[Dnsmasq-discuss] doc: upstream server selection algorithm

HONTVÁRI Levente hontvari at flyordie.com
Mon Jan 25 09:22:39 GMT 2016


Hello All,

I would like to make an enhancement request regarding the documentation 
of the upstream server selection algorithm. I assumed that only the 
first server is tried if it responds within timeout. However, I noticed 
in my Dnsmasq log, that Dnsmasq uses both upstream servers. I thought 
that there may be a problem with the first server, so I started to debug 
the issue, Unfortunately, Bind 9.9 has no easy configuration option to 
log DND replies (it only logs them on debug level 4, but that also means 
a huge level amount of nonrelevant information). Finally tcpdump helped, 
and I bacame sure that the first upstream server responds timely.

On the man page the only relevan info I found about the subject is this:

*--all-servers*
    By default, when dnsmasq has more than one upstream server
    available, it will send queries to just one server. Setting this
    flag forces dnsmasq to send all queries to all available servers.
    The reply from the server which answers first will be returned to
    the original requester. 

This description seems to be obsolete. After reading the changelog I 
noticed another information:

Test which upstream nameserver to use every 10 seconds
             or 50 queries and not just when a query times out and
             is retried. This should improve performance when there
             is a slow nameserver in the list. Thanks to Joe for the
             suggestion.

This seems to valid, at least it is plausible.

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