offset += copy;
1153                 length -= copy;
1154         }
1155 
1156         return 0;
1157 
1158 error_efault:
1159         err = -EFAULT;
1160 error:
1161         cork->length -= length;
1162         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1163         return err;
1164 }
1165 
1166 static int ip_setup_cork(struct sock *sk, struct inet_cork *cork,
1167                          struct ipcm_cookie *ipc, struct rtable **rtp)
1168 {
1169         struct ip_options_rcu *opt;
1170         struct rtable *rt;
1171 
1172         /*
1173          * setup for corking.
1174          */
1175         opt = ipc->opt;
1176         if (opt) {
1177                 if (!cork->opt) {
1178                         cork->opt = kmalloc(sizeof(struct ip_options) + 40,
1179                                             sk->sk_allocation);
1180                         if (unlikely(!cork->opt))
1181                                 return -ENOBUFS;
1182                 }
1183                 memcpy(cork->opt, &opt->opt, sizeof(struct ip_options) + opt->opt.optlen);
1184                 cork->flags |= IPCORK_OPT;
1185                 cork->addr = ipc->addr;
1186         }
1187         rt = *rtp;
1188         if (unlikely(!rt))
1189                 return -EFAULT;
1190         /*
1191          * We steal reference to this route, caller should not release it
1192          */
1193         *rtp = NULL;
1194         cork->fragsize = ip_sk_use_pmtu(sk) ?
1195                          dst_mtu(&rt->dst) : rt->dst.dev->mtu;
1196         cork->dst = &rt->dst;
1197         cork->length = 0;
1198         cork->ttl = ipc->ttl;
1199         cork->tos = ipc->tos;
1200         cork->priority = ipc->priority;
1201         cork->tx_flags = ipc->tx_flags;
1202 
1203         return 0;
1204 }
1205 
1206 /*
1207  *      ip_append_data() and ip_append_page() can make one large IP datagram
1208  *      from many pieces of data. Each pieces will be holded on the socket
1209  *      until ip_push_pending_frames() is called. Each piece can be a page
1210  *      or non-page data.
1211  *
1212  *      Not only UDP, other transport protocols - e.g. raw sockets - can use
1213  *      this interface potentially.
1214  *
1215  *      LATER: length must be adjusted by pad at tail, when it is required.
1216  */
1217 int ip_append_data(struct sock *sk, struct flowi4 *fl4,
1218                    int getfrag(void *from, char *to, int offset, int len,
1219                                int odd, struct sk_buff *skb),
1220                    void *from, int length, int transhdrlen,
1221                    struct ipcm_cookie *ipc, struct rtable **rtp,
1222                    unsigned int flags)
1223 {
1224         struct inet_sock *inet = inet_sk(sk);
1225         int err;
1226 
1227         if (flags&MSG_PROBE)
1228                 return 0;
1229 
1230         if (skb_queue_empty(&sk->sk_write_queue)) {
1231                 err = ip_setup_cork(sk, &inet->cork.base, ipc, rtp);
1232                 if (err)
1233                         return err;
1234         } else {
1235                 transhdrlen = 0;
1236         }
1237 
1238         return __ip_append_data(sk, fl4, &sk->sk_write_queue, &inet->cork.base,
1239                                 sk_page_frag(sk), getfrag,
1240                                 from, length, transhdrlen, flags);
1241 }
1242 
1243 ssize_t ip_append_page(struct sock *sk, struct flowi4 *fl4, struct page *page,
1244                        int offset, size_t size, int flags)
1245 {
1246         struct inet_sock *inet = inet_sk(sk);
1247         struct sk_buff *skb;
1248         struct rtable *rt;
1249         struct ip_options *opt = NULL;
1250         struct inet_cork *cork;
1251         int hh_len;
1252         int mtu;
1253         int len;
1254         int err;
1255         unsigned int maxfraglen, fragheaderlen, fraggap, maxnonfragsize;
1256 
1257         if (inet->hdrincl)
1258                 return -EPERM;
1259 
1260         if (flags&MSG_PROBE)
1261                 return 0;
1262 
1263         if (skb_queue_empty(&sk->sk_write_queue))
