From: Márton Németh <nm127@xxxxxxxxxxx> USBIP v1.0.0 protocol documentation. Signed-off-by: Márton Németh <nm127@xxxxxxxxxxx> --- Hi, I tried to document the USBIP protocol as implemented in the Linux kernel 3.0-rc2. The description is a preliminary draft only, it may contain mistakes. I tried to document what I have understand from the source code and from the actual captured network traffic when the USBIP is in action. Please review it, correct it, point out the missing parts. During I have documented the protocol a question came into my mind: why do we have two different type of package when the URB completition handler is called, namely USB_RET_SUBMIT and USBIP_RET_UNLINK? As far as I can see this causes race condition because for one URB the completition handler is only called once. If the one URB is sent in with USB_CMD_SUBMIT and then unlinked with USB_CMD_UNLINK the completition handler is called only once. In the protocol, however, we have two different type of packets: USB_RET_SUBMIT and USBIP_RET_UNLINK. The status field of these messages may contain anything in this case depending on the timing. Regards, Márton Németh --- diff -uprN staging-2.6.orig/drivers/staging/usbip/usbip_protocol.txt staging-2.6/drivers/staging/usbip/usbip_protocol.txt --- staging-2.6.orig/drivers/staging/usbip/usbip_protocol.txt 1970-01-01 01:00:00.000000000 +0100 +++ staging-2.6/drivers/staging/usbip/usbip_protocol.txt 2011-06-28 08:30:04.000000000 +0200 @@ -0,0 +1,352 @@ +PRELIMINARY DRAFT, MAY CONTAIN MISTAKES! +28 Jun 2011 + +The USB/IP protocol follows a server/client architecture. The server exports the +USB devices and the clients imports 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 towards 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 towards 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 trasfer 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) | + | <---------------------------------------------- | + | . | + | : | + | | + | USBIP_CMD_UNLINK | + | ----------------------------------------------> | + | | + | USBIP_RET_UNLINK | + | <---------------------------------------------- | + | | + +The fields are in network (big endian) byte order meaning that the most significant +byte (MSB) is stored at the lowest address. + + +OP_REQ_DEVLIST: Retrieve the list of exported USB devices. + + Offset | Length | Value | Meaning +-----------+--------+------------+--------------------------------------------------- + 0 | 2 | 0x0100 | Binary-coded decimal USBIP version number: v1.0.0 +-----------+--------+------------+--------------------------------------------------- + 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 | Meaning +-----------+--------+------------+--------------------------------------------------- + 0 | 2 | 0x0100 | Binary-coded decimal USBIP version number: v1.0.0. +-----------+--------+------------+--------------------------------------------------- + 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 + | | | 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 busid field. + m_(i-1)*4 | | | + +OP_REQ_IMPORT: Request to import (attach) a remote USB device. + + Offset | Length | Value | Meaning +-----------+--------+------------+--------------------------------------------------- + 0 | 2 | 0x0100 | Binary-coded decimal USBIP version number: v1.0.0 +-----------+--------+------------+--------------------------------------------------- + 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 | Meaning +-----------+--------+------------+--------------------------------------------------- + 0 | 2 | 0x0100 | Binary-coded decimal USBIP version number: v1.0.0 +-----------+--------+------------+--------------------------------------------------- + 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 + +USBIP_CMD_SUBMIT: Submit an URB + + Offset | Length | Value | Meaning +-----------+--------+------------+--------------------------------------------------- + 0 | 4 | 0x00000001 | command: Submit an URB +-----------+--------+------------+--------------------------------------------------- + 4 | 4 | | seqnum: the sequence number of the URB to submit +-----------+--------+------------+--------------------------------------------------- + 8 | 4 | | devid +-----------+--------+------------+--------------------------------------------------- + 0xC | 4 | | direction: 0: USBIP_DIR_IN + | | | 1: USBIP_DIR_OUT +-----------+--------+------------+--------------------------------------------------- + 0x10 | 4 | | ep: endpoint number, possible values are: 0...15 +-----------+--------+------------+--------------------------------------------------- + 0x14 | 4 | | transfer_flags: possible values depend on the + | | | URB transfer type, see below +-----------+--------+------------+--------------------------------------------------- + 0x18 | 4 | | transfer_buffer_length +-----------+--------+------------+--------------------------------------------------- + 0x1C | 4 | | start_frame: specify the selected frame to + | | | transmit an ISO frame, ignored if URB_ISO_ASAP + | | | is specified at transfer_flags +-----------+--------+------------+--------------------------------------------------- + 0x20 | 4 | | number_of_packets: number of ISO packets +-----------+--------+------------+--------------------------------------------------- + 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 | | | URB data. For ISO transfers the padding between + | | | each ISO packets is not transmitted. + + + Allowed transfer_flags | value | control | interrupt | bulk | isochronous + -------------------------+------------+---------+-----------+----------+------------- + URB_SHORT_NOT_OK | 0x00000001 | only in | only in | only in | no + URB_ISO_ASAP | 0x00000002 | no | no | no | yes + URB_NO_TRANSFER_DMA_MAP | 0x00000004 | yes | yes | yes | yes + URB_NO_FSBR | 0x00000020 | yes | no | no | no + URB_ZERO_PACKET | 0x00000040 | no | no | only out | no + URB_NO_INTERRUPT | 0x00000080 | yes | yes | yes | yes + URB_FREE_BUFFER | 0x00000100 | yes | yes | yes | yes + URB_DIR_MASK | 0x00000200 | yes | yes | yes | yes + + +USBIP_RET_SUBMIT: Reply for submitting an URB + + Offset | Length | Value | Meaning +-----------+--------+------------+--------------------------------------------------- + 0 | 4 | 0x00000002 | command +-----------+--------+------------+--------------------------------------------------- + 4 | 4 | | seqnum: URB sequence number +-----------+--------+------------+--------------------------------------------------- + 8 | 4 | | devid +-----------+--------+------------+--------------------------------------------------- + 0xC | 4 | | direction: 0: USBIP_DIR_IN + | | | 1: USBIP_DIR_OUT +-----------+--------+------------+--------------------------------------------------- + 0x10 | 4 | | ep: endpoint number +-----------+--------+------------+--------------------------------------------------- + 0x14 | 4 | | status: zero for successful URB transaction, + | | | otherwise some kind of error happened. +-----------+--------+------------+--------------------------------------------------- + 0x18 | 4 | n | actual_length: number of URB data bytes +-----------+--------+------------+--------------------------------------------------- + 0x1C | 4 | | start_frame: for an ISO frame the actually + | | | selected frame for transmit. +-----------+--------+------------+--------------------------------------------------- + 0x20 | 4 | | number_of_packets +-----------+--------+------------+--------------------------------------------------- + 0x24 | 4 | | error_count +-----------+--------+------------+--------------------------------------------------- + 0x28 | 8 | | setup: data bytes for USB setup, filled with + | | | zeros if not used +-----------+--------+------------+--------------------------------------------------- + 0x30 | n | | URB data bytes. For ISO transfers the padding + | | | between each ISO packets is not transmitted. + +USBIP_CMD_UNLINK: Unlink an URB + + Offset | Length | Value | Meaning +-----------+--------+------------+--------------------------------------------------- + 0 | 4 | 0x00000003 | command: URB unlink command +-----------+--------+------------+--------------------------------------------------- + 4 | 4 | | seqnum: URB sequence number to unlink: FIXME: is this so? +-----------+--------+------------+--------------------------------------------------- + 8 | 4 | | devid +-----------+--------+------------+--------------------------------------------------- + 0xC | 4 | | direction: 0: USBIP_DIR_IN + | | | 1: USBIP_DIR_OUT +-----------+--------+------------+--------------------------------------------------- + 0x10 | 4 | | ep: endpoint number: zero +-----------+--------+------------+--------------------------------------------------- + 0x14 | 4 | | seqnum: the URB sequence number given previously + | | | at USBIP_CMD_SUBMIT.seqnum field + +USBIP_RET_UNLINK: Reply for URB unlink + + Offset | Length | Value | Meaning +-----------+--------+------------+--------------------------------------------------- + 0 | 4 | 0x00000004 | command: reply for the URB unlink command +-----------+--------+------------+--------------------------------------------------- + 4 | 4 | | seqnum: the unlinked URB sequence number +-----------+--------+------------+--------------------------------------------------- + 8 | 4 | | devid +-----------+--------+------------+--------------------------------------------------- + 0xC | 4 | | direction: 0: USBIP_DIR_IN + | | | 1: USBIP_DIR_OUT +-----------+--------+------------+--------------------------------------------------- + 0x10 | 4 | | ep: endpoint number +-----------+--------+------------+--------------------------------------------------- + 0x14 | 4 | | status: This is the value contained in the + | | | urb->status in the URB completition handler. + | | | FIXME: a better explanation needed. -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
