netdev - Re: [PATCH v10 nf-next 2/3] netfilter: nft_chain_filter: Add bridge double vlan and pppoe

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Message-ID: <Z9n8GHYfuhTFZB3p@calendula>
Date: Wed, 19 Mar 2025 00:04:56 +0100
From: Pablo Neira Ayuso <pablo@...filter.org>
To: Eric Woudstra <ericwouds@...il.com>
Cc: Jozsef Kadlecsik <kadlec@...filter.org>,
	Roopa Prabhu <roopa@...dia.com>,
	Nikolay Aleksandrov <razor@...ckwall.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>, Shuah Khan <shuah@...nel.org>,
	netfilter-devel@...r.kernel.org, bridge@...ts.linux.dev,
	netdev@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v10 nf-next 2/3] netfilter: nft_chain_filter: Add bridge
 double vlan and pppoe

Hi,

On Sat, Mar 15, 2025 at 09:00:32PM +0100, Eric Woudstra wrote:
> This adds the capability to evaluate 802.1ad, QinQ, PPPoE and PPPoE-in-Q
> packets in the bridge filter chain.
> 
> Reviewed-by: Nikolay Aleksandrov <razor@...ckwall.org>
> Signed-off-by: Eric Woudstra <ericwouds@...il.com>
> ---
>  net/netfilter/nft_chain_filter.c | 20 +++++++++++++++++++-
>  1 file changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/net/netfilter/nft_chain_filter.c b/net/netfilter/nft_chain_filter.c
> index 19a553550c76..7c7080c1a67d 100644
> --- a/net/netfilter/nft_chain_filter.c
> +++ b/net/netfilter/nft_chain_filter.c
> @@ -232,11 +232,27 @@ nft_do_chain_bridge(void *priv,
>  		    struct sk_buff *skb,
>  		    const struct nf_hook_state *state)
>  {
> +	struct ethhdr *ethh = eth_hdr(skb);
>  	struct nft_pktinfo pkt;
> +	int thoff;
>  
>  	nft_set_pktinfo(&pkt, skb, state);
>  
> -	switch (eth_hdr(skb)->h_proto) {
> +	switch (ethh->h_proto) {
> +	case htons(ETH_P_PPP_SES):
> +		thoff = PPPOE_SES_HLEN;
> +		ethh += thoff;

This pointer arithmetics does not look correct, ethh is struct ethhdr,
neither void nor char.

> +		break;
> +	case htons(ETH_P_8021Q):
> +		thoff = VLAN_HLEN;
> +		ethh += thoff;

Same here.

> +		break;
> +	default:
> +		thoff = 0;
> +		break;
> +	}
> +
> +	switch (ethh->h_proto) {

This switch will match on the wrong offset.

>  	case htons(ETH_P_IP):
>  		nft_set_pktinfo_ipv4_validate(&pkt);
>  		break;
> @@ -248,6 +264,8 @@ nft_do_chain_bridge(void *priv,
>  		break;
>  	}
>  
> +	pkt.thoff += thoff;

And only transport offset is adjusted here.

>  	return nft_do_chain(&pkt, priv);
>  }
>  
> -- 
> 2.47.1
>