1264                 return -EINVAL;
1265 
1266         cork = &inet->cork.base;
1267         rt = (struct rtable *)cork->dst;
1268         if (cork->flags & IPCORK_OPT)
1269                 opt = cork->opt;
1270 
1271         if (!(rt->dst.dev->features&NETIF_F_SG))
1272                 return -EOPNOTSUPP;
1273 
1274         hh_len = LL_RESERVED_SPACE(rt->dst.dev);
1275         mtu = cork->fragsize;
1276 
1277         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
1278         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
1279         maxnonfragsize = ip_sk_ignore_df(sk) ? 0xFFFF : mtu;
1280 
1281         if (cork->length + size > maxnonfragsize - fragheaderlen) {
1282                 ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
1283                                mtu - (opt ? opt->optlen : 0));
1284                 return -EMSGSIZE;
1285         }
1286 
1287         skb = skb_peek_tail(&sk->sk_write_queue);
1288         if (!skb)
1289                 return -EINVAL;
1290 
1291         if ((size + skb->len > mtu) &&
1292             (skb_queue_len(&sk->sk_write_queue) == 1) &&
1293             (sk->sk_protocol == IPPROTO_UDP) &&
1294             (rt->dst.dev->features & NETIF_F_UFO)) {
1295                 if (skb->ip_summed != CHECKSUM_PARTIAL)
1296                         return -EOPNOTSUPP;
1297 
1298                 skb_shinfo(skb)->gso_size = mtu - fragheaderlen;
1299                 skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
1300         }
1301         cork->length += size;
1302 
1303         while (size > 0) {
1304                 if (skb_is_gso(skb)) {
1305                         len = size;
1306                 } else {
1307 
1308                         /* Check if the remaining data fits into current packet. */
1309                         len = mtu - skb->len;
1310                         if (len < size)
1311                                 len = maxfraglen - skb->len;
1312                 }
1313                 if (len <= 0) {
1314                         struct sk_buff *skb_prev;
1315                         int alloclen;
1316 
1317                         skb_prev = skb;
1318                         fraggap = skb_prev->len - maxfraglen;
1319 
1320                         alloclen = fragheaderlen + hh_len + fraggap + 15;
1321                         skb = sock_wmalloc(sk, alloclen, 1, sk->sk_allocation);
1322                         if (unlikely(!skb)) {
1323                                 err = -ENOBUFS;
1324                                 goto error;
1325                         }
1326 
1327                         /*
1328                          *      Fill in the control structures
1329                          */
1330                         skb->ip_summed = CHECKSUM_NONE;
1331                         skb->csum = 0;
1332                         skb_reserve(skb, hh_len);
1333 
1334                         /*
1335                          *      Find where to start putting bytes.
1336                          */
1337                         skb_put(skb, fragheaderlen + fraggap);
1338                         skb_reset_network_header(skb);
1339                         skb->transport_header = (skb->network_header +
1340                                                  fragheaderlen);
1341                         if (fraggap) {
1342                                 skb->csum = skb_copy_and_csum_bits(skb_prev,
1343                                                                    maxfraglen,
1344                                                     skb_transport_header(skb),
1345                                                                    fraggap, 0);
1346                                 skb_prev->csum = csum_sub(skb_prev->csum,
1347                                                           skb->csum);
1348                                 pskb_trim_unique(skb_prev, maxfraglen);
1349                         }
1350 
1351                         /*
1352                          * Put the packet on the pending queue.
