net/ipv6/mcast_snoop.c

   1 /* Copyright (C) 2010: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
   2  * Copyright (C) 2015: Linus Lüssing <linus.luessing@c0d3.blue>
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of version 2 of the GNU General Public
   6  * License as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful, but
   9  * WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License
  14  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  15  *
  16  *
  17  * Based on the MLD support added to br_multicast.c by YOSHIFUJI Hideaki.
  18  */
  19
  20 #include <linux/skbuff.h>
  21 #include <net/ipv6.h>
  22 #include <net/mld.h>
  23 #include <net/addrconf.h>
  24 #include <net/ip6_checksum.h>
  25
  26 static int ipv6_mc_check_ip6hdr(struct sk_buff *skb)
  27 {
  28         const struct ipv6hdr *ip6h;
  29         unsigned int len;
  30         unsigned int offset = skb_network_offset(skb) + sizeof(*ip6h);
  31
  32         if (!pskb_may_pull(skb, offset))
  33                 return -EINVAL;
  34
  35         ip6h = ipv6_hdr(skb);
  36
  37         if (ip6h->version != 6)
  38                 return -EINVAL;
  39
  40         len = offset + ntohs(ip6h->payload_len);
  41         if (skb->len < len || len <= offset)
  42                 return -EINVAL;
  43
  44         return 0;
  45 }
  46
  47 static int ipv6_mc_check_exthdrs(struct sk_buff *skb)
  48 {
  49         const struct ipv6hdr *ip6h;
  50         int offset;
  51         u8 nexthdr;
  52         __be16 frag_off;
  53
  54         ip6h = ipv6_hdr(skb);
  55
  56         if (ip6h->nexthdr != IPPROTO_HOPOPTS)
  57                 return -ENOMSG;
  58
  59         nexthdr = ip6h->nexthdr;
  60         offset = skb_network_offset(skb) + sizeof(*ip6h);
  61         offset = ipv6_skip_exthdr(skb, offset, &nexthdr, &frag_off);
  62
  63         if (offset < 0)
  64                 return -EINVAL;
  65
  66         if (nexthdr != IPPROTO_ICMPV6)
  67                 return -ENOMSG;
  68
  69         skb_set_transport_header(skb, offset);
  70
  71         return 0;
  72 }
  73
  74 static int ipv6_mc_check_mld_reportv2(struct sk_buff *skb)
  75 {
  76         unsigned int len = skb_transport_offset(skb);
  77
  78         len += sizeof(struct mld2_report);
  79
  80         return pskb_may_pull(skb, len) ? 0 : -EINVAL;
  81 }
  82
  83 static int ipv6_mc_check_mld_query(struct sk_buff *skb)
  84 {
  85         struct mld_msg *mld;
  86         unsigned int len = skb_transport_offset(skb);
  87
  88         /* RFC2710+RFC3810 (MLDv1+MLDv2) require link-local source addresses */
  89         if (!(ipv6_addr_type(&ipv6_hdr(skb)->saddr) & IPV6_ADDR_LINKLOCAL))
  90                 return -EINVAL;
  91
  92         len += sizeof(struct mld_msg);
  93         if (skb->len < len)
  94                 return -EINVAL;
  95
  96         /* MLDv1? */
  97         if (skb->len != len) {
  98                 /* or MLDv2? */
  99                 len += sizeof(struct mld2_query) - sizeof(struct mld_msg);
 100                 if (skb->len < len || !pskb_may_pull(skb, len))
 101                         return -EINVAL;
 102         }
 103
 104         mld = (struct mld_msg *)skb_transport_header(skb);
 105
 106         /* RFC2710+RFC3810 (MLDv1+MLDv2) require the multicast link layer
 107          * all-nodes destination address (ff02::1) for general queries
 108          */
 109         if (ipv6_addr_any(&mld->mld_mca) &&
 110             !ipv6_addr_is_ll_all_nodes(&ipv6_hdr(skb)->daddr))
 111                 return -EINVAL;
 112
 113         return 0;
 114 }
 115
 116 static int ipv6_mc_check_mld_msg(struct sk_buff *skb)
