xref: /openbmc/linux/net/ipv6/ip6_input.c (revision 8bd1369b) 
1 /*
2  *	IPv6 input
3  *	Linux INET6 implementation
4  *
5  *	Authors:
6  *	Pedro Roque		<roque@di.fc.ul.pt>
7  *	Ian P. Morris		<I.P.Morris@soton.ac.uk>
8  *
9  *	Based in linux/net/ipv4/ip_input.c
10  *
11  *	This program is free software; you can redistribute it and/or
12  *      modify it under the terms of the GNU General Public License
13  *      as published by the Free Software Foundation; either version
14  *      2 of the License, or (at your option) any later version.
15  */
16 /* Changes
17  *
18  *	Mitsuru KANDA @USAGI and
19  *	YOSHIFUJI Hideaki @USAGI: Remove ipv6_parse_exthdrs().
20  */
21 
22 #include <linux/errno.h>
23 #include <linux/types.h>
24 #include <linux/socket.h>
25 #include <linux/sockios.h>
26 #include <linux/net.h>
27 #include <linux/netdevice.h>
28 #include <linux/in6.h>
29 #include <linux/icmpv6.h>
30 #include <linux/mroute6.h>
31 #include <linux/slab.h>
32 
33 #include <linux/netfilter.h>
34 #include <linux/netfilter_ipv6.h>
35 
36 #include <net/sock.h>
37 #include <net/snmp.h>
38 
39 #include <net/ipv6.h>
40 #include <net/protocol.h>
41 #include <net/transp_v6.h>
42 #include <net/rawv6.h>
43 #include <net/ndisc.h>
44 #include <net/ip6_route.h>
45 #include <net/addrconf.h>
46 #include <net/xfrm.h>
47 #include <net/inet_ecn.h>
48 #include <net/dst_metadata.h>
49 
50 int ip6_rcv_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
51 {
52 	void (*edemux)(struct sk_buff *skb);
53 
54 	/* if ingress device is enslaved to an L3 master device pass the
55 	 * skb to its handler for processing
56 	 */
57 	skb = l3mdev_ip6_rcv(skb);
58 	if (!skb)
59 		return NET_RX_SUCCESS;
60 
61 	if (net->ipv4.sysctl_ip_early_demux && !skb_dst(skb) && skb->sk == NULL) {
62 		const struct inet6_protocol *ipprot;
63 
64 		ipprot = rcu_dereference(inet6_protos[ipv6_hdr(skb)->nexthdr]);
65 		if (ipprot && (edemux = READ_ONCE(ipprot->early_demux)))
66 			edemux(skb);
67 	}
68 	if (!skb_valid_dst(skb))
69 		ip6_route_input(skb);
70 
71 	return dst_input(skb);
72 }
73 
74 int ipv6_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev)
75 {
76 	const struct ipv6hdr *hdr;
77 	u32 pkt_len;
78 	struct inet6_dev *idev;
79 	struct net *net = dev_net(skb->dev);
80 
81 	if (skb->pkt_type == PACKET_OTHERHOST) {
82 		kfree_skb(skb);
83 		return NET_RX_DROP;
84 	}
85 
86 	rcu_read_lock();
87 
88 	idev = __in6_dev_get(skb->dev);
89 
90 	__IP6_UPD_PO_STATS(net, idev, IPSTATS_MIB_IN, skb->len);
91 
92 	if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL ||
93 	    !idev || unlikely(idev->cnf.disable_ipv6)) {
94 		__IP6_INC_STATS(net, idev, IPSTATS_MIB_INDISCARDS);
95 		goto drop;
96 	}
97 
98 	memset(IP6CB(skb), 0, sizeof(struct inet6_skb_parm));
99 
100 	/*
101 	 * Store incoming device index. When the packet will
102 	 * be queued, we cannot refer to skb->dev anymore.
103 	 *
104 	 * BTW, when we send a packet for our own local address on a
105 	 * non-loopback interface (e.g. ethX), it is being delivered
106 	 * via the loopback interface (lo) here; skb->dev = loopback_dev.
