feat(correlation): add include_dest_ports filter + README/arch update (v1.1.12)

- feat: new config directive include_dest_ports ([]int) in correlation section
- feat: if non-empty, only events with a matching dst_port are correlated
- feat: filtered events are silently ignored (not correlated, not emitted as orphan)
- feat: new metric failed_dest_port_filtered tracked in ProcessEvent
- feat: DEBUG log 'event excluded by dest port filter: source=A dst_port=22'
- test: TestCorrelationService_IncludeDestPorts_AllowedPort
- test: TestCorrelationService_IncludeDestPorts_FilteredPort
- test: TestCorrelationService_IncludeDestPorts_EmptyAllowsAll
- docs(readme): full rewrite to match current code (v1.1.12)
- docs(readme): add include_dest_ports section, fix version refs, clean outdated sections
- docs(arch): add dest_port_filtering section, failed_dest_port_filtered metric, debug log example
- fix(config.example): remove obsolete stdout.level field
- chore: bump version to 1.1.12

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

internal/domain/correlation_service.go

@@ -42,8 +42,9 @@ type CorrelationConfig struct {
 	MaxHTTPBufferSize int    // Maximum events to buffer for source A (HTTP)
 	MaxNetworkBufferSize int // Maximum events to buffer for source B (Network)
 	NetworkTTLS       int    // TTL in seconds for network events (source B)
-	MatchingMode      string // "one_to_one" or "one_to_many" (Keep-Alive)
+	MatchingMode      string   // "one_to_one" or "one_to_many" (Keep-Alive)
 	ExcludeSourceIPs  []string // List of source IPs or CIDR ranges to exclude
+	IncludeDestPorts  []int    // If non-empty, only correlate events matching these destination ports
 }
 
 // pendingOrphan represents an A event waiting to be emitted as orphan.
@@ -181,6 +182,20 @@ func (s *CorrelationService) isIPExcluded(ip string) bool {
 	return false
 }
 
+// isDestPortFiltered returns true if the event's destination port is NOT in the
+// include list. When IncludeDestPorts is empty, all ports are allowed.
+func (s *CorrelationService) isDestPortFiltered(port int) bool {
+	if len(s.config.IncludeDestPorts) == 0 {
+		return false // no filter configured: allow all
+	}
+	for _, p := range s.config.IncludeDestPorts {
+		if p == port {
+			return false // port is in the allow-list
+		}
+	}
+	return true // port not in allow-list: filter out
+}
+
 // ProcessEvent processes an incoming event and returns correlated logs if matches are found.
 func (s *CorrelationService) ProcessEvent(event *NormalizedEvent) []CorrelatedLog {
 	s.mu.Lock()
@@ -194,6 +209,14 @@ func (s *CorrelationService) ProcessEvent(event *NormalizedEvent) []CorrelatedLo
 		return nil
 	}
 
+	// Check if destination port is in the allow-list
+	if s.isDestPortFiltered(event.DstPort) {
+		s.logger.Debugf("event excluded by dest port filter: source=%s dst_port=%d",
+			event.Source, event.DstPort)
+		s.metrics.RecordCorrelationFailed("dest_port_filtered")
+		return nil
+	}
+
 	// Record event received
 	s.metrics.RecordEventReceived(string(event.Source))
 

internal/domain/correlation_service_test.go

@@ -1317,3 +1317,100 @@ func TestCorrelationService_ApacheEmitDelay_Flush(t *testing.T) {
 	}
 }
 
+
+func TestCorrelationService_IncludeDestPorts_AllowedPort(t *testing.T) {
+now := time.Now()
+mt := &mockTimeProvider{now: now}
+svc := NewCorrelationService(CorrelationConfig{
+TimeWindow:       10 * time.Second,
+ApacheAlwaysEmit: true,
+MatchingMode:     MatchingModeOneToMany,
+IncludeDestPorts: []int{80, 443},
+}, mt)
+
+// B event on allowed port 443
+bEvent := &NormalizedEvent{
+Source: SourceB, Timestamp: now,
+SrcIP: "1.2.3.4", SrcPort: 1234, DstPort: 443,
+}
+results := svc.ProcessEvent(bEvent)
+if len(results) != 0 {
+t.Fatalf("expected B buffered (no match yet), got %d results", len(results))
+}
+
+// A event on same key, allowed port
+aEvent := &NormalizedEvent{
+Source: SourceA, Timestamp: now,
+SrcIP: "1.2.3.4", SrcPort: 1234, DstPort: 443,
+}
+results = svc.ProcessEvent(aEvent)
+if len(results) != 1 {
+t.Fatalf("expected 1 correlation, got %d", len(results))
+}
+if !results[0].Correlated {
+t.Error("expected correlated=true")
+}
+}
+
+func TestCorrelationService_IncludeDestPorts_FilteredPort(t *testing.T) {
+now := time.Now()
+mt := &mockTimeProvider{now: now}
+svc := NewCorrelationService(CorrelationConfig{
+TimeWindow:       10 * time.Second,
+ApacheAlwaysEmit: true,
+MatchingMode:     MatchingModeOneToMany,
+IncludeDestPorts: []int{80, 443},
+}, mt)
+
+// A event on port 22 (not in allow-list)
+aEvent := &NormalizedEvent{
+Source: SourceA, Timestamp: now,
+SrcIP: "1.2.3.4", SrcPort: 1234, DstPort: 22,
+}
+results := svc.ProcessEvent(aEvent)
+if len(results) != 0 {
+t.Fatalf("expected 0 results (filtered), got %d", len(results))
+}
+
+// B event on port 22 (not in allow-list)
+bEvent := &NormalizedEvent{
+Source: SourceB, Timestamp: now,
+SrcIP: "1.2.3.4", SrcPort: 1234, DstPort: 22,
+}
+results = svc.ProcessEvent(bEvent)
+if len(results) != 0 {
+t.Fatalf("expected 0 results (filtered), got %d", len(results))
+}
+
+// Flush should also return nothing
+flushed := svc.Flush()
+if len(flushed) != 0 {
+t.Errorf("expected 0 flushed events, got %d", len(flushed))
+}
+}
+
+func TestCorrelationService_IncludeDestPorts_EmptyAllowsAll(t *testing.T) {
+now := time.Now()
+mt := &mockTimeProvider{now: now}
+// No IncludeDestPorts = all ports allowed
+svc := NewCorrelationService(CorrelationConfig{
+TimeWindow:       10 * time.Second,
+ApacheAlwaysEmit: true,
+MatchingMode:     MatchingModeOneToMany,
+}, mt)
+
+bEvent := &NormalizedEvent{
+Source: SourceB, Timestamp: now,
+SrcIP: "1.2.3.4", SrcPort: 1234, DstPort: 9999,
+}
+svc.ProcessEvent(bEvent)
+
+aEvent := &NormalizedEvent{
+Source: SourceA, Timestamp: now,
+SrcIP: "1.2.3.4", SrcPort: 1234, DstPort: 9999,
+}
+results := svc.ProcessEvent(aEvent)
+if len(results) != 1 || !results[0].Correlated {
+t.Errorf("expected 1 correlation on any port when list is empty, got %d", len(results))
+}
+}