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, <bir7@leland.Stanford.Edu>
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 #include <linux/config.h>
57
58 #include <linux/socket.h>
59 #include <linux/sockios.h>
60 #include <linux/in.h>
61 #include <linux/inet.h>
62 #include <linux/netdevice.h>
63 #include <linux/etherdevice.h>
64 #include <linux/proc_fs.h>
65 #include <linux/stat.h>
66 #include <linux/init.h>
67
68 #include <net/snmp.h>
69 #include <net/ip.h>
70 #include <net/protocol.h>
71 #include <net/route.h>
72 #include <net/tcp.h>
73 #include <net/udp.h>
74 #include <linux/skbuff.h>
75 #include <net/sock.h>
76 #include <net/arp.h>
77 #include <net/icmp.h>
78 #include <net/raw.h>
79 #include <net/checksum.h>
80 #include <net/inetpeer.h>
81 #include <net/checksum.h>
82 #include <linux/igmp.h>
83 #include <linux/netfilter_ipv4.h>
84 #include <linux/netfilter_bridge.h>
85 #include <linux/mroute.h>
86 #include <linux/netlink.h>
87
88 /*
89 * Shall we try to damage output packets if routing dev changes?
90 */
91
92 int sysctl_ip_dynaddr;
93 int sysctl_ip_default_ttl = IPDEFTTL;
94
95 /* Generate a checksum for an outgoing IP datagram. */
96 __inline__ void ip_send_check(struct iphdr *iph)
97 {
98 iph->check = 0;
99 iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
100 }
101
102 /* dev_loopback_xmit for use with netfilter. */
103 static int ip_dev_loopback_xmit(struct sk_buff *newskb)
104 {
105 newskb->mac.raw = newskb->data;
106 __skb_pull(newskb, newskb->nh.raw - newskb->data);
107 newskb->pkt_type = PACKET_LOOPBACK;
108 newskb->ip_summed = CHECKSUM_UNNECESSARY;
109 BUG_TRAP(newskb->dst);
110
111 #ifdef CONFIG_NETFILTER_DEBUG
112 nf_debug_ip_loopback_xmit(newskb);
113 #endif
114 netif_rx(newskb);
115 return 0;
116 }
117
118 static inline int ip_select_ttl(struct inet_sock *inet, struct dst_entry *dst)
119 {
120 int ttl = inet->uc_ttl;
121
122 if (ttl < 0)
123 ttl = dst_metric(dst, RTAX_HOPLIMIT);
124 return ttl;
125 }
126
127 /*
128 * Add an ip header to a skbuff and send it out.
129 *
130 */
131 int ip_build_and_send_pkt(struct sk_buff *skb, struct sock *sk,
132 u32 saddr, u32 daddr, struct ip_options *opt)
133 {
134 struct inet_sock *inet = inet_sk(sk);
135 struct rtable *rt = (struct rtable *)skb->dst;
136 struct iphdr *iph;
137
138 /* Build the IP header. */
139 if (opt)
140 iph=(struct iphdr *)skb_push(skb,sizeof(struct iphdr) + opt->optlen);
141 else
142 iph=(struct iphdr *)skb_push(skb,sizeof(struct iphdr));
143
144 iph->version = 4;
145 iph->ihl = 5;
146 iph->tos = inet->tos;
147 if (ip_dont_fragment(sk, &rt->u.dst))
148 iph->frag_off = htons(IP_DF);
149 else
150 iph->frag_off = 0;
151 iph->ttl = ip_select_ttl(inet, &rt->u.dst);
152 iph->daddr = rt->rt_dst;
153 iph->saddr = rt->rt_src;
154 iph->protocol = sk->sk_protocol;
155 iph->tot_len = htons(skb->len);
156 ip_select_ident(iph, &rt->u.dst, sk);
157 skb->nh.iph = iph;
158
159 if (opt && opt->optlen) {
160 iph->ihl += opt->optlen>>2;
161 ip_options_build(skb, opt, daddr, rt, 0);
162 }
163 ip_send_check(iph);
164
165 skb->priority = sk->sk_priority;
166
167 /* Send it out. */
168 return NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, skb, NULL, rt->u.dst.dev,
169 dst_output);
170 }
171
172 static inline int ip_finish_output2(struct sk_buff *skb)
173 {
174 struct dst_entry *dst = skb->dst;
175 struct hh_cache *hh = dst->hh;
176 struct net_device *dev = dst->dev;
177 int hh_len = LL_RESERVED_SPACE(dev);
178
179 /* Be paranoid, rather than too clever. */
180 if (unlikely(skb_headroom(skb) < hh_len && dev->hard_header)) {
181 struct sk_buff *skb2;
182
183 skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev));
184 if (skb2 == NULL) {
185 kfree_skb(skb);
186 return -ENOMEM;
187 }
188 if (skb->sk)
189 skb_set_owner_w(skb2, skb->sk);
190 kfree_skb(skb);
191 skb = skb2;
192 }
193
194 #ifdef CONFIG_NETFILTER_DEBUG
195 nf_debug_ip_finish_output2(skb);
196 #endif /*CONFIG_NETFILTER_DEBUG*/
197
198 if (hh) {
199 int hh_alen;
200
201 read_lock_bh(&hh->hh_lock);
202 hh_alen = HH_DATA_ALIGN(hh->hh_len);
203 memcpy(skb->data - hh_alen, hh->hh_data, hh_alen);
204 read_unlock_bh(&hh->hh_lock);
205 skb_push(skb, hh->hh_len);
206 return hh->hh_output(skb);
207 } else if (dst->neighbour)
208 return dst->neighbour->output(skb);
209
210 if (net_ratelimit())
211 printk(KERN_DEBUG "ip_finish_output2: No header cache and no neighbour!\n");
212 kfree_skb(skb);
213 return -EINVAL;
214 }
215
216 int ip_finish_output(struct sk_buff *skb)
217 {
218 struct net_device *dev = skb->dst->dev;
219
220 skb->dev = dev;
221 skb->protocol = htons(ETH_P_IP);
222
223 return NF_HOOK(PF_INET, NF_IP_POST_ROUTING, skb, NULL, dev,
224 ip_finish_output2);
225 }
226
227 int ip_mc_output(struct sk_buff *skb)
228 {
229 struct sock *sk = skb->sk;
230 struct rtable *rt = (struct rtable*)skb->dst;
231 struct net_device *dev = rt->u.dst.dev;
232
233 /*
234 * If the indicated interface is up and running, send the packet.
