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Linux/net/ipv6/mcast_snoop.c

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  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 
 14 static 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 
 37 static 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 
 64 static 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 
 73 static 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 
106 static 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 -EINVAL;
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 -ENOMSG;
126         }
127 }
128 
129 static inline __sum16 ipv6_mc_validate_checksum(struct sk_buff *skb)
130 {
131         return skb_checksum_validate(skb, IPPROTO_ICMPV6, ip6_compute_pseudo);
132 }
133 
134 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 EXPORT_SYMBOL(ipv6_mc_check_icmpv6);
154 
155 /**
156  * ipv6_mc_check_mld - checks whether this is a sane MLD packet
157  * @skb: the skb to validate
158  *
159  * Checks whether an IPv6 packet is a valid MLD packet. If so sets
160  * skb transport header accordingly and returns zero.
161  *
162  * -EINVAL: A broken packet was detected, i.e. it violates some internet
163  *  standard
164  * -ENOMSG: IP header validation succeeded but it is not an MLD packet.
165  * -ENOMEM: A memory allocation failure happened.
166  *
167  * Caller needs to set the skb network header and free any returned skb if it
168  * differs from the provided skb.
169  */
170 int ipv6_mc_check_mld(struct sk_buff *skb)
171 {
172         int ret;
173 
174         ret = ipv6_mc_check_ip6hdr(skb);
175         if (ret < 0)
176                 return ret;
177 
178         ret = ipv6_mc_check_exthdrs(skb);
179         if (ret < 0)
180                 return ret;
181 
182         ret = ipv6_mc_check_icmpv6(skb);
183         if (ret < 0)
184                 return ret;
185 
186         return ipv6_mc_check_mld_msg(skb);
187 }
188 EXPORT_SYMBOL(ipv6_mc_check_mld);
189 

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