feat: add `bind_addr` for `NetworkOptions` to enable `TCPSocket.bind()`

[caoruijuan13]

Type of change

Checklist:

• [x] Formatted with cargo fmt
• [x] Make an entry to CHANGELOG.md if it's relevant to the users of the library. If it's not relevant mention why.

[swanandx]

hey @caoruijuan13 , thanks for the contribution, can you please elaborate more on why this is required?

[caoruijuan13]

hey @caoruijuan13 , thanks for the contribution, can you please elaborate more on why this is required?

In my actual use, I need to bind specific address(the default interface address usually, maybe x.x.x.x:0) for the client to avoid routing loop, maybe others need it too.

[cavivie]

Fortunately I took another look at the PR list, otherwise I would have done this again.

Our company now has a multi-platform and multi network devices scenario test. This will cause the bind device to be unable to bind specific address routing in scenarios such as macOS/iOS/Windows. Since the routing characteristics of different platforms are different, it is difficult to use simple routing. Control is achieved by simply binding addresses for rumqtt to avoid re-routing decisions to achieve the same effect, which is really awesome and we need it too.

[cavivie]

@flxo @swanandx I wonder what's stopping us from going further now?

[swanandx]

@flxo @swanandx I wonder what's stopping us from going further now?

same changes needs to be done for v5 client as well. And i think the discussion about what to do incase it fails to convert to sockeraddr isn't resolved right?

[cavivie]

same changes needs to be done for v5 client as well.

The v5 client is already supported because v5 MqttOptions NetworkOptions references the already implemented lib NetworkOptions, doesn't it?

And i think the discussion about what to do incase it fails to convert to sockeraddr isn't resolved right?

As I said before, we use SocketAddr directly instead of ToSocksAddr, isn't this solution enough to solve this problem? I think the conversion is handled by the caller rather than in this non-low-level crate, what you think so?

UDP: If you agree with all of these, then we push this PR author change to go further.

[swanandx]

The v5 client is already supported because v5 MqttOptions NetworkOptions references the already implemented lib NetworkOptions, doesn't it?

that is bind_device which is different from bind_addr right? if not, bind_device already exists for v4 client, so we don't even need anything.

I think the conversion is handled by the caller rather than in this non-low-level crate, what you think so?

didn't get it, wdym?

[cavivie]

that is bind_device which is different from bind_addr right? if not, bind_device already exists for v4 client, so we don't even need anything.

bind_addr is different from bind_device. bind_addr: Bind a socket to a socket address like "192.168.128.1:8080". bind_device: Bind a socket to a particular device like "eth0", as specified in the passed interface name.

Currently v5 and non-v5 share the same NetworkOptions struct and eventloop socket_connect function, it only needs to be implemented in one place, and the other place will be automatically implemented. For non-v5, just set NetworkOptions directly on MqttOptions, but for v5, need to create NetworkOptions and set it into the EventLoop struct.

If it’s still unclear, I have a PR here to make v5 and non-v5 network options consistent in the way they are used externally.

didn't get it, wdym?

Use the (recommend) way:

/// callers can call `set_bind_address(addr: SocketAddr)`;
///
/// bind connection to a specific socket address
pub fn set_bind_address(&mut self, bind_address: SocketAddr) -> &mut Self {
    self.bind_address = Some(bind_address);
    self
}

Instead of the way(unrecommended):

/// callers can call `set_bind_address(addr: ToSocketAddrs)`.
/// example: set_bind_address("192.168.227.1:8086").
///
/// bind connection to a specific socket address
pub fn set_bind_address(&mut self, bind_address: ToSocketAddrs) -> std::io::Result<()> {
    self.bind_address = bind_address.to_socket_addrs()?.next();
    Ok(())
}

Usage for callers:

/// address convert errors should be handled by callers themself, 
/// not by the rumqttc library, this example just unwrap (panic) it.
use std::net::ToSocketAddrs;
let addr = "192.168.227.1:8086"
let addr: SocketAddr = addr.to_socket_addrs().unwrap();

/// use SocketAddr variable to call `set_bind_address`,
/// won't use `set_bind_address("192.168.227.1:8086")`.
network_options.set_bind_address(addr);