 117 {
 118         struct mld_msg *mld = (struct mld_msg *)skb_transport_header(skb);
 119
 120         switch (mld->mld_type) {
 121         case ICMPV6_MGM_REDUCTION:
 122         case ICMPV6_MGM_REPORT:
 123                 /* fall through */
 124                 return 0;
 125         case ICMPV6_MLD2_REPORT:
 126                 return ipv6_mc_check_mld_reportv2(skb);
 127         case ICMPV6_MGM_QUERY:
 128                 return ipv6_mc_check_mld_query(skb);
 129         default:
 130                 return -ENOMSG;
 131         }
 132 }
 133
 134 static inline __sum16 ipv6_mc_validate_checksum(struct sk_buff *skb)
 135 {
 136         return skb_checksum_validate(skb, IPPROTO_ICMPV6, ip6_compute_pseudo);
 137 }
 138
 139 static int __ipv6_mc_check_mld(struct sk_buff *skb,
 140                                struct sk_buff **skb_trimmed)
 141
 142 {
 143         struct sk_buff *skb_chk = NULL;
 144         unsigned int transport_len;
 145         unsigned int len = skb_transport_offset(skb) + sizeof(struct mld_msg);
 146         int ret = -EINVAL;
 147
 148         transport_len = ntohs(ipv6_hdr(skb)->payload_len);
 149         transport_len -= skb_transport_offset(skb) - sizeof(struct ipv6hdr);
 150
 151         skb_chk = skb_checksum_trimmed(skb, transport_len,
 152                                        ipv6_mc_validate_checksum);
 153         if (!skb_chk)
 154                 goto err;
 155
 156         if (!pskb_may_pull(skb_chk, len))
 157                 goto err;
 158
 159         ret = ipv6_mc_check_mld_msg(skb_chk);
 160         if (ret)
 161                 goto err;
 162
 163         if (skb_trimmed)
 164                 *skb_trimmed = skb_chk;
 165         /* free now unneeded clone */
 166         else if (skb_chk != skb)
 167                 kfree_skb(skb_chk);
 168
 169         ret = 0;
 170
 171 err:
 172         if (ret && skb_chk && skb_chk != skb)
 173                 kfree_skb(skb_chk);
 174
 175         return ret;
 176 }
 177
 178 /**
 179  * ipv6_mc_check_mld - checks whether this is a sane MLD packet
 180  * @skb: the skb to validate
 181  * @skb_trimmed: to store an skb pointer trimmed to IPv6 packet tail (optional)
 182  *
 183  * Checks whether an IPv6 packet is a valid MLD packet. If so sets
 184  * skb transport header accordingly and returns zero.
 185  *
 186  * -EINVAL: A broken packet was detected, i.e. it violates some internet
 187  *  standard
 188  * -ENOMSG: IP header validation succeeded but it is not an MLD packet.
 189  * -ENOMEM: A memory allocation failure happened.
 190  *
 191  * Optionally, an skb pointer might be provided via skb_trimmed (or set it
 192  * to NULL): After parsing an MLD packet successfully it will point to
 193  * an skb which has its tail aligned to the IP packet end. This might
 194  * either be the originally provided skb or a trimmed, cloned version if
 195  * the skb frame had data beyond the IP packet. A cloned skb allows us
 196  * to leave the original skb and its full frame unchanged (which might be
 197  * desirable for layer 2 frame jugglers).
 198  *
 199  * Caller needs to set the skb network header and free any returned skb if it
 200  * differs from the provided skb.
 201  */
 202 int ipv6_mc_check_mld(struct sk_buff *skb, struct sk_buff **skb_trimmed)
 203 {
 204         int ret;
 205
 206         ret = ipv6_mc_check_ip6hdr(skb);
 207         if (ret < 0)
 208                 return ret;
 209
 210         ret = ipv6_mc_check_exthdrs(skb);
 211         if (ret < 0)
 212                 return ret;
 213
 214         return __ipv6_mc_check_mld(skb, skb_trimmed);
 215 }
 216 EXPORT_SYMBOL(ipv6_mc_check_mld);