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+===============
+USB/IP protocol
+===============
+
+Architecture
+============
+
+The USB/IP protocol follows a server/client architecture. The server exports the
+USB devices and the clients import them. The device driver for the exported
+USB device runs on the client machine.
+
+The client may ask for the list of the exported USB devices. To get the list the
+client opens a TCP/IP connection to the server, and sends an OP_REQ_DEVLIST
+packet on top of the TCP/IP connection (so the actual OP_REQ_DEVLIST may be sent
+in one or more pieces at the low level transport layer). The server sends back
+the OP_REP_DEVLIST packet which lists the exported USB devices. Finally the
+TCP/IP connection is closed.
+
+::
+
+ virtual host controller usb host
+ "client" "server"
+ (imports USB devices) (exports USB devices)
+ | |
+ | OP_REQ_DEVLIST |
+ | ----------------------------------------------> |
+ | |
+ | OP_REP_DEVLIST |
+ | <---------------------------------------------- |
+ | |
+
+Once the client knows the list of exported USB devices it may decide to use one
+of them. First the client opens a TCP/IP connection to the server and
+sends an OP_REQ_IMPORT packet. The server replies with OP_REP_IMPORT. If the
+import was successful the TCP/IP connection remains open and will be used
+to transfer the URB traffic between the client and the server. The client may
+send two types of packets: the USBIP_CMD_SUBMIT to submit an URB, and
+USBIP_CMD_UNLINK to unlink a previously submitted URB. The answers of the
+server may be USBIP_RET_SUBMIT and USBIP_RET_UNLINK respectively.
+
+::
+
+ virtual host controller usb host
+ "client" "server"
+ (imports USB devices) (exports USB devices)
+ | |
+ | OP_REQ_IMPORT |
+ | ----------------------------------------------> |
+ | |
+ | OP_REP_IMPORT |
+ | <---------------------------------------------- |
+ | |
+ | |
+ | USBIP_CMD_SUBMIT(seqnum = n) |
+ | ----------------------------------------------> |
+ | |
+ | USBIP_RET_SUBMIT(seqnum = n) |
+ | <---------------------------------------------- |
+ | . |
+ | : |
+ | |
+ | USBIP_CMD_SUBMIT(seqnum = m) |
+ | ----------------------------------------------> |
+ | |
+ | USBIP_CMD_SUBMIT(seqnum = m+1) |
+ | ----------------------------------------------> |
+ | |
+ | USBIP_CMD_SUBMIT(seqnum = m+2) |
+ | ----------------------------------------------> |
+ | |
+ | USBIP_RET_SUBMIT(seqnum = m) |
+ | <---------------------------------------------- |
+ | |
+ | USBIP_CMD_SUBMIT(seqnum = m+3) |
+ | ----------------------------------------------> |
+ | |
+ | USBIP_RET_SUBMIT(seqnum = m+1) |
+ | <---------------------------------------------- |
+ | |
+ | USBIP_CMD_SUBMIT(seqnum = m+4) |
+ | ----------------------------------------------> |
+ | |
+ | USBIP_RET_SUBMIT(seqnum = m+2) |
+ | <---------------------------------------------- |
+ | . |
+ | : |
+
+For UNLINK, note that after a successful USBIP_RET_UNLINK, the unlinked URB
+submission would not have a corresponding USBIP_RET_SUBMIT (this is explained in
+function stub_recv_cmd_unlink of drivers/usb/usbip/stub_rx.c).
