xref: /openbmc/linux/net/ipv4/ip_output.c (revision fd589a8f)
1 /*
2  * INET		An implementation of the TCP/IP protocol suite for the LINUX
3  *		operating system.  INET is implemented using the  BSD Socket
4  *		interface as the means of communication with the user level.
5  *
6  *		The Internet Protocol (IP) output module.
7  *
8  * Authors:	Ross Biro
9  *		Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
10  *		Donald Becker, <becker@super.org>
11  *		Alan Cox, <Alan.Cox@linux.org>
12  *		Richard Underwood
13  *		Stefan Becker, <stefanb@yello.ping.de>
14  *		Jorge Cwik, <jorge@laser.satlink.net>
15  *		Arnt Gulbrandsen, <agulbra@nvg.unit.no>
16  *		Hirokazu Takahashi, <taka@valinux.co.jp>
17  *
18  *	See ip_input.c for original log
19  *
20  *	Fixes:
21  *		Alan Cox	:	Missing nonblock feature in ip_build_xmit.
22  *		Mike Kilburn	:	htons() missing in ip_build_xmit.
23  *		Bradford Johnson:	Fix faulty handling of some frames when
24  *					no route is found.
25  *		Alexander Demenshin:	Missing sk/skb free in ip_queue_xmit
26  *					(in case if packet not accepted by
27  *					output firewall rules)
28  *		Mike McLagan	:	Routing by source
29  *		Alexey Kuznetsov:	use new route cache
30  *		Andi Kleen:		Fix broken PMTU recovery and remove
31  *					some redundant tests.
32  *	Vitaly E. Lavrov	:	Transparent proxy revived after year coma.
33  *		Andi Kleen	: 	Replace ip_reply with ip_send_reply.
34  *		Andi Kleen	:	Split fast and slow ip_build_xmit path
35  *					for decreased register pressure on x86
36  *					and more readibility.
37  *		Marc Boucher	:	When call_out_firewall returns FW_QUEUE,
38  *					silently drop skb instead of failing with -EPERM.
39  *		Detlev Wengorz	:	Copy protocol for fragments.
40  *		Hirokazu Takahashi:	HW checksumming for outgoing UDP
41  *					datagrams.
42  *		Hirokazu Takahashi:	sendfile() on UDP works now.
43  */
44 
45 #include <asm/uaccess.h>
46 #include <asm/system.h>
47 #include <linux/module.h>
48 #include <linux/types.h>
49 #include <linux/kernel.h>
50 #include <linux/mm.h>
51 #include <linux/string.h>
52 #include <linux/errno.h>
53 #include <linux/highmem.h>
54 
55 #include <linux/socket.h>
56 #include <linux/sockios.h>
57 #include <linux/in.h>
58 #include <linux/inet.h>
59 #include <linux/netdevice.h>
60 #include <linux/etherdevice.h>
61 #include <linux/proc_fs.h>
62 #include <linux/stat.h>
63 #include <linux/init.h>
64 
65 #include <net/snmp.h>
66 #include <net/ip.h>
67 #include <net/protocol.h>
68 #include <net/route.h>
69 #include <net/xfrm.h>
70 #include <linux/skbuff.h>
71 #include <net/sock.h>
72 #include <net/arp.h>
73 #include <net/icmp.h>
74 #include <net/checksum.h>
75 #include <net/inetpeer.h>
76 #include <linux/igmp.h>
77 #include <linux/netfilter_ipv4.h>
78 #include <linux/netfilter_bridge.h>
79 #include <linux/mroute.h>
80 #include <linux/netlink.h>
81 #include <linux/tcp.h>
82 
83 int sysctl_ip_default_ttl __read_mostly = IPDEFTTL;
84 
85 /* Generate a checksum for an outgoing IP datagram. */
86 __inline__ void ip_send_check(struct iphdr *iph)
87 {
88 	iph->check = 0;
89 	iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
90 }
91 
92 int __ip_local_out(struct sk_buff *skb)
93 {
94 	struct iphdr *iph = ip_hdr(skb);
95 
96 	iph->tot_len = htons(skb->len);
97 	ip_send_check(iph);
98 	return nf_hook(PF_INET, NF_INET_LOCAL_OUT, skb, NULL, skb_dst(skb)->dev,
99 		       dst_output);
100 }
101 
102 int ip_local_out(struct sk_buff *skb)
103 {
104 	int err;
105 
106 	err = __ip_local_out(skb);
107 	if (likely(err == 1))
108 		err = dst_output(skb);
109 
110 	return err;
111 }
112 EXPORT_SYMBOL_GPL(ip_local_out);
113 
114 /* dev_loopback_xmit for use with netfilter. */
115 static int ip_dev_loopback_xmit(struct sk_buff *newskb)
116 {
117 	skb_reset_mac_header(newskb);
118 	__skb_pull(newskb, skb_network_offset(newskb));
119 	newskb->pkt_type = PACKET_LOOPBACK;
120 	newskb->ip_summed = CHECKSUM_UNNECESSARY;
121 	WARN_ON(!skb_dst(newskb));
122 	netif_rx(newskb);
123 	return 0;
124 }
125 
126 static inline int ip_select_ttl(struct inet_sock *inet, struct dst_entry *dst)
127 {
128 	int ttl = inet->uc_ttl;
129 
130 	if (ttl < 0)
131 		ttl = dst_metric(dst, RTAX_HOPLIMIT);
132 	return ttl;
133 }
134 
135 /*
136  *		Add an ip header to a skbuff and send it out.
