I would like to use OpenWrt 21.02.3 with a wireguard tunnel such that once the wireguard tunnel is established, all traffic moves through the tunnel and the remote DNS is used. Until the tunnel is established, the DHCP provided DNS should be used (i.e. wifi clients use OpenWrt as DNS, and dnsmasq on OpenWrt forwards requests appropriately). Is it ok/sufficient for this purpose to specify a DNS for the wireguard interface and leave everything else as it is?
I am asking, because once the tunnel has been established, the dhcp DNS in resolv.conf is not replaced with the wireguard DNS, but the wireguard DNS is just added as another option. Is this correct?
root@OpenWrt:~# cat /tmp/resolv.conf.d/resolv.conf.auto
# Interface trm_wwan6
nameserver fe80::84ad:8dff:fead:5e64%wlan1
# Interface wg0
nameserver 192.168.1.102
# Interface trm_wwan
nameserver 172.20.10.1
(trm_wwan6 and trm_wwan nameservers are dhcp provided, wg0 is the one I configured.)
root@OpenWrt:~# uci show network
network.loopback=interface
network.loopback.device='lo'
network.loopback.proto='static'
network.loopback.ipaddr='127.0.0.1'
network.loopback.netmask='255.0.0.0'
network.globals=globals
network.globals.ula_prefix='fd97:6241:a239::/48'
network.@device[0]=device
network.@device[0].name='br-lan'
network.@device[0].type='bridge'
network.@device[0].ports='eth0.1'
network.lan=interface
network.lan.device='br-lan'
network.lan.proto='static'
network.lan.ipaddr='192.168.168.1'
network.lan.netmask='255.255.255.0'
network.lan.ip6assign='60'
network.wan=interface
network.wan.device='eth0.2'
network.wan.proto='dhcp'
network.wan6=interface
network.wan6.device='eth0.2'
network.wan6.proto='dhcpv6'
network.@switch[0]=switch
network.@switch[0].name='switch0'
network.@switch[0].reset='1'
network.@switch[0].enable_vlan='1'
network.@switch_vlan[0]=switch_vlan
network.@switch_vlan[0].device='switch0'
network.@switch_vlan[0].vlan='1'
network.@switch_vlan[0].ports='2 3 0t'
network.@switch_vlan[1]=switch_vlan
network.@switch_vlan[1].device='switch0'
network.@switch_vlan[1].vlan='2'
network.@switch_vlan[1].ports='1 0t'
network.trm_wwan=interface
network.trm_wwan.proto='dhcp'
network.trm_wwan.metric='100'
network.trm_wwan6=interface
network.trm_wwan6.device='@trm_wwan'
network.trm_wwan6.proto='dhcpv6'
network.wg0=interface
network.wg0.proto='wireguard'
network.wg0.private_key='xxx'
network.wg0.addresses='10.7.0.2' '192.168.168.0/24'
network.wg0.peerdns='0'
network.wg0.dns='192.168.1.102'
network.@wireguard_wg0[0]=wireguard_wg0
network.@wireguard_wg0[0].description='Wireguard'
network.@wireguard_wg0[0].public_key='xxx'
network.@wireguard_wg0[0].allowed_ips='0.0.0.0/0'
network.@wireguard_wg0[0].route_allowed_ips='1'
network.@wireguard_wg0[0].endpoint_host='gateway.example.com'
network.@wireguard_wg0[0].persistent_keepalive='25'