add: test case for handling nil IP address

Author: lanphgphm

route_test.go

@@ -152,6 +152,61 @@ func TestRouteAddDel(t *testing.T) {
 	}
 }
 
+func TestRouteUnreachableEmptyDst(t *testing.T) {
+	t.Cleanup(setUpNetlinkTest(t))
+
+	// Test adding unreachable/blackhole/prohibit routes with empty Dst.IP
+	// These route types don't need RTA_DST to be serialized
+	testCases := []struct {
+		name      string
+		routeType int
+	}{
+		{"unreachable", unix.RTN_UNREACHABLE},
+		{"blackhole", unix.RTN_BLACKHOLE},
+		{"prohibit", unix.RTN_PROHIBIT},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			route := &Route{
+				Table: 100,
+				Dst: &net.IPNet{
+					IP:   net.IP{},
+					Mask: net.IPMask{},
+				},
+				Priority: 100,
+				Type:     tc.routeType,
+				Scope:    unix.RT_SCOPE_UNIVERSE,
+				Family:   FAMILY_V4,
+			}
+
+			if err := RouteAdd(route); err != nil {
+				t.Fatalf("failed to add %s route with empty Dst.IP: %v", tc.name, err)
+			}
+
+			routes, err := RouteListFiltered(FAMILY_V4, &Route{Table: 100}, RT_FILTER_TABLE)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			found := false
+			for _, r := range routes {
+				if r.Type == tc.routeType {
+					found = true
+					break
+				}
+			}
+			if !found {
+				t.Fatalf("%s route not found after adding", tc.name)
+			}
+
+			if err := RouteDel(route); err != nil {
+				t.Fatalf("failed to delete %s route: %v", tc.name, err)
+			}
+		})
+	}
+}
+
 func TestRoute6AddDel(t *testing.T) {
 	t.Cleanup(setUpNetlinkTest(t))