fix: use atomic operations for concurrent counter access (#109)

- DHCP server: s.requestsTotal++ and s.offersTotal++ → atomic.AddUint64
- DHCP server: Stats() reads → atomic.LoadUint64 for all counters
- RADIUS coverage_test: handlerCalled bool → atomic.Bool in CoA tests

Fixes data races detected by -race flag in CI.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: mgazza

pkg/dhcp/server.go

@@ -295,7 +295,7 @@ func (s *Server) Start(ctx context.Context) error {
 
 // handleDHCP handles incoming DHCP packets (slow path)
 func (s *Server) handleDHCP(conn net.PacketConn, peer net.Addr, req *dhcpv4.DHCPv4) {
-	s.requestsTotal++
+	atomic.AddUint64(&s.requestsTotal, 1)
 
 	mac := req.ClientHWAddr.String()
 	msgType := req.MessageType()
@@ -508,7 +508,7 @@ func (s *Server) handleDiscover(req *dhcpv4.DHCPv4) (*dhcpv4.DHCPv4, error) {
 		return nil, fmt.Errorf("failed to build OFFER: %w", err)
 	}
 
-	s.offersTotal++
+	atomic.AddUint64(&s.offersTotal, 1)
 	return resp, nil
 }
 
@@ -1090,11 +1090,11 @@ func (s *Server) cleanupExpiredLeases() {
 // Stats returns DHCP server statistics
 func (s *Server) Stats() map[string]uint64 {
 	return map[string]uint64{
-		"requests_total": s.requestsTotal,
-		"offers_total":   s.offersTotal,
-		"acks_total":     s.acksTotal,
-		"naks_total":     s.naksTotal,
-		"releases_total": s.releasesTotal,
+		"requests_total": atomic.LoadUint64(&s.requestsTotal),
+		"offers_total":   atomic.LoadUint64(&s.offersTotal),
+		"acks_total":     atomic.LoadUint64(&s.acksTotal),
+		"naks_total":     atomic.LoadUint64(&s.naksTotal),
+		"releases_total": atomic.LoadUint64(&s.releasesTotal),
 	}
 }
 

pkg/radius/coverage_test.go

@@ -1730,9 +1730,9 @@ func TestCoAServer_HandleCoARequest_WithHandler(t *testing.T) {
 	}
 	defer srv.Stop()
 
-	handlerCalled := false
+	var handlerCalled atomic.Bool
 	srv.SetCoAHandler(func(ctx context.Context, req *CoARequest) *CoAResponse {
-		handlerCalled = true
+		handlerCalled.Store(true)
 		return &CoAResponse{Success: true, Message: "accepted"}
 	})
 
@@ -1741,7 +1741,7 @@ func TestCoAServer_HandleCoARequest_WithHandler(t *testing.T) {
 
 	time.Sleep(100 * time.Millisecond) // Allow time to process
 
-	if !handlerCalled {
+	if !handlerCalled.Load() {
 		t.Error("CoA handler was not called")
 	}
 
@@ -1795,17 +1795,17 @@ func TestCoAServer_HandleDisconnectRequest_WithHandler(t *testing.T) {
 	}
 	defer srv.Stop()
 
-	handlerCalled := false
+	var handlerCalled atomic.Bool
 	srv.SetDisconnectHandler(func(ctx context.Context, req *DisconnectRequest) *DisconnectResponse {
-		handlerCalled = true
+		handlerCalled.Store(true)
 		return &DisconnectResponse{Success: true, Message: "disconnected"}
 	})
 
 	sendCoAPacket(t, srv, CodeDisconnectRequest)
 
 	time.Sleep(100 * time.Millisecond)
 
-	if !handlerCalled {
+	if !handlerCalled.Load() {
 		t.Error("Disconnect handler was not called")
 	}