[kea-dev] Raw socket input buffer

[Francis Dupont]

kea at jack.fr.eu.org writes:
> I have a kea4 server, version 1.1.0, I added hooks that connect
> externally (the important information : that hook is "slow", it does TCP
> connect)
> That part works well
> 
> However, when the server takes too many queries (I don't know how "too
> many" is), a strange behavior appears: the server keep and answer
> outdated requests (some kind of input buffer, I guess), which clients
> timed-out in the mean time, leading to another requests etc -> broadcast
> storm and global failure

=> as your tentative fix suggested this is a kernel issue: pending
queries are simply queued waiting Kea to read them. IMHO the best is
to add some code in the slow hook to flush them.

> I tried to reduce /proc/sys/net/core/rmem_max to 4096, this does not fix
> the issue (probably because 4096 is still a lot of dhcp-packets :p)
> 
> Any tip, trick, configuration or whatever on that issue ?

=> slow processing is incompatible with the DHCP protocol so basically
there is no final fix, only tricks to make things less broken.

Regards

Francis Dupont <fdupont at isc.org>