81b2795a4c2053ddf1855b60dbec4357e9414845
[linux-2.6.git] / net / ipv4 / ip_output.c
1 /*
2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
3  *              operating system.  INET is implemented using the  BSD Socket
4  *              interface as the means of communication with the user level.
5  *
6  *              The Internet Protocol (IP) output module.
7  *
8  * Version:     $Id: ip_output.c,v 1.100 2002/02/01 22:01:03 davem Exp $
9  *
10  * Authors:     Ross Biro
11  *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
12  *              Donald Becker, <becker@super.org>
13  *              Alan Cox, <Alan.Cox@linux.org>
14  *              Richard Underwood
15  *              Stefan Becker, <stefanb@yello.ping.de>
16  *              Jorge Cwik, <jorge@laser.satlink.net>
17  *              Arnt Gulbrandsen, <agulbra@nvg.unit.no>
18  *              Hirokazu Takahashi, <taka@valinux.co.jp>
19  *
20  *      See ip_input.c for original log
21  *
22  *      Fixes:
23  *              Alan Cox        :       Missing nonblock feature in ip_build_xmit.
24  *              Mike Kilburn    :       htons() missing in ip_build_xmit.
25  *              Bradford Johnson:       Fix faulty handling of some frames when 
26  *                                      no route is found.
27  *              Alexander Demenshin:    Missing sk/skb free in ip_queue_xmit
28  *                                      (in case if packet not accepted by
29  *                                      output firewall rules)
30  *              Mike McLagan    :       Routing by source
31  *              Alexey Kuznetsov:       use new route cache
32  *              Andi Kleen:             Fix broken PMTU recovery and remove
33  *                                      some redundant tests.
34  *      Vitaly E. Lavrov        :       Transparent proxy revived after year coma.
35  *              Andi Kleen      :       Replace ip_reply with ip_send_reply.
36  *              Andi Kleen      :       Split fast and slow ip_build_xmit path 
37  *                                      for decreased register pressure on x86 
38  *                                      and more readibility. 
39  *              Marc Boucher    :       When call_out_firewall returns FW_QUEUE,
40  *                                      silently drop skb instead of failing with -EPERM.
41  *              Detlev Wengorz  :       Copy protocol for fragments.
42  *              Hirokazu Takahashi:     HW checksumming for outgoing UDP
43  *                                      datagrams.
44  *              Hirokazu Takahashi:     sendfile() on UDP works now.
45  */
46
47 #include <asm/uaccess.h>
48 #include <asm/system.h>
49 #include <linux/module.h>
50 #include <linux/types.h>
51 #include <linux/kernel.h>
52 #include <linux/sched.h>
53 #include <linux/mm.h>
54 #include <linux/string.h>
55 #include <linux/errno.h>
56
57 #include <linux/socket.h>
58 #include <linux/sockios.h>
59 #include <linux/in.h>
60 #include <linux/inet.h>
61 #include <linux/netdevice.h>
62 #include <linux/etherdevice.h>
63 #include <linux/proc_fs.h>
64 #include <linux/stat.h>
65 #include <linux/init.h>
66
67 #include <net/snmp.h>
68 #include <net/ip.h>
69 #include <net/protocol.h>
70 #include <net/route.h>
71 #include <net/xfrm.h>
72 #include <linux/skbuff.h>
73 #include <net/sock.h>
74 #include <net/arp.h>
75 #include <net/icmp.h>
76 #include <net/checksum.h>
77 #include <net/inetpeer.h>
78 #include <net/checksum.h>
79 #include <linux/igmp.h>
80 #include <linux/netfilter_ipv4.h>
81 #include <linux/netfilter_bridge.h>
82 #include <linux/mroute.h>
83 #include <linux/netlink.h>
84 #include <linux/tcp.h>
85
86 int sysctl_ip_default_ttl __read_mostly = IPDEFTTL;
87
88 /* Generate a checksum for an outgoing IP datagram. */
89 __inline__ void ip_send_check(struct iphdr *iph)
90 {
91         iph->check = 0;
92         iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
93 }
94
95 /* dev_loopback_xmit for use with netfilter. */
96 static int ip_dev_loopback_xmit(struct sk_buff *newskb)
97 {
98         newskb->mac.raw = newskb->data;
99         __skb_pull(newskb, newskb->nh.raw - newskb->data);
100         newskb->pkt_type = PACKET_LOOPBACK;
101         newskb->ip_summed = CHECKSUM_UNNECESSARY;
102         BUG_TRAP(newskb->dst);
103         netif_rx(newskb);
104         return 0;
105 }
106
107 static inline int ip_select_ttl(struct inet_sock *inet, struct dst_entry *dst)
108 {
109         int ttl = inet->uc_ttl;
110
111         if (ttl < 0)
112                 ttl = dst_metric(dst, RTAX_HOPLIMIT);
113         return ttl;
114 }
115
116 /* 
117  *              Add an ip header to a skbuff and send it out.