107 	 * It, however, should be considered as if it is being
108 	 * arrived via the sending interface (ethX), because of the
109 	 * nature of scoping architecture. --yoshfuji
110 	 */
111 	IP6CB(skb)->iif = skb_valid_dst(skb) ? ip6_dst_idev(skb_dst(skb))->dev->ifindex : dev->ifindex;
112 
113 	if (unlikely(!pskb_may_pull(skb, sizeof(*hdr))))
114 		goto err;
115 
116 	hdr = ipv6_hdr(skb);
117 
118 	if (hdr->version != 6)
119 		goto err;
120 
121 	__IP6_ADD_STATS(net, idev,
122 			IPSTATS_MIB_NOECTPKTS +
123 				(ipv6_get_dsfield(hdr) & INET_ECN_MASK),
124 			max_t(unsigned short, 1, skb_shinfo(skb)->gso_segs));
125 	/*
126 	 * RFC4291 2.5.3
127 	 * The loopback address must not be used as the source address in IPv6
128 	 * packets that are sent outside of a single node. [..]
129 	 * A packet received on an interface with a destination address
130 	 * of loopback must be dropped.
131 	 */
132 	if ((ipv6_addr_loopback(&hdr->saddr) ||
133 	     ipv6_addr_loopback(&hdr->daddr)) &&
134 	     !(dev->flags & IFF_LOOPBACK))
135 		goto err;
136 
137 	/* RFC4291 Errata ID: 3480
138 	 * Interface-Local scope spans only a single interface on a
139 	 * node and is useful only for loopback transmission of
140 	 * multicast.  Packets with interface-local scope received
141 	 * from another node must be discarded.
142 	 */
143 	if (!(skb->pkt_type == PACKET_LOOPBACK ||
144 	      dev->flags & IFF_LOOPBACK) &&
145 	    ipv6_addr_is_multicast(&hdr->daddr) &&
146 	    IPV6_ADDR_MC_SCOPE(&hdr->daddr) == 1)
147 		goto err;
148 
149 	/* If enabled, drop unicast packets that were encapsulated in link-layer
150 	 * multicast or broadcast to protected against the so-called "hole-196"
151 	 * attack in 802.11 wireless.
152 	 */
153 	if (!ipv6_addr_is_multicast(&hdr->daddr) &&
154 	    (skb->pkt_type == PACKET_BROADCAST ||
155 	     skb->pkt_type == PACKET_MULTICAST) &&
156 	    idev->cnf.drop_unicast_in_l2_multicast)
157 		goto err;
158 
159 	/* RFC4291 2.7
160 	 * Nodes must not originate a packet to a multicast address whose scope
161 	 * field contains the reserved value 0; if such a packet is received, it
162 	 * must be silently dropped.
163 	 */
164 	if (ipv6_addr_is_multicast(&hdr->daddr) &&
165 	    IPV6_ADDR_MC_SCOPE(&hdr->daddr) == 0)
166 		goto err;
167 
168 	/*
169 	 * RFC4291 2.7
170 	 * Multicast addresses must not be used as source addresses in IPv6
171 	 * packets or appear in any Routing header.
