TUN inbound: Refine gateway and autoSystemRoutingTable on macOS

[yiguodev]

Summary

• allow Darwin TUN to use the first IPv4 prefix from gateway for the utun point-to-point address
• keep 169.254.10.1/30 as the default fallback when gateway is not configured
• use the selected gateway when adding/removing IPv4 system routes
• document macOS gateway, autoSystemRoutingTable, and dns behavior
• add Darwin unit tests for gateway selection

Validation

• git diff --check
• go test ./proxy/tun -count=1
• go test ./infra/conf ./infra/conf/serial ./proxy/tun -count=1

AI Coding by GPT-5.5 Extra High

[yiguodev]

1. 优化 macOS 的 gateway 支持。
2. 实测 IPv4 路由正常。
3. 实测 link-local IPv6 足够使用。
4. 如果 stable release 在等 macOS 的裸核 tun 支持的话，可以考虑发一个 stable version 了。

[Copilot]

Pull request overview

This pull request updates the Darwin (macOS) TUN implementation to derive the utun point-to-point IPv4 addressing and IPv4 system-route gateway from the configured gateway list (first IPv4 prefix), with a safe default fallback (169.254.10.1/30). It also documents the macOS behavior and adds unit tests for gateway selection.

Changes:

• Add selectDarwinGateway logic to choose the first IPv4 gateway prefix (or fall back to defaultDarwinGateway) and validate that a usable local IPv4 address exists.
• Use the selected gateway both for utun point-to-point configuration (setIPAddress) and as the IPv4 gateway when adding/removing system routes.
• Update TUN documentation for macOS behavior and add darwin-only unit tests for gateway selection.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
proxy/tun/tun_darwin.go	Selects/validates a macOS gateway prefix, configures utun addressing from it, and uses it for IPv4 system route gateway.
proxy/tun/tun_darwin_test.go	Adds darwin-only unit tests covering default selection, IPv4 selection, IPv6 skipping, and validation failures.
proxy/tun/README.md	Documents macOS gateway, autoSystemRoutingTable, and dns behavior (including defaults and IPv6 notes).

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[Jasper344612]

如果 stable release 在等 macOS 的裸核 tun 支持的话，可以考虑发一个 stable version 了。

应该不是

[RPRX]

2dust/v2rayN#9649 (comment)

[RPRX]

@yiguodev 三大系统的 TUN 就差 macOS 还没实现进程匹配了，你研究一下，希望下一个 PR 是这个，确实能发 stable 了

[autorepobot]

2dust/v2rayN#9715

[iambabyninja]

@yiguodev
Good afternoon! Based on information received from the clients developers:
Commit 987290b (merged July 8, PR #6434 — "Routing: process supports macOS as well") added calls to proc_pidinfo / proc_pidfdinfo / proc_pidpath from /usr/lib/libproc.dylib. These are public on macOS but private on iOS. Since the app ships as "Designed for iPad," Apple's scanner picks them up and flags it during review.

Rejection reason: Guideline 2.5.1 (Performance — Software Requirements) — unapproved use of public APIs, specifically citing NEVPNManager, on the grounds that API behavior may change unpredictably.

[RPRX]

@iambabyninja 是这个 PR #6447 ，@yiguodev 话说 Go 有没有 !ios 这种东西？或者有没有 !gomobile 之类的

[yiguodev]

修改中，一会发 PR 。

[yiguodev]

@iambabyninja fixed in #6524