ip_input.c

  1// SPDX-License-Identifier: GPL-2.0-or-later
  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) 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@lxorguk.ukuu.org.uk>
 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 *
 18 * Fixes:
 19 *		Alan Cox	:	Commented a couple of minor bits of surplus code
 20 *		Alan Cox	:	Undefining IP_FORWARD doesn't include the code
 21 *					(just stops a compiler warning).
 22 *		Alan Cox	:	Frames with >=MAX_ROUTE record routes, strict routes or loose routes
 23 *					are junked rather than corrupting things.
 24 *		Alan Cox	:	Frames to bad broadcast subnets are dumped
 25 *					We used to process them non broadcast and
 26 *					boy could that cause havoc.
 27 *		Alan Cox	:	ip_forward sets the free flag on the
 28 *					new frame it queues. Still crap because
 29 *					it copies the frame but at least it
 30 *					doesn't eat memory too.
 31 *		Alan Cox	:	Generic queue code and memory fixes.
 32 *		Fred Van Kempen :	IP fragment support (borrowed from NET2E)
 33 *		Gerhard Koerting:	Forward fragmented frames correctly.
 34 *		Gerhard Koerting: 	Fixes to my fix of the above 8-).
 35 *		Gerhard Koerting:	IP interface addressing fix.
 36 *		Linus Torvalds	:	More robustness checks
 37 *		Alan Cox	:	Even more checks: Still not as robust as it ought to be
 38 *		Alan Cox	:	Save IP header pointer for later
 39 *		Alan Cox	:	ip option setting
 40 *		Alan Cox	:	Use ip_tos/ip_ttl settings
 41 *		Alan Cox	:	Fragmentation bogosity removed
 42 *					(Thanks to Mark.Bush@prg.ox.ac.uk)
 43 *		Dmitry Gorodchanin :	Send of a raw packet crash fix.
 44 *		Alan Cox	:	Silly ip bug when an overlength
 45 *					fragment turns up. Now frees the
 46 *					queue.
 47 *		Linus Torvalds/ :	Memory leakage on fragmentation
 48 *		Alan Cox	:	handling.
 49 *		Gerhard Koerting:	Forwarding uses IP priority hints
 50 *		Teemu Rantanen	:	Fragment problems.
 51 *		Alan Cox	:	General cleanup, comments and reformat
 52 *		Alan Cox	:	SNMP statistics
 53 *		Alan Cox	:	BSD address rule semantics. Also see
 54 *					UDP as there is a nasty checksum issue
 55 *					if you do things the wrong way.
 56 *		Alan Cox	:	Always defrag, moved IP_FORWARD to the config.in file
 57 *		Alan Cox	: 	IP options adjust sk->priority.
 58 *		Pedro Roque	:	Fix mtu/length error in ip_forward.
 59 *		Alan Cox	:	Avoid ip_chk_addr when possible.
 60 *	Richard Underwood	:	IP multicasting.
 61 *		Alan Cox	:	Cleaned up multicast handlers.
 62 *		Alan Cox	:	RAW sockets demultiplex in the BSD style.
 63 *		Gunther Mayer	:	Fix the SNMP reporting typo
 64 *		Alan Cox	:	Always in group 224.0.0.1
 65 *	Pauline Middelink	:	Fast ip_checksum update when forwarding
 66 *					Masquerading support.
 67 *		Alan Cox	:	Multicast loopback error for 224.0.0.1
 68 *		Alan Cox	:	IP_MULTICAST_LOOP option.
 69 *		Alan Cox	:	Use notifiers.
 70 *		Bjorn Ekwall	:	Removed ip_csum (from slhc.c too)
 71 *		Bjorn Ekwall	:	Moved ip_fast_csum to ip.h (inline!)
 72 *		Stefan Becker   :       Send out ICMP HOST REDIRECT
 73 *	Arnt Gulbrandsen	:	ip_build_xmit
 74 *		Alan Cox	:	Per socket routing cache
 75 *		Alan Cox	:	Fixed routing cache, added header cache.
