Bind to dual-stack socket by default [IPv6]

[margau]

I've been trying to set up the notify_push daemon using a reverse proxy on another machine.
The internal network is IPv6 only (as we're living in 2021).
Unfortunately, the daemon does not start an IPv6 Socket on ::, but only a Legacy Socket:

tcp 0 0 0.0.0.0:7867 0.0.0.0:* LISTEN 8246/notify_push

I'd suggest using a Socket bound to :: with the IPV6_V6ONLY socket option deactivated. That way, both IPv6 and Legacy will be supported in a single socket.

As a workaround, you can set "Environment=BIND=::" to force listening on IPv6. 9f67831 as given in #47 does not fix this, as it does not work when the reverse proxy does communicate only over IPv6.

[ransty]

Hey there

I have pulled the latest main to test out in our Docker container and because we specifically only bind to IPv4, and remove the IPv6 stack, the binary fails to run due to this stack trace:

nextcloud_push  | Error:   × Main thread panicked.
nextcloud_push  |   ├─▶ at /opt/cargo/registry/src/index.crates.io-1949cf8c6b5b557f/warp-0.3.7/         
nextcloud_push  |   │   src/server.rs:291:27     nextcloud_push  |   ╰─▶ error binding to [::]:7867: error creating server listener: Address    
nextcloud_push  |       family not supported by protocol (os error 97)     
nextcloud_push  |   help: set the `RUST_BACKTRACE=1` environment variable to display a   
nextcloud_push  |         backtrace.

So while this is on my environment for not supporting IPv6 yet, how can I get past this without patching the commit?

[icewind1991]

You can change what address is listened to by setting the BIND environment variable.

For the next version it should automatically fall back to ipv4 if ipv6 is unavailable (#710)