[management, proxy] Add CrowdSec IP reputation integration for reverse proxy (#5722)

proxy/internal/accesslog/logger.go

@@ -2,6 +2,7 @@ package accesslog
 
 import (
 	"context"
+	"maps"
 	"net/netip"
 	"sync"
 	"sync/atomic"
@@ -126,6 +127,7 @@ type logEntry struct {
 	BytesUpload   int64
 	BytesDownload int64
 	Protocol      Protocol
+	Metadata      map[string]string
 }
 
 // Protocol identifies the transport protocol of an access log entry.
@@ -150,8 +152,10 @@ type L4Entry struct {
 	BytesDownload int64
 	// DenyReason, when non-empty, indicates the connection was denied.
 	// Values match the HTTP auth mechanism strings: "ip_restricted",
-	// "country_restricted", "geo_unavailable".
+	// "country_restricted", "geo_unavailable", "crowdsec_ban", etc.
 	DenyReason string
+	// Metadata carries extra context about the connection (e.g. CrowdSec verdict).
+	Metadata map[string]string
 }
 
 // LogL4 sends an access log entry for a layer-4 connection (TCP or UDP).
@@ -167,6 +171,7 @@ func (l *Logger) LogL4(entry L4Entry) {
 		DurationMs:    entry.DurationMs,
 		BytesUpload:   entry.BytesUpload,
 		BytesDownload: entry.BytesDownload,
+		Metadata:      maps.Clone(entry.Metadata),
 	}
 	if entry.DenyReason != "" {
 		if !l.allowDenyLog(entry.ServiceID, entry.DenyReason) {
@@ -258,6 +263,7 @@ func (l *Logger) log(entry logEntry) {
 				BytesUpload:   entry.BytesUpload,
 				BytesDownload: entry.BytesDownload,
 				Protocol:      string(entry.Protocol),
+				Metadata:      entry.Metadata,
 			},
 		}); err != nil {
 			l.logger.WithFields(log.Fields{

proxy/internal/accesslog/middleware.go

@@ -82,6 +82,7 @@ func (l *Logger) Middleware(next http.Handler) http.Handler {
 			BytesUpload:   bytesUpload,
 			BytesDownload: bytesDownload,
 			Protocol:      ProtocolHTTP,
+			Metadata:      capturedData.GetMetadata(),
 		}
 		l.logger.Debugf("response: request_id=%s method=%s host=%s path=%s status=%d duration=%dms source=%s origin=%s service=%s account=%s",
 			requestID, r.Method, host, r.URL.Path, sw.status, duration.Milliseconds(), sourceIp, capturedData.GetOrigin(), capturedData.GetServiceID(), capturedData.GetAccountID())

proxy/internal/auth/middleware.go

@@ -167,6 +167,20 @@ func (mw *Middleware) checkIPRestrictions(w http.ResponseWriter, r *http.Request
 		return true
 	}
 
+	if verdict.IsCrowdSec() {
+		if cd := proxy.CapturedDataFromContext(r.Context()); cd != nil {
+			cd.SetMetadata("crowdsec_verdict", verdict.String())
+			if config.IPRestrictions.IsObserveOnly(verdict) {
+				cd.SetMetadata("crowdsec_mode", "observe")
+			}
+		}
+	}
+
+	if config.IPRestrictions.IsObserveOnly(verdict) {
+		mw.logger.Debugf("CrowdSec observe: would block %s for %s (%s)", clientIP, r.Host, verdict)
+		return true
+	}
+
 	reason := verdict.String()
 	mw.blockIPRestriction(r, reason)
 	http.Error(w, "Forbidden", http.StatusForbidden)

proxy/internal/auth/middleware_test.go

@@ -669,7 +669,7 @@ func TestCheckIPRestrictions_UnparseableAddress(t *testing.T) {
 	mw := NewMiddleware(log.StandardLogger(), nil, nil)
 
 	err := mw.AddDomain("example.com", nil, "", 0, "acc1", "svc1",
-		restrict.ParseFilter([]string{"10.0.0.0/8"}, nil, nil, nil))
+		restrict.ParseFilter(restrict.FilterConfig{AllowedCIDRs: []string{"10.0.0.0/8"}}))
 	require.NoError(t, err)
 
 	handler := mw.Protect(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
@@ -705,7 +705,7 @@ func TestCheckIPRestrictions_UsesCapturedDataClientIP(t *testing.T) {
 	mw := NewMiddleware(log.StandardLogger(), nil, nil)
 
 	err := mw.AddDomain("example.com", nil, "", 0, "acc1", "svc1",
-		restrict.ParseFilter([]string{"203.0.113.0/24"}, nil, nil, nil))
+		restrict.ParseFilter(restrict.FilterConfig{AllowedCIDRs: []string{"203.0.113.0/24"}}))
 	require.NoError(t, err)
 
 	handler := mw.Protect(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
@@ -746,7 +746,7 @@ func TestCheckIPRestrictions_NilGeoWithCountryRules(t *testing.T) {
 	mw := NewMiddleware(log.StandardLogger(), nil, nil)
 
 	err := mw.AddDomain("example.com", nil, "", 0, "acc1", "svc1",
-		restrict.ParseFilter(nil, nil, []string{"US"}, nil))
+		restrict.ParseFilter(restrict.FilterConfig{AllowedCountries: []string{"US"}}))
 	require.NoError(t, err)
 
 	handler := mw.Protect(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {

proxy/internal/crowdsec/bouncer.go

@@ -0,0 +1,251 @@
+// Package crowdsec provides a CrowdSec stream bouncer that maintains a local
+// decision cache for IP reputation checks.
+package crowdsec
+
+import (
+	"context"
+	"errors"
+	"net/netip"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/crowdsecurity/crowdsec/pkg/models"
+	csbouncer "github.com/crowdsecurity/go-cs-bouncer"
+	log "github.com/sirupsen/logrus"
+
+	"github.com/netbirdio/netbird/proxy/internal/restrict"
+)
+
+// Bouncer wraps a CrowdSec StreamBouncer, maintaining a local cache of
+// active decisions for fast IP lookups. It implements restrict.CrowdSecChecker.
+type Bouncer struct {
+	mu       sync.RWMutex
+	ips      map[netip.Addr]*restrict.CrowdSecDecision
+	prefixes map[netip.Prefix]*restrict.CrowdSecDecision
+	ready    atomic.Bool
+
+	apiURL         string
+	apiKey         string
+	tickerInterval time.Duration
+	logger         *log.Entry
+
+	// lifeMu protects cancel and done from concurrent Start/Stop calls.
+	lifeMu sync.Mutex
+	cancel context.CancelFunc
+	done   chan struct{}
+}
+
+// compile-time check
+var _ restrict.CrowdSecChecker = (*Bouncer)(nil)
+
+// NewBouncer creates a bouncer but does not start the stream.
+func NewBouncer(apiURL, apiKey string, logger *log.Entry) *Bouncer {
+	return &Bouncer{
+		apiURL:   apiURL,
+		apiKey:   apiKey,
+		logger:   logger,
+		ips:      make(map[netip.Addr]*restrict.CrowdSecDecision),
+		prefixes: make(map[netip.Prefix]*restrict.CrowdSecDecision),
+	}
+}
+
+// Start launches the background goroutine that streams decisions from the
+// CrowdSec LAPI. The stream runs until Stop is called or ctx is cancelled.
+func (b *Bouncer) Start(ctx context.Context) error {
+	interval := b.tickerInterval
+	if interval == 0 {
+		interval = 10 * time.Second
+	}
+	stream := &csbouncer.StreamBouncer{
+		APIKey:              b.apiKey,
+		APIUrl:              b.apiURL,
+		TickerInterval:      interval.String(),
+		UserAgent:           "netbird-proxy/1.0",
+		Scopes:              []string{"ip", "range"},
+		RetryInitialConnect: true,
+	}
+
+	b.logger.Infof("connecting to CrowdSec LAPI at %s", b.apiURL)
+
+	if err := stream.Init(); err != nil {
+		return err
+	}
+
+	// Reset state from any previous run.
+	b.mu.Lock()
+	b.ips = make(map[netip.Addr]*restrict.CrowdSecDecision)
+	b.prefixes = make(map[netip.Prefix]*restrict.CrowdSecDecision)
+	b.mu.Unlock()
+	b.ready.Store(false)
+
+	ctx, cancel := context.WithCancel(ctx)
+	done := make(chan struct{})
+
+	b.lifeMu.Lock()
+	if b.cancel != nil {
+		b.lifeMu.Unlock()
+		cancel()
+		return errors.New("bouncer already started")
+	}
+	b.cancel = cancel
+	b.done = done
+	b.lifeMu.Unlock()
+
+	var wg sync.WaitGroup
+	wg.Add(2)
+
+	go func() {
+		defer wg.Done()
+		if err := stream.Run(ctx); err != nil && ctx.Err() == nil {
+			b.logger.Errorf("CrowdSec stream ended: %v", err)
+		}
+	}()
+
+	go func() {
+		defer wg.Done()
+		b.consumeStream(ctx, stream)
+	}()
+
+	go func() {
+		wg.Wait()
+		close(done)
+	}()
+
+	return nil
+}
+
+// Stop cancels the stream and waits for all goroutines to finish.
+func (b *Bouncer) Stop() {
+	b.lifeMu.Lock()
+	cancel := b.cancel
+	done := b.done
+	b.cancel = nil
+	b.lifeMu.Unlock()
+
+	if cancel != nil {
+		cancel()
+		<-done
+	}
+}
+
+// Ready returns true after the first batch of decisions has been processed.
+func (b *Bouncer) Ready() bool {
+	return b.ready.Load()
+}
+
+// CheckIP looks up addr in the local decision cache. Returns nil if no
+// active decision exists for the address.
+//
+// Prefix lookups are O(1): instead of scanning all stored prefixes, we
+// probe the map for every possible containing prefix of the address
+// (at most 33 for IPv4, 129 for IPv6).
+func (b *Bouncer) CheckIP(addr netip.Addr) *restrict.CrowdSecDecision {
+	addr = addr.Unmap()
+
+	b.mu.RLock()
+	defer b.mu.RUnlock()
+
+	if d, ok := b.ips[addr]; ok {
+		return d
+	}
+
+	maxBits := 32
+	if addr.Is6() {
+		maxBits = 128
+	}
+	// Walk from most-specific to least-specific prefix so the narrowest
+	// matching decision wins when ranges overlap.
+	for bits := maxBits; bits >= 0; bits-- {
+		prefix := netip.PrefixFrom(addr, bits).Masked()
+		if d, ok := b.prefixes[prefix]; ok {
+			return d
+		}
+	}
+
+	return nil
+}
+
+func (b *Bouncer) consumeStream(ctx context.Context, stream *csbouncer.StreamBouncer) {
+	first := true
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case resp, ok := <-stream.Stream:
+			if !ok {
+				return
+			}
+			b.mu.Lock()
+			b.applyDeleted(resp.Deleted)
+			b.applyNew(resp.New)
+			b.mu.Unlock()
+
+			if first {
+				b.ready.Store(true)
+				b.logger.Info("CrowdSec bouncer synced initial decisions")
+				first = false
+			}
+		}
+	}
+}
+
+func (b *Bouncer) applyDeleted(decisions []*models.Decision) {
+	for _, d := range decisions {
+		if d.Value == nil || d.Scope == nil {
+			continue
+		}
+		value := *d.Value
+
+		if strings.ToLower(*d.Scope) == "range" || strings.Contains(value, "/") {
+			prefix, err := netip.ParsePrefix(value)
+			if err != nil {
+				b.logger.Debugf("skip unparsable CrowdSec range deletion %q: %v", value, err)
+				continue
+			}
+			prefix = normalizePrefix(prefix)
+			delete(b.prefixes, prefix)
+		} else {
+			addr, err := netip.ParseAddr(value)
+			if err != nil {
+				b.logger.Debugf("skip unparsable CrowdSec IP deletion %q: %v", value, err)
+				continue
+			}
+			delete(b.ips, addr.Unmap())
+		}
+	}
+}
+
+func (b *Bouncer) applyNew(decisions []*models.Decision) {
+	for _, d := range decisions {
+		if d.Value == nil || d.Type == nil || d.Scope == nil {
+			continue
+		}
+		dec := &restrict.CrowdSecDecision{Type: restrict.DecisionType(*d.Type)}
+		value := *d.Value
+
+		if strings.ToLower(*d.Scope) == "range" || strings.Contains(value, "/") {
+			prefix, err := netip.ParsePrefix(value)
+			if err != nil {
+				b.logger.Debugf("skip unparsable CrowdSec range %q: %v", value, err)
+				continue
+			}
+			prefix = normalizePrefix(prefix)
+			b.prefixes[prefix] = dec
+		} else {
+			addr, err := netip.ParseAddr(value)
+			if err != nil {
+				b.logger.Debugf("skip unparsable CrowdSec IP %q: %v", value, err)
+				continue
+			}
+			b.ips[addr.Unmap()] = dec
+		}
+	}
+}
+
+// normalizePrefix unmaps v4-mapped-v6 addresses and zeros host bits so
+// the prefix is a valid map key that matches CheckIP's probe logic.
+func normalizePrefix(p netip.Prefix) netip.Prefix {
+	return netip.PrefixFrom(p.Addr().Unmap(), p.Bits()).Masked()
+}

