netdev - Re: ip_queue_xmit() used illegally

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Message-Id: <20110506.132129.59693228.davem@davemloft.net>
Date:	Fri, 06 May 2011 13:21:29 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	netdev@...r.kernel.org
Cc:	vladislav.yasevich@...com, yjwei@...fujitsu.com,
	jchapman@...alix.com
Subject: Re: ip_queue_xmit() used illegally

From: David Miller <davem@...emloft.net>
Date: Fri, 06 May 2011 12:26:56 -0700 (PDT)

> SCTP stores it's binding information using transports and assosciations
> and does not fill in the ->inet_{daddr,saddr} values.
> 
> It tries to work around this route issue by checking dst->obsolete
> directly in sctp_packet_transmit(), which just makes the race smaller
> and does not eliminate it.  ip_queue_xmit() can still end up with
> __sk_dst_check() returning NULL and then we end up emitting a
> potentially bogus packet.

I take this back, we added this hack where things like SCTP can
pre-route the packet by hooking up the route to the SKB before
calling ->queue_xmit.

And L2TP does something similar.

So false alarm, nothing to see here :-)

I still want to clean this up so that this kind of stuff can be
handled generically inside of ->queue_xmit() by passing in the correct
addressing information.
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