1353                          */
1354                         __skb_queue_tail(&sk->sk_write_queue, skb);
1355                         continue;
1356                 }
1357 
1358                 if (len > size)
1359                         len = size;
1360 
1361                 if (skb_append_pagefrags(skb, page, offset, len)) {
1362                         err = -EMSGSIZE;
1363                         goto error;
1364                 }
1365 
1366                 if (skb->ip_summed == CHECKSUM_NONE) {
1367                         __wsum csum;
1368                         csum = csum_page(page, offset, len);
1369                         skb->csum = csum_block_add(skb->csum, csum, skb->len);
1370                 }
1371 
1372                 skb->len += len;
1373                 skb->data_len += len;
1374                 skb->truesize += len;
1375                 refcount_add(len, &sk->sk_wmem_alloc);
1376                 offset += len;
1377                 size -= len;
1378         }
1379         return 0;
1380 
1381 error:
1382         cork->length -= size;
1383         IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1384         return err;
1385 }
1386 
1387 static void ip_cork_release(struct inet_cork *cork)
1388 {
1389         cork->flags &= ~IPCORK_OPT;
1390         kfree(cork->opt);
1391         cork->opt = NULL;
1392         dst_release(cork->dst);
1393         cork->dst = NULL;
1394 }
1395 
1396 /*
1397  *      Combined all pending IP fragments on the socket as one IP datagram
1398  *      and push them out.
1399  */
1400 struct sk_buff *__ip_make_skb(struct sock *sk,
1401                               struct flowi4 *fl4,
1402                               struct sk_buff_head *queue,
1403                               struct inet_cork *cork)
1404 {
1405         struct sk_buff *skb, *tmp_skb;
1406         struct sk_buff **tail_skb;
1407         struct inet_sock *inet = inet_sk(sk);
1408         struct net *net = sock_net(sk);
1409         struct ip_options *opt = NULL;
1410         struct rtable *rt = (struct rtable *)cork->dst;
1411         struct iphdr *iph;
1412         __be16 df = 0;
1413         __u8 ttl;
1414 
1415         skb = __skb_dequeue(queue);
1416         if (!skb)
1417                 goto out;
1418         tail_skb = &(skb_shinfo(skb)->frag_list);
1419 
1420         /* move skb->data to ip header from ext header */
1421         if (skb->data < skb_network_header(skb))
1422                 __skb_pull(skb, skb_network_offset(skb));
1423         while ((tmp_skb = __skb_dequeue(queue)) != NULL) {
1424                 __skb_pull(tmp_skb, skb_network_header_len(skb));
1425                 *tail_skb = tmp_skb;
1426                 tail_skb = &(tmp_skb->next);
1427                 skb->len += tmp_skb->len;
1428                 skb->data_len += tmp_skb->len;
1429                 skb->truesize += tmp_skb->truesize;
1430                 tmp_skb->destructor = NULL;
1431                 tmp_skb->sk = NULL;
1432         }
1433 
1434         /* Unless user demanded real pmtu discovery (IP_PMTUDISC_DO), we allow
1435          * to fragment the frame generated here. No matter, what transforms
1436          * how transforms change size of the packet, it will come out.
1437          */
1438         skb->ignore_df = ip_sk_ignore_df(sk);
1439 
1440         /* DF bit is set when we want to see DF on outgoing frames.
