From: Florian Westphal <fw@strlen.de>
To: Georg Kohmann <geokohma@cisco.com>
Cc: netdev@vger.kernel.org, coreteam@netfilter.org,
netfilter-devel@vger.kernel.org, kuba@kernel.org,
davem@davemloft.net, fw@strlen.de, kadlec@netfilter.org,
pablo@netfilter.org
Subject: Re: [PATCH net] ipv6/netfilter: Drop Packet Too Big with invalid payload
Date: Thu, 24 Jun 2021 11:05:53 +0200 [thread overview]
Message-ID: <20210624090553.GB24271@breakpoint.cc> (raw)
In-Reply-To: <20210624090135.22406-1-geokohma@cisco.com>
Georg Kohmann <geokohma@cisco.com> wrote:
> PMTU is updated even though received ICMPv6 PTB do not match any
> transmitted traffic. This breaks TAHI IPv6 Core Conformance Test
> Revision 5.0.1, v6LC.4.1.12 Validate Packet Too Big[1].
>
> Referring to RFC8201 IPv6 Path MTU Discovery, section 4: "Nodes should
> appropriately validate the payload of ICMPv6 PTB messages to ensure
> these are received in response to transmitted traffic (i.e., a reported
> error condition that corresponds to an IPv6 packet actually sent by the
> application) per [ICMPv6]."
>
> nf_conntrack_inet_error() return -NF_ACCEPT if the inner header of
> ICMPv6 error packet is not related to an existing connection. Drop PTB
> packet when this occur. This will prevent ipv6 from handling the packet
> and update the PMTU.
This is intentional. We try to not auto-drop packets in conntrack.
Packet is marked as invalid, users can add nft/iptables rules to discard
such packets if they want to do so.
next prev parent reply other threads:[~2021-06-24 9:05 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-24 9:01 [PATCH net] ipv6/netfilter: Drop Packet Too Big with invalid payload Georg Kohmann
2021-06-24 9:05 ` Florian Westphal [this message]
2021-06-24 9:27 ` Georg Kohmann (geokohma)
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