Summary

• Add comp-lzo config option for OpenVPN proxy to support LZO compression
• Fix data packets not being routed through OpenVPN servers with comp-lzo enabled

Problem

When connecting to OpenVPN servers with comp-lzo enabled, the handshake succeeds but data transfer fails. The server expects all data packets to include a 1-byte LZO compression header, but mihomo was sending raw IP packets without it.

Root Cause

1. Sending: No LZO header prepended to outgoing packets → server drops them
2. Receiving: Cannot decompress LZO-compressed packets from server → responses lost

Changes

• transport/openvpn/config.go: Add CompLZO field to ClientConfig struct
• transport/openvpn/lzo.go: New file - pure Go LZO1X decompression using github.com/rasky/go-lzo
• transport/openvpn/data.go: Add LZO header (0xfa) to outgoing packets when comp-lzo is enabled; decompress incoming LZO-compressed packets (0x66)
• transport/openvpn/keymethod.go: Add IV_LZO=1 to peer info and comp-lzo to options string when enabled
• transport/openvpn/client.go: Use new comp-lzo aware functions
• transport/openvpn/push.go: Parse route and route-ipv6 from server push reply
• adapter/outbound/openvpn.go: Add comp-lzo config option, convert string to bool

Config Example

proxies:
  - name: my-openvpn
    type: openvpn
    server: vpn.example.com
    port: 1194
    proto: tcp
    username: user
    password: pass
    comp-lzo: "yes"  # "yes", "no", or "adaptive"
    ca: |
      -----BEGIN CERTIFICATE-----
      ...
      -----END CERTIFICATE-----

Testing

Verified against a real OpenVPN server with comp-lzo enabled:

• Handshake: ✅ succeeds
• Health check: ✅ alive, 73-284ms
• HTTP request through tunnel: ✅ returns valid response

Dependencies

Pure Go, no CGO required. Uses github.com/rasky/go-lzo for LZO decompression.