235 */
236 IP_INC_STATS(IPSTATS_MIB_OUTREQUESTS);
237
238 skb->dev = dev;
239 skb->protocol = htons(ETH_P_IP);
240
241 /*
242 * Multicasts are looped back for other local users
243 */
244
245 if (rt->rt_flags&RTCF_MULTICAST) {
246 if ((!sk || inet_sk(sk)->mc_loop)
247 #ifdef CONFIG_IP_MROUTE
248 /* Small optimization: do not loopback not local frames,
249 which returned after forwarding; they will be dropped
250 by ip_mr_input in any case.
251 Note, that local frames are looped back to be delivered
252 to local recipients.
253
254 This check is duplicated in ip_mr_input at the moment.
255 */
256 && ((rt->rt_flags&RTCF_LOCAL) || !(IPCB(skb)->flags&IPSKB_FORWARDED))
257 #endif
258 ) {
259 struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
260 if (newskb)
261 NF_HOOK(PF_INET, NF_IP_POST_ROUTING, newskb, NULL,
262 newskb->dev,
263 ip_dev_loopback_xmit);
264 }
265
266 /* Multicasts with ttl 0 must not go beyond the host */
267
268 if (skb->nh.iph->ttl == 0) {
269 kfree_skb(skb);
270 return 0;
271 }
272 }
273
274 if (rt->rt_flags&RTCF_BROADCAST) {
275 struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
276 if (newskb)
277 NF_HOOK(PF_INET, NF_IP_POST_ROUTING, newskb, NULL,
278 newskb->dev, ip_dev_loopback_xmit);
279 }
280
281 if (skb->len > dst_pmtu(&rt->u.dst))
282 return ip_fragment(skb, ip_finish_output);
283 else
284 return ip_finish_output(skb);
285 }
286
287 int ip_output(struct sk_buff *skb)
288 {
289 IP_INC_STATS(IPSTATS_MIB_OUTREQUESTS);
290
291 if (skb->len > dst_pmtu(skb->dst) && !skb_shinfo(skb)->tso_size)
292 return ip_fragment(skb, ip_finish_output);
293 else
294 return ip_finish_output(skb);
295 }
296
297 int ip_queue_xmit(struct sk_buff *skb, int ipfragok)
298 {
299 struct sock *sk = skb->sk;
300 struct inet_sock *inet = inet_sk(sk);
301 struct ip_options *opt = inet->opt;
302 struct rtable *rt;
303 struct iphdr *iph;
304
305 /* Skip all of this if the packet is already routed,
306 * f.e. by something like SCTP.
307 */
308 rt = (struct rtable *) skb->dst;
309 if (rt != NULL)
310 goto packet_routed;
311
312 /* Make sure we can route this packet. */
313 rt = (struct rtable *)__sk_dst_check(sk, 0);
314 if (rt == NULL) {
315 u32 daddr;
316
317 /* Use correct destination address if we have options. */
318 daddr = inet->daddr;
319 if(opt && opt->srr)
320 daddr = opt->faddr;
321
322 {
323 struct flowi fl = { .oif = sk->sk_bound_dev_if,
324 .nl_u = { .ip4_u =
325 { .daddr = daddr,
326 .saddr = inet->saddr,
327 .tos = RT_CONN_FLAGS(sk) } },
328 .proto = sk->sk_protocol,
329 .uli_u = { .ports =
330 { .sport = inet->sport,
331 .dport = inet->dport } } };
332
333 /* If this fails, retransmit mechanism of transport layer will
334 * keep trying until route appears or the connection times
335 * itself out.
