/
ping.go
108 lines (88 loc) · 2.26 KB
/
ping.go
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package helpers
import (
"bytes"
"net"
"os"
"time"
)
const (
ICMP_ECHO_REQUEST = 8
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
}
/*
func elapsedTime(start int64) float32 {
t := float32(time.Nanoseconds() - start) / 1000000.0
return t
}*/
func IcmpPing(addr string, timeout time.Duration) (time.Duration, error) {
raddr, err := net.ResolveIPAddr("ip4", addr) // *IPAddr
if err != nil {
return 0, err
}
ipconn, err := net.ListenIP("ip4:icmp", nil) // *IPConn (Conn 인터페이스 구현)
if err != nil {
return 0, err
}
sendid := os.Getpid() & 0xffff
sendseq := 1
pingpktlen := 64
sendpkt := makePingRequest(sendid, sendseq, pingpktlen, []byte("Go Ping"))
start := time.Now()
n, err := ipconn.WriteToIP(sendpkt, raddr)
if err != nil || n != pingpktlen {
return 0, err
}
ipconn.SetReadDeadline(start.Add(timeout)) // 0.5 second
resp := make([]byte, 1024)
for {
_, _, err := ipconn.ReadFrom(resp)
//fmt.Printf("%d bytes from %s: icmp_req=%d time=%.2f ms\n", n, dst, sendseq, elapsedTime(start))
if err != nil {
return 0, err
}
if resp[0] != ICMP_ECHO_REPLY {
continue
}
rcvid, rcvseq := parsePingReply(resp)
if rcvid != sendid || rcvseq != sendseq {
return 0, err
}
break
}
return time.Now().Sub(start), nil
}