Motivation / Problem

For STUN I need a method that a connect() can be bound to a local address (to reuse a local address, as that is what STUN does). I was looking for a clean way to implement this.

I see two methods of doing this:

1. add a connect_bind_address variable to NetworkAddress, and pass this from Resolve() into func so it can read this address again. This is a lot of poking holes, and adds a variable specific for one flow (out of the three that exist).
2. use a lambda with a capture to bypass all this and only send the NetworkAddress to ConnectLoopProc directly.

In this PR I present the second option, mostly as my C++ knowledge is not sufficient to know if there are any downsides to this approach.

Description

This is currently not used, but later commits will make use of
this.

It uses a capture lambda to inject some extra parameters to the callback function, without anything in between knowing about it.

Limitations

• During testing this works, but I have no clue how many compilers accept this (should be C++17?)
• My C++ knowledge is limited, so I pieced this together from what LordAro told me last week, but please, look at this carefully :)

Checklist for review

Some things are not automated, and forgotten often. This list is a reminder for the reviewers.

• The bug fix is important enough to be backported? (label: 'backport requested')
• This PR affects the save game format? (label 'savegame upgrade')
• This PR affects the GS/AI API? (label 'needs review: Script API')
  • ai_changelog.hpp, gs_changelog.hpp need updating.
  • The compatibility wrappers (compat_*.nut) need updating.
• This PR affects the NewGRF API? (label 'needs review: NewGRF')
  • newgrf_debug_data.h may need updating.
  • PR must be added to API tracker