xref: /linux/net/ipv4/ip_output.c (revision 1c4b5ecb7ea190fa3e9f9d6891e6c90b60e04f24)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * INET		An implementation of the TCP/IP protocol suite for the LINUX
4  *		operating system.  INET is implemented using the  BSD Socket
5  *		interface as the means of communication with the user level.
6  *
7  *		The Internet Protocol (IP) output module.
8  *
9  * Authors:	Ross Biro
10  *		Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
11  *		Donald Becker, <becker@super.org>
12  *		Alan Cox, <Alan.Cox@linux.org>
13  *		Richard Underwood
14  *		Stefan Becker, <stefanb@yello.ping.de>
15  *		Jorge Cwik, <jorge@laser.satlink.net>
16  *		Arnt Gulbrandsen, <agulbra@nvg.unit.no>
17  *		Hirokazu Takahashi, <taka@valinux.co.jp>
18  *
19  *	See ip_input.c for original log
20  *
21  *	Fixes:
22  *		Alan Cox	:	Missing nonblock feature in ip_build_xmit.
23  *		Mike Kilburn	:	htons() missing in ip_build_xmit.
24  *		Bradford Johnson:	Fix faulty handling of some frames when
25  *					no route is found.
26  *		Alexander Demenshin:	Missing sk/skb free in ip_queue_xmit
27  *					(in case if packet not accepted by
28  *					output firewall rules)
29  *		Mike McLagan	:	Routing by source
30  *		Alexey Kuznetsov:	use new route cache
31  *		Andi Kleen:		Fix broken PMTU recovery and remove
32  *					some redundant tests.
33  *	Vitaly E. Lavrov	:	Transparent proxy revived after year coma.
34  *		Andi Kleen	: 	Replace ip_reply with ip_send_reply.
35  *		Andi Kleen	:	Split fast and slow ip_build_xmit path
36  *					for decreased register pressure on x86
37  *					and more readability.
38  *		Marc Boucher	:	When call_out_firewall returns FW_QUEUE,
39  *					silently drop skb instead of failing with -EPERM.
40  *		Detlev Wengorz	:	Copy protocol for fragments.
41  *		Hirokazu Takahashi:	HW checksumming for outgoing UDP
42  *					datagrams.
43  *		Hirokazu Takahashi:	sendfile() on UDP works now.
44  */
45 
46 #include <linux/uaccess.h>
47 #include <linux/module.h>
48 #include <linux/types.h>
49 #include <linux/kernel.h>
50 #include <linux/mm.h>
51 #include <linux/string.h>
52 #include <linux/errno.h>
53 #include <linux/highmem.h>
54 #include <linux/slab.h>
55 
56 #include <linux/socket.h>
57 #include <linux/sockios.h>
58 #include <linux/in.h>
59 #include <linux/inet.h>
60 #include <linux/netdevice.h>
61 #include <linux/etherdevice.h>
62 #include <linux/proc_fs.h>
63 #include <linux/stat.h>
64 #include <linux/init.h>
65 
66 #include <net/snmp.h>
67 #include <net/ip.h>
68 #include <net/protocol.h>
69 #include <net/route.h>
70 #include <net/xfrm.h>
71 #include <linux/skbuff.h>
72 #include <net/sock.h>
73 #include <net/arp.h>
74 #include <net/icmp.h>
75 #include <net/checksum.h>
76 #include <net/inetpeer.h>
77 #include <net/inet_ecn.h>
78 #include <net/lwtunnel.h>
79 #include <linux/bpf-cgroup.h>
80 #include <linux/igmp.h>
81 #include <linux/netfilter_ipv4.h>
82 #include <linux/netfilter_bridge.h>
83 #include <linux/netlink.h>
84 #include <linux/tcp.h>
85 
86 static int
87 ip_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
88 	    unsigned int mtu,
89 	    int (*output)(struct net *, struct sock *, struct sk_buff *));
90 
91 /* Generate a checksum for an outgoing IP datagram. */
92 void ip_send_check(struct iphdr *iph)
93 {
94 	iph->check = 0;
95 	iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
96 }
97 EXPORT_SYMBOL(ip_send_check);
98 
99 int __ip_local_out(struct net *net, struct sock *sk, struct sk_buff *skb)
100 {
101 	struct iphdr *iph = ip_hdr(skb);
102 
103 	iph->tot_len = htons(skb->len);
104 	ip_send_check(iph);
105 
106 	/* if egress device is enslaved to an L3 master device pass the
107 	 * skb to its handler for processing
108 	 */
109 	skb = l3mdev_ip_out(sk, skb);
110 	if (unlikely(!skb))
111 		return 0;
112 
113 	skb->protocol = htons(ETH_P_IP);
114 
115 	return nf_hook(NFPROTO_IPV4, NF_INET_LOCAL_OUT,
116 		       net, sk, skb, NULL, skb_dst(skb)->dev,
117 		       dst_output);
118 }
119 
120 int ip_local_out(struct net *net, struct sock *sk, struct sk_buff *skb)
121 {
122 	int err;
123 
124 	err = __ip_local_out(net, sk, skb);
125 	if (likely(err == 1))
126 		err = dst_output(net, sk, skb);
127 
128 	return err;
129 }
130 EXPORT_SYMBOL_GPL(ip_local_out);
131 
132 static inline int ip_select_ttl(struct inet_sock *inet, struct dst_entry *dst)
133 {
134 	int ttl = inet->uc_ttl;
135 
136 	if (ttl < 0)
137 		ttl = ip4_dst_hoplimit(dst);
138 	return ttl;
139 }
140 
141 /*
142  *		Add an ip header to a skbuff and send it out.
143  *
144  */
145 int ip_build_and_send_pkt(struct sk_buff *skb, const struct sock *sk,
146 			  __be32 saddr, __be32 daddr, struct ip_options_rcu *opt,
147 			  u8 tos)
148 {
149 	struct inet_sock *inet = inet_sk(sk);
150 	struct rtable *rt = skb_rtable(skb);
151 	struct net *net = sock_net(sk);
152 	struct iphdr *iph;
153 
154 	/* Build the IP header. */
155 	skb_push(skb, sizeof(struct iphdr) + (opt ? opt->opt.optlen : 0));
156 	skb_reset_network_header(skb);
157 	iph = ip_hdr(skb);
158 	iph->version  = 4;
159 	iph->ihl      = 5;
160 	iph->tos      = tos;
161 	iph->ttl      = ip_select_ttl(inet, &rt->dst);
162 	iph->daddr    = (opt && opt->opt.srr ? opt->opt.faddr : daddr);
163 	iph->saddr    = saddr;
164 	iph->protocol = sk->sk_protocol;
165 	/* Do not bother generating IPID for small packets (eg SYNACK) */
166 	if (skb->len <= IPV4_MIN_MTU || ip_dont_fragment(sk, &rt->dst)) {
167 		iph->frag_off = htons(IP_DF);
168 		iph->id = 0;
169 	} else {
170 		iph->frag_off = 0;
171 		/* TCP packets here are SYNACK with fat IPv4/TCP options.
172 		 * Avoid using the hashed IP ident generator.