 76 *		Alan Cox	:	Loopback didn't work right in original ip_build_xmit - fixed it.
 77 *		Alan Cox	:	Only send ICMP_REDIRECT if src/dest are the same net.
 78 *		Alan Cox	:	Incoming IP option handling.
 79 *		Alan Cox	:	Set saddr on raw output frames as per BSD.
 80 *		Alan Cox	:	Stopped broadcast source route explosions.
 81 *		Alan Cox	:	Can disable source routing
 82 *		Takeshi Sone    :	Masquerading didn't work.
 83 *	Dave Bonn,Alan Cox	:	Faster IP forwarding whenever possible.
 84 *		Alan Cox	:	Memory leaks, tramples, misc debugging.
 85 *		Alan Cox	:	Fixed multicast (by popular demand 8))
 86 *		Alan Cox	:	Fixed forwarding (by even more popular demand 8))
 87 *		Alan Cox	:	Fixed SNMP statistics [I think]
 88 *	Gerhard Koerting	:	IP fragmentation forwarding fix
 89 *		Alan Cox	:	Device lock against page fault.
 90 *		Alan Cox	:	IP_HDRINCL facility.
 91 *	Werner Almesberger	:	Zero fragment bug
 92 *		Alan Cox	:	RAW IP frame length bug
 93 *		Alan Cox	:	Outgoing firewall on build_xmit
 94 *		A.N.Kuznetsov	:	IP_OPTIONS support throughout the kernel
 95 *		Alan Cox	:	Multicast routing hooks
 96 *		Jos Vos		:	Do accounting *before* call_in_firewall
 97 *	Willy Konynenberg	:	Transparent proxying support
 98 *
 99 * To Fix:
100 *		IP fragmentation wants rewriting cleanly. The RFC815 algorithm is much more efficient
101 *		and could be made very efficient with the addition of some virtual memory hacks to permit
102 *		the allocation of a buffer that can then be 'grown' by twiddling page tables.
103 *		Output fragmentation wants updating along with the buffer management to use a single
104 *		interleaved copy algorithm so that fragmenting has a one copy overhead. Actual packet
105 *		output should probably do its own fragmentation at the UDP/RAW layer. TCP shouldn't cause
106 *		fragmentation anyway.
107 */
108
109#define pr_fmt(fmt) "IPv4: " fmt
110
111#include <linux/module.h>
112#include <linux/types.h>
113#include <linux/kernel.h>
114#include <linux/string.h>
115#include <linux/errno.h>
116#include <linux/slab.h>
117
118#include <linux/net.h>
119#include <linux/socket.h>
120#include <linux/sockios.h>
121#include <linux/in.h>
122#include <linux/inet.h>
123#include <linux/inetdevice.h>
124#include <linux/netdevice.h>
125#include <linux/etherdevice.h>
126#include <linux/indirect_call_wrapper.h>
127
128#include <net/snmp.h>
129#include <net/ip.h>
130#include <net/protocol.h>
131#include <net/route.h>
132#include <linux/skbuff.h>
133#include <net/sock.h>
134#include <net/arp.h>
135#include <net/icmp.h>
136#include <net/raw.h>
137#include <net/checksum.h>
138#include <net/inet_ecn.h>
139#include <linux/netfilter_ipv4.h>
140#include <net/xfrm.h>
141#include <linux/mroute.h>
142#include <linux/netlink.h>
143#include <net/dst_metadata.h>
144#include <net/udp.h>
145#include <net/tcp.h>
146
147/*
148 *	Process Router Attention IP option (RFC 2113)
149 */
150bool ip_call_ra_chain(struct sk_buff *skb)
151{
152	struct ip_ra_chain *ra;
153	u8 protocol = ip_hdr(skb)->protocol;
154	struct sock *last = NULL;
155	struct net_device *dev = skb->dev;
156	struct net *net = dev_net(dev);
157
158	for (ra = rcu_dereference(net->ipv4.ra_chain); ra; ra = rcu_dereference(ra->next)) {
159		struct sock *sk = ra->sk;
160
161		/* If socket is bound to an interface, only report
162		 * the packet if it came  from that interface.
