Author: cy
Date: Sat May 20 16:58:48 2017
New Revision: 318578
URL: https://svnweb.freebsd.org/changeset/base/318578
Log:
Fix non-recoverable name resolution failures due to negative cache
entries never expiring. This patch honours the negative cache timeout.
To test/experience the failure do the following:
1. Edit /etc/ncd.conf to adjust the cache timeouts as follows:
positive-time-to-live hosts 30
negative-time-to-live hosts 1
2. Ensure that nsswitch.conf hosts line contains something like:
hosts: files cache dns
Note that cache must be specified before dns.
3. Start nscd.
4. Run the following command:
while true; do nc -z -w 3 www.google.com 80; sleep 5; done
5. While running the command, remove or comment out all nameserver
statements in /etc/resolv.conf. After a short while you will notice
non-recoverable name rsolution failures.
6. Uncomment or replace all nameserver statements back into
/etc/resolv.conf. Take note that name resolution never recovers.
To recover nscd must be restarted. This patch fixes this.
PR: 207804
Submitted by: Jov <am...@amutu.com>
MFC after: 1 week
Modified:
head/usr.sbin/nscd/query.c
Modified: head/usr.sbin/nscd/query.c
==============================================================================
--- head/usr.sbin/nscd/query.c Sat May 20 16:47:00 2017 (r318577)
+++ head/usr.sbin/nscd/query.c Sat May 20 16:58:48 2017 (r318578)
@@ -743,9 +743,14 @@ on_read_request_process(struct query_sta
&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);
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