173 		 */
174 		if (sk->sk_protocol == IPPROTO_TCP)
175 			iph->id = (__force __be16)prandom_u32();
176 		else
177 			__ip_select_ident(net, iph, 1);
178 	}
179 
180 	if (opt && opt->opt.optlen) {
181 		iph->ihl += opt->opt.optlen>>2;
182 		ip_options_build(skb, &opt->opt, daddr, rt, 0);
183 	}
184 
185 	skb->priority = sk->sk_priority;
186 	if (!skb->mark)
187 		skb->mark = sk->sk_mark;
188 
189 	/* Send it out. */
190 	return ip_local_out(net, skb->sk, skb);
191 }
192 EXPORT_SYMBOL_GPL(ip_build_and_send_pkt);
193 
194 static int ip_finish_output2(struct net *net, struct sock *sk, struct sk_buff *skb)
195 {
196 	struct dst_entry *dst = skb_dst(skb);
197 	struct rtable *rt = (struct rtable *)dst;
198 	struct net_device *dev = dst->dev;
199 	unsigned int hh_len = LL_RESERVED_SPACE(dev);
200 	struct neighbour *neigh;
201 	bool is_v6gw = false;
202 
203 	if (rt->rt_type == RTN_MULTICAST) {
204 		IP_UPD_PO_STATS(net, IPSTATS_MIB_OUTMCAST, skb->len);
205 	} else if (rt->rt_type == RTN_BROADCAST)
206 		IP_UPD_PO_STATS(net, IPSTATS_MIB_OUTBCAST, skb->len);
207 
208 	if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) {
209 		skb = skb_expand_head(skb, hh_len);
210 		if (!skb)
211 			return -ENOMEM;
212 	}
213 
214 	if (lwtunnel_xmit_redirect(dst->lwtstate)) {
215 		int res = lwtunnel_xmit(skb);
216 
217 		if (res < 0 || res == LWTUNNEL_XMIT_DONE)
218 			return res;
219 	}
220 
221 	rcu_read_lock_bh();
222 	neigh = ip_neigh_for_gw(rt, skb, &is_v6gw);
223 	if (!IS_ERR(neigh)) {
224 		int res;
225 
226 		sock_confirm_neigh(skb, neigh);
227 		/* if crossing protocols, can not use the cached header */
228 		res = neigh_output(neigh, skb, is_v6gw);
229 		rcu_read_unlock_bh();
230 		return res;
231 	}
232 	rcu_read_unlock_bh();
233 
234 	net_dbg_ratelimited("%s: No header cache and no neighbour!\n",
235 			    __func__);
236 	kfree_skb(skb);
237 	return -EINVAL;
238 }
239 
240 static int ip_finish_output_gso(struct net *net, struct sock *sk,
241 				struct sk_buff *skb, unsigned int mtu)
242 {
243 	struct sk_buff *segs, *nskb;
244 	netdev_features_t features;
245 	int ret = 0;
246 
247 	/* common case: seglen is <= mtu
248 	 */
249 	if (skb_gso_validate_network_len(skb, mtu))
250 		return ip_finish_output2(net, sk, skb);
251 
252 	/* Slowpath -  GSO segment length exceeds the egress MTU.
253 	 *
254 	 * This can happen in several cases:
255 	 *  - Forwarding of a TCP GRO skb, when DF flag is not set.
256 	 *  - Forwarding of an skb that arrived on a virtualization interface
257 	 *    (virtio-net/vhost/tap) with TSO/GSO size set by other network
258 	 *    stack.
259 	 *  - Local GSO skb transmitted on an NETIF_F_TSO tunnel stacked over an
260 	 *    interface with a smaller MTU.
261 	 *  - Arriving GRO skb (or GSO skb in a virtualized environment) that is
262 	 *    bridged to a NETIF_F_TSO tunnel stacked over an interface with an
263 	 *    insufficient MTU.
264 	 */
265 	features = netif_skb_features(skb);
266 	BUILD_BUG_ON(sizeof(*IPCB(skb)) > SKB_GSO_CB_OFFSET);
267 	segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK);
268 	if (IS_ERR_OR_NULL(segs)) {
269 		kfree_skb(skb);
270 		return -ENOMEM;
271 	}
272 
273 	consume_skb(skb);
274 
275 	skb_list_walk_safe(segs, segs, nskb) {
276 		int err;
277 
278 		skb_mark_not_on_list(segs);
279 		err = ip_fragment(net, sk, segs, mtu, ip_finish_output2);
280 
281 		if (err && ret == 0)
282 			ret = err;
283 	}
284 
285 	return ret;
286 }
287 
288 static int __ip_finish_output(struct net *net, struct sock *sk, struct sk_buff *skb)
289 {
290 	unsigned int mtu;
291 
292 #if defined(CONFIG_NETFILTER) && defined(CONFIG_XFRM)
293 	/* Policy lookup after SNAT yielded a new policy */
294 	if (skb_dst(skb)->xfrm) {
295 		IPCB(skb)->flags |= IPSKB_REROUTED;
296 		return dst_output(net, sk, skb);
297 	}
298 #endif
299 	mtu = ip_skb_dst_mtu(sk, skb);
300 	if (skb_is_gso(skb))
301 		return ip_finish_output_gso(net, sk, skb, mtu);
302 
303 	if (skb->len > mtu || IPCB(skb)->frag_max_size)
304 		return ip_fragment(net, sk, skb, mtu, ip_finish_output2);
305 
306 	return ip_finish_output2(net, sk, skb);
307 }
308 
309 static int ip_finish_output(struct net *net, struct sock *sk, struct sk_buff *skb)
310 {
311 	int ret;
312 
313 	ret = BPF_CGROUP_RUN_PROG_INET_EGRESS(sk, skb);
314 	switch (ret) {
315 	case NET_XMIT_SUCCESS:
316 		return __ip_finish_output(net, sk, skb);
317 	case NET_XMIT_CN:
318 		return __ip_finish_output(net, sk, skb) ? : ret;
319 	default:
320 		kfree_skb(skb);
321 		return ret;
322 	}
323 }
324 
325 static int ip_mc_finish_output(struct net *net, struct sock *sk,
326 			       struct sk_buff *skb)
327 {
328 	struct rtable *new_rt;
329 	bool do_cn = false;
330 	int ret, err;
331 
332 	ret = BPF_CGROUP_RUN_PROG_INET_EGRESS(sk, skb);
333 	switch (ret) {
334 	case NET_XMIT_CN:
335 		do_cn = true;
336 		fallthrough;
337 	case NET_XMIT_SUCCESS:
338 		break;
339 	default:
340 		kfree_skb(skb);
341 		return ret;
342 	}
343 
344 	/* Reset rt_iif so that inet_iif() will return skb->skb_iif. Setting
345 	 * this to non-zero causes ipi_ifindex in in_pktinfo to be overwritten,
346 	 * see ipv4_pktinfo_prepare().
347 	 */
348 	new_rt = rt_dst_clone(net->loopback_dev, skb_rtable(skb));
349 	if (new_rt) {
350 		new_rt->rt_iif = 0;
351 		skb_dst_drop(skb);
352 		skb_dst_set(skb, &new_rt->dst);
353 	}
354 
355 	err = dev_loopback_xmit(net, sk, skb);
356 	return (do_cn && err) ? ret : err;
357 }
358 
359 int ip_mc_output(struct net *net, struct sock *sk, struct sk_buff *skb)
360 {
361 	struct rtable *rt = skb_rtable(skb);
362 	struct net_device *dev = rt->dst.dev;
363 
364 	/*
365 	 *	If the indicated interface is up and running, send the packet.
366 	 */
367 	IP_UPD_PO_STATS(net, IPSTATS_MIB_OUT, skb->len);
368 
369 	skb->dev = dev;
370 	skb->protocol = htons(ETH_P_IP);
371 
372 	/*
373 	 *	Multicasts are looped back for other local users
374 	 */
375 
376 	if (rt->rt_flags&RTCF_MULTICAST) {
377 		if (sk_mc_loop(sk)
378 #ifdef CONFIG_IP_MROUTE
379 		/* Small optimization: do not loopback not local frames,
380 		   which returned after forwarding; they will be  dropped
381 		   by ip_mr_input in any case.
382 		   Note, that local frames are looped back to be delivered
383 		   to local recipients.
384 
385 		   This check is duplicated in ip_mr_input at the moment.
386 		 */
387 		    &&
388 		    ((rt->rt_flags & RTCF_LOCAL) ||
389 		     !(IPCB(skb)->flags & IPSKB_FORWARDED))
390 #endif
391 		   ) {
392 			struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
393 			if (newskb)
394 				NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING,
395 					net, sk, newskb, NULL, newskb->dev,
396 					ip_mc_finish_output);
397 		}
398 
399 		/* Multicasts with ttl 0 must not go beyond the host */
400 
401 		if (ip_hdr(skb)->ttl == 0) {
402 			kfree_skb(skb);
403 			return 0;
404 		}
405 	}
406 
407 	if (rt->rt_flags&RTCF_BROADCAST) {
408 		struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
409 		if (newskb)
410 			NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING,
411 				net, sk, newskb, NULL, newskb->dev,
412 				ip_mc_finish_output);
413 	}
414 
415 	return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
416 			    net, sk, skb, NULL, skb->dev,
417 			    ip_finish_output,
418 			    !(IPCB(skb)->flags & IPSKB_REROUTED));
419 }
420 
421 int ip_output(struct net *net, struct sock *sk, struct sk_buff *skb)
422 {
423 	struct net_device *dev = skb_dst(skb)->dev, *indev = skb->dev;
424 
425 	IP_UPD_PO_STATS(net, IPSTATS_MIB_OUT, skb->len);
426 
427 	skb->dev = dev;
428 	skb->protocol = htons(ETH_P_IP);
429 
430 	return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
431 			    net, sk, skb, indev, dev,
432 			    ip_finish_output,
433 			    !(IPCB(skb)->flags & IPSKB_REROUTED));
434 }
435 EXPORT_SYMBOL(ip_output);
436 
437 /*
438  * copy saddr and daddr, possibly using 64bit load/stores
439  * Equivalent to :
440  *   iph->saddr = fl4->saddr;
441  *   iph->daddr = fl4->daddr;
442  */
443 static void ip_copy_addrs(struct iphdr *iph, const struct flowi4 *fl4)
444 {
445 	BUILD_BUG_ON(offsetof(typeof(*fl4), daddr) !=
446 		     offsetof(typeof(*fl4), saddr) + sizeof(fl4->saddr));
447 
448 	iph->saddr = fl4->saddr;
449 	iph->daddr = fl4->daddr;
450 }
451 
452 /* Note: skb->sk can be different from sk, in case of tunnels */
453 int __ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl,
454 		    __u8 tos)
455 {
456 	struct inet_sock *inet = inet_sk(sk);
457 	struct net *net = sock_net(sk);
458 	struct ip_options_rcu *inet_opt;
459 	struct flowi4 *fl4;
460 	struct rtable *rt;
461 	struct iphdr *iph;
462 	int res;
463 
464 	/* Skip all of this if the packet is already routed,
465 	 * f.e. by something like SCTP.
