Use time.Duration for IGMP Max Response Time field

Bug #4682

PiperOrigin-RevId: 343993297

2 files changed, 32 insertions, 8 deletions

diff --git a/pkg/tcpip/header/igmp.go b/pkg/tcpip/header/igmp.go
index e0f5d46f4..5c5be1b9d 100644
--- a/pkg/tcpip/header/igmp.go
+++ b/pkg/tcpip/header/igmp.go
@@ -17,6 +17,7 @@ package header
 import (
 	"encoding/binary"
 	"fmt"
+	"time"
 
 	"gvisor.dev/gvisor/pkg/tcpip"
 )
@@ -103,7 +104,15 @@ func (b IGMP) SetType(t IGMPType) { b[igmpTypeOffset] = byte(t) }
 // MaxRespTime gets the MaxRespTimeField. This is meaningful only in Membership
 // Query messages, in other cases it is set to 0 by the sender and ignored by
 // the receiver.
-func (b IGMP) MaxRespTime() byte { return b[igmpMaxRespTimeOffset] }
+func (b IGMP) MaxRespTime() time.Duration {
+	// As per RFC 2236 section 2.2,
+	//
+	//  The Max Response Time field is meaningful only in Membership Query
+	//  messages, and specifies the maximum allowed time before sending a
+	//  responding report in units of 1/10 second.  In all other messages, it
+	//  is set to zero by the sender and ignored by receivers.
+	return DecisecondToDuration(b[igmpMaxRespTimeOffset])
+}
 
 // SetMaxRespTime sets the MaxRespTimeField.
 func (b IGMP) SetMaxRespTime(m byte) { b[igmpMaxRespTimeOffset] = m }
@@ -164,3 +173,9 @@ func IGMPCalculateChecksum(h IGMP) uint16 {
 	h.SetChecksum(existingXsum)
 	return xsum
 }
+
+// DecisecondToDuration converts a value representing deci-seconds to a
+// time.Duration.
+func DecisecondToDuration(ds uint8) time.Duration {
+	return time.Duration(ds) * time.Second / 10
+}
diff --git a/pkg/tcpip/header/igmp_test.go b/pkg/tcpip/header/igmp_test.go
index 66e872880..b6126d29a 100644
--- a/pkg/tcpip/header/igmp_test.go
+++ b/pkg/tcpip/header/igmp_test.go
@@ -16,6 +16,7 @@ package header_test
 
 import (
 	"testing"
+	"time"
 
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
@@ -23,10 +24,11 @@ import (
 
 // TestIGMPHeader tests the functions within header.igmp
 func TestIGMPHeader(t *testing.T) {
+	const maxRespTimeTenthSec = 0xF0
 	b := []byte{
-		0x11,       // IGMP Type, Membership Query
-		0xF0,       // Maximum Response Time
-		0xC0, 0xC0, // Checksum
+		0x11,                // IGMP Type, Membership Query
+		maxRespTimeTenthSec, // Maximum Response Time
+		0xC0, 0xC0,          // Checksum
 		0x01, 0x02, 0x03, 0x04, // Group Address
 	}
 
@@ -36,8 +38,8 @@ func TestIGMPHeader(t *testing.T) {
 		t.Errorf("got igmpHeader.Type() = %x, want = %x", got, want)
 	}
 
-	if got, want := igmpHeader.MaxRespTime(), byte(0xF0); got != want {
-		t.Errorf("got igmpHeader.MaxRespTime() = %x, want = %x", got, want)
+	if got, want := igmpHeader.MaxRespTime(), header.DecisecondToDuration(maxRespTimeTenthSec); got != want {
+		t.Errorf("got igmpHeader.MaxRespTime() = %s, want = %s", got, want)
 	}
 
 	if got, want := igmpHeader.Checksum(), uint16(0xC0C0); got != want {
@@ -59,8 +61,8 @@ func TestIGMPHeader(t *testing.T) {
 
 	respTime := byte(0x02)
 	igmpHeader.SetMaxRespTime(respTime)
-	if got := igmpHeader.MaxRespTime(); got != respTime {
-		t.Errorf("got igmpHeader.MaxRespTime() = %x, want = %x", got, respTime)
+	if got, want := igmpHeader.MaxRespTime(), header.DecisecondToDuration(respTime); got != want {
+		t.Errorf("got igmpHeader.MaxRespTime() = %s, want = %s", got, want)
 	}
 
 	checksum := uint16(0x0102)
@@ -99,3 +101,10 @@ func TestIGMPChecksum(t *testing.T) {
 		t.Errorf("got IGMPCalculateChecksum = %x, want %x", got, checksum)
 	}
 }
+
+func TestDecisecondToDuration(t *testing.T) {
+	const valueInDeciseconds = 5
+	if got, want := header.DecisecondToDuration(valueInDeciseconds), valueInDeciseconds*time.Second/10; got != want {
+		t.Fatalf("got header.DecisecondToDuration(%d) = %s, want = %s", valueInDeciseconds, got, want)
+	}
+}