+
+::
+
+ virtual host controller usb host
+ "client" "server"
+ (imports USB devices) (exports USB devices)
+ | |
+ | USBIP_CMD_SUBMIT(seqnum = p) |
+ | ----------------------------------------------> |
+ | |
+ | USBIP_CMD_UNLINK |
+ | (seqnum = p+1, unlink_seqnum = p) |
+ | ----------------------------------------------> |
+ | |
+ | USBIP_RET_UNLINK |
+ | (seqnum = p+1, status = -ECONNRESET) |
+ | <---------------------------------------------- |
+ | |
+ | Note: No USBIP_RET_SUBMIT(seqnum = p) |
+ | <--X---X---X---X---X---X---X---X---X---X---X--- |
+ | . |
+ | : |
+ | |
+ | USBIP_CMD_SUBMIT(seqnum = q) |
+ | ----------------------------------------------> |
+ | |
+ | USBIP_RET_SUBMIT(seqnum = q) |
+ | <---------------------------------------------- |
+ | |
+ | USBIP_CMD_UNLINK |
+ | (seqnum = q+1, unlink_seqnum = q) |
+ | ----------------------------------------------> |
+ | |
+ | USBIP_RET_UNLINK |
+ | (seqnum = q+1, status = 0) |
+ | <---------------------------------------------- |
+ | |
+
+The fields are in network (big endian) byte order meaning that the most significant
+byte (MSB) is stored at the lowest address.
+
+Protocol Version
+================
+
+The documented USBIP version is v1.1.1. The binary representation of this
+version in message headers is 0x0111.
+
+This is defined in tools/usb/usbip/configure.ac
+
+Message Format
+==============
+
+OP_REQ_DEVLIST:
+ Retrieve the list of exported USB devices.
+
++-----------+--------+------------+---------------------------------------------------+
+| Offset | Length | Value | Description |
++===========+========+============+===================================================+
+| 0 | 2 | | USBIP version |
++-----------+--------+------------+---------------------------------------------------+
+| 2 | 2 | 0x8005 | Command code: Retrieve the list of exported USB |
+| | | | devices. |
++-----------+--------+------------+---------------------------------------------------+
+| 4 | 4 | 0x00000000 | Status: unused, shall be set to 0 |
++-----------+--------+------------+---------------------------------------------------+
+
+OP_REP_DEVLIST:
+ Reply with the list of exported USB devices.
+
++-----------+--------+------------+---------------------------------------------------+
+| Offset | Length | Value | Description |
++===========+========+============+===================================================+
+| 0 | 2 | | USBIP version |
++-----------+--------+------------+---------------------------------------------------+
+| 2 | 2 | 0x0005 | Reply code: The list of exported USB devices. |
++-----------+--------+------------+---------------------------------------------------+
+| 4 | 4 | 0x00000000 | Status: 0 for OK |
++-----------+--------+------------+---------------------------------------------------+
+| 8 | 4 | n | Number of exported devices: 0 means no exported |
+| | | | devices. |
++-----------+--------+------------+---------------------------------------------------+
+| 0x0C | | | From now on the exported n devices are described, |
+| | | | if any. If no devices are exported the message |
+| | | | ends with the previous "number of exported |
+| | | | devices" field. |
++-----------+--------+------------+---------------------------------------------------+
+| | 256 | | path: Path of the device on the host exporting the|
+| | | | USB device, string closed with zero byte, e.g. |
+| | | | "/sys/devices/pci0000:00/0000:00:1d.1/usb3/3-2" |
+| | | | The unused bytes shall be filled with zero |
+| | | | bytes. |
++-----------+--------+------------+---------------------------------------------------+
+| 0x10C | 32 | | busid: Bus ID of the exported device, string |
+| | | | closed with zero byte, e.g. "3-2". The unused |
+| | | | bytes shall be filled with zero bytes. |
++-----------+--------+------------+---------------------------------------------------+
+| 0x12C | 4 | | busnum |
++-----------+--------+------------+---------------------------------------------------+
+| 0x130 | 4 | | devnum |
++-----------+--------+------------+---------------------------------------------------+
+| 0x134 | 4 | | speed |
++-----------+--------+------------+---------------------------------------------------+
+| 0x138 | 2 | | idVendor |
++-----------+--------+------------+---------------------------------------------------+
+| 0x13A | 2 | | idProduct |
++-----------+--------+------------+---------------------------------------------------+
+| 0x13C | 2 | | bcdDevice |
++-----------+--------+------------+---------------------------------------------------+
+| 0x13E | 1 | | bDeviceClass |
++-----------+--------+------------+---------------------------------------------------+
+| 0x13F | 1 | | bDeviceSubClass |
++-----------+--------+------------+---------------------------------------------------+
+| 0x140 | 1 | | bDeviceProtocol |
++-----------+--------+------------+---------------------------------------------------+
+| 0x141 | 1 | | bConfigurationValue |
++-----------+--------+------------+---------------------------------------------------+
+| 0x142 | 1 | | bNumConfigurations |
++-----------+--------+------------+---------------------------------------------------+
+| 0x143 | 1 | | bNumInterfaces |
++-----------+--------+------------+---------------------------------------------------+