118  *
119  */
120 int ip_build_and_send_pkt(struct sk_buff *skb, struct sock *sk,
121                           u32 saddr, u32 daddr, struct ip_options *opt)
122 {
123         struct inet_sock *inet = inet_sk(sk);
124         struct rtable *rt = (struct rtable *)skb->dst;
125         struct iphdr *iph;
126
127         /* Build the IP header. */
128         if (opt)
129                 iph=(struct iphdr *)skb_push(skb,sizeof(struct iphdr) + opt->optlen);
130         else
131                 iph=(struct iphdr *)skb_push(skb,sizeof(struct iphdr));
132
133         iph->version  = 4;
134         iph->ihl      = 5;
135         iph->tos      = inet->tos;
136         if (ip_dont_fragment(sk, &rt->u.dst))
137                 iph->frag_off = htons(IP_DF);
138         else
139                 iph->frag_off = 0;
140         iph->ttl      = ip_select_ttl(inet, &rt->u.dst);
141         iph->daddr    = rt->rt_dst;
142         iph->saddr    = rt->rt_src;
143         iph->protocol = sk->sk_protocol;
144         iph->tot_len  = htons(skb->len);
145         ip_select_ident(iph, &rt->u.dst, sk);
146         skb->nh.iph   = iph;
147
148         if (opt && opt->optlen) {
149                 iph->ihl += opt->optlen>>2;
150                 ip_options_build(skb, opt, daddr, rt, 0);
151         }
152         ip_send_check(iph);
153
154         skb->priority = sk->sk_priority;
155
156         /* Send it out. */
157         return NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, skb, NULL, rt->u.dst.dev,
158                        dst_output);
159 }
160
161 EXPORT_SYMBOL_GPL(ip_build_and_send_pkt);
162
163 static inline int ip_finish_output2(struct sk_buff *skb)
164 {
165         struct dst_entry *dst = skb->dst;
166         struct hh_cache *hh = dst->hh;
167         struct net_device *dev = dst->dev;
168         int hh_len = LL_RESERVED_SPACE(dev);
169
170         /* Be paranoid, rather than too clever. */
171         if (unlikely(skb_headroom(skb) < hh_len && dev->hard_header)) {
172                 struct sk_buff *skb2;
173
174                 skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev));
175                 if (skb2 == NULL) {
176                         kfree_skb(skb);
177                         return -ENOMEM;
178                 }
179                 if (skb->sk)
180                         skb_set_owner_w(skb2, skb->sk);
181                 kfree_skb(skb);
182                 skb = skb2;
183         }
184
185         if (hh) {
186                 int hh_alen;
187
188                 read_lock_bh(&hh->hh_lock);
189                 hh_alen = HH_DATA_ALIGN(hh->hh_len);
190                 memcpy(skb->data - hh_alen, hh->hh_data, hh_alen);
191                 read_unlock_bh(&hh->hh_lock);
192                 skb_push(skb, hh->hh_len);
193                 return hh->hh_output(skb);
194         } else if (dst->neighbour)
195                 return dst->neighbour->output(skb);
196
197         if (net_ratelimit())
198                 printk(KERN_DEBUG "ip_finish_output2: No header cache and no neighbour!\n");
199         kfree_skb(skb);
200         return -EINVAL;
201 }
202
203 static inline int ip_finish_output(struct sk_buff *skb)
204 {
205 #if defined(CONFIG_NETFILTER) && defined(CONFIG_XFRM)
206         /* Policy lookup after SNAT yielded a new policy */
207         if (skb->dst->xfrm != NULL) {
208                 IPCB(skb)->flags |= IPSKB_REROUTED;
209                 return dst_output(skb);
210         }
211 #endif
212         if (skb->len > dst_mtu(skb->dst) && !skb_is_gso(skb))
213                 return ip_fragment(skb, ip_finish_output2);
214         else
215                 return ip_finish_output2(skb);
216 }
217
218 int ip_mc_output(struct sk_buff *skb)
219 {
220         struct sock *sk = skb->sk;
221         struct rtable *rt = (struct rtable*)skb->dst;
222         struct net_device *dev = rt->u.dst.dev;
223
224         /*
225          *      If the indicated interface is up and running, send the packet.
226          */
227         IP_INC_STATS(IPSTATS_MIB_OUTREQUESTS);
228
229         skb->dev = dev;
230         skb->protocol = htons(ETH_P_IP);
231
232         /*
233          *      Multicasts are looped back for other local users
234          */
235
236         if (rt->rt_flags&RTCF_MULTICAST) {
237                 if ((!sk || inet_sk(sk)->mc_loop)
238 #ifdef CONFIG_IP_MROUTE
239                 /* Small optimization: do not loopback not local frames,
240                    which returned after forwarding; they will be  dropped
241                    by ip_mr_input in any case.
242                    Note, that local frames are looped back to be delivered
243                    to local recipients.
244
245                    This check is duplicated in ip_mr_input at the moment.
246                  */
247                     && ((rt->rt_flags&RTCF_LOCAL) || !(IPCB(skb)->flags&IPSKB_FORWARDED))
248 #endif
249                 ) {
250                         struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
251                         if (newskb)
252                                 NF_HOOK(PF_INET, NF_IP_POST_ROUTING, newskb, NULL,
253                                         newskb->dev, 
254                                         ip_dev_loopback_xmit);
255                 }
256
257                 /* Multicasts with ttl 0 must not go beyond the host */
258
259                 if (skb->nh.iph->ttl == 0) {
260                         kfree_skb(skb);
261                         return 0;
262                 }
263         }
264
265         if (rt->rt_flags&RTCF_BROADCAST) {
266                 struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
267                 if (newskb)
268                         NF_HOOK(PF_INET, NF_IP_POST_ROUTING, newskb, NULL,
269                                 newskb->dev, ip_dev_loopback_xmit);
270         }
271
272         return NF_HOOK_COND(PF_INET, NF_IP_POST_ROUTING, skb, NULL, skb->dev,
273                             ip_finish_output,
274                             !(IPCB(skb)->flags & IPSKB_REROUTED));
275 }
276
277 int ip_output(struct sk_buff *skb)
278 {
279         struct net_device *dev = skb->dst->dev;
280
281         IP_INC_STATS(IPSTATS_MIB_OUTREQUESTS);
282
283         skb->dev = dev;
284         skb->protocol = htons(ETH_P_IP);
285
286         return NF_HOOK_COND(PF_INET, NF_IP_POST_ROUTING, skb, NULL, dev,
287                             ip_finish_output,
288                             !(IPCB(skb)->flags & IPSKB_REROUTED));
289 }
290
291 int ip_queue_xmit(struct sk_buff *skb, int ipfragok)
292 {
293         struct sock *sk = skb->sk;
294         struct inet_sock *inet = inet_sk(sk);
295         struct ip_options *opt = inet->opt;
296         struct rtable *rt;
297         struct iphdr *iph;
298
299         /* Skip all of this if the packet is already routed,
300          * f.e. by something like SCTP.
301          */
302         rt = (struct rtable *) skb->dst;
303         if (rt != NULL)
304                 goto packet_routed;
305
306         /* Make sure we can route this packet. */
307         rt = (struct rtable *)__sk_dst_check(sk, 0);
308         if (rt == NULL) {
309                 u32 daddr;
310
311                 /* Use correct destination address if we have options. */
312                 daddr = inet->daddr;
313                 if(opt && opt->srr)
314                         daddr = opt->faddr;
315
316                 {
317                         struct flowi fl = { .oif = sk->sk_bound_dev_if,
318                                             .nl_u = { .ip4_u =
319                                                       { .daddr = daddr,
320                                                         .saddr = inet->saddr,
321                                                         .tos = RT_CONN_FLAGS(sk) } },
322                                             .proto = sk->sk_protocol,
323                                             .uli_u = { .ports =
324                                                        { .sport = inet->sport,
325                                                          .dport = inet->dport } } };
326
327                         /* If this fails, retransmit mechanism of transport layer will
328                          * keep trying until route appears or the connection times
329                          * itself out.