137  *
138  */
139 int ip_build_and_send_pkt(struct sk_buff *skb, struct sock *sk,
140 			  __be32 saddr, __be32 daddr, struct ip_options *opt)
141 {
142 	struct inet_sock *inet = inet_sk(sk);
143 	struct rtable *rt = skb_rtable(skb);
144 	struct iphdr *iph;
145 
146 	/* Build the IP header. */
147 	skb_push(skb, sizeof(struct iphdr) + (opt ? opt->optlen : 0));
148 	skb_reset_network_header(skb);
149 	iph = ip_hdr(skb);
150 	iph->version  = 4;
151 	iph->ihl      = 5;
152 	iph->tos      = inet->tos;
153 	if (ip_dont_fragment(sk, &rt->u.dst))
154 		iph->frag_off = htons(IP_DF);
155 	else
156 		iph->frag_off = 0;
157 	iph->ttl      = ip_select_ttl(inet, &rt->u.dst);
158 	iph->daddr    = rt->rt_dst;
159 	iph->saddr    = rt->rt_src;
160 	iph->protocol = sk->sk_protocol;
161 	ip_select_ident(iph, &rt->u.dst, sk);
162 
163 	if (opt && opt->optlen) {
164 		iph->ihl += opt->optlen>>2;
165 		ip_options_build(skb, opt, daddr, rt, 0);
166 	}
167 
168 	skb->priority = sk->sk_priority;
169 	skb->mark = sk->sk_mark;
170 
171 	/* Send it out. */
172 	return ip_local_out(skb);
173 }
174 
175 EXPORT_SYMBOL_GPL(ip_build_and_send_pkt);
176 
177 static inline int ip_finish_output2(struct sk_buff *skb)
178 {
179 	struct dst_entry *dst = skb_dst(skb);
180 	struct rtable *rt = (struct rtable *)dst;
181 	struct net_device *dev = dst->dev;
182 	unsigned int hh_len = LL_RESERVED_SPACE(dev);
183 
184 	if (rt->rt_type == RTN_MULTICAST) {
185 		IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUTMCAST, skb->len);
186 	} else if (rt->rt_type == RTN_BROADCAST)
187 		IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUTBCAST, skb->len);
188 
189 	/* Be paranoid, rather than too clever. */
190 	if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) {
191 		struct sk_buff *skb2;
192 
193 		skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev));
194 		if (skb2 == NULL) {
195 			kfree_skb(skb);
196 			return -ENOMEM;
197 		}
198 		if (skb->sk)
199 			skb_set_owner_w(skb2, skb->sk);
200 		kfree_skb(skb);
201 		skb = skb2;
202 	}
203 
204 	if (dst->hh)
205 		return neigh_hh_output(dst->hh, skb);
206 	else if (dst->neighbour)
207 		return dst->neighbour->output(skb);
208 
209 	if (net_ratelimit())
210 		printk(KERN_DEBUG "ip_finish_output2: No header cache and no neighbour!\n");
211 	kfree_skb(skb);
212 	return -EINVAL;
213 }
214 
215 static inline int ip_skb_dst_mtu(struct sk_buff *skb)
216 {
217 	struct inet_sock *inet = skb->sk ? inet_sk(skb->sk) : NULL;
218 
219 	return (inet && inet->pmtudisc == IP_PMTUDISC_PROBE) ?
220 	       skb_dst(skb)->dev->mtu : dst_mtu(skb_dst(skb));
221 }
222 
223 static int ip_finish_output(struct sk_buff *skb)
224 {
225 #if defined(CONFIG_NETFILTER) && defined(CONFIG_XFRM)
226 	/* Policy lookup after SNAT yielded a new policy */
227 	if (skb_dst(skb)->xfrm != NULL) {
228 		IPCB(skb)->flags |= IPSKB_REROUTED;
229 		return dst_output(skb);
230 	}
231 #endif
232 	if (skb->len > ip_skb_dst_mtu(skb) && !skb_is_gso(skb))
233 		return ip_fragment(skb, ip_finish_output2);
234 	else
235 		return ip_finish_output2(skb);
236 }
237 
238 int ip_mc_output(struct sk_buff *skb)
239 {
240 	struct sock *sk = skb->sk;
241 	struct rtable *rt = skb_rtable(skb);
242 	struct net_device *dev = rt->u.dst.dev;
243 
244 	/*
245 	 *	If the indicated interface is up and running, send the packet.
246 	 */
247 	IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUT, skb->len);
248 
249 	skb->dev = dev;
250 	skb->protocol = htons(ETH_P_IP);
251 
252 	/*
253 	 *	Multicasts are looped back for other local users
254 	 */
255 
256 	if (rt->rt_flags&RTCF_MULTICAST) {
257 		if ((!sk || inet_sk(sk)->mc_loop)
258 #ifdef CONFIG_IP_MROUTE
259 		/* Small optimization: do not loopback not local frames,
260 		   which returned after forwarding; they will be  dropped
261 		   by ip_mr_input in any case.
262 		   Note, that local frames are looped back to be delivered
263 		   to local recipients.
264 
265 		   This check is duplicated in ip_mr_input at the moment.
266 		 */
267 		    && ((rt->rt_flags&RTCF_LOCAL) || !(IPCB(skb)->flags&IPSKB_FORWARDED))
268 #endif
269 		) {
270 			struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
271 			if (newskb)
272 				NF_HOOK(PF_INET, NF_INET_POST_ROUTING, newskb,
273 					NULL, newskb->dev,
274 					ip_dev_loopback_xmit);
275 		}
276 
277 		/* Multicasts with ttl 0 must not go beyond the host */
278 
279 		if (ip_hdr(skb)->ttl == 0) {
280 			kfree_skb(skb);
281 			return 0;
282 		}
283 	}
284 
285 	if (rt->rt_flags&RTCF_BROADCAST) {
286 		struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
287 		if (newskb)
288 			NF_HOOK(PF_INET, NF_INET_POST_ROUTING, newskb, NULL,
289 				newskb->dev, ip_dev_loopback_xmit);
290 	}
291 
292 	return NF_HOOK_COND(PF_INET, NF_INET_POST_ROUTING, skb, NULL, skb->dev,
293 			    ip_finish_output,
294 			    !(IPCB(skb)->flags & IPSKB_REROUTED));
295 }
296 
297 int ip_output(struct sk_buff *skb)
298 {
299 	struct net_device *dev = skb_dst(skb)->dev;
300 
301 	IP_UPD_PO_STATS(dev_net(dev), IPSTATS_MIB_OUT, skb->len);
302 
303 	skb->dev = dev;
304 	skb->protocol = htons(ETH_P_IP);
305 
306 	return NF_HOOK_COND(PF_INET, NF_INET_POST_ROUTING, skb, NULL, dev,
307 			    ip_finish_output,
308 			    !(IPCB(skb)->flags & IPSKB_REROUTED));
309 }
310 
311 int ip_queue_xmit(struct sk_buff *skb, int ipfragok)
312 {
313 	struct sock *sk = skb->sk;
314 	struct inet_sock *inet = inet_sk(sk);
315 	struct ip_options *opt = inet->opt;
316 	struct rtable *rt;
317 	struct iphdr *iph;
318 
319 	/* Skip all of this if the packet is already routed,
320 	 * f.e. by something like SCTP.
321 	 */
322 	rt = skb_rtable(skb);
323 	if (rt != NULL)
324 		goto packet_routed;
325 
326 	/* Make sure we can route this packet. */
327 	rt = (struct rtable *)__sk_dst_check(sk, 0);
328 	if (rt == NULL) {
329 		__be32 daddr;
330 
331 		/* Use correct destination address if we have options. */
332 		daddr = inet->daddr;
333 		if(opt && opt->srr)
334 			daddr = opt->faddr;
335 
336 		{
337 			struct flowi fl = { .oif = sk->sk_bound_dev_if,
338 					    .nl_u = { .ip4_u =
339 						      { .daddr = daddr,
340 							.saddr = inet->saddr,
341 							.tos = RT_CONN_FLAGS(sk) } },
342 					    .proto = sk->sk_protocol,
343 					    .flags = inet_sk_flowi_flags(sk),
344 					    .uli_u = { .ports =
345 						       { .sport = inet->sport,
346 							 .dport = inet->dport } } };
347 
348 			/* If this fails, retransmit mechanism of transport layer will
349 			 * keep trying until route appears or the connection times
350 			 * itself out.
