Support binding to a specific local address for http_response

[zoonage]

Feature Request

Opening a feature request kicks off a discussion.

Proposal:

Add a bind interface/IP address to the http_response plugin to force the request to egress via a specific interface

[[inputs.http_response]]
  address = "http://google.com"
  bind = "eth0"

Current behavior:

The request uses the default net.Dialer which selects an interface for the request.

Desired behavior:

To be able to specify an interface or IP address as the address to bind the http.Client to.

Use case:

For hosts that have VPN tunnels for a specific interface's traffic it is useful to check that you can send a request via this interface

[danielnelson]

Sounds good, I think we should name the option interface since bind is something the server usually does. It seems like this is implemented with the LocalAddr field on the dialer? I guess we would use the first address assigned to the interface?

Is this something you could put together a pull request for?

[zoonage]

@danielnelson I'm unsure due to work commitments, but I'll give it a go