336 */
337 if (ip_route_output_flow(&rt, &fl, sk, 0))
338 goto no_route;
339 }
340 __sk_dst_set(sk, &rt->u.dst);
341 tcp_v4_setup_caps(sk, &rt->u.dst);
342 }
343 skb->dst = dst_clone(&rt->u.dst);
344
345 packet_routed:
346 if (opt && opt->is_strictroute && rt->rt_dst != rt->rt_gateway)
347 goto no_route;
348
349 /* OK, we know where to send it, allocate and build IP header. */
350 iph = (struct iphdr *) skb_push(skb, sizeof(struct iphdr) + (opt ? opt->optlen : 0));
351 *((__u16 *)iph) = htons((4 << 12) | (5 << 8) | (inet->tos & 0xff));
352 iph->tot_len = htons(skb->len);
353 if (ip_dont_fragment(sk, &rt->u.dst) && !ipfragok)
354 iph->frag_off = htons(IP_DF);
355 else
356 iph->frag_off = 0;
357 iph->ttl = ip_select_ttl(inet, &rt->u.dst);
358 iph->protocol = sk->sk_protocol;
359 iph->saddr = rt->rt_src;
360 iph->daddr = rt->rt_dst;
361 skb->nh.iph = iph;
362 /* Transport layer set skb->h.foo itself. */
363
364 if (opt && opt->optlen) {
365 iph->ihl += opt->optlen >> 2;
366 ip_options_build(skb, opt, inet->daddr, rt, 0);
367 }
368
369 ip_select_ident_more(iph, &rt->u.dst, sk, skb_shinfo(skb)->tso_segs);
370
371 /* Add an IP checksum. */
372 ip_send_check(iph);
373
374 skb->priority = sk->sk_priority;
375
376 return NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, skb, NULL, rt->u.dst.dev,
377 dst_output);
378
379 no_route:
380 IP_INC_STATS(IPSTATS_MIB_OUTNOROUTES);
381 kfree_skb(skb);
382 return -EHOSTUNREACH;
383 }
384
385
386 static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
387 {
388 to->pkt_type = from->pkt_type;
389 to->priority = from->priority;
390 to->protocol = from->protocol;
391 to->security = from->security;
392 dst_release(to->dst);
393 to->dst = dst_clone(from->dst);
394 to->dev = from->dev;
395
396 /* Copy the flags to each fragment. */
397 IPCB(to)->flags = IPCB(from)->flags;
398
399 #ifdef CONFIG_NET_SCHED
400 to->tc_index = from->tc_index;
401 #endif
402 #ifdef CONFIG_NETFILTER
403 to->nfmark = from->nfmark;
404 to->nfcache = from->nfcache;
405 /* Connection association is same as pre-frag packet */
406 nf_conntrack_put(to->nfct);
407 to->nfct = from->nfct;
408 nf_conntrack_get(to->nfct);
409 to->nfctinfo = from->nfctinfo;
410 #ifdef CONFIG_BRIDGE_NETFILTER
411 nf_bridge_put(to->nf_bridge);
412 to->nf_bridge = from->nf_bridge;
413 nf_bridge_get(to->nf_bridge);
414 #endif
415 #ifdef CONFIG_NETFILTER_DEBUG
416 to->nf_debug = from->nf_debug;
417 #endif
418 #endif
419 }
420
421 /*
422 * This IP datagram is too large to be sent in one piece. Break it up into
423 * smaller pieces (each of size equal to IP header plus
424 * a block of the data of the original IP data part) that will yet fit in a
425 * single device frame, and queue such a frame for sending.
426 */
427
428 int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff*))
429 {
430 struct iphdr *iph;
431 int raw = 0;
432 int ptr;
433 struct net_device *dev;
434 struct sk_buff *skb2;
435 unsigned int mtu, hlen, left, len, ll_rs;
436 int offset;
437 int not_last_frag;
438 struct rtable *rt = (struct rtable*)skb->dst;
439 int err = 0;
440
441 dev = rt->u.dst.dev;
442
443 /*
444 * Point into the IP datagram header.
445 */
446
447 iph = skb->nh.iph;
448
449 if (unlikely((iph->frag_off & htons(IP_DF)) && !skb->local_df)) {
450 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
451 htonl(dst_pmtu(&rt->u.dst)));
452 kfree_skb(skb);
453 return -EMSGSIZE;
454 }
455
456 /*
457 * Setup starting values.
458 */
459
460 hlen = iph->ihl * 4;
461 mtu = dst_pmtu(&rt->u.dst) - hlen; /* Size of data space */
462
463 /* When frag_list is given, use it. First, check its validity:
464 * some transformers could create wrong frag_list or break existing
465 * one, it is not prohibited. In this case fall back to copying.
466 *
467 * LATER: this step can be merged to real generation of fragments,
468 * we can switch to copy when see the first bad fragment.
469 */
470 if (skb_shinfo(skb)->frag_list) {
471 struct sk_buff *frag;
472 int first_len = skb_pagelen(skb);
473
474 if (first_len - hlen > mtu ||
475 ((first_len - hlen) & 7) ||
476 (iph->frag_off & htons(IP_MF|IP_OFFSET)) ||
477 skb_cloned(skb))
478 goto slow_path;
479
480 for (frag = skb_shinfo(skb)->frag_list; frag; frag = frag->next) {
481 /* Correct geometry. */
482 if (frag->len > mtu ||
483 ((frag->len & 7) && frag->next) ||
484 skb_headroom(frag) < hlen)
485 goto slow_path;
486
487 /* Partially cloned skb? */
488 if (skb_shared(frag))
489 goto slow_path;
490 }
491
492 /* Everything is OK. Generate! */
493
494 err = 0;
495 offset = 0;
496 frag = skb_shinfo(skb)->frag_list;
497 skb_shinfo(skb)->frag_list = NULL;
498 skb->data_len = first_len - skb_headlen(skb);
499 skb->len = first_len;
500 iph->tot_len = htons(first_len);
501 iph->frag_off |= htons(IP_MF);
502 ip_send_check(iph);
503
504 for (;;) {
505 /* Prepare header of the next frame,
506 * before previous one went down. */
507 if (frag) {
508 frag->ip_summed = CHECKSUM_NONE;
509 frag->h.raw = frag->data;
510 frag->nh.raw = __skb_push(frag, hlen);
511 memcpy(frag->nh.raw, iph, hlen);
512 iph = frag->nh.iph;
513 iph->tot_len = htons(frag->len);
514 ip_copy_metadata(frag, skb);
515 if (offset == 0)
516 ip_options_fragment(frag);
517 offset += skb->len - hlen;
518 iph->frag_off = htons(offset>>3);
519 if (frag->next != NULL)
520 iph->frag_off |= htons(IP_MF);
521 /* Ready, complete checksum */
522 ip_send_check(iph);
523 }
524
525 err = output(skb);
526
527 if (err || !frag)
528 break;
529
530 skb = frag;
531 frag = skb->next;
532 skb->next = NULL;
533 }
534
535 if (err == 0) {
536 IP_INC_STATS(IPSTATS_MIB_FRAGOKS);
537 return 0;
538 }
539
540 while (frag) {
541 skb = frag->next;
542 kfree_skb(frag);
543 frag = skb;
544 }
545 IP_INC_STATS(IPSTATS_MIB_FRAGFAILS);
546 return err;
547 }
548
549 slow_path:
550 left = skb->len - hlen; /* Space per frame */
551 ptr = raw + hlen; /* Where to start from */
552
553 #ifdef CONFIG_BRIDGE_NETFILTER
554 /* for bridged IP traffic encapsulated inside f.e. a vlan header,
555 * we need to make room for the encapsulating header */
556 ll_rs = LL_RESERVED_SPACE_EXTRA(rt->u.dst.dev, nf_bridge_pad(skb));
557 mtu -= nf_bridge_pad(skb);
558 #else
559 ll_rs = LL_RESERVED_SPACE(rt->u.dst.dev);
560 #endif
561 /*
562 * Fragment the datagram.