351 			 */
352 			security_sk_classify_flow(sk, &fl);
353 			if (ip_route_output_flow(sock_net(sk), &rt, &fl, sk, 0))
354 				goto no_route;
355 		}
356 		sk_setup_caps(sk, &rt->u.dst);
357 	}
358 	skb_dst_set(skb, dst_clone(&rt->u.dst));
359 
360 packet_routed:
361 	if (opt && opt->is_strictroute && rt->rt_dst != rt->rt_gateway)
362 		goto no_route;
363 
364 	/* OK, we know where to send it, allocate and build IP header. */
365 	skb_push(skb, sizeof(struct iphdr) + (opt ? opt->optlen : 0));
366 	skb_reset_network_header(skb);
367 	iph = ip_hdr(skb);
368 	*((__be16 *)iph) = htons((4 << 12) | (5 << 8) | (inet->tos & 0xff));
369 	if (ip_dont_fragment(sk, &rt->u.dst) && !ipfragok)
370 		iph->frag_off = htons(IP_DF);
371 	else
372 		iph->frag_off = 0;
373 	iph->ttl      = ip_select_ttl(inet, &rt->u.dst);
374 	iph->protocol = sk->sk_protocol;
375 	iph->saddr    = rt->rt_src;
376 	iph->daddr    = rt->rt_dst;
377 	/* Transport layer set skb->h.foo itself. */
378 
379 	if (opt && opt->optlen) {
380 		iph->ihl += opt->optlen >> 2;
381 		ip_options_build(skb, opt, inet->daddr, rt, 0);
382 	}
383 
384 	ip_select_ident_more(iph, &rt->u.dst, sk,
385 			     (skb_shinfo(skb)->gso_segs ?: 1) - 1);
386 
387 	skb->priority = sk->sk_priority;
388 	skb->mark = sk->sk_mark;
389 
390 	return ip_local_out(skb);
391 
392 no_route:
393 	IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);
394 	kfree_skb(skb);
395 	return -EHOSTUNREACH;
396 }
397 
398 
399 static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
400 {
401 	to->pkt_type = from->pkt_type;
402 	to->priority = from->priority;
403 	to->protocol = from->protocol;
404 	skb_dst_drop(to);
405 	skb_dst_set(to, dst_clone(skb_dst(from)));
406 	to->dev = from->dev;
407 	to->mark = from->mark;
408 
409 	/* Copy the flags to each fragment. */
410 	IPCB(to)->flags = IPCB(from)->flags;
411 
412 #ifdef CONFIG_NET_SCHED
413 	to->tc_index = from->tc_index;
414 #endif
415 	nf_copy(to, from);
416 #if defined(CONFIG_NETFILTER_XT_TARGET_TRACE) || \
417     defined(CONFIG_NETFILTER_XT_TARGET_TRACE_MODULE)
418 	to->nf_trace = from->nf_trace;
419 #endif
420 #if defined(CONFIG_IP_VS) || defined(CONFIG_IP_VS_MODULE)
421 	to->ipvs_property = from->ipvs_property;
422 #endif
423 	skb_copy_secmark(to, from);
424 }
425 
426 /*
427  *	This IP datagram is too large to be sent in one piece.  Break it up into
428  *	smaller pieces (each of size equal to IP header plus
429  *	a block of the data of the original IP data part) that will yet fit in a
430  *	single device frame, and queue such a frame for sending.
431  */
432 
433 int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
434 {
435 	struct iphdr *iph;
436 	int raw = 0;
437 	int ptr;
438 	struct net_device *dev;
439 	struct sk_buff *skb2;
440 	unsigned int mtu, hlen, left, len, ll_rs, pad;
441 	int offset;
442 	__be16 not_last_frag;
443 	struct rtable *rt = skb_rtable(skb);
444 	int err = 0;
445 
446 	dev = rt->u.dst.dev;
447 
448 	/*
449 	 *	Point into the IP datagram header.
450 	 */
451 
452 	iph = ip_hdr(skb);
453 
454 	if (unlikely((iph->frag_off & htons(IP_DF)) && !skb->local_df)) {
455 		IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
456 		icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
457 			  htonl(ip_skb_dst_mtu(skb)));
458 		kfree_skb(skb);
459 		return -EMSGSIZE;
460 	}
461 
462 	/*
463 	 *	Setup starting values.
464 	 */
465 
466 	hlen = iph->ihl * 4;
467 	mtu = dst_mtu(&rt->u.dst) - hlen;	/* Size of data space */
468 	IPCB(skb)->flags |= IPSKB_FRAG_COMPLETE;
469 
470 	/* When frag_list is given, use it. First, check its validity:
471 	 * some transformers could create wrong frag_list or break existing
472 	 * one, it is not prohibited. In this case fall back to copying.
473 	 *
474 	 * LATER: this step can be merged to real generation of fragments,
475 	 * we can switch to copy when see the first bad fragment.
