Adding forwarder headers so end server can resolve caller

[hansr]

No description provided.

[gemini-code-assist]

Summary of Changes

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This pull request enhances the proxy listener's functionality by ensuring that the original client's IP address is correctly propagated to the end server. It achieves this by injecting standard HTTP forwarding headers into the connection, allowing backend services to accurately resolve the true caller behind the proxy.

Highlights

• Forwarding Headers Injection: Introduced logic to inject standard forwarding headers (X-Forwarded-For, X-Real-IP, and Forwarded) into the connection to ensure backend services can identify the original client's IP address.
• Connection Wrapping: Wrapped the established connection with a new newForwardedHeaderConn to encapsulate the header injection mechanism.
• Consistent Client Address Usage: Ensured that the client's remote address is consistently used when establishing the connection to the device via connectDeviceFrom.

Changelog

• rpc/proxy_listener.go
  • Introduced logic to inject X-Forwarded-For, X-Real-IP, and Forwarded headers into the connection.
  • Modified the connectDeviceFrom function call to consistently use the client's remote address.

Activity

• No human activity has been recorded on this pull request yet.

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[gemini-code-assist]

Code Review

This pull request aims to add forwarding headers to preserve the original client IP address. While the intent is valid, the implementation exposes a pre-existing critical race condition by modifying a loop variable captured in a goroutine. This issue must be addressed to prevent incorrect behavior such as connection mix-ups.

[gemini-code-assist]

This line, by re-assigning the conn variable, exacerbates a critical race condition. The conn and tlsConn variables are captured from the parent for loop. When the loop iterates, these variables are updated, but previously launched goroutines will see the new values, causing them to operate on the wrong connection. This will lead to unpredictable behavior and connection mix-ups.

To fix this, you must pass the connection as a parameter to the goroutine to ensure each goroutine has its own local copy.

For example, the goroutine invocation around line 53 should be changed to:

go func(conn net.Conn) {
    tlsConn, ok := conn.(*tls.Conn)
    if !ok {
        // This was already checked, but for safety.
        return
    }
    // ... rest of the goroutine logic using local conn and tlsConn
}(conn)

Inside the goroutine, you should then use this local conn parameter. It would also be clearer to assign the result of newForwardedHeaderConn to a new variable, e.g., forwardedConn.

Suggested change

	conn = newForwardedHeaderConn(conn, clientAddr)
	go func(conn net.Conn) {
	tlsConn, ok := conn.(*tls.Conn)
	if !ok {
	// This was already checked, but for safety.
	return
	}
	// ... rest of the goroutine logic using local conn and tlsConn
	}(conn)

[dominicletz]

@hansr did you miss committing a file?