563 */
564
565 offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3;
566 not_last_frag = iph->frag_off & htons(IP_MF);
567
568 /*
569 * Keep copying data until we run out.
570 */
571
572 while(left > 0) {
573 len = left;
574 /* IF: it doesn't fit, use 'mtu' - the data space left */
575 if (len > mtu)
576 len = mtu;
577 /* IF: we are not sending upto and including the packet end
578 then align the next start on an eight byte boundary */
579 if (len < left) {
580 len &= ~7;
581 }
582 /*
583 * Allocate buffer.
584 */
585
586 if ((skb2 = alloc_skb(len+hlen+ll_rs, GFP_ATOMIC)) == NULL) {
587 NETDEBUG(printk(KERN_INFO "IP: frag: no memory for new fragment!\n"));
588 err = -ENOMEM;
589 goto fail;
590 }
591
592 /*
593 * Set up data on packet
594 */
595
596 ip_copy_metadata(skb2, skb);
597 skb_reserve(skb2, ll_rs);
598 skb_put(skb2, len + hlen);
599 skb2->nh.raw = skb2->data;
600 skb2->h.raw = skb2->data + hlen;
601
602 /*
603 * Charge the memory for the fragment to any owner
604 * it might possess
605 */
606
607 if (skb->sk)
608 skb_set_owner_w(skb2, skb->sk);
609
610 /*
611 * Copy the packet header into the new buffer.
612 */
613
614 memcpy(skb2->nh.raw, skb->data, hlen);
615
616 /*
617 * Copy a block of the IP datagram.
618 */
619 if (skb_copy_bits(skb, ptr, skb2->h.raw, len))
620 BUG();
621 left -= len;
622
623 /*
624 * Fill in the new header fields.
625 */
626 iph = skb2->nh.iph;
627 iph->frag_off = htons((offset >> 3));
628
629 /* ANK: dirty, but effective trick. Upgrade options only if
630 * the segment to be fragmented was THE FIRST (otherwise,
631 * options are already fixed) and make it ONCE
632 * on the initial skb, so that all the following fragments
633 * will inherit fixed options.
634 */
635 if (offset == 0)
636 ip_options_fragment(skb);
637
638 /*
639 * Added AC : If we are fragmenting a fragment that's not the
640 * last fragment then keep MF on each bit
641 */
642 if (left > 0 || not_last_frag)
643 iph->frag_off |= htons(IP_MF);
644 ptr += len;
645 offset += len;
646
647 /*
648 * Put this fragment into the sending queue.
649 */
650
651 IP_INC_STATS(IPSTATS_MIB_FRAGCREATES);
652
653 iph->tot_len = htons(len + hlen);
654
655 ip_send_check(iph);
656
657 err = output(skb2);
658 if (err)
659 goto fail;
660 }
661 kfree_skb(skb);
662 IP_INC_STATS(IPSTATS_MIB_FRAGOKS);
663 return err;
664
665 fail:
666 kfree_skb(skb);
667 IP_INC_STATS(IPSTATS_MIB_FRAGFAILS);
668 return err;
669 }
670
671 int
672 ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
673 {
674 struct iovec *iov = from;
675
676 if (skb->ip_summed == CHECKSUM_HW) {
677 if (memcpy_fromiovecend(to, iov, offset, len) < 0)
678 return -EFAULT;
679 } else {
680 unsigned int csum = 0;
681 if (csum_partial_copy_fromiovecend(to, iov, offset, len, &csum) < 0)
682 return -EFAULT;
683 skb->csum = csum_block_add(skb->csum, csum, odd);
684 }
685 return 0;
686 }
687
688 static inline unsigned int
689 csum_page(struct page *page, int offset, int copy)
690 {
691 char *kaddr;
692 unsigned int csum;
693 kaddr = kmap(page);
694 csum = csum_partial(kaddr + offset, copy, 0);
695 kunmap(page);
696 return csum;
697 }
698
699 /*
700 * ip_append_data() and ip_append_page() can make one large IP datagram
701 * from many pieces of data. Each pieces will be holded on the socket
702 * until ip_push_pending_frames() is called. Each piece can be a page
703 * or non-page data.
704 *
705 * Not only UDP, other transport protocols - e.g. raw sockets - can use
706 * this interface potentially.
707 *
708 * LATER: length must be adjusted by pad at tail, when it is required.