proxy/internal/crowdsec/bouncer_test.go

@@ -0,0 +1,337 @@
+package crowdsec
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"net/netip"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/crowdsecurity/crowdsec/pkg/models"
+	log "github.com/sirupsen/logrus"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/netbirdio/netbird/proxy/internal/restrict"
+)
+
+func TestBouncer_CheckIP_Empty(t *testing.T) {
+	b := newTestBouncer()
+	b.ready.Store(true)
+
+	assert.Nil(t, b.CheckIP(netip.MustParseAddr("1.2.3.4")))
+}
+
+func TestBouncer_CheckIP_ExactMatch(t *testing.T) {
+	b := newTestBouncer()
+	b.ready.Store(true)
+	b.ips[netip.MustParseAddr("10.0.0.1")] = &restrict.CrowdSecDecision{Type: restrict.DecisionBan}
+
+	d := b.CheckIP(netip.MustParseAddr("10.0.0.1"))
+	require.NotNil(t, d)
+	assert.Equal(t, restrict.DecisionBan, d.Type)
+
+	assert.Nil(t, b.CheckIP(netip.MustParseAddr("10.0.0.2")))
+}
+
+func TestBouncer_CheckIP_PrefixMatch(t *testing.T) {
+	b := newTestBouncer()
+	b.ready.Store(true)
+	b.prefixes[netip.MustParsePrefix("192.168.1.0/24")] = &restrict.CrowdSecDecision{Type: restrict.DecisionBan}
+
+	d := b.CheckIP(netip.MustParseAddr("192.168.1.100"))
+	require.NotNil(t, d)
+	assert.Equal(t, restrict.DecisionBan, d.Type)
+
+	assert.Nil(t, b.CheckIP(netip.MustParseAddr("192.168.2.1")))
+}
+
+func TestBouncer_CheckIP_UnmapsV4InV6(t *testing.T) {
+	b := newTestBouncer()
+	b.ready.Store(true)
+	b.ips[netip.MustParseAddr("10.0.0.1")] = &restrict.CrowdSecDecision{Type: restrict.DecisionBan}
+
+	d := b.CheckIP(netip.MustParseAddr("::ffff:10.0.0.1"))
+	require.NotNil(t, d)
+	assert.Equal(t, restrict.DecisionBan, d.Type)
+}
+
+func TestBouncer_Ready(t *testing.T) {
+	b := newTestBouncer()
+	assert.False(t, b.Ready())
+
+	b.ready.Store(true)
+	assert.True(t, b.Ready())
+}
+
+func TestBouncer_CheckIP_ExactBeforePrefix(t *testing.T) {
+	b := newTestBouncer()
+	b.ready.Store(true)
+	b.ips[netip.MustParseAddr("10.0.0.1")] = &restrict.CrowdSecDecision{Type: restrict.DecisionCaptcha}
+	b.prefixes[netip.MustParsePrefix("10.0.0.0/8")] = &restrict.CrowdSecDecision{Type: restrict.DecisionBan}
+
+	d := b.CheckIP(netip.MustParseAddr("10.0.0.1"))
+	require.NotNil(t, d)
+	assert.Equal(t, restrict.DecisionCaptcha, d.Type)
+
+	d2 := b.CheckIP(netip.MustParseAddr("10.0.0.2"))
+	require.NotNil(t, d2)
+	assert.Equal(t, restrict.DecisionBan, d2.Type)
+}
+
+func TestBouncer_ApplyNew_IP(t *testing.T) {
+	b := newTestBouncer()
+
+	b.applyNew(makeDecisions(
+		decision{scope: "ip", value: "1.2.3.4", dtype: "ban", scenario: "test/brute"},
+		decision{scope: "ip", value: "5.6.7.8", dtype: "captcha", scenario: "test/crawl"},
+	))
+
+	require.Len(t, b.ips, 2)
+	assert.Equal(t, restrict.DecisionBan, b.ips[netip.MustParseAddr("1.2.3.4")].Type)
+	assert.Equal(t, restrict.DecisionCaptcha, b.ips[netip.MustParseAddr("5.6.7.8")].Type)
+}
+
+func TestBouncer_ApplyNew_Range(t *testing.T) {
+	b := newTestBouncer()
+
+	b.applyNew(makeDecisions(
+		decision{scope: "range", value: "10.0.0.0/8", dtype: "ban"},
+	))
+
+	require.Len(t, b.prefixes, 1)
+	assert.NotNil(t, b.prefixes[netip.MustParsePrefix("10.0.0.0/8")])
+}
+
+func TestBouncer_ApplyDeleted_IP(t *testing.T) {
+	b := newTestBouncer()
+	b.ips[netip.MustParseAddr("1.2.3.4")] = &restrict.CrowdSecDecision{Type: restrict.DecisionBan}
+	b.ips[netip.MustParseAddr("5.6.7.8")] = &restrict.CrowdSecDecision{Type: restrict.DecisionBan}
+
+	b.applyDeleted(makeDecisions(
+		decision{scope: "ip", value: "1.2.3.4", dtype: "ban"},
+	))
+
+	assert.Len(t, b.ips, 1)
+	assert.Nil(t, b.ips[netip.MustParseAddr("1.2.3.4")])
+	assert.NotNil(t, b.ips[netip.MustParseAddr("5.6.7.8")])
+}
+
+func TestBouncer_ApplyDeleted_Range(t *testing.T) {
+	b := newTestBouncer()
+	b.prefixes[netip.MustParsePrefix("10.0.0.0/8")] = &restrict.CrowdSecDecision{Type: restrict.DecisionBan}
+	b.prefixes[netip.MustParsePrefix("192.168.0.0/16")] = &restrict.CrowdSecDecision{Type: restrict.DecisionBan}
+
+	b.applyDeleted(makeDecisions(
+		decision{scope: "range", value: "10.0.0.0/8", dtype: "ban"},
+	))
+
+	require.Len(t, b.prefixes, 1)
+	assert.NotNil(t, b.prefixes[netip.MustParsePrefix("192.168.0.0/16")])
+}
+
+func TestBouncer_ApplyNew_OverwritesExisting(t *testing.T) {
+	b := newTestBouncer()
+	b.ips[netip.MustParseAddr("1.2.3.4")] = &restrict.CrowdSecDecision{Type: restrict.DecisionBan}
+
+	b.applyNew(makeDecisions(
+		decision{scope: "ip", value: "1.2.3.4", dtype: "captcha"},
+	))
+
+	assert.Equal(t, restrict.DecisionCaptcha, b.ips[netip.MustParseAddr("1.2.3.4")].Type)
+}
+
+func TestBouncer_ApplyNew_SkipsInvalid(t *testing.T) {
+	b := newTestBouncer()
+
+	b.applyNew(makeDecisions(
+		decision{scope: "ip", value: "not-an-ip", dtype: "ban"},
+		decision{scope: "range", value: "also-not-valid", dtype: "ban"},
+	))
+
+	assert.Empty(t, b.ips)
+	assert.Empty(t, b.prefixes)
+}
+
+// TestBouncer_StreamIntegration tests the full flow: fake LAPI → StreamBouncer → Bouncer cache → CheckIP.
+func TestBouncer_StreamIntegration(t *testing.T) {