466 	 */
467 	rcu_read_lock();
468 	inet_opt = rcu_dereference(inet->inet_opt);
469 	fl4 = &fl->u.ip4;
470 	rt = skb_rtable(skb);
471 	if (rt)
472 		goto packet_routed;
473 
474 	/* Make sure we can route this packet. */
475 	rt = (struct rtable *)__sk_dst_check(sk, 0);
476 	if (!rt) {
477 		__be32 daddr;
478 
479 		/* Use correct destination address if we have options. */
480 		daddr = inet->inet_daddr;
481 		if (inet_opt && inet_opt->opt.srr)
482 			daddr = inet_opt->opt.faddr;
483 
484 		/* If this fails, retransmit mechanism of transport layer will
485 		 * keep trying until route appears or the connection times
486 		 * itself out.
487 		 */
488 		rt = ip_route_output_ports(net, fl4, sk,
489 					   daddr, inet->inet_saddr,
490 					   inet->inet_dport,
491 					   inet->inet_sport,
492 					   sk->sk_protocol,
493 					   RT_CONN_FLAGS_TOS(sk, tos),
494 					   sk->sk_bound_dev_if);
495 		if (IS_ERR(rt))
496 			goto no_route;
497 		sk_setup_caps(sk, &rt->dst);
498 	}
499 	skb_dst_set_noref(skb, &rt->dst);
500 
501 packet_routed:
502 	if (inet_opt && inet_opt->opt.is_strictroute && rt->rt_uses_gateway)
503 		goto no_route;
504 
505 	/* OK, we know where to send it, allocate and build IP header. */
506 	skb_push(skb, sizeof(struct iphdr) + (inet_opt ? inet_opt->opt.optlen : 0));
507 	skb_reset_network_header(skb);
508 	iph = ip_hdr(skb);
509 	*((__be16 *)iph) = htons((4 << 12) | (5 << 8) | (tos & 0xff));
510 	if (ip_dont_fragment(sk, &rt->dst) && !skb->ignore_df)
511 		iph->frag_off = htons(IP_DF);
512 	else
513 		iph->frag_off = 0;
514 	iph->ttl      = ip_select_ttl(inet, &rt->dst);
515 	iph->protocol = sk->sk_protocol;
516 	ip_copy_addrs(iph, fl4);
517 
518 	/* Transport layer set skb->h.foo itself. */
519 
520 	if (inet_opt && inet_opt->opt.optlen) {
521 		iph->ihl += inet_opt->opt.optlen >> 2;
522 		ip_options_build(skb, &inet_opt->opt, inet->inet_daddr, rt, 0);
523 	}
524 
525 	ip_select_ident_segs(net, skb, sk,
526 			     skb_shinfo(skb)->gso_segs ?: 1);
527 
528 	/* TODO : should we use skb->sk here instead of sk ? */
529 	skb->priority = sk->sk_priority;
530 	skb->mark = sk->sk_mark;
531 
532 	res = ip_local_out(net, sk, skb);
533 	rcu_read_unlock();
534 	return res;
535 
536 no_route:
537 	rcu_read_unlock();
538 	IP_INC_STATS(net, IPSTATS_MIB_OUTNOROUTES);
539 	kfree_skb(skb);
540 	return -EHOSTUNREACH;
541 }
542 EXPORT_SYMBOL(__ip_queue_xmit);
543 
544 int ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl)
545 {
546 	return __ip_queue_xmit(sk, skb, fl, inet_sk(sk)->tos);
547 }
548 EXPORT_SYMBOL(ip_queue_xmit);
549 
550 static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
551 {
552 	to->pkt_type = from->pkt_type;
553 	to->priority = from->priority;
554 	to->protocol = from->protocol;
555 	to->skb_iif = from->skb_iif;
556 	skb_dst_drop(to);
557 	skb_dst_copy(to, from);
558 	to->dev = from->dev;
559 	to->mark = from->mark;
560 
561 	skb_copy_hash(to, from);
562 
563 #ifdef CONFIG_NET_SCHED
564 	to->tc_index = from->tc_index;
565 #endif
566 	nf_copy(to, from);
567 	skb_ext_copy(to, from);
568 #if IS_ENABLED(CONFIG_IP_VS)
569 	to->ipvs_property = from->ipvs_property;
570 #endif
571 	skb_copy_secmark(to, from);
572 }
573 
574 static int ip_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
575 		       unsigned int mtu,
576 		       int (*output)(struct net *, struct sock *, struct sk_buff *))
577 {
578 	struct iphdr *iph = ip_hdr(skb);
579 
580 	if ((iph->frag_off & htons(IP_DF)) == 0)
581 		return ip_do_fragment(net, sk, skb, output);
582 
583 	if (unlikely(!skb->ignore_df ||
584 		     (IPCB(skb)->frag_max_size &&
585 		      IPCB(skb)->frag_max_size > mtu))) {
586 		IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
587 		icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
588 			  htonl(mtu));
589 		kfree_skb(skb);
590 		return -EMSGSIZE;
591 	}
592 
593 	return ip_do_fragment(net, sk, skb, output);
594 }
595 
596 void ip_fraglist_init(struct sk_buff *skb, struct iphdr *iph,
597 		      unsigned int hlen, struct ip_fraglist_iter *iter)
598 {
599 	unsigned int first_len = skb_pagelen(skb);
600 
601 	iter->frag = skb_shinfo(skb)->frag_list;
602 	skb_frag_list_init(skb);
603 
604 	iter->offset = 0;
605 	iter->iph = iph;
606 	iter->hlen = hlen;
607 
608 	skb->data_len = first_len - skb_headlen(skb);
609 	skb->len = first_len;
610 	iph->tot_len = htons(first_len);
611 	iph->frag_off = htons(IP_MF);
612 	ip_send_check(iph);
613 }
614 EXPORT_SYMBOL(ip_fraglist_init);
615 
616 void ip_fraglist_prepare(struct sk_buff *skb, struct ip_fraglist_iter *iter)
617 {
618 	unsigned int hlen = iter->hlen;
619 	struct iphdr *iph = iter->iph;
620 	struct sk_buff *frag;
621 
622 	frag = iter->frag;
623 	frag->ip_summed = CHECKSUM_NONE;
624 	skb_reset_transport_header(frag);
625 	__skb_push(frag, hlen);
626 	skb_reset_network_header(frag);
627 	memcpy(skb_network_header(frag), iph, hlen);
628 	iter->iph = ip_hdr(frag);
629 	iph = iter->iph;
630 	iph->tot_len = htons(frag->len);
631 	ip_copy_metadata(frag, skb);
632 	iter->offset += skb->len - hlen;
633 	iph->frag_off = htons(iter->offset >> 3);
634 	if (frag->next)
635 		iph->frag_off |= htons(IP_MF);
636 	/* Ready, complete checksum */
637 	ip_send_check(iph);
638 }
639 EXPORT_SYMBOL(ip_fraglist_prepare);
640 
641 void ip_frag_init(struct sk_buff *skb, unsigned int hlen,
642 		  unsigned int ll_rs, unsigned int mtu, bool DF,
643 		  struct ip_frag_state *state)
644 {
645 	struct iphdr *iph = ip_hdr(skb);
646 
647 	state->DF = DF;
648 	state->hlen = hlen;
649 	state->ll_rs = ll_rs;
650 	state->mtu = mtu;
651 
652 	state->left = skb->len - hlen;	/* Space per frame */
653 	state->ptr = hlen;		/* Where to start from */
654 
655 	state->offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3;
656 	state->not_last_frag = iph->frag_off & htons(IP_MF);
657 }
658 EXPORT_SYMBOL(ip_frag_init);
659 
660 static void ip_frag_ipcb(struct sk_buff *from, struct sk_buff *to,
661 			 bool first_frag)
662 {
663 	/* Copy the flags to each fragment. */
664 	IPCB(to)->flags = IPCB(from)->flags;
665 
666 	/* ANK: dirty, but effective trick. Upgrade options only if
667 	 * the segment to be fragmented was THE FIRST (otherwise,
668 	 * options are already fixed) and make it ONCE
669 	 * on the initial skb, so that all the following fragments
670 	 * will inherit fixed options.
