After months of everything working fine, I upgraded one of my nodes to 1.8.0 (via the plugin manager on FreeNAS).
The other side is a Mac, running 1.7.0.
Now I see this on the 1.8.0 side: " 2020-08-18 20:05:43: Bad certificate from atto at 172.16.0.2:38865-198.245.49.122:22067/relay-server/TLS1.3-TLS_AES_128_GCM_SHA256: x509: certificate relies on legacy Common Name field, use SANs or temporarily enable Common Name matching with GODEBUG=x509ignoreCN=0"
Unfortunately I guess they built with Go 1.15 which doesn’t work on that version. (I’m surprised it isn’t also panicking due to the QUIC incompatibility.) You can downgrade or complain to the packager.
Or set GODEBUG=x509ignoreCN=0 somewhere in the startup.