+	lapi := newFakeLAPI()
+	ts := httptest.NewServer(lapi)
+	defer ts.Close()
+
+	// Seed the LAPI with initial decisions.
+	lapi.setDecisions(
+		decision{scope: "ip", value: "1.2.3.4", dtype: "ban", scenario: "crowdsecurity/ssh-bf"},
+		decision{scope: "range", value: "10.0.0.0/8", dtype: "ban", scenario: "crowdsecurity/http-probing"},
+		decision{scope: "ip", value: "5.5.5.5", dtype: "captcha", scenario: "crowdsecurity/http-crawl"},
+	)
+
+	b := NewBouncer(ts.URL, "test-key", log.NewEntry(log.StandardLogger()))
+	b.tickerInterval = 200 * time.Millisecond
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	require.NoError(t, b.Start(ctx))
+	defer b.Stop()
+
+	// Wait for initial sync.
+	require.Eventually(t, b.Ready, 5*time.Second, 50*time.Millisecond, "bouncer should become ready")
+
+	// Verify decisions are cached.
+	d := b.CheckIP(netip.MustParseAddr("1.2.3.4"))
+	require.NotNil(t, d, "1.2.3.4 should be banned")
+	assert.Equal(t, restrict.DecisionBan, d.Type)
+
+	d2 := b.CheckIP(netip.MustParseAddr("10.1.2.3"))
+	require.NotNil(t, d2, "10.1.2.3 should match range ban")
+	assert.Equal(t, restrict.DecisionBan, d2.Type)
+
+	d3 := b.CheckIP(netip.MustParseAddr("5.5.5.5"))
+	require.NotNil(t, d3, "5.5.5.5 should have captcha")
+	assert.Equal(t, restrict.DecisionCaptcha, d3.Type)
+
+	assert.Nil(t, b.CheckIP(netip.MustParseAddr("9.9.9.9")), "unknown IP should be nil")
+
+	// Simulate a delta update: delete one IP, add a new one.
+	lapi.setDelta(
+		[]decision{{scope: "ip", value: "1.2.3.4", dtype: "ban"}},
+		[]decision{{scope: "ip", value: "2.3.4.5", dtype: "throttle", scenario: "crowdsecurity/http-flood"}},
+	)
+
+	// Wait for the delta to be picked up.
+	require.Eventually(t, func() bool {
+		return b.CheckIP(netip.MustParseAddr("2.3.4.5")) != nil
+	}, 5*time.Second, 50*time.Millisecond, "new decision should appear")
+
+	assert.Nil(t, b.CheckIP(netip.MustParseAddr("1.2.3.4")), "deleted decision should be gone")
+
+	d4 := b.CheckIP(netip.MustParseAddr("2.3.4.5"))
+	require.NotNil(t, d4)
+	assert.Equal(t, restrict.DecisionThrottle, d4.Type)
+
+	// Range ban should still be active.
+	assert.NotNil(t, b.CheckIP(netip.MustParseAddr("10.99.99.99")))
+}
+
+// Helpers
+
+func newTestBouncer() *Bouncer {
+	return &Bouncer{
+		ips:      make(map[netip.Addr]*restrict.CrowdSecDecision),
+		prefixes: make(map[netip.Prefix]*restrict.CrowdSecDecision),
+		logger:   log.NewEntry(log.StandardLogger()),
+	}
+}
+
+type decision struct {
+	scope    string
+	value    string
+	dtype    string
+	scenario string
+}
+
+func makeDecisions(decs ...decision) []*models.Decision {
+	out := make([]*models.Decision, len(decs))
+	for i, d := range decs {
+		out[i] = &models.Decision{
+			Scope:    strPtr(d.scope),
+			Value:    strPtr(d.value),
+			Type:     strPtr(d.dtype),
+			Scenario: strPtr(d.scenario),
+			Duration: strPtr("1h"),
+			Origin:   strPtr("cscli"),
+		}
+	}
+	return out
+}
+
+func strPtr(s string) *string { return &s }
+
+// fakeLAPI is a minimal fake CrowdSec LAPI that serves /v1/decisions/stream.
+type fakeLAPI struct {
+	mu       sync.Mutex
+	initial  []decision
+	newDelta []decision
+	delDelta []decision
+	served   bool // true after the initial snapshot has been served
+}
+
+func newFakeLAPI() *fakeLAPI {
+	return &fakeLAPI{}
+}
+
+func (f *fakeLAPI) setDecisions(decs ...decision) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	f.initial = decs
+	f.served = false
+}
+
+func (f *fakeLAPI) setDelta(deleted, added []decision) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	f.delDelta = deleted
+	f.newDelta = added
+}
+
+func (f *fakeLAPI) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	if r.URL.Path != "/v1/decisions/stream" {
+		http.NotFound(w, r)
+		return
+	}
+
+	f.mu.Lock()
+	defer f.mu.Unlock()
+
+	resp := streamResponse{}
+
+	if !f.served {
+		for _, d := range f.initial {
+			resp.New = append(resp.New, toLAPIDecision(d))
+		}
+		f.served = true
+	} else {
+		for _, d := range f.delDelta {
+			resp.Deleted = append(resp.Deleted, toLAPIDecision(d))
+		}
+		for _, d := range f.newDelta {
+			resp.New = append(resp.New, toLAPIDecision(d))
+		}
+		// Clear delta after serving once.
+		f.delDelta = nil
+		f.newDelta = nil
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	json.NewEncoder(w).Encode(resp) //nolint:errcheck
+}
+
+// streamResponse mirrors the CrowdSec LAPI /v1/decisions/stream JSON structure.
+type streamResponse struct {
+	New     []*lapiDecision `json:"new"`
+	Deleted []*lapiDecision `json:"deleted"`
+}
+
+type lapiDecision struct {
+	Duration *string `json:"duration"`
+	Origin   *string `json:"origin"`
+	Scenario *string `json:"scenario"`
+	Scope    *string `json:"scope"`
+	Type     *string `json:"type"`
+	Value    *string `json:"value"`
+}
+
+func toLAPIDecision(d decision) *lapiDecision {
+	return &lapiDecision{
+		Duration: strPtr("1h"),
+		Origin:   strPtr("cscli"),
+		Scenario: strPtr(d.scenario),
+		Scope:    strPtr(d.scope),
+		Type:     strPtr(d.dtype),
+		Value:    strPtr(d.value),
+	}
+}

