linux-kernel - Re: [PATCH] af_packet: Handle outgoing VLAN packets without hardware offloading

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Date: Sat, 25 May 2024 11:51:34 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Chengen Du <chengen.du@...onical.com>, 
 Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc: davem@...emloft.net, 
 edumazet@...gle.com, 
 kuba@...nel.org, 
 pabeni@...hat.com, 
 netdev@...r.kernel.org, 
 linux-kernel@...r.kernel.org, 
 alexandre.ferrieux@...nge.com
Subject: Re: [PATCH] af_packet: Handle outgoing VLAN packets without hardware
 offloading

> Firstly, I will submit a patch to add a new bit in the status to
> indicate the presence of VLAN information in the payload and modify
> the header's entry accordingly.
> A new member will be added to the sockaddr_ll struct to represent the
> VLAN-encapsulated protocol, thus avoiding direct modification of the
> sll_protocol.

See my earlier comments to your v1 patch. It's a minor respin. Please
don't add new members.

> Following this patch, I will work on enabling the link layer header
> via a socket option.

Let's focus on the VLAN for now.

Any expansion of the ABI requires a very clear path to use. I'd like
to see the pcap and tcpdump (or wireshark) changes that use it.

First, we need to even understand better why anything is using
SOCK_DGRAM when access to L2.5 headers is important, and whether the
process can convert to using SOCK_RAW instead.