1=============== 2USB/IP protocol 3=============== 4 5Architecture 6============ 7 8The USB/IP protocol follows a server/client architecture. The server exports the 9USB devices and the clients import them. The device driver for the exported 10USB device runs on the client machine. 11 12The client may ask for the list of the exported USB devices. To get the list the 13client opens a TCP/IP connection to the server, and sends an OP_REQ_DEVLIST 14packet on top of the TCP/IP connection (so the actual OP_REQ_DEVLIST may be sent 15in one or more pieces at the low level transport layer). The server sends back 16the OP_REP_DEVLIST packet which lists the exported USB devices. Finally the 17TCP/IP connection is closed. 18 19:: 20 21 virtual host controller usb host 22 "client" "server" 23 (imports USB devices) (exports USB devices) 24 | | 25 | OP_REQ_DEVLIST | 26 | ----------------------------------------------> | 27 | | 28 | OP_REP_DEVLIST | 29 | <---------------------------------------------- | 30 | | 31 32Once the client knows the list of exported USB devices it may decide to use one 33of them. First the client opens a TCP/IP connection to the server and 34sends an OP_REQ_IMPORT packet. The server replies with OP_REP_IMPORT. If the 35import was successful the TCP/IP connection remains open and will be used 36to transfer the URB traffic between the client and the server. The client may 37send two types of packets: the USBIP_CMD_SUBMIT to submit an URB, and 38USBIP_CMD_UNLINK to unlink a previously submitted URB. The answers of the 39server may be USBIP_RET_SUBMIT and USBIP_RET_UNLINK respectively. 40 41:: 42 43 virtual host controller usb host 44 "client" "server" 45 (imports USB devices) (exports USB devices) 46 | | 47 | OP_REQ_IMPORT | 48 | ----------------------------------------------> | 49 | | 50 | OP_REP_IMPORT | 51 | <---------------------------------------------- | 52 | | 53 | | 54 | USBIP_CMD_SUBMIT(seqnum = n) | 55 | ----------------------------------------------> | 56 | | 57 | USBIP_RET_SUBMIT(seqnum = n) | 58 | <---------------------------------------------- | 59 | . | 60 | : | 61 | | 62 | USBIP_CMD_SUBMIT(seqnum = m) | 63 | ----------------------------------------------> | 64 | | 65 | USBIP_CMD_SUBMIT(seqnum = m+1) | 66 | ----------------------------------------------> | 67 | | 68 | USBIP_CMD_SUBMIT(seqnum = m+2) | 69 | ----------------------------------------------> | 70 | | 71 | USBIP_RET_SUBMIT(seqnum = m) | 72 | <---------------------------------------------- | 73 | | 74 | USBIP_CMD_SUBMIT(seqnum = m+3) | 75 | ----------------------------------------------> | 76 | | 77 | USBIP_RET_SUBMIT(seqnum = m+1) | 78 | <---------------------------------------------- | 79 | | 80 | USBIP_CMD_SUBMIT(seqnum = m+4) | 81 | ----------------------------------------------> | 82 | | 83 | USBIP_RET_SUBMIT(seqnum = m+2) | 84 | <---------------------------------------------- | 85 | . | 86 | : | 87 88For UNLINK, note that after a successful USBIP_RET_UNLINK, the unlinked URB 89submission would not have a corresponding USBIP_RET_SUBMIT (this is explained in 90function stub_recv_cmd_unlink of drivers/usb/usbip/stub_rx.c). 91 92:: 93 94 virtual host controller usb host 95 "client" "server" 96 (imports USB devices) (exports USB devices) 97 | | 98 | USBIP_CMD_SUBMIT(seqnum = p) | 99 | ----------------------------------------------> | 100 | | 101 | USBIP_CMD_UNLINK | 102 | (seqnum = p+1, unlink_seqnum = p) | 103 | ----------------------------------------------> | 104 | | 105 | USBIP_RET_UNLINK | 106 | (seqnum = p+1, status = -ECONNRESET) | 107 | <---------------------------------------------- | 108 | | 109 | Note: No USBIP_RET_SUBMIT(seqnum = p) | 110 | <--X---X---X---X---X---X---X---X---X---X---X--- | 111 | . | 112 | : | 113 | | 114 | USBIP_CMD_SUBMIT(seqnum = q) | 115 | ----------------------------------------------> | 116 | | 117 | USBIP_RET_SUBMIT(seqnum = q) | 118 | <---------------------------------------------- | 119 | | 120 | USBIP_CMD_UNLINK | 121 | (seqnum = q+1, unlink_seqnum = q) | 122 | ----------------------------------------------> | 123 | | 124 | USBIP_RET_UNLINK | 125 | (seqnum = q+1, status = 0) | 126 | <---------------------------------------------- | 127 | | 128 129The fields are in network (big endian) byte order meaning that the most significant 130byte (MSB) is stored at the lowest address. 