netdev - Re: Linux kernel patch: elide fib_validate_source() completely when possible

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Message-Id: <20140122.185305.1125981867482223830.davem@davemloft.net>
Date:	Wed, 22 Jan 2014 18:53:05 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	hannes@...essinduktion.org
Cc:	ja@....bg, gregory.hoggarth@...iedtelesis.co.nz,
	netdev@...r.kernel.org
Subject: Re: Linux kernel patch: elide fib_validate_source() completely
 when possible - bad side effect?

From: Hannes Frederic Sowa <hannes@...essinduktion.org>
Date: Thu, 23 Jan 2014 03:02:24 +0100

> On Wed, Jan 22, 2014 at 11:04:52PM +0200, Julian Anastasov wrote:
>> 	I don't remember someone mentioning about such
>> side-effect, I guess it is overlooked. IMHO, it is not a good
>> reason to restore the old behavior. Lets see other opinions.
> 
> A routing lookup to check for broadcast is much too expansive, I agree. But
> can't we just check skb->pkt_type == PACKET_BROADCAST?

We can't universally know what a broadcast is, because the prefix of
every network is a local piece of information.

We might not have the route necessary to know the source address is
a broadcast if the packet came through more than 1 hop already.
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