I don't want to announce any DNS neither using RAs (RDNSS) nor DHCPv6 stateless, using odhcpd. However, if I don't set anything in /etc/config/dhcp it will always send the router's IPv6 address as DNS. I can also see this from Linux using rdisc6.
This is my config:
config dnsmasq option domainneeded '1' option boguspriv '1' option filterwin2k '0' option localise_queries '1' option rebind_protection '1' option rebind_localhost '1' option local '/lan/' option domain 'lan' option expandhosts '1' option nonegcache '0' option authoritative '1' option readethers '1' option leasefile '/tmp/dhcp.leases' option resolvfile '/tmp/resolv.conf.auto' option localservice '1' config dhcp 'lan' option interface 'wan' option ignore '1' option ra 'server' option ra_default '1' option ra_management '0' option ra_dns '0' # list dns '::1' # list domain '::1' config odhcpd 'odhcpd' option maindhcp '0' option leasefile '/tmp/hosts/odhcpd' option leasetrigger '/usr/sbin/odhcpd-update'
I've read so far that it is not possible to set the O-bit to zero (it is always on by default, even if M-flag is set to 0; i.e. M=0, O=1). But that shouldn't be a problem since I didn't setup DHCPv6 for the interface anyways. And even though I set "option ra_dns '0'", I still see RDNSS information in the router advertisements.
Only workaround seems to be to set "list dns" to something like "::1". I really don't want any DNS to be published. Just IPv6 address and default gateway using SLAAC.