476 	 */
477 	if (skb_has_frags(skb)) {
478 		struct sk_buff *frag;
479 		int first_len = skb_pagelen(skb);
480 		int truesizes = 0;
481 
482 		if (first_len - hlen > mtu ||
483 		    ((first_len - hlen) & 7) ||
484 		    (iph->frag_off & htons(IP_MF|IP_OFFSET)) ||
485 		    skb_cloned(skb))
486 			goto slow_path;
487 
488 		skb_walk_frags(skb, frag) {
489 			/* Correct geometry. */
490 			if (frag->len > mtu ||
491 			    ((frag->len & 7) && frag->next) ||
492 			    skb_headroom(frag) < hlen)
493 			    goto slow_path;
494 
495 			/* Partially cloned skb? */
496 			if (skb_shared(frag))
497 				goto slow_path;
498 
499 			BUG_ON(frag->sk);
500 			if (skb->sk) {
501 				frag->sk = skb->sk;
502 				frag->destructor = sock_wfree;
503 				truesizes += frag->truesize;
504 			}
505 		}
506 
507 		/* Everything is OK. Generate! */
508 
509 		err = 0;
510 		offset = 0;
511 		frag = skb_shinfo(skb)->frag_list;
512 		skb_frag_list_init(skb);
513 		skb->data_len = first_len - skb_headlen(skb);
514 		skb->truesize -= truesizes;
515 		skb->len = first_len;
516 		iph->tot_len = htons(first_len);
517 		iph->frag_off = htons(IP_MF);
518 		ip_send_check(iph);
519 
520 		for (;;) {
521 			/* Prepare header of the next frame,
522 			 * before previous one went down. */
523 			if (frag) {
524 				frag->ip_summed = CHECKSUM_NONE;
525 				skb_reset_transport_header(frag);
526 				__skb_push(frag, hlen);
527 				skb_reset_network_header(frag);
528 				memcpy(skb_network_header(frag), iph, hlen);
529 				iph = ip_hdr(frag);
530 				iph->tot_len = htons(frag->len);
531 				ip_copy_metadata(frag, skb);
532 				if (offset == 0)
533 					ip_options_fragment(frag);
534 				offset += skb->len - hlen;
535 				iph->frag_off = htons(offset>>3);
536 				if (frag->next != NULL)
537 					iph->frag_off |= htons(IP_MF);
538 				/* Ready, complete checksum */
539 				ip_send_check(iph);
540 			}
541 
542 			err = output(skb);
543 
544 			if (!err)
545 				IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGCREATES);
546 			if (err || !frag)
547 				break;
548 
549 			skb = frag;
550 			frag = skb->next;
551 			skb->next = NULL;
552 		}
553 
554 		if (err == 0) {
555 			IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGOKS);
556 			return 0;
557 		}
558 
559 		while (frag) {
560 			skb = frag->next;
561 			kfree_skb(frag);
562 			frag = skb;
563 		}
564 		IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
565 		return err;
566 	}
567 
568 slow_path:
569 	left = skb->len - hlen;		/* Space per frame */
570 	ptr = raw + hlen;		/* Where to start from */
571 
572 	/* for bridged IP traffic encapsulated inside f.e. a vlan header,
573 	 * we need to make room for the encapsulating header
574 	 */
575 	pad = nf_bridge_pad(skb);
576 	ll_rs = LL_RESERVED_SPACE_EXTRA(rt->u.dst.dev, pad);
577 	mtu -= pad;
578 
579 	/*
580 	 *	Fragment the datagram.
581 	 */
582 
583 	offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3;
584 	not_last_frag = iph->frag_off & htons(IP_MF);
585 
586 	/*
587 	 *	Keep copying data until we run out.
588 	 */
589 
590 	while (left > 0) {
591 		len = left;
592 		/* IF: it doesn't fit, use 'mtu' - the data space left */
593 		if (len > mtu)
594 			len = mtu;
595 		/* IF: we are not sending upto and including the packet end
596 		   then align the next start on an eight byte boundary */
597 		if (len < left)	{
598 			len &= ~7;
599 		}
600 		/*
601 		 *	Allocate buffer.
602 		 */
603 
604 		if ((skb2 = alloc_skb(len+hlen+ll_rs, GFP_ATOMIC)) == NULL) {
605 			NETDEBUG(KERN_INFO "IP: frag: no memory for new fragment!\n");
606 			err = -ENOMEM;
607 			goto fail;
608 		}
609 
610 		/*
611 		 *	Set up data on packet
612 		 */
613 
614 		ip_copy_metadata(skb2, skb);
615 		skb_reserve(skb2, ll_rs);
616 		skb_put(skb2, len + hlen);
617 		skb_reset_network_header(skb2);
618 		skb2->transport_header = skb2->network_header + hlen;
619 
620 		/*
621 		 *	Charge the memory for the fragment to any owner
622 		 *	it might possess
623 		 */
624 
625 		if (skb->sk)
626 			skb_set_owner_w(skb2, skb->sk);
627 
628 		/*
629 		 *	Copy the packet header into the new buffer.
630 		 */
631 
632 		skb_copy_from_linear_data(skb, skb_network_header(skb2), hlen);
633 
634 		/*
635 		 *	Copy a block of the IP datagram.
636 		 */
637 		if (skb_copy_bits(skb, ptr, skb_transport_header(skb2), len))
638 			BUG();
639 		left -= len;
640 
641 		/*
642 		 *	Fill in the new header fields.
643 		 */
644 		iph = ip_hdr(skb2);
645 		iph->frag_off = htons((offset >> 3));
646 
647 		/* ANK: dirty, but effective trick. Upgrade options only if
648 		 * the segment to be fragmented was THE FIRST (otherwise,
649 		 * options are already fixed) and make it ONCE
650 		 * on the initial skb, so that all the following fragments
651 		 * will inherit fixed options.
652 		 */
653 		if (offset == 0)
654 			ip_options_fragment(skb);
655 
656 		/*
657 		 *	Added AC : If we are fragmenting a fragment that's not the
658 		 *		   last fragment then keep MF on each bit
659 		 */
660 		if (left > 0 || not_last_frag)
661 			iph->frag_off |= htons(IP_MF);
662 		ptr += len;
663 		offset += len;
664 
665 		/*
666 		 *	Put this fragment into the sending queue.
667 		 */
668 		iph->tot_len = htons(len + hlen);
669 
670 		ip_send_check(iph);
671 
672 		err = output(skb2);
673 		if (err)
674 			goto fail;
675 
676 		IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGCREATES);
677 	}
678 	kfree_skb(skb);
679 	IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGOKS);
680 	return err;
681 
682 fail:
683 	kfree_skb(skb);
684 	IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
685 	return err;
686 }
687 
688 EXPORT_SYMBOL(ip_fragment);
689 
690 int
691 ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
692 {
693 	struct iovec *iov = from;
694 
695 	if (skb->ip_summed == CHECKSUM_PARTIAL) {
696 		if (memcpy_fromiovecend(to, iov, offset, len) < 0)
697 			return -EFAULT;
698 	} else {
699 		__wsum csum = 0;
700 		if (csum_partial_copy_fromiovecend(to, iov, offset, len, &csum) < 0)
701 			return -EFAULT;
702 		skb->csum = csum_block_add(skb->csum, csum, odd);
703 	}
704 	return 0;
705 }
706 
707 static inline __wsum
708 csum_page(struct page *page, int offset, int copy)
709 {
710 	char *kaddr;
711 	__wsum csum;
712 	kaddr = kmap(page);
713 	csum = csum_partial(kaddr + offset, copy, 0);
714 	kunmap(page);
715 	return csum;
716 }
717 
718 static inline int ip_ufo_append_data(struct sock *sk,
719 			int getfrag(void *from, char *to, int offset, int len,
720 			       int odd, struct sk_buff *skb),
721 			void *from, int length, int hh_len, int fragheaderlen,
722 			int transhdrlen, int mtu, unsigned int flags)
723 {
724 	struct sk_buff *skb;
725 	int err;
726 
727 	/* There is support for UDP fragmentation offload by network
728 	 * device, so create one single skb packet containing complete
729 	 * udp datagram
730 	 */
731 	if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL) {
732 		skb = sock_alloc_send_skb(sk,
733 			hh_len + fragheaderlen + transhdrlen + 20,
734 			(flags & MSG_DONTWAIT), &err);
735 
736 		if (skb == NULL)
737 			return err;
738 
739 		/* reserve space for Hardware header */
740 		skb_reserve(skb, hh_len);
741 
742 		/* create space for UDP/IP header */
743 		skb_put(skb, fragheaderlen + transhdrlen);
744 
745 		/* initialize network header pointer */
746 		skb_reset_network_header(skb);
747 
748 		/* initialize protocol header pointer */
749 		skb->transport_header = skb->network_header + fragheaderlen;
750 
751 		skb->ip_summed = CHECKSUM_PARTIAL;
752 		skb->csum = 0;
753 		sk->sk_sndmsg_off = 0;
754 
755 		/* specify the length of each IP datagram fragment */
756 		skb_shinfo(skb)->gso_size = mtu - fragheaderlen;
757 		skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
758 		__skb_queue_tail(&sk->sk_write_queue, skb);
759 	}
760 
761 	return skb_append_datato_frags(sk, skb, getfrag, from,
762 				       (length - transhdrlen));
763 }
764 
765 /*
766  *	ip_append_data() and ip_append_page() can make one large IP datagram
767  *	from many pieces of data. Each pieces will be holded on the socket
768  *	until ip_push_pending_frames() is called. Each piece can be a page
769  *	or non-page data.