+| 0x144 | | m_0 | From now on each interface is described, all |
+| | | | together bNumInterfaces times, with the following |
+| | | | 4 fields: |
++-----------+--------+------------+---------------------------------------------------+
+| | 1 | | bInterfaceClass |
++-----------+--------+------------+---------------------------------------------------+
+| 0x145 | 1 | | bInterfaceSubClass |
++-----------+--------+------------+---------------------------------------------------+
+| 0x146 | 1 | | bInterfaceProtocol |
++-----------+--------+------------+---------------------------------------------------+
+| 0x147 | 1 | | padding byte for alignment, shall be set to zero |
++-----------+--------+------------+---------------------------------------------------+
+| 0xC + | | | The second exported USB device starts at i=1 |
+| i*0x138 + | | | with the path field. |
+| m_(i-1)*4 | | | |
++-----------+--------+------------+---------------------------------------------------+
+
+OP_REQ_IMPORT:
+ Request to import (attach) a remote USB device.
+
++-----------+--------+------------+---------------------------------------------------+
+| Offset | Length | Value | Description |
++===========+========+============+===================================================+
+| 0 | 2 | | USBIP version |
++-----------+--------+------------+---------------------------------------------------+
+| 2 | 2 | 0x8003 | Command code: import a remote USB device. |
++-----------+--------+------------+---------------------------------------------------+
+| 4 | 4 | 0x00000000 | Status: unused, shall be set to 0 |
++-----------+--------+------------+---------------------------------------------------+
+| 8 | 32 | | busid: the busid of the exported device on the |
+| | | | remote host. The possible values are taken |
+| | | | from the message field OP_REP_DEVLIST.busid. |
+| | | | A string closed with zero, the unused bytes |
+| | | | shall be filled with zeros. |
++-----------+--------+------------+---------------------------------------------------+
+
+OP_REP_IMPORT:
+ Reply to import (attach) a remote USB device.
+
++-----------+--------+------------+---------------------------------------------------+
+| Offset | Length | Value | Description |
++===========+========+============+===================================================+
+| 0 | 2 | | USBIP version |
++-----------+--------+------------+---------------------------------------------------+
+| 2 | 2 | 0x0003 | Reply code: Reply to import. |
++-----------+--------+------------+---------------------------------------------------+
+| 4 | 4 | 0x00000000 | Status: |
+| | | | |
+| | | | - 0 for OK |
+| | | | - 1 for error |
++-----------+--------+------------+---------------------------------------------------+
+| 8 | | | From now on comes the details of the imported |
+| | | | device, if the previous status field was OK (0), |
+| | | | otherwise the reply ends with the status field. |
++-----------+--------+------------+---------------------------------------------------+
+| | 256 | | path: Path of the device on the host exporting the|
+| | | | USB device, string closed with zero byte, e.g. |
+| | | | "/sys/devices/pci0000:00/0000:00:1d.1/usb3/3-2" |
+| | | | The unused bytes shall be filled with zero |
+| | | | bytes. |
++-----------+--------+------------+---------------------------------------------------+
+| 0x108 | 32 | | busid: Bus ID of the exported device, string |
+| | | | closed with zero byte, e.g. "3-2". The unused |
+| | | | bytes shall be filled with zero bytes. |
++-----------+--------+------------+---------------------------------------------------+
+| 0x128 | 4 | | busnum |
++-----------+--------+------------+---------------------------------------------------+
+| 0x12C | 4 | | devnum |
++-----------+--------+------------+---------------------------------------------------+
+| 0x130 | 4 | | speed |
++-----------+--------+------------+---------------------------------------------------+
+| 0x134 | 2 | | idVendor |
++-----------+--------+------------+---------------------------------------------------+
+| 0x136 | 2 | | idProduct |
++-----------+--------+------------+---------------------------------------------------+
+| 0x138 | 2 | | bcdDevice |
++-----------+--------+------------+---------------------------------------------------+
+| 0x139 | 1 | | bDeviceClass |
++-----------+--------+------------+---------------------------------------------------+
+| 0x13A | 1 | | bDeviceSubClass |
++-----------+--------+------------+---------------------------------------------------+
+| 0x13B | 1 | | bDeviceProtocol |
++-----------+--------+------------+---------------------------------------------------+
+| 0x13C | 1 | | bConfigurationValue |
++-----------+--------+------------+---------------------------------------------------+
+| 0x13D | 1 | | bNumConfigurations |
++-----------+--------+------------+---------------------------------------------------+
+| 0x13E | 1 | | bNumInterfaces |
++-----------+--------+------------+---------------------------------------------------+
+
+The following four commands have a common basic header called
+'usbip_header_basic', and their headers, called 'usbip_header' (before
+transfer_buffer payload), have the same length, therefore paddings are needed.
