netdev - RE: [PATCH] sctp: Fix mangled IPv4 addresses on a IPv6 listening socket

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Date:	Wed, 27 May 2015 16:41:18 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Jason Gunthorpe' <jgunthorpe@...idianresearch.com>
CC:	'Daniel Borkmann' <daniel@...earbox.net>,
	Neil Horman <nhorman@...driver.com>,
	"linux-sctp@...r.kernel.org" <linux-sctp@...r.kernel.org>,
	Vlad Yasevich <vyasevich@...il.com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH] sctp: Fix mangled IPv4 addresses on a IPv6 listening
 socket

From: Jason Gunthorpe
> Sent: 27 May 2015 17:32
> On Wed, May 27, 2015 at 04:16:44PM +0000, David Laight wrote:
> > From: Jason Gunthorpe
> > > Sent: 27 May 2015 16:32
> > > On Wed, May 27, 2015 at 10:11:22AM +0000, David Laight wrote:
> > >
> > > > In any case it looks like I can escape by turning off
> > > > SCTP_I_WANT_MAPPED_V4_ADDR for kernels 3.17 through 4.0.
> > >
> > > Just be aware that option is unusable on kernels without 299ee.
> > >
> > > I fixed everything wrong I saw, but that doesn't mean it works
> > > 100%. Honestly, I don't think anyone has ever used it.
> >
> > I'm now confused.
> >
> > I've just done a test using a 4.0.0-rc1 kernel.
> > I'm binding an IPv6 listening socket and then connecting to it
> > from 127.0.0.1.
> > I don't know it I'm being given an IPv4 format address or a
> > v6mapped one (I shorten the latter before tracing it) - but
> > it contains 127.0.0.1 (not 0.0.0.0).
> > (That is without changing any socket options.)
> 
> I don't know what your test does, but I used the same basic idea with
> loopback to find this issue. You should confirm the kernel is
> returning a AF_INET6 socket type, if it is AF_INET then there is a
> path I missed in 299ee and I should fix it..

The code will be sleeping in kernel_accept() and later calls
kernel_getpeername().
The code is used for both TCP and SCTP and this part is common (using
the TCP semantics).

I'll look at the actual raw address format tomorrow.
I suspect it is already AF_INET6 before getting to the code that would
badly translate it.

	David

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