770  *
771  *	Not only UDP, other transport protocols - e.g. raw sockets - can use
772  *	this interface potentially.
773  *
774  *	LATER: length must be adjusted by pad at tail, when it is required.
775  */
776 int ip_append_data(struct sock *sk,
777 		   int getfrag(void *from, char *to, int offset, int len,
778 			       int odd, struct sk_buff *skb),
779 		   void *from, int length, int transhdrlen,
780 		   struct ipcm_cookie *ipc, struct rtable **rtp,
781 		   unsigned int flags)
782 {
783 	struct inet_sock *inet = inet_sk(sk);
784 	struct sk_buff *skb;
785 
786 	struct ip_options *opt = NULL;
787 	int hh_len;
788 	int exthdrlen;
789 	int mtu;
790 	int copy;
791 	int err;
792 	int offset = 0;
793 	unsigned int maxfraglen, fragheaderlen;
794 	int csummode = CHECKSUM_NONE;
795 	struct rtable *rt;
796 
797 	if (flags&MSG_PROBE)
798 		return 0;
799 
800 	if (skb_queue_empty(&sk->sk_write_queue)) {
801 		/*
802 		 * setup for corking.
803 		 */
804 		opt = ipc->opt;
805 		if (opt) {
806 			if (inet->cork.opt == NULL) {
807 				inet->cork.opt = kmalloc(sizeof(struct ip_options) + 40, sk->sk_allocation);
808 				if (unlikely(inet->cork.opt == NULL))
809 					return -ENOBUFS;
810 			}
811 			memcpy(inet->cork.opt, opt, sizeof(struct ip_options)+opt->optlen);
812 			inet->cork.flags |= IPCORK_OPT;
813 			inet->cork.addr = ipc->addr;
814 		}
815 		rt = *rtp;
816 		if (unlikely(!rt))
817 			return -EFAULT;
818 		/*
819 		 * We steal reference to this route, caller should not release it
820 		 */
821 		*rtp = NULL;
822 		inet->cork.fragsize = mtu = inet->pmtudisc == IP_PMTUDISC_PROBE ?
823 					    rt->u.dst.dev->mtu :
824 					    dst_mtu(rt->u.dst.path);
825 		inet->cork.dst = &rt->u.dst;
826 		inet->cork.length = 0;
827 		sk->sk_sndmsg_page = NULL;
828 		sk->sk_sndmsg_off = 0;
829 		if ((exthdrlen = rt->u.dst.header_len) != 0) {
830 			length += exthdrlen;
831 			transhdrlen += exthdrlen;
832 		}
833 	} else {
834 		rt = (struct rtable *)inet->cork.dst;
835 		if (inet->cork.flags & IPCORK_OPT)
836 			opt = inet->cork.opt;
837 
838 		transhdrlen = 0;
839 		exthdrlen = 0;
840 		mtu = inet->cork.fragsize;
841 	}
842 	hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
843 
844 	fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
845 	maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
846 
847 	if (inet->cork.length + length > 0xFFFF - fragheaderlen) {
848 		ip_local_error(sk, EMSGSIZE, rt->rt_dst, inet->dport, mtu-exthdrlen);
849 		return -EMSGSIZE;
850 	}
851 
852 	/*
853 	 * transhdrlen > 0 means that this is the first fragment and we wish
854 	 * it won't be fragmented in the future.
855 	 */
856 	if (transhdrlen &&
857 	    length + fragheaderlen <= mtu &&
858 	    rt->u.dst.dev->features & NETIF_F_V4_CSUM &&
859 	    !exthdrlen)
860 		csummode = CHECKSUM_PARTIAL;
861 
862 	inet->cork.length += length;
863 	if (((length> mtu) || !skb_queue_empty(&sk->sk_write_queue)) &&
864 	    (sk->sk_protocol == IPPROTO_UDP) &&
865 	    (rt->u.dst.dev->features & NETIF_F_UFO)) {
866 		err = ip_ufo_append_data(sk, getfrag, from, length, hh_len,
867 					 fragheaderlen, transhdrlen, mtu,
868 					 flags);
869 		if (err)
870 			goto error;
871 		return 0;
872 	}
873 
874 	/* So, what's going on in the loop below?
875 	 *
876 	 * We use calculated fragment length to generate chained skb,
877 	 * each of segments is IP fragment ready for sending to network after
878 	 * adding appropriate IP header.
879 	 */
880 
881 	if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
882 		goto alloc_new_skb;
883 
884 	while (length > 0) {
885 		/* Check if the remaining data fits into current packet. */
886 		copy = mtu - skb->len;
887 		if (copy < length)
888 			copy = maxfraglen - skb->len;
889 		if (copy <= 0) {
890 			char *data;
891 			unsigned int datalen;
892 			unsigned int fraglen;
893 			unsigned int fraggap;
894 			unsigned int alloclen;
895 			struct sk_buff *skb_prev;
896 alloc_new_skb:
897 			skb_prev = skb;
898 			if (skb_prev)
899 				fraggap = skb_prev->len - maxfraglen;
900 			else
901 				fraggap = 0;
902 
903 			/*
904 			 * If remaining data exceeds the mtu,
905 			 * we know we need more fragment(s).
