1// SPDX-License-Identifier: GPL-2.0-only
2/* Copyright (C) 2010: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
3 * Copyright (C) 2015: Linus Lüssing <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, len: 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, start: offset, nexthdrp: &nexthdr, frag_offp: &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(addr: &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(a: &mld->mld_mca) &&
100 !ipv6_addr_is_ll_all_nodes(addr: &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 skb_chkf: ipv6_mc_validate_checksum);
145 if (!skb_chk)
146 return -EINVAL;
147
148 if (skb_chk != skb)
149 kfree_skb(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