671 	 */
672 	if (first_frag)
673 		ip_options_fragment(from);
674 }
675 
676 struct sk_buff *ip_frag_next(struct sk_buff *skb, struct ip_frag_state *state)
677 {
678 	unsigned int len = state->left;
679 	struct sk_buff *skb2;
680 	struct iphdr *iph;
681 
682 	/* IF: it doesn't fit, use 'mtu' - the data space left */
683 	if (len > state->mtu)
684 		len = state->mtu;
685 	/* IF: we are not sending up to and including the packet end
686 	   then align the next start on an eight byte boundary */
687 	if (len < state->left)	{
688 		len &= ~7;
689 	}
690 
691 	/* Allocate buffer */
692 	skb2 = alloc_skb(len + state->hlen + state->ll_rs, GFP_ATOMIC);
693 	if (!skb2)
694 		return ERR_PTR(-ENOMEM);
695 
696 	/*
697 	 *	Set up data on packet
698 	 */
699 
700 	ip_copy_metadata(skb2, skb);
701 	skb_reserve(skb2, state->ll_rs);
702 	skb_put(skb2, len + state->hlen);
703 	skb_reset_network_header(skb2);
704 	skb2->transport_header = skb2->network_header + state->hlen;
705 
706 	/*
707 	 *	Charge the memory for the fragment to any owner
708 	 *	it might possess
709 	 */
710 
711 	if (skb->sk)
712 		skb_set_owner_w(skb2, skb->sk);
713 
714 	/*
715 	 *	Copy the packet header into the new buffer.
716 	 */
717 
718 	skb_copy_from_linear_data(skb, skb_network_header(skb2), state->hlen);
719 
720 	/*
721 	 *	Copy a block of the IP datagram.
722 	 */
723 	if (skb_copy_bits(skb, state->ptr, skb_transport_header(skb2), len))
724 		BUG();
725 	state->left -= len;
726 
727 	/*
728 	 *	Fill in the new header fields.
729 	 */
730 	iph = ip_hdr(skb2);
731 	iph->frag_off = htons((state->offset >> 3));
732 	if (state->DF)
733 		iph->frag_off |= htons(IP_DF);
734 
735 	/*
736 	 *	Added AC : If we are fragmenting a fragment that's not the
737 	 *		   last fragment then keep MF on each bit
738 	 */
739 	if (state->left > 0 || state->not_last_frag)
740 		iph->frag_off |= htons(IP_MF);
741 	state->ptr += len;
742 	state->offset += len;
743 
744 	iph->tot_len = htons(len + state->hlen);
745 
746 	ip_send_check(iph);
747 
748 	return skb2;
749 }
750 EXPORT_SYMBOL(ip_frag_next);
751 
752 /*
753  *	This IP datagram is too large to be sent in one piece.  Break it up into
754  *	smaller pieces (each of size equal to IP header plus
755  *	a block of the data of the original IP data part) that will yet fit in a
756  *	single device frame, and queue such a frame for sending.
757  */
758 
759 int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
760 		   int (*output)(struct net *, struct sock *, struct sk_buff *))
761 {
762 	struct iphdr *iph;
763 	struct sk_buff *skb2;
764 	struct rtable *rt = skb_rtable(skb);
765 	unsigned int mtu, hlen, ll_rs;
766 	struct ip_fraglist_iter iter;
767 	ktime_t tstamp = skb->tstamp;
768 	struct ip_frag_state state;
769 	int err = 0;
770 
771 	/* for offloaded checksums cleanup checksum before fragmentation */
772 	if (skb->ip_summed == CHECKSUM_PARTIAL &&
773 	    (err = skb_checksum_help(skb)))
774 		goto fail;
775 
776 	/*
777 	 *	Point into the IP datagram header.
778 	 */
779 
780 	iph = ip_hdr(skb);
781 
782 	mtu = ip_skb_dst_mtu(sk, skb);
783 	if (IPCB(skb)->frag_max_size && IPCB(skb)->frag_max_size < mtu)
784 		mtu = IPCB(skb)->frag_max_size;
785 
786 	/*
787 	 *	Setup starting values.
788 	 */
789 
790 	hlen = iph->ihl * 4;
791 	mtu = mtu - hlen;	/* Size of data space */
792 	IPCB(skb)->flags |= IPSKB_FRAG_COMPLETE;
793 	ll_rs = LL_RESERVED_SPACE(rt->dst.dev);
794 
795 	/* When frag_list is given, use it. First, check its validity:
796 	 * some transformers could create wrong frag_list or break existing
797 	 * one, it is not prohibited. In this case fall back to copying.
798 	 *
799 	 * LATER: this step can be merged to real generation of fragments,
800 	 * we can switch to copy when see the first bad fragment.
801 	 */
802 	if (skb_has_frag_list(skb)) {
803 		struct sk_buff *frag, *frag2;
804 		unsigned int first_len = skb_pagelen(skb);
805 
806 		if (first_len - hlen > mtu ||
807 		    ((first_len - hlen) & 7) ||
808 		    ip_is_fragment(iph) ||
809 		    skb_cloned(skb) ||
810 		    skb_headroom(skb) < ll_rs)
811 			goto slow_path;
812 
813 		skb_walk_frags(skb, frag) {
814 			/* Correct geometry. */
815 			if (frag->len > mtu ||
816 			    ((frag->len & 7) && frag->next) ||
817 			    skb_headroom(frag) < hlen + ll_rs)
818 				goto slow_path_clean;
819 
820 			/* Partially cloned skb? */
821 			if (skb_shared(frag))
822 				goto slow_path_clean;
823 
824 			BUG_ON(frag->sk);
825 			if (skb->sk) {
826 				frag->sk = skb->sk;
827 				frag->destructor = sock_wfree;
828 			}
829 			skb->truesize -= frag->truesize;
830 		}
831 
832 		/* Everything is OK. Generate! */
833 		ip_fraglist_init(skb, iph, hlen, &iter);
834 
835 		for (;;) {
836 			/* Prepare header of the next frame,
837 			 * before previous one went down. */
838 			if (iter.frag) {
839 				bool first_frag = (iter.offset == 0);
840 
841 				IPCB(iter.frag)->flags = IPCB(skb)->flags;
842 				ip_fraglist_prepare(skb, &iter);
843 				if (first_frag && IPCB(skb)->opt.optlen) {
844 					/* ipcb->opt is not populated for frags
845 					 * coming from __ip_make_skb(),
846 					 * ip_options_fragment() needs optlen
847 					 */
848 					IPCB(iter.frag)->opt.optlen =
849 						IPCB(skb)->opt.optlen;
850 					ip_options_fragment(iter.frag);
851 					ip_send_check(iter.iph);
852 				}
853 			}
854 
855 			skb->tstamp = tstamp;
856 			err = output(net, sk, skb);
857 
858 			if (!err)
859 				IP_INC_STATS(net, IPSTATS_MIB_FRAGCREATES);
860 			if (err || !iter.frag)
861 				break;
862 
863 			skb = ip_fraglist_next(&iter);
864 		}
865 
866 		if (err == 0) {
867 			IP_INC_STATS(net, IPSTATS_MIB_FRAGOKS);
868 			return 0;
869 		}
870 
871 		kfree_skb_list(iter.frag);
872 
873 		IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
874 		return err;
875 
876 slow_path_clean:
877 		skb_walk_frags(skb, frag2) {
878 			if (frag2 == frag)
879 				break;
880 			frag2->sk = NULL;
881 			frag2->destructor = NULL;
882 			skb->truesize += frag2->truesize;
883 		}
884 	}
885 
886 slow_path:
887 	/*
888 	 *	Fragment the datagram.
