2 files changed, 48 insertions, 0 deletions
diff --git a/pkg/tcpip/header/ndp_router_advert.go b/pkg/tcpip/header/ndp_router_advert.go
index 7e2f0c797..7d6efa083 100644
--- a/pkg/tcpip/header/ndp_router_advert.go
+++ b/pkg/tcpip/header/ndp_router_advert.go
@@ -16,9 +16,12 @@ package header
 
 import (
 	"encoding/binary"
+	"fmt"
 	"time"
 )
 
+var _ fmt.Stringer = NDPRoutePreference(0)
+
 // NDPRoutePreference is the preference values for default routers or
 // more-specific routes.
 //
@@ -64,6 +67,22 @@ const (
 	ReservedRoutePreference = 0b10
 )
 
+// String implements fmt.Stringer.
+func (p NDPRoutePreference) String() string {
+	switch p {
+	case HighRoutePreference:
+		return "HighRoutePreference"
+	case MediumRoutePreference:
+		return "MediumRoutePreference"
+	case LowRoutePreference:
+		return "LowRoutePreference"
+	case ReservedRoutePreference:
+		return "ReservedRoutePreference"
+	default:
+		return fmt.Sprintf("NDPRoutePreference(%d)", p)
+	}
+}
+
 // NDPRouterAdvert is an NDP Router Advertisement message. It will only contain
 // the body of an ICMPv6 packet.
 //
diff --git a/pkg/tcpip/header/ndp_test.go b/pkg/tcpip/header/ndp_test.go
index 2d55f2289..2a897e938 100644
--- a/pkg/tcpip/header/ndp_test.go
+++ b/pkg/tcpip/header/ndp_test.go
@@ -1717,3 +1717,32 @@ func TestNDPOptionsIter(t *testing.T) {
 		t.Errorf("got Next = (%x, _, _), want = (nil, _, _)", next)
 	}
 }
+
+func TestNDPRoutePreferenceStringer(t *testing.T) {
+	p := NDPRoutePreference(0)
+	for {
+		var wantStr string
+		switch p {
+		case 0b01:
+			wantStr = "HighRoutePreference"
+		case 0b00:
+			wantStr = "MediumRoutePreference"
+		case 0b11:
+			wantStr = "LowRoutePreference"
+		case 0b10:
+			wantStr = "ReservedRoutePreference"
+		default:
+			wantStr = fmt.Sprintf("NDPRoutePreference(%d)", p)
+		}
+
+		if gotStr := p.String(); gotStr != wantStr {
+			t.Errorf("got NDPRoutePreference(%d).String() = %s, want = %s", p, gotStr, wantStr)
+		}
+
+		p++
+		if p == 0 {
+			// Overflowed, we hit all values.
+			break
+		}
+	}
+}