1441          * If ignore_df is set too, we still allow to fragment this frame
1442          * locally. */
1443         if (inet->pmtudisc == IP_PMTUDISC_DO ||
1444             inet->pmtudisc == IP_PMTUDISC_PROBE ||
1445             (skb->len <= dst_mtu(&rt->dst) &&
1446              ip_dont_fragment(sk, &rt->dst)))
1447                 df = htons(IP_DF);
1448 
1449         if (cork->flags & IPCORK_OPT)
1450                 opt = cork->opt;
1451 
1452         if (cork->ttl != 0)
1453                 ttl = cork->ttl;
1454         else if (rt->rt_type == RTN_MULTICAST)
1455                 ttl = inet->mc_ttl;
1456         else
1457                 ttl = ip_select_ttl(inet, &rt->dst);
1458 
1459         iph = ip_hdr(skb);
1460         iph->version = 4;
1461         iph->ihl = 5;
1462         iph->tos = (cork->tos != -1) ? cork->tos : inet->tos;
1463         iph->frag_off = df;
1464         iph->ttl = ttl;
1465         iph->protocol = sk->sk_protocol;
1466         ip_copy_addrs(iph, fl4);
1467         ip_select_ident(net, skb, sk);
1468 
1469         if (opt) {
1470                 iph->ihl += opt->optlen>>2;
1471                 ip_options_build(skb, opt, cork->addr, rt, 0);
1472         }
1473 
1474         skb->priority = (cork->tos != -1) ? cork->priority: sk->sk_priority;
1475         skb->mark = sk->sk_mark;
1476         /*
1477          * Steal rt from cork.dst to avoid a pair of atomic_inc/atomic_dec
1478          * on dst refcount
1479          */
1480         cork->dst = NULL;
1481         skb_dst_set(skb, &rt->dst);
1482 
1483         if (iph->protocol == IPPROTO_ICMP)
1484                 icmp_out_count(net, ((struct icmphdr *)
1485                         skb_transport_header(skb))->type);
1486 
1487         ip_cork_release(cork);
1488 out:
1489         return skb;
1490 }
1491 
1492 int ip_send_skb(struct net *net, struct sk_buff *skb)
1493 {
1494         int err;
1495 
1496         err = ip_local_out(net, skb->sk, skb);
1497         if (err) {
1498                 if (err > 0)
1499                         err = net_xmit_errno(err);
1500                 if (err)
1501                         IP_INC_STATS(net, IPSTATS_MIB_OUTDISCARDS);
1502         }
1503 
1504         return err;
1505 }
1506 
1507 int ip_push_pending_frames(struct sock *sk, struct flowi4 *fl4)
1508 {
1509         struct sk_buff *skb;
1510 
1511         skb = ip_finish_skb(sk, fl4);
1512         if (!skb)
1513                 return 0;
1514 
1515         /* Netfilter gets whole the not fragmented skb. */
1516         return ip_send_skb(sock_net(sk), skb);
1517 }
1518 
1519 /*
1520  *      Throw away all pending data on the socket.
1521  */
1522 static void __ip_flush_pending_frames(struct sock *sk,
1523                                       struct sk_buff_head *queue,
1524                                       struct inet_cork *cork)
1525 {
1526         struct sk_buff *skb;
1527 
1528         while ((skb = __skb_dequeue_tail(queue)) != NULL)
1529                 kfree_skb(skb);
1530 
1531         ip_cork_release(cork);
1532 }
1533 
1534 void ip_flush_pending_frames(struct sock *sk)
1535 {
1536         __ip_flush_pending_frames(sk, &sk->sk_write_queue, &inet_sk(sk)->cork.base);
1537 }
1538 
1539 struct sk_buff *ip_make_skb(struct sock *sk,
1540                             struct flowi4 *fl4,
1541                             int getfrag(void *from, char *to, int offset,
1542                                         int len, int odd, struct sk_buff *skb),
1543                             void *from, int length, int transhdrlen,
1544                             struct ipcm_cookie *ipc, struct rtable **rtp,
1545                             unsigned int flags)
1546 {
1547         struct inet_cork cork;
1548         struct sk_buff_head queue;
1549         int err;
1550 
1551         if (flags & MSG_PROBE)
1552                 return NULL;
1553 
1554         __skb_queue_head_init(&queue);
1555 
1556         cork.flags = 0;
1557         cork.addr = 0;
1558         cork.opt = NULL;
1559         err = ip_setup_cork(sk, &cork, ipc, rtp);
1560         if (err)
1561                 return ERR_PTR(err);
1562 
1563         err = __ip_append_data(sk, fl4, &queue, &cork,
1564                                &current->task_frag, getfrag,
1565                                from, length, transhdrlen, flags);
1566         if (err) {
1567                 __ip_flush_pending_frames(sk, &queue, &cork);
1568                 return ERR_PTR(err);
1569         }
1570 
1571         return __ip_make_skb(sk, fl4, &queue, &cork);
1572 }
1573 
1574 /*
1575  *      Fetch data from kernel space and fill in checksum if needed.
