unsafe1_setopt.go

package main

import (
	"net"
	"unsafe"
	"syscall"
)

type fdMutex struct {
	state uint64
	rsema uint32
	wsema uint32
}

type pollDesc struct {
	runtimeCtx uintptr
}

type netFD struct {
	// locking/lifetime of sysfd + serialize access to Read and Write methods
	fdmu fdMutex

	// immutable until Close
	sysfd       int
	family      int
	sotype      int
	isConnected bool
	net         string
	laddr       net.Addr // 加上包
	raddr       net.Addr // 加上包

	// wait server
	pd pollDesc
}

func main() {
	conn, err := net.Dial("tcp", "www.taobao.com:80")
	if err != nil {
		panic(err)
	}

	if tcpConn, ok := conn.(*net.TCPConn); ok {
		fd := *(**netFD)(unsafe.Pointer(tcpConn))
		println("fd: ", fd.sysfd)

		const tcpUserTimeout = 0x12
		syscall.SetsockoptInt(fd.sysfd, syscall.IPPROTO_TCP, tcpUserTimeout, 1000)
	}
}