[MichaelSuen-thePointer]

Summary

Add --plugin-mode and the corresponding plugin_mode configuration option, supporting tcp_only (default), udp_only, and tcp_and_udp.

The plugin handles only the selected protocols. For example, with mode=tcp_and_udp and plugin_mode=udp_only, UDP traffic passes through the plugin while TCP traffic connects directly. The plugin mode must be a subset of the relay mode.

Changes

• Apply protocol-specific routing in ss-local, ss-tunnel, and ss-redir.
• Bind plugin-handled protocols to an internal listener in ss-server, while retaining the public listener for other protocols.
• Support plugin mode configuration in ss-manager.
• Check both TCP and UDP port availability when the plugin handles UDP.
• Update CLI documentation and add regression coverage for mode parsing and all nine relay/plugin mode combinations.

The default remains TCP-only plugin handling, preserving existing SIP003 behavior.

Validation

Passed:

• CLI documentation consistency checks and all 10 documentation regression tests.
• No-heap lint, including its self-test.
• git diff --check.
• Compilation, CTest, and the added C++ regression tests.

Not yet run:

• Stress tests and independent shadowsocks-rust interoperability tests.
• End-to-end SIP003u plugin tests for TCP, UDP, and mixed-protocol routing.

[MichaelSuen-thePointer]

close to re-organize commits