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* [Bug libc/11950] New: res_send fails with ETIMEDOUT on successful DNS UPDATE
@ 2010-08-27 5:22 dos at scarff dot id dot au
2010-08-27 5:23 ` [Bug libc/11950] " dos at scarff dot id dot au
2010-08-27 8:54 ` dos at scarff dot id dot au
0 siblings, 2 replies; 3+ messages in thread
From: dos at scarff dot id dot au @ 2010-08-27 5:22 UTC (permalink / raw)
To: glibc-bugs
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
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* [Bug libc/11950] res_send fails with ETIMEDOUT on successful DNS UPDATE
2010-08-27 5:22 [Bug libc/11950] New: res_send fails with ETIMEDOUT on successful DNS UPDATE dos at scarff dot id dot au
@ 2010-08-27 5:23 ` dos at scarff dot id dot au
2010-08-27 8:54 ` dos at scarff dot id dot au
1 sibling, 0 replies; 3+ messages in thread
From: dos at scarff dot id dot au @ 2010-08-27 5:23 UTC (permalink / raw)
To: glibc-bugs
------- Additional Comments From dos at scarff dot id dot au 2010-08-27 05:22 -------
Created an attachment (id=4951)
--> (http://sourceware.org/bugzilla/attachment.cgi?id=4951&action=view)
accept DNS UPDATE responses without RA set
--
http://sourceware.org/bugzilla/show_bug.cgi?id=11950
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* [Bug libc/11950] res_send fails with ETIMEDOUT on successful DNS UPDATE
2010-08-27 5:22 [Bug libc/11950] New: res_send fails with ETIMEDOUT on successful DNS UPDATE dos at scarff dot id dot au
2010-08-27 5:23 ` [Bug libc/11950] " dos at scarff dot id dot au
@ 2010-08-27 8:54 ` dos at scarff dot id dot au
1 sibling, 0 replies; 3+ messages in thread
From: dos at scarff dot id dot au @ 2010-08-27 8:54 UTC (permalink / raw)
To: glibc-bugs
------- Additional Comments From dos at scarff dot id dot au 2010-08-27 08:54 -------
Minor correction: testing again I see that res_send sets errno to ECONNREFUSED,
not ETIMEDOUT.
--
http://sourceware.org/bugzilla/show_bug.cgi?id=11950
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end of thread, other threads:[~2010-08-27 8:54 UTC | newest]
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2010-08-27 5:22 [Bug libc/11950] New: res_send fails with ETIMEDOUT on successful DNS UPDATE dos at scarff dot id dot au
2010-08-27 5:23 ` [Bug libc/11950] " dos at scarff dot id dot au
2010-08-27 8:54 ` dos at scarff dot id dot au
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