"Network is unreachable" error returned when IPv6 is disabled and network is reachable using IPv4

This is migrated from evolution#1099 (closed). The problem is basically that glib reports "network is unreachable" when the actual problem is not even close to the message.

Sorry, the smallest steps-to-reproduce I have involve using glib through Evolution. The investigation that found glib/gio to be the culprit you can see at this comment.

To reproduce you basically click through mail setup wizard till Sending email screen, in which you set smtp.gmail.com as server and port 587, and click "Check for supported types" button. Alternatively, create an account with the "sending" address:port as noted above, and try sending yourself a email.

Steps to reproduce

1. Open evolution
2. Click Edit → Accounts → Add → Mail Account
3. Identity screen: use foo@example.com as email address, uncheck "Look up mail server details…", click next
4. Receiving Email screen: use 1.1.1.1 as IMAP server and foo for username, click next (skip server lookup)
5. Sending Email screen: type smtp.gmail.com as server, choose 587 as port number, check Server requires authentication, then press the button Check for Supported Types

Expected

You'll get an error "Error performing TLS handshake: An unexpected TLS packet was received." or a similar one about TLS failure.

Actual

You'll get Could not connect to smtp.gmail.com: Network is unreachable, which is completely wrong as everything, starting the network and ending with the port, is reachable.

Versions

• glib2 2.66.0