330                          */
331                         security_sk_classify_flow(sk, &fl);
332                         if (ip_route_output_flow(&rt, &fl, sk, 0))
333                                 goto no_route;
334                 }
335                 sk_setup_caps(sk, &rt->u.dst);
336         }
337         skb->dst = dst_clone(&rt->u.dst);
338
339 packet_routed:
340         if (opt && opt->is_strictroute && rt->rt_dst != rt->rt_gateway)
341                 goto no_route;
342
343         /* OK, we know where to send it, allocate and build IP header. */
344         iph = (struct iphdr *) skb_push(skb, sizeof(struct iphdr) + (opt ? opt->optlen : 0));
345         *((__u16 *)iph) = htons((4 << 12) | (5 << 8) | (inet->tos & 0xff));
346         iph->tot_len = htons(skb->len);
347         if (ip_dont_fragment(sk, &rt->u.dst) && !ipfragok)
348                 iph->frag_off = htons(IP_DF);
349         else
350                 iph->frag_off = 0;
351         iph->ttl      = ip_select_ttl(inet, &rt->u.dst);
352         iph->protocol = sk->sk_protocol;
353         iph->saddr    = rt->rt_src;
354         iph->daddr    = rt->rt_dst;
355         skb->nh.iph   = iph;
356         /* Transport layer set skb->h.foo itself. */
357
358         if (opt && opt->optlen) {
359                 iph->ihl += opt->optlen >> 2;
360                 ip_options_build(skb, opt, inet->daddr, rt, 0);
361         }
362
363         ip_select_ident_more(iph, &rt->u.dst, sk,
364                              (skb_shinfo(skb)->gso_segs ?: 1) - 1);
365
366         /* Add an IP checksum. */
367         ip_send_check(iph);
368
369         skb->priority = sk->sk_priority;
370
371         return NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, skb, NULL, rt->u.dst.dev,
372                        dst_output);
373
374 no_route:
375         IP_INC_STATS(IPSTATS_MIB_OUTNOROUTES);
376         kfree_skb(skb);
377         return -EHOSTUNREACH;
378 }
379
380
381 static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
382 {
383         to->pkt_type = from->pkt_type;
384         to->priority = from->priority;
385         to->protocol = from->protocol;
386         dst_release(to->dst);
387         to->dst = dst_clone(from->dst);
388         to->dev = from->dev;
389
390         /* Copy the flags to each fragment. */
391         IPCB(to)->flags = IPCB(from)->flags;
392
393 #ifdef CONFIG_NET_SCHED
394         to->tc_index = from->tc_index;
395 #endif
396 #ifdef CONFIG_NETFILTER
397         to->nfmark = from->nfmark;
398         /* Connection association is same as pre-frag packet */
399         nf_conntrack_put(to->nfct);
400         to->nfct = from->nfct;
401         nf_conntrack_get(to->nfct);
402         to->nfctinfo = from->nfctinfo;
403 #if defined(CONFIG_IP_VS) || defined(CONFIG_IP_VS_MODULE)
404         to->ipvs_property = from->ipvs_property;
405 #endif
406 #ifdef CONFIG_BRIDGE_NETFILTER
407         nf_bridge_put(to->nf_bridge);
408         to->nf_bridge = from->nf_bridge;
409         nf_bridge_get(to->nf_bridge);
410 #endif
411 #endif
412         skb_copy_secmark(to, from);
413 }
414
415 /*
416  *      This IP datagram is too large to be sent in one piece.  Break it up into
417  *      smaller pieces (each of size equal to IP header plus
418  *      a block of the data of the original IP data part) that will yet fit in a
419  *      single device frame, and queue such a frame for sending.
420  */
421
422 int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff*))
423 {
424         struct iphdr *iph;
425         int raw = 0;
426         int ptr;
427         struct net_device *dev;
428         struct sk_buff *skb2;
429         unsigned int mtu, hlen, left, len, ll_rs;
430         int offset;
431         __be16 not_last_frag;
432         struct rtable *rt = (struct rtable*)skb->dst;
433         int err = 0;
434
435         dev = rt->u.dst.dev;
436
437         /*
438          *      Point into the IP datagram header.
439          */
440
441         iph = skb->nh.iph;
442
443         if (unlikely((iph->frag_off & htons(IP_DF)) && !skb->local_df)) {
444                 IP_INC_STATS(IPSTATS_MIB_FRAGFAILS);
445                 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
446                           htonl(dst_mtu(&rt->u.dst)));
447                 kfree_skb(skb);
448                 return -EMSGSIZE;
449         }
450
451         /*
452          *      Setup starting values.
453          */
454
455         hlen = iph->ihl * 4;
456         mtu = dst_mtu(&rt->u.dst) - hlen;       /* Size of data space */
457         IPCB(skb)->flags |= IPSKB_FRAG_COMPLETE;
458
459         /* When frag_list is given, use it. First, check its validity:
460          * some transformers could create wrong frag_list or break existing
461          * one, it is not prohibited. In this case fall back to copying.
462          *
463          * LATER: this step can be merged to real generation of fragments,
464          * we can switch to copy when see the first bad fragment.
