feat: Add option to define which DNS server a DNS monitor queries (#2389)

internal/hub/network_monitors.go

@@ -17,6 +17,10 @@ func generateMonitorID(systemId string, config monitor.Config) string {
 	if config.Protocol == "tcp" {
 		args = append(args, strconv.FormatUint(uint64(config.Port), 10))
 	}
+	// only use server for DNS monitors, so the same target queried via different servers gets distinct monitors
+	if config.Protocol == "dns" {
+		args = append(args, config.Server)
+	}
 	return systems.MakeStableHashId(args...)
 }
 
@@ -53,10 +57,15 @@ func bindNetworkMonitorsEvents(hub *Hub) {
 	// record with the new ID and delete the old one. Otherwise, just update the existing monitor on the agent.
 	hub.OnRecordUpdateRequest("network_monitors").BindFunc(func(e *core.RecordRequestEvent) error {
 		systemID := e.Record.GetString("system")
+		protocol := e.Record.GetString("protocol")
 		// only tcp uses port - set other protocols port to zero
-		if e.Record.GetString("protocol") != "tcp" {
+		if protocol != "tcp" {
 			e.Record.Set("port", 0)
 		}
+		// only dns uses server - clear it for other protocols
+		if protocol != "dns" {
+			e.Record.Set("server", "")
+		}
 		ID := generateMonitorID(systemID, *monitorConfigFromRecord(e.Record))
 		if ID != e.Record.Id {
 			newRecord := copyMonitorToNewRecord(e.Record, ID)
@@ -103,6 +112,7 @@ func monitorConfigFromRecord(record *core.Record) *monitor.Config {
 		Protocol: record.GetString("protocol"),
 		Port:     uint16(record.GetInt("port")),
 		Interval: uint16(record.GetInt("interval")),
+		Server:   record.GetString("server"),
 	}
 }
 
@@ -127,7 +137,7 @@ func copyMonitorToNewRecord(oldRecord *core.Record, newID string) *core.Record {
 	collection := oldRecord.Collection()
 	newRecord := core.NewRecord(collection)
 	newRecord.Id = newID
-	fields := []string{"system", "target", "protocol", "port", "interval", "enabled"}
+	fields := []string{"system", "target", "protocol", "port", "server", "interval", "enabled"}
 	for _, field := range fields {
 		newRecord.Set(field, oldRecord.Get(field))
 	}

internal/hub/network_monitors_test.go

@@ -174,6 +174,39 @@ func TestGenerateMonitorID(t *testing.T) {
 			},
 			expected: "84167969",
 		},
+		{
+			name:     "DNS monitor on example.com with server 1.1.1.1",
+			systemID: "sys999",
+			config: monitor.Config{
+				Protocol: "dns",
+				Target:   "example.com",
+				Server:   "1.1.1.1",
+				Interval: 30,
+			},
+			expected: "2175898b",
+		},
+		{
+			name:     "DNS monitor on example.com with different server",
+			systemID: "sys999",
+			config: monitor.Config{
+				Protocol: "dns",
+				Target:   "example.com",
+				Server:   "8.8.8.8",
+				Interval: 30,
+			},
+			expected: "ebcd8b33",
+		},
+		{
+			name:     "DNS monitor on example.com with no server (system resolver)",
+			systemID: "sys999",
+			config: monitor.Config{
+				Protocol: "dns",
+				Target:   "example.com",
+				Server:   "",
+				Interval: 30,
+			},
+			expected: "19476a7",
+		},
 	}
 
 	for _, tt := range tests {
@@ -199,6 +232,7 @@ func TestCopyMonitorToNewRecordDropsResultFields(t *testing.T) {
 		"target":   "https://example.com",
 		"protocol": "http",
 		"port":     443,
+		"server":   "1.1.1.1",
 		"interval": 60,
 		"enabled":  true,
 		"res":      1200,
@@ -216,6 +250,7 @@ func TestCopyMonitorToNewRecordDropsResultFields(t *testing.T) {
 	assert.Equal(t, "https://example.com", newRecord.GetString("target"))
 	assert.Equal(t, "http", newRecord.GetString("protocol"))
 	assert.Equal(t, 443, newRecord.GetInt("port"))
+	assert.Equal(t, "1.1.1.1", newRecord.GetString("server"))
 	assert.True(t, newRecord.GetBool("enabled"))
 	assert.Contains(t, []string{"", "null"}, newRecord.GetString("certInfo"))
 	assert.Zero(t, newRecord.GetFloat("res"))