Specifying the source address of an outgoing connection using IO::Socket::*

[p6rt]

Migrated from rt.perl.org#131766 (status was 'new')

Searchable as RT131766$

[p6rt]

From @AlexDaniel

It should be possible to specify the source address of outgoing (client) connections. This is especially useful if the machine has more than one IP address.

Examples in other software​:
* wget supports --bind-address parameter​: https://www.gnu.org/software/wget/manual/wget.html#Download-Options
* Python accepts optional “source_address” parameter​: https://docs.python.org/2/library/socket.html#socket.create_connection
* “bind before connect”, a blog post that seems to be relevant​: https://idea.popcount.org/2014-04-03-bind-before-connect/
* curl seems to allow it too, but surprisingly it can also accept the interface name​: https://curl.haxx.se/docs/manpage.html#--interface

It is possible to find more examples of languages that support it, but I'm sold already.

My best guess is that it is doable by simply calling uv_tcp_bind for outgoing connections.

Relevant links​:
* https://github.com/MoarVM/MoarVM/blob/2a79727deb78105c8c9f660a1136a3db1179b09b/src/io/asyncsocket.c#L532-L533
* https://github.com/MoarVM/MoarVM/blob/2a79727deb78105c8c9f660a1136a3db1179b09b/src/io/asyncsocket.c#L681-L683

[AlexDaniel]

There were a series of pull requests to resolve this, but unfortunately it's a little bit stuck.

• Add a source_address parameter to the connect instruction. MoarVM/MoarVM#659
• Add a source-address parameter to IO::Socket::INet.pm rakudo/rakudo#1137

@Kaiepi, any thoughts?

[Kaiepi]

Bind before connect is something I'm working towards making possible with MoarVM/MoarVM#1231 / Raku/nqp#597 / rakudo/rakudo#3451. With those it'd be possible to call a bind method (which I don't think I actually have written yet) before calling connect to do this, but it'd be useful to be able to deal with this from the connect method alone as well.

I'm OK with adding source host and port parameters to IO::Socket::INET.connect, but the way the PR handles this by adding more behaviour to nqp::connect conflicts somewhat with how I was approaching this.

[AlexDaniel]

OK, I see. Mind if I assign you here?