CIDR support for proxy bypass list

Feature or enhancement

Proposal:

I propose adding universal support for CIDR-notation IP addresses when reading NO_PROXY / the OS-specific equivalents.

Currently, support for NO_PROXY is a bit inconsistent, both across the ecosystem and within Python. On MacOS using SystemConfiguration, CIDR is supported out of the box, as is the short notation 10.0. The default implementation and the windows nt ProxyOverride registry key do not. Go and curl and wget all support CIDR notation, so despite not being standardized, there is precedent towards this.

In some environments, all outbound traffic is required to go through a proxy. However, traffic to internal services is allowed to be direct (for performance, or inherent trust, or any other reason). An example NO_PROXY may look like NO_PROXY=localhost,.localhost,127.0.0.1,127.0.0.2,0.0.0.0,169.254.169.254,10.0.0.0/8,.internal.,.internal,.local.,.local.

Has this already been discussed elsewhere?

I have already discussed this feature proposal on Discourse

Links to previous discussion of this feature:

https://discuss.python.org/t/support-cidr-notation-in-no-proxy/66292 - discussion was tepid but leant towards yes if a good PR was proposed. I'm working on that in tandem with this gh ticket.

Windows specifically: https://github.com/python/cpython/issues/149136

More generally: https://about.gitlab.com/blog/we-need-to-talk-no-proxy/

Linked PRs

• gh-149744
• gh-156336

先查看 gh-149744 和 gh-156336 中的相關工作，接著閱讀相關的 Discourse 討論以及 Windows issue gh-149136。要求的結果是對 NO_PROXY 和作業系統特定等效項一致地處理 CIDR 表示法，包括列出的內部網路範例。