netdev - Re: Unexpected source address selection in routing

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Message-ID: <alpine.LNX.1.10.0808242126540.22921@fbirervta.pbzchgretzou.qr>
Date:	Sun, 24 Aug 2008 21:28:10 -0400 (EDT)
From:	Jan Engelhardt <jengelh@...ozas.de>
To:	David Miller <davem@...emloft.net>
cc:	netdev@...r.kernel.org, netfilter-devel@...r.kernel.org
Subject: Re: Unexpected source address selection in routing


On Sunday 2008-08-24 20:31, David Miller wrote:
>
>> It appears that the routing code selects the outgoing source address to 
>> use for packets is chosen when the socket is established instead of
>> at routing time.
>> 
>> The following presents a test case for "unexpected" (from a user's 
>> perspective) behavior.
>> 
>> Is there any way to make it behave as a user would expect?
>
>No matter when we had made the routing lookup, we would have ended
>up with what you see the kernel doing.
>
>The route is looked up long before netfilter even sees the packets.
>
>The source address selection at the socket level can only "see" the
>original destination address and therefore makes the source address
>selection using that original destination address.

That's what I thought. With IPv4, one can cheat and use
SNAT/MASQUERADE, but what about IPv6? (Other than using the RAWNAT
extension, which bypasses netfilter connection tracking.)
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