163		 */
164		if (sk && inet_sk(sk)->inet_num == protocol &&
165		    (!sk->sk_bound_dev_if ||
166		     sk->sk_bound_dev_if == dev->ifindex)) {
167			if (ip_is_fragment(ip_hdr(skb))) {
168				if (ip_defrag(net, skb, IP_DEFRAG_CALL_RA_CHAIN))
169					return true;
170			}
171			if (last) {
172				struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);
173				if (skb2)
174					raw_rcv(last, skb2);
175			}
176			last = sk;
177		}
178	}
179
180	if (last) {
181		raw_rcv(last, skb);
182		return true;
183	}
184	return false;
185}
186
187INDIRECT_CALLABLE_DECLARE(int udp_rcv(struct sk_buff *));
188INDIRECT_CALLABLE_DECLARE(int tcp_v4_rcv(struct sk_buff *));
189void ip_protocol_deliver_rcu(struct net *net, struct sk_buff *skb, int protocol)
190{
191	const struct net_protocol *ipprot;
192	int raw, ret;
193
194resubmit:
195	raw = raw_local_deliver(skb, protocol);
196
197	ipprot = rcu_dereference(inet_protos[protocol]);
198	if (ipprot) {
199		if (!ipprot->no_policy) {
200			if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
201				kfree_skb_reason(skb,
202						 SKB_DROP_REASON_XFRM_POLICY);
203				return;
204			}
205			nf_reset_ct(skb);
206		}
207		ret = INDIRECT_CALL_2(ipprot->handler, tcp_v4_rcv, udp_rcv,
208				      skb);
209		if (ret < 0) {
210			protocol = -ret;
211			goto resubmit;
212		}
213		__IP_INC_STATS(net, IPSTATS_MIB_INDELIVERS);
214	} else {
215		if (!raw) {
216			if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
217				__IP_INC_STATS(net, IPSTATS_MIB_INUNKNOWNPROTOS);
218				icmp_send(skb, ICMP_DEST_UNREACH,
219					  ICMP_PROT_UNREACH, 0);
220			}
221			kfree_skb_reason(skb, SKB_DROP_REASON_IP_NOPROTO);
222		} else {
223			__IP_INC_STATS(net, IPSTATS_MIB_INDELIVERS);
224			consume_skb(skb);
225		}
226	}
227}
228
229static int ip_local_deliver_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
230{
231	if (unlikely(skb_orphan_frags_rx(skb, GFP_ATOMIC))) {
232		__IP_INC_STATS(net, IPSTATS_MIB_INDISCARDS);
233		kfree_skb_reason(skb, SKB_DROP_REASON_NOMEM);
234		return 0;
235	}
236
237	skb_clear_delivery_time(skb);
238	__skb_pull(skb, skb_network_header_len(skb));
239
240	rcu_read_lock();
241	ip_protocol_deliver_rcu(net, skb, ip_hdr(skb)->protocol);
242	rcu_read_unlock();
243
244	return 0;
245}
246
247/*
248 * 	Deliver IP Packets to the higher protocol layers.
249 */
250int ip_local_deliver(struct sk_buff *skb)
251{
252	/*
253	 *	Reassemble IP fragments.
254	 */
255	struct net *net = dev_net(skb->dev);
256
257	if (ip_is_fragment(ip_hdr(skb))) {
258		if (ip_defrag(net, skb, IP_DEFRAG_LOCAL_DELIVER))
259			return 0;
260	}
261
262	return NF_HOOK(NFPROTO_IPV4, NF_INET_LOCAL_IN,
263		       net, NULL, skb, skb->dev, NULL,
264		       ip_local_deliver_finish);
265}
266EXPORT_SYMBOL(ip_local_deliver);
267
268static inline enum skb_drop_reason
269ip_rcv_options(struct sk_buff *skb, struct net_device *dev)
270{
271	const struct iphdr *iph;
272	struct ip_options *opt;
273
274	/* It looks as overkill, because not all
275	   IP options require packet mangling.
276	   But it is the easiest for now, especially taking
277	   into account that combination of IP options
278	   and running sniffer is extremely rare condition.
