From mboxrd@z Thu Jan 1 00:00:00 1970 From: Georg Kohmann Subject: [PATCH] ipv6: icmp: Updating pmtu for link local route Date: Thu, 2 Aug 2018 13:56:58 +0200 Message-ID: <20180802115658.17084-1-geokohma@cisco.com> Cc: Georg Kohmann To: netdev@vger.kernel.org Return-path: Received: from aer-iport-3.cisco.com ([173.38.203.53]:24133 "EHLO aer-iport-3.cisco.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732237AbeHBNrw (ORCPT ); Thu, 2 Aug 2018 09:47:52 -0400 Sender: netdev-owner@vger.kernel.org List-ID: When a ICMPV6_PKT_TOOBIG is received from a link local address the pmtu will be updated on a route with an arbitrary interface index. Subsequent packets sent back to the same link local address may therefore end up not considering the updated pmtu. Current behavior breaks TAHI v6LC4.1.4 Reduce PMTU On-link. Referring to RFC 1981: Section 3: "Note that Path MTU Discovery must be performed even in cases where a node "thinks" a destination is attached to the same link as itself. In a situation such as when a neighboring router acts as proxy [ND] for some destination, the destination can to appear to be directly connected but is in fact more than one hop away." Using the interface index from the incoming ICMPV6_PKT_TOOBIG when updating the pmtu. Signed-off-by: Georg Kohmann --- net/ipv6/icmp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c index 3ae2fbe..211db37 100644 --- a/net/ipv6/icmp.c +++ b/net/ipv6/icmp.c @@ -92,7 +92,7 @@ static void icmpv6_err(struct sk_buff *skb, struct inet6_skb_parm *opt, struct net *net = dev_net(skb->dev); if (type == ICMPV6_PKT_TOOBIG) - ip6_update_pmtu(skb, net, info, 0, 0, sock_net_uid(net, NULL)); + ip6_update_pmtu(skb, net, info, skb->dev->ifindex, 0, sock_net_uid(net, NULL)); else if (type == NDISC_REDIRECT) ip6_redirect(skb, net, skb->dev->ifindex, 0, sock_net_uid(net, NULL)); -- 2.10.2