889 	 */
890 
891 	ip_frag_init(skb, hlen, ll_rs, mtu, IPCB(skb)->flags & IPSKB_FRAG_PMTU,
892 		     &state);
893 
894 	/*
895 	 *	Keep copying data until we run out.
896 	 */
897 
898 	while (state.left > 0) {
899 		bool first_frag = (state.offset == 0);
900 
901 		skb2 = ip_frag_next(skb, &state);
902 		if (IS_ERR(skb2)) {
903 			err = PTR_ERR(skb2);
904 			goto fail;
905 		}
906 		ip_frag_ipcb(skb, skb2, first_frag);
907 
908 		/*
909 		 *	Put this fragment into the sending queue.
910 		 */
911 		skb2->tstamp = tstamp;
912 		err = output(net, sk, skb2);
913 		if (err)
914 			goto fail;
915 
916 		IP_INC_STATS(net, IPSTATS_MIB_FRAGCREATES);
917 	}
918 	consume_skb(skb);
919 	IP_INC_STATS(net, IPSTATS_MIB_FRAGOKS);
920 	return err;
921 
922 fail:
923 	kfree_skb(skb);
924 	IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
925 	return err;
926 }
927 EXPORT_SYMBOL(ip_do_fragment);
928 
929 int
930 ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
931 {
932 	struct msghdr *msg = from;
933 
934 	if (skb->ip_summed == CHECKSUM_PARTIAL) {
935 		if (!copy_from_iter_full(to, len, &msg->msg_iter))
936 			return -EFAULT;
937 	} else {
938 		__wsum csum = 0;
939 		if (!csum_and_copy_from_iter_full(to, len, &csum, &msg->msg_iter))
940 			return -EFAULT;
941 		skb->csum = csum_block_add(skb->csum, csum, odd);
942 	}
943 	return 0;
944 }
945 EXPORT_SYMBOL(ip_generic_getfrag);
946 
947 static inline __wsum
948 csum_page(struct page *page, int offset, int copy)
949 {
950 	char *kaddr;
951 	__wsum csum;
952 	kaddr = kmap(page);
953 	csum = csum_partial(kaddr + offset, copy, 0);
954 	kunmap(page);
955 	return csum;
956 }
957 
958 static int __ip_append_data(struct sock *sk,
959 			    struct flowi4 *fl4,
960 			    struct sk_buff_head *queue,
961 			    struct inet_cork *cork,
962 			    struct page_frag *pfrag,
963 			    int getfrag(void *from, char *to, int offset,
964 					int len, int odd, struct sk_buff *skb),
965 			    void *from, int length, int transhdrlen,
966 			    unsigned int flags)
967 {
968 	struct inet_sock *inet = inet_sk(sk);
969 	struct ubuf_info *uarg = NULL;
970 	struct sk_buff *skb;
971 
972 	struct ip_options *opt = cork->opt;
973 	int hh_len;
974 	int exthdrlen;
975 	int mtu;
976 	int copy;
977 	int err;
978 	int offset = 0;
979 	unsigned int maxfraglen, fragheaderlen, maxnonfragsize;
980 	int csummode = CHECKSUM_NONE;
981 	struct rtable *rt = (struct rtable *)cork->dst;
982 	unsigned int wmem_alloc_delta = 0;
983 	bool paged, extra_uref = false;
984 	u32 tskey = 0;
985 
986 	skb = skb_peek_tail(queue);
987 
988 	exthdrlen = !skb ? rt->dst.header_len : 0;
989 	mtu = cork->gso_size ? IP_MAX_MTU : cork->fragsize;
990 	paged = !!cork->gso_size;
991 
992 	if (cork->tx_flags & SKBTX_ANY_SW_TSTAMP &&
993 	    sk->sk_tsflags & SOF_TIMESTAMPING_OPT_ID)
994 		tskey = sk->sk_tskey++;
995 
996 	hh_len = LL_RESERVED_SPACE(rt->dst.dev);
997 
998 	fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
999 	maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
1000 	maxnonfragsize = ip_sk_ignore_df(sk) ? IP_MAX_MTU : mtu;
1001 
1002 	if (cork->length + length > maxnonfragsize - fragheaderlen) {
1003 		ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
1004 			       mtu - (opt ? opt->optlen : 0));
1005 		return -EMSGSIZE;
1006 	}
1007 
1008 	/*
1009 	 * transhdrlen > 0 means that this is the first fragment and we wish
1010 	 * it won't be fragmented in the future.
1011 	 */
1012 	if (transhdrlen &&
1013 	    length + fragheaderlen <= mtu &&
1014 	    rt->dst.dev->features & (NETIF_F_HW_CSUM | NETIF_F_IP_CSUM) &&
1015 	    (!(flags & MSG_MORE) || cork->gso_size) &&
1016 	    (!exthdrlen || (rt->dst.dev->features & NETIF_F_HW_ESP_TX_CSUM)))
1017 		csummode = CHECKSUM_PARTIAL;
1018 
1019 	if (flags & MSG_ZEROCOPY && length && sock_flag(sk, SOCK_ZEROCOPY)) {
1020 		uarg = msg_zerocopy_realloc(sk, length, skb_zcopy(skb));
1021 		if (!uarg)
1022 			return -ENOBUFS;
1023 		extra_uref = !skb_zcopy(skb);	/* only ref on new uarg */
1024 		if (rt->dst.dev->features & NETIF_F_SG &&
1025 		    csummode == CHECKSUM_PARTIAL) {
1026 			paged = true;
1027 		} else {
1028 			uarg->zerocopy = 0;
1029 			skb_zcopy_set(skb, uarg, &extra_uref);
1030 		}
1031 	}
1032 
1033 	cork->length += length;
1034 
1035 	/* So, what's going on in the loop below?
1036 	 *
1037 	 * We use calculated fragment length to generate chained skb,
1038 	 * each of segments is IP fragment ready for sending to network after
1039 	 * adding appropriate IP header.
1040 	 */
1041 
1042 	if (!skb)
1043 		goto alloc_new_skb;
1044 
1045 	while (length > 0) {
1046 		/* Check if the remaining data fits into current packet. */
1047 		copy = mtu - skb->len;
1048 		if (copy < length)
1049 			copy = maxfraglen - skb->len;
1050 		if (copy <= 0) {
1051 			char *data;
1052 			unsigned int datalen;
1053 			unsigned int fraglen;
1054 			unsigned int fraggap;
1055 			unsigned int alloclen, alloc_extra;
1056 			unsigned int pagedlen;
1057 			struct sk_buff *skb_prev;
1058 alloc_new_skb:
1059 			skb_prev = skb;
1060 			if (skb_prev)
1061 				fraggap = skb_prev->len - maxfraglen;
1062 			else
1063 				fraggap = 0;
1064 
1065 			/*
1066 			 * If remaining data exceeds the mtu,
1067 			 * we know we need more fragment(s).
1068 			 */
1069 			datalen = length + fraggap;
1070 			if (datalen > mtu - fragheaderlen)
1071 				datalen = maxfraglen - fragheaderlen;
1072 			fraglen = datalen + fragheaderlen;
1073 			pagedlen = 0;
1074 
1075 			alloc_extra = hh_len + 15;
1076 			alloc_extra += exthdrlen;
1077 
1078 			/* The last fragment gets additional space at tail.
1079 			 * Note, with MSG_MORE we overallocate on fragments,
1080 			 * because we have no idea what fragment will be
1081 			 * the last.
