[dns-operations] Heads up Linux IPv6 users: larger scale use may require kernel tuning

Hannes Frederic Sowa hannes at stressinduktion.org
Fri Feb 28 18:34:02 UTC 2014

On Fri, Feb 28, 2014 at 10:24:11AM -0800, Donovan, Chris wrote:
> Why does this effect a DNS server? In many cases, I would expect the
> routing table to be small (default route + some static routes). Does Linux
> need to add a route for each client that is connecting to it or are we
> talking about a scenario where the Linux host is participating in dynamic
> routing protocols and just received more routes than originally expected?

Current situation is that every lookup is cloned, the prefix in the
routing node is overwritten with the address and reinserted back into
the fib. Later gc invocations if fib exceeds the number of the maximum
number of routes triggers an in-path execution of gc, which may be costly
as we have to hold write_lock on the table the whole time, too.

Dicussion on netdev: http://thread.gmane.org/gmane.linux.network/306098



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