I wonder if there's any way to set this flag without running a forked version of warp - right now I'm running a cronjob which restarts my service every 3 hours, because otherwise after 4 hours I hit 65535 ESTABLISHED connections and new connections start failing...

You could also configure default keep alive at the operating system level.

Searching for how to do that, all the sources I've found (eg [0]) say "you can tweak the default timeout at the OS level, but the application needs to opt-in to having keepalive enabled in the first place" :(

Alternatively if there's some other way to avoid leaking sockets, I'm all ears - I assume that's the end goal of this feature request either way? Briefly looking at eg nginx and varnish, they seem to be proactively closing idle connections after 75 or 60 seconds[1][2] rather than using TCP socket options, but I didn't see an option for warp to use the explicit-timeout approach either. (Apologies if this issue is specifically requesting TCP timeouts and other forms of idle-timeout are off-topic)

[0] https://tldp.org/HOWTO/TCP-Keepalive-HOWTO/usingkeepalive.html
[1] https://nginx.org/en/docs/http/ngx_http_core_module.html#keepalive_timeout
[2] https://varnish-cache.org/docs/6.6/reference/varnishd.html#ref-param-idle-send-timeout

Indeed, OS cannot really enable application-level keepalives as they are required to be by default off at the socket. The application needs to set them on explicitly. I tried this way first quite thoroughly.

Pulling #1075 would be a nice fix, reformatting issue.