1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 *	IPv6 input
4 *	Linux INET6 implementation
5 *
6 *	Authors:
7 *	Pedro Roque		<roque@di.fc.ul.pt>
8 *	Ian P. Morris		<I.P.Morris@soton.ac.uk>
9 *
10 *	Based in linux/net/ipv4/ip_input.c
11 */
12/* Changes
13 *
14 *	Mitsuru KANDA @USAGI and
15 *	YOSHIFUJI Hideaki @USAGI: Remove ipv6_parse_exthdrs().
16 */
17
18#include <linux/errno.h>
19#include <linux/types.h>
20#include <linux/socket.h>
21#include <linux/sockios.h>
22#include <linux/net.h>
23#include <linux/netdevice.h>
24#include <linux/in6.h>
25#include <linux/icmpv6.h>
26#include <linux/mroute6.h>
27#include <linux/slab.h>
28#include <linux/indirect_call_wrapper.h>
29
30#include <linux/netfilter.h>
31#include <linux/netfilter_ipv6.h>
32
33#include <net/sock.h>
34#include <net/snmp.h>
35#include <net/udp.h>
36
37#include <net/ipv6.h>
38#include <net/protocol.h>
39#include <net/transp_v6.h>
40#include <net/rawv6.h>
41#include <net/ndisc.h>
42#include <net/ip6_route.h>
43#include <net/addrconf.h>
44#include <net/xfrm.h>
45#include <net/inet_ecn.h>
46#include <net/dst_metadata.h>
47
48static void ip6_rcv_finish_core(struct net *net, struct sock *sk,
49				struct sk_buff *skb)
50{
51	if (READ_ONCE(net->ipv4.sysctl_ip_early_demux) &&
52	    !skb_dst(skb) && !skb->sk) {
53		switch (ipv6_hdr(skb)->nexthdr) {
54		case IPPROTO_TCP:
55			if (READ_ONCE(net->ipv4.sysctl_tcp_early_demux))
56				tcp_v6_early_demux(skb);
57			break;
58		case IPPROTO_UDP:
59			if (READ_ONCE(net->ipv4.sysctl_udp_early_demux))
60				udp_v6_early_demux(skb);
61			break;
62		}
63	}
64
65	if (!skb_valid_dst(skb))
66		ip6_route_input(skb);
67}
68
69int ip6_rcv_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
70{
71	/* if ingress device is enslaved to an L3 master device pass the
72	 * skb to its handler for processing
73	 */
74	skb = l3mdev_ip6_rcv(skb);
75	if (!skb)
76		return NET_RX_SUCCESS;
77	ip6_rcv_finish_core(net, sk, skb);
78
79	return dst_input(skb);
80}
81
82static void ip6_sublist_rcv_finish(struct list_head *head)
83{
84	struct sk_buff *skb, *next;
85
86	list_for_each_entry_safe(skb, next, head, list) {
87		skb_list_del_init(skb);
88		dst_input(skb);
89	}
90}
91
92static bool ip6_can_use_hint(const struct sk_buff *skb,
93			     const struct sk_buff *hint)
94{
95	return hint && !skb_dst(skb) &&
96	       ipv6_addr_equal(&ipv6_hdr(hint)->daddr, &ipv6_hdr(skb)->daddr);
97}
98
99static struct sk_buff *ip6_extract_route_hint(const struct net *net,
100					      struct sk_buff *skb)
101{
102	if (fib6_routes_require_src(net) || fib6_has_custom_rules(net) ||
103	    IP6CB(skb)->flags & IP6SKB_MULTIPATH)
104		return NULL;
105
106	return skb;
107}
108
109static void ip6_list_rcv_finish(struct net *net, struct sock *sk,
110				struct list_head *head)
111{
112	struct sk_buff *skb, *next, *hint = NULL;
113	struct dst_entry *curr_dst = NULL;
114	struct list_head sublist;
115
116	INIT_LIST_HEAD(&sublist);
117	list_for_each_entry_safe(skb, next, head, list) {
118		struct dst_entry *dst;
119
120		skb_list_del_init(skb);
121		/* if ingress device is enslaved to an L3 master device pass the
122		 * skb to its handler for processing
123		 */
124		skb = l3mdev_ip6_rcv(skb);
125		if (!skb)
