Add knot-resolver so we can do DNS resolution.

We add the http module so we can get prometheus metrics as well.

Dockerfile

@@ -22,7 +22,7 @@ COPY --from=build /usr/sbin/openvpn /usr/sbin/openvpn
 COPY --from=build /go/bin/openvpn_exporter /usr/local/bin/openvpn_exporter
 COPY chaperone.d/ /etc/chaperone.d
 RUN apt-get -q update && env DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends \
-        openvpn libcap2-bin netcat-openbsd iptables\
+        openvpn libcap2-bin netcat-openbsd iptables knot-resolver knot-resolver-module-http \
         && rm -rf /var/lib/apt/lists/*
 RUN setcap cap_net_admin,cap_net_bind_service+ep /usr/sbin/openvpn
 RUN setcap cap_net_admin+ep /bin/ip