Unbound and unbound-control getting stuck

[Jef Driesen]

Hi,

I'm using unbound on my openwrt router. Openwrt uses unbound-control to add the 
dhcp leases (from odhcp) into the dns. This works fine, except that once in a 
while, unbound-control seems to get stuck and never returns, and I end up with a 
large number of unbound-control processes:

# ps | grep unbound-control
  2335 root      5988 S    /usr/sbin/unbound-control -c 
/var/lib/unbound/unbound.conf local_datas_remove
  2385 root      5988 S    /usr/sbin/unbound-control -c 
/var/lib/unbound/unbound.conf local_datas
  2428 root      5988 S    /usr/sbin/unbound-control -c 
/var/lib/unbound/unbound.conf local_datas
  2995 root      5988 S    /usr/sbin/unbound-control -c 
/var/lib/unbound/unbound.conf local_datas
  3839 root      5988 S    unbound-control -c /var/lib/unbound/unbound.conf 
stats_noreset
  3970 root      5988 S    unbound-control -c /var/lib/unbound/unbound.conf 
stats_noreset
  4090 root      5988 S    unbound-control -c /var/lib/unbound/unbound.conf 
stats_noreset
25060 root      5964 S    /usr/sbin/unbound-control -c 
/var/lib/unbound/unbound.conf local_datas_remove
25064 root      5964 S    /usr/sbin/unbound-control -c 
/var/lib/unbound/unbound.conf local_datas_remove
28771 root      5984 S    /usr/sbin/unbound-control -c 
/var/lib/unbound/unbound.conf local_datas_remove
29845 root      5984 S    /usr/sbin/unbound-control -c 
/var/lib/unbound/unbound.conf local_datas_remove
30351 root      5984 S    /usr/sbin/unbound-control -c 
/var/lib/unbound/unbound.conf local_datas
30681 root      5968 S    /usr/sbin/unbound-control -c 
/var/lib/unbound/unbound.conf local_datas_remove
30721 root      5968 S    /usr/sbin/unbound-control -c 
/var/lib/unbound/unbound.conf local_datas

At that point, dns resolving becomes also problematic:

$ dig aaaa google.es @192.168.1.1

; <<>> DiG 9.16.1-Ubuntu <<>> aaaa google.es @192.168.1.1
;; global options: +cmd
;; connection timed out; no servers could be reached

$ dig aaaa google.es @fd81:631b:716f:10::1

; <<>> DiG 9.16.1-Ubuntu <<>> aaaa google.es @fd81:631b:716f:10::1
;; global options: +cmd
;; connection timed out; no servers could be reached

Once I manually kill all those unbound-control processes, everything starts 
working again.

I have reported the problem on the openwrt forum:

https://forum.openwrt.org/t/issues-with-unbound-and-odhcp-setup/66354/26

The problem seems to be triggered by executing multiple unbound-control 
instances in parallel. Openwrt now contains a workaround to avoid doing this 
with a lockfile, but I suspect there is still some kind of bug present in 
unbound itself. Maybe some kind of deadlock condition?

Any ideas what could be the problem here?

Jef