126			continue;
127
128		if (ip6_can_use_hint(skb, hint))
129			skb_dst_copy(skb, hint);
130		else
131			ip6_rcv_finish_core(net, sk, skb);
132		dst = skb_dst(skb);
133		if (curr_dst != dst) {
134			hint = ip6_extract_route_hint(net, skb);
135
136			/* dispatch old sublist */
137			if (!list_empty(&sublist))
138				ip6_sublist_rcv_finish(&sublist);
139			/* start new sublist */
140			INIT_LIST_HEAD(&sublist);
141			curr_dst = dst;
142		}
143		list_add_tail(&skb->list, &sublist);
144	}
145	/* dispatch final sublist */
146	ip6_sublist_rcv_finish(&sublist);
147}
148
149static struct sk_buff *ip6_rcv_core(struct sk_buff *skb, struct net_device *dev,
150				    struct net *net)
151{
152	enum skb_drop_reason reason;
153	const struct ipv6hdr *hdr;
154	u32 pkt_len;
155	struct inet6_dev *idev;
156
157	if (skb->pkt_type == PACKET_OTHERHOST) {
158		dev_core_stats_rx_otherhost_dropped_inc(skb->dev);
159		kfree_skb_reason(skb, SKB_DROP_REASON_OTHERHOST);
160		return NULL;
161	}
162
163	rcu_read_lock();
164
165	idev = __in6_dev_get(skb->dev);
166
167	__IP6_UPD_PO_STATS(net, idev, IPSTATS_MIB_IN, skb->len);
168
169	SKB_DR_SET(reason, NOT_SPECIFIED);
170	if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL ||
171	    !idev || unlikely(READ_ONCE(idev->cnf.disable_ipv6))) {
172		__IP6_INC_STATS(net, idev, IPSTATS_MIB_INDISCARDS);
173		if (idev && unlikely(READ_ONCE(idev->cnf.disable_ipv6)))
174			SKB_DR_SET(reason, IPV6DISABLED);
175		goto drop;
176	}
177
178	memset(IP6CB(skb), 0, sizeof(struct inet6_skb_parm));
179
180	/*
181	 * Store incoming device index. When the packet will
182	 * be queued, we cannot refer to skb->dev anymore.
183	 *
184	 * BTW, when we send a packet for our own local address on a
185	 * non-loopback interface (e.g. ethX), it is being delivered
186	 * via the loopback interface (lo) here; skb->dev = loopback_dev.
187	 * It, however, should be considered as if it is being
188	 * arrived via the sending interface (ethX), because of the
189	 * nature of scoping architecture. --yoshfuji
190	 */
191	IP6CB(skb)->iif = skb_valid_dst(skb) ? ip6_dst_idev(skb_dst(skb))->dev->ifindex : dev->ifindex;
192
193	if (unlikely(!pskb_may_pull(skb, sizeof(*hdr))))
194		goto err;
195
196	hdr = ipv6_hdr(skb);
197
198	if (hdr->version != 6) {
199		SKB_DR_SET(reason, UNHANDLED_PROTO);
200		goto err;
201	}
202
203	__IP6_ADD_STATS(net, idev,
204			IPSTATS_MIB_NOECTPKTS +
205				(ipv6_get_dsfield(hdr) & INET_ECN_MASK),
206			max_t(unsigned short, 1, skb_shinfo(skb)->gso_segs));
207	/*
208	 * RFC4291 2.5.3
209	 * The loopback address must not be used as the source address in IPv6
210	 * packets that are sent outside of a single node. [..]
211	 * A packet received on an interface with a destination address
212	 * of loopback must be dropped.
213	 */
214	if ((ipv6_addr_loopback(&hdr->saddr) ||
215	     ipv6_addr_loopback(&hdr->daddr)) &&
216	    !(dev->flags & IFF_LOOPBACK) &&
217	    !netif_is_l3_master(dev))
218		goto err;
219
220	/* RFC4291 Errata ID: 3480
221	 * Interface-Local scope spans only a single interface on a
222	 * node and is useful only for loopback transmission of
223	 * multicast.  Packets with interface-local scope received
224	 * from another node must be discarded.
