netdev - Re: [PATCH v15 nf-next 3/3] netfilter: nft_chain_filter: Add bridge double vlan and pppoe

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Message-ID: <aN425i3sBuYiC5D5@strlen.de>
Date: Thu, 2 Oct 2025 10:25:10 +0200
From: Florian Westphal <fw@...len.de>
To: Eric Woudstra <ericwouds@...il.com>
Cc: Pablo Neira Ayuso <pablo@...filter.org>,
	Jozsef Kadlecsik <kadlec@...filter.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>,
	Nikolay Aleksandrov <razor@...ckwall.org>,
	Ido Schimmel <idosch@...dia.com>, netfilter-devel@...r.kernel.org,
	netdev@...r.kernel.org, bridge@...ts.linux.dev
Subject: Re: [PATCH v15 nf-next 3/3] netfilter: nft_chain_filter: Add bridge
 double vlan and pppoe

Eric Woudstra <ericwouds@...il.com> wrote:
> This adds the capability to evaluate 802.1ad, QinQ, PPPoE and PPPoE-in-Q
> packets in the bridge filter chain.

Same comment as previous patch, this needs to explain the why, not the what.

nft_do_chain_bridge() passes all packets to the interpreter, so the
above statement is not correct either, you can already filter on all of
these packet types.  This exposes NFT_PKTINFO_L4PROTO etc, which is
different than what this commit message says.

I also vaguely remember I commented that this changes (breaks?) existing
behaviour for a rule like "tcp dport 22 accept" which may now match e.g.
a PPPoE packet.

Pablo, whats your take on this?  Do we need a new NFPROTO_BRIDGE
expression that can munge (populate) nft_pktinfo with the l4 data?

That would move this off to user policy (config) land.

(or extend nft_meta_bridge, doesn't absolutely require a brand new expression).

> +static inline int nft_set_bridge_pktinfo(struct nft_pktinfo *pkt,
> +					 struct sk_buff *skb,
> +					 const struct nf_hook_state *state,
> +					 __be16 *proto)

This is only called from one .c file and unless this gets changed later
this should reside in that .c file (without inline keyword).