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

["aurelien at aurel32 dot net" <sourceware-bugzilla at sourceware dot org>]

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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