Add ability to set TTL (#186)

cmd/ping/ping.go

@@ -41,6 +41,7 @@ func main() {
 	interval := flag.Duration("i", time.Second, "")
 	count := flag.Int("c", -1, "")
 	size := flag.Int("s", 24, "")
+	ttl := flag.Int("l", 64, "TTL")
 	privileged := flag.Bool("privileged", false, "")
 	flag.Usage = func() {
 		fmt.Print(usage)
@@ -88,6 +89,7 @@ func main() {
 	pinger.Size = *size
 	pinger.Interval = *interval
 	pinger.Timeout = *timeout
+	pinger.TTL = *ttl
 	pinger.SetPrivileged(*privileged)
 
 	fmt.Printf("PING %s (%s):\n", pinger.Addr(), pinger.IPAddr())

packetconn.go

@@ -17,21 +17,38 @@ type packetConn interface {
 	SetFlagTTL() error
 	SetReadDeadline(t time.Time) error
 	WriteTo(b []byte, dst net.Addr) (int, error)
+	SetTTL(ttl int)
 }
 
 type icmpConn struct {
-	c *icmp.PacketConn
+	c   *icmp.PacketConn
+	ttl int
 }
 
 func (c *icmpConn) Close() error {
 	return c.c.Close()
 }
 
+func (c *icmpConn) SetTTL(ttl int) {
+	c.ttl = ttl
+}
+
 func (c *icmpConn) SetReadDeadline(t time.Time) error {
 	return c.c.SetReadDeadline(t)
 }
 
 func (c *icmpConn) WriteTo(b []byte, dst net.Addr) (int, error) {
+	if c.c.IPv6PacketConn() != nil {
+		if err := c.c.IPv6PacketConn().SetHopLimit(c.ttl); err != nil {
+			return 0, err
+		}
+	}
+	if c.c.IPv4PacketConn() != nil {
+		if err := c.c.IPv4PacketConn().SetTTL(c.ttl); err != nil {
+			return 0, err
+		}
+	}
+
 	return c.c.WriteTo(b, dst)
 }
 

ping.go

@@ -106,6 +106,7 @@ func New(addr string) *Pinger {
 		network:           "ip",
 		protocol:          "udp",
 		awaitingSequences: firstSequence,
+		TTL:               64,
 		logger:            StdLogger{Logger: log.New(log.Writer(), log.Prefix(), log.Flags())},
 	}
 }
@@ -202,6 +203,8 @@ type Pinger struct {
 	protocol string
 
 	logger Logger
+
+	TTL int
 }
 
 type packet struct {
@@ -402,6 +405,7 @@ func (p *Pinger) Run() error {
 	}
 	defer conn.Close()
 
+	conn.SetTTL(p.TTL)
 	return p.run(conn)
 }
 

ping_test.go

@@ -641,6 +641,7 @@ func (c testPacketConn) Close() error                      { return nil }
 func (c testPacketConn) ICMPRequestType() icmp.Type        { return ipv4.ICMPTypeEcho }
 func (c testPacketConn) SetFlagTTL() error                 { return nil }
 func (c testPacketConn) SetReadDeadline(t time.Time) error { return nil }
+func (c testPacketConn) SetTTL(t int)                      {}
 
 func (c testPacketConn) ReadFrom(b []byte) (n int, ttl int, src net.Addr, err error) {
 	return 0, 0, nil, nil