dial.go

package main

import (
	"net"
	"fmt"
	"time"
	"context"
)

func Dialer(ctx context.Context, network, address string) (conn net.Conn, err error) {
	var d net.Dialer
	fmt.Println(ctx, network, address)
	conn, err = d.DialContext(ctx, network, address)
	fmt.Println("Dial!", err)
	//return conn, err
	if err != nil {
		fmt.Println("dial err: " + err.Error())
		return conn, err
	}
	return &ConnProxy{ target: conn }, nil
}

type ConnProxy struct {
	target net.Conn
}

func (p *ConnProxy) Read(b []byte) (n int, err error) {
	n, err = p.target.Read(b)
	fmt.Println("read: ", b, n, err)
	return
}

func (p *ConnProxy) Write(b []byte) (n int, err error) {
	n, err = p.target.Write(b)
	fmt.Println("write: ", b, n, err)
	return
}

func (p *ConnProxy) Close() error {
	return p.target.Close()
}

func (p *ConnProxy) LocalAddr() net.Addr {
	return p.target.LocalAddr()
}

func (p *ConnProxy) RemoteAddr() net.Addr {
	return p.target.RemoteAddr()
}

func (p *ConnProxy) SetDeadline(t time.Time) error {
	return p.target.SetDeadline(t)
}

func (p *ConnProxy) SetReadDeadline(t time.Time) error {
	return p.target.SetReadDeadline(t)
}

func (p *ConnProxy) SetWriteDeadline(t time.Time) error {
	return p.target.SetWriteDeadline(t)
}

func init() {
	net.DefaultResolver = &net.Resolver{
		PreferGo: true,
		Dial: Dialer,
	}
}

func main() {
	/*
	net.DefaultResolver = &net.Resolver{
		PreferGo: true,
		Dial: Dialer,
	}*/
	//init()
	names, err := net.LookupHost("www.baidu.com")
	fmt.Printf("%+v, %v\n", names, err)
}