906 			 */
907 			datalen = length + fraggap;
908 			if (datalen > mtu - fragheaderlen)
909 				datalen = maxfraglen - fragheaderlen;
910 			fraglen = datalen + fragheaderlen;
911 
912 			if ((flags & MSG_MORE) &&
913 			    !(rt->u.dst.dev->features&NETIF_F_SG))
914 				alloclen = mtu;
915 			else
916 				alloclen = datalen + fragheaderlen;
917 
918 			/* The last fragment gets additional space at tail.
919 			 * Note, with MSG_MORE we overallocate on fragments,
920 			 * because we have no idea what fragment will be
921 			 * the last.
922 			 */
923 			if (datalen == length + fraggap)
924 				alloclen += rt->u.dst.trailer_len;
925 
926 			if (transhdrlen) {
927 				skb = sock_alloc_send_skb(sk,
928 						alloclen + hh_len + 15,
929 						(flags & MSG_DONTWAIT), &err);
930 			} else {
931 				skb = NULL;
932 				if (atomic_read(&sk->sk_wmem_alloc) <=
933 				    2 * sk->sk_sndbuf)
934 					skb = sock_wmalloc(sk,
935 							   alloclen + hh_len + 15, 1,
936 							   sk->sk_allocation);
937 				if (unlikely(skb == NULL))
938 					err = -ENOBUFS;
939 				else
940 					/* only the initial fragment is
941 					   time stamped */
942 					ipc->shtx.flags = 0;
943 			}
944 			if (skb == NULL)
945 				goto error;
946 
947 			/*
948 			 *	Fill in the control structures
949 			 */
950 			skb->ip_summed = csummode;
951 			skb->csum = 0;
952 			skb_reserve(skb, hh_len);
953 			*skb_tx(skb) = ipc->shtx;
954 
955 			/*
956 			 *	Find where to start putting bytes.
957 			 */
958 			data = skb_put(skb, fraglen);
959 			skb_set_network_header(skb, exthdrlen);
960 			skb->transport_header = (skb->network_header +
961 						 fragheaderlen);
962 			data += fragheaderlen;
963 
964 			if (fraggap) {
965 				skb->csum = skb_copy_and_csum_bits(
966 					skb_prev, maxfraglen,
967 					data + transhdrlen, fraggap, 0);
968 				skb_prev->csum = csum_sub(skb_prev->csum,
969 							  skb->csum);
970 				data += fraggap;
971 				pskb_trim_unique(skb_prev, maxfraglen);
972 			}
973 
974 			copy = datalen - transhdrlen - fraggap;
975 			if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
976 				err = -EFAULT;
977 				kfree_skb(skb);
978 				goto error;
979 			}
980 
981 			offset += copy;
982 			length -= datalen - fraggap;
983 			transhdrlen = 0;
984 			exthdrlen = 0;
985 			csummode = CHECKSUM_NONE;
986 
987 			/*
988 			 * Put the packet on the pending queue.
989 			 */
990 			__skb_queue_tail(&sk->sk_write_queue, skb);
991 			continue;
992 		}
993 
994 		if (copy > length)
995 			copy = length;
996 
997 		if (!(rt->u.dst.dev->features&NETIF_F_SG)) {
998 			unsigned int off;
999 
1000 			off = skb->len;
1001 			if (getfrag(from, skb_put(skb, copy),
1002 					offset, copy, off, skb) < 0) {
1003 				__skb_trim(skb, off);
1004 				err = -EFAULT;
1005 				goto error;
1006 			}
1007 		} else {
1008 			int i = skb_shinfo(skb)->nr_frags;
1009 			skb_frag_t *frag = &skb_shinfo(skb)->frags[i-1];
1010 			struct page *page = sk->sk_sndmsg_page;
1011 			int off = sk->sk_sndmsg_off;
1012 			unsigned int left;
1013 
1014 			if (page && (left = PAGE_SIZE - off) > 0) {
1015 				if (copy >= left)
1016 					copy = left;
1017 				if (page != frag->page) {
1018 					if (i == MAX_SKB_FRAGS) {
1019 						err = -EMSGSIZE;
1020 						goto error;
1021 					}
1022 					get_page(page);
1023 					skb_fill_page_desc(skb, i, page, sk->sk_sndmsg_off, 0);
1024 					frag = &skb_shinfo(skb)->frags[i];
1025 				}
1026 			} else if (i < MAX_SKB_FRAGS) {
1027 				if (copy > PAGE_SIZE)
1028 					copy = PAGE_SIZE;
1029 				page = alloc_pages(sk->sk_allocation, 0);
1030 				if (page == NULL)  {
1031 					err = -ENOMEM;
1032 					goto error;
1033 				}
1034 				sk->sk_sndmsg_page = page;
1035 				sk->sk_sndmsg_off = 0;
1036 
1037 				skb_fill_page_desc(skb, i, page, 0, 0);
1038 				frag = &skb_shinfo(skb)->frags[i];
1039 			} else {
1040 				err = -EMSGSIZE;
1041 				goto error;
1042 			}
1043 			if (getfrag(from, page_address(frag->page)+frag->page_offset+frag->size, offset, copy, skb->len, skb) < 0) {
1044 				err = -EFAULT;
1045 				goto error;
1046 			}
1047 			sk->sk_sndmsg_off += copy;
1048 			frag->size += copy;
1049 			skb->len += copy;
1050 			skb->data_len += copy;
1051 			skb->truesize += copy;
1052 			atomic_add(copy, &sk->sk_wmem_alloc);
1053 		}
1054 		offset += copy;
1055 		length -= copy;
1056 	}
1057 
1058 	return 0;
1059 
1060 error:
1061 	inet->cork.length -= length;
1062 	IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1063 	return err;
1064 }
1065 
1066 ssize_t	ip_append_page(struct sock *sk, struct page *page,
1067 		       int offset, size_t size, int flags)
1068 {
1069 	struct inet_sock *inet = inet_sk(sk);
1070 	struct sk_buff *skb;
1071 	struct rtable *rt;
1072 	struct ip_options *opt = NULL;
1073 	int hh_len;
1074 	int mtu;
1075 	int len;
1076 	int err;
1077 	unsigned int maxfraglen, fragheaderlen, fraggap;
1078 
1079 	if (inet->hdrincl)
1080 		return -EPERM;
1081 
1082 	if (flags&MSG_PROBE)
1083 		return 0;
1084 
1085 	if (skb_queue_empty(&sk->sk_write_queue))
1086 		return -EINVAL;
1087 
1088 	rt = (struct rtable *)inet->cork.dst;
1089 	if (inet->cork.flags & IPCORK_OPT)
1090 		opt = inet->cork.opt;
1091 
1092 	if (!(rt->u.dst.dev->features&NETIF_F_SG))
1093 		return -EOPNOTSUPP;
1094 
1095 	hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
1096 	mtu = inet->cork.fragsize;
1097 
1098 	fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
1099 	maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
1100 
1101 	if (inet->cork.length + size > 0xFFFF - fragheaderlen) {
1102 		ip_local_error(sk, EMSGSIZE, rt->rt_dst, inet->dport, mtu);
1103 		return -EMSGSIZE;
1104 	}
1105 
1106 	if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
1107 		return -EINVAL;
1108 
1109 	inet->cork.length += size;
1110 	if ((sk->sk_protocol == IPPROTO_UDP) &&
1111 	    (rt->u.dst.dev->features & NETIF_F_UFO)) {
1112 		skb_shinfo(skb)->gso_size = mtu - fragheaderlen;
1113 		skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
1114 	}
1115 
1116 
1117 	while (size > 0) {
1118 		int i;
1119 
1120 		if (skb_is_gso(skb))
1121 			len = size;
1122 		else {
1123 
1124 			/* Check if the remaining data fits into current packet. */
1125 			len = mtu - skb->len;
1126 			if (len < size)
1127 				len = maxfraglen - skb->len;
1128 		}
1129 		if (len <= 0) {
1130 			struct sk_buff *skb_prev;
1131 			int alloclen;
1132 
1133 			skb_prev = skb;
1134 			fraggap = skb_prev->len - maxfraglen;
1135 
1136 			alloclen = fragheaderlen + hh_len + fraggap + 15;
1137 			skb = sock_wmalloc(sk, alloclen, 1, sk->sk_allocation);
1138 			if (unlikely(!skb)) {
1139 				err = -ENOBUFS;
1140 				goto error;
1141 			}
1142 
1143 			/*
1144 			 *	Fill in the control structures
1145 			 */
1146 			skb->ip_summed = CHECKSUM_NONE;
1147 			skb->csum = 0;
1148 			skb_reserve(skb, hh_len);
1149 
1150 			/*
1151 			 *	Find where to start putting bytes.
