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authorLinus Lüssing <linus.luessing@c0d3.blue>2021-04-25 17:27:35 +0200
committerDavid S. Miller <davem@davemloft.net>2021-04-27 14:02:06 -0700
commit99014088156cd78867d19514a0bc771c4b86b93b (patch)
tree3e196ee651ebc5b4bc70b367c916152ab2c52547 /net/bridge
parent6d72e7c767acbbdd44ebc7d89c6690b405b32b57 (diff)
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net: bridge: mcast: fix broken length + header check for MRDv6 Adv.
The IPv6 Multicast Router Advertisements parsing has the following two issues: For one thing, ICMPv6 MRD Advertisements are smaller than ICMPv6 MLD messages (ICMPv6 MRD Adv.: 8 bytes vs. ICMPv6 MLDv1/2: >= 24 bytes, assuming MLDv2 Reports with at least one multicast address entry). When ipv6_mc_check_mld_msg() tries to parse an Multicast Router Advertisement its MLD length check will fail - and it will wrongly return -EINVAL, even if we have a valid MRD Advertisement. With the returned -EINVAL the bridge code will assume a broken packet and will wrongly discard it, potentially leading to multicast packet loss towards multicast routers. The second issue is the MRD header parsing in br_ip6_multicast_mrd_rcv(): It wrongly checks for an ICMPv6 header immediately after the IPv6 header (IPv6 next header type). However according to RFC4286, section 2 all MRD messages contain a Router Alert option (just like MLD). So instead there is an IPv6 Hop-by-Hop option for the Router Alert between the IPv6 and ICMPv6 header, again leading to the bridge wrongly discarding Multicast Router Advertisements. To fix these two issues, introduce a new return value -ENODATA to ipv6_mc_check_mld() to indicate a valid ICMPv6 packet with a hop-by-hop option which is not an MLD but potentially an MRD packet. This also simplifies further parsing in the bridge code, as ipv6_mc_check_mld() already fully checks the ICMPv6 header and hop-by-hop option. These issues were found and fixed with the help of the mrdisc tool (https://github.com/troglobit/mrdisc). Fixes: 4b3087c7e37f ("bridge: Snoop Multicast Router Advertisements") Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/bridge')
-rw-r--r--net/bridge/br_multicast.c33
1 files changed, 8 insertions, 25 deletions
diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index 2883601d5c8b..226bb05c3b42 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -3159,25 +3159,14 @@ static int br_multicast_ipv4_rcv(struct net_bridge *br,
}
#if IS_ENABLED(CONFIG_IPV6)
-static int br_ip6_multicast_mrd_rcv(struct net_bridge *br,
- struct net_bridge_port *port,
- struct sk_buff *skb)
+static void br_ip6_multicast_mrd_rcv(struct net_bridge *br,
+ struct net_bridge_port *port,
+ struct sk_buff *skb)
{
- int ret;
-
- if (ipv6_hdr(skb)->nexthdr != IPPROTO_ICMPV6)
- return -ENOMSG;
-
- ret = ipv6_mc_check_icmpv6(skb);
- if (ret < 0)
- return ret;
-
if (icmp6_hdr(skb)->icmp6_type != ICMPV6_MRDISC_ADV)
- return -ENOMSG;
+ return;
br_multicast_mark_router(br, port);
-
- return 0;
}
static int br_multicast_ipv6_rcv(struct net_bridge *br,
@@ -3191,18 +3180,12 @@ static int br_multicast_ipv6_rcv(struct net_bridge *br,
err = ipv6_mc_check_mld(skb);
- if (err == -ENOMSG) {
+ if (err == -ENOMSG || err == -ENODATA) {
if (!ipv6_addr_is_ll_all_nodes(&ipv6_hdr(skb)->daddr))
BR_INPUT_SKB_CB(skb)->mrouters_only = 1;
-
- if (ipv6_addr_is_all_snoopers(&ipv6_hdr(skb)->daddr)) {
- err = br_ip6_multicast_mrd_rcv(br, port, skb);
-
- if (err < 0 && err != -ENOMSG) {
- br_multicast_err_count(br, port, skb->protocol);
- return err;
- }
- }
+ if (err == -ENODATA &&
+ ipv6_addr_is_all_snoopers(&ipv6_hdr(skb)->daddr))
+ br_ip6_multicast_mrd_rcv(br, port, skb);
return 0;
} else if (err < 0) {