Redirecting USB devices via a browser-based virtual desktop infrastructure application

1. A method, performed by a proxy of a virtual desktop infrastructure (VDI) application that executes within a browser on a client terminal, for redirecting a USB device that is connected to the client terminal to enable the USB device to be accessed in a remote session on a server, the method comprising:

receiving, by the proxy and from an agent that executes on the server, a first USB request block (URB);

evaluating contents of the first URB to determine a USB function that the first URB defines and a handle that defines a target of the USB function;

determining that the handle is associated with a browser-based representation of a first USB device that is connected to the client terminal; and

invoking a function of the browser-based representation of the first USB device, the function corresponding to the USB function defined in the first URB.

2. The method of claim 1 , further comprising:

obtaining, from the browser-based representation of the first USB device, data that was returned by the first USB device as a result of invoking the function of the browser-based representation of the first USB device;

generating a second URB that defines the USB function and the handle;

populating a payload of the second URB with the data; and

sending the second URB to the agent.

3. The method of claim 2 , wherein the first URB is received and the second URB is sent using the Web Socket protocol.

4. The method of claim 1 , wherein the handle is a pipe handle.

5. The method of claim 4 , wherein the USB function is a request to read data from or write data to the first USB device.

6. The method of claim 4 , wherein determining that the pipe handle is associated with the browser-based representation of the first USB device comprises accessing a data structure which defines mappings between pipe handles and endpoint numbers defined in the browser-based representation of the first USB device.

7. The method of claim 1 , wherein the handle is a device handle.

8. The method of claim 7 , wherein the USB function is a request to select a configuration of the first USB device.

9. The method of claim 7 , wherein determining that the device handle is associated with the browser-based representation of the first USB device comprises accessing a data structure which maps the device handle to the browser-based representation of the first USB device.

10. The method of claim 1 , wherein invoking the function of the browser-based representation of the first USB device comprises invoking a function of the WebUSB API.

11. The method of claim 1 , wherein the browser-based representation of the first USB device includes at least one configuration of the first USB device, at least one interface for each configuration and at least one endpoint for each interface, wherein the method further comprises:

creating and mapping a unique identifier to each endpoint included in the browser-based representation; and

employing the unique identifiers as pipe handles in URBs that are sent to the agent.

12. The method of claim 11 , further comprising:

creating and mapping a unique identifier to each interface and configuration;

employing each unique identifier that is mapped to an interface as an interface handle in URBs that are sent to the agent; and

employing each unique identifier that is mapped to a configuration as a configuration handle in URBs that are sent to the agent.

13. A method, performed by a proxy of a virtual desktop infrastructure (VDI) application that executes within a browser on a client terminal, for redirecting a USB device that is connected to the client terminal to enable the USB device to be accessed in a remote session on a server, the method comprising:

obtaining, from a browser-based representation of a first USB device that is connected to the client terminal, descriptors of the first USB device, the descriptors including a device descriptor, at least one configuration descriptor, at least one interface descriptor and at least one endpoint descriptor, each endpoint descriptor defining an endpoint of the first USB device;

creating a data structure that maps a unique identifier to each endpoint defined in the browser-based representation of the first USB device;

receiving, from an agent that executes on the server, a first USB request block (URB);

evaluating contents of the first URB to determine a USB function that the first URB defines and a pipe handle that defines an endpoint to which the USB function is directed;

accessing the data structure to determine that the pipe handle matches the unique identifier that is mapped to a first endpoint defined in in the browser-based representation of the first USB device; and

invoking a function of the browser-based representation of the first USB device, the function corresponding to the USB function defined in the first URB.

14. The method of claim 13 , further comprising:

sending each unique identifier to the agent to enable client drivers on the server to employ each unique identifier as a pipe handle in URBs.

15. The method of claim 14 , wherein sending each unique identifier to the agent comprises sending one or more URBs to the agent that include each unique identifier.

16. The method of claim 13 , wherein the data structure also maps unique identifiers to each interface and each configuration, wherein the method further comprises:

sending each unique identifier that is mapped to an interface and each unique identifier that is mapped to a configuration to the agent to enable client drivers on the server to employ the unique identifiers as interface handles and configuration handles respectively in URBs.

17. The method of claim 13 , wherein the browser-based representation of the first USB device is a USBDevice object provided by the WebUSB API.

18. The method of claim 13 , wherein the USB function defined in the first URB is a request to read data from the first USB device, wherein the method further comprises:

generating a second URB that defines the USB function and includes the pipe handle;

populating a payload of the second URB with data obtained from the invocation of the function of the browser-based representation of the first USB device; and

sending the second URB to the agent.

19. One or more computer storage media storing computer executable instructions which when executed in a browser on a client terminal implement a proxy of a virtual desktop infrastructure (VDI) application, the proxy being configured to perform a method for redirecting a USB device that is connected to the client terminal to enable the USB device to be accessed in a remote session on a server, the method comprising:

receiving, by the proxy and from an agent that executes on the server, a first USB request block (URB);

evaluating contents of the first URB to determine a USB function that the first URB defines;

determining that the first URB is associated with a browser-based representation of a first USB device that is connected to the client terminal;

invoking a function of the browser-based representation of the first USB device, the function corresponding to the USB function defined in the first URB; and

sending a second URB to the agent, the second URB including data obtained from the first USB device by invoking the function of the browser-based representation of the first USB device.

20. The computer storage media of claim 19 , wherein determining that the first URB is associated with the browser-based representation of the first USB device comprises determining that the first URB includes a handle that is mapped to an element of the browser-based representation of the first USB device.