proxy/internal/crowdsec/registry.go

@@ -0,0 +1,103 @@
+package crowdsec
+
+import (
+	"context"
+	"sync"
+
+	log "github.com/sirupsen/logrus"
+
+	"github.com/netbirdio/netbird/proxy/internal/types"
+)
+
+// Registry manages a single shared Bouncer instance with reference counting.
+// The bouncer starts when the first service acquires it and stops when the
+// last service releases it.
+type Registry struct {
+	mu      sync.Mutex
+	bouncer *Bouncer
+	refs    map[types.ServiceID]struct{}
+	apiURL  string
+	apiKey  string
+	logger  *log.Entry
+	cancel  context.CancelFunc
+}
+
+// NewRegistry creates a registry. The bouncer is not started until Acquire is called.
+func NewRegistry(apiURL, apiKey string, logger *log.Entry) *Registry {
+	return &Registry{
+		apiURL: apiURL,
+		apiKey: apiKey,
+		logger: logger,
+		refs:   make(map[types.ServiceID]struct{}),
+	}
+}
+
+// Available returns true when the LAPI URL and API key are configured.
+func (r *Registry) Available() bool {
+	return r.apiURL != "" && r.apiKey != ""
+}
+
+// Acquire registers svcID as a consumer and starts the bouncer if this is the
+// first consumer. Returns the shared Bouncer (which implements the restrict
+// package's CrowdSecChecker interface). Returns nil if not Available.
+func (r *Registry) Acquire(svcID types.ServiceID) *Bouncer {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+
+	if !r.Available() {
+		return nil
+	}
+
+	if _, exists := r.refs[svcID]; exists {
+		return r.bouncer
+	}
+
+	if r.bouncer == nil {
+		r.startLocked()
+	}
+
+	// startLocked may fail, leaving r.bouncer nil.
+	if r.bouncer == nil {
+		return nil
+	}
+
+	r.refs[svcID] = struct{}{}
+	return r.bouncer
+}
+
+// Release removes svcID as a consumer. Stops the bouncer when the last
+// consumer releases.
+func (r *Registry) Release(svcID types.ServiceID) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+
+	delete(r.refs, svcID)
+
+	if len(r.refs) == 0 && r.bouncer != nil {
+		r.stopLocked()
+	}
+}
+
+func (r *Registry) startLocked() {
+	b := NewBouncer(r.apiURL, r.apiKey, r.logger)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	r.cancel = cancel
+
+	if err := b.Start(ctx); err != nil {
+		r.logger.Errorf("failed to start CrowdSec bouncer: %v", err)
+		cancel()
+		return
+	}
+
+	r.bouncer = b
+	r.logger.Info("CrowdSec bouncer started")
+}
+
+func (r *Registry) stopLocked() {
+	r.bouncer.Stop()
+	r.cancel()
+	r.bouncer = nil
+	r.cancel = nil
+	r.logger.Info("CrowdSec bouncer stopped")
+}

proxy/internal/crowdsec/registry_test.go

@@ -0,0 +1,66 @@
+package crowdsec
+
+import (
+	"testing"
+
+	log "github.com/sirupsen/logrus"
+	"github.com/stretchr/testify/assert"
+
+	"github.com/netbirdio/netbird/proxy/internal/types"
+)
+
+func TestRegistry_Available(t *testing.T) {
+	r := NewRegistry("http://localhost:8080/", "test-key", log.NewEntry(log.StandardLogger()))
+	assert.True(t, r.Available())
+
+	r2 := NewRegistry("", "", log.NewEntry(log.StandardLogger()))
+	assert.False(t, r2.Available())
+
+	r3 := NewRegistry("http://localhost:8080/", "", log.NewEntry(log.StandardLogger()))
+	assert.False(t, r3.Available())
+}
+
+func TestRegistry_Acquire_NotAvailable(t *testing.T) {
+	r := NewRegistry("", "", log.NewEntry(log.StandardLogger()))
+	b := r.Acquire("svc-1")
+	assert.Nil(t, b)
+}
+
+func TestRegistry_Acquire_Idempotent(t *testing.T) {
+	r := newTestRegistry()
+
+	b1 := r.Acquire("svc-1")
+	// Can't start without a real LAPI, but we can verify the ref tracking.
+	// The bouncer will be nil because Start fails, but the ref is tracked.
+	_ = b1
+
+	assert.Len(t, r.refs, 1)
+
+	// Second acquire of same service should not add another ref.
+	r.Acquire("svc-1")
+	assert.Len(t, r.refs, 1)
+}
+
+func TestRegistry_Release_Removes(t *testing.T) {
+	r := newTestRegistry()
+	r.refs[types.ServiceID("svc-1")] = struct{}{}
+
+	r.Release("svc-1")
+	assert.Empty(t, r.refs)
+}
+
+func TestRegistry_Release_Noop(t *testing.T) {
+	r := newTestRegistry()
+	// Releasing a service that was never acquired should not panic.
+	r.Release("nonexistent")
+	assert.Empty(t, r.refs)
+}
+
+func newTestRegistry() *Registry {
+	return &Registry{
+		apiURL: "http://localhost:8080/",
+		apiKey: "test-key",
+		logger: log.NewEntry(log.StandardLogger()),
+		refs:   make(map[types.ServiceID]struct{}),
+	}
+}

proxy/internal/proxy/context.go

@@ -2,6 +2,7 @@ package proxy
 
 import (
 	"context"
+	"maps"
 	"net/netip"
 	"sync"
 
@@ -52,6 +53,7 @@ type CapturedData struct {
 	clientIP   netip.Addr
 	userID     string
 	authMethod string
+	metadata   map[string]string
 }
 
 // NewCapturedData creates a CapturedData with the given request ID.
@@ -150,6 +152,23 @@ func (c *CapturedData) GetAuthMethod() string {
 	return c.authMethod
 }
 
+// SetMetadata sets a key-value pair in the metadata map.
+func (c *CapturedData) SetMetadata(key, value string) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if c.metadata == nil {
+		c.metadata = make(map[string]string)
+	}
+	c.metadata[key] = value
+}
+
+// GetMetadata returns a copy of the metadata map.
+func (c *CapturedData) GetMetadata() map[string]string {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+	return maps.Clone(c.metadata)
+}
+
 // WithCapturedData adds a CapturedData struct to the context.
 func WithCapturedData(ctx context.Context, data *CapturedData) context.Context {
 	return context.WithValue(ctx, capturedDataKey, data)

proxy/internal/restrict/restrict.go

@@ -12,12 +12,44 @@ import (
 	"github.com/netbirdio/netbird/proxy/internal/geolocation"
 )
 
+// defaultLogger is used when no logger is provided to ParseFilter.
+var defaultLogger = log.NewEntry(log.StandardLogger())
+
 // GeoResolver resolves an IP address to geographic information.
 type GeoResolver interface {
 	LookupAddr(addr netip.Addr) geolocation.Result
 	Available() bool
 }
 
+// DecisionType is the type of CrowdSec remediation action.
+type DecisionType string
+
+const (
+	DecisionBan      DecisionType = "ban"
+	DecisionCaptcha  DecisionType = "captcha"
+	DecisionThrottle DecisionType = "throttle"
+)
+
+// CrowdSecDecision holds the type of a CrowdSec decision.
+type CrowdSecDecision struct {
+	Type DecisionType
+}
+
+// CrowdSecChecker queries CrowdSec decisions for an IP address.
+type CrowdSecChecker interface {
+	CheckIP(addr netip.Addr) *CrowdSecDecision
+	Ready() bool
+}
+
+// CrowdSecMode is the per-service enforcement mode.
+type CrowdSecMode string
+
+const (
+	CrowdSecOff     CrowdSecMode = ""
+	CrowdSecEnforce CrowdSecMode = "enforce"
+	CrowdSecObserve CrowdSecMode = "observe"
+)
+
 // Filter evaluates IP restrictions. CIDR checks are performed first
 // (cheap), followed by country lookups (more expensive) only when needed.
 type Filter struct {
@@ -25,32 +57,55 @@ type Filter struct {
 	BlockedCIDRs     []netip.Prefix
 	AllowedCountries []string
 	BlockedCountries []string
+	CrowdSec         CrowdSecChecker
+	CrowdSecMode     CrowdSecMode
 }
 
-// ParseFilter builds a Filter from the raw string slices. Returns nil
-// if all slices are empty.
-func ParseFilter(allowedCIDRs, blockedCIDRs, allowedCountries, blockedCountries []string) *Filter {
-	if len(allowedCIDRs) == 0 && len(blockedCIDRs) == 0 &&
-		len(allowedCountries) == 0 && len(blockedCountries) == 0 {
+// FilterConfig holds the raw configuration for building a Filter.
+type FilterConfig struct {
+	AllowedCIDRs     []string
+	BlockedCIDRs     []string
+	AllowedCountries []string
+	BlockedCountries []string
+	CrowdSec         CrowdSecChecker
+	CrowdSecMode     CrowdSecMode
+	Logger           *log.Entry
+}
+
+// ParseFilter builds a Filter from the config. Returns nil if no restrictions
+// are configured.
+func ParseFilter(cfg FilterConfig) *Filter {
+	hasCS := cfg.CrowdSecMode == CrowdSecEnforce || cfg.CrowdSecMode == CrowdSecObserve
+	if len(cfg.AllowedCIDRs) == 0 && len(cfg.BlockedCIDRs) == 0 &&
+		len(cfg.AllowedCountries) == 0 && len(cfg.BlockedCountries) == 0 && !hasCS {
 		return nil
 	}
 
-	f := &Filter{
-		AllowedCountries: normalizeCountryCodes(allowedCountries),
-		BlockedCountries: normalizeCountryCodes(blockedCountries),
+	logger := cfg.Logger
+	if logger == nil {
+		logger = defaultLogger
 	}
-	for _, cidr := range allowedCIDRs {
+
+	f := &Filter{
+		AllowedCountries: normalizeCountryCodes(cfg.AllowedCountries),
+		BlockedCountries: normalizeCountryCodes(cfg.BlockedCountries),
+	}
+	if hasCS {
+		f.CrowdSec = cfg.CrowdSec
+		f.CrowdSecMode = cfg.CrowdSecMode
+	}
+	for _, cidr := range cfg.AllowedCIDRs {
 		prefix, err := netip.ParsePrefix(cidr)
 		if err != nil {
-			log.Warnf("skip invalid allowed CIDR %q: %v", cidr, err)
+			logger.Warnf("skip invalid allowed CIDR %q: %v", cidr, err)
 			continue
 		}
 		f.AllowedCIDRs = append(f.AllowedCIDRs, prefix.Masked())
 	}
-	for _, cidr := range blockedCIDRs {
+	for _, cidr := range cfg.BlockedCIDRs {
 		prefix, err := netip.ParsePrefix(cidr)
 		if err != nil {
-			log.Warnf("skip invalid blocked CIDR %q: %v", cidr, err)
+			logger.Warnf("skip invalid blocked CIDR %q: %v", cidr, err)
 			continue
 		}
 		f.BlockedCIDRs = append(f.BlockedCIDRs, prefix.Masked())
@@ -82,6 +137,15 @@ const (
 	// DenyGeoUnavailable indicates that country restrictions are configured
 	// but the geo lookup is unavailable.
 	DenyGeoUnavailable
+	// DenyCrowdSecBan indicates a CrowdSec "ban" decision.
+	DenyCrowdSecBan
+	// DenyCrowdSecCaptcha indicates a CrowdSec "captcha" decision.
+	DenyCrowdSecCaptcha
+	// DenyCrowdSecThrottle indicates a CrowdSec "throttle" decision.
+	DenyCrowdSecThrottle
+	// DenyCrowdSecUnavailable indicates enforce mode but the bouncer has not
+	// completed its initial sync.
+	DenyCrowdSecUnavailable
 )
 
