Add support for setting traffic class on outgoing packets

cmd/ping/ping.go

@@ -10,11 +10,7 @@ import (
 	probing "github.com/prometheus-community/pro-bing"
 )
 
-var usage = `
-Usage:
-
-    ping [-c count] [-i interval] [-t timeout] [-I interface] [--privileged] host
-
+var examples = `
 Examples:
 
     # ping google continuously
@@ -37,6 +33,9 @@ Examples:
 
     # Send ICMP messages with a 100-byte payload
     ping -s 100 1.1.1.1
+
+    # Send ICMP messages with DSCP CS4 and ECN bits set to 0
+    ping -Q 128 8.8.8.8
 `
 
 func main() {
@@ -46,9 +45,13 @@ func main() {
 	size := flag.Int("s", 24, "")
 	ttl := flag.Int("l", 64, "TTL")
 	iface := flag.String("I", "", "interface name")
+	tclass := flag.Int("Q", 192, "Set Quality of Service related bits in ICMP datagrams (DSCP + ECN bits). Only decimal number supported")
 	privileged := flag.Bool("privileged", false, "")
 	flag.Usage = func() {
-		fmt.Print(usage)
+		out := flag.CommandLine.Output()
+		fmt.Fprintf(out, "Usage of %s:\n", os.Args[0])
+		flag.PrintDefaults()
+		fmt.Fprint(out, examples)
 	}
 	flag.Parse()
 
@@ -96,6 +99,7 @@ func main() {
 	pinger.TTL = *ttl
 	pinger.InterfaceName = *iface
 	pinger.SetPrivileged(*privileged)
+	pinger.SetTrafficClass(uint8(*tclass))
 
 	fmt.Printf("PING %s (%s):\n", pinger.Addr(), pinger.IPAddr())
 	err = pinger.Run()

packetconn.go

@@ -22,6 +22,7 @@ type packetConn interface {
 	SetDoNotFragment() error
 	SetBroadcastFlag() error
 	SetIfIndex(ifIndex int)
+	SetTrafficClass(uint8) error
 }
 
 type icmpConn struct {
@@ -58,6 +59,10 @@ func (c *icmpv4Conn) SetFlagTTL() error {
 	return err
 }
 
+func (c *icmpv4Conn) SetTrafficClass(tclass uint8) error {
+	return c.c.IPv4PacketConn().SetTOS(int(tclass))
+}
+
 func (c *icmpv4Conn) ReadFrom(b []byte) (int, int, net.Addr, error) {
 	ttl := -1
 	n, cm, src, err := c.c.IPv4PacketConn().ReadFrom(b)
@@ -99,6 +104,10 @@ func (c *icmpV6Conn) SetFlagTTL() error {
 	return err
 }
 
+func (c *icmpV6Conn) SetTrafficClass(tclass uint8) error {
+	return c.c.IPv6PacketConn().SetTrafficClass(int(tclass))
+}
+
 func (c *icmpV6Conn) ReadFrom(b []byte) (int, int, net.Addr, error) {
 	ttl := -1
 	n, cm, src, err := c.c.IPv6PacketConn().ReadFrom(b)

ping.go

@@ -116,6 +116,7 @@ func New(addr string) *Pinger {
 		protocol:          "udp",
 		awaitingSequences: firstSequence,
 		TTL:               64,
+		tclass:            192, // CS6 (network control)
 		logger:            StdLogger{Logger: log.New(log.Writer(), log.Prefix(), log.Flags())},
 	}
 }
@@ -239,6 +240,9 @@ type Pinger struct {
 	logger Logger
 
 	TTL int
+
+	// tclass defines the traffic class (ToS for IPv4) set on outgoing icmp packets
+	tclass uint8
 }
 
 type packet struct {
@@ -488,6 +492,18 @@ func (p *Pinger) SetDoNotFragment(df bool) {
 	p.df = df
 }
 
+// SetTrafficClass sets the traffic class (type-of-service field for IPv4) field
+// value for future outgoing packets.
+func (p *Pinger) SetTrafficClass(tc uint8) {
+	p.tclass = tc
+}
+
+// TrafficClass returns the traffic class field (type-of-service field for IPv4)
+// value for outgoing packets.
+func (p *Pinger) TrafficClass() uint8 {
+	return p.tclass
+}
+
 // Run runs the pinger. This is a blocking function that will exit when it's
 // done. If Count or Interval are not specified, it will run continuously until
 // it is interrupted.
@@ -527,6 +543,12 @@ func (p *Pinger) RunWithContext(ctx context.Context) error {
 		}
 	}
 
+	if p.tclass != 0 {
+		if err := conn.SetTrafficClass(p.tclass); err != nil {
+			return fmt.Errorf("error setting traffic class: %v", err)
+		}
+	}
+
 	conn.SetTTL(p.TTL)
 	if p.InterfaceName != "" {
 		iface, err := net.InterfaceByName(p.InterfaceName)

ping_test.go

@@ -242,6 +242,7 @@ func TestNewPingerValid(t *testing.T) {
 	AssertNotEqualStrings(t, "www.google.com", p.IPAddr().String())
 	AssertTrue(t, isIPv4(p.IPAddr().IP))
 	AssertFalse(t, p.Privileged())
+	AssertEquals(t, 192, p.tclass)
 	// Test that SetPrivileged works
 	p.SetPrivileged(true)
 	AssertTrue(t, p.Privileged())
@@ -253,6 +254,9 @@ func TestNewPingerValid(t *testing.T) {
 	err = p.SetAddr("ipv6.google.com")
 	AssertNoError(t, err)
 	AssertFalse(t, isIPv4(p.IPAddr().IP))
+	// Test setting traffic class
+	p.SetTrafficClass(0)
+	AssertEquals(t, 0, p.tclass)
 
 	p = New("localhost")
 	err = p.Resolve()
@@ -541,6 +545,14 @@ func AssertEqualStrings(t *testing.T, expected, actual string) {
 	}
 }
 
+func AssertEquals[T comparable](t *testing.T, expected, actual T) {
+	t.Helper()
+	if expected != actual {
+		t.Errorf("Expected %v, got %v, Stack:\n%s",
+			expected, actual, string(debug.Stack()))
+	}
+}
+
 func AssertNotEqualStrings(t *testing.T, expected, actual string) {
 	t.Helper()
 	if expected == actual {
@@ -666,6 +678,8 @@ func (c testPacketConn) SetMark(m uint) error              { return nil }
 func (c testPacketConn) SetDoNotFragment() error           { return nil }
 func (c testPacketConn) SetBroadcastFlag() error           { return nil }
 func (c testPacketConn) SetIfIndex(ifIndex int)            {}
+func (c testPacketConn) SetTrafficClass(uint8) error       { return nil }
+
 func (c testPacketConn) ReadFrom(b []byte) (n int, ttl int, src net.Addr, err error) {
 	return 0, 0, testAddr, nil
 }