Version 1.4 of the Linux VDA provides support for USB redirection. With this functionaliy, USB devices are shared among Citrix Receiver and the Linux VDA desktop. Once a USB device is redirected to the desktop, the user can use the USB device as if it were locally connected.
USB redirection includes three main areas of functionality:
Open source VHCI
This portion of the USB redirection feature develops a general USB device sharing system over an IP network. It consists of a Linux kernel driver and some user mode libraries, which allows you to communicate with the kernel driver to get all the USB data. In the Linux VDA implementation, Citrix reuses the kernel driver of VHCI, however all the USB data transfers between Linux VDA and Citrix Receiver are encapsulated in the Citrix ICA protocol package.
The VHCI service is an open source service provided by Citrix to communicate with VHCI kernel module. This service works as a gateway between VHCI and the Citrix USB service.
The USB service represents a Citrix module that manages all the virtualization and data transfers on the USB device.
This article contains the following sections:
Typically, if a USB device is redirected successfully to the Linux VDA client, one or more device nodes are created in the system /dev path. However, in some cases the redirected device cannot be used by an active Linux VDA session. USB devices rely on drivers to function properly (and some devices require special drivers), and in some cases drivers are not provided, which results in some redirected USB devices being inaccessible to an active Linux VDA session. When situations like these occur, the drivers must be installed and the system must be configured properly to ensure USB device connectivity.
With version 1.4, the Linux VDA supports a list of USB devices that are sucessfully redirected to the client. In addition, the device is properly mounted, especially the USB disk, allowing the user to access the disk without any additional configuration.
A Citrix policy controls whether USB device redirection is enabled or disabled. In addition, the type of device can also be specified using s DDC policy. When configuring USB redirection for the Linux VDA, the following must be configured:
In Citrix Studio, enable (or disable) USB device redirection to and from the client (for workstation hosts only).
In the Edit Setting dialog:
After enabling the USB redirection policy, set redirection rules using Citrix Studio by specifying which devices are allowed (or denied) on the Linux VDA client.
In the Client USB device redirection rules dialog:
To learn more about configuring generic USB redirection, refer to the Citrix Generic USB Redirection Configuration Guide.
Use the information in this section to troubleshoot various issues that you might encounter when using the Linux VDA.
No devices on the Receiver toolbar
In some cases, you might not be able to see devices listed on the Citrix Receiver toolbar, which indicates that no USB redirection is taking place. If this occurs, verify the following:
USB devices can be seen in the Receiver toolbar, but are labeled policy restricted, which results in failed redirection
This issue occurs because of the device's policy configuration. In such cases:
For more information, see How to Configure Automatic Redirection of USB Devices on the Citrix Support site.
A USB device is redirected successfully, but I cannot use it in my session
In most cases, only USB devices in the supported devices list can be redirected, however, in some cases other kinds of devices may be redirected into an active Linux VDA session. In these situations, for every redirected device, a node owned by the user is created in the system /dev path. However, it is the drivers and the configuration that determine whether the user can use the device successfully. If you find a device owned (plugged in) but inaccessible, add the device to an unrestricted policy.
In the case of USB drives, the Linux VDA configures and mounts the disk. The user (and only the owner who installed it) can access the disk without any additional configuration. This might not be the case for device that are not in the supoorted device list.
USB redirection depends on the VHCI kernel modules (usb-vhci-hcd.ko and usb-vhci-iocif.ko). These modules are part of the Linux VDA distribution (as part of the RPM package). They are compiled based on the official Linux distribution kernels and are noted in the table below:
|Supported Linux distribution||Kernel version|
If the kernel of your machine is not compatible with the driver built by Citrix for the Linux VDA, the USB service may fail to start. In this case you cannot use the USB redirection feature unless you build your own VHCI kernel modules.
On the command line, execute the following command to verify if the kernel is consistent:
If the command executes successfully, it means that the kernel module has loaded successfully and that the version is consistent with the one installed by Citrix.
If the command executes with errors, it means that the kernel is inconsistent with the Citrix module and must be rebuilt.
If the kernel module is inconsistent with the Citrix version, perform the following:
1. Build the VHCI kernel module. Download the VHCI source code from the project page.
2. Build the kernel module based on the header files and the Module.symvers file. Use the following steps to install the kernel header files and create Module.symvers based on the appropriate Linux distribution:
yum install kernel-devel
yum install kernel-headers
zypper install kernel-devel
zypper install kernel-source
zypper install kernel-source
If the installation is successful, there will be a kernel folder resembling:
3. In the folder (/usr/src/kernels/3.10.0-327.10.1.el7.x86_64) verify that the file Module.symvers is present. If this file is not in the directory, you must build the kernel to get this file (e.g., make oldconfig; make prepare;make modules;make) or copy it from /usr/src/kernels/3.10.0-327.10.1.el7.x86_64-obj/x86_64/defaults/module.*
4. vhci-hcd-1.15/Makefile, change the Makefile of VCHI, set KDIR to the kernel directory:
#KDIR = $(BUILD_PREFIX)/lib/modules/$(KVERSION)/build
KDIR = usr/src/kernels/3.10.0-327.10.1.el7.x86_64
5. cd vhci-hcd-1.15/ and make; build the VHCI kernel.
If the build was successful, usb-vhci-hcd.ko and usb-vhci-iocifc.ko are created in the vhci-hcd-1.15/directory.
6. Replace the kernel module with the newly built one: cp -f usb-vhci-*.ko /opt/Citrix/VDA/lib64/
7. Restart the USB service: service ctxusbsd restart
8. Log off and log on to the the session again. Check to see if USB redirection is functioning.
This issue occurs because when you write data to a file system, the system mounts the memory cache in the file system, the data is not actually written to the disk itself. If you stop redirecting using the Receiver toolbar, there is no time remaining for the data being flushed into the disk, which results in lost data.
To resolve this issue, whenever you write data into the disk, use the sync command in a terminal to flush data into the disk, then stop USB redirection.
The following devices have been verified to work with this version of the Linux VDA. Other devices may be freely used, with unexpected results:
|USB mass storage device||VID:PID||File system|
|Netac Technology Co., Ltd||0dd8:173c||FAT32|
|Kingston Datatraveler 101 II||0951:1625||FAT32|
|Kingston Datatraveler GT101 G2||1567:8902||FAT32|
|SanDisk SDCZ80 flash drive||0781:5580||FAT32|
|SanDisk Cruzer 16GB||1058:10B8||FAT32|
|USB 3D mouse||VID:PID|
|3DConnexion SpaceMouse Pro||046d: c62b|
|Epson Perfection V330 photo||04B8: 0142|