465          */
466         if (skb_shinfo(skb)->frag_list) {
467                 struct sk_buff *frag;
468                 int first_len = skb_pagelen(skb);
469
470                 if (first_len - hlen > mtu ||
471                     ((first_len - hlen) & 7) ||
472                     (iph->frag_off & htons(IP_MF|IP_OFFSET)) ||
473                     skb_cloned(skb))
474                         goto slow_path;
475
476                 for (frag = skb_shinfo(skb)->frag_list; frag; frag = frag->next) {
477                         /* Correct geometry. */
478                         if (frag->len > mtu ||
479                             ((frag->len & 7) && frag->next) ||
480                             skb_headroom(frag) < hlen)
481                             goto slow_path;
482
483                         /* Partially cloned skb? */
484                         if (skb_shared(frag))
485                                 goto slow_path;
486
487                         BUG_ON(frag->sk);
488                         if (skb->sk) {
489                                 sock_hold(skb->sk);
490                                 frag->sk = skb->sk;
491                                 frag->destructor = sock_wfree;
492                                 skb->truesize -= frag->truesize;
493                         }
494                 }
495
496                 /* Everything is OK. Generate! */
497
498                 err = 0;
499                 offset = 0;
500                 frag = skb_shinfo(skb)->frag_list;
501                 skb_shinfo(skb)->frag_list = NULL;
502                 skb->data_len = first_len - skb_headlen(skb);
503                 skb->len = first_len;
504                 iph->tot_len = htons(first_len);
505                 iph->frag_off = htons(IP_MF);
506                 ip_send_check(iph);
507
508                 for (;;) {
509                         /* Prepare header of the next frame,
510                          * before previous one went down. */
511                         if (frag) {
512                                 frag->ip_summed = CHECKSUM_NONE;
513                                 frag->h.raw = frag->data;
514                                 frag->nh.raw = __skb_push(frag, hlen);
515                                 memcpy(frag->nh.raw, iph, hlen);
516                                 iph = frag->nh.iph;
517                                 iph->tot_len = htons(frag->len);
518                                 ip_copy_metadata(frag, skb);
519                                 if (offset == 0)
520                                         ip_options_fragment(frag);
521                                 offset += skb->len - hlen;
522                                 iph->frag_off = htons(offset>>3);
523                                 if (frag->next != NULL)
524                                         iph->frag_off |= htons(IP_MF);
525                                 /* Ready, complete checksum */
526                                 ip_send_check(iph);
527                         }
528
529                         err = output(skb);
530
531                         if (!err)
532                                 IP_INC_STATS(IPSTATS_MIB_FRAGCREATES);
533                         if (err || !frag)
534                                 break;
535
536                         skb = frag;
537                         frag = skb->next;
538                         skb->next = NULL;
539                 }
540
541                 if (err == 0) {
542                         IP_INC_STATS(IPSTATS_MIB_FRAGOKS);
543                         return 0;
544                 }
545
546                 while (frag) {
547                         skb = frag->next;
548                         kfree_skb(frag);
549                         frag = skb;
550                 }
551                 IP_INC_STATS(IPSTATS_MIB_FRAGFAILS);
552                 return err;
553         }
554
555 slow_path:
556         left = skb->len - hlen;         /* Space per frame */
557         ptr = raw + hlen;               /* Where to start from */
558
559 #ifdef CONFIG_BRIDGE_NETFILTER
560         /* for bridged IP traffic encapsulated inside f.e. a vlan header,
561          * we need to make room for the encapsulating header */
562         ll_rs = LL_RESERVED_SPACE_EXTRA(rt->u.dst.dev, nf_bridge_pad(skb));
563         mtu -= nf_bridge_pad(skb);
564 #else
565         ll_rs = LL_RESERVED_SPACE(rt->u.dst.dev);
566 #endif
567         /*
568          *      Fragment the datagram.
569          */
570
571         offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3;
572         not_last_frag = iph->frag_off & htons(IP_MF);
573
574         /*
575          *      Keep copying data until we run out.
576          */
577
578         while(left > 0) {
579                 len = left;
580                 /* IF: it doesn't fit, use 'mtu' - the data space left */
581                 if (len > mtu)
582                         len = mtu;
583                 /* IF: we are not sending upto and including the packet end
584                    then align the next start on an eight byte boundary */
585                 if (len < left) {
586                         len &= ~7;
587                 }
588                 /*
589                  *      Allocate buffer.
590                  */
591
592                 if ((skb2 = alloc_skb(len+hlen+ll_rs, GFP_ATOMIC)) == NULL) {
593                         NETDEBUG(KERN_INFO "IP: frag: no memory for new fragment!\n");
594                         err = -ENOMEM;
595                         goto fail;
596                 }
597
598                 /*
599                  *      Set up data on packet
600                  */
601
602                 ip_copy_metadata(skb2, skb);
603                 skb_reserve(skb2, ll_rs);
604                 skb_put(skb2, len + hlen);
605                 skb2->nh.raw = skb2->data;
606                 skb2->h.raw = skb2->data + hlen;
607
608                 /*
609                  *      Charge the memory for the fragment to any owner
610                  *      it might possess
611                  */
612
613                 if (skb->sk)
614                         skb_set_owner_w(skb2, skb->sk);
615
616                 /*
617                  *      Copy the packet header into the new buffer.
618                  */
619
620                 memcpy(skb2->nh.raw, skb->data, hlen);
621
622                 /*
623                  *      Copy a block of the IP datagram.
624                  */
625                 if (skb_copy_bits(skb, ptr, skb2->h.raw, len))
626                         BUG();
627                 left -= len;
628
629                 /*
630                  *      Fill in the new header fields.
631                  */
632                 iph = skb2->nh.iph;
633                 iph->frag_off = htons((offset >> 3));
634
635                 /* ANK: dirty, but effective trick. Upgrade options only if
636                  * the segment to be fragmented was THE FIRST (otherwise,
637                  * options are already fixed) and make it ONCE
638                  * on the initial skb, so that all the following fragments
639                  * will inherit fixed options.
640                  */
641                 if (offset == 0)
642                         ip_options_fragment(skb);
643
644                 /*
645                  *      Added AC : If we are fragmenting a fragment that's not the
646                  *                 last fragment then keep MF on each bit
647                  */
648                 if (left > 0 || not_last_frag)
649                         iph->frag_off |= htons(IP_MF);
650                 ptr += len;
651                 offset += len;
652
653                 /*
654                  *      Put this fragment into the sending queue.
