Socks proxy support for net/http

[technoweenie]

This patches in SOCKS proxy support for the net/http adapter, using this snippet by @yarafan: #787 (comment).

I don't want to add the socksify gem as a required gem dependency for faraday. The net/http adapter attempts to load it, but only complains if you try to use a socks proxy:

$ irb -Ilib
>> require 'faraday'
=> true
>> Faraday.new(proxy: 'socks://127.0.0.1:6000').get('http://example.com').status
=> RuntimeError (SOCKS proxy support requires the socksify gem ~> 1.7.1)

$ gem install socksify
$ irb -Ilib
>> require 'faraday'
=> true
>> Faraday.new(proxy: 'socks://127.0.0.1:6000').get('http://example.com').status
Faraday::ConnectionFailed (Failed to open TCP connection to 127.0.0.1:6000 (Connection refused - connect(2) for "127.0.0.1" port 6000))

This behavior is difficult to test with rspec, so I tested this in the integration test suite faraday-live.

Fixes #787

[technoweenie]

While the original patch passed my integration tests (technoweenie/faraday-live#7), I didn't like how the username and password were set:

      TCPSocket.socks_username = proxy[:user] if proxy[:user]
      TCPSocket.socks_password = proxy[:password] if proxy[:password]
      Net::HTTP::SOCKSProxy(proxy[:uri].host, proxy[:uri].port)

A global (or at-best, a thread local) socks username/pass doesn't seem very safe. I rewrote this to use the socksify maintainer's PR to support proxy authentication: astro/socksify-ruby#33

[iMacTia]

Nice implementation and great opportunity to also rewrite some old code in a much better way.
Ignoring Code Climate issues for the reasons explained in the comment above.

[iMacTia]

For future visitors, this change is technically good to go but is waiting for astro/socksify-ruby#33 to be merged.

[vizv]

This takes forever 😅

[iMacTia]

Cross-dependencies with other libraries 🙈.
We have been chasing on astro/socksify-ruby#33, but to no avail 😞

[reinieravila]

Cross-dependencies with other libraries 🙈. We have been chasing on astro/socksify-ruby#33, but to no avail 😞

Finally the linked PR got merged