225	 */
226	if (!(skb->pkt_type == PACKET_LOOPBACK ||
227	      dev->flags & IFF_LOOPBACK) &&
228	    ipv6_addr_is_multicast(&hdr->daddr) &&
229	    IPV6_ADDR_MC_SCOPE(&hdr->daddr) == 1)
230		goto err;
231
232	/* If enabled, drop unicast packets that were encapsulated in link-layer
233	 * multicast or broadcast to protected against the so-called "hole-196"
234	 * attack in 802.11 wireless.
235	 */
236	if (!ipv6_addr_is_multicast(&hdr->daddr) &&
237	    (skb->pkt_type == PACKET_BROADCAST ||
238	     skb->pkt_type == PACKET_MULTICAST) &&
239	    READ_ONCE(idev->cnf.drop_unicast_in_l2_multicast)) {
240		SKB_DR_SET(reason, UNICAST_IN_L2_MULTICAST);
241		goto err;
242	}
243
244	/* RFC4291 2.7
245	 * Nodes must not originate a packet to a multicast address whose scope
246	 * field contains the reserved value 0; if such a packet is received, it
247	 * must be silently dropped.
248	 */
249	if (ipv6_addr_is_multicast(&hdr->daddr) &&
250	    IPV6_ADDR_MC_SCOPE(&hdr->daddr) == 0)
251		goto err;
252
253	/*
254	 * RFC4291 2.7
255	 * Multicast addresses must not be used as source addresses in IPv6
256	 * packets or appear in any Routing header.
257	 */
258	if (ipv6_addr_is_multicast(&hdr->saddr))
259		goto err;
260
261	skb->transport_header = skb->network_header + sizeof(*hdr);
262	IP6CB(skb)->nhoff = offsetof(struct ipv6hdr, nexthdr);
263
264	pkt_len = ntohs(hdr->payload_len);
265
266	/* pkt_len may be zero if Jumbo payload option is present */
267	if (pkt_len || hdr->nexthdr != NEXTHDR_HOP) {
268		if (pkt_len + sizeof(struct ipv6hdr) > skb->len) {
269			__IP6_INC_STATS(net,
270					idev, IPSTATS_MIB_INTRUNCATEDPKTS);
271			SKB_DR_SET(reason, PKT_TOO_SMALL);
272			goto drop;
273		}
274		if (pskb_trim_rcsum(skb, pkt_len + sizeof(struct ipv6hdr)))
275			goto err;
276		hdr = ipv6_hdr(skb);
277	}
278
279	if (hdr->nexthdr == NEXTHDR_HOP) {
280		if (ipv6_parse_hopopts(skb) < 0) {
281			__IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
282			rcu_read_unlock();
283			return NULL;
284		}
285	}
286
287	rcu_read_unlock();
288
289	/* Must drop socket now because of tproxy. */
290	if (!skb_sk_is_prefetched(skb))
291		skb_orphan(skb);
292
293	return skb;
294err:
295	__IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
296	SKB_DR_OR(reason, IP_INHDR);
297drop:
298	rcu_read_unlock();
299	kfree_skb_reason(skb, reason);
300	return NULL;
301}
302
303int ipv6_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev)
304{
305	struct net *net = dev_net(skb->dev);
306
307	skb = ip6_rcv_core(skb, dev, net);
308	if (skb == NULL)
309		return NET_RX_DROP;
310	return NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING,
311		       net, NULL, skb, dev, NULL,
312		       ip6_rcv_finish);
313}
314
315static void ip6_sublist_rcv(struct list_head *head, struct net_device *dev,
316			    struct net *net)
317{
318	NF_HOOK_LIST(NFPROTO_IPV6, NF_INET_PRE_ROUTING, net, NULL,
319		     head, dev, NULL, ip6_rcv_finish);
320	ip6_list_rcv_finish(net, NULL, head);
321}
322
323/* Receive a list of IPv6 packets */
324void ipv6_list_rcv(struct list_head *head, struct packet_type *pt,
325		   struct net_device *orig_dev)
326{
327	struct net_device *curr_dev = NULL;
328	struct net *curr_net = NULL;
329	struct sk_buff *skb, *next;
