netdev - Re: Bonding ALB sends bogus packets

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Date:	Thu, 30 Jul 2009 13:28:19 -0700
From:	Jay Vosburgh <fubar@...ibm.com>
To:	Stephen Hemminger <shemminger@...tta.com>
cc:	Ben Greear <greearb@...delatech.com>, bonding-devel@...ts.sf.net,
	netdev@...r.kernel.org
Subject: Re: Bonding ALB sends bogus packets

Stephen Hemminger <shemminger@...tta.com> wrote:

>The bonding ALB mode builds packets with type, ETH_P_LOOP.
>
>Well ETH_P_LOOP is defined as 0x0060 which looks completely bogus.
>All Ethernet types less than 1536 are interpreted as 802.2 frames.
>The result is that the resulting packet looks like a bogus 802.2
>frame to the other host (or switch).  I have no idea what the 
>initial design was or what the purpose of this code is, but it
>should either send a real packet or nothing at all.

	I've looked at that code before, too, although I hadn't noticed
that ETH_P_LOOP is under the limit for interpretation as a length
instead of a type.

	I believe the purpose of the code is to update the switch's MAC
address table for the port and insure it's correct, since the alb mode
can move MAC addresses around amongst the set of slaves.

	-J

---
	-Jay Vosburgh, IBM Linux Technology Center, fubar@...ibm.com
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