rumqttc: Add bind_device to NetworkOptions to enable TCPSocket.bind_device()

[seimonw]

Allows the network connection to be optionally bound to a specific interface.
See also: https://docs.rs/tokio/latest/tokio/net/struct.TcpSocket.html#method.bind_device

Type of change

New feature (non-breaking change which adds functionality)

Checklist:

• Formatted with cargo fmt
• Make an entry to CHANGELOG.md if its relevant of user of the library. If its not relevant mention why.

[h3nill]

else LGTM, but can you explain the use case for this?

[seimonw]

else LGTM, but can you explain the use case for this?

It can be used to force the connection to go via a specific network which may not be the default route. I would like to use it to maintain two independent connections to a server. I can verify the backup network route's connectivity while the primary (default) route is still active.

[seimonw]

What's the latest with this PR @henil - it seems to have stalled. Is there anything more I can do?

[h3nill]

Hey, sorry for the delay. we have backlog of things to review and merge but we dont have enough bandwidth. I will try to get this reviewed and merged by this month.

[seimonw]

No worries - I noticed that clippy in the workflow didn't like the #cfg(all(any from tokio so have pushed without the all in there. Sorry - I didn't see that issue locally.

[h3nill]

Thank you @seimonw! 🎉