1576  */
1577 static int ip_reply_glue_bits(void *dptr, char *to, int offset,
1578                               int len, int odd, struct sk_buff *skb)
1579 {
1580         __wsum csum;
1581 
1582         csum = csum_partial_copy_nocheck(dptr+offset, to, len, 0);
1583         skb->csum = csum_block_add(skb->csum, csum, odd);
1584         return 0;
1585 }
1586 
1587 /*
1588  *      Generic function to send a packet as reply to another packet.
1589  *      Used to send some TCP resets/acks so far.
1590  */
1591 void ip_send_unicast_reply(struct sock *sk, struct sk_buff *skb,
1592                            const struct ip_options *sopt,
1593                            __be32 daddr, __be32 saddr,
1594                            const struct ip_reply_arg *arg,
1595                            unsigned int len)
1596 {
1597         struct ip_options_data replyopts;
1598         struct ipcm_cookie ipc;
1599         struct flowi4 fl4;
1600         struct rtable *rt = skb_rtable(skb);
1601         struct net *net = sock_net(sk);
1602         struct sk_buff *nskb;
1603         int err;
1604         int oif;
1605 
1606         if (__ip_options_echo(&replyopts.opt.opt, skb, sopt))
1607                 return;
1608 
1609         ipc.addr = daddr;
1610         ipc.opt = NULL;
1611         ipc.tx_flags = 0;
1612         ipc.ttl = 0;
1613         ipc.tos = -1;
1614 
1615         if (replyopts.opt.opt.optlen) {
1616                 ipc.opt = &replyopts.opt;
1617 
1618                 if (replyopts.opt.opt.srr)
1619                         daddr = replyopts.opt.opt.faddr;
1620         }
1621 
1622         oif = arg->bound_dev_if;
1623         if (!oif && netif_index_is_l3_master(net, skb->skb_iif))
1624                 oif = skb->skb_iif;
1625 
1626         flowi4_init_output(&fl4, oif,
1627                            IP4_REPLY_MARK(net, skb->mark),
1628                            RT_TOS(arg->tos),
1629                            RT_SCOPE_UNIVERSE, ip_hdr(skb)->protocol,
1630                            ip_reply_arg_flowi_flags(arg),
1631                            daddr, saddr,
1632                            tcp_hdr(skb)->source, tcp_hdr(skb)->dest,
1633                            arg->uid);
1634         security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
1635         rt = ip_route_output_key(net, &fl4);
1636         if (IS_ERR(rt))
1637                 return;
1638 
1639         inet_sk(sk)->tos = arg->tos;
1640 
1641         sk->sk_priority = skb->priority;
1642         sk->sk_protocol = ip_hdr(skb)->protocol;
1643         sk->sk_bound_dev_if = arg->bound_dev_if;
1644         sk->sk_sndbuf = sysctl_wmem_default;
1645         sk->sk_mark = fl4.flowi4_mark;
1646         err = ip_append_data(sk, &fl4, ip_reply_glue_bits, arg->iov->iov_base,
1647                              len, 0, &ipc, &rt, MSG_DONTWAIT);
1648         if (unlikely(err)) {
1649                 ip_flush_pending_frames(sk);
1650                 goto out;
1651         }
1652 
1653         nskb = skb_peek(&sk->sk_write_queue);
1654         if (nskb) {
1655                 if (arg->csumoffset >= 0)
1656                         *((__sum16 *)skb_transport_header(nskb) +
1657                           arg->csumoffset) = csum_fold(csum_add(nskb->csum,
1658                                                                 arg->csum));
1659                 nskb->ip_summed = CHECKSUM_NONE;
1660                 ip_push_pending_frames(sk, &fl4);
1661         }
1662 out:
1663         ip_rt_put(rt);
1664 }
1665 
1666 void __init ip_init(void)
1667 {
1668         ip_rt_init();
1669         inet_initpeers();
1670 
1671 #if defined(CONFIG_IP_MULTICAST)
1672         igmp_mc_init();
1673 #endif
1674 }
1675 

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