netdev - Re: [PATCH] af_packet: add interframe drop cmsg (v6)

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Message-ID: <4ACB16B2.3030001@hartkopp.net>
Date:	Tue, 06 Oct 2009 12:06:42 +0200
From:	Oliver Hartkopp <socketcan@...tkopp.net>
To:	Neil Horman <nhorman@...driver.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	David Miller <davem@...emloft.net>
CC:	netdev@...r.kernel.org
Subject: Re: [PATCH] af_packet: add interframe drop cmsg (v6)


> 
> C) When the application goes to dequeue a frame from the packet socket, we look
> at skb->mark for that frame.  If it is non-zero, we add a cmsg chunk to the
> msghdr of level SOL_PACKET and type PACKET_GAPDATA.  Its a 32 bit integer that
> represents the number of frames lost between this packet and the last previous
> frame received.
> 


> +	gap = check_packet_gap(skb);
> +	if (gap)
> +		put_cmsg(msg, SOL_PACKET, PACKET_GAPDATA, sizeof(__u32), &gap);
> +

I wonder, if using SOL_PACKET with a packet specific sockopt PACKET_GAPDATA is
the right approach here, as this functionality should probably be made
available to all DGRAM/RAW sockets ...

E.g. getting the gap information is also interesting for CAN_RAW sockets as i
polled from the SocketCAN ML.

So i could easily implement something like this in net/can/raw.c :

gap = check_packet_gap(skb);
if (gap)
	put_cmsg(msg, SOL_CAN_RAW, CAN_RAW_GAPDATA, sizeof(__u32), &gap);

Is this a good approach or should we better find a general handling within
SOL_SOCKET here?

Regards,
Oliver
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