+
+usbip_header_basic:
+
++-----------+--------+---------------------------------------------------+
+| Offset | Length | Description |
++===========+========+===================================================+
+| 0 | 4 | command |
++-----------+--------+---------------------------------------------------+
+| 4 | 4 | seqnum: sequential number that identifies requests|
+| | | and corresponding responses; |
+| | | incremented per connection |
++-----------+--------+---------------------------------------------------+
+| 8 | 4 | devid: specifies a remote USB device uniquely |
+| | | instead of busnum and devnum; |
+| | | for client (request), this value is |
+| | | ((busnum << 16) | devnum); |
+| | | for server (response), this shall be set to 0 |
++-----------+--------+---------------------------------------------------+
+| 0xC | 4 | direction: |
+| | | |
+| | | - 0: USBIP_DIR_OUT |
+| | | - 1: USBIP_DIR_IN |
+| | | |
+| | | only used by client, for server this shall be 0 |
++-----------+--------+---------------------------------------------------+
+| 0x10 | 4 | ep: endpoint number |
+| | | only used by client, for server this shall be 0; |
+| | | for UNLINK, this shall be 0 |
++-----------+--------+---------------------------------------------------+
+
+USBIP_CMD_SUBMIT:
+ Submit an URB
+
++-----------+--------+---------------------------------------------------+
+| Offset | Length | Description |
++===========+========+===================================================+
+| 0 | 20 | usbip_header_basic, 'command' shall be 0x00000001 |
++-----------+--------+---------------------------------------------------+
+| 0x14 | 4 | transfer_flags: possible values depend on the |
+| | | USBIP_URB transfer_flags. |
+| | | Refer to include/uapi/linux/usbip.h and |
+| | | Documentation/driver-api/usb/URB.rst. |
+| | | Refer to usbip_pack_cmd_submit() and |
+| | | tweak_transfer_flags() in drivers/usb/usbip/ |
+| | | usbip_common.c. |
++-----------+--------+---------------------------------------------------+
+| 0x18 | 4 | transfer_buffer_length: |
+| | | use URB transfer_buffer_length |
++-----------+--------+---------------------------------------------------+
+| 0x1C | 4 | start_frame: use URB start_frame; |
+| | | initial frame for ISO transfer; |
+| | | shall be set to 0 if not ISO transfer |
++-----------+--------+---------------------------------------------------+
+| 0x20 | 4 | number_of_packets: number of ISO packets; |
+| | | shall be set to 0xffffffff if not ISO transfer |
++-----------+--------+---------------------------------------------------+
+| 0x24 | 4 | interval: maximum time for the request on the |
+| | | server-side host controller |
++-----------+--------+---------------------------------------------------+
+| 0x28 | 8 | setup: data bytes for USB setup, filled with |
+| | | zeros if not used. |
++-----------+--------+---------------------------------------------------+
+| 0x30 | n | transfer_buffer. |
+| | | If direction is USBIP_DIR_OUT then n equals |
+| | | transfer_buffer_length; otherwise n equals 0. |
+| | | For ISO transfers the padding between each ISO |
+| | | packets is not transmitted. |
++-----------+--------+---------------------------------------------------+
+| 0x30+n | m | iso_packet_descriptor |
++-----------+--------+---------------------------------------------------+
+
+USBIP_RET_SUBMIT:
+ Reply for submitting an URB
+
++-----------+--------+---------------------------------------------------+
+| Offset | Length | Description |
++===========+========+===================================================+
+| 0 | 20 | usbip_header_basic, 'command' shall be 0x00000003 |
++-----------+--------+---------------------------------------------------+
