Golang binds the local interface IP to request the URL, and you can choose to specify the domain name resolution result IP or customize DNS resolution. 绑定接口IP(源IP)请求URL, 指定域名解析结果IP.

demo-request-bind-local-ip-hosts.go

package main

import (
	"context"
	"flag"
	"io"
	"log"
	"net"
	"net/http"
	"os"
	"time"
)

func main() {
	localIP := flag.String("localip", "", "Bind local IP")
	reqUrl := flag.String("url", "https://ipinfo.io", "URL to request")
	domainAddr := flag.String("domainaddr", "", "Specify domain name resolution IP, 34.117.59.81:443")
	flag.Parse()

	log.Printf("URL to request: %s\n", *reqUrl)
	resp, err := Request("GET", *reqUrl, nil, *localIP, *domainAddr)
	if err != nil {
		log.Fatalln(err)
	}
	_, _ = io.Copy(os.Stdout, resp.Body)
	_ = resp.Body.Close()
}

func Request(method, url string, body io.Reader, localIP, domainAddr string) (*http.Response, error) {
	client := http.Client{
		Transport: &http.Transport{
			DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
				return CustomDialContext(ctx, network, addr, localIP, domainAddr)
			},
			TLSHandshakeTimeout: 10 * time.Second,
		},
	}
	req, err := http.NewRequest(method, url, body)
	if err != nil {
		return nil, err
	}
	resp, err := client.Do(req)
	if err != nil {
		return nil, err
	}
	return resp, nil
}

func CustomDialContext(ctx context.Context, network, addr, localIP, domainAddr string) (net.Conn, error) {
	// Specify domain name resolution IP, or custom domain name resolution
	if domainAddr != "" {
		log.Printf("Specify domain name resolution IP: %s -> %s\n", addr, domainAddr)
		addr = domainAddr
	}

	var laddr *net.TCPAddr
	if localIP != "" {
		var err error
		// Automatically assign source port
		log.Printf("Bind local IP: %s\n", localIP)
		laddr, err = net.ResolveTCPAddr(network, localIP+":0")
		if err != nil {
			return nil, err
		}
	}

	dialer := &net.Dialer{
		Timeout:   10 * time.Second,
		KeepAlive: 10 * time.Second,
		LocalAddr: laddr,
	}
	return dialer.DialContext(ctx, network, addr)
}

// Demo:
//
// root@10:~/ff# ./bindipget -h
// Usage of ./bindipget:
//  -domainaddr string
//        Specify domain name resolution IP, 34.117.59.81:443
//  -localip string
//        Bind local IP
//  -url string
//        URL to request (default "https://ipinfo.io")
//
// root@10:~/ff# ./bindipget
// 2022/12/30 12:32:18 URL to request: https://ipinfo.io
// {
//  "ip": "1.2.3.4",
//  "city": "Hong Kong",
//  "region": "Central and Western",
//  "country": "HK",
//  "loc": "22.2783,114.1747",
//  "org": "AS146834 SiChuan XunYou Network Technologe Limit, co",
//  "timezone": "Asia/Hong_Kong",
//  "readme": "https://ipinfo.io/missingauth"
// }
//
// root@10:~/ff# ./bindipget -localip=172.16.1.2
// 2022/12/30 12:32:34 URL to request: https://ipinfo.io
// 2022/12/30 12:32:34 Bind local IP: 172.16.1.2
// {
//  "ip": "1.2.3.5",
//  "city": "Hong Kong",
//  "region": "Central and Western",
//  "country": "HK",
//  "loc": "22.2783,114.1747",
//  "org": "AS146834 SiChuan XunYou Network Technologe Limit, co",
//  "timezone": "Asia/Hong_Kong",
//  "readme": "https://ipinfo.io/missingauth"
// }
//
// root@10:~/ff# ./bindipget -localip=172.16.1.2 -domainaddr=34.117.59.81:443
// 2022/12/30 12:32:50 URL to request: https://ipinfo.io
// 2022/12/30 12:32:50 Specify domain name resolution IP: ipinfo.io:443 -> 34.117.59.81:443
// 2022/12/30 12:32:50 Bind local IP: 172.16.1.2
// {
//  "ip": "129.227.157.190",
//  "city": "Hong Kong",
//  "region": "Central and Western",
//  "country": "HK",
//  "loc": "22.2783,114.1747",
//  "org": "AS146834 SiChuan XunYou Network Technologe Limit, co",
//  "timezone": "Asia/Hong_Kong",
//  "readme": "https://ipinfo.io/missingauth"
// }
//
// root@10:~/ff# ./bindipget -localip=172.16.1.2 -url="http://4.ipw.cn"
// 2022/12/30 12:33:24 URL to request: http://4.ipw.cn
// 2022/12/30 12:33:24 Bind local IP: 172.16.1.2
// 1.2.3.4