279					      --ANK (980813)
280	*/
281	if (skb_cow(skb, skb_headroom(skb))) {
282		__IP_INC_STATS(dev_net(dev), IPSTATS_MIB_INDISCARDS);
283		return SKB_DROP_REASON_NOMEM;
284	}
285
286	iph = ip_hdr(skb);
287	opt = &(IPCB(skb)->opt);
288	opt->optlen = iph->ihl*4 - sizeof(struct iphdr);
289
290	if (ip_options_compile(dev_net(dev), opt, skb)) {
291		__IP_INC_STATS(dev_net(dev), IPSTATS_MIB_INHDRERRORS);
292		return SKB_DROP_REASON_IP_INHDR;
293	}
294
295	if (unlikely(opt->srr)) {
296		struct in_device *in_dev = __in_dev_get_rcu(dev);
297
298		if (in_dev) {
299			if (!IN_DEV_SOURCE_ROUTE(in_dev)) {
300				if (IN_DEV_LOG_MARTIANS(in_dev))
301					net_info_ratelimited("source route option %pI4 -> %pI4\n",
302							     &iph->saddr,
303							     &iph->daddr);
304				return SKB_DROP_REASON_NOT_SPECIFIED;
305			}
306		}
307
308		if (ip_options_rcv_srr(skb, dev))
309			return SKB_DROP_REASON_NOT_SPECIFIED;
310	}
311
312	return SKB_NOT_DROPPED_YET;
313}
314
315static bool ip_can_use_hint(const struct sk_buff *skb, const struct iphdr *iph,
316			    const struct sk_buff *hint)
317{
318	return hint && !skb_dst(skb) && ip_hdr(hint)->daddr == iph->daddr &&
319	       ip_hdr(hint)->tos == iph->tos;
320}
321
322static int ip_rcv_finish_core(struct net *net,
323			      struct sk_buff *skb, struct net_device *dev,
324			      const struct sk_buff *hint)
325{
326	const struct iphdr *iph = ip_hdr(skb);
327	struct rtable *rt;
328	int drop_reason;
329
330	if (ip_can_use_hint(skb, iph, hint)) {
331		drop_reason = ip_route_use_hint(skb, iph->daddr, iph->saddr,
332						ip4h_dscp(iph), dev, hint);
333		if (unlikely(drop_reason))
334			goto drop_error;
335	}
336
337	if (READ_ONCE(net->ipv4.sysctl_ip_early_demux) &&
338	    !skb_dst(skb) &&
339	    !skb->sk &&
340	    !ip_is_fragment(iph)) {
341		switch (iph->protocol) {
342		case IPPROTO_TCP:
343			if (READ_ONCE(net->ipv4.sysctl_tcp_early_demux)) {
344				tcp_v4_early_demux(skb);
345
346				/* must reload iph, skb->head might have changed */
347				iph = ip_hdr(skb);
348			}
349			break;
350		case IPPROTO_UDP:
351			if (READ_ONCE(net->ipv4.sysctl_udp_early_demux)) {
352				drop_reason = udp_v4_early_demux(skb);
353				if (unlikely(drop_reason))
354					goto drop_error;
355
356				/* must reload iph, skb->head might have changed */
357				iph = ip_hdr(skb);
358			}
359			break;
360		}
361	}
362
363	/*
364	 *	Initialise the virtual path cache for the packet. It describes
365	 *	how the packet travels inside Linux networking.
