fix USBDEVFS_DISCONNECT_CLAIM

internal/usbip/server.go

@@ -51,19 +51,36 @@ func (s *Server) Attach() error {
 	}
 	s.handle = handle
 
-	// Disconnect kernel drivers from all interfaces
+	// For each interface: disconnect kernel driver and claim it
 	for _, iface := range s.device.Interfaces {
-		if iface.Driver != "" && iface.Driver != "(none)" {
-			// Try to disconnect - ignore errors for already-disconnected interfaces
-			handle.DisconnectDriver()
-		}
-	}
+		ifnum := uint32(iface.Number)
 
-	// Claim all interfaces
-	for _, iface := range s.device.Interfaces {
-		if err := handle.ClaimInterface(uint32(iface.Number)); err != nil {
-			log.Printf("[usbip-server] warning: could not claim interface %d: %v", iface.Number, err)
+		// Try atomic disconnect+claim first (USBDEVFS_DISCONNECT_CLAIM, Linux 3.7+)
+		err := handle.DisconnectClaimInterface(ifnum)
+		if err == nil {
+			log.Printf("[usbip-server] interface %d: disconnect+claim OK", ifnum)
+			continue
 		}
+
+		// Fallback: disconnect driver per interface, then claim
+		if disconnErr := handle.DisconnectDriverForInterface(ifnum); disconnErr != nil {
+			log.Printf("[usbip-server] interface %d: disconnect warning: %v", ifnum, disconnErr)
+		}
+
+		if claimErr := handle.ClaimInterface(ifnum); claimErr != nil {
+			log.Printf("[usbip-server] error: could not claim interface %d: %v", ifnum, claimErr)
+			// This is a critical error - clean up and fail
+			for _, prev := range s.device.Interfaces {
+				if uint32(prev.Number) < ifnum {
+					handle.ReleaseInterface(uint32(prev.Number))
+				}
+			}
+			handle.ConnectDriver()
+			handle.Close()
+			s.handle = nil
+			return fmt.Errorf("claiming interface %d: %w", ifnum, claimErr)
+		}
+		log.Printf("[usbip-server] interface %d: fallback disconnect+claim OK", ifnum)
 	}
 
 	return nil