655                  */
656                 iph->tot_len = htons(len + hlen);
657
658                 ip_send_check(iph);
659
660                 err = output(skb2);
661                 if (err)
662                         goto fail;
663
664                 IP_INC_STATS(IPSTATS_MIB_FRAGCREATES);
665         }
666         kfree_skb(skb);
667         IP_INC_STATS(IPSTATS_MIB_FRAGOKS);
668         return err;
669
670 fail:
671         kfree_skb(skb); 
672         IP_INC_STATS(IPSTATS_MIB_FRAGFAILS);
673         return err;
674 }
675
676 EXPORT_SYMBOL(ip_fragment);
677
678 int
679 ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
680 {
681         struct iovec *iov = from;
682
683         if (skb->ip_summed == CHECKSUM_PARTIAL) {
684                 if (memcpy_fromiovecend(to, iov, offset, len) < 0)
685                         return -EFAULT;
686         } else {
687                 unsigned int csum = 0;
688                 if (csum_partial_copy_fromiovecend(to, iov, offset, len, &csum) < 0)
689                         return -EFAULT;
690                 skb->csum = csum_block_add(skb->csum, csum, odd);
691         }
692         return 0;
693 }
694
695 static inline unsigned int
696 csum_page(struct page *page, int offset, int copy)
697 {
698         char *kaddr;
699         unsigned int csum;
700         kaddr = kmap(page);
701         csum = csum_partial(kaddr + offset, copy, 0);
702         kunmap(page);
703         return csum;
704 }
705
706 static inline int ip_ufo_append_data(struct sock *sk,
707                         int getfrag(void *from, char *to, int offset, int len,
708                                int odd, struct sk_buff *skb),
709                         void *from, int length, int hh_len, int fragheaderlen,
710                         int transhdrlen, int mtu,unsigned int flags)
711 {
712         struct sk_buff *skb;
713         int err;
714
715         /* There is support for UDP fragmentation offload by network
716          * device, so create one single skb packet containing complete
717          * udp datagram
718          */
719         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL) {
720                 skb = sock_alloc_send_skb(sk,
721                         hh_len + fragheaderlen + transhdrlen + 20,
722                         (flags & MSG_DONTWAIT), &err);
723
724                 if (skb == NULL)
725                         return err;
726
727                 /* reserve space for Hardware header */
728                 skb_reserve(skb, hh_len);
729
730                 /* create space for UDP/IP header */
731                 skb_put(skb,fragheaderlen + transhdrlen);
732
733                 /* initialize network header pointer */
734                 skb->nh.raw = skb->data;
735
736                 /* initialize protocol header pointer */
737                 skb->h.raw = skb->data + fragheaderlen;
738
739                 skb->ip_summed = CHECKSUM_PARTIAL;
740                 skb->csum = 0;
741                 sk->sk_sndmsg_off = 0;
742         }
743
744         err = skb_append_datato_frags(sk,skb, getfrag, from,
745                                (length - transhdrlen));
746         if (!err) {
747                 /* specify the length of each IP datagram fragment*/
748                 skb_shinfo(skb)->gso_size = mtu - fragheaderlen;
749                 skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
750                 __skb_queue_tail(&sk->sk_write_queue, skb);
751
752                 return 0;
753         }
754         /* There is not enough support do UFO ,
755          * so follow normal path
756          */
757         kfree_skb(skb);
758         return err;
759 }
760
761 /*
762  *      ip_append_data() and ip_append_page() can make one large IP datagram
763  *      from many pieces of data. Each pieces will be holded on the socket
764  *      until ip_push_pending_frames() is called. Each piece can be a page
765  *      or non-page data.
766  *      
767  *      Not only UDP, other transport protocols - e.g. raw sockets - can use
768  *      this interface potentially.
769  *
770  *      LATER: length must be adjusted by pad at tail, when it is required.
771  */
772 int ip_append_data(struct sock *sk,
773                    int getfrag(void *from, char *to, int offset, int len,
774                                int odd, struct sk_buff *skb),
775                    void *from, int length, int transhdrlen,
776                    struct ipcm_cookie *ipc, struct rtable *rt,
777                    unsigned int flags)
778 {
779         struct inet_sock *inet = inet_sk(sk);
780         struct sk_buff *skb;
781
782         struct ip_options *opt = NULL;
783         int hh_len;
784         int exthdrlen;
785         int mtu;
786         int copy;
787         int err;
788         int offset = 0;
789         unsigned int maxfraglen, fragheaderlen;
790         int csummode = CHECKSUM_NONE;
791
792         if (flags&MSG_PROBE)
793                 return 0;
794
795         if (skb_queue_empty(&sk->sk_write_queue)) {
796                 /*
797                  * setup for corking.
798                  */
799                 opt = ipc->opt;
800                 if (opt) {
801                         if (inet->cork.opt == NULL) {
802                                 inet->cork.opt = kmalloc(sizeof(struct ip_options) + 40, sk->sk_allocation);
803                                 if (unlikely(inet->cork.opt == NULL))
804                                         return -ENOBUFS;
805                         }
806                         memcpy(inet->cork.opt, opt, sizeof(struct ip_options)+opt->optlen);
807                         inet->cork.flags |= IPCORK_OPT;
808                         inet->cork.addr = ipc->addr;
809                 }
810                 dst_hold(&rt->u.dst);
811                 inet->cork.fragsize = mtu = dst_mtu(rt->u.dst.path);
812                 inet->cork.rt = rt;
813                 inet->cork.length = 0;
814                 sk->sk_sndmsg_page = NULL;
815                 sk->sk_sndmsg_off = 0;
816                 if ((exthdrlen = rt->u.dst.header_len) != 0) {
817                         length += exthdrlen;
818                         transhdrlen += exthdrlen;
819                 }
820         } else {
821                 rt = inet->cork.rt;
822                 if (inet->cork.flags & IPCORK_OPT)
823                         opt = inet->cork.opt;
824
825                 transhdrlen = 0;
826                 exthdrlen = 0;
827                 mtu = inet->cork.fragsize;
828         }
829         hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
830
831         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
832         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
833
834         if (inet->cork.length + length > 0xFFFF - fragheaderlen) {
835                 ip_local_error(sk, EMSGSIZE, rt->rt_dst, inet->dport, mtu-exthdrlen);
836                 return -EMSGSIZE;
837         }
838
839         /*
840          * transhdrlen > 0 means that this is the first fragment and we wish
841          * it won't be fragmented in the future.
842          */
843         if (transhdrlen &&
844             length + fragheaderlen <= mtu &&
845             rt->u.dst.dev->features & NETIF_F_ALL_CSUM &&
846             !exthdrlen)
847                 csummode = CHECKSUM_PARTIAL;
848
849         inet->cork.length += length;
850         if (((length > mtu) && (sk->sk_protocol == IPPROTO_UDP)) &&
851                         (rt->u.dst.dev->features & NETIF_F_UFO)) {
852
853                 err = ip_ufo_append_data(sk, getfrag, from, length, hh_len,
854                                          fragheaderlen, transhdrlen, mtu,
855                                          flags);
856                 if (err)
857                         goto error;
858                 return 0;
859         }
860
861         /* So, what's going on in the loop below?
862          *
863          * We use calculated fragment length to generate chained skb,
864          * each of segments is IP fragment ready for sending to network after
865          * adding appropriate IP header.
866          */
867
868         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
869                 goto alloc_new_skb;
870
871         while (length > 0) {
872                 /* Check if the remaining data fits into current packet. */
873                 copy = mtu - skb->len;
874                 if (copy < length)
875                         copy = maxfraglen - skb->len;
876                 if (copy <= 0) {
877                         char *data;
878                         unsigned int datalen;
879                         unsigned int fraglen;
880                         unsigned int fraggap;
881                         unsigned int alloclen;
882                         struct sk_buff *skb_prev;
883 alloc_new_skb:
884                         skb_prev = skb;
885                         if (skb_prev)
886                                 fraggap = skb_prev->len - maxfraglen;
887                         else
888                                 fraggap = 0;
889
890                         /*
891                          * If remaining data exceeds the mtu,
892                          * we know we need more fragment(s).
