使可以指定发起连接使用的Interface以及Port

[brainiac19]

功能需求

特别是在软路由环境下，若可以指定发起连接的Interface和Port，则可在各类代理中添加规则使流量Bypass，不再有必要关闭代理再测速。对我个人的情况来讲，若可以不关闭代理进行测速，外加MOSDNS接管cf的dns重定向，意味着可以几乎无感完成优选IP更新。

预期目标

我不懂Go。问了下AI，它说可以实现。

Yes, you can modify the downloadHandler function to allow specifying the network interface name and port. Here's an updated version of the function that includes these changes:

func downloadHandler(interfaceName string, localPort int) float64 {
	interfaces, err := net.Interfaces()
	if err != nil {
		// handle error
	}

	var localAddr net.IP
	for _, iface := range interfaces {
		if iface.Name == interfaceName {
			addrs, err := iface.Addrs()
			if err != nil {
				// handle error
			}
			for _, addr := range addrs {
				ip, _, err := net.ParseCIDR(addr.String())
				if err != nil {
					// handle error
				}
				if ip.To4() != nil {
					localAddr = ip
					break
				}
			}
		}
	}

	if localAddr == nil {
		// handle error, interface not found or no IPv4 address
	}

	transport := &http.Transport{
		DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
			localTCPAddr := &net.TCPAddr{
				IP:   localAddr,
				Port: localPort,
			}
			dialer := &net.Dialer{
				LocalAddr: localTCPAddr,
			}
			return dialer.DialContext(ctx, network, addr)
		},
		Timeout:   Timeout,
		Proxy:     http.ProxyFromEnvironment,
		// ... other transport configuration options
	}

	client := &http.Client{
		Transport: transport,
		Timeout:   Timeout,
		// ... other client configuration options
	}

	// ... rest of the function code
}

In the updated code, the downloadHandler function takes an additional interfaceName argument, which represents the name of the network interface you want to use. It then searches for the specified network interface and retrieves its IPv4 address.The DialContext function is modified to create a custom net.Dialer with a specific local address (localTCPAddr) that contains the desired local IP and port. This custom Dialer is then used to establish the network connection.To use this updated function, pass the network interface name and local port as arguments when calling the function, for example:

interfaceName := "eth0"
localPort := 12345
result := downloadHandler(interfaceName, localPort)
Make sure to replace interfaceName with the appropriate network interface name, adjust the other parts of the code as needed, and handle any error conditions.