1082 			 */
1083 			if (datalen == length + fraggap)
1084 				alloc_extra += rt->dst.trailer_len;
1085 
1086 			if ((flags & MSG_MORE) &&
1087 			    !(rt->dst.dev->features&NETIF_F_SG))
1088 				alloclen = mtu;
1089 			else if (!paged &&
1090 				 (fraglen + alloc_extra < SKB_MAX_ALLOC ||
1091 				  !(rt->dst.dev->features & NETIF_F_SG)))
1092 				alloclen = fraglen;
1093 			else {
1094 				alloclen = min_t(int, fraglen, MAX_HEADER);
1095 				pagedlen = fraglen - alloclen;
1096 			}
1097 
1098 			alloclen += alloc_extra;
1099 
1100 			if (transhdrlen) {
1101 				skb = sock_alloc_send_skb(sk, alloclen,
1102 						(flags & MSG_DONTWAIT), &err);
1103 			} else {
1104 				skb = NULL;
1105 				if (refcount_read(&sk->sk_wmem_alloc) + wmem_alloc_delta <=
1106 				    2 * sk->sk_sndbuf)
1107 					skb = alloc_skb(alloclen,
1108 							sk->sk_allocation);
1109 				if (unlikely(!skb))
1110 					err = -ENOBUFS;
1111 			}
1112 			if (!skb)
1113 				goto error;
1114 
1115 			/*
1116 			 *	Fill in the control structures
1117 			 */
1118 			skb->ip_summed = csummode;
1119 			skb->csum = 0;
1120 			skb_reserve(skb, hh_len);
1121 
1122 			/*
1123 			 *	Find where to start putting bytes.
1124 			 */
1125 			data = skb_put(skb, fraglen + exthdrlen - pagedlen);
1126 			skb_set_network_header(skb, exthdrlen);
1127 			skb->transport_header = (skb->network_header +
1128 						 fragheaderlen);
1129 			data += fragheaderlen + exthdrlen;
1130 
1131 			if (fraggap) {
1132 				skb->csum = skb_copy_and_csum_bits(
1133 					skb_prev, maxfraglen,
1134 					data + transhdrlen, fraggap);
1135 				skb_prev->csum = csum_sub(skb_prev->csum,
1136 							  skb->csum);
1137 				data += fraggap;
1138 				pskb_trim_unique(skb_prev, maxfraglen);
1139 			}
1140 
1141 			copy = datalen - transhdrlen - fraggap - pagedlen;
1142 			if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) {
1143 				err = -EFAULT;
1144 				kfree_skb(skb);
1145 				goto error;
1146 			}
1147 
1148 			offset += copy;
1149 			length -= copy + transhdrlen;
1150 			transhdrlen = 0;
1151 			exthdrlen = 0;
1152 			csummode = CHECKSUM_NONE;
1153 
1154 			/* only the initial fragment is time stamped */
1155 			skb_shinfo(skb)->tx_flags = cork->tx_flags;
1156 			cork->tx_flags = 0;
1157 			skb_shinfo(skb)->tskey = tskey;
1158 			tskey = 0;
1159 			skb_zcopy_set(skb, uarg, &extra_uref);
1160 
1161 			if ((flags & MSG_CONFIRM) && !skb_prev)
1162 				skb_set_dst_pending_confirm(skb, 1);
1163 
1164 			/*
1165 			 * Put the packet on the pending queue.
1166 			 */
1167 			if (!skb->destructor) {
1168 				skb->destructor = sock_wfree;
1169 				skb->sk = sk;
1170 				wmem_alloc_delta += skb->truesize;
1171 			}
1172 			__skb_queue_tail(queue, skb);
1173 			continue;
1174 		}
1175 
1176 		if (copy > length)
1177 			copy = length;
1178 
1179 		if (!(rt->dst.dev->features&NETIF_F_SG) &&
1180 		    skb_tailroom(skb) >= copy) {
1181 			unsigned int off;
1182 
1183 			off = skb->len;
1184 			if (getfrag(from, skb_put(skb, copy),
1185 					offset, copy, off, skb) < 0) {
1186 				__skb_trim(skb, off);
1187 				err = -EFAULT;
1188 				goto error;
1189 			}
1190 		} else if (!uarg || !uarg->zerocopy) {
1191 			int i = skb_shinfo(skb)->nr_frags;
1192 
1193 			err = -ENOMEM;
1194 			if (!sk_page_frag_refill(sk, pfrag))
1195 				goto error;
1196 
1197 			if (!skb_can_coalesce(skb, i, pfrag->page,
1198 					      pfrag->offset)) {
1199 				err = -EMSGSIZE;
1200 				if (i == MAX_SKB_FRAGS)
1201 					goto error;
1202 
1203 				__skb_fill_page_desc(skb, i, pfrag->page,
1204 						     pfrag->offset, 0);
1205 				skb_shinfo(skb)->nr_frags = ++i;
1206 				get_page(pfrag->page);
1207 			}
1208 			copy = min_t(int, copy, pfrag->size - pfrag->offset);
1209 			if (getfrag(from,
1210 				    page_address(pfrag->page) + pfrag->offset,
1211 				    offset, copy, skb->len, skb) < 0)
1212 				goto error_efault;
1213 
1214 			pfrag->offset += copy;
1215 			skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
1216 			skb->len += copy;
1217 			skb->data_len += copy;
1218 			skb->truesize += copy;
1219 			wmem_alloc_delta += copy;
1220 		} else {
1221 			err = skb_zerocopy_iter_dgram(skb, from, copy);
1222 			if (err < 0)
1223 				goto error;
1224 		}
1225 		offset += copy;
1226 		length -= copy;
1227 	}
1228 
1229 	if (wmem_alloc_delta)
1230 		refcount_add(wmem_alloc_delta, &sk->sk_wmem_alloc);
1231 	return 0;
1232 
1233 error_efault:
1234 	err = -EFAULT;
1235 error:
1236 	net_zcopy_put_abort(uarg, extra_uref);
1237 	cork->length -= length;
1238 	IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1239 	refcount_add(wmem_alloc_delta, &sk->sk_wmem_alloc);
1240 	return err;
1241 }
1242 
1243 static int ip_setup_cork(struct sock *sk, struct inet_cork *cork,
1244 			 struct ipcm_cookie *ipc, struct rtable **rtp)
1245 {
1246 	struct ip_options_rcu *opt;
1247 	struct rtable *rt;
1248 
1249 	rt = *rtp;
1250 	if (unlikely(!rt))
1251 		return -EFAULT;
1252 
1253 	/*
1254 	 * setup for corking.
1255 	 */
1256 	opt = ipc->opt;
1257 	if (opt) {
1258 		if (!cork->opt) {
1259 			cork->opt = kmalloc(sizeof(struct ip_options) + 40,
1260 					    sk->sk_allocation);
1261 			if (unlikely(!cork->opt))
1262 				return -ENOBUFS;
1263 		}
1264 		memcpy(cork->opt, &opt->opt, sizeof(struct ip_options) + opt->opt.optlen);
1265 		cork->flags |= IPCORK_OPT;
1266 		cork->addr = ipc->addr;
1267 	}
1268 
1269 	cork->fragsize = ip_sk_use_pmtu(sk) ?
1270 			 dst_mtu(&rt->dst) : READ_ONCE(rt->dst.dev->mtu);
1271 
1272 	if (!inetdev_valid_mtu(cork->fragsize))
1273 		return -ENETUNREACH;
1274 
1275 	cork->gso_size = ipc->gso_size;
1276 
1277 	cork->dst = &rt->dst;
1278 	/* We stole this route, caller should not release it. */
1279 	*rtp = NULL;
1280 
1281 	cork->length = 0;
1282 	cork->ttl = ipc->ttl;
1283 	cork->tos = ipc->tos;
1284 	cork->mark = ipc->sockc.mark;
1285 	cork->priority = ipc->priority;
1286 	cork->transmit_time = ipc->sockc.transmit_time;
1287 	cork->tx_flags = 0;
1288 	sock_tx_timestamp(sk, ipc->sockc.tsflags, &cork->tx_flags);
1289 
1290 	return 0;
1291 }
1292 
1293 /*
1294  *	ip_append_data() and ip_append_page() can make one large IP datagram
1295  *	from many pieces of data. Each pieces will be holded on the socket
1296  *	until ip_push_pending_frames() is called. Each piece can be a page
1297  *	or non-page data.
1298  *
1299  *	Not only UDP, other transport protocols - e.g. raw sockets - can use
1300  *	this interface potentially.
1301  *
1302  *	LATER: length must be adjusted by pad at tail, when it is required.