172 	 */
173 	if (ipv6_addr_is_multicast(&hdr->saddr))
174 		goto err;
175 
176 	skb->transport_header = skb->network_header + sizeof(*hdr);
177 	IP6CB(skb)->nhoff = offsetof(struct ipv6hdr, nexthdr);
178 
179 	pkt_len = ntohs(hdr->payload_len);
180 
181 	/* pkt_len may be zero if Jumbo payload option is present */
182 	if (pkt_len || hdr->nexthdr != NEXTHDR_HOP) {
183 		if (pkt_len + sizeof(struct ipv6hdr) > skb->len) {
184 			__IP6_INC_STATS(net,
185 					idev, IPSTATS_MIB_INTRUNCATEDPKTS);
186 			goto drop;
187 		}
188 		if (pskb_trim_rcsum(skb, pkt_len + sizeof(struct ipv6hdr))) {
189 			__IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
190 			goto drop;
191 		}
192 		hdr = ipv6_hdr(skb);
193 	}
194 
195 	if (hdr->nexthdr == NEXTHDR_HOP) {
196 		if (ipv6_parse_hopopts(skb) < 0) {
197 			__IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
198 			rcu_read_unlock();
199 			return NET_RX_DROP;
200 		}
201 	}
202 
203 	rcu_read_unlock();
204 
205 	/* Must drop socket now because of tproxy. */
206 	skb_orphan(skb);
207 
208 	return NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING,
209 		       net, NULL, skb, dev, NULL,
210 		       ip6_rcv_finish);
211 err:
212 	__IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
213 drop:
214 	rcu_read_unlock();
215 	kfree_skb(skb);
216 	return NET_RX_DROP;
217 }
218 
219 /*
220  *	Deliver the packet to the host
221  */
222 
223 
224 static int ip6_input_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
225 {
226 	const struct inet6_protocol *ipprot;
227 	struct inet6_dev *idev;
228 	unsigned int nhoff;
229 	int nexthdr;
230 	bool raw;
231 	bool have_final = false;
232 
233 	/*
234 	 *	Parse extension headers
235 	 */
236 
237 	rcu_read_lock();
238 resubmit:
239 	idev = ip6_dst_idev(skb_dst(skb));
240 	if (!pskb_pull(skb, skb_transport_offset(skb)))
241 		goto discard;
242 	nhoff = IP6CB(skb)->nhoff;
243 	nexthdr = skb_network_header(skb)[nhoff];
244 
245 resubmit_final:
246 	raw = raw6_local_deliver(skb, nexthdr);
247 	ipprot = rcu_dereference(inet6_protos[nexthdr]);
248 	if (ipprot) {
249 		int ret;
250 
251 		if (have_final) {
252 			if (!(ipprot->flags & INET6_PROTO_FINAL)) {
253 				/* Once we've seen a final protocol don't
254 				 * allow encapsulation on any non-final
255 				 * ones. This allows foo in UDP encapsulation
256 				 * to work.
257 				 */
258 				goto discard;
259 			}
260 		} else if (ipprot->flags & INET6_PROTO_FINAL) {
261 			const struct ipv6hdr *hdr;
262 
263 			/* Only do this once for first final protocol */
264 			have_final = true;
265 
266 			/* Free reference early: we don't need it any more,
267 			   and it may hold ip_conntrack module loaded
268 			   indefinitely. */
269 			nf_reset(skb);
270 
271 			skb_postpull_rcsum(skb, skb_network_header(skb),
272 					   skb_network_header_len(skb));
273 			hdr = ipv6_hdr(skb);
274 			if (ipv6_addr_is_multicast(&hdr->daddr) &&
275 			    !ipv6_chk_mcast_addr(skb->dev, &hdr->daddr,
276 			    &hdr->saddr) &&
277 			    !ipv6_is_mld(skb, nexthdr, skb_network_header_len(skb)))
278 				goto discard;
279 		}
280 		if (!(ipprot->flags & INET6_PROTO_NOPOLICY) &&
281 		    !xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb))
282 			goto discard;
283 
284 		ret = ipprot->handler(skb);
285 		if (ret > 0) {
286 			if (ipprot->flags & INET6_PROTO_FINAL) {
287 				/* Not an extension header, most likely UDP
288 				 * encapsulation. Use return value as nexthdr
289 				 * protocol not nhoff (which presumably is
290 				 * not set by handler).
