On 01/03/2011 12:15 PM, I wrote:

The following patch allows me to build the 8.3 and 8.4 branches using Visual Studio 2008, once the build system is patched. But I don't really know why. HEAD and 9.0 build fine without it. But those branches branches fail with a complaint about IPPROTO_IPV6 being undefined.

The patch seems harmless enough. But I'd like to know why it's happening. Does anyone have a clue?


-#ifdef IPV6_V6ONLY
+#if defined(IPV6_V6ONLY) && defined(IPPROTO_IPV6)
        if (addr->ai_family == AF_INET6)
        {
            if (setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY,


OK, what's going here is that, in the newer SDK, IPV6_V6ONLY is defined unconditionally, but IPPROTO_IPV6 is only defined if _WIN32_WINNT is set to 0x0501 or higher. We defined _WIN32_WINNT as 0x0500 until 9.0, when we changed it specifically to allow use of the right IPV6 settings.

This seems to me like a clear error in the MS headers. I don't think it makes any sense to define the settings constant but not the context constant. The fix I have suggested above doesn't seem unreasonable or terribly unsafe in these circumstances. The code clearly contemplates the setsockopt() call in question not having been run, as shown in this comment:

        /*
         * Note: This might fail on some OS's, like Linux older than
* 2.4.21-pre3, that don't have the IPV6_V6ONLY socket option, and map
         * ipv4 addresses to ipv6.  It will show ::ffff:ipv4 for all ipv4
         * connections.
         */


cheers

andrew

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