 // String returns the deny reason string matching the HTTP auth mechanism names.
@@ -95,14 +159,42 @@ func (v Verdict) String() string {
 		return "country_restricted"
 	case DenyGeoUnavailable:
 		return "geo_unavailable"
+	case DenyCrowdSecBan:
+		return "crowdsec_ban"
+	case DenyCrowdSecCaptcha:
+		return "crowdsec_captcha"
+	case DenyCrowdSecThrottle:
+		return "crowdsec_throttle"
+	case DenyCrowdSecUnavailable:
+		return "crowdsec_unavailable"
 	default:
 		return "unknown"
 	}
 }
 
+// IsCrowdSec returns true when the verdict originates from a CrowdSec check.
+func (v Verdict) IsCrowdSec() bool {
+	switch v {
+	case DenyCrowdSecBan, DenyCrowdSecCaptcha, DenyCrowdSecThrottle, DenyCrowdSecUnavailable:
+		return true
+	default:
+		return false
+	}
+}
+
+// IsObserveOnly returns true when v is a CrowdSec verdict and the filter is in
+// observe mode. Callers should log the verdict but not block the request.
+func (f *Filter) IsObserveOnly(v Verdict) bool {
+	if f == nil {
+		return false
+	}
+	return v.IsCrowdSec() && f.CrowdSecMode == CrowdSecObserve
+}
+
 // Check evaluates whether addr is permitted. CIDR rules are evaluated
 // first because they are O(n) prefix comparisons. Country rules run
-// only when CIDR checks pass and require a geo lookup.
+// only when CIDR checks pass and require a geo lookup. CrowdSec checks
+// run last.
 func (f *Filter) Check(addr netip.Addr, geo GeoResolver) Verdict {
 	if f == nil {
 		return Allow
@@ -115,7 +207,10 @@ func (f *Filter) Check(addr netip.Addr, geo GeoResolver) Verdict {
 	if v := f.checkCIDR(addr); v != Allow {
 		return v
 	}
-	return f.checkCountry(addr, geo)
+	if v := f.checkCountry(addr, geo); v != Allow {
+		return v
+	}
+	return f.checkCrowdSec(addr)
 }
 
 func (f *Filter) checkCIDR(addr netip.Addr) Verdict {
@@ -173,11 +268,48 @@ func (f *Filter) checkCountry(addr netip.Addr, geo GeoResolver) Verdict {
 	return Allow
 }
 
+func (f *Filter) checkCrowdSec(addr netip.Addr) Verdict {
+	if f.CrowdSecMode == CrowdSecOff {
+		return Allow
+	}
+
+	// Checker nil with enforce means CrowdSec was requested but the proxy
+	// has no LAPI configured. Fail-closed.
+	if f.CrowdSec == nil {
+		if f.CrowdSecMode == CrowdSecEnforce {
+			return DenyCrowdSecUnavailable
+		}
+		return Allow
+	}
+
+	if !f.CrowdSec.Ready() {
+		if f.CrowdSecMode == CrowdSecEnforce {
+			return DenyCrowdSecUnavailable
+		}
+		return Allow
+	}
+
+	d := f.CrowdSec.CheckIP(addr)
+	if d == nil {
+		return Allow
+	}
+
+	switch d.Type {
+	case DecisionCaptcha:
+		return DenyCrowdSecCaptcha
+	case DecisionThrottle:
+		return DenyCrowdSecThrottle
+	default:
+		return DenyCrowdSecBan
+	}
+}
+
 // HasRestrictions returns true if any restriction rules are configured.
 func (f *Filter) HasRestrictions() bool {
 	if f == nil {
 		return false
 	}
 	return len(f.AllowedCIDRs) > 0 || len(f.BlockedCIDRs) > 0 ||
-		len(f.AllowedCountries) > 0 || len(f.BlockedCountries) > 0
+		len(f.AllowedCountries) > 0 || len(f.BlockedCountries) > 0 ||
+		f.CrowdSecMode == CrowdSecEnforce || f.CrowdSecMode == CrowdSecObserve
 }

proxy/internal/restrict/restrict_test.go

@@ -29,21 +29,21 @@ func TestFilter_Check_NilFilter(t *testing.T) {
 }
 
 func TestFilter_Check_AllowedCIDR(t *testing.T) {
-	f := ParseFilter([]string{"10.0.0.0/8"}, nil, nil, nil)
+	f := ParseFilter(FilterConfig{AllowedCIDRs: []string{"10.0.0.0/8"}})
 
 	assert.Equal(t, Allow, f.Check(netip.MustParseAddr("10.1.2.3"), nil))
 	assert.Equal(t, DenyCIDR, f.Check(netip.MustParseAddr("192.168.1.1"), nil))
 }
 
 func TestFilter_Check_BlockedCIDR(t *testing.T) {
-	f := ParseFilter(nil, []string{"10.0.0.0/8"}, nil, nil)
+	f := ParseFilter(FilterConfig{BlockedCIDRs: []string{"10.0.0.0/8"}})
 
 	assert.Equal(t, DenyCIDR, f.Check(netip.MustParseAddr("10.1.2.3"), nil))
 	assert.Equal(t, Allow, f.Check(netip.MustParseAddr("192.168.1.1"), nil))
 }
 
 func TestFilter_Check_AllowedAndBlockedCIDR(t *testing.T) {
-	f := ParseFilter([]string{"10.0.0.0/8"}, []string{"10.1.0.0/16"}, nil, nil)
+	f := ParseFilter(FilterConfig{AllowedCIDRs: []string{"10.0.0.0/8"}, BlockedCIDRs: []string{"10.1.0.0/16"}})
 
 	assert.Equal(t, Allow, f.Check(netip.MustParseAddr("10.2.3.4"), nil), "allowed by allowlist, not in blocklist")
 	assert.Equal(t, DenyCIDR, f.Check(netip.MustParseAddr("10.1.2.3"), nil), "allowed by allowlist but in blocklist")
@@ -56,7 +56,7 @@ func TestFilter_Check_AllowedCountry(t *testing.T) {
 		"2.2.2.2": "DE",
 		"3.3.3.3": "CN",
 	})
-	f := ParseFilter(nil, nil, []string{"US", "DE"}, nil)
+	f := ParseFilter(FilterConfig{AllowedCountries: []string{"US", "DE"}})
 
 	assert.Equal(t, Allow, f.Check(netip.MustParseAddr("1.1.1.1"), geo), "US in allowlist")
 	assert.Equal(t, Allow, f.Check(netip.MustParseAddr("2.2.2.2"), geo), "DE in allowlist")
@@ -69,7 +69,7 @@ func TestFilter_Check_BlockedCountry(t *testing.T) {
 		"2.2.2.2": "RU",
 		"3.3.3.3": "US",
 	})
-	f := ParseFilter(nil, nil, nil, []string{"CN", "RU"})
+	f := ParseFilter(FilterConfig{BlockedCountries: []string{"CN", "RU"}})
 
 	assert.Equal(t, DenyCountry, f.Check(netip.MustParseAddr("1.1.1.1"), geo), "CN in blocklist")
 	assert.Equal(t, DenyCountry, f.Check(netip.MustParseAddr("2.2.2.2"), geo), "RU in blocklist")
@@ -83,7 +83,7 @@ func TestFilter_Check_AllowedAndBlockedCountry(t *testing.T) {
 		"3.3.3.3": "CN",
 	})
 	// Allow US and DE, but block DE explicitly.
-	f := ParseFilter(nil, nil, []string{"US", "DE"}, []string{"DE"})
+	f := ParseFilter(FilterConfig{AllowedCountries: []string{"US", "DE"}, BlockedCountries: []string{"DE"}})
 
 	assert.Equal(t, Allow, f.Check(netip.MustParseAddr("1.1.1.1"), geo), "US allowed and not blocked")
 	assert.Equal(t, DenyCountry, f.Check(netip.MustParseAddr("2.2.2.2"), geo), "DE allowed but also blocked, block wins")
@@ -94,7 +94,7 @@ func TestFilter_Check_UnknownCountryWithAllowlist(t *testing.T) {
 	geo := newMockGeo(map[string]string{
 		"1.1.1.1": "US",
 	})
-	f := ParseFilter(nil, nil, []string{"US"}, nil)
+	f := ParseFilter(FilterConfig{AllowedCountries: []string{"US"}})
 