366	 */
367	if (!skb_valid_dst(skb)) {
368		drop_reason = ip_route_input_noref(skb, iph->daddr, iph->saddr,
369						   ip4h_dscp(iph), dev);
370		if (unlikely(drop_reason))
371			goto drop_error;
372	} else {
373		struct in_device *in_dev = __in_dev_get_rcu(dev);
374
375		if (in_dev && IN_DEV_ORCONF(in_dev, NOPOLICY))
376			IPCB(skb)->flags |= IPSKB_NOPOLICY;
377	}
378
379#ifdef CONFIG_IP_ROUTE_CLASSID
380	if (unlikely(skb_dst(skb)->tclassid)) {
381		struct ip_rt_acct *st = this_cpu_ptr(ip_rt_acct);
382		u32 idx = skb_dst(skb)->tclassid;
383		st[idx&0xFF].o_packets++;
384		st[idx&0xFF].o_bytes += skb->len;
385		st[(idx>>16)&0xFF].i_packets++;
386		st[(idx>>16)&0xFF].i_bytes += skb->len;
387	}
388#endif
389
390	if (iph->ihl > 5) {
391		drop_reason = ip_rcv_options(skb, dev);
392		if (drop_reason)
393			goto drop;
394	}
395
396	rt = skb_rtable(skb);
397	if (rt->rt_type == RTN_MULTICAST) {
398		__IP_UPD_PO_STATS(net, IPSTATS_MIB_INMCAST, skb->len);
399	} else if (rt->rt_type == RTN_BROADCAST) {
400		__IP_UPD_PO_STATS(net, IPSTATS_MIB_INBCAST, skb->len);
401	} else if (skb->pkt_type == PACKET_BROADCAST ||
402		   skb->pkt_type == PACKET_MULTICAST) {
403		struct in_device *in_dev = __in_dev_get_rcu(dev);
404
405		/* RFC 1122 3.3.6:
406		 *
407		 *   When a host sends a datagram to a link-layer broadcast
408		 *   address, the IP destination address MUST be a legal IP
409		 *   broadcast or IP multicast address.
410		 *
411		 *   A host SHOULD silently discard a datagram that is received
412		 *   via a link-layer broadcast (see Section 2.4) but does not
413		 *   specify an IP multicast or broadcast destination address.
414		 *
415		 * This doesn't explicitly say L2 *broadcast*, but broadcast is
416		 * in a way a form of multicast and the most common use case for
417		 * this is 802.11 protecting against cross-station spoofing (the
418		 * so-called "hole-196" attack) so do it for both.
419		 */
420		if (in_dev &&
421		    IN_DEV_ORCONF(in_dev, DROP_UNICAST_IN_L2_MULTICAST)) {
422			drop_reason = SKB_DROP_REASON_UNICAST_IN_L2_MULTICAST;
423			goto drop;
424		}
425	}
426
427	return NET_RX_SUCCESS;
428
429drop:
430	kfree_skb_reason(skb, drop_reason);
431	return NET_RX_DROP;
432
433drop_error:
434	if (drop_reason == SKB_DROP_REASON_IP_RPFILTER)
435		__NET_INC_STATS(net, LINUX_MIB_IPRPFILTER);
436	goto drop;
437}
438
439static int ip_rcv_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
440{
441	struct net_device *dev = skb->dev;
442	int ret;
443
444	/* if ingress device is enslaved to an L3 master device pass the
445	 * skb to its handler for processing
446	 */
447	skb = l3mdev_ip_rcv(skb);
448	if (!skb)
449		return NET_RX_SUCCESS;
450
451	ret = ip_rcv_finish_core(net, skb, dev, NULL);
452	if (ret != NET_RX_DROP)
453		ret = dst_input(skb);
454	return ret;
455}
456
457/*
458 * 	Main IP Receive routine.
459 */
460static struct sk_buff *ip_rcv_core(struct sk_buff *skb, struct net *net)
461{
462	const struct iphdr *iph;
463	int drop_reason;
464	u32 len;
465
466	/* When the interface is in promisc. mode, drop all the crap
467	 * that it receives, do not try to analyse it.
