No DNS after 18.06-rc2 upgrade

I've got a D-Link DIR-869 working as a secondary AP only. WAN is not connected and one of the LAN ports is connected to a LAN port of main main router/AP.

This is how my /etc/config/network looks like for WAN (there's no other definition of DNS):

config interface 'lan'
        option type 'bridge'
        option ifname 'eth0.1'
        option proto 'static'
        option netmask ''
        option ip6assign '60'
        option ipaddr ''
        option gateway ''
        option dns ''

Now I understand that /tmp/resolv.conf and /tmp/ are somehow related to the DNS configuration and actually in /tmp/ I have my DNS server correctly set:

root@wlan-ap-dlink:~# ls -l /etc/resolv.conf
lrwxrwxrwx    1 root     root            16 Jul 15 15:30 /etc/resolv.conf -> /tmp/resolv.conf
root@wlan-ap-dlink:~# cat /tmp/resolv.conf
search lan
root@wlan-ap-dlink:~# cat /tmp/
# Interface lan

However, DNS resolution does not work:

root@wlan-ap-dlink:~# ping
ping: bad address ''

This worked fine in LEFE 17.01.4 that I was running before. How is the /tmp/ file used?

Does it work after /etc/init.d/dnsmasq restart ?