netdev - Re: [PATCH net-next v2 01/12] flow_dissector: Parse ETH_P

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Message-ID: <66bfa0823734a_184d66294a3@willemb.c.googlers.com.notmuch>
Date: Fri, 16 Aug 2024 14:54:58 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Tom Herbert <tom@...bertland.com>, 
 davem@...emloft.net, 
 kuba@...nel.org, 
 edumazet@...gle.com, 
 netdev@...r.kernel.org, 
 felipe@...anda.io, 
 willemdebruijn.kernel@...il.com
Cc: Tom Herbert <tom@...bertland.com>
Subject: Re: [PATCH net-next v2 01/12] flow_dissector: Parse ETH_P_TEB and
 move out of GRE

Tom Herbert wrote:
> ETH_P_TEB (Trans Ether Bridging) is the EtherType to carry
> a plain Etherent frame. Add case in skb_flow_dissect to parse
> packets of this type
> 
> If the GRE protocol is ETH_P_TEB then just process that as any
> another EtherType since it's now supported in the main loop
> 
> Signed-off-by: Tom Herbert <tom@...bertland.com>

Reviewed-by: Willem de Bruijn <willemb@...gle.com>

> -	if (gre_ver == 0) {
> -		if (*p_proto == htons(ETH_P_TEB)) {
> -			const struct ethhdr *eth;
> -			struct ethhdr _eth;
> -
> -			eth = __skb_header_pointer(skb, *p_nhoff + offset,
> -						   sizeof(_eth),
> -						   data, *p_hlen, &_eth);
> -			if (!eth)
> -				return FLOW_DISSECT_RET_OUT_BAD;
> -			*p_proto = eth->h_proto;
> -			offset += sizeof(*eth);
> -
> -			/* Cap headers that we access via pointers at the
> -			 * end of the Ethernet header as our maximum alignment
> -			 * at that point is only 2 bytes.
> -			 */
> -			if (NET_IP_ALIGN)
> -				*p_hlen = *p_nhoff + offset;
> -		}
> -	} else { /* version 1, must be PPTP */

> @@ -1284,6 +1268,27 @@ bool __skb_flow_dissect(const struct net *net,
>  
>  		break;
>  	}
> +	case htons(ETH_P_TEB): {
> +		const struct ethhdr *eth;
> +		struct ethhdr _eth;
> +
> +		eth = __skb_header_pointer(skb, nhoff, sizeof(_eth),
> +					   data, hlen, &_eth);
> +		if (!eth)
> +			goto out_bad;
> +
> +		proto = eth->h_proto;
> +		nhoff += sizeof(*eth);
> +
> +		/* Cap headers that we access via pointers at the
> +		 * end of the Ethernet header as our maximum alignment
> +		 * at that point is only 2 bytes.
> +		 */
> +		if (NET_IP_ALIGN)
> +			hlen = nhoff;

I wonder why this exists. But besides the point of this move.

> +
> +		goto proto_again;
> +	}