Merge pull request #907 from devlights/add-tcp-reuseaddr-onoff-example

Author: devlights

examples/socket/tcp_reuseaddr/Taskfile.yml

@@ -0,0 +1,12 @@
+# https://taskfile.dev
+
+version: '3'
+
+tasks:
+  default:
+    cmds:
+      - task: run
+  run:
+    cmds:
+      - go run . -listenconfig
+      - go run .

examples/socket/tcp_reuseaddr/main.go

@@ -0,0 +1,131 @@
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"log"
+	"net"
+	"syscall"
+)
+
+type (
+	Args struct {
+		UseListenConfig bool
+	}
+)
+
+const (
+	SO_REUSEADDR = syscall.SO_REUSEADDR
+	SO_REUSEPORT = 0xf
+)
+
+var (
+	args Args
+)
+
+func main() {
+	log.SetFlags(log.Lmicroseconds)
+
+	flag.BoolVar(&args.UseListenConfig, "listenconfig", false, "Use net.ListenConfig")
+	flag.Parse()
+
+	if err := run(); err != nil {
+		panic(err)
+	}
+}
+
+func run() error {
+	var err error
+	switch args.UseListenConfig {
+	case true:
+		err = runListenConfig()
+	default:
+		err = runNormal()
+	}
+
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func runListenConfig() error {
+	lc := net.ListenConfig{
+		Control: func(network, address string, c syscall.RawConn) error {
+			var (
+				reuseAddr, reusePort int
+				opErr1, opErr2       error
+				err                  error
+			)
+
+			err = c.Control(func(fd uintptr) {
+				reuseAddr, opErr1 = syscall.GetsockoptInt(int(fd), syscall.SOL_SOCKET, SO_REUSEADDR)
+				reusePort, opErr2 = syscall.GetsockoptInt(int(fd), syscall.SOL_SOCKET, SO_REUSEPORT)
+			})
+
+			if err != nil {
+				return err
+			}
+
+			log.Printf("SO_REUSEADDR=%d", reuseAddr)
+			log.Printf("SO_REUSEPORT=%d", reusePort)
+
+			if opErr1 != nil {
+				return opErr1
+			}
+
+			if opErr2 != nil {
+				return opErr2
+			}
+
+			return nil
+		},
+	}
+
+	ln, err := lc.Listen(context.Background(), "tcp", ":8888")
+	if err != nil {
+		return err
+	}
+	defer ln.Close()
+
+	return nil
+}
+
+func runNormal() error {
+	ln, err := net.Listen("tcp", ":8888")
+	if err != nil {
+		return err
+	}
+	defer ln.Close()
+
+	tcpLn, ok := ln.(*net.TCPListener)
+	if !ok {
+		return fmt.Errorf("not a TCP Listener")
+	}
+
+	file, err := tcpLn.File()
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+
+	var (
+		fd = file.Fd()
+		v  int
+	)
+	v, err = syscall.GetsockoptInt(int(fd), syscall.SOL_SOCKET, SO_REUSEADDR)
+	if err != nil {
+		return err
+	}
+	log.Printf("SO_REUSEADDR=%d", v)
+
+	v, err = syscall.GetsockoptInt(int(fd), syscall.SOL_SOCKET, SO_REUSEPORT)
+	if err != nil {
+		return err
+	}
+	log.Printf("SO_REUSEPORT=%d", v)
+
+	return nil
+}