1// SPDX-License-Identifier: GPL-2.0-only
2/* Copyright (C) 2010: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
3 * Copyright (C) 2015: Linus L��ssing <linus.luessing@c0d3.blue>
4 *
5 * Based on the MLD support added to br_multicast.c by YOSHIFUJI Hideaki.
6 */
7
8#include <linux/skbuff.h>
9#include <net/ipv6.h>
10#include <net/mld.h>
11#include <net/addrconf.h>
12#include <net/ip6_checksum.h>
13
14static int ipv6_mc_check_ip6hdr(struct sk_buff *skb)
15{
16	const struct ipv6hdr *ip6h;
17	unsigned int len;
18	unsigned int offset = skb_network_offset(skb) + sizeof(*ip6h);
19
20	if (!pskb_may_pull(skb, offset))
21		return -EINVAL;
22
23	ip6h = ipv6_hdr(skb);
24
25	if (ip6h->version != 6)
26		return -EINVAL;
27
28	len = offset + ntohs(ip6h->payload_len);
29	if (skb->len < len || len <= offset)
30		return -EINVAL;
31
32	skb_set_transport_header(skb, offset);
33
34	return 0;
35}
36
37static int ipv6_mc_check_exthdrs(struct sk_buff *skb)
38{
39	const struct ipv6hdr *ip6h;
40	int offset;
41	u8 nexthdr;
42	__be16 frag_off;
43
44	ip6h = ipv6_hdr(skb);
45
46	if (ip6h->nexthdr != IPPROTO_HOPOPTS)
47		return -ENOMSG;
48
49	nexthdr = ip6h->nexthdr;
50	offset = skb_network_offset(skb) + sizeof(*ip6h);
51	offset = ipv6_skip_exthdr(skb, offset, &nexthdr, &frag_off);
52
53	if (offset < 0)
54		return -EINVAL;
55
56	if (nexthdr != IPPROTO_ICMPV6)
57		return -ENOMSG;
58
59	skb_set_transport_header(skb, offset);
60
61	return 0;
62}
63
64static int ipv6_mc_check_mld_reportv2(struct sk_buff *skb)
65{
66	unsigned int len = skb_transport_offset(skb);
67
68	len += sizeof(struct mld2_report);
69
70	return ipv6_mc_may_pull(skb, len) ? 0 : -EINVAL;
71}
72
73static int ipv6_mc_check_mld_query(struct sk_buff *skb)
74{
75	unsigned int transport_len = ipv6_transport_len(skb);
76	struct mld_msg *mld;
77	unsigned int len;
78
79	/* RFC2710+RFC3810 (MLDv1+MLDv2) require link-local source addresses */
80	if (!(ipv6_addr_type(&ipv6_hdr(skb)->saddr) & IPV6_ADDR_LINKLOCAL))
81		return -EINVAL;
82
83	/* MLDv1? */
84	if (transport_len != sizeof(struct mld_msg)) {
85		/* or MLDv2? */
86		if (transport_len < sizeof(struct mld2_query))
87			return -EINVAL;
88
89		len = skb_transport_offset(skb) + sizeof(struct mld2_query);
90		if (!ipv6_mc_may_pull(skb, len))
91			return -EINVAL;
92	}
93
94	mld = (struct mld_msg *)skb_transport_header(skb);
95
96	/* RFC2710+RFC3810 (MLDv1+MLDv2) require the multicast link layer
97	 * all-nodes destination address (ff02::1) for general queries
98	 */
99	if (ipv6_addr_any(&mld->mld_mca) &&
100	    !ipv6_addr_is_ll_all_nodes(&ipv6_hdr(skb)->daddr))
101		return -EINVAL;
102
103	return 0;
104}
105
106static int ipv6_mc_check_mld_msg(struct sk_buff *skb)
107{
108	unsigned int len = skb_transport_offset(skb) + sizeof(struct mld_msg);
109	struct mld_msg *mld;
110
111	if (!ipv6_mc_may_pull(skb, len))
112		return -ENODATA;
113
114	mld = (struct mld_msg *)skb_transport_header(skb);
115
116	switch (mld->mld_type) {
117	case ICMPV6_MGM_REDUCTION:
118	case ICMPV6_MGM_REPORT:
119		return 0;
120	case ICMPV6_MLD2_REPORT:
121		return ipv6_mc_check_mld_reportv2(skb);
122	case ICMPV6_MGM_QUERY:
123		return ipv6_mc_check_mld_query(skb);
124	default:
125		return -ENODATA;
126	}
127}
128
129static inline __sum16 ipv6_mc_validate_checksum(struct sk_buff *skb)
130{
131	return skb_checksum_validate(skb, IPPROTO_ICMPV6, ip6_compute_pseudo);
132}
133
134static int ipv6_mc_check_icmpv6(struct sk_buff *skb)
135{
136	unsigned int len = skb_transport_offset(skb) + sizeof(struct icmp6hdr);
137	unsigned int transport_len = ipv6_transport_len(skb);
138	struct sk_buff *skb_chk;
139
140	if (!ipv6_mc_may_pull(skb, len))
141		return -EINVAL;
142
143	skb_chk = skb_checksum_trimmed(skb, transport_len,
144				       ipv6_mc_validate_checksum);
145	if (!skb_chk)
146		return -EINVAL;
147
148	if (skb_chk != skb)
149		kfree_skb(skb_chk);
150
151	return 0;
152}
153
154/**
155 * ipv6_mc_check_mld - checks whether this is a sane MLD packet
156 * @skb: the skb to validate
157 *
158 * Checks whether an IPv6 packet is a valid MLD packet. If so sets
159 * skb transport header accordingly and returns zero.
160 *
161 * -EINVAL: A broken packet was detected, i.e. it violates some internet
162 *  standard
163 * -ENOMSG: IP header validation succeeded but it is not an ICMPv6 packet
164 *  with a hop-by-hop option.
165 * -ENODATA: IP+ICMPv6 header with hop-by-hop option validation succeeded
166 *  but it is not an MLD packet.
167 * -ENOMEM: A memory allocation failure happened.
168 *
169 * Caller needs to set the skb network header and free any returned skb if it
170 * differs from the provided skb.
171 */
172int ipv6_mc_check_mld(struct sk_buff *skb)
173{
174	int ret;
175
176	ret = ipv6_mc_check_ip6hdr(skb);
177	if (ret < 0)
178		return ret;
179
180	ret = ipv6_mc_check_exthdrs(skb);
181	if (ret < 0)
182		return ret;
183
184	ret = ipv6_mc_check_icmpv6(skb);
185	if (ret < 0)
186		return ret;
187
188	return ipv6_mc_check_mld_msg(skb);
189}
190EXPORT_SYMBOL(ipv6_mc_check_mld);
191