Subject: Question on the use of ETH_P_CONTROL

From: Alexander Duyck <[email-masked]>
Date: Wed, 24 Apr 2013 11:17:50 -0700

I have a wired Ethernet driver that will need to support a user space
application with UIO access and a network device.  The network device
will need a way to send raw frames with some descriptor data to and from
the user space application.  The frames are not meant to be routed and
are not meant for this host, only for the user space application.  After
doing some digging I came across the definition for ETH_P_CONTROL, which
seems to be a good solution for my current issue.

My thought is to do something like this for Rx control frames:
	eth_type_trans(skb);
	skb->protocol = htons(ETH_P_CONTROL);
	skb->mac_header -= sizeof(struct desc_hdr);
	desc_hdr = (struct desc_hdr *)skb_mac_header(skb);
	desc_hdr->val = val;

For frames received from the user space application I would essentially
just leave the descriptor header on and notify the hardware that it is
present for any frames received that have ETH_P_CONTROL as their protocol.

Then all that is left is for the user space to allocate a raw packet
socket and bind it to our interface specifying the control protocol so
that it can send and receive just the control frames.

I'm looking for any thoughts, issues, or concerns with this approach.

Thanks,

Alex