291 				 */
292 				nexthdr = ret;
293 				goto resubmit_final;
294 			} else {
295 				goto resubmit;
296 			}
297 		} else if (ret == 0) {
298 			__IP6_INC_STATS(net, idev, IPSTATS_MIB_INDELIVERS);
299 		}
300 	} else {
301 		if (!raw) {
302 			if (xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb)) {
303 				__IP6_INC_STATS(net, idev,
304 						IPSTATS_MIB_INUNKNOWNPROTOS);
305 				icmpv6_send(skb, ICMPV6_PARAMPROB,
306 					    ICMPV6_UNK_NEXTHDR, nhoff);
307 			}
308 			kfree_skb(skb);
309 		} else {
310 			__IP6_INC_STATS(net, idev, IPSTATS_MIB_INDELIVERS);
311 			consume_skb(skb);
312 		}
313 	}
314 	rcu_read_unlock();
315 	return 0;
316 
317 discard:
318 	__IP6_INC_STATS(net, idev, IPSTATS_MIB_INDISCARDS);
319 	rcu_read_unlock();
320 	kfree_skb(skb);
321 	return 0;
322 }
323 
324 
325 int ip6_input(struct sk_buff *skb)
326 {
327 	return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_IN,
328 		       dev_net(skb->dev), NULL, skb, skb->dev, NULL,
329 		       ip6_input_finish);
330 }
331 EXPORT_SYMBOL_GPL(ip6_input);
332 
333 int ip6_mc_input(struct sk_buff *skb)
334 {
335 	const struct ipv6hdr *hdr;
336 	bool deliver;
337 
338 	__IP6_UPD_PO_STATS(dev_net(skb_dst(skb)->dev),
339 			 __in6_dev_get_safely(skb->dev), IPSTATS_MIB_INMCAST,
340 			 skb->len);
341 
342 	hdr = ipv6_hdr(skb);
343 	deliver = ipv6_chk_mcast_addr(skb->dev, &hdr->daddr, NULL);
344 
345 #ifdef CONFIG_IPV6_MROUTE
346 	/*
347 	 *      IPv6 multicast router mode is now supported ;)
348 	 */
349 	if (dev_net(skb->dev)->ipv6.devconf_all->mc_forwarding &&
350 	    !(ipv6_addr_type(&hdr->daddr) &
351 	      (IPV6_ADDR_LOOPBACK|IPV6_ADDR_LINKLOCAL)) &&
352 	    likely(!(IP6CB(skb)->flags & IP6SKB_FORWARDED))) {
353 		/*
354 		 * Okay, we try to forward - split and duplicate
355 		 * packets.
356 		 */
357 		struct sk_buff *skb2;
358 		struct inet6_skb_parm *opt = IP6CB(skb);
359 
360 		/* Check for MLD */
361 		if (unlikely(opt->flags & IP6SKB_ROUTERALERT)) {
362 			/* Check if this is a mld message */
363 			u8 nexthdr = hdr->nexthdr;
364 			__be16 frag_off;
365 			int offset;
366 
367 			/* Check if the value of Router Alert
368 			 * is for MLD (0x0000).
369 			 */
370 			if (opt->ra == htons(IPV6_OPT_ROUTERALERT_MLD)) {
371 				deliver = false;
372 
373 				if (!ipv6_ext_hdr(nexthdr)) {
374 					/* BUG */
375 					goto out;
376 				}
377 				offset = ipv6_skip_exthdr(skb, sizeof(*hdr),
378 							  &nexthdr, &frag_off);
379 				if (offset < 0)
380 					goto out;
381 
382 				if (ipv6_is_mld(skb, nexthdr, offset))
383 					deliver = true;
384 
385 				goto out;
386 			}
387 			/* unknown RA - process it normally */
388 		}
389 
390 		if (deliver)
391 			skb2 = skb_clone(skb, GFP_ATOMIC);
392 		else {
393 			skb2 = skb;
394 			skb = NULL;
395 		}
396 
397 		if (skb2) {
398 			ip6_mr_input(skb2);
399 		}
400 	}
401 out:
402 #endif
403 	if (likely(deliver))
404 		ip6_input(skb);
405 	else {
406 		/* discard */
407 		kfree_skb(skb);
408 	}
409 
410 	return 0;
411 }
412