Source file src/pkg/net/ipraw_test.go

// Copyright 2009 The Go Authors.  All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.


// TODO(cw): ListenPacket test, Read() test, ipv6 test &
// Dial()/Listen() level tests

package net

import (
    "bytes"
    "flag"
    "os"
    "testing"
)

const ICMP_ECHO_REQUEST = 8
const ICMP_ECHO_REPLY = 0

// returns a suitable 'ping request' packet, with id & seq and a
// payload length of pktlen
func makePingRequest(id, seq, pktlen int, filler []byte) []byte {
    p := make([]byte, pktlen)
    copy(p[8:], bytes.Repeat(filler, (pktlen-8)/len(filler)+1))

    p[0] = ICMP_ECHO_REQUEST // type
    p[1] = 0                 // code
    p[2] = 0                 // cksum
    p[3] = 0                 // cksum
    p[4] = uint8(id >> 8)    // id
    p[5] = uint8(id & 0xff)  // id
    p[6] = uint8(seq >> 8)   // sequence
    p[7] = uint8(seq & 0xff) // sequence

    // calculate icmp checksum
    cklen := len(p)
    s := uint32(0)
    for i := 0; i < (cklen - 1); i += 2 {
        s += uint32(p[i+1])<<8 | uint32(p[i])
    }
    if cklen&1 == 1 {
        s += uint32(p[cklen-1])
    }
    s = (s >> 16) + (s & 0xffff)
    s = s + (s >> 16)

    // place checksum back in header; using ^= avoids the
    // assumption the checksum bytes are zero
    p[2] ^= uint8(^s & 0xff)
    p[3] ^= uint8(^s >> 8)

    return p
}

func parsePingReply(p []byte) (id, seq int) {
    id = int(p[4])<<8 | int(p[5])
    seq = int(p[6])<<8 | int(p[7])
    return
}

var srchost = flag.String("srchost", "", "Source of the ICMP ECHO request")
var dsthost = flag.String("dsthost", "localhost", "Destination for the ICMP ECHO request")

// test (raw) IP socket using ICMP
func TestICMP(t *testing.T) {
    if os.Getuid() != 0 {
        t.Logf("test disabled; must be root")
        return
    }

    var laddr *IPAddr
    if *srchost != "" {
        laddr, err := ResolveIPAddr(*srchost)
        if err != nil {
            t.Fatalf(`net.ResolveIPAddr("%v") = %v, %v`, *srchost, laddr, err)
        }
    }

    raddr, err := ResolveIPAddr(*dsthost)
    if err != nil {
        t.Fatalf(`net.ResolveIPAddr("%v") = %v, %v`, *dsthost, raddr, err)
    }

    c, err := ListenIP("ip4:icmp", laddr)
    if err != nil {
        t.Fatalf(`net.ListenIP("ip4:icmp", %v) = %v, %v`, *srchost, c, err)
    }

    sendid := os.Getpid() & 0xffff
    const sendseq = 61455
    const pingpktlen = 128
    sendpkt := makePingRequest(sendid, sendseq, pingpktlen, []byte("Go Go Gadget Ping!!!"))

    n, err := c.WriteToIP(sendpkt, raddr)
    if err != nil || n != pingpktlen {
        t.Fatalf(`net.WriteToIP(..., %v) = %v, %v`, raddr, n, err)
    }

    c.SetTimeout(100e6)
    resp := make([]byte, 1024)
    for {
        n, from, err := c.ReadFrom(resp)
        if err != nil {
            t.Fatalf(`ReadFrom(...) = %v, %v, %v`, n, from, err)
        }
        if resp[0] != ICMP_ECHO_REPLY {
            continue
        }
        rcvid, rcvseq := parsePingReply(resp)
        if rcvid != sendid || rcvseq != sendseq {
            t.Fatalf(`Ping reply saw id,seq=0x%x,0x%x (expected 0x%x, 0x%x)`, rcvid, rcvseq, sendid, sendseq)
        }
        return
    }
    t.Fatalf("saw no ping return")
}