468	 */
469	if (skb->pkt_type == PACKET_OTHERHOST) {
470		dev_core_stats_rx_otherhost_dropped_inc(skb->dev);
471		drop_reason = SKB_DROP_REASON_OTHERHOST;
472		goto drop;
473	}
474
475	__IP_UPD_PO_STATS(net, IPSTATS_MIB_IN, skb->len);
476
477	skb = skb_share_check(skb, GFP_ATOMIC);
478	if (!skb) {
479		__IP_INC_STATS(net, IPSTATS_MIB_INDISCARDS);
480		goto out;
481	}
482
483	drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;
484	if (!pskb_may_pull(skb, sizeof(struct iphdr)))
485		goto inhdr_error;
486
487	iph = ip_hdr(skb);
488
489	/*
490	 *	RFC1122: 3.2.1.2 MUST silently discard any IP frame that fails the checksum.
491	 *
492	 *	Is the datagram acceptable?
493	 *
494	 *	1.	Length at least the size of an ip header
495	 *	2.	Version of 4
496	 *	3.	Checksums correctly. [Speed optimisation for later, skip loopback checksums]
497	 *	4.	Doesn't have a bogus length
498	 */
499
500	if (iph->ihl < 5 || iph->version != 4)
501		goto inhdr_error;
502
503	BUILD_BUG_ON(IPSTATS_MIB_ECT1PKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_ECT_1);
504	BUILD_BUG_ON(IPSTATS_MIB_ECT0PKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_ECT_0);
505	BUILD_BUG_ON(IPSTATS_MIB_CEPKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_CE);
506	__IP_ADD_STATS(net,
507		       IPSTATS_MIB_NOECTPKTS + (iph->tos & INET_ECN_MASK),
508		       max_t(unsigned short, 1, skb_shinfo(skb)->gso_segs));
509
510	if (!pskb_may_pull(skb, iph->ihl*4))
511		goto inhdr_error;
512
513	iph = ip_hdr(skb);
514
515	if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl)))
516		goto csum_error;
517
518	len = iph_totlen(skb, iph);
519	if (skb->len < len) {
520		drop_reason = SKB_DROP_REASON_PKT_TOO_SMALL;
521		__IP_INC_STATS(net, IPSTATS_MIB_INTRUNCATEDPKTS);
522		goto drop;
523	} else if (len < (iph->ihl*4))
524		goto inhdr_error;
525
526	/* Our transport medium may have padded the buffer out. Now we know it
527	 * is IP we can trim to the true length of the frame.
528	 * Note this now means skb->len holds ntohs(iph->tot_len).
529	 */
530	if (pskb_trim_rcsum(skb, len)) {
531		__IP_INC_STATS(net, IPSTATS_MIB_INDISCARDS);
532		goto drop;
533	}
534
535	iph = ip_hdr(skb);
536	skb->transport_header = skb->network_header + iph->ihl*4;
537
538	/* Remove any debris in the socket control block */
539	memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
540	IPCB(skb)->iif = skb->skb_iif;
541
542	/* Must drop socket now because of tproxy. */
543	if (!skb_sk_is_prefetched(skb))
544		skb_orphan(skb);
545
546	return skb;
547
548csum_error:
549	drop_reason = SKB_DROP_REASON_IP_CSUM;
550	__IP_INC_STATS(net, IPSTATS_MIB_CSUMERRORS);
551inhdr_error:
552	if (drop_reason == SKB_DROP_REASON_NOT_SPECIFIED)
553		drop_reason = SKB_DROP_REASON_IP_INHDR;
554	__IP_INC_STATS(net, IPSTATS_MIB_INHDRERRORS);
555drop:
556	kfree_skb_reason(skb, drop_reason);
557out:
558	return NULL;
559}
560
561/*
562 * IP receive entry point
563 */
564int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt,
565	   struct net_device *orig_dev)
566{
567	struct net *net = dev_net(dev);
568
