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Date: Tue, 4 Nov 2025 16:53:48 +0100
From: Florian Westphal <fw@strlen.de>
To: Eric Woudstra <ericwouds@gmail.com>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>,
	Jozsef Kadlecsik <kadlec@netfilter.org>, Phil Sutter <phil@nwl.cc>,
	Nikolay Aleksandrov <razor@blackwall.org>,
	Ido Schimmel <idosch@nvidia.com>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Simon Horman <horms@kernel.org>, netfilter-devel@vger.kernel.org,
	bridge@lists.linux.dev, netdev@vger.kernel.org
Subject: Re: [PATCH v16 nf-next 3/3] netfilter: nft_chain_filter: Add bridge
 double vlan and pppoe
Message-ID: <aQohjDYORamn7Gya@strlen.de>
References: <20251104145728.517197-1-ericwouds@gmail.com>
 <20251104145728.517197-4-ericwouds@gmail.com>
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In-Reply-To: <20251104145728.517197-4-ericwouds@gmail.com>

Eric Woudstra <ericwouds@gmail.com> wrote:
> +	switch (*proto) {
> +	case htons(ETH_P_PPP_SES): {
> +		struct ppp_hdr {
> +			struct pppoe_hdr hdr;
> +			__be16 proto;
> +		} *ph;
> +
> +		if (!pskb_may_pull(skb, PPPOE_SES_HLEN))
> +			return -1;
> +		ph = (struct ppp_hdr *)(skb->data);
> +		switch (ph->proto) {
> +		case htons(PPP_IP):
> +			*proto = htons(ETH_P_IP);
> +			skb_set_network_header(skb, PPPOE_SES_HLEN);
> +			return PPPOE_SES_HLEN;
> +		case htons(PPP_IPV6):
> +			*proto = htons(ETH_P_IPV6);
> +			skb_set_network_header(skb, PPPOE_SES_HLEN);
> +			return PPPOE_SES_HLEN;
> +		}
> +		break;
> +	}
> +	case htons(ETH_P_8021Q): {
> +		struct vlan_hdr *vhdr;
> +
> +		if (!pskb_may_pull(skb, VLAN_HLEN))
> +			return -1;
> +		vhdr = (struct vlan_hdr *)(skb->data);
> +		*proto = vhdr->h_vlan_encapsulated_proto;
> +		skb_set_network_header(skb, VLAN_HLEN);
> +		return VLAN_HLEN;
> +	}
> +	}
> +	return 0;
> +}
> +
>  static unsigned int
>  nft_do_chain_bridge(void *priv,
>  		    struct sk_buff *skb,
>  		    const struct nf_hook_state *state)
>  {
>  	struct nft_pktinfo pkt;
> +	__be16 proto;
> +	int offset;
>  
> -	nft_set_pktinfo(&pkt, skb, state);
> +	proto = eth_hdr(skb)->h_proto;
>  
> -	switch (eth_hdr(skb)->h_proto) {
> +	offset = nft_set_bridge_pktinfo(&pkt, skb, state, &proto);
> +	if (offset < 0)
> +		return NF_ACCEPT;


Hmm.  I'm not sure, I think this should either drop them right away
OR pass them to do_chain without any changes (i.e. retain existing
behavior and have this be same as nft_set_pktinfo_unspec()).

but please wait until resend.

I hope to finish a larger set i've been working on by tomorrow.
Then I can give this a more thorough review (and also make a summary +
suggestion wrt. the bridge match semantics wrt.  vlan + pppoe etc.

My hunch is that your approach is pretty much the way to go
but I need to complete related homework to make sure I did not
miss/forget anything.