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\xC3\xBCssing <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, 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, 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
  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(&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
 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                                       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
 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