summaryrefslogtreecommitdiffstats
path: root/net/ipv6/mcast_snoop.c
blob: df8afe5ab31e4b8e75bf2fbf844f8b3e798edbba (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
/* Copyright (C) 2010: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
 * Copyright (C) 2015: Linus Lüssing <linus.luessing@c0d3.blue>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see <http://www.gnu.org/licenses/>.
 *
 *
 * Based on the MLD support added to br_multicast.c by YOSHIFUJI Hideaki.
 */

#include <linux/skbuff.h>
#include <net/ipv6.h>
#include <net/mld.h>
#include <net/addrconf.h>
#include <net/ip6_checksum.h>

static int ipv6_mc_check_ip6hdr(struct sk_buff *skb)
{
	const struct ipv6hdr *ip6h;
	unsigned int len;
	unsigned int offset = skb_network_offset(skb) + sizeof(*ip6h);

	if (!pskb_may_pull(skb, offset))
		return -EINVAL;

	ip6h = ipv6_hdr(skb);

	if (ip6h->version != 6)
		return -EINVAL;

	len = offset + ntohs(ip6h->payload_len);
	if (skb->len < len || len <= offset)
		return -EINVAL;

	return 0;
}

static int ipv6_mc_check_exthdrs(struct sk_buff *skb)
{
	const struct ipv6hdr *ip6h;
	int offset;
	u8 nexthdr;
	__be16 frag_off;

	ip6h = ipv6_hdr(skb);

	if (ip6h->nexthdr != IPPROTO_HOPOPTS)
		return -ENOMSG;

	nexthdr = ip6h->nexthdr;
	offset = skb_network_offset(skb) + sizeof(*ip6h);
	offset = ipv6_skip_exthdr(skb, offset, &nexthdr, &frag_off);

	if (offset < 0)
		return -EINVAL;

	if (nexthdr != IPPROTO_ICMPV6)
		return -ENOMSG;

	skb_set_transport_header(skb, offset);

	return 0;
}

static int ipv6_mc_check_mld_reportv2(struct sk_buff *skb)
{
	unsigned int len = skb_transport_offset(skb);

	len += sizeof(struct mld2_report);

	return pskb_may_pull(skb, len) ? 0 : -EINVAL;
}

static int ipv6_mc_check_mld_query(struct sk_buff *skb)
{
	struct mld_msg *mld;
	unsigned int len = skb_transport_offset(skb);

	/* RFC2710+RFC3810 (MLDv1+MLDv2) require link-local source addresses */
	if (!(ipv6_addr_type(&ipv6_hdr(skb)->saddr) & IPV6_ADDR_LINKLOCAL))
		return -EINVAL;

	len += sizeof(struct mld_msg);
	if (skb->len < len)
		return -EINVAL;

	/* MLDv1? */
	if (skb->len != len) {
		/* or MLDv2? */
		len += sizeof(struct mld2_query) - sizeof(struct mld_msg);
		if (skb->len < len || !pskb_may_pull(skb, len))
			return -EINVAL;
	}

	mld = (struct mld_msg *)skb_transport_header(skb);

	/* RFC2710+RFC3810 (MLDv1+MLDv2) require the multicast link layer
	 * all-nodes destination address (ff02::1) for general queries
	 */
	if (ipv6_addr_any(&mld->mld_mca) &&
	    !ipv6_addr_is_ll_all_nodes(&ipv6_hdr(skb)->daddr))
		return -EINVAL;

	return 0;
}

static int ipv6_mc_check_mld_msg(struct sk_buff *skb)
{
	struct mld_msg *mld = (struct mld_msg *)skb_transport_header(skb);

	switch (mld->mld_type) {
	case ICMPV6_MGM_REDUCTION:
	case ICMPV6_MGM_REPORT:
		/* fall through */
		return 0;
	case ICMPV6_MLD2_REPORT:
		return ipv6_mc_check_mld_reportv2(skb);
	case ICMPV6_MGM_QUERY:
		return ipv6_mc_check_mld_query(skb);
	default:
		return -ENOMSG;
	}
}

static inline __sum16 ipv6_mc_validate_checksum(struct sk_buff *skb)
{
	return skb_checksum_validate(skb, IPPROTO_ICMPV6, ip6_compute_pseudo);
}

static int __ipv6_mc_check_mld(struct sk_buff *skb,
			       struct sk_buff **skb_trimmed)

{
	struct sk_buff *skb_chk = NULL;
	unsigned int transport_len;
	unsigned int len = skb_transport_offset(skb) + sizeof(struct mld_msg);
	int ret;

	transport_len = ntohs(ipv6_hdr(skb)->payload_len);
	transport_len -= skb_transport_offset(skb) - sizeof(struct ipv6hdr);

	skb_get(skb);
	skb_chk = skb_checksum_trimmed(skb, transport_len,
				       ipv6_mc_validate_checksum);
	if (!skb_chk)
		return -EINVAL;

	if (!pskb_may_pull(skb_chk, len)) {
		kfree_skb(skb_chk);
		return -EINVAL;
	}

	ret = ipv6_mc_check_mld_msg(skb_chk);
	if (ret) {
		kfree_skb(skb_chk);
		return ret;
	}

	if (skb_trimmed)
		*skb_trimmed = skb_chk;
	else
		kfree_skb(skb_chk);

	return 0;
}

/**
 * ipv6_mc_check_mld - checks whether this is a sane MLD packet
 * @skb: the skb to validate
 * @skb_trimmed: to store an skb pointer trimmed to IPv6 packet tail (optional)
 *
 * Checks whether an IPv6 packet is a valid MLD packet. If so sets
 * skb network and transport headers accordingly and returns zero.
 *
 * -EINVAL: A broken packet was detected, i.e. it violates some internet
 *  standard
 * -ENOMSG: IP header validation succeeded but it is not an MLD packet.
 * -ENOMEM: A memory allocation failure happened.
 *
 * Optionally, an skb pointer might be provided via skb_trimmed (or set it
 * to NULL): After parsing an MLD packet successfully it will point to
 * an skb which has its tail aligned to the IP packet end. This might
 * either be the originally provided skb or a trimmed, cloned version if
 * the skb frame had data beyond the IP packet. A cloned skb allows us
 * to leave the original skb and its full frame unchanged (which might be
 * desirable for layer 2 frame jugglers).
 *
 * The caller needs to release a reference count from any returned skb_trimmed.
 */
int ipv6_mc_check_mld(struct sk_buff *skb, struct sk_buff **skb_trimmed)
{
	int ret;

	ret = ipv6_mc_check_ip6hdr(skb);
	if (ret < 0)
		return ret;

	ret = ipv6_mc_check_exthdrs(skb);
	if (ret < 0)
		return ret;

	return __ipv6_mc_check_mld(skb, skb_trimmed);
}
EXPORT_SYMBOL(ipv6_mc_check_mld);