Date: Tue, 27 Aug 2013 16:50:38 GMT From: "Oleg A. Mamontov" <oleg@mamontov.net> To: freebsd-gnats-submit@FreeBSD.org Subject: bin/181586: nscd negative responses Message-ID: <201308271650.r7RGocIu019008@oldred.freebsd.org> Resent-Message-ID: <201308271700.r7RH00Y6036648@freefall.freebsd.org>
next in thread | raw e-mail | index | archive | help
>Number: 181586
>Category: bin
>Synopsis: nscd negative responses
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Tue Aug 27 17:00:00 UTC 2013
>Closed-Date:
>Last-Modified:
>Originator: Oleg A. Mamontov
>Release: 9.1-RELEASE-p4
>Organization:
>Environment:
FreeBSD lonerr.jail.local 9.1-RELEASE-p4 FreeBSD 9.1-RELEASE-p4 #0: Mon Jun 17 11:42:37 UTC 2013 root@amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC amd64
>Description:
nscd (8) daemon caches negative responses for infinite time.
Parameter 'negative-time-to-live' in /etc/nscd.conf doesn't correct this behavior.
>How-To-Repeat:
Try set 'negative-time-to-live hosts 1' in /etc/nscd.conf and 'hosts: files cache dns' in /etc/nsswitch.conf.
Restart nscd: '/etc/rc.d/nscd onerestart'.
Now we can see output of 'tcpdump udp and port 53' and repeat many times: 'ping -c1 some.nonexistent'.
Only first time there will be actual dns search (with expected negative response).
>Fix:
Supplied below corrects nscd behaviour on 9.1-RELEASE-p4 and HEAD:
--- usr.sbin/nscd/query.c.orig 2013-08-22 11:59:03.921956888 +0400
+++ usr.sbin/nscd/query.c 2013-08-22 12:00:01.515957178 +0400
@@ -743,9 +743,14 @@
&read_response->data_size);
if (read_response->error_code == -2) {
- read_response->error_code = 0;
- read_response->data = NULL;
- read_response->data_size = 0;
+ read_response->data = malloc(
+ read_response->data_size);
+ assert(read_response != NULL);
+ read_response->error_code = cache_read(neg_c_entry,
+ read_request->cache_key,
+ read_request->cache_key_size,
+ read_response->data,
+ &read_response->data_size);
}
}
configuration_unlock_entry(qstate->config_entry, CELT_NEGATIVE);
>Release-Note:
>Audit-Trail:
>Unformatted:
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201308271650.r7RGocIu019008>