This is the mail archive of the
glibc-bugs@sourceware.org
mailing list for the glibc project.
[Bug libc/11950] New: res_send fails with ETIMEDOUT on successful DNS UPDATE
- From: "dos at scarff dot id dot au" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sources dot redhat dot com
- Date: 27 Aug 2010 05:21:44 -0000
- Subject: [Bug libc/11950] New: res_send fails with ETIMEDOUT on successful DNS UPDATE
- Reply-to: sourceware-bugzilla at sourceware dot org
In the glibc resolver (previous versions and current git HEAD), res_send
interprets some successful DNS UPDATE responses as an indication to retry with
the next server, because of this test in res_send.c:
if (anhp->rcode == NOERROR && anhp->ancount == 0
&& anhp->aa == 0 && anhp->ra == 0 && anhp->arcount == 0) {
This test is nonsensical for DNS UPDATE, where the "AA" and "RA" flags are part
of the much larger Z bitfield, see
http://tools.ietf.org/html/rfc2136#page-5
for more information. This issue appears to be limited to UDP queries in
send_dg(). The end result is that res_send returns failure and sets ETIMEDOUT.
This issue will not occur for all DNS servers; those which allow recursion
(e.g. BIND9 without recursion disabled) will set the RA bit anyway.
Unfortunately, it's hard to generate a simple test case due to the nature of
DNS UPDATE (needs crypto, a current timestamp, and a configured server). I am
experiencing this issue when using res_send in the context of the dudders DNS
UPDATE client: http://dudders.sourceforge.net/
Patch attached.
--
Summary: res_send fails with ETIMEDOUT on successful DNS UPDATE
Product: glibc
Version: unspecified
Status: NEW
Severity: normal
Priority: P2
Component: libc
AssignedTo: drepper at redhat dot com
ReportedBy: dos at scarff dot id dot au
CC: glibc-bugs at sources dot redhat dot com
http://sourceware.org/bugzilla/show_bug.cgi?id=11950
------- You are receiving this mail because: -------
You are on the CC list for the bug, or are watching someone who is.