Hi Pierre,
On Jan 5 09:03, Pierre A. Humblet wrote:
> While porting exim to Windows 64 I have observed strange results when
> resolving localhost
>
> On Windows XP,
>
> Resolv: search "localhost" type 28
> Resolv: query "localhost" type 28
> Resolv: DnsQuery: 0 (Windows)
> Resolv: localhost Section 0 Type 28 Windows Record Length 16
> 08:02:06 3760 DNS lookup of localhost (AAAA) succeeded
> Resolv: search "localhost" type 1
> Resolv: query "localhost" type 1
> Resolv: DnsQuery: 0 (Windows)
> Resolv: localhost Section 1 Type 1 Windows Record Length 4
> 08:44:13 5552 DNS lookup of localhost (A) succeeded
>
> We see that for IPV4 localhost things are fine.
> Windows returns an answer section (1) and Cygwin processes it correctly.
>
> However for IPV6 it returned a question section (0) but with data in it.
> Cygwin essentially drops that.
> That's why above the application tried an A record after getting the AAAA
> record, which was empty.
>
>
> However of Windows 7
> CYGWIN_NT-6.1 Dell3020 1.7.33-2(0.280/5/3) 2014-11-13 15:47 x86_64 Cygwin
>
> Resolv: search "localhost" type 28
> Resolv: query "localhost" type 28
> Resolv: DnsQuery: 0 (Windows)
> Resolv: localhost Section 0 Type 28 Windows Record Length 16
> 08:22:24 140244 DNS lookup of localhost (AAAA) succeeded
> Resolv: search "localhost" type 1
> Resolv: query "localhost" type 1
> Resolv: DnsQuery: 0 (Windows)
> Resolv: localhost Section 0 Type 1 Windows Record Length 4
>
> We see that Windows returns question sections in both cases and localhost is
> never resolved.
> From what I have seen Windows never returns question section in normal cases
> so I suggest
> inserting the following on line 251 of minires-os-if.c, to essentially turn
> question sections
> in answer sections (after while (rr) { )
>
> if ((rr->Flags.DW & 0x3) == 0) {
> DPRINTF(debug, "Got section 0 %s %d with data length %d\n", DomName,
> Type, rr->wDataLength);
> if (rr->wDataLength > 0)
> rr->Flags.DW |= 1; // Make it an answer section as there is
> data
> }Can you please send at least a real patch? Without the formatting matching the surrounding code I'm totally unsure where to apply this code. A ChangeLog entry would be helpful as well. > It would be nice if this would be tried ASAP. > However I am not setup currently to build cygwin. It's not exactly tricky to set this up... > Occasionally I also see localhost queries fail. > I have not been able to pinpoint what causes that. > > Resolv: search "localhost" type 28 > Resolv: query "localhost" type 28 > Resolv: DnsQuery: 9003 (Windows) > 08:00:14 145640 DNS lookup of localhost (AAAA) gave HOST_NOT_FOUND > 08:00:14 145640 returning DNS_NOMATCH > Resolv: search "localhost" type 1 > Resolv: query "localhost" type 1 > Resolv: DnsQuery: 9003 (Windows) > > > In light of RFC 6761 we should handle localhost in gethostbyname2, for both > IP4 and IP6 > While we are at it we should also handle numerical domains w.x.y.z there. > That's less urgent, I can do that in the coming weeks. Cool, I'm looking forward to your patches! Thanks, Corinna -- Corinna Vinschen Please, send mails regarding Cygwin to Cygwin Maintainer cygwin AT cygwin DOT com Red Hat
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