893                          */
894                         datalen = length + fraggap;
895                         if (datalen > mtu - fragheaderlen)
896                                 datalen = maxfraglen - fragheaderlen;
897                         fraglen = datalen + fragheaderlen;
898
899                         if ((flags & MSG_MORE) && 
900                             !(rt->u.dst.dev->features&NETIF_F_SG))
901                                 alloclen = mtu;
902                         else
903                                 alloclen = datalen + fragheaderlen;
904
905                         /* The last fragment gets additional space at tail.
906                          * Note, with MSG_MORE we overallocate on fragments,
907                          * because we have no idea what fragment will be
908                          * the last.
909                          */
910                         if (datalen == length + fraggap)
911                                 alloclen += rt->u.dst.trailer_len;
912
913                         if (transhdrlen) {
914                                 skb = sock_alloc_send_skb(sk, 
915                                                 alloclen + hh_len + 15,
916                                                 (flags & MSG_DONTWAIT), &err);
917                         } else {
918                                 skb = NULL;
919                                 if (atomic_read(&sk->sk_wmem_alloc) <=
920                                     2 * sk->sk_sndbuf)
921                                         skb = sock_wmalloc(sk, 
922                                                            alloclen + hh_len + 15, 1,
923                                                            sk->sk_allocation);
924                                 if (unlikely(skb == NULL))
925                                         err = -ENOBUFS;
926                         }
927                         if (skb == NULL)
928                                 goto error;
929
930                         /*
931                          *      Fill in the control structures
932                          */
933                         skb->ip_summed = csummode;
934                         skb->csum = 0;
935                         skb_reserve(skb, hh_len);
936
937                         /*
938                          *      Find where to start putting bytes.
939                          */
940                         data = skb_put(skb, fraglen);
941                         skb->nh.raw = data + exthdrlen;
942                         data += fragheaderlen;
943                         skb->h.raw = data + exthdrlen;
944
945                         if (fraggap) {
946                                 skb->csum = skb_copy_and_csum_bits(
947                                         skb_prev, maxfraglen,
948                                         data + transhdrlen, fraggap, 0);
949                                 skb_prev->csum = csum_sub(skb_prev->csum,
950                                                           skb->csum);
951                                 data += fraggap;
952                                 pskb_trim_unique(skb_prev, maxfraglen);
953                         }
954
955                         copy = datalen - transhdrlen - fraggap;
956                         if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
957                                 err = -EFAULT;
958                                 kfree_skb(skb);
959                                 goto error;
960                         }
961
962                         offset += copy;
963                         length -= datalen - fraggap;
964                         transhdrlen = 0;
965                         exthdrlen = 0;
966                         csummode = CHECKSUM_NONE;
967
968                         /*
969                          * Put the packet on the pending queue.
970                          */
971                         __skb_queue_tail(&sk->sk_write_queue, skb);
972                         continue;
973                 }
974
975                 if (copy > length)
976                         copy = length;
977
978                 if (!(rt->u.dst.dev->features&NETIF_F_SG)) {
979                         unsigned int off;
980
981                         off = skb->len;
982                         if (getfrag(from, skb_put(skb, copy), 
983                                         offset, copy, off, skb) < 0) {
984                                 __skb_trim(skb, off);
985                                 err = -EFAULT;
986                                 goto error;
987                         }
988                 } else {
989                         int i = skb_shinfo(skb)->nr_frags;
990                         skb_frag_t *frag = &skb_shinfo(skb)->frags[i-1];
991                         struct page *page = sk->sk_sndmsg_page;
992                         int off = sk->sk_sndmsg_off;
993                         unsigned int left;
994
995                         if (page && (left = PAGE_SIZE - off) > 0) {
996                                 if (copy >= left)
997                                         copy = left;
998                                 if (page != frag->page) {
999                                         if (i == MAX_SKB_FRAGS) {
1000                                                 err = -EMSGSIZE;
1001                                                 goto error;
1002                                         }
1003                                         get_page(page);
1004                                         skb_fill_page_desc(skb, i, page, sk->sk_sndmsg_off, 0);
1005                                         frag = &skb_shinfo(skb)->frags[i];
1006                                 }
1007                         } else if (i < MAX_SKB_FRAGS) {
1008                                 if (copy > PAGE_SIZE)
1009                                         copy = PAGE_SIZE;
1010                                 page = alloc_pages(sk->sk_allocation, 0);
1011                                 if (page == NULL)  {
1012                                         err = -ENOMEM;
1013                                         goto error;
1014                                 }
1015                                 sk->sk_sndmsg_page = page;
1016                                 sk->sk_sndmsg_off = 0;
1017
1018                                 skb_fill_page_desc(skb, i, page, 0, 0);
1019                                 frag = &skb_shinfo(skb)->frags[i];
1020                                 skb->truesize += PAGE_SIZE;
1021                                 atomic_add(PAGE_SIZE, &sk->sk_wmem_alloc);
1022                         } else {
1023                                 err = -EMSGSIZE;
1024                                 goto error;
1025                         }
1026                         if (getfrag(from, page_address(frag->page)+frag->page_offset+frag->size, offset, copy, skb->len, skb) < 0) {
1027                                 err = -EFAULT;
1028                                 goto error;
1029                         }
1030                         sk->sk_sndmsg_off += copy;
1031                         frag->size += copy;
1032                         skb->len += copy;
1033                         skb->data_len += copy;
1034                 }
1035                 offset += copy;
1036                 length -= copy;
1037         }
1038
1039         return 0;
1040
1041 error:
1042         inet->cork.length -= length;
1043         IP_INC_STATS(IPSTATS_MIB_OUTDISCARDS);