 	assert.Equal(t, Allow, f.Check(netip.MustParseAddr("1.1.1.1"), geo), "known US in allowlist")
 	assert.Equal(t, DenyCountry, f.Check(netip.MustParseAddr("9.9.9.9"), geo), "unknown country denied when allowlist is active")
@@ -104,34 +104,34 @@ func TestFilter_Check_UnknownCountryWithBlocklistOnly(t *testing.T) {
 	geo := newMockGeo(map[string]string{
 		"1.1.1.1": "CN",
 	})
-	f := ParseFilter(nil, nil, nil, []string{"CN"})
+	f := ParseFilter(FilterConfig{BlockedCountries: []string{"CN"}})
 
 	assert.Equal(t, DenyCountry, f.Check(netip.MustParseAddr("1.1.1.1"), geo), "known CN in blocklist")
 	assert.Equal(t, Allow, f.Check(netip.MustParseAddr("9.9.9.9"), geo), "unknown country allowed when only blocklist is active")
 }
 
 func TestFilter_Check_CountryWithoutGeo(t *testing.T) {
-	f := ParseFilter(nil, nil, []string{"US"}, nil)
+	f := ParseFilter(FilterConfig{AllowedCountries: []string{"US"}})
 	assert.Equal(t, DenyGeoUnavailable, f.Check(netip.MustParseAddr("1.2.3.4"), nil), "nil geo with country allowlist")
 }
 
 func TestFilter_Check_CountryBlocklistWithoutGeo(t *testing.T) {
-	f := ParseFilter(nil, nil, nil, []string{"CN"})
+	f := ParseFilter(FilterConfig{BlockedCountries: []string{"CN"}})
 	assert.Equal(t, DenyGeoUnavailable, f.Check(netip.MustParseAddr("1.2.3.4"), nil), "nil geo with country blocklist")
 }
 
 func TestFilter_Check_GeoUnavailable(t *testing.T) {
 	geo := &unavailableGeo{}
 
-	f := ParseFilter(nil, nil, []string{"US"}, nil)
+	f := ParseFilter(FilterConfig{AllowedCountries: []string{"US"}})
 	assert.Equal(t, DenyGeoUnavailable, f.Check(netip.MustParseAddr("1.2.3.4"), geo), "unavailable geo with country allowlist")
 
-	f2 := ParseFilter(nil, nil, nil, []string{"CN"})
+	f2 := ParseFilter(FilterConfig{BlockedCountries: []string{"CN"}})
 	assert.Equal(t, DenyGeoUnavailable, f2.Check(netip.MustParseAddr("1.2.3.4"), geo), "unavailable geo with country blocklist")
 }
 
 func TestFilter_Check_CIDROnlySkipsGeo(t *testing.T) {
-	f := ParseFilter([]string{"10.0.0.0/8"}, nil, nil, nil)
+	f := ParseFilter(FilterConfig{AllowedCIDRs: []string{"10.0.0.0/8"}})
 
 	// CIDR-only filter should never touch geo, so nil geo is fine.
 	assert.Equal(t, Allow, f.Check(netip.MustParseAddr("10.1.2.3"), nil))
@@ -143,7 +143,7 @@ func TestFilter_Check_CIDRAllowThenCountryBlock(t *testing.T) {
 		"10.1.2.3": "CN",
 		"10.2.3.4": "US",
 	})
-	f := ParseFilter([]string{"10.0.0.0/8"}, nil, nil, []string{"CN"})
+	f := ParseFilter(FilterConfig{AllowedCIDRs: []string{"10.0.0.0/8"}, BlockedCountries: []string{"CN"}})
 
 	assert.Equal(t, DenyCountry, f.Check(netip.MustParseAddr("10.1.2.3"), geo), "CIDR allowed but country blocked")
 	assert.Equal(t, Allow, f.Check(netip.MustParseAddr("10.2.3.4"), geo), "CIDR allowed and country not blocked")
@@ -151,12 +151,12 @@ func TestFilter_Check_CIDRAllowThenCountryBlock(t *testing.T) {
 }
 
 func TestParseFilter_Empty(t *testing.T) {
-	f := ParseFilter(nil, nil, nil, nil)
+	f := ParseFilter(FilterConfig{})
 	assert.Nil(t, f)
 }
 
 func TestParseFilter_InvalidCIDR(t *testing.T) {
-	f := ParseFilter([]string{"invalid", "10.0.0.0/8"}, nil, nil, nil)
+	f := ParseFilter(FilterConfig{AllowedCIDRs: []string{"invalid", "10.0.0.0/8"}})
 
 	assert.NotNil(t, f)
 	assert.Len(t, f.AllowedCIDRs, 1, "invalid CIDR should be skipped")
@@ -166,12 +166,12 @@ func TestParseFilter_InvalidCIDR(t *testing.T) {
 func TestFilter_HasRestrictions(t *testing.T) {
 	assert.False(t, (*Filter)(nil).HasRestrictions())
 	assert.False(t, (&Filter{}).HasRestrictions())
-	assert.True(t, ParseFilter([]string{"10.0.0.0/8"}, nil, nil, nil).HasRestrictions())
-	assert.True(t, ParseFilter(nil, nil, []string{"US"}, nil).HasRestrictions())
+	assert.True(t, ParseFilter(FilterConfig{AllowedCIDRs: []string{"10.0.0.0/8"}}).HasRestrictions())
+	assert.True(t, ParseFilter(FilterConfig{AllowedCountries: []string{"US"}}).HasRestrictions())
 }
 
 func TestFilter_Check_IPv6CIDR(t *testing.T) {
-	f := ParseFilter([]string{"2001:db8::/32"}, nil, nil, nil)
+	f := ParseFilter(FilterConfig{AllowedCIDRs: []string{"2001:db8::/32"}})
 
 	assert.Equal(t, Allow, f.Check(netip.MustParseAddr("2001:db8::1"), nil), "v6 addr in v6 allowlist")
 	assert.Equal(t, DenyCIDR, f.Check(netip.MustParseAddr("2001:db9::1"), nil), "v6 addr not in v6 allowlist")
@@ -179,7 +179,7 @@ func TestFilter_Check_IPv6CIDR(t *testing.T) {
 }
 
 func TestFilter_Check_IPv4MappedIPv6(t *testing.T) {
-	f := ParseFilter([]string{"10.0.0.0/8"}, nil, nil, nil)
+	f := ParseFilter(FilterConfig{AllowedCIDRs: []string{"10.0.0.0/8"}})
 
 	// A v4-mapped-v6 address like ::ffff:10.1.2.3 must match a v4 CIDR.
 	v4mapped := netip.MustParseAddr("::ffff:10.1.2.3")
@@ -191,7 +191,7 @@ func TestFilter_Check_IPv4MappedIPv6(t *testing.T) {
 }
 
 func TestFilter_Check_MixedV4V6CIDRs(t *testing.T) {
-	f := ParseFilter([]string{"10.0.0.0/8", "2001:db8::/32"}, nil, nil, nil)
+	f := ParseFilter(FilterConfig{AllowedCIDRs: []string{"10.0.0.0/8", "2001:db8::/32"}})
 
 	assert.Equal(t, Allow, f.Check(netip.MustParseAddr("10.1.2.3"), nil), "v4 in v4 CIDR")
 	assert.Equal(t, Allow, f.Check(netip.MustParseAddr("2001:db8::1"), nil), "v6 in v6 CIDR")
@@ -202,7 +202,7 @@ func TestFilter_Check_MixedV4V6CIDRs(t *testing.T) {
 
 func TestParseFilter_CanonicalizesNonMaskedCIDR(t *testing.T) {
 	// 1.1.1.1/24 has host bits set; ParseFilter should canonicalize to 1.1.1.0/24.
-	f := ParseFilter([]string{"1.1.1.1/24"}, nil, nil, nil)
+	f := ParseFilter(FilterConfig{AllowedCIDRs: []string{"1.1.1.1/24"}})
 	assert.Equal(t, netip.MustParsePrefix("1.1.1.0/24"), f.AllowedCIDRs[0])
 
 	// Verify it still matches correctly.
@@ -264,7 +264,7 @@ func TestFilter_Check_CountryCodeCaseInsensitive(t *testing.T) {
 
 	for _, tc := range tests {
 		t.Run(tc.name, func(t *testing.T) {
-			f := ParseFilter(nil, nil, tc.allowedCountries, tc.blockedCountries)
+			f := ParseFilter(FilterConfig{AllowedCountries: tc.allowedCountries, BlockedCountries: tc.blockedCountries})
 			got := f.Check(netip.MustParseAddr(tc.addr), geo)
 			assert.Equal(t, tc.want, got)
 		})
@@ -275,4 +275,252 @@ func TestFilter_Check_CountryCodeCaseInsensitive(t *testing.T) {
 type unavailableGeo struct{}
 
