[dnsdist] dnstap logs CLIENT_RESPONSES only, when the queried RR is not in cache

Tom lists at verreckte-cheib.ch
Fri Aug 27 06:21:14 UTC 2021


Using dnsdist-1.6.0, a packet-cache-configuration and a dnstap 
(newFrameStreamUnixLogger) configuration, which is configured for 
logging responses too:

I have noticed that in the dnstap-logs the CLIENT_RESPONSE only appears, 
when dnsdist has NO cache entry for this request. Ever client-query, 
which can be answered from the dnsdist-cache will only be logged with 
"CLIENT_QUERY" and not additional with CLIENT_RESPONSE.

Look here:

# initial query (dnsdist hast empty cache) for mx google.com will be 
logged with dnstap (CLIENT_QUERY and CLIENT_RESPONSE):
2021-08-27T06:09:35.541094903Z server01 CLIENT_QUERY NOERROR 
55177 INET UDP 51b google.com MX 0.000000
2021-08-27T06:09:35.557156637Z server01 CLIENT_RESPONSE NOERROR 55177 INET UDP 185b google.com MX 0.016062

# 2nd, third, fourth etc. query for the same RR will only be logged with 
2021-08-27T06:11:11.711001431Z server01 CLIENT_QUERY NOERROR 
54555 INET UDP 51b google.com MX 0.000000
2021-08-27T06:11:13.238908856Z server01 CLIENT_QUERY NOERROR 
48615 INET UDP 51b google.com MX 0.000000
2021-08-27T06:11:14.16733849Z server01 CLIENT_QUERY NOERROR 
57005 INET UDP 51b google.com MX 0.000000
2021-08-27T06:11:14.776923103Z server01 CLIENT_QUERY NOERROR 
37766 INET UDP 51b google.com MX 0.000000

# the cache-dump looks like this:
; dnsdist's packet cache dump follows
google.com. 488 MX ; rcode 0, key 4146178086, length 185, tcp 0, added 

When I clear the cache (getPool("poolname"):getCache():expunge(0)) or 
restart dnsdist, then every first not cached query is logged again with 

Any hints for this?

Many thanks.
Kind regards,

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