709 */
710 int ip_append_data(struct sock *sk,
711 int getfrag(void *from, char *to, int offset, int len,
712 int odd, struct sk_buff *skb),
713 void *from, int length, int transhdrlen,
714 struct ipcm_cookie *ipc, struct rtable *rt,
715 unsigned int flags)
716 {
717 struct inet_sock *inet = inet_sk(sk);
718 struct sk_buff *skb;
719
720 struct ip_options *opt = NULL;
721 int hh_len;
722 int exthdrlen;
723 int mtu;
724 int copy;
725 int err;
726 int offset = 0;
727 unsigned int maxfraglen, fragheaderlen;
728 int csummode = CHECKSUM_NONE;
729
730 if (flags&MSG_PROBE)
731 return 0;
732
733 if (skb_queue_empty(&sk->sk_write_queue)) {
734 /*
735 * setup for corking.
736 */
737 opt = ipc->opt;
738 if (opt) {
739 if (inet->cork.opt == NULL) {
740 inet->cork.opt = kmalloc(sizeof(struct ip_options) + 40, sk->sk_allocation);
741 if (unlikely(inet->cork.opt == NULL))
742 return -ENOBUFS;
743 }
744 memcpy(inet->cork.opt, opt, sizeof(struct ip_options)+opt->optlen);
745 inet->cork.flags |= IPCORK_OPT;
746 inet->cork.addr = ipc->addr;
747 }
748 dst_hold(&rt->u.dst);
749 inet->cork.fragsize = mtu = dst_pmtu(&rt->u.dst);
750 inet->cork.rt = rt;
751 inet->cork.length = 0;
752 sk->sk_sndmsg_page = NULL;
753 sk->sk_sndmsg_off = 0;
754 if ((exthdrlen = rt->u.dst.header_len) != 0) {
755 length += exthdrlen;
756 transhdrlen += exthdrlen;
757 }
758 } else {
759 rt = inet->cork.rt;
760 if (inet->cork.flags & IPCORK_OPT)
761 opt = inet->cork.opt;
762
763 transhdrlen = 0;
764 exthdrlen = 0;
765 mtu = inet->cork.fragsize;
766 }
767 hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
768
769 fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
770 maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
771
772 if (inet->cork.length + length > 0xFFFF - fragheaderlen) {
773 ip_local_error(sk, EMSGSIZE, rt->rt_dst, inet->dport, mtu-exthdrlen);
774 return -EMSGSIZE;
775 }
776
777 /*
778 * transhdrlen > 0 means that this is the first fragment and we wish
779 * it won't be fragmented in the future.
780 */
781 if (transhdrlen &&
782 length + fragheaderlen <= mtu &&
783 rt->u.dst.dev->features&(NETIF_F_IP_CSUM|NETIF_F_NO_CSUM|NETIF_F_HW_CSUM) &&
784 !exthdrlen)
785 csummode = CHECKSUM_HW;
786
787 inet->cork.length += length;
788
789 /* So, what's going on in the loop below?
790 *
791 * We use calculated fragment length to generate chained skb,
792 * each of segments is IP fragment ready for sending to network after
793 * adding appropriate IP header.
794 */
795
796 if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
797 goto alloc_new_skb;
798
799 while (length > 0) {
800 /* Check if the remaining data fits into current packet. */
801 copy = mtu - skb->len;
802 if (copy < length)
803 copy = maxfraglen - skb->len;
804 if (copy <= 0) {
805 char *data;
806 unsigned int datalen;
807 unsigned int fraglen;
808 unsigned int fraggap;
809 unsigned int alloclen;
810 struct sk_buff *skb_prev;
811 alloc_new_skb:
812 skb_prev = skb;
813 if (skb_prev)
814 fraggap = skb_prev->len - maxfraglen;
815 else
816 fraggap = 0;
817
818 /*
819 * If remaining data exceeds the mtu,
820 * we know we need more fragment(s).
821 */
822 datalen = length + fraggap;
823 if (datalen > mtu - fragheaderlen)
824 datalen = maxfraglen - fragheaderlen;
825 fraglen = datalen + fragheaderlen;
826
827 if ((flags & MSG_MORE) &&
828 !(rt->u.dst.dev->features&NETIF_F_SG))
829 alloclen = mtu;
830 else
831 alloclen = datalen + fragheaderlen;
832
833 /* The last fragment gets additional space at tail.
834 * Note, with MSG_MORE we overallocate on fragments,
835 * because we have no idea what fragment will be
836 * the last.
837 */
838 if (datalen == length)
839 alloclen += rt->u.dst.trailer_len;
840
841 if (transhdrlen) {
842 skb = sock_alloc_send_skb(sk,
843 alloclen + hh_len + 15,
844 (flags & MSG_DONTWAIT), &err);
845 } else {
846 skb = NULL;
847 if (atomic_read(&sk->sk_wmem_alloc) <=
848 2 * sk->sk_sndbuf)
849 skb = sock_wmalloc(sk,
850 alloclen + hh_len + 15, 1,
851 sk->sk_allocation);
852 if (unlikely(skb == NULL))
853 err = -ENOBUFS;
854 }
855 if (skb == NULL)
856 goto error;
857
858 /*
859 * Fill in the control structures
860 */
861 skb->ip_summed = csummode;
862 skb->csum = 0;
863 skb_reserve(skb, hh_len);
864
865 /*
866 * Find where to start putting bytes.
