netdev - Re: [RFC PATCH v1.0] af_packet: don't emit packet on orig fanout group

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Date:	Thu, 16 Aug 2012 14:52:00 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	eric@...it.org
Cc:	netdev@...r.kernel.org
Subject: Re: [RFC PATCH v1.0] af_packet: don't emit packet on orig fanout
 group

From: Eric Leblond <eric@...it.org>
Date: Thu, 16 Aug 2012 17:44:50 +0200

> If a packet is emitted on one socket in one group of fanout sockets,
> it is transmitted again. It is thus read again on one of the sockets
> of the fanout group. This result in a loop for software which
> generate packets when receiving one.
> This retransmission is not the intended behavior: a fanout group
> must behave like a single socket. The packet should not be
> transmitted on a socket if it originates from a socket belonging
> to the same fanout group.
> 
> This patch fixes the issue by changing the transmission check to
> take fanout group info account.

This looks mostly fine, thanks for fixing this.

I wonder if it wouldn't be better to simply have a callback?  That
would eliminate all of the ifdefs:

	if (ptype->id_match) {
		if (ptype->id_match(ptype, skb->sk))
			return true;
	} else if (ptype->af_packet_priv == skb->sk)
		return true;

It's a shame that we have a user of af_packet_priv outside of
AF_PACKET, in TIPC.  If we could get rid of that we could simplify
things even futher.
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