1152 			 */
1153 			skb_put(skb, fragheaderlen + fraggap);
1154 			skb_reset_network_header(skb);
1155 			skb->transport_header = (skb->network_header +
1156 						 fragheaderlen);
1157 			if (fraggap) {
1158 				skb->csum = skb_copy_and_csum_bits(skb_prev,
1159 								   maxfraglen,
1160 						    skb_transport_header(skb),
1161 								   fraggap, 0);
1162 				skb_prev->csum = csum_sub(skb_prev->csum,
1163 							  skb->csum);
1164 				pskb_trim_unique(skb_prev, maxfraglen);
1165 			}
1166 
1167 			/*
1168 			 * Put the packet on the pending queue.
1169 			 */
1170 			__skb_queue_tail(&sk->sk_write_queue, skb);
1171 			continue;
1172 		}
1173 
1174 		i = skb_shinfo(skb)->nr_frags;
1175 		if (len > size)
1176 			len = size;
1177 		if (skb_can_coalesce(skb, i, page, offset)) {
1178 			skb_shinfo(skb)->frags[i-1].size += len;
1179 		} else if (i < MAX_SKB_FRAGS) {
1180 			get_page(page);
1181 			skb_fill_page_desc(skb, i, page, offset, len);
1182 		} else {
1183 			err = -EMSGSIZE;
1184 			goto error;
1185 		}
1186 
1187 		if (skb->ip_summed == CHECKSUM_NONE) {
1188 			__wsum csum;
1189 			csum = csum_page(page, offset, len);
1190 			skb->csum = csum_block_add(skb->csum, csum, skb->len);
1191 		}
1192 
1193 		skb->len += len;
1194 		skb->data_len += len;
1195 		skb->truesize += len;
1196 		atomic_add(len, &sk->sk_wmem_alloc);
1197 		offset += len;
1198 		size -= len;
1199 	}
1200 	return 0;
1201 
1202 error:
1203 	inet->cork.length -= size;
1204 	IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1205 	return err;
1206 }
1207 
1208 static void ip_cork_release(struct inet_sock *inet)
1209 {
1210 	inet->cork.flags &= ~IPCORK_OPT;
1211 	kfree(inet->cork.opt);
1212 	inet->cork.opt = NULL;
1213 	dst_release(inet->cork.dst);
1214 	inet->cork.dst = NULL;
1215 }
1216 
1217 /*
1218  *	Combined all pending IP fragments on the socket as one IP datagram
1219  *	and push them out.
1220  */
1221 int ip_push_pending_frames(struct sock *sk)
1222 {
1223 	struct sk_buff *skb, *tmp_skb;
1224 	struct sk_buff **tail_skb;
1225 	struct inet_sock *inet = inet_sk(sk);
1226 	struct net *net = sock_net(sk);
1227 	struct ip_options *opt = NULL;
1228 	struct rtable *rt = (struct rtable *)inet->cork.dst;
1229 	struct iphdr *iph;
1230 	__be16 df = 0;
1231 	__u8 ttl;
1232 	int err = 0;
1233 
1234 	if ((skb = __skb_dequeue(&sk->sk_write_queue)) == NULL)
1235 		goto out;
1236 	tail_skb = &(skb_shinfo(skb)->frag_list);
1237 
1238 	/* move skb->data to ip header from ext header */
1239 	if (skb->data < skb_network_header(skb))
1240 		__skb_pull(skb, skb_network_offset(skb));
1241 	while ((tmp_skb = __skb_dequeue(&sk->sk_write_queue)) != NULL) {
1242 		__skb_pull(tmp_skb, skb_network_header_len(skb));
1243 		*tail_skb = tmp_skb;
1244 		tail_skb = &(tmp_skb->next);
1245 		skb->len += tmp_skb->len;
1246 		skb->data_len += tmp_skb->len;
1247 		skb->truesize += tmp_skb->truesize;
1248 		tmp_skb->destructor = NULL;
1249 		tmp_skb->sk = NULL;
1250 	}
1251 
1252 	/* Unless user demanded real pmtu discovery (IP_PMTUDISC_DO), we allow
1253 	 * to fragment the frame generated here. No matter, what transforms
1254 	 * how transforms change size of the packet, it will come out.
1255 	 */
1256 	if (inet->pmtudisc < IP_PMTUDISC_DO)
1257 		skb->local_df = 1;
1258 
1259 	/* DF bit is set when we want to see DF on outgoing frames.