 func (u *unavailableGeo) LookupAddr(_ netip.Addr) geolocation.Result { return geolocation.Result{} }
-func (u *unavailableGeo) Available() bool                             { return false }
+func (u *unavailableGeo) Available() bool                            { return false }
+
+// mockCrowdSec is a test implementation of CrowdSecChecker.
+type mockCrowdSec struct {
+	decisions map[string]*CrowdSecDecision
+	ready     bool
+}
+
+func (m *mockCrowdSec) CheckIP(addr netip.Addr) *CrowdSecDecision {
+	return m.decisions[addr.Unmap().String()]
+}
+
+func (m *mockCrowdSec) Ready() bool { return m.ready }
+
+func TestFilter_CrowdSec_Enforce_Ban(t *testing.T) {
+	cs := &mockCrowdSec{
+		decisions: map[string]*CrowdSecDecision{"1.2.3.4": {Type: DecisionBan}},
+		ready:     true,
+	}
+	f := ParseFilter(FilterConfig{CrowdSec: cs, CrowdSecMode: CrowdSecEnforce})
+
+	assert.Equal(t, DenyCrowdSecBan, f.Check(netip.MustParseAddr("1.2.3.4"), nil))
+	assert.Equal(t, Allow, f.Check(netip.MustParseAddr("5.6.7.8"), nil))
+}
+
+func TestFilter_CrowdSec_Enforce_Captcha(t *testing.T) {
+	cs := &mockCrowdSec{
+		decisions: map[string]*CrowdSecDecision{"1.2.3.4": {Type: DecisionCaptcha}},
+		ready:     true,
+	}
+	f := ParseFilter(FilterConfig{CrowdSec: cs, CrowdSecMode: CrowdSecEnforce})
+
+	assert.Equal(t, DenyCrowdSecCaptcha, f.Check(netip.MustParseAddr("1.2.3.4"), nil))
+}
+
+func TestFilter_CrowdSec_Enforce_Throttle(t *testing.T) {
+	cs := &mockCrowdSec{
+		decisions: map[string]*CrowdSecDecision{"1.2.3.4": {Type: DecisionThrottle}},
+		ready:     true,
+	}
+	f := ParseFilter(FilterConfig{CrowdSec: cs, CrowdSecMode: CrowdSecEnforce})
+
+	assert.Equal(t, DenyCrowdSecThrottle, f.Check(netip.MustParseAddr("1.2.3.4"), nil))
+}
+
+func TestFilter_CrowdSec_Observe_DoesNotBlock(t *testing.T) {
+	cs := &mockCrowdSec{
+		decisions: map[string]*CrowdSecDecision{"1.2.3.4": {Type: DecisionBan}},
+		ready:     true,
+	}
+	f := ParseFilter(FilterConfig{CrowdSec: cs, CrowdSecMode: CrowdSecObserve})
+
+	verdict := f.Check(netip.MustParseAddr("1.2.3.4"), nil)
+	assert.Equal(t, DenyCrowdSecBan, verdict, "verdict should be ban")
+	assert.True(t, f.IsObserveOnly(verdict), "should be observe-only")
+}
+
+func TestFilter_CrowdSec_Enforce_NotReady(t *testing.T) {
+	cs := &mockCrowdSec{ready: false}
+	f := ParseFilter(FilterConfig{CrowdSec: cs, CrowdSecMode: CrowdSecEnforce})
+
+	assert.Equal(t, DenyCrowdSecUnavailable, f.Check(netip.MustParseAddr("1.2.3.4"), nil))
+}
+
+func TestFilter_CrowdSec_Observe_NotReady_Allows(t *testing.T) {
+	cs := &mockCrowdSec{ready: false}
+	f := ParseFilter(FilterConfig{CrowdSec: cs, CrowdSecMode: CrowdSecObserve})
+
+	assert.Equal(t, Allow, f.Check(netip.MustParseAddr("1.2.3.4"), nil))
+}
+
+func TestFilter_CrowdSec_Off(t *testing.T) {
+	cs := &mockCrowdSec{
+		decisions: map[string]*CrowdSecDecision{"1.2.3.4": {Type: DecisionBan}},
+		ready:     true,
+	}
+	f := ParseFilter(FilterConfig{CrowdSec: cs, CrowdSecMode: CrowdSecOff})
+
+	// CrowdSecOff means the filter is nil (no restrictions).
+	assert.Nil(t, f)
+}
+
+func TestFilter_IsObserveOnly(t *testing.T) {
+	f := &Filter{CrowdSecMode: CrowdSecObserve}
+	assert.True(t, f.IsObserveOnly(DenyCrowdSecBan))
+	assert.True(t, f.IsObserveOnly(DenyCrowdSecCaptcha))
+	assert.True(t, f.IsObserveOnly(DenyCrowdSecThrottle))
+	assert.True(t, f.IsObserveOnly(DenyCrowdSecUnavailable))
+	assert.False(t, f.IsObserveOnly(DenyCIDR))
+	assert.False(t, f.IsObserveOnly(Allow))
+
+	f2 := &Filter{CrowdSecMode: CrowdSecEnforce}
+	assert.False(t, f2.IsObserveOnly(DenyCrowdSecBan))
+}
+
+// TestFilter_LayerInteraction exercises the evaluation order across all three
+// restriction layers: CIDR -> Country -> CrowdSec. Each layer can only further
+// restrict; no layer can relax a denial from an earlier layer.
+//
+//	Layer order    | Behavior
+//	---------------|-------------------------------------------------------
+//	1. CIDR        | Allowlist narrows to specific ranges, blocklist removes
+//	               | specific ranges. Deny here → stop, CrowdSec never runs.
+//	2. Country     | Allowlist/blocklist by geo. Deny here → stop.
+//	3. CrowdSec    | IP reputation. Can block IPs that passed layers 1-2.
+//	               | Observe mode: verdict returned but caller doesn't block.
+func TestFilter_LayerInteraction(t *testing.T) {
+	bannedIP := "10.1.2.3"
+	cleanIP := "10.2.3.4"
+	outsideIP := "192.168.1.1"
+
+	cs := &mockCrowdSec{
+		decisions: map[string]*CrowdSecDecision{bannedIP: {Type: DecisionBan}},
+		ready:     true,
+	}
+	geo := newMockGeo(map[string]string{
+		bannedIP:  "US",
+		cleanIP:   "US",
+		outsideIP: "CN",
+	})
+
+	tests := []struct {
+		name   string
+		config FilterConfig
+		addr   string
+		want   Verdict
+	}{
+		// CIDR allowlist + CrowdSec enforce: CrowdSec blocks inside allowed range
+		{
+			name:   "allowed CIDR + CrowdSec banned",
+			config: FilterConfig{AllowedCIDRs: []string{"10.0.0.0/8"}, CrowdSec: cs, CrowdSecMode: CrowdSecEnforce},
+			addr:   bannedIP,
+			want:   DenyCrowdSecBan,
+		},
+		{
+			name:   "allowed CIDR + CrowdSec clean",
+			config: FilterConfig{AllowedCIDRs: []string{"10.0.0.0/8"}, CrowdSec: cs, CrowdSecMode: CrowdSecEnforce},
+			addr:   cleanIP,
+			want:   Allow,
+		},
+		{
+			name:   "CIDR deny stops before CrowdSec",
+			config: FilterConfig{AllowedCIDRs: []string{"10.0.0.0/8"}, CrowdSec: cs, CrowdSecMode: CrowdSecEnforce},
+			addr:   outsideIP,
+			want:   DenyCIDR,
+		},
+
+		// CIDR blocklist + CrowdSec enforce: blocklist blocks first, CrowdSec blocks remaining
+		{
+			name:   "blocked CIDR stops before CrowdSec",
+			config: FilterConfig{BlockedCIDRs: []string{"10.1.0.0/16"}, CrowdSec: cs, CrowdSecMode: CrowdSecEnforce},
+			addr:   bannedIP,
+			want:   DenyCIDR,
+		},
+		{
+			name:   "not in blocklist + CrowdSec clean",
+			config: FilterConfig{BlockedCIDRs: []string{"10.1.0.0/16"}, CrowdSec: cs, CrowdSecMode: CrowdSecEnforce},
+			addr:   cleanIP,
+			want:   Allow,
+		},
+
+		// Country allowlist + CrowdSec enforce
+		{
+			name:   "allowed country + CrowdSec banned",
+			config: FilterConfig{AllowedCountries: []string{"US"}, CrowdSec: cs, CrowdSecMode: CrowdSecEnforce},
+			addr:   bannedIP,
+			want:   DenyCrowdSecBan,
+		},
+		{
+			name:   "country deny stops before CrowdSec",
+			config: FilterConfig{AllowedCountries: []string{"US"}, CrowdSec: cs, CrowdSecMode: CrowdSecEnforce},
+			addr:   outsideIP,
+			want:   DenyCountry,
+		},
+
+		// All three layers: CIDR allowlist + country blocklist + CrowdSec
+		{
+			name: "all layers: CIDR allow + country allow + CrowdSec ban",
+			config: FilterConfig{
+				AllowedCIDRs:     []string{"10.0.0.0/8"},
+				BlockedCountries: []string{"CN"},
+				CrowdSec:         cs,
+				CrowdSecMode:     CrowdSecEnforce,
+			},
+			addr: bannedIP, // 10.x (CIDR ok), US (country ok), banned (CrowdSec deny)
+			want: DenyCrowdSecBan,
+		},
+		{
+			name: "all layers: CIDR deny short-circuits everything",
+			config: FilterConfig{
+				AllowedCIDRs:     []string{"10.0.0.0/8"},
+				BlockedCountries: []string{"CN"},
+				CrowdSec:         cs,
+				CrowdSecMode:     CrowdSecEnforce,
+			},
+			addr: outsideIP, // 192.x (CIDR deny)
+			want: DenyCIDR,
+		},
+
+		// Observe mode: verdict returned but IsObserveOnly is true
+		{
+			name:   "observe mode: CrowdSec banned inside allowed CIDR",
+			config: FilterConfig{AllowedCIDRs: []string{"10.0.0.0/8"}, CrowdSec: cs, CrowdSecMode: CrowdSecObserve},
+			addr:   bannedIP,
+			want:   DenyCrowdSecBan, // verdict is ban, caller checks IsObserveOnly
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			f := ParseFilter(tc.config)
+			got := f.Check(netip.MustParseAddr(tc.addr), geo)
+			assert.Equal(t, tc.want, got)
+
+			// Verify observe mode flag when applicable.
+			if tc.config.CrowdSecMode == CrowdSecObserve && got.IsCrowdSec() {
+				assert.True(t, f.IsObserveOnly(got), "observe mode verdict should be observe-only")
+			}
+			if tc.config.CrowdSecMode == CrowdSecEnforce && got.IsCrowdSec() {
+				assert.False(t, f.IsObserveOnly(got), "enforce mode verdict should not be observe-only")
+			}
+		})
+	}
+}
+
+func TestFilter_CrowdSec_Enforce_NilChecker(t *testing.T) {
+	// LAPI not configured: checker is nil but mode is enforce. Must fail closed.
+	f := ParseFilter(FilterConfig{CrowdSec: nil, CrowdSecMode: CrowdSecEnforce})
+
+	assert.Equal(t, DenyCrowdSecUnavailable, f.Check(netip.MustParseAddr("1.2.3.4"), nil))
+}
+
+func TestFilter_CrowdSec_Observe_NilChecker(t *testing.T) {
+	// LAPI not configured: checker is nil but mode is observe. Must allow.
+	f := ParseFilter(FilterConfig{CrowdSec: nil, CrowdSecMode: CrowdSecObserve})
+
+	assert.Equal(t, Allow, f.Check(netip.MustParseAddr("1.2.3.4"), nil))
+}
+
+func TestFilter_HasRestrictions_CrowdSec(t *testing.T) {
+	cs := &mockCrowdSec{ready: true}
+	f := ParseFilter(FilterConfig{CrowdSec: cs, CrowdSecMode: CrowdSecEnforce})
+	assert.True(t, f.HasRestrictions())
+
+	// Enforce mode without checker (LAPI not configured): still has restrictions
+	// because Check() will fail-closed with DenyCrowdSecUnavailable.
+	f2 := ParseFilter(FilterConfig{CrowdSec: nil, CrowdSecMode: CrowdSecEnforce})
+	assert.True(t, f2.HasRestrictions())
+}

