From 4a65dff81a04f874fa6915c7f069b4dc2c4010e4 Mon Sep 17 00:00:00 2001 From: Georg Kohmann Date: Wed, 7 Oct 2020 14:53:02 +0200 Subject: net: ipv6: Discard next-hop MTU less than minimum link MTU When a ICMPV6_PKT_TOOBIG report a next-hop MTU that is less than the IPv6 minimum link MTU, the estimated path MTU is reduced to the minimum link MTU. This behaviour breaks TAHI IPv6 Core Conformance Test v6LC4.1.6: Packet Too Big Less than IPv6 MTU. Referring to RFC 8201 section 4: "If a node receives a Packet Too Big message reporting a next-hop MTU that is less than the IPv6 minimum link MTU, it must discard it. A node must not reduce its estimate of the Path MTU below the IPv6 minimum link MTU on receipt of a Packet Too Big message." Drop the path MTU update if reported MTU is less than the minimum link MTU. Signed-off-by: Georg Kohmann Signed-off-by: Jakub Kicinski --- net/ipv6/route.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'net') diff --git a/net/ipv6/route.c b/net/ipv6/route.c index fb075d9545b9..27430d6e1a99 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -2745,7 +2745,8 @@ static void __ip6_rt_update_pmtu(struct dst_entry *dst, const struct sock *sk, if (confirm_neigh) dst_confirm_neigh(dst, daddr); - mtu = max_t(u32, mtu, IPV6_MIN_MTU); + if (mtu < IPV6_MIN_MTU) + return; if (mtu >= dst_mtu(dst)) return; -- cgit v1.2.3