README.md

build

go build tcpinfo.go

run

./tcpinfo -h
./tcpinfo

feature

print tcp options, include:

• Maximum segment size
• Window scale
• Selective Acknowledgement
• others

tcpinfo.go

package main

import (
        "encoding/json"
        "flag"
        "fmt"
        "log"
        "net"

        "github.com/mikioh/tcp"
        "github.com/mikioh/tcpinfo"
)

func handleConnection(conn net.Conn, monitor bool) {
        fmt.Println("new connection:", conn.RemoteAddr())
        tc, err := tcp.NewConn(conn)
        if err != nil {
                conn.Close()
                log.Printf("tcp.NewConn failed:", err)
                return
        }

        var o tcpinfo.Info
        var b [256]byte
        for {
                i, err := tc.Option(o.Level(), o.Name(), b[:])
                if err != nil {
                        log.Println(err)
                        return
                }
                txt, err := json.Marshal(i)
                if err != nil {
                        log.Println(err)
                        return
                }
                fmt.Println(string(txt))
                if !monitor {
                        break
                }
        }
}

func main() {
        listen := flag.String("listen", ":8081", "listen adddress")
        monitor := flag.Bool("monitor", false, "monitor options")
        flag.Parse()

        ln, err := net.Listen("tcp", *listen)
        if err != nil {
                log.Printf("listen failed: %s", err)
                return
        }

        log.Println("listen:", *listen)
        for {
                conn, err := ln.Accept()
                if err != nil {
                        // handle error
                        log.Println("accept failed:", err)
                        break
                }
                go handleConnection(conn, *monitor)
        }
}

options:

{
    "ato": 0,
    "cong_ctl": {
        "snd_ssthresh": 2147483647,
        "rcv_ssthresh": 65483,
        "snd_cwnd_bytes": 0,
        "snd_cwnd_segs": 10
    },
    "flow_ctl": {
        "rcv_wnd": 65483
    },
    "last_ack_rcvd": 0,
    "last_data_rcvd": 0,
    "last_data_sent": 0,
    "opts": {
        "sack": true,
        "tmstamps": true,
        "wscale": 7
    },
    "peer_opts": {
        "sack": true,
        "tmstamps": true,
        "wscale": 7
    },
    "rcv_mss": 536,
    "rto": 200000000,
    "rtt": 14000,
    "rttvar": 7000,
    "snd_mss": 32768,
    "state": "established",
    "sys": {
        "path_mtu": 65535,
        "adv_mss": 65483,
        "ca_state": 0,
        "rexmits": 0,
        "backoffs": 0,
        "wnd_ka_probes": 0,
        "unacked_segs": 0,
        "sacked_segs": 0,
        "lost_segs": 0,
        "retrans_segs": 0,
        "fack_segs": 0,
        "reord_segs": 3,
        "rcv_rtt": 0,
        "total_retrans_segs": 0,
        "pacing_rate": 18446744073709551615,
        "thru_bytes_acked": 0,
        "thru_bytes_rcvd": 0,
        "segs_out": 0,
        "segs_in": 2,
        "not_sent_bytes": 0,
        "min_rtt": 14000,
        "data_segs_out": 0,
        "data_segs_in": 0
    }
}