IPV6 support for proxy

[max-au]

Feature request

Current behaviour

It's possible to set either environment variable HTTPS_PROXY, or HTTP_PROXY, or use global rebar configuration file to specify proxy name and port.

However there is no way to specify Internet Protocol Family (ipv6), so machines that need to connect to proxy using IPv6 cannot use rebar3.

Expected behaviour

Line 905 of src/rebar_utils.erl (also in bootstrap):

httpc:set_options([{Scheme, {{Host, Port}, []}}], rebar),

To use ipv6, it's necessary to set this for rebar httpc profile:

httpc:set_options([{ipfamily, inet6}], rebar).

[tsloughter]

Should it use a separate env var so the rebar.config doesn't have to be updated? Like HTTPS_PROXY_IPV6? And it'd use that if set.

[ferd]

The variable is kind of a standard mechanism in more than one application, so I believe we should be able to support IPv6 within existing variables. For example, the following projects all added support for it:

• Update Kubeadm proxy handling for IPv6 kubernetes/kubernetes#58399
• IPv6 literal not recognised for http_proxy env var rubygems/bundler#3725
• https_proxy / http_proxy ipv6 does not work aws/aws-cli#2994

[max-au]

That would work for IP addresses, but not actual name (and BTW I think it is already working).
(saw comment in bundler - "Fair enough. We're unlikely to support IPv6 proxies soon, then.")
I agree we should not use any more environment variables.

Root cause is inability of "escript" runner to use .inetrc file (or have {inet6, true} to be specified when starting rebar3 escript). It may be worth to explore that path, and include a fix into OTP.

Confirming - even when node has no IPv4 address (except for loopback interface with 127.0.0.1 on it), DNS client still tries to use IPv4 only, failing to resolve remote host name. I guess the issue can be closed, as it's OTP problem, not rebar.

[max-au]

Can be closed, now it works.