867 */
868 data = skb_put(skb, fraglen);
869 skb->nh.raw = data + exthdrlen;
870 data += fragheaderlen;
871 skb->h.raw = data + exthdrlen;
872
873 if (fraggap) {
874 skb->csum = skb_copy_and_csum_bits(
875 skb_prev, maxfraglen,
876 data + transhdrlen, fraggap, 0);
877 skb_prev->csum = csum_sub(skb_prev->csum,
878 skb->csum);
879 data += fraggap;
880 skb_trim(skb_prev, maxfraglen);
881 }
882
883 copy = datalen - transhdrlen - fraggap;
884 if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
885 err = -EFAULT;
886 kfree_skb(skb);
887 goto error;
888 }
889
890 offset += copy;
891 length -= datalen - fraggap;
892 transhdrlen = 0;
893 exthdrlen = 0;
894 csummode = CHECKSUM_NONE;
895
896 /*
897 * Put the packet on the pending queue.
898 */
899 __skb_queue_tail(&sk->sk_write_queue, skb);
900 continue;
901 }
902
903 if (copy > length)
904 copy = length;
905
906 if (!(rt->u.dst.dev->features&NETIF_F_SG)) {
907 unsigned int off;
908
909 off = skb->len;
910 if (getfrag(from, skb_put(skb, copy),
911 offset, copy, off, skb) < 0) {
912 __skb_trim(skb, off);
913 err = -EFAULT;
914 goto error;
915 }
916 } else {
917 int i = skb_shinfo(skb)->nr_frags;
918 skb_frag_t *frag = &skb_shinfo(skb)->frags[i-1];
919 struct page *page = sk->sk_sndmsg_page;
920 int off = sk->sk_sndmsg_off;
921 unsigned int left;
922
923 if (page && (left = PAGE_SIZE - off) > 0) {
924 if (copy >= left)
925 copy = left;
926 if (page != frag->page) {
927 if (i == MAX_SKB_FRAGS) {
928 err = -EMSGSIZE;
929 goto error;
930 }
931 get_page(page);
932 skb_fill_page_desc(skb, i, page, sk->sk_sndmsg_off, 0);
933 frag = &skb_shinfo(skb)->frags[i];
934 }
935 } else if (i < MAX_SKB_FRAGS) {
936 if (copy > PAGE_SIZE)
937 copy = PAGE_SIZE;
938 page = alloc_pages(sk->sk_allocation, 0);
939 if (page == NULL) {
940 err = -ENOMEM;
941 goto error;
942 }
943 sk->sk_sndmsg_page = page;
944 sk->sk_sndmsg_off = 0;
945
946 skb_fill_page_desc(skb, i, page, 0, 0);
947 frag = &skb_shinfo(skb)->frags[i];
948 skb->truesize += PAGE_SIZE;
949 atomic_add(PAGE_SIZE, &sk->sk_wmem_alloc);
950 } else {
951 err = -EMSGSIZE;
952 goto error;
953 }
954 if (getfrag(from, page_address(frag->page)+frag->page_offset+frag->size, offset, copy, skb->len, skb) < 0) {
955 err = -EFAULT;
956 goto error;
957 }
958 sk->sk_sndmsg_off += copy;
959 frag->size += copy;
960 skb->len += copy;
961 skb->data_len += copy;
962 }
963 offset += copy;
964 length -= copy;
965 }
966
967 return 0;
968
969 error:
970 inet->cork.length -= length;
971 IP_INC_STATS(IPSTATS_MIB_OUTDISCARDS);
972 return err;
973 }
974
975 ssize_t ip_append_page(struct sock *sk, struct page *page,
976 int offset, size_t size, int flags)
977 {
978 struct inet_sock *inet = inet_sk(sk);
979 struct sk_buff *skb;
980 struct rtable *rt;
981 struct ip_options *opt = NULL;
982 int hh_len;
983 int mtu;
984 int len;
985 int err;
986 unsigned int maxfraglen, fragheaderlen, fraggap;
987
988 if (inet->hdrincl)
989 return -EPERM;
990
991 if (flags&MSG_PROBE)
992 return 0;
993
994 if (skb_queue_empty(&sk->sk_write_queue))
995 return -EINVAL;
996
997 rt = inet->cork.rt;
998 if (inet->cork.flags & IPCORK_OPT)
999 opt = inet->cork.opt;
1000
1001 if (!(rt->u.dst.dev->features&NETIF_F_SG))
1002 return -EOPNOTSUPP;
1003
1004 hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
1005 mtu = inet->cork.fragsize;
1006
1007 fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
1008 maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
1009
1010 if (inet->cork.length + size > 0xFFFF - fragheaderlen) {
1011 ip_local_error(sk, EMSGSIZE, rt->rt_dst, inet->dport, mtu);
1012 return -EMSGSIZE;
1013 }
1014
1015 if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
1016 return -EINVAL;
1017
1018 inet->cork.length += size;
1019
1020 while (size > 0) {
1021 int i;
1022
1023 /* Check if the remaining data fits into current packet. */
1024 len = mtu - skb->len;
1025 if (len < size)
1026 len = maxfraglen - skb->len;
1027 if (len <= 0) {
1028 struct sk_buff *skb_prev;
1029 char *data;
1030 struct iphdr *iph;
1031 int alloclen;
1032
1033 skb_prev = skb;
1034 if (skb_prev)
1035 fraggap = skb_prev->len - maxfraglen;
1036 else
1037 fraggap = 0;
1038
1039 alloclen = fragheaderlen + hh_len + fraggap + 15;
1040 skb = sock_wmalloc(sk, alloclen, 1, sk->sk_allocation);
1041 if (unlikely(!skb)) {
1042 err = -ENOBUFS;
1043 goto error;
1044 }
1045
1046 /*
1047 * Fill in the control structures
1048 */
1049 skb->ip_summed = CHECKSUM_NONE;
1050 skb->csum = 0;
1051 skb_reserve(skb, hh_len);
1052
1053 /*
1054 * Find where to start putting bytes.