1303  */
1304 int ip_append_data(struct sock *sk, struct flowi4 *fl4,
1305 		   int getfrag(void *from, char *to, int offset, int len,
1306 			       int odd, struct sk_buff *skb),
1307 		   void *from, int length, int transhdrlen,
1308 		   struct ipcm_cookie *ipc, struct rtable **rtp,
1309 		   unsigned int flags)
1310 {
1311 	struct inet_sock *inet = inet_sk(sk);
1312 	int err;
1313 
1314 	if (flags&MSG_PROBE)
1315 		return 0;
1316 
1317 	if (skb_queue_empty(&sk->sk_write_queue)) {
1318 		err = ip_setup_cork(sk, &inet->cork.base, ipc, rtp);
1319 		if (err)
1320 			return err;
1321 	} else {
1322 		transhdrlen = 0;
1323 	}
1324 
1325 	return __ip_append_data(sk, fl4, &sk->sk_write_queue, &inet->cork.base,
1326 				sk_page_frag(sk), getfrag,
1327 				from, length, transhdrlen, flags);
1328 }
1329 
1330 ssize_t	ip_append_page(struct sock *sk, struct flowi4 *fl4, struct page *page,
1331 		       int offset, size_t size, int flags)
1332 {
1333 	struct inet_sock *inet = inet_sk(sk);
1334 	struct sk_buff *skb;
1335 	struct rtable *rt;
1336 	struct ip_options *opt = NULL;
1337 	struct inet_cork *cork;
1338 	int hh_len;
1339 	int mtu;
1340 	int len;
1341 	int err;
1342 	unsigned int maxfraglen, fragheaderlen, fraggap, maxnonfragsize;
1343 
1344 	if (inet->hdrincl)
1345 		return -EPERM;
1346 
1347 	if (flags&MSG_PROBE)
1348 		return 0;
1349 
1350 	if (skb_queue_empty(&sk->sk_write_queue))
1351 		return -EINVAL;
1352 
1353 	cork = &inet->cork.base;
1354 	rt = (struct rtable *)cork->dst;
1355 	if (cork->flags & IPCORK_OPT)
1356 		opt = cork->opt;
1357 
1358 	if (!(rt->dst.dev->features & NETIF_F_SG))
1359 		return -EOPNOTSUPP;
1360 
1361 	hh_len = LL_RESERVED_SPACE(rt->dst.dev);
1362 	mtu = cork->gso_size ? IP_MAX_MTU : cork->fragsize;
1363 
1364 	fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
1365 	maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
1366 	maxnonfragsize = ip_sk_ignore_df(sk) ? 0xFFFF : mtu;
1367 
1368 	if (cork->length + size > maxnonfragsize - fragheaderlen) {
1369 		ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
1370 			       mtu - (opt ? opt->optlen : 0));
1371 		return -EMSGSIZE;
1372 	}
1373 
1374 	skb = skb_peek_tail(&sk->sk_write_queue);
1375 	if (!skb)
1376 		return -EINVAL;
1377 
1378 	cork->length += size;
1379 
1380 	while (size > 0) {
1381 		/* Check if the remaining data fits into current packet. */
1382 		len = mtu - skb->len;
1383 		if (len < size)
1384 			len = maxfraglen - skb->len;
1385 
1386 		if (len <= 0) {
1387 			struct sk_buff *skb_prev;
1388 			int alloclen;
1389 
1390 			skb_prev = skb;
1391 			fraggap = skb_prev->len - maxfraglen;
1392 
1393 			alloclen = fragheaderlen + hh_len + fraggap + 15;
1394 			skb = sock_wmalloc(sk, alloclen, 1, sk->sk_allocation);
1395 			if (unlikely(!skb)) {
1396 				err = -ENOBUFS;
1397 				goto error;
1398 			}
1399 
1400 			/*
1401 			 *	Fill in the control structures
1402 			 */
1403 			skb->ip_summed = CHECKSUM_NONE;
1404 			skb->csum = 0;
1405 			skb_reserve(skb, hh_len);
1406 
1407 			/*
1408 			 *	Find where to start putting bytes.
1409 			 */
1410 			skb_put(skb, fragheaderlen + fraggap);
1411 			skb_reset_network_header(skb);
1412 			skb->transport_header = (skb->network_header +
1413 						 fragheaderlen);
1414 			if (fraggap) {
1415 				skb->csum = skb_copy_and_csum_bits(skb_prev,
1416 								   maxfraglen,
1417 						    skb_transport_header(skb),
1418 								   fraggap);
1419 				skb_prev->csum = csum_sub(skb_prev->csum,
1420 							  skb->csum);
1421 				pskb_trim_unique(skb_prev, maxfraglen);
1422 			}
1423 
1424 			/*
1425 			 * Put the packet on the pending queue.
1426 			 */
1427 			__skb_queue_tail(&sk->sk_write_queue, skb);
1428 			continue;
1429 		}
1430 
1431 		if (len > size)
1432 			len = size;
1433 
1434 		if (skb_append_pagefrags(skb, page, offset, len)) {
1435 			err = -EMSGSIZE;
1436 			goto error;
1437 		}
1438 
1439 		if (skb->ip_summed == CHECKSUM_NONE) {
1440 			__wsum csum;
1441 			csum = csum_page(page, offset, len);
1442 			skb->csum = csum_block_add(skb->csum, csum, skb->len);
1443 		}
1444 
1445 		skb->len += len;
1446 		skb->data_len += len;
1447 		skb->truesize += len;
1448 		refcount_add(len, &sk->sk_wmem_alloc);
1449 		offset += len;
1450 		size -= len;
1451 	}
1452 	return 0;
1453 
1454 error:
1455 	cork->length -= size;
1456 	IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
1457 	return err;
1458 }
1459 
1460 static void ip_cork_release(struct inet_cork *cork)
1461 {
1462 	cork->flags &= ~IPCORK_OPT;
1463 	kfree(cork->opt);
1464 	cork->opt = NULL;
1465 	dst_release(cork->dst);
1466 	cork->dst = NULL;
1467 }
1468 
1469 /*
1470  *	Combined all pending IP fragments on the socket as one IP datagram
1471  *	and push them out.
1472  */
1473 struct sk_buff *__ip_make_skb(struct sock *sk,
1474 			      struct flowi4 *fl4,
1475 			      struct sk_buff_head *queue,
1476 			      struct inet_cork *cork)
1477 {
1478 	struct sk_buff *skb, *tmp_skb;
1479 	struct sk_buff **tail_skb;
1480 	struct inet_sock *inet = inet_sk(sk);
1481 	struct net *net = sock_net(sk);
1482 	struct ip_options *opt = NULL;
1483 	struct rtable *rt = (struct rtable *)cork->dst;
1484 	struct iphdr *iph;
1485 	__be16 df = 0;
1486 	__u8 ttl;
1487 
1488 	skb = __skb_dequeue(queue);
1489 	if (!skb)
1490 		goto out;
1491 	tail_skb = &(skb_shinfo(skb)->frag_list);
1492 
1493 	/* move skb->data to ip header from ext header */
1494 	if (skb->data < skb_network_header(skb))
1495 		__skb_pull(skb, skb_network_offset(skb));
1496 	while ((tmp_skb = __skb_dequeue(queue)) != NULL) {
1497 		__skb_pull(tmp_skb, skb_network_header_len(skb));
1498 		*tail_skb = tmp_skb;
1499 		tail_skb = &(tmp_skb->next);
1500 		skb->len += tmp_skb->len;
1501 		skb->data_len += tmp_skb->len;
1502 		skb->truesize += tmp_skb->truesize;
1503 		tmp_skb->destructor = NULL;
1504 		tmp_skb->sk = NULL;
1505 	}
1506 
1507 	/* Unless user demanded real pmtu discovery (IP_PMTUDISC_DO), we allow
1508 	 * to fragment the frame generated here. No matter, what transforms
1509 	 * how transforms change size of the packet, it will come out.
1510 	 */
1511 	skb->ignore_df = ip_sk_ignore_df(sk);
1512 
1513 	/* DF bit is set when we want to see DF on outgoing frames.
