Maintained by: NLnet Labs

[Unbound-users] The flush command of unbound-control doesn't take effect.

W.C.A. Wijngaards
Mon Feb 23 09:50:23 CET 2015


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Hi Hongyi,

On 23/02/15 03:49, Hongyi Zhao wrote:
> Hi all,
> 
> Currently, I use the latest release of unbound 1.5.2 compilled by
> myself on the Debian wheezy.  I configured the unbound by some
> using some forward-zone sections in its unbound.conf  file, and let
> it  listen on the local 1052 port to listen on for queries.
> 
> Now, I want to use the unbound-control tool to do some tests, say, 
> cleaning some type of record in the cache, say, the A record, by
> using the following command:
> 
> $ sudo unbound-control -c 
> /home/werner/software/anti-gfw/anti-DNS-cache-poisoning/final-methods/unbound.conf
>
> 
flush A

You flush here the domain-name "A".  The command expects a domain
name, so like: flush example.com removes the example.com A record.

Best regards,
   Wouter

> But I failed to clean the cache, please see following for detail:
> 
> -------------- begin test ------------------------------ 
> werner at debian:~$ dig -p1052 youtube.com <http://youtube.com>
> 
> ; <<>> DiG 9.8.4-rpz2+rl005.12-P1 <<>> -p1052 youtube.com 
> <http://youtube.com> ;; global options: +cmd ;; Got answer: ;;
> ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 20966 ;; flags: qr
> rd ra; QUERY: 1, ANSWER: 11, AUTHORITY: 0, ADDITIONAL: 0
> 
> ;; QUESTION SECTION: ;youtube.com <http://youtube.com>.
> IN    A
> 
> ;; ANSWER SECTION: youtube.com <http://youtube.com>.        3600
> IN    A    173.194.127.40 youtube.com <http://youtube.com>.
> 3600    IN    A    173.194.127.38 youtube.com <http://youtube.com>.
> 3600    IN    A    173.194.127.41 youtube.com <http://youtube.com>.
> 3600    IN    A    173.194.127.35 youtube.com <http://youtube.com>.
> 3600    IN    A    173.194.127.39 youtube.com <http://youtube.com>.
> 3600    IN    A    173.194.127.46 youtube.com <http://youtube.com>.
> 3600    IN    A    173.194.127.37 youtube.com <http://youtube.com>.
> 3600    IN    A    173.194.127.32 youtube.com <http://youtube.com>.
> 3600    IN    A    173.194.127.34 youtube.com <http://youtube.com>.
> 3600    IN    A    173.194.127.36 youtube.com <http://youtube.com>.
> 3600    IN    A    173.194.127.33
> 
> ;; Query time: 715 msec ;; SERVER: 127.0.0.1#1052(127.0.0.1) ;;
> WHEN: Mon Feb 23 10:33:41 2015 ;; MSG SIZE  rcvd: 205
> 
> werner at debian:~$ sudo unbound-control -c 
> /home/werner/software/anti-gfw/anti-DNS-cache-poisoning/final-methods/unbound.conf
>
> 
flush A
> ok werner at debian:~$ dig -p1052 youtube.com <http://youtube.com> ;
> <<>> DiG 9.8.4-rpz2+rl005.12-P1 <<>> -p1052 youtube.com 
> <http://youtube.com> ;; global options: +cmd ;; Got answer: ;;
> ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 22618 ;; flags: qr
> rd ra; QUERY: 1, ANSWER: 11, AUTHORITY: 0, ADDITIONAL: 0
> 
> ;; QUESTION SECTION: ;youtube.com <http://youtube.com>.
> IN    A
> 
> ;; ANSWER SECTION: youtube.com <http://youtube.com>.        3584
> IN    A    173.194.127.40 youtube.com <http://youtube.com>.
> 3584    IN    A    173.194.127.38 youtube.com <http://youtube.com>.
> 3584    IN    A    173.194.127.41 youtube.com <http://youtube.com>.
> 3584    IN    A    173.194.127.35 youtube.com <http://youtube.com>.
> 3584    IN    A    173.194.127.39 youtube.com <http://youtube.com>.
> 3584    IN    A    173.194.127.46 youtube.com <http://youtube.com>.
> 3584    IN    A    173.194.127.37 youtube.com <http://youtube.com>.
> 3584    IN    A    173.194.127.32 youtube.com <http://youtube.com>.
> 3584    IN    A    173.194.127.34 youtube.com <http://youtube.com>.
> 3584    IN    A    173.194.127.36 youtube.com <http://youtube.com>.
> 3584    IN    A    173.194.127.33
> 
> ;; Query time: 0 msec ;; SERVER: 127.0.0.1#1052(127.0.0.1) ;; WHEN:
> Mon Feb 23 10:33:57 2015 ;; MSG SIZE  rcvd: 205 -------------- end
> test ------------------------------
> 
> As you can see, after I've done the flush operation  on the A
> record, the 2nd dig command still can fetech the cached A records
> -- "the Query time: 0 msec" of the 2nd run of dig should tell
> this.
> 
> Why does this happen?  Could someone please give me some hints?
> 
> Regards -- Hongyi Zhao <hongyi.zhao at gmail.com
> <mailto:hongyi.zhao at gmail.com>> Xinjiang Technical Institute of
> Physics and Chemistry Chinese Academy of Sciences GnuPG DSA:
> 0xD108493
> 
> 
> _______________________________________________ Unbound-users
> mailing list Unbound-users at unbound.net 
> http://unbound.nlnetlabs.nl/mailman/listinfo/unbound-users
> 

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