Allow binding to another (non-default) interface

[tahajahangir]

[rofl0r]

SO_BINDTODEVICE seems to be a linux-specific API. what prevents you from using the ip address of the specified interface with the existing -b option?

[tahajahangir]

The existing -b option only works when the specified IP is on the same interface as the default route interface. When machine have multiple interfaces and the bind-ip is not on the default interface, this options solves the problem.

[soffchen]

Nice feature, but works only under linux.

[mimi89999]

what prevents you from using the ip address of the specified interface with the existing -b option?

It would be nice to listen on a different interface that the outgoing connections.

[mimi89999]

The problem is that if the IP address set by the -b option is on the default route, the default route will be used and not the specified interface.

[zopieux]

I've patched this PR against master and it works and does exactly what I needed. Would you consider accepting it, please?

[rofl0r]

i can't merge this PR as-is, because it would break build on solaris, *BSD, and OSX

[zopieux]

It is a matter of surrounding the Linux-specific code with #if[def] fences?

[rofl0r]

i dont want to litter the code with ugly ifdefs, they need to be in a single spot, if at all