+| 0x14 | 4 | status: zero for successful URB transaction, |
+| | | otherwise some kind of error happened. |
++-----------+--------+---------------------------------------------------+
+| 0x18 | 4 | actual_length: number of URB data bytes; |
+| | | use URB actual_length |
++-----------+--------+---------------------------------------------------+
+| 0x1C | 4 | start_frame: use URB start_frame; |
+| | | initial frame for ISO transfer; |
+| | | shall be set to 0 if not ISO transfer |
++-----------+--------+---------------------------------------------------+
+| 0x20 | 4 | number_of_packets: number of ISO packets; |
+| | | shall be set to 0xffffffff if not ISO transfer |
++-----------+--------+---------------------------------------------------+
+| 0x24 | 4 | error_count |
++-----------+--------+---------------------------------------------------+
+| 0x28 | 8 | padding, shall be set to 0 |
++-----------+--------+---------------------------------------------------+
+| 0x30 | n | transfer_buffer. |
+| | | If direction is USBIP_DIR_IN then n equals |
+| | | actual_length; otherwise n equals 0. |
+| | | For ISO transfers the padding between each ISO |
+| | | packets is not transmitted. |
++-----------+--------+---------------------------------------------------+
+| 0x30+n | m | iso_packet_descriptor |
++-----------+--------+---------------------------------------------------+
+
+USBIP_CMD_UNLINK:
+ Unlink an URB
+
++-----------+--------+---------------------------------------------------+
+| Offset | Length | Description |
++===========+========+===================================================+
+| 0 | 20 | usbip_header_basic, 'command' shall be 0x00000002 |
++-----------+--------+---------------------------------------------------+
+| 0x14 | 4 | unlink_seqnum, of the SUBMIT request to unlink |
++-----------+--------+---------------------------------------------------+
+| 0x18 | 24 | padding, shall be set to 0 |
++-----------+--------+---------------------------------------------------+
+
+USBIP_RET_UNLINK:
+ Reply for URB unlink
+
++-----------+--------+---------------------------------------------------+
+| Offset | Length | Description |
++===========+========+===================================================+
+| 0 | 20 | usbip_header_basic, 'command' shall be 0x00000004 |
++-----------+--------+---------------------------------------------------+
+| 0x14 | 4 | status: This is similar to the status of |
+| | | USBIP_RET_SUBMIT (share the same memory offset). |
+| | | When UNLINK is successful, status is -ECONNRESET; |
+| | | when USBIP_CMD_UNLINK is after USBIP_RET_SUBMIT |
+| | | status is 0 |
++-----------+--------+---------------------------------------------------+
+| 0x18 | 24 | padding, shall be set to 0 |
++-----------+--------+---------------------------------------------------+
+
+EXAMPLE
+=======
+
+ The following data is captured from wire with Human Interface Devices (HID)
+ payload
+
+::
+
+ CmdIntrIN: 00000001 00000d05 0001000f 00000001 00000001 00000200 00000040 ffffffff 00000000 00000004 00000000 00000000
+ CmdIntrOUT: 00000001 00000d06 0001000f 00000000 00000001 00000000 00000040 ffffffff 00000000 00000004 00000000 00000000
+ ffffffff860008a784ce5ae212376300000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
+ RetIntrOut: 00000003 00000d06 00000000 00000000 00000000 00000000 00000040 ffffffff 00000000 00000000 00000000 00000000
+ RetIntrIn: 00000003 00000d05 00000000 00000000 00000000 00000000 00000040 ffffffff 00000000 00000000 00000000 00000000
+ ffffffff860011a784ce5ae2123763612891b1020100000400000000000000000000000000000000000000000000000000000000000000000000000000000000
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-18 00:43:21 +0000