Re: [PATCH v4 net-next 02/13] netfilter: bridge: Add conntrack double vlan and pppoe

[Nikolay Aleksandrov <razor@blackwall.org>]

On 1/7/25 11:05, Eric Woudstra wrote:
> This adds the capability to conntrack 802.1ad, QinQ, PPPoE and PPPoE-in-Q
> packets that are passing a bridge.
> 
> Signed-off-by: Eric Woudstra <ericwouds@gmail.com>
> ---
>  net/bridge/netfilter/nf_conntrack_bridge.c | 88 ++++++++++++++++++----
>  1 file changed, 75 insertions(+), 13 deletions(-)
> 
> diff --git a/net/bridge/netfilter/nf_conntrack_bridge.c b/net/bridge/netfilter/nf_conntrack_bridge.c
> index 816bb0fde718..31e2bcd71735 100644
> --- a/net/bridge/netfilter/nf_conntrack_bridge.c
> +++ b/net/bridge/netfilter/nf_conntrack_bridge.c
> @@ -241,56 +241,118 @@ static unsigned int nf_ct_bridge_pre(void *priv, struct sk_buff *skb,
>  				     const struct nf_hook_state *state)
>  {
>  	struct nf_hook_state bridge_state = *state;
> +	__be16 outer_proto, inner_proto;
>  	enum ip_conntrack_info ctinfo;
> +	int ret, offset = 0;
>  	struct nf_conn *ct;
> -	u32 len;
> -	int ret;
> +	u32 len, data_len;
>  
>  	ct = nf_ct_get(skb, &ctinfo);
>  	if ((ct && !nf_ct_is_template(ct)) ||
>  	    ctinfo == IP_CT_UNTRACKED)
>  		return NF_ACCEPT;
>  

In all cases below I think you should make sure the headers are present
in the linear part of the skb, either do pskb_may_pull() or use
skb_header_pointer(). This is executed in the PRE bridge hook, so nothing
has been pulled yet by it.

> +	switch (skb->protocol) {
> +	case htons(ETH_P_PPP_SES): {
> +		struct ppp_hdr {
> +			struct pppoe_hdr hdr;
> +			__be16 proto;
> +		} *ph = (struct ppp_hdr *)(skb->data);
> +
> +		data_len = ntohs(ph->hdr.length) - 2;
> +		offset = PPPOE_SES_HLEN;
> +		outer_proto = skb->protocol;
> +		switch (ph->proto) {
> +		case htons(PPP_IP):
> +			inner_proto = htons(ETH_P_IP);
> +			break;
> +		case htons(PPP_IPV6):
> +			inner_proto = htons(ETH_P_IPV6);
> +			break;
> +		default:
> +			return NF_ACCEPT;
> +		}
> +		break;
> +	}
> +	case htons(ETH_P_8021Q): {
> +		struct vlan_hdr *vhdr = (struct vlan_hdr *)(skb->data);
> +
> +		data_len = 0xffffffff;
> +		offset = VLAN_HLEN;
> +		outer_proto = skb->protocol;
> +		inner_proto = vhdr->h_vlan_encapsulated_proto;
> +		break;
> +	}
> +	default:
> +		data_len = 0xffffffff;
> +		break;
> +	}
> +
> +	if (offset) {
> +		switch (inner_proto) {
> +		case htons(ETH_P_IP):
> +		case htons(ETH_P_IPV6):
> +			if (!pskb_may_pull(skb, offset))
> +				return NF_ACCEPT;
> +			skb_pull_rcsum(skb, offset);> +			skb_reset_network_header(skb);
> +			skb->protocol = inner_proto;
> +			break;
> +		default:
> +			return NF_ACCEPT;
> +		}
> +	}
> +
> +	ret = NF_ACCEPT;
>  	switch (skb->protocol) {
>  	case htons(ETH_P_IP):
>  		if (!pskb_may_pull(skb, sizeof(struct iphdr)))
> -			return NF_ACCEPT;
> +			goto do_not_track;
>  
>  		len = skb_ip_totlen(skb);
> +		if (data_len < len)
> +			len = data_len;
>  		if (pskb_trim_rcsum(skb, len))
> -			return NF_ACCEPT;
> +			goto do_not_track;
>  
>  		if (nf_ct_br_ip_check(skb))
> -			return NF_ACCEPT;
> +			goto do_not_track;
>  
>  		bridge_state.pf = NFPROTO_IPV4;
>  		ret = nf_ct_br_defrag4(skb, &bridge_state);
>  		break;
>  	case htons(ETH_P_IPV6):
>  		if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
> -			return NF_ACCEPT;
> +			goto do_not_track;
>  
>  		len = sizeof(struct ipv6hdr) + ntohs(ipv6_hdr(skb)->payload_len);
> +		if (data_len < len)
> +			len = data_len;
>  		if (pskb_trim_rcsum(skb, len))
> -			return NF_ACCEPT;
> +			goto do_not_track;
>  
>  		if (nf_ct_br_ipv6_check(skb))
> -			return NF_ACCEPT;
> +			goto do_not_track;
>  
>  		bridge_state.pf = NFPROTO_IPV6;
>  		ret = nf_ct_br_defrag6(skb, &bridge_state);
>  		break;
>  	default:
>  		nf_ct_set(skb, NULL, IP_CT_UNTRACKED);
> -		return NF_ACCEPT;
> +		goto do_not_track;
>  	}
>  
> -	if (ret != NF_ACCEPT)
> -		return ret;
> +	if (ret == NF_ACCEPT)
> +		ret = nf_conntrack_in(skb, &bridge_state);
>  
> -	return nf_conntrack_in(skb, &bridge_state);
> +do_not_track:
> +	if (offset) {
> +		skb_push_rcsum(skb, offset);
> +		skb_reset_network_header(skb);
> +		skb->protocol = outer_proto;
> +	}
> +	return ret;
>  }
> -
>  static unsigned int nf_ct_bridge_in(void *priv, struct sk_buff *skb,
>  				    const struct nf_hook_state *state)
>  {