net/ipv6/mcast_snoop.c

   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
  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);