@ryanc something causing intermittent broadcast storms? something stealing the MAC addr or IP addr of your DNS resolver? something making dnsmasq hang, maybe it was trying to write to something very slow, eg. logs on a broken disk?

@fanf I'm going to give it to you for this, it was dnsmasq calling fsync(2) on the dhcp leases file, which happens fairly frequently because I've got about 80 DHCP clients on my home network.

I have resolved it by LD_PRELOADing libeatmydata.

@mdione @fanf I didn't dig into the code, but I believe it is single threaded, and fsync is always blocking by design even on an otherwise non-blocking file descriptor.

But. In common configurations, fsync also has to wait on any other writes that were pending on the same filesystem.