330	struct list_head sublist;
331
332	INIT_LIST_HEAD(&sublist);
333	list_for_each_entry_safe(skb, next, head, list) {
334		struct net_device *dev = skb->dev;
335		struct net *net = dev_net(dev);
336
337		skb_list_del_init(skb);
338		skb = ip6_rcv_core(skb, dev, net);
339		if (skb == NULL)
340			continue;
341
342		if (curr_dev != dev || curr_net != net) {
343			/* dispatch old sublist */
344			if (!list_empty(&sublist))
345				ip6_sublist_rcv(&sublist, curr_dev, curr_net);
346			/* start new sublist */
347			INIT_LIST_HEAD(&sublist);
348			curr_dev = dev;
349			curr_net = net;
350		}
351		list_add_tail(&skb->list, &sublist);
352	}
353	/* dispatch final sublist */
354	if (!list_empty(&sublist))
355		ip6_sublist_rcv(&sublist, curr_dev, curr_net);
356}
357
358INDIRECT_CALLABLE_DECLARE(int tcp_v6_rcv(struct sk_buff *));
359
360/*
361 *	Deliver the packet to the host
362 */
363void ip6_protocol_deliver_rcu(struct net *net, struct sk_buff *skb, int nexthdr,
364			      bool have_final)
365{
366	const struct inet6_protocol *ipprot;
367	struct inet6_dev *idev;
368	unsigned int nhoff;
369	SKB_DR(reason);
370	bool raw;
371
372	/*
373	 *	Parse extension headers
374	 */
375
376resubmit:
377	idev = ip6_dst_idev(skb_dst(skb));
378	nhoff = IP6CB(skb)->nhoff;
379	if (!have_final) {
380		if (!pskb_pull(skb, skb_transport_offset(skb)))
381			goto discard;
382		nexthdr = skb_network_header(skb)[nhoff];
383	}
384
385resubmit_final:
386	raw = raw6_local_deliver(skb, nexthdr);
387	ipprot = rcu_dereference(inet6_protos[nexthdr]);
388	if (ipprot) {
389		int ret;
390
391		if (have_final) {
392			if (!(ipprot->flags & INET6_PROTO_FINAL)) {
393				/* Once we've seen a final protocol don't
394				 * allow encapsulation on any non-final
395				 * ones. This allows foo in UDP encapsulation
396				 * to work.
397				 */
398				goto discard;
399			}
400		} else if (ipprot->flags & INET6_PROTO_FINAL) {
401			const struct ipv6hdr *hdr;
402			int sdif = inet6_sdif(skb);
403			struct net_device *dev;
404
405			/* Only do this once for first final protocol */
406			have_final = true;
407
408
409			skb_postpull_rcsum(skb, skb_network_header(skb),
410					   skb_network_header_len(skb));
411			hdr = ipv6_hdr(skb);
412
413			/* skb->dev passed may be master dev for vrfs. */
414			if (sdif) {
415				dev = dev_get_by_index_rcu(net, sdif);
416				if (!dev)
417					goto discard;
418			} else {
419				dev = skb->dev;
420			}
421
422			if (ipv6_addr_is_multicast(&hdr->daddr) &&
423			    !ipv6_chk_mcast_addr(dev, &hdr->daddr,
424						 &hdr->saddr) &&
425			    !ipv6_is_mld(skb, nexthdr, skb_network_header_len(skb))) {
426				SKB_DR_SET(reason, IP_INADDRERRORS);
427				goto discard;
428			}
429		}
430		if (!(ipprot->flags & INET6_PROTO_NOPOLICY)) {
431			if (!xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb)) {
432				SKB_DR_SET(reason, XFRM_POLICY);
433				goto discard;
434			}
435			nf_reset_ct(skb);
436		}
437
438		ret = INDIRECT_CALL_2(ipprot->handler, tcp_v6_rcv, udpv6_rcv,
439				      skb);
440		if (ret > 0) {
441			if (ipprot->flags & INET6_PROTO_FINAL) {
442				/* Not an extension header, most likely UDP
443				 * encapsulation. Use return value as nexthdr
444				 * protocol not nhoff (which presumably is
445				 * not set by handler).
