Re: Ident authentication fails due to bind error on server (8.4.8) - Mailing list pgsql-bugs

From Tom Lane
Subject Re: Ident authentication fails due to bind error on server (8.4.8)
Date
Msg-id 20339.1308333119@sss.pgh.pa.us
Whole thread Raw
In response to Re: Ident authentication fails due to bind error on server (8.4.8)  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: Ident authentication fails due to bind error on server (8.4.8)
List pgsql-bugs
I wrote:
> I don't think it's a race condition per se.  The code ought to be
> setting up the address argument for bind() with sin_port = 0 so that
> an unused port number gets assigned.  That seems to be what happens on
> a couple of machines that I tried here, but I notice that the Linux
> manpage for getaddrinfo says

>     service sets the port in each returned address structure.  If
>     this argument is a service name (see services(5)), it is
>     translated to the corresponding port number.  This argument can
>     also be specified as a decimal number, which is simply converted
>     to binary.  If service is NULL, then the port number of the
>     returned socket addresses will be left uninitialized.

> In principle this wording would allow getaddrinfo to return the same
> nonzero port number in multiple backends, which would lead to the
> reported failure if they were doing ident verification at the same time.
> I'm thinking maybe we should explicitly pass "0" rather than NULL to
> getaddrinfo here.  On the other hand, it seems to work reliably as-is
> on my Linux machine, so this is just speculation at this point.

I looked at the glibc source code for getaddrinfo, and it looks like
they do reliably set sin_port to zero when no service argument is
provided, despite the above documentation statement.  So that's why it
works for me.  But still, if you're on a non-Linux platform it seems
possible that this is the mechanism for what's biting you.

            regards, tom lane

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