Re: [PATCH v19 nf-next 5/5] netfilter: nft_chain_filter: Add bridge double vlan and pppoe

[Eric Woudstra <ericwouds@gmail.com>]

On 2/24/26 7:53 AM, Eric Woudstra wrote:
> In nft_do_chain_bridge() pktinfo is only fully populated for plain packets
> and packets encapsulated in single 802.1q or 802.1ad.
> 
> When implementing the software bridge-fastpath and testing all possible
> encapulations, there can be more encapsulations:
> 
> The packet could (also) be encapsulated in PPPoE, or the packet could be
> encapsulated in an inner 802.1q, combined with an outer 802.1ad or 802.1q
> encapsulation.
> 
> nft_flow_offload_eval() also examines the L4 header, with the L4 protocol
> known from the conntrack-tuplehash. To access the header it uses
> nft_thoff(), but for these packets it returns zero.
> 
> Introduce nft_set_bridge_pktinfo() to help populate pktinfo with the
> offsets.
> 
> Signed-off-by: Eric Woudstra <ericwouds@gmail.com>
> ---
>  net/netfilter/nft_chain_filter.c | 55 +++++++++++++++++++++++++++++---
>  1 file changed, 51 insertions(+), 4 deletions(-)
> 
> diff --git a/net/netfilter/nft_chain_filter.c b/net/netfilter/nft_chain_filter.c
> index d4d5eadaba9c..66ef30c60e56 100644
> --- a/net/netfilter/nft_chain_filter.c
> +++ b/net/netfilter/nft_chain_filter.c
> @@ -227,21 +227,68 @@ static inline void nft_chain_filter_inet_fini(void) {}
>  #endif /* CONFIG_NF_TABLES_IPV6 */
>  
>  #if IS_ENABLED(CONFIG_NF_TABLES_BRIDGE)
> +static int nft_set_bridge_pktinfo(struct nft_pktinfo *pkt, struct sk_buff *skb,
> +				  const struct nf_hook_state *state,
> +				  __be16 *proto)
> +{
> +	nft_set_pktinfo(pkt, skb, state);
> +
> +	switch (*proto) {
> +	case htons(ETH_P_PPP_SES): {
> +		struct ppp_hdr {
> +			struct pppoe_hdr hdr;
> +			__be16 proto;
> +		} *ph, _ph;
> +
> +		ph = skb_header_pointer(skb, 0, sizeof(_ph), &_ph);
> +		if (!ph) {
> +			*proto = 0;
> +			return -1;
> +		}
> +		switch (ph->proto) {
> +		case htons(PPP_IP):
> +			*proto = htons(ETH_P_IP);
> +			return PPPOE_SES_HLEN;
> +		case htons(PPP_IPV6):
> +			*proto = htons(ETH_P_IPV6);
> +			return PPPOE_SES_HLEN;
> +		}
> +		break;
> +	}
> +	case htons(ETH_P_8021Q): {
> +		struct vlan_hdr *vhdr, _vhdr;
> +
> +		vhdr = skb_header_pointer(skb, 0, sizeof(_vhdr), &_vhdr);
> +		if (!vhdr) {
> +			*proto = 0;
> +			return -1;
> +		}
> +		*proto = vhdr->h_vlan_encapsulated_proto;
> +		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;
> +
> +	offset = nft_set_bridge_pktinfo(&pkt, skb, state, &proto);
>  
> -	switch (eth_hdr(skb)->h_proto) {
> +	switch (proto) {
>  	case htons(ETH_P_IP):
> -		nft_set_pktinfo_ipv4_validate(&pkt, 0);
> +		nft_set_pktinfo_ipv4_validate(&pkt, offset);
>  		break;
>  	case htons(ETH_P_IPV6):
> -		nft_set_pktinfo_ipv6_validate(&pkt, 0);
> +		nft_set_pktinfo_ipv6_validate(&pkt, offset);
>  		break;
>  	default:
>  		nft_set_pktinfo_unspec(&pkt);

Just in case, I'm sending a kind and small reminder, before it is too
late in the cycle.

Regards,

Eric