1514 	 * If ignore_df is set too, we still allow to fragment this frame
1515 	 * locally. */
1516 	if (inet->pmtudisc == IP_PMTUDISC_DO ||
1517 	    inet->pmtudisc == IP_PMTUDISC_PROBE ||
1518 	    (skb->len <= dst_mtu(&rt->dst) &&
1519 	     ip_dont_fragment(sk, &rt->dst)))
1520 		df = htons(IP_DF);
1521 
1522 	if (cork->flags & IPCORK_OPT)
1523 		opt = cork->opt;
1524 
1525 	if (cork->ttl != 0)
1526 		ttl = cork->ttl;
1527 	else if (rt->rt_type == RTN_MULTICAST)
1528 		ttl = inet->mc_ttl;
1529 	else
1530 		ttl = ip_select_ttl(inet, &rt->dst);
1531 
1532 	iph = ip_hdr(skb);
1533 	iph->version = 4;
1534 	iph->ihl = 5;
1535 	iph->tos = (cork->tos != -1) ? cork->tos : inet->tos;
1536 	iph->frag_off = df;
1537 	iph->ttl = ttl;
1538 	iph->protocol = sk->sk_protocol;
1539 	ip_copy_addrs(iph, fl4);
1540 	ip_select_ident(net, skb, sk);
1541 
1542 	if (opt) {
1543 		iph->ihl += opt->optlen >> 2;
1544 		ip_options_build(skb, opt, cork->addr, rt, 0);
1545 	}
1546 
1547 	skb->priority = (cork->tos != -1) ? cork->priority: sk->sk_priority;
1548 	skb->mark = cork->mark;
1549 	skb->tstamp = cork->transmit_time;
1550 	/*
1551 	 * Steal rt from cork.dst to avoid a pair of atomic_inc/atomic_dec
1552 	 * on dst refcount
1553 	 */
1554 	cork->dst = NULL;
1555 	skb_dst_set(skb, &rt->dst);
1556 
1557 	if (iph->protocol == IPPROTO_ICMP)
1558 		icmp_out_count(net, ((struct icmphdr *)
1559 			skb_transport_header(skb))->type);
1560 
1561 	ip_cork_release(cork);
1562 out:
1563 	return skb;
1564 }
1565 
1566 int ip_send_skb(struct net *net, struct sk_buff *skb)
1567 {
1568 	int err;
1569 
1570 	err = ip_local_out(net, skb->sk, skb);
1571 	if (err) {
1572 		if (err > 0)
1573 			err = net_xmit_errno(err);
1574 		if (err)
1575 			IP_INC_STATS(net, IPSTATS_MIB_OUTDISCARDS);
1576 	}
1577 
1578 	return err;
1579 }
1580 
1581 int ip_push_pending_frames(struct sock *sk, struct flowi4 *fl4)
1582 {
1583 	struct sk_buff *skb;
1584 
1585 	skb = ip_finish_skb(sk, fl4);
1586 	if (!skb)
1587 		return 0;
1588 
1589 	/* Netfilter gets whole the not fragmented skb. */
1590 	return ip_send_skb(sock_net(sk), skb);
1591 }
1592 
1593 /*
1594  *	Throw away all pending data on the socket.
1595  */
1596 static void __ip_flush_pending_frames(struct sock *sk,
1597 				      struct sk_buff_head *queue,
1598 				      struct inet_cork *cork)
1599 {
1600 	struct sk_buff *skb;
1601 
1602 	while ((skb = __skb_dequeue_tail(queue)) != NULL)
1603 		kfree_skb(skb);
1604 
1605 	ip_cork_release(cork);
1606 }
1607 
1608 void ip_flush_pending_frames(struct sock *sk)
1609 {
1610 	__ip_flush_pending_frames(sk, &sk->sk_write_queue, &inet_sk(sk)->cork.base);
1611 }
1612 
1613 struct sk_buff *ip_make_skb(struct sock *sk,
1614 			    struct flowi4 *fl4,
1615 			    int getfrag(void *from, char *to, int offset,
1616 					int len, int odd, struct sk_buff *skb),
1617 			    void *from, int length, int transhdrlen,
1618 			    struct ipcm_cookie *ipc, struct rtable **rtp,
1619 			    struct inet_cork *cork, unsigned int flags)
1620 {
1621 	struct sk_buff_head queue;
1622 	int err;
1623 
1624 	if (flags & MSG_PROBE)
1625 		return NULL;
1626 
1627 	__skb_queue_head_init(&queue);
1628 
1629 	cork->flags = 0;
1630 	cork->addr = 0;
1631 	cork->opt = NULL;
1632 	err = ip_setup_cork(sk, cork, ipc, rtp);
1633 	if (err)
1634 		return ERR_PTR(err);
1635 
1636 	err = __ip_append_data(sk, fl4, &queue, cork,
1637 			       &current->task_frag, getfrag,
1638 			       from, length, transhdrlen, flags);
1639 	if (err) {
1640 		__ip_flush_pending_frames(sk, &queue, cork);
1641 		return ERR_PTR(err);
1642 	}
1643 
1644 	return __ip_make_skb(sk, fl4, &queue, cork);
1645 }
1646 
1647 /*
1648  *	Fetch data from kernel space and fill in checksum if needed.
1649  */
1650 static int ip_reply_glue_bits(void *dptr, char *to, int offset,
1651 			      int len, int odd, struct sk_buff *skb)
1652 {
1653 	__wsum csum;
1654 
1655 	csum = csum_partial_copy_nocheck(dptr+offset, to, len);
1656 	skb->csum = csum_block_add(skb->csum, csum, odd);
1657 	return 0;
1658 }
1659 
1660 /*
1661  *	Generic function to send a packet as reply to another packet.
1662  *	Used to send some TCP resets/acks so far.
1663  */
1664 void ip_send_unicast_reply(struct sock *sk, struct sk_buff *skb,
1665 			   const struct ip_options *sopt,
1666 			   __be32 daddr, __be32 saddr,
1667 			   const struct ip_reply_arg *arg,
1668 			   unsigned int len, u64 transmit_time)
1669 {
1670 	struct ip_options_data replyopts;
1671 	struct ipcm_cookie ipc;
1672 	struct flowi4 fl4;
1673 	struct rtable *rt = skb_rtable(skb);
1674 	struct net *net = sock_net(sk);
1675 	struct sk_buff *nskb;
1676 	int err;
1677 	int oif;
1678 
1679 	if (__ip_options_echo(net, &replyopts.opt.opt, skb, sopt))
1680 		return;
1681 
1682 	ipcm_init(&ipc);
1683 	ipc.addr = daddr;
1684 	ipc.sockc.transmit_time = transmit_time;
1685 
1686 	if (replyopts.opt.opt.optlen) {
1687 		ipc.opt = &replyopts.opt;
1688 
1689 		if (replyopts.opt.opt.srr)
1690 			daddr = replyopts.opt.opt.faddr;
1691 	}
1692 
1693 	oif = arg->bound_dev_if;
1694 	if (!oif && netif_index_is_l3_master(net, skb->skb_iif))
1695 		oif = skb->skb_iif;
1696 
1697 	flowi4_init_output(&fl4, oif,
1698 			   IP4_REPLY_MARK(net, skb->mark) ?: sk->sk_mark,
1699 			   RT_TOS(arg->tos),
1700 			   RT_SCOPE_UNIVERSE, ip_hdr(skb)->protocol,
1701 			   ip_reply_arg_flowi_flags(arg),
1702 			   daddr, saddr,
1703 			   tcp_hdr(skb)->source, tcp_hdr(skb)->dest,
1704 			   arg->uid);
1705 	security_skb_classify_flow(skb, flowi4_to_flowi_common(&fl4));
1706 	rt = ip_route_output_key(net, &fl4);
1707 	if (IS_ERR(rt))
1708 		return;
1709 
1710 	inet_sk(sk)->tos = arg->tos & ~INET_ECN_MASK;
1711 
1712 	sk->sk_protocol = ip_hdr(skb)->protocol;
1713 	sk->sk_bound_dev_if = arg->bound_dev_if;
1714 	sk->sk_sndbuf = sysctl_wmem_default;
1715 	ipc.sockc.mark = fl4.flowi4_mark;
1716 	err = ip_append_data(sk, &fl4, ip_reply_glue_bits, arg->iov->iov_base,
1717 			     len, 0, &ipc, &rt, MSG_DONTWAIT);
1718 	if (unlikely(err)) {
1719 		ip_flush_pending_frames(sk);
1720 		goto out;
1721 	}
1722 
1723 	nskb = skb_peek(&sk->sk_write_queue);
1724 	if (nskb) {
1725 		if (arg->csumoffset >= 0)
1726 			*((__sum16 *)skb_transport_header(nskb) +
1727 			  arg->csumoffset) = csum_fold(csum_add(nskb->csum,
1728 								arg->csum));
1729 		nskb->ip_summed = CHECKSUM_NONE;
1730 		ip_push_pending_frames(sk, &fl4);
1731 	}
1732 out:
1733 	ip_rt_put(rt);
1734 }
1735 
1736 void __init ip_init(void)
1737 {
1738 	ip_rt_init();
1739 	inet_initpeers();
1740 
1741 #if defined(CONFIG_IP_MULTICAST)
1742 	igmp_mc_init();
1743 #endif
1744 }
1745