1055 */
1056 data = skb_put(skb, fragheaderlen + fraggap);
1057 skb->nh.iph = iph = (struct iphdr *)data;
1058 data += fragheaderlen;
1059 skb->h.raw = data;
1060
1061 if (fraggap) {
1062 skb->csum = skb_copy_and_csum_bits(
1063 skb_prev, maxfraglen,
1064 data, fraggap, 0);
1065 skb_prev->csum = csum_sub(skb_prev->csum,
1066 skb->csum);
1067 skb_trim(skb_prev, maxfraglen);
1068 }
1069
1070 /*
1071 * Put the packet on the pending queue.
1072 */
1073 __skb_queue_tail(&sk->sk_write_queue, skb);
1074 continue;
1075 }
1076
1077 i = skb_shinfo(skb)->nr_frags;
1078 if (len > size)
1079 len = size;
1080 if (skb_can_coalesce(skb, i, page, offset)) {
1081 skb_shinfo(skb)->frags[i-1].size += len;
1082 } else if (i < MAX_SKB_FRAGS) {
1083 get_page(page);
1084 skb_fill_page_desc(skb, i, page, offset, len);
1085 } else {
1086 err = -EMSGSIZE;
1087 goto error;
1088 }
1089
1090 if (skb->ip_summed == CHECKSUM_NONE) {
1091 unsigned int csum;
1092 csum = csum_page(page, offset, len);
1093 skb->csum = csum_block_add(skb->csum, csum, skb->len);
1094 }
1095
1096 skb->len += len;
1097 skb->data_len += len;
1098 offset += len;
1099 size -= len;
1100 }
1101 return 0;
1102
1103 error:
1104 inet->cork.length -= size;
1105 IP_INC_STATS(IPSTATS_MIB_OUTDISCARDS);
1106 return err;
1107 }
1108
1109 /*
1110 * Combined all pending IP fragments on the socket as one IP datagram
1111 * and push them out.
1112 */
1113 int ip_push_pending_frames(struct sock *sk)
1114 {
1115 struct sk_buff *skb, *tmp_skb;
1116 struct sk_buff **tail_skb;
1117 struct inet_sock *inet = inet_sk(sk);
1118 struct ip_options *opt = NULL;
1119 struct rtable *rt = inet->cork.rt;
1120 struct iphdr *iph;
1121 int df = 0;
1122 __u8 ttl;
1123 int err = 0;
1124
1125 if ((skb = __skb_dequeue(&sk->sk_write_queue)) == NULL)
1126 goto out;
1127 tail_skb = &(skb_shinfo(skb)->frag_list);
1128
1129 /* move skb->data to ip header from ext header */
1130 if (skb->data < skb->nh.raw)
1131 __skb_pull(skb, skb->nh.raw - skb->data);
1132 while ((tmp_skb = __skb_dequeue(&sk->sk_write_queue)) != NULL) {
1133 __skb_pull(tmp_skb, skb->h.raw - skb->nh.raw);
1134 *tail_skb = tmp_skb;
1135 tail_skb = &(tmp_skb->next);
1136 skb->len += tmp_skb->len;
1137 skb->data_len += tmp_skb->len;
1138 skb->truesize += tmp_skb->truesize;
1139 __sock_put(tmp_skb->sk);
1140 tmp_skb->destructor = NULL;
1141 tmp_skb->sk = NULL;
1142 }
1143
1144 /* Unless user demanded real pmtu discovery (IP_PMTUDISC_DO), we allow
1145 * to fragment the frame generated here. No matter, what transforms
1146 * how transforms change size of the packet, it will come out.
1147 */
1148 if (inet->pmtudisc != IP_PMTUDISC_DO)
1149 skb->local_df = 1;
1150
1151 /* DF bit is set when we want to see DF on outgoing frames.
1152 * If local_df is set too, we still allow to fragment this frame
1153 * locally. */
1154 if (inet->pmtudisc == IP_PMTUDISC_DO ||
1155 (!skb_shinfo(skb)->frag_list && ip_dont_fragment(sk, &rt->u.dst)))
1156 df = htons(IP_DF);
1157
1158 if (inet->cork.flags & IPCORK_OPT)
1159 opt = inet->cork.opt;
1160
1161 if (rt->rt_type == RTN_MULTICAST)
1162 ttl = inet->mc_ttl;
1163 else
1164 ttl = ip_select_ttl(inet, &rt->u.dst);
1165
1166 iph = (struct iphdr *)skb->data;
1167 iph->version = 4;
1168 iph->ihl = 5;
1169 if (opt) {
1170 iph->ihl += opt->optlen>>2;
1171 ip_options_build(skb, opt, inet->cork.addr, rt, 0);
1172 }
1173 iph->tos = inet->tos;
1174 iph->tot_len = htons(skb->len);
1175 iph->frag_off = df;
1176 if (!df) {
1177 __ip_select_ident(iph, &rt->u.dst, 0);
1178 } else {
1179 iph->id = htons(inet->id++);
1180 }
1181 iph->ttl = ttl;
1182 iph->protocol = sk->sk_protocol;
1183 iph->saddr = rt->rt_src;
1184 iph->daddr = rt->rt_dst;
1185 ip_send_check(iph);
1186
1187 skb->priority = sk->sk_priority;
1188 skb->dst = dst_clone(&rt->u.dst);
1189
1190 /* Netfilter gets whole the not fragmented skb. */
1191 err = NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, skb, NULL,
1192 skb->dst->dev, dst_output);
1193 if (err) {
1194 if (err > 0)
1195 err = inet->recverr ? net_xmit_errno(err) : 0;
1196 if (err)
1197 goto error;
1198 }
1199
1200 out:
1201 inet->cork.flags &= ~IPCORK_OPT;
1202 if (inet->cork.opt) {
1203 kfree(inet->cork.opt);
1204 inet->cork.opt = NULL;
1205 }
1206 if (inet->cork.rt) {
1207 ip_rt_put(inet->cork.rt);
1208 inet->cork.rt = NULL;
1209 }
1210 return err;
1211
1212 error:
1213 IP_INC_STATS(IPSTATS_MIB_OUTDISCARDS);
1214 goto out;
1215 }
1216
1217 /*
1218 * Throw away all pending data on the socket.
