Date: Sat, 20 May 2017 16:58:48 +0000 (UTC) From: Cy Schubert <cy@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r318578 - head/usr.sbin/nscd Message-ID: <201705201658.v4KGwnjk014611@repo.freebsd.org>
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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 <amutu@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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