1044         return err; 
1045 }
1046
1047 ssize_t ip_append_page(struct sock *sk, struct page *page,
1048                        int offset, size_t size, int flags)
1049 {
1050         struct inet_sock *inet = inet_sk(sk);
1051         struct sk_buff *skb;
1052         struct rtable *rt;
1053         struct ip_options *opt = NULL;
1054         int hh_len;
1055         int mtu;
1056         int len;
1057         int err;
1058         unsigned int maxfraglen, fragheaderlen, fraggap;
1059
1060         if (inet->hdrincl)
1061                 return -EPERM;
1062
1063         if (flags&MSG_PROBE)
1064                 return 0;
1065
1066         if (skb_queue_empty(&sk->sk_write_queue))
1067                 return -EINVAL;
1068
1069         rt = inet->cork.rt;
1070         if (inet->cork.flags & IPCORK_OPT)
1071                 opt = inet->cork.opt;
1072
1073         if (!(rt->u.dst.dev->features&NETIF_F_SG))
1074                 return -EOPNOTSUPP;
1075
1076         hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
1077         mtu = inet->cork.fragsize;
1078
1079         fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
1080         maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
1081
1082         if (inet->cork.length + size > 0xFFFF - fragheaderlen) {
1083                 ip_local_error(sk, EMSGSIZE, rt->rt_dst, inet->dport, mtu);
1084                 return -EMSGSIZE;
1085         }
1086
1087         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
1088                 return -EINVAL;
1089
1090         inet->cork.length += size;
1091         if ((sk->sk_protocol == IPPROTO_UDP) &&
1092             (rt->u.dst.dev->features & NETIF_F_UFO)) {
1093                 skb_shinfo(skb)->gso_size = mtu - fragheaderlen;
1094                 skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
1095         }
1096
1097
1098         while (size > 0) {
1099                 int i;
1100
1101                 if (skb_is_gso(skb))
1102                         len = size;
1103                 else {
1104
1105                         /* Check if the remaining data fits into current packet. */
1106                         len = mtu - skb->len;
1107                         if (len < size)
1108                                 len = maxfraglen - skb->len;
1109                 }
1110                 if (len <= 0) {
1111                         struct sk_buff *skb_prev;
1112                         char *data;
1113                         struct iphdr *iph;
1114                         int alloclen;
1115
1116                         skb_prev = skb;
1117                         fraggap = skb_prev->len - maxfraglen;
1118
1119                         alloclen = fragheaderlen + hh_len + fraggap + 15;
1120                         skb = sock_wmalloc(sk, alloclen, 1, sk->sk_allocation);
1121                         if (unlikely(!skb)) {
1122                                 err = -ENOBUFS;
1123                                 goto error;
1124                         }
1125
1126                         /*
1127                          *      Fill in the control structures
1128                          */
1129                         skb->ip_summed = CHECKSUM_NONE;
1130                         skb->csum = 0;
1131                         skb_reserve(skb, hh_len);
1132
1133                         /*
1134                          *      Find where to start putting bytes.
1135                          */
1136                         data = skb_put(skb, fragheaderlen + fraggap);
1137                         skb->nh.iph = iph = (struct iphdr *)data;
1138                         data += fragheaderlen;
1139                         skb->h.raw = data;
1140
1141                         if (fraggap) {
1142                                 skb->csum = skb_copy_and_csum_bits(
1143                                         skb_prev, maxfraglen,
1144                                         data, fraggap, 0);
1145                                 skb_prev->csum = csum_sub(skb_prev->csum,
1146                                                           skb->csum);
1147                                 pskb_trim_unique(skb_prev, maxfraglen);
1148                         }
1149
1150                         /*
1151                          * Put the packet on the pending queue.
1152                          */
1153                         __skb_queue_tail(&sk->sk_write_queue, skb);
1154                         continue;
1155                 }
1156
1157                 i = skb_shinfo(skb)->nr_frags;
1158                 if (len > size)
1159                         len = size;
1160                 if (skb_can_coalesce(skb, i, page, offset)) {
1161                         skb_shinfo(skb)->frags[i-1].size += len;
1162                 } else if (i < MAX_SKB_FRAGS) {
1163                         get_page(page);
1164                         skb_fill_page_desc(skb, i, page, offset, len);
1165                 } else {
1166                         err = -EMSGSIZE;
1167                         goto error;
1168                 }
1169
1170                 if (skb->ip_summed == CHECKSUM_NONE) {
1171                         unsigned int csum;
1172                         csum = csum_page(page, offset, len);
1173                         skb->csum = csum_block_add(skb->csum, csum, skb->len);
1174                 }
1175
1176                 skb->len += len;
1177                 skb->data_len += len;
1178                 offset += len;
1179                 size -= len;
1180         }
1181         return 0;
1182
1183 error:
1184         inet->cork.length -= size;
1185         IP_INC_STATS(IPSTATS_MIB_OUTDISCARDS);
1186         return err;
1187 }
1188
1189 /*
1190  *      Combined all pending IP fragments on the socket as one IP datagram
1191  *      and push them out.
1192  */
1193 int ip_push_pending_frames(struct sock *sk)
1194 {
1195         struct sk_buff *skb, *tmp_skb;
1196         struct sk_buff **tail_skb;
1197         struct inet_sock *inet = inet_sk(sk);
1198         struct ip_options *opt = NULL;
1199         struct rtable *rt = inet->cork.rt;
1200         struct iphdr *iph;
1201         __be16 df = 0;
1202         __u8 ttl;
1203         int err = 0;
1204
1205         if ((skb = __skb_dequeue(&sk->sk_write_queue)) == NULL)
1206                 goto out;
1207         tail_skb = &(skb_shinfo(skb)->frag_list);
1208
1209         /* move skb->data to ip header from ext header */
1210         if (skb->data < skb->nh.raw)
1211                 __skb_pull(skb, skb->nh.raw - skb->data);
1212         while ((tmp_skb = __skb_dequeue(&sk->sk_write_queue)) != NULL) {
1213                 __skb_pull(tmp_skb, skb->h.raw - skb->nh.raw);
1214                 *tail_skb = tmp_skb;
1215                 tail_skb = &(tmp_skb->next);
1216                 skb->len += tmp_skb->len;
1217                 skb->data_len += tmp_skb->len;
1218                 skb->truesize += tmp_skb->truesize;
1219                 __sock_put(tmp_skb->sk);
1220                 tmp_skb->destructor = NULL;
1221                 tmp_skb->sk = NULL;
1222         }
1223
1224         /* Unless user demanded real pmtu discovery (IP_PMTUDISC_DO), we allow
1225          * to fragment the frame generated here. No matter, what transforms
1226          * how transforms change size of the packet, it will come out.
1227          */
1228         if (inet->pmtudisc != IP_PMTUDISC_DO)
1229                 skb->local_df = 1;
1230
1231         /* DF bit is set when we want to see DF on outgoing frames.
