linux-kernel - Re: [PATCH net] netfilter: conntrack: fix ct-state for ICMPv6 Multicast Router Discovery

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Message-ID: <20240307101254.GL281974@kernel.org>
Date: Thu, 7 Mar 2024 10:12:54 +0000
From: Simon Horman <horms@...nel.org>
To: Linus Lüssing <linus.luessing@...3.blue>
Cc: netfilter-devel@...r.kernel.org, coreteam@...filter.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Pablo Neira Ayuso <pablo@...filter.org>,
	Jozsef Kadlecsik <kadlec@...filter.org>,
	Florian Westphal <fw@...len.de>,
	"David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Dietmar Maurer <dietmar@...xmox.com>,
	Thomas Lamprecht <t.lamprecht@...xmox.com>,
	Wolfgang Bumiller <w.bumiller@...xmox.com>,
	Alexandre Derumier <aderumier@...so.com>
Subject: Re: [PATCH net] netfilter: conntrack: fix ct-state for ICMPv6
 Multicast Router Discovery

On Wed, Mar 06, 2024 at 03:18:04PM +0100, Linus Lüssing wrote:
> So far Multicast Router Advertisements and Multicast Router
> Solicitations from the Multicast Router Discovery protocol (RFC4286)
> would be marked as INVALID for IPv6, even if they are in fact intact
> and adhering to RFC4286.
> 
> This broke MRA reception and by that multicast reception on
> IPv6 multicast routers in a Proxmox managed setup, where Proxmox
> would install a rule like "-m conntrack --ctstate INVALID -j DROP"
> at the top of the FORWARD chain with br-nf-call-ip6tables enabled
> by default.
> 
> Similar to as it's done for MLDv1, MLDv2 and IPv6 Neighbor Discovery
> already, fix this issue by excluding MRD from connection tracking
> handling as MRD always uses predefined multicast destinations
> for its messages, too. This changes the ct-state for ICMPv6 MRD messages
> from INVALID to UNTRACKED.
> 
> This issue was found and fixed with the help of the mrdisc tool
> (https://github.com/troglobit/mrdisc).
> 
> Signed-off-by: Linus Lüssing <linus.luessing@...3.blue>

Hi Linus,

this appears to be a fix and as such I think it warrants a Fixes tag.
You should be able to just add it to this thread if no other changes
are required - no need for a v2 just to address this.

..