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Date: Tue, 6 Feb 2018 15:20:12 +0100
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: RPC clnt_create() adress already in use
Message-ID: <20180206142012.GB30794@calimero.vinschen.de>
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References: <59D90AF8D70E9740907BACDE2BCB520836E4AA63 AT RESW102 DOT resdom01 DOT local>
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On Feb  6 11:29, PAULUS, Raimund, TI-ABN wrote:
> On Feb  5 15:06, Corinna Vinschen wrote:
> > On Feb  5 14:34, Corinna Vinschen wrote:
> > > On Feb  5 12:26, Corinna Vinschen wrote:
> > > > [...]
> > > > What potential solutions to this problem do we have?
> > > >=20
> > > > - bindresvport could enforce SO_EXCLUSIVEADDRUSE temporarily to make
> > > >   sure bind fails.
> > >=20
> > > Nope, no way.  Even enforcing SO_EXCLUSIVEADDRUSE results in the=20
> > > second bind succeeding and the subsequent connect failing.  The=20
> > > entire SO_REUSEADDR/SO_EXCLUSIVEADDRUSE semantics only works as=20
> > > desired on the server side apparently
> > >=20
> > > > - bindresvport could check every local address for being free prior
> > > >   to calling bind.  However, there's a potential race here.
> > > >=20
> > > > - DisconnectEx?  Never tried this Winsock extension but it might be
> > > >   worth a shot.
> >=20
> > I think I have a very simple solution for the scenario which calls=20
> > bindresvport with port number.  Still looking for a solution for the=20
> > second problem...
>=20
> I've pushed a few patches and uploaded new developer snapshots to
> https://cygwin.com/snapshots.  Please give them a try.
>=20
> with the snapshot of cygwin1.dll and using bindresvport() from Cygwin
> for libtirpc (instead of the original bindresvport() from libtirpc)
> all my testcases work without error.
>=20
> Many thanks
> Raimund

Thanks for testing.  Please note that this should work most of the time,
but is still not 100% foolproof.  There's a systematic race between
checking existing connections and calling bind which can't be easily
worked around by Cygwin.  Still, should be better than before :}


Corinna

--=20
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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