1232          * If local_df is set too, we still allow to fragment this frame
1233          * locally. */
1234         if (inet->pmtudisc == IP_PMTUDISC_DO ||
1235             (skb->len <= dst_mtu(&rt->u.dst) &&
1236              ip_dont_fragment(sk, &rt->u.dst)))
1237                 df = htons(IP_DF);
1238
1239         if (inet->cork.flags & IPCORK_OPT)
1240                 opt = inet->cork.opt;
1241
1242         if (rt->rt_type == RTN_MULTICAST)
1243                 ttl = inet->mc_ttl;
1244         else
1245                 ttl = ip_select_ttl(inet, &rt->u.dst);
1246
1247         iph = (struct iphdr *)skb->data;
1248         iph->version = 4;
1249         iph->ihl = 5;
1250         if (opt) {
1251                 iph->ihl += opt->optlen>>2;
1252                 ip_options_build(skb, opt, inet->cork.addr, rt, 0);
1253         }
1254         iph->tos = inet->tos;
1255         iph->tot_len = htons(skb->len);
1256         iph->frag_off = df;
1257         ip_select_ident(iph, &rt->u.dst, sk);
1258         iph->ttl = ttl;
1259         iph->protocol = sk->sk_protocol;
1260         iph->saddr = rt->rt_src;
1261         iph->daddr = rt->rt_dst;
1262         ip_send_check(iph);
1263
1264         skb->priority = sk->sk_priority;
1265         skb->dst = dst_clone(&rt->u.dst);
1266
1267         /* Netfilter gets whole the not fragmented skb. */
1268         err = NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, skb, NULL, 
1269                       skb->dst->dev, dst_output);
1270         if (err) {
1271                 if (err > 0)
1272                         err = inet->recverr ? net_xmit_errno(err) : 0;
1273                 if (err)
1274                         goto error;
1275         }
1276
1277 out:
1278         inet->cork.flags &= ~IPCORK_OPT;
1279         kfree(inet->cork.opt);
1280         inet->cork.opt = NULL;
1281         if (inet->cork.rt) {
1282                 ip_rt_put(inet->cork.rt);
1283                 inet->cork.rt = NULL;
1284         }
1285         return err;
1286
1287 error:
1288         IP_INC_STATS(IPSTATS_MIB_OUTDISCARDS);
1289         goto out;
1290 }
1291
1292 /*
1293  *      Throw away all pending data on the socket.
1294  */
1295 void ip_flush_pending_frames(struct sock *sk)
1296 {
1297         struct inet_sock *inet = inet_sk(sk);
1298         struct sk_buff *skb;
1299
1300         while ((skb = __skb_dequeue_tail(&sk->sk_write_queue)) != NULL)
1301                 kfree_skb(skb);
1302
1303         inet->cork.flags &= ~IPCORK_OPT;
1304         kfree(inet->cork.opt);
1305         inet->cork.opt = NULL;
1306         if (inet->cork.rt) {
1307                 ip_rt_put(inet->cork.rt);
1308                 inet->cork.rt = NULL;
1309         }
1310 }
1311
1312
1313 /*
1314  *      Fetch data from kernel space and fill in checksum if needed.
1315  */
1316 static int ip_reply_glue_bits(void *dptr, char *to, int offset, 
1317                               int len, int odd, struct sk_buff *skb)
1318 {
1319         unsigned int csum;
1320
1321         csum = csum_partial_copy_nocheck(dptr+offset, to, len, 0);
1322         skb->csum = csum_block_add(skb->csum, csum, odd);
1323         return 0;  
1324 }
1325
1326 /* 
1327  *      Generic function to send a packet as reply to another packet.
1328  *      Used to send TCP resets so far. ICMP should use this function too.
1329  *
1330  *      Should run single threaded per socket because it uses the sock 
1331  *      structure to pass arguments.
1332  *
1333  *      LATER: switch from ip_build_xmit to ip_append_*
1334  */
1335 void ip_send_reply(struct sock *sk, struct sk_buff *skb, struct ip_reply_arg *arg,
1336                    unsigned int len)
1337 {
1338         struct inet_sock *inet = inet_sk(sk);
1339         struct {
1340                 struct ip_options       opt;
1341                 char                    data[40];
1342         } replyopts;
1343         struct ipcm_cookie ipc;
1344         u32 daddr;
1345         struct rtable *rt = (struct rtable*)skb->dst;
1346
1347         if (ip_options_echo(&replyopts.opt, skb))
1348                 return;
1349
1350         daddr = ipc.addr = rt->rt_src;
1351         ipc.opt = NULL;
1352
1353         if (replyopts.opt.optlen) {
1354                 ipc.opt = &replyopts.opt;
1355
1356                 if (ipc.opt->srr)
1357                         daddr = replyopts.opt.faddr;
1358         }
1359
1360         {
1361                 struct flowi fl = { .nl_u = { .ip4_u =
1362                                               { .daddr = daddr,
1363                                                 .saddr = rt->rt_spec_dst,
1364                                                 .tos = RT_TOS(skb->nh.iph->tos) } },
1365                                     /* Not quite clean, but right. */
1366                                     .uli_u = { .ports =
1367                                                { .sport = skb->h.th->dest,
1368                                                  .dport = skb->h.th->source } },
1369                                     .proto = sk->sk_protocol };
1370                 security_skb_classify_flow(skb, &fl);
1371                 if (ip_route_output_key(&rt, &fl))
1372                         return;
1373         }
1374
1375         /* And let IP do all the hard work.
1376
1377            This chunk is not reenterable, hence spinlock.
1378            Note that it uses the fact, that this function is called
1379            with locally disabled BH and that sk cannot be already spinlocked.
1380          */
1381         bh_lock_sock(sk);
1382         inet->tos = skb->nh.iph->tos;
1383         sk->sk_priority = skb->priority;
1384         sk->sk_protocol = skb->nh.iph->protocol;
1385         ip_append_data(sk, ip_reply_glue_bits, arg->iov->iov_base, len, 0,
1386                        &ipc, rt, MSG_DONTWAIT);
1387         if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {
1388                 if (arg->csumoffset >= 0)
1389                         *((u16 *)skb->h.raw + arg->csumoffset) = csum_fold(csum_add(skb->csum, arg->csum));
1390                 skb->ip_summed = CHECKSUM_NONE;
1391                 ip_push_pending_frames(sk);
1392         }
1393
1394         bh_unlock_sock(sk);
1395
1396         ip_rt_put(rt);
1397 }
1398
1399 void __init ip_init(void)
1400 {
1401         ip_rt_init();
1402         inet_initpeers();
1403
1404 #if defined(CONFIG_IP_MULTICAST) && defined(CONFIG_PROC_FS)
1405         igmp_mc_proc_init();
1406 #endif
1407 }
1408
1409 EXPORT_SYMBOL(ip_generic_getfrag);
1410 EXPORT_SYMBOL(ip_queue_xmit);
1411 EXPORT_SYMBOL(ip_send_check);