I was trying to enable DNS over TLS via systemd-resolved. I changed /etc/systemd/resolved.conf as follows:
[Resolve]
DNS=1.1.1.1
#FallbackDNS=
Domains=~.
#LLMNR=no
#MulticastDNS=no
#DNSSEC=no
DNSOverTLS=opportunistic
#Cache=yes
#DNSStubListener=yes
While monitoring the network (with tcpdump) to see if the resulting behavior was the intended one, it seems that a TLS session is established with the target server; but, then the server closes the connection. I get the same results with 1.1.1.1, 8.8.8.8 and others.
Any ideas on how to fix this?
P.S.: systemd-resolved ends up doing parallel resolution with traditional DNS (despite the setting of "Domains" above). But my main question for this post is what may be going wrong with the TLS one.