446				 */
447				nexthdr = ret;
448				goto resubmit_final;
449			} else {
450				goto resubmit;
451			}
452		} else if (ret == 0) {
453			__IP6_INC_STATS(net, idev, IPSTATS_MIB_INDELIVERS);
454		}
455	} else {
456		if (!raw) {
457			if (xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb)) {
458				__IP6_INC_STATS(net, idev,
459						IPSTATS_MIB_INUNKNOWNPROTOS);
460				icmpv6_send(skb, ICMPV6_PARAMPROB,
461					    ICMPV6_UNK_NEXTHDR, nhoff);
462				SKB_DR_SET(reason, IP_NOPROTO);
463			} else {
464				SKB_DR_SET(reason, XFRM_POLICY);
465			}
466			kfree_skb_reason(skb, reason);
467		} else {
468			__IP6_INC_STATS(net, idev, IPSTATS_MIB_INDELIVERS);
469			consume_skb(skb);
470		}
471	}
472	return;
473
474discard:
475	__IP6_INC_STATS(net, idev, IPSTATS_MIB_INDISCARDS);
476	kfree_skb_reason(skb, reason);
477}
478
479static int ip6_input_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
480{
481	skb_clear_delivery_time(skb);
482	rcu_read_lock();
483	ip6_protocol_deliver_rcu(net, skb, 0, false);
484	rcu_read_unlock();
485
486	return 0;
487}
488
489
490int ip6_input(struct sk_buff *skb)
491{
492	return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_IN,
493		       dev_net(skb->dev), NULL, skb, skb->dev, NULL,
494		       ip6_input_finish);
495}
496EXPORT_SYMBOL_GPL(ip6_input);
497
498int ip6_mc_input(struct sk_buff *skb)
499{
500	int sdif = inet6_sdif(skb);
501	const struct ipv6hdr *hdr;
502	struct net_device *dev;
503	bool deliver;
504
505	__IP6_UPD_PO_STATS(dev_net(skb_dst(skb)->dev),
506			 __in6_dev_get_safely(skb->dev), IPSTATS_MIB_INMCAST,
507			 skb->len);
508
509	/* skb->dev passed may be master dev for vrfs. */
510	if (sdif) {
511		rcu_read_lock();
512		dev = dev_get_by_index_rcu(dev_net(skb->dev), sdif);
513		if (!dev) {
514			rcu_read_unlock();
515			kfree_skb(skb);
516			return -ENODEV;
517		}
518	} else {
519		dev = skb->dev;
520	}
521
522	hdr = ipv6_hdr(skb);
523	deliver = ipv6_chk_mcast_addr(dev, &hdr->daddr, NULL);
524	if (sdif)
525		rcu_read_unlock();
526
527#ifdef CONFIG_IPV6_MROUTE
528	/*
529	 *      IPv6 multicast router mode is now supported ;)
530	 */
531	if (atomic_read(&dev_net(skb->dev)->ipv6.devconf_all->mc_forwarding) &&
532	    !(ipv6_addr_type(&hdr->daddr) &
533	      (IPV6_ADDR_LOOPBACK|IPV6_ADDR_LINKLOCAL)) &&
534	    likely(!(IP6CB(skb)->flags & IP6SKB_FORWARDED))) {
535		/*
536		 * Okay, we try to forward - split and duplicate
537		 * packets.
538		 */
539		struct sk_buff *skb2;
540		struct inet6_skb_parm *opt = IP6CB(skb);
541
542		/* Check for MLD */
543		if (unlikely(opt->flags & IP6SKB_ROUTERALERT)) {
544			/* Check if this is a mld message */
545			u8 nexthdr = hdr->nexthdr;
546			__be16 frag_off;
547			int offset;
548
549			/* Check if the value of Router Alert
550			 * is for MLD (0x0000).
551			 */
552			if (opt->ra == htons(IPV6_OPT_ROUTERALERT_MLD)) {
553				deliver = false;
554
555				if (!ipv6_ext_hdr(nexthdr)) {
556					/* BUG */
557					goto out;
558				}
559				offset = ipv6_skip_exthdr(skb, sizeof(*hdr),
560							  &nexthdr, &frag_off);
561				if (offset < 0)
562					goto out;
563
564				if (ipv6_is_mld(skb, nexthdr, offset))
565					deliver = true;
566
567				goto out;
568			}
569			/* unknown RA - process it normally */
570		}
571
572		if (deliver)
573			skb2 = skb_clone(skb, GFP_ATOMIC);
574		else {
575			skb2 = skb;
576			skb = NULL;
577		}
578
579		if (skb2) {
580			ip6_mr_input(skb2);
581		}
582	}
583out:
584#endif
585	if (likely(deliver))
586		ip6_input(skb);
587	else {
588		/* discard */
589		kfree_skb(skb);
590	}
591
592	return 0;
593}
594