[Bug libc/10128] New: __libc_res_nquery fails if one answer returns NOERROR and the other NOTIMP or FORMERR

[Bug libc/10128] New: __libc_res_nquery fails if one answer returns NOERROR and the other NOTIMP or FORMERR

[aurelien at aurel32 dot net]

Now that the glibc send both IPv4 and IPv6 requests in parallel, name 
resolution does not work anymore on DNS servers returning *two answers*, but 
NOTIMP or FORMERR to the AAAA query and NOERROR on the A query. This is broken 
according to the RFC, but it seems a common mistake among broken DNS software.

The recent changes to switch back to single request mode in case of timeout 
does not work here (as both queries are answered), so I propose the following 
patch below to solve the issue:


2009-05-05  Aurelien Jarno  <aurelien@aurel32.net>

        * resolv/res_query.c (__libc_res_nquery): If one query returns NOTIMP
        or FORMERR and the other NOERROR, don't raise an error.

--- a/resolv/res_query.c
+++ b/resolv/res_query.c
@@ -289,6 +289,10 @@ __libc_res_nquery(res_state statp,
                        break;
                case FORMERR:
                case NOTIMP:
+                       if ((hp->rcode == NOERROR && ntohs (hp->ancount) != 0)
+                           || (hp2->rcode == NOERROR
+                               && ntohs (hp2->ancount) != 0))
+                               goto success;
                case REFUSED:
                default:
                        RES_SET_H_ERRNO(statp, NO_RECOVERY);

-- 
           Summary: __libc_res_nquery fails if one answer returns NOERROR
                    and the other NOTIMP or FORMERR
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
        AssignedTo: drepper at redhat dot com
        ReportedBy: aurelien at aurel32 dot net
                CC: glibc-bugs at sources dot redhat dot com
 GCC build triplet: x86_64-unknown-linux-gnu
  GCC host triplet: x86_64-unknown-linux-gnu
GCC target triplet: x86_64-unknown-linux-gnu


http://sourceware.org/bugzilla/show_bug.cgi?id=10128

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[Bug libc/10128] __libc_res_nquery fails if one answer returns NOERROR and the other NOTIMP or FORMERR

[drepper at redhat dot com]

------- Additional Comments From drepper at redhat dot com  2009-05-05 14:48 -------
Where is such a server?  And why can you claim "common"?

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |WAITING


http://sourceware.org/bugzilla/show_bug.cgi?id=10128

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[Bug libc/10128] __libc_res_nquery fails if one answer returns NOERROR and the other NOTIMP or FORMERR

[aurelien at aurel32 dot net]

------- Additional Comments From aurelien at aurel32 dot net  2009-05-05 15:36 -------
> Where is such a server?
It's a DSL router, I don't have the exact reference.

> And why can you claim "common"?
I don't say "common", but "common among broken DNS software". A few Debian 
users reported the exact same problem. Google also has a few entries about this 
problem. And this is one of the problems about AAAA query listed during RIPE-48 
session:
http://www.ripe.net/ripe/meetings/ripe-48/presentations/ripe48-dns-malone.pdf

-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=10128

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[Bug libc/10128] __libc_res_nquery fails if one answer returns NOERROR and the other NOTIMP or FORMERR

[drepper at redhat dot com]

------- Additional Comments From drepper at redhat dot com  2009-05-09 16:12 -------
I've used the patch.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |RESOLVED
         Resolution|                            |FIXED


http://sourceware.org/bugzilla/show_bug.cgi?id=10128

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[Bug libc/10128] __libc_res_nquery fails if one answer returns NOERROR and the other NOTIMP or FORMERR

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=10128

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
              Flags|                            |security-

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