golang 实现ss/netstat

今天遇到一个问题。使用netstat命令查看, 发现tcp某链接长时间处于CLOST_WAIT状态。所以想看看netstat是如些实现的。直接下载netstat源码看实现。netstat主要是读/proc/net/下的文件。而当时host是/proc文件已经阻塞。ls命令都会被阻塞。因此这才是导致TCP链接状态长期不更新的原因。

正在学golang于是go实现类似ss, netstat命令的功能。直接上代码

package main


import (
    "fmt"
    "os"
    "bufio"
    "io"
    "strings"
    "strconv"
)

func load_data() []string {

    var str []string

    tcpFile := "/proc/net/tcp"

    fin, err := os.Open(tcpFile)

    defer fin.Close()

    if err != nil {
        fmt.Println(tcpFile, err)
        return str
    }

    r := bufio.NewReader(fin)

    for {
        buf, err := r.ReadString('\n')
        if err == io.EOF { break }
        str = append(str, buf)
    }

    if len(str) > 0 {
        return str[1:]
    }
    return str
}

func hex2dec(hexstr string) string{
    i, _ := strconv.ParseInt(hexstr, 16, 0)
    return strconv.FormatInt(i, 10)
}

func hex_to_ip(hexstr string) (string, string) {
    var ip string
    if len(hexstr) != 8 {
        err := "parse error"
        return ip, err
    }

    i1, _ := strconv.ParseInt(hexstr[6:8], 16, 0)
    i2, _ := strconv.ParseInt(hexstr[4:6], 16, 0)
    i3, _ := strconv.ParseInt(hexstr[2:4], 16, 0)
    i4, _ := strconv.ParseInt(hexstr[0:2], 16, 0)
    ip = fmt.Sprintf("%d.%d.%d.%d", i1, i2, i3, i4)

    return ip, ""
}

func convert_to_ip_port(str string) (string, string) {
    l := strings.Split(str, ":")
    if len(l) != 2 {
        return str, ""
    }

    ip, err := hex_to_ip(l[0])
    if err != "" {
        return str, ""
    }

    return ip, hex2dec(l[1])
}

func remove_all_space(l [] string) [] string {
    var ll []string
    for _, v := range l {
        if v != "" {
            ll = append(ll, v)
        }
    }

    return ll
}

var STATE = map[string]string{
                "01":"ESTABLISHED",
                "02":"SYN_SENT",
                "03":"SYN_RECV",
                "04":"FIN_WAIT1",
                "05":"FIN_WAIT2",
                "06":"TIME_WAIT",
                "07":"CLOSE",
                "08":"CLOSE_WAIT",
                "09":"LAST_ACK",
                "0A":"LISTEN",
                "0B":"CLOSING",
                }


func main() {
    fmt.Println("ss demo use golang");

    lines := load_data()

    fmt.Printf("State\tLocal Address:Port\t\t\tPeer Address:Port\n")
    for _, line := range lines {
        //fmt.Println(line)
        l := remove_all_space(strings.Split(line, " "))
        l_host, l_port := convert_to_ip_port(l[1])
        r_host, r_port := convert_to_ip_port(l[2])
        stats := STATE[l[3]]
        fmt.Printf("%s\t\t%s:%s\t\t\t%s:%s\n", stats, l_host, l_port, r_host, r_port)
    }
}