1260 	 * If local_df is set too, we still allow to fragment this frame
1261 	 * locally. */
1262 	if (inet->pmtudisc >= IP_PMTUDISC_DO ||
1263 	    (skb->len <= dst_mtu(&rt->u.dst) &&
1264 	     ip_dont_fragment(sk, &rt->u.dst)))
1265 		df = htons(IP_DF);
1266 
1267 	if (inet->cork.flags & IPCORK_OPT)
1268 		opt = inet->cork.opt;
1269 
1270 	if (rt->rt_type == RTN_MULTICAST)
1271 		ttl = inet->mc_ttl;
1272 	else
1273 		ttl = ip_select_ttl(inet, &rt->u.dst);
1274 
1275 	iph = (struct iphdr *)skb->data;
1276 	iph->version = 4;
1277 	iph->ihl = 5;
1278 	if (opt) {
1279 		iph->ihl += opt->optlen>>2;
1280 		ip_options_build(skb, opt, inet->cork.addr, rt, 0);
1281 	}
1282 	iph->tos = inet->tos;
1283 	iph->frag_off = df;
1284 	ip_select_ident(iph, &rt->u.dst, sk);
1285 	iph->ttl = ttl;
1286 	iph->protocol = sk->sk_protocol;
1287 	iph->saddr = rt->rt_src;
1288 	iph->daddr = rt->rt_dst;
1289 
1290 	skb->priority = sk->sk_priority;
1291 	skb->mark = sk->sk_mark;
1292 	/*
1293 	 * Steal rt from cork.dst to avoid a pair of atomic_inc/atomic_dec
1294 	 * on dst refcount
1295 	 */
1296 	inet->cork.dst = NULL;
1297 	skb_dst_set(skb, &rt->u.dst);
1298 
1299 	if (iph->protocol == IPPROTO_ICMP)
1300 		icmp_out_count(net, ((struct icmphdr *)
1301 			skb_transport_header(skb))->type);
1302 
1303 	/* Netfilter gets whole the not fragmented skb. */
1304 	err = ip_local_out(skb);
1305 	if (err) {
1306 		if (err > 0)
1307 			err = net_xmit_errno(err);
1308 		if (err)
1309 			goto error;
1310 	}
1311 
1312 out:
1313 	ip_cork_release(inet);
1314 	return err;
1315 
1316 error:
1317 	IP_INC_STATS(net, IPSTATS_MIB_OUTDISCARDS);
1318 	goto out;
1319 }
1320 
1321 /*
1322  *	Throw away all pending data on the socket.
1323  */
1324 void ip_flush_pending_frames(struct sock *sk)
1325 {
1326 	struct sk_buff *skb;
1327 
1328 	while ((skb = __skb_dequeue_tail(&sk->sk_write_queue)) != NULL)
1329 		kfree_skb(skb);
1330 
1331 	ip_cork_release(inet_sk(sk));
1332 }
1333 
1334 
1335 /*
1336  *	Fetch data from kernel space and fill in checksum if needed.
1337  */
1338 static int ip_reply_glue_bits(void *dptr, char *to, int offset,
1339 			      int len, int odd, struct sk_buff *skb)
1340 {
1341 	__wsum csum;
1342 
1343 	csum = csum_partial_copy_nocheck(dptr+offset, to, len, 0);
1344 	skb->csum = csum_block_add(skb->csum, csum, odd);
1345 	return 0;
1346 }
1347 
1348 /*
1349  *	Generic function to send a packet as reply to another packet.
1350  *	Used to send TCP resets so far. ICMP should use this function too.
1351  *
1352  *	Should run single threaded per socket because it uses the sock
1353  *     	structure to pass arguments.
1354  */
1355 void ip_send_reply(struct sock *sk, struct sk_buff *skb, struct ip_reply_arg *arg,
1356 		   unsigned int len)
1357 {
1358 	struct inet_sock *inet = inet_sk(sk);
1359 	struct {
1360 		struct ip_options	opt;
1361 		char			data[40];
1362 	} replyopts;
1363 	struct ipcm_cookie ipc;
1364 	__be32 daddr;
1365 	struct rtable *rt = skb_rtable(skb);
1366 
1367 	if (ip_options_echo(&replyopts.opt, skb))
1368 		return;
1369 
1370 	daddr = ipc.addr = rt->rt_src;
1371 	ipc.opt = NULL;
1372 	ipc.shtx.flags = 0;
1373 
1374 	if (replyopts.opt.optlen) {
1375 		ipc.opt = &replyopts.opt;
1376 
1377 		if (ipc.opt->srr)
1378 			daddr = replyopts.opt.faddr;
1379 	}
1380 
1381 	{
1382 		struct flowi fl = { .oif = arg->bound_dev_if,
1383 				    .nl_u = { .ip4_u =
1384 					      { .daddr = daddr,
1385 						.saddr = rt->rt_spec_dst,
1386 						.tos = RT_TOS(ip_hdr(skb)->tos) } },
1387 				    /* Not quite clean, but right. */
1388 				    .uli_u = { .ports =
1389 					       { .sport = tcp_hdr(skb)->dest,
1390 						 .dport = tcp_hdr(skb)->source } },
1391 				    .proto = sk->sk_protocol,
1392 				    .flags = ip_reply_arg_flowi_flags(arg) };
1393 		security_skb_classify_flow(skb, &fl);
1394 		if (ip_route_output_key(sock_net(sk), &rt, &fl))
1395 			return;
1396 	}
1397 
1398 	/* And let IP do all the hard work.
1399 
1400 	   This chunk is not reenterable, hence spinlock.
1401 	   Note that it uses the fact, that this function is called
1402 	   with locally disabled BH and that sk cannot be already spinlocked.
1403 	 */
1404 	bh_lock_sock(sk);
1405 	inet->tos = ip_hdr(skb)->tos;
1406 	sk->sk_priority = skb->priority;
1407 	sk->sk_protocol = ip_hdr(skb)->protocol;
1408 	sk->sk_bound_dev_if = arg->bound_dev_if;
1409 	ip_append_data(sk, ip_reply_glue_bits, arg->iov->iov_base, len, 0,
1410 		       &ipc, &rt, MSG_DONTWAIT);
1411 	if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {
1412 		if (arg->csumoffset >= 0)
1413 			*((__sum16 *)skb_transport_header(skb) +
1414 			  arg->csumoffset) = csum_fold(csum_add(skb->csum,
1415 								arg->csum));
1416 		skb->ip_summed = CHECKSUM_NONE;
1417 		ip_push_pending_frames(sk);
1418 	}
1419 
1420 	bh_unlock_sock(sk);
1421 
1422 	ip_rt_put(rt);
1423 }
1424 
1425 void __init ip_init(void)
1426 {
1427 	ip_rt_init();
1428 	inet_initpeers();
1429 
1430 #if defined(CONFIG_IP_MULTICAST) && defined(CONFIG_PROC_FS)
1431 	igmp_mc_proc_init();
1432 #endif
1433 }
1434 
1435 EXPORT_SYMBOL(ip_generic_getfrag);
1436 EXPORT_SYMBOL(ip_queue_xmit);
1437 EXPORT_SYMBOL(ip_send_check);
1438