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From: John Baldwin <jhb@freebsd.org>
To: freebsd-net@freebsd.org
Subject: Re: A small fix for if_em.c, if_igb.c, if_ixgbe.c
Date: Fri, 13 Dec 2013 13:26:28 -0500
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 (bigwig.baldwin.cx); Fri, 13 Dec 2013 15:57:45 -0500 (EST)
Cc: Yong-Hyeon Pyun <pyunyh@gmail.com>,
 Michael Tuexen <Michael.Tuexen@lurchi.franken.de>,
 Adrian Chadd <adrian@freebsd.org>, Jack F Vogel <jfv@freebsd.org>,
 John-Mark Gurney <jmg@funkthat.com>
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On Monday, December 09, 2013 2:37:08 pm Adrian Chadd wrote:
> Jack / John - thoughts?

Note that if_start has always worked the way if_transmit would work with the 
err = 0 change.  All the other drivers in the tree are already giving you an 
error if an earlier packet in the IFQ fails to transmit, and it's been that 
way for decades.  If you decide to make if_transmit precise (only return an 
error if the specific packet fails), the corresponding change for if_start() 
drivers would be to never return an error ever.

It's not clear to me what the impact of that would be.  However, the current 
patch to return 0 in the drbr_putback case would at least restore things to 
the previous status quo from the past few decades for both if_start() and 
if_transmit() drivers.

-- 
John Baldwin