netdev - Re: [PATCH net] Don't allow overwrite of config src addr

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Message-Id: <20170221.122312.68917979585063893.davem@davemloft.net>
Date:   Tue, 21 Feb 2017 12:23:12 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     brussell@...cade.com
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH net] Don't allow overwrite of config src addr

From: Brian Russell <brussell@...cade.com>
Date: Mon, 20 Feb 2017 17:03:54 +0000

> When using IPv6 transport and a default dst, a pointer to the configured
> source address is passed into the route lookup. If no source address is
> configured, then the value is overwritten.
> 
> IPv6 route lookup ignores egress ifindex match if the source adress is set,
> so if egress ifindex match is desired, the source address must be passed
> as any. The overwrite breaks this for subsequent lookups.
> 
> Avoid this by copying the configured address to an existing stack variable
> and pass a pointer to that instead.
> 
> Signed-off-by: Brian Russell <brussell@...cade.com>

I really would like you to try and find a way to avoid this address copy.
It means even with a cached route, we are going to copy a 128-bit address
onto the stack _every single_ packet vxlan transmits.