1219 */
1220 void ip_flush_pending_frames(struct sock *sk)
1221 {
1222 struct inet_sock *inet = inet_sk(sk);
1223 struct sk_buff *skb;
1224
1225 while ((skb = __skb_dequeue_tail(&sk->sk_write_queue)) != NULL)
1226 kfree_skb(skb);
1227
1228 inet->cork.flags &= ~IPCORK_OPT;
1229 if (inet->cork.opt) {
1230 kfree(inet->cork.opt);
1231 inet->cork.opt = NULL;
1232 }
1233 if (inet->cork.rt) {
1234 ip_rt_put(inet->cork.rt);
1235 inet->cork.rt = NULL;
1236 }
1237 }
1238
1239
1240 /*
1241 * Fetch data from kernel space and fill in checksum if needed.
1242 */
1243 static int ip_reply_glue_bits(void *dptr, char *to, int offset,
1244 int len, int odd, struct sk_buff *skb)
1245 {
1246 unsigned int csum;
1247
1248 csum = csum_partial_copy_nocheck(dptr+offset, to, len, 0);
1249 skb->csum = csum_block_add(skb->csum, csum, odd);
1250 return 0;
1251 }
1252
1253 /*
1254 * Generic function to send a packet as reply to another packet.
1255 * Used to send TCP resets so far. ICMP should use this function too.
1256 *
1257 * Should run single threaded per socket because it uses the sock
1258 * structure to pass arguments.
1259 *
1260 * LATER: switch from ip_build_xmit to ip_append_*
1261 */
1262 void ip_send_reply(struct sock *sk, struct sk_buff *skb, struct ip_reply_arg *arg,
1263 unsigned int len)
1264 {
1265 struct inet_sock *inet = inet_sk(sk);
1266 struct {
1267 struct ip_options opt;
1268 char data[40];
1269 } replyopts;
1270 struct ipcm_cookie ipc;
1271 u32 daddr;
1272 struct rtable *rt = (struct rtable*)skb->dst;
1273
1274 if (ip_options_echo(&replyopts.opt, skb))
1275 return;
1276
1277 daddr = ipc.addr = rt->rt_src;
1278 ipc.opt = NULL;
1279
1280 if (replyopts.opt.optlen) {
1281 ipc.opt = &replyopts.opt;
1282
1283 if (ipc.opt->srr)
1284 daddr = replyopts.opt.faddr;
1285 }
1286
1287 {
1288 struct flowi fl = { .nl_u = { .ip4_u =
1289 { .daddr = daddr,
1290 .saddr = rt->rt_spec_dst,
1291 .tos = RT_TOS(skb->nh.iph->tos) } },
1292 /* Not quite clean, but right. */
1293 .uli_u = { .ports =
1294 { .sport = skb->h.th->dest,
1295 .dport = skb->h.th->source } },
1296 .proto = sk->sk_protocol };
1297 if (ip_route_output_key(&rt, &fl))
1298 return;
1299 }
1300
1301 /* And let IP do all the hard work.
1302
1303 This chunk is not reenterable, hence spinlock.
1304 Note that it uses the fact, that this function is called
1305 with locally disabled BH and that sk cannot be already spinlocked.
1306 */
1307 bh_lock_sock(sk);
1308 inet->tos = skb->nh.iph->tos;
1309 sk->sk_priority = skb->priority;
1310 sk->sk_protocol = skb->nh.iph->protocol;
1311 ip_append_data(sk, ip_reply_glue_bits, arg->iov->iov_base, len, 0,
1312 &ipc, rt, MSG_DONTWAIT);
1313 if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {
1314 if (arg->csumoffset >= 0)
1315 *((u16 *)skb->h.raw + arg->csumoffset) = csum_fold(csum_add(skb->csum, arg->csum));
1316 skb->ip_summed = CHECKSUM_NONE;
1317 ip_push_pending_frames(sk);
1318 }
1319
1320 bh_unlock_sock(sk);
1321
1322 ip_rt_put(rt);
1323 }
1324
1325 /*
1326 * IP protocol layer initialiser
1327 */
1328
1329 static struct packet_type ip_packet_type = {
1330 .type = __constant_htons(ETH_P_IP),
1331 .func = ip_rcv,
1332 };
1333
1334 /*
1335 * IP registers the packet type and then calls the subprotocol initialisers
1336 */
1337
1338 void __init ip_init(void)
1339 {
1340 dev_add_pack(&ip_packet_type);
1341
1342 ip_rt_init();
1343 inet_initpeers();
1344
1345 #if defined(CONFIG_IP_MULTICAST) && defined(CONFIG_PROC_FS)
1346 igmp_mc_proc_init();
1347 #endif
1348 }
1349
1350 EXPORT_SYMBOL(ip_finish_output);
1351 EXPORT_SYMBOL(ip_fragment);
1352 EXPORT_SYMBOL(ip_generic_getfrag);
1353 EXPORT_SYMBOL(ip_queue_xmit);
1354 EXPORT_SYMBOL(ip_send_check);
1355
1356 #ifdef CONFIG_SYSCTL
1357 EXPORT_SYMBOL(sysctl_ip_default_ttl);
1358 #endif
1359
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