Added support for the NO_PROXY environment variable

[BlackDex]

Hello there,

Using the use_sys_proxy() feature does not support the NO_PROXY environment variable.
This causes Domains or IP's which should not go through the proxy to not work.

Most languages/tools support a simple comma separated list of items to skip proxy for.
This list can contain the following.

• FQDN: github.com, localhost etc.. - Only matches github.com, not gist.github.com
• FQDN Started with a dot: .github.com - matches gist.github.com, api.github.com, but not github.com
• IP Address: 127.0.0.1,::1
• CIDR: 10.0.0.0/8

Example:

NO_PROXY=localhost,127.0.0.1,::1,github.com,.github.com,10.0.0.0/8,192.168.0.5

[BlackDex]

@seanmonstar
I'm not that high level skilled in rust, but i can find my way.
I was looking at the code, and am a bit puzzled as where the best place is to put this.

I figured the best thing would be to add it to the ProxyScheme or a bit more global in the Intercept enum. But i'm a bit at a loss where to start and where/how to add it.

Because i think i need to catch it in the Proxy::intercept() call, and return None in case the Dst.host() matches the NO_PROXY value. So i probably need to have something available within that function, which can do that pattern checking.

If possible, could you point me in a bit in the right direction?
Thx in advance :).

[seanmonstar]

The behavior would likely be contained in the Intercept::System variant. The matching happens here.

I'm not too familiar with all the rules that NO_PROXY can use. It kind of looks like the rules differ in curl vs Golang.

[BlackDex]

There are some basics at least. But there are a lot of differences indeed.

Thx for the pointers, i will take a look there.

[AndrewGaspar]

I would be interested in seeing this problem fixed.

Thank you!

[jamescassell]

Curl works by splitting the "domains" in the no_proxy environment by comma (,), checking whether that matches exactly the domain, or whether the domain being considered is a "subdomain" of one of the no_proxy domains. I use quotes because you can specify a number like 1 and curl will consider 192.168.1.1 to be a "subdomain" and skip the proxy. (This is very handy for telling curl to only use the proxy for FQDN queries and bypass the proxy for IP-only queries.)

[thomastaylor312]

Opened a PR for this: #877.