coder ssh hangs if the underlying network is down, rather than timing out. Here we are not talking about an idle connection, but one in which the user types something to send to the workspace, but the network is down.

We should give the underlying tailnet, say, 15 seconds (3x Wireguard handshake retries) to send the data and get a response, but if we go longer than this, it's safe to conclude the networking is dead and we should exit with an error.

stack trace of coder ssh waiting to send

Reproduction steps

Connect to a workspace with coder ssh
Disable WiFi and/or unplug Ethernet
Type some stuff at the frozen prompt