proxy/internal/tcp/router.go

@@ -479,9 +479,14 @@ func (r *Router) checkRestrictions(conn net.Conn, route Route) restrict.Verdict
 // On success (nil error), both conn and backend are closed by the relay.
 func (r *Router) relayTCP(ctx context.Context, conn net.Conn, sni SNIHost, route Route) error {
 	if verdict := r.checkRestrictions(conn, route); verdict != restrict.Allow {
-		r.logger.Debugf("connection from %s rejected by access restrictions: %s", conn.RemoteAddr(), verdict)
-		r.logL4Deny(route, conn, verdict)
-		return errAccessRestricted
+		if route.Filter != nil && route.Filter.IsObserveOnly(verdict) {
+			r.logger.Debugf("CrowdSec observe: would block %s for %s (%s)", conn.RemoteAddr(), sni, verdict)
+			r.logL4Deny(route, conn, verdict, true)
+		} else {
+			r.logger.Debugf("connection from %s rejected by access restrictions: %s", conn.RemoteAddr(), verdict)
+			r.logL4Deny(route, conn, verdict, false)
+			return errAccessRestricted
+		}
 	}
 
 	svcCtx, err := r.acquireRelay(ctx, route)
@@ -610,7 +615,7 @@ func (r *Router) logL4Entry(route Route, conn net.Conn, duration time.Duration,
 }
 
 // logL4Deny sends an access log entry for a denied connection.
-func (r *Router) logL4Deny(route Route, conn net.Conn, verdict restrict.Verdict) {
+func (r *Router) logL4Deny(route Route, conn net.Conn, verdict restrict.Verdict, observeOnly bool) {
 	r.mu.RLock()
 	al := r.accessLog
 	r.mu.RUnlock()
@@ -621,14 +626,22 @@ func (r *Router) logL4Deny(route Route, conn net.Conn, verdict restrict.Verdict)
 
 	sourceIP, _ := addrFromConn(conn)
 
-	al.LogL4(accesslog.L4Entry{
+	entry := accesslog.L4Entry{
 		AccountID:  route.AccountID,
 		ServiceID:  route.ServiceID,
 		Protocol:   route.Protocol,
 		Host:       route.Domain,
 		SourceIP:   sourceIP,
 		DenyReason: verdict.String(),
-	})
+	}
+	if verdict.IsCrowdSec() {
+		entry.Metadata = map[string]string{"crowdsec_verdict": verdict.String()}
+		if observeOnly {
+			entry.Metadata["crowdsec_mode"] = "observe"
+			entry.DenyReason = ""
+		}
+	}
+	al.LogL4(entry)
 }
 
 // getOrCreateServiceCtxLocked returns the context for a service, creating one

proxy/internal/tcp/router_test.go

@@ -1686,7 +1686,7 @@ func (f *fakeConn) RemoteAddr() net.Addr { return f.remote }
 
 func TestCheckRestrictions_UnparseableAddress(t *testing.T) {
 	router := NewPortRouter(log.StandardLogger(), nil)
-	filter := restrict.ParseFilter([]string{"10.0.0.0/8"}, nil, nil, nil)
+	filter := restrict.ParseFilter(restrict.FilterConfig{AllowedCIDRs: []string{"10.0.0.0/8"}})
 	route := Route{Filter: filter}
 
 	conn := &fakeConn{remote: fakeAddr("not-an-ip")}
@@ -1695,7 +1695,7 @@ func TestCheckRestrictions_UnparseableAddress(t *testing.T) {
 
 func TestCheckRestrictions_NilRemoteAddr(t *testing.T) {
 	router := NewPortRouter(log.StandardLogger(), nil)
-	filter := restrict.ParseFilter([]string{"10.0.0.0/8"}, nil, nil, nil)
+	filter := restrict.ParseFilter(restrict.FilterConfig{AllowedCIDRs: []string{"10.0.0.0/8"}})
 	route := Route{Filter: filter}
 
 	conn := &fakeConn{remote: nil}
@@ -1704,7 +1704,7 @@ func TestCheckRestrictions_NilRemoteAddr(t *testing.T) {
 
 func TestCheckRestrictions_AllowedAndDenied(t *testing.T) {
 	router := NewPortRouter(log.StandardLogger(), nil)
-	filter := restrict.ParseFilter([]string{"10.0.0.0/8"}, nil, nil, nil)
+	filter := restrict.ParseFilter(restrict.FilterConfig{AllowedCIDRs: []string{"10.0.0.0/8"}})
 	route := Route{Filter: filter}
 
 	allowed := &fakeConn{remote: &net.TCPAddr{IP: net.IPv4(10, 1, 2, 3), Port: 1234}}
@@ -1724,7 +1724,7 @@ func TestCheckRestrictions_NilFilter(t *testing.T) {
 
 func TestCheckRestrictions_IPv4MappedIPv6(t *testing.T) {
 	router := NewPortRouter(log.StandardLogger(), nil)
-	filter := restrict.ParseFilter([]string{"10.0.0.0/8"}, nil, nil, nil)
+	filter := restrict.ParseFilter(restrict.FilterConfig{AllowedCIDRs: []string{"10.0.0.0/8"}})
 	route := Route{Filter: filter}
 
 	// net.IPv4() returns a 16-byte v4-in-v6 representation internally.

proxy/internal/udp/relay.go

@@ -336,8 +336,13 @@ func (r *Relay) checkAccessRestrictions(addr net.Addr) error {
 		return fmt.Errorf("parse client address %s for restriction check: %w", addr, err)
 	}
 	if v := r.filter.Check(clientIP, r.geo); v != restrict.Allow {
-		r.logDeny(clientIP, v)
-		return fmt.Errorf("access restricted for %s", addr)
+		if r.filter.IsObserveOnly(v) {
+			r.logger.Debugf("CrowdSec observe: would block %s (%s)", clientIP, v)
+			r.logDeny(clientIP, v, true)
+		} else {
+			r.logDeny(clientIP, v, false)
+			return fmt.Errorf("access restricted for %s", addr)
+		}
 	}
 	return nil
 }
@@ -498,19 +503,27 @@ func (r *Relay) logSessionEnd(sess *session) {
 }
 
 // logDeny sends an access log entry for a denied UDP packet.
-func (r *Relay) logDeny(clientIP netip.Addr, verdict restrict.Verdict) {
+func (r *Relay) logDeny(clientIP netip.Addr, verdict restrict.Verdict, observeOnly bool) {
 	if r.accessLog == nil {
 		return
 	}
 
-	r.accessLog.LogL4(accesslog.L4Entry{
+	entry := accesslog.L4Entry{
 		AccountID:  r.accountID,
 		ServiceID:  r.serviceID,
 		Protocol:   accesslog.ProtocolUDP,
 		Host:       r.domain,
 		SourceIP:   clientIP,
 		DenyReason: verdict.String(),
-	})
+	}
+	if verdict.IsCrowdSec() {
+		entry.Metadata = map[string]string{"crowdsec_verdict": verdict.String()}
+		if observeOnly {
+			entry.Metadata["crowdsec_mode"] = "observe"
+			entry.DenyReason = ""
+		}
+	}
+	r.accessLog.LogL4(entry)
 }
 
 // Close stops the relay, waits for all session goroutines to exit,