569	skb = ip_rcv_core(skb, net);
570	if (skb == NULL)
571		return NET_RX_DROP;
572
573	return NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING,
574		       net, NULL, skb, dev, NULL,
575		       ip_rcv_finish);
576}
577
578static void ip_sublist_rcv_finish(struct list_head *head)
579{
580	struct sk_buff *skb, *next;
581
582	list_for_each_entry_safe(skb, next, head, list) {
583		skb_list_del_init(skb);
584		dst_input(skb);
585	}
586}
587
588static struct sk_buff *ip_extract_route_hint(const struct net *net,
589					     struct sk_buff *skb)
590{
591	const struct iphdr *iph = ip_hdr(skb);
592
593	if (fib4_has_custom_rules(net) ||
594	    ipv4_is_lbcast(iph->daddr) ||
595	    ipv4_is_zeronet(iph->daddr) ||
596	    IPCB(skb)->flags & IPSKB_MULTIPATH)
597		return NULL;
598
599	return skb;
600}
601
602static void ip_list_rcv_finish(struct net *net, struct list_head *head)
603{
604	struct sk_buff *skb, *next, *hint = NULL;
605	struct dst_entry *curr_dst = NULL;
606	LIST_HEAD(sublist);
607
608	list_for_each_entry_safe(skb, next, head, list) {
609		struct net_device *dev = skb->dev;
610		struct dst_entry *dst;
611
612		skb_list_del_init(skb);
613		/* if ingress device is enslaved to an L3 master device pass the
614		 * skb to its handler for processing
615		 */
616		skb = l3mdev_ip_rcv(skb);
617		if (!skb)
618			continue;
619		if (ip_rcv_finish_core(net, skb, dev, hint) == NET_RX_DROP)
620			continue;
621
622		dst = skb_dst(skb);
623		if (curr_dst != dst) {
624			hint = ip_extract_route_hint(net, skb);
625
626			/* dispatch old sublist */
627			if (!list_empty(&sublist))
628				ip_sublist_rcv_finish(&sublist);
629			/* start new sublist */
630			INIT_LIST_HEAD(&sublist);
631			curr_dst = dst;
632		}
633		list_add_tail(&skb->list, &sublist);
634	}
635	/* dispatch final sublist */
636	ip_sublist_rcv_finish(&sublist);
637}
638
639static void ip_sublist_rcv(struct list_head *head, struct net_device *dev,
640			   struct net *net)
641{
642	NF_HOOK_LIST(NFPROTO_IPV4, NF_INET_PRE_ROUTING, net, NULL,
643		     head, dev, NULL, ip_rcv_finish);
644	ip_list_rcv_finish(net, head);
645}
646
647/* Receive a list of IP packets */
648void ip_list_rcv(struct list_head *head, struct packet_type *pt,
649		 struct net_device *orig_dev)
650{
651	struct net_device *curr_dev = NULL;
652	struct net *curr_net = NULL;
653	struct sk_buff *skb, *next;
654	LIST_HEAD(sublist);
655
656	list_for_each_entry_safe(skb, next, head, list) {
657		struct net_device *dev = skb->dev;
658		struct net *net = dev_net(dev);
659
660		skb_list_del_init(skb);
661		skb = ip_rcv_core(skb, net);
662		if (skb == NULL)
663			continue;
664
665		if (curr_dev != dev || curr_net != net) {
666			/* dispatch old sublist */
667			if (!list_empty(&sublist))
668				ip_sublist_rcv(&sublist, curr_dev, curr_net);
669			/* start new sublist */
670			INIT_LIST_HEAD(&sublist);
671			curr_dev = dev;
672			curr_net = net;
673		}
674		list_add_tail(&skb->list, &sublist);
675	}
676	/* dispatch final sublist */
677	if (!list_empty(&sublist))
678		ip_sublist_rcv(&sublist, curr_dev, curr_net);
679}