[Unbound-users] How to config whitelist for EDNS client subnetin unbound

Yuri Schaeffer yuri at nlnetlabs.nl
Tue Dec 30 09:49:41 UTC 2014

Hash: SHA1

Hi Kun,

Thank you for your feedback!

Apart from the TTL issue it sounds like the software works as
advertised. The authority server indicated lack of ECS support so we
cache that information. This strategy greatly improves performance for
all non-ECS domains. (Read: it will keep stock Unbound performance)
Once the TTL expires the server is probed again.

How do you propose Unbound should decide this information is a lie,
sometimes...? Would you be willing to sacrifice performance for all
non-ECS lookups greatly?


On 12/24/2014 10:07 AM, 余坤 wrote:
> Hi Larry, Yuri After a few days of testing, I'm afraid that this
> branch is not ready for production use yet. First, just like Larry
> has pointed out, RTT value in ECS cache does not decrease. Second,
> when a domain supports ECS partially, unbound may cache suboptimal
> results. For instance, www.qq.com <http://www.qq.com> supports ECS
> in China, i.e. all name servers of qq.com <http://qq.com> in China
> responses correctly when ECS is set in the query. But qq.com 
> <http://qq.com> uses Akamai to deliver contents outside China.
> When unbound receives a query of www.qq.com <http://www.qq.com>
> with client= <>, the name server of
> qq.com <http://qq.com> will redirect this query to Akamai. As we
> all know, Akamai doesn's support ECS, so name server of Akamai will
> rerurn a resource record without ECS option. This record ends up in
> the ordinary cache of unbount! How did I find out this record is
> cached in the ordinary cache? Because the TTL value of this records
> does decrease! So subsequent queries of qq.com <http://qq.com>
> without ECS option will be replied with an IP address in America!
> This may cause severe performance downgrade. A more specific
> example: dig @ <> www.qq.com
> <http://www.qq.com> ;; ANSWER SECTION: www.qq.com
> <http://www.qq.com>.300INA115.25.209.39  <= IP in Beijing China
> ./dig @ <> www.qq.com 
> <http://www.qq.com> +client= <> ;;
> OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 4096 ;
> QUESTION SECTION: ;www.qq.com <http://www.qq.com>.INA
> ;; ANSWER SECTION: www.qq.com
> <http://www.qq.com>.300INA175.155.116.108 <= IP in another city of
> China
> So far so good, now ask unbound with an IP address in America:
> ./dig @ <> www.qq.com 
> <http://www.qq.com> +client= <> ;; OPT
> PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 4096 ;
> SECTION: ;www.qq.com <http://www.qq.com>.INA
> ;; ANSWER SECTION: www.qq.com
> <http://www.qq.com>.299INCNAMEqq.com.edgesuite.net 
> <http://qq.com.edgesuite.net>. qq.com.edgesuite.net 
> <http://qq.com.edgesuite.net>.21600INCNAMEa1574.b.akamai.net 
> <http://a1574.b.akamai.net>. a1574.b.akamai.net
> <http://a1574.b.akamai.net>.20INA23.201.102.40  <= Akamai's IP
> address a1574.b.akamai.net
> <http://a1574.b.akamai.net>.20INA23.201.102.41
> Now query unbound without ECS option: ./dig @
> <> www.qq.com <http://www.qq.com> ;; ANSWER
> SECTION: www.qq.com
> <http://www.qq.com>.292INCNAMEqq.com.edgesuite.net 
> <http://qq.com.edgesuite.net>. qq.com.edgesuite.net 
> <http://qq.com.edgesuite.net>.21593INCNAMEa1574.b.akamai.net 
> <http://a1574.b.akamai.net>. a1574.b.akamai.net
> <http://a1574.b.akamai.net>.13INA23.201.102.40  <= Still Akamai's
> address! a1574.b.akamai.net
> <http://a1574.b.akamai.net>.13INA23.201.102.41
> ;; Query time: 0 msec <= get result from cache
> In this way, unbound stores a sub optimal record in the main
> cache, subsequent queries will all get this record. This is not
> acceptable because it will cause too much inter-continent traffic. 
> Since ECS is not a RFC yet, I assume partial support of ECS is
> quite common. Return sub optimal results to clients can cause
> serious performance problems. IMHO, unbound should provide a way to
> config which domain should be stored in ECS cache. In this way,
> even some of the name servers of a domain do not support ECS, all
> the records of this domain will be stored in ECS cache. Records
> without ECS information will have a subnet of
> <>. The best choice can be determined by longest
> prefix match of client subnet.
> Regards, Kun
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