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Date:	Sat, 5 Sep 2009 18:12:29 +0200
From:	Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To:	cygwin AT cygwin DOT com
Subject:	Re: missing ipi_spec_dst in struct in_pktinfo
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On Sep  4 16:10, Schulman DOT Andrew AT epamail DOT epa DOT gov wrote:
> 
> I'm trying to build socat for Cygwin (1.7).  The build fails with
> 
> xio-ip.c:480: error: structure has no member named `ipi_spec_dst'
> 
> The offending code wants to use pktinfo->ipi_spec_dst.s_addr, where
> pktinfo is a struct in_pktinfo *.  The problem is that in Cygwin,
> in_pktinfo doesn't have an ipi_spec_dst member.  The IP man page
> (http://homepages.cwi.nl/~aeb/linux/man2html/man7/ip.7.html) lists
> in_pktinfo as
> 
> struct in_pktinfo {
>     unsigned int   ipi_ifindex;  /* Interface index */
>     struct in_addr ipi_spec_dst; /* Local address */
>     struct in_addr ipi_addr;     /* Header Destination address */
> };
> 
> while in /usr/include/cygwin/in.h, it's just
> 
> struct in_pktinfo
> {
>   struct in_addr ipi_addr;
>   uint32_t       ipi_ifindex;
> };
> 
> Any suggestions for a workaround to this problem?  Why is ipi_spec_dst
> missing, and more to the point, what can/should I substitute in its
> place?

ipi_spec_dst is missing because the Winsock structure in_pktinfo is
defined without this field.  The recvmsg function will return the
Winsock equivalent to this structure, since that's how it gets it from
Windows.  The workaround is easy: Don't use that field.  Disable the code
in socat which uses it.  Even if we would go to great lengths to
add/remove the field when calling WSASendMsg/WSARecvMsg, it would be
entirely meaningless anyway.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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