131 132Protocol Version 133================ 134 135The documented USBIP version is v1.1.1. The binary representation of this 136version in message headers is 0x0111. 137 138This is defined in tools/usb/usbip/configure.ac 139 140Message Format 141============== 142 143OP_REQ_DEVLIST: 144 Retrieve the list of exported USB devices. 145 146+-----------+--------+------------+---------------------------------------------------+ 147| Offset | Length | Value | Description | 148+===========+========+============+===================================================+ 149| 0 | 2 | | USBIP version | 150+-----------+--------+------------+---------------------------------------------------+ 151| 2 | 2 | 0x8005 | Command code: Retrieve the list of exported USB | 152| | | | devices. | 153+-----------+--------+------------+---------------------------------------------------+ 154| 4 | 4 | 0x00000000 | Status: unused, shall be set to 0 | 155+-----------+--------+------------+---------------------------------------------------+ 156 157OP_REP_DEVLIST: 158 Reply with the list of exported USB devices. 159 160+-----------+--------+------------+---------------------------------------------------+ 161| Offset | Length | Value | Description | 162+===========+========+============+===================================================+ 163| 0 | 2 | | USBIP version | 164+-----------+--------+------------+---------------------------------------------------+ 165| 2 | 2 | 0x0005 | Reply code: The list of exported USB devices. | 166+-----------+--------+------------+---------------------------------------------------+ 167| 4 | 4 | 0x00000000 | Status: 0 for OK | 168+-----------+--------+------------+---------------------------------------------------+ 169| 8 | 4 | n | Number of exported devices: 0 means no exported | 170| | | | devices. | 171+-----------+--------+------------+---------------------------------------------------+ 172| 0x0C | | | From now on the exported n devices are described, | 173| | | | if any. If no devices are exported the message | 174| | | | ends with the previous "number of exported | 175| | | | devices" field. | 176+-----------+--------+------------+---------------------------------------------------+ 177| | 256 | | path: Path of the device on the host exporting the| 178| | | | USB device, string closed with zero byte, e.g. | 179| | | | "/sys/devices/pci0000:00/0000:00:1d.1/usb3/3-2" | 180| | | | The unused bytes shall be filled with zero | 181| | | | bytes. | 182+-----------+--------+------------+---------------------------------------------------+ 183| 0x10C | 32 | | busid: Bus ID of the exported device, string | 184| | | | closed with zero byte, e.g. "3-2". The unused | 185| | | | bytes shall be filled with zero bytes. | 186+-----------+--------+------------+---------------------------------------------------+ 187| 0x12C | 4 | | busnum | 188+-----------+--------+------------+---------------------------------------------------+ 189| 0x130 | 4 | | devnum | 190+-----------+--------+------------+---------------------------------------------------+ 191| 0x134 | 4 | | speed | 192+-----------+--------+------------+---------------------------------------------------+ 193| 0x138 | 2 | | idVendor | 194+-----------+--------+------------+---------------------------------------------------+ 195| 0x13A | 2 | | idProduct | 196+-----------+--------+------------+---------------------------------------------------+ 197| 0x13C | 2 | | bcdDevice | 198+-----------+--------+------------+---------------------------------------------------+ 199| 0x13E | 1 | | bDeviceClass | 200+-----------+--------+------------+---------------------------------------------------+ 201| 0x13F | 1 | | bDeviceSubClass | 202+-----------+--------+------------+---------------------------------------------------+ 203| 0x140 | 1 | | bDeviceProtocol | 204+-----------+--------+------------+---------------------------------------------------+ 205| 0x141 | 1 | | bConfigurationValue | 206+-----------+--------+------------+---------------------------------------------------+ 207| 0x142 | 1 | | bNumConfigurations | 208+-----------+--------+------------+---------------------------------------------------+ 209| 0x143 | 1 | | bNumInterfaces | 210+-----------+--------+------------+---------------------------------------------------+ 211| 0x144 | | m_0 | From now on each interface is described, all | 212| | | | together bNumInterfaces times, with the following | 213| | | | 4 fields: | 214+-----------+--------+------------+---------------------------------------------------+ 215| | 1 | | bInterfaceClass | 216+-----------+--------+------------+---------------------------------------------------+ 217| 0x145 | 1 | | bInterfaceSubClass | 218+-----------+--------+------------+---------------------------------------------------+ 219| 0x146 | 1 | | bInterfaceProtocol | 220+-----------+--------+------------+---------------------------------------------------+ 221| 0x147 | 1 | | padding byte for alignment, shall be set to zero | 222+-----------+--------+------------+---------------------------------------------------+ 223| 0xC + | | | The second exported USB device starts at i=1 | 224| i*0x138 + | | | with the path field. | 225| m_(i-1)*4 | | | | 226+-----------+--------+------------+---------------------------------------------------+ 227 228OP_REQ_IMPORT: 229 Request to import (attach) a remote USB device. 230 231+-----------+--------+------------+---------------------------------------------------+ 232| Offset | Length | Value | Description | 233+===========+========+============+===================================================+ 234| 0 | 2 | | USBIP version | 235+-----------+--------+------------+---------------------------------------------------+ 236| 2 | 2 | 0x8003 | Command code: import a remote USB device. | 237+-----------+--------+------------+---------------------------------------------------+ 238| 4 | 4 | 0x00000000 | Status: unused, shall be set to 0 | 239+-----------+--------+------------+---------------------------------------------------+ 240| 8 | 32 | | busid: the busid of the exported device on the | 241| | | | remote host. The possible values are taken | 242| | | | from the message field OP_REP_DEVLIST.busid. | 243| | | | A string closed with zero, the unused bytes | 244| | | | shall be filled with zeros. | 245+-----------+--------+------------+---------------------------------------------------+ 246 247OP_REP_IMPORT: 248 Reply to import (attach) a remote USB device. 249 250+-----------+--------+------------+---------------------------------------------------+ 251| Offset | Length | Value | Description | 252+===========+========+============+===================================================+ 253| 0 | 2 | | USBIP version | 254+-----------+--------+------------+---------------------------------------------------+ 255| 2 | 2 | 0x0003 | Reply code: Reply to import. | 256+-----------+--------+------------+---------------------------------------------------+ 257| 4 | 4 | 0x00000000 | Status: | 258| | | | | 259| | | | - 0 for OK | 260| | | | - 1 for error | 261+-----------+--------+------------+---------------------------------------------------+ 262| 8 | | | From now on comes the details of the imported | 263| | | | device, if the previous status field was OK (0), | 264| | | | otherwise the reply ends with the status field. | 265+-----------+--------+------------+---------------------------------------------------+ 266| | 256 | | path: Path of the device on the host exporting the| 267| | | | USB device, string closed with zero byte, e.g. | 268| | | | "/sys/devices/pci0000:00/0000:00:1d.1/usb3/3-2" | 269| | | | The unused bytes shall be filled with zero | 270| | | | bytes. | 271+-----------+--------+------------+---------------------------------------------------+ 272| 0x108 | 32 | | busid: Bus ID of the exported device, string | 273| | | | closed with zero byte, e.g. "3-2". The unused | 274| | | | bytes shall be filled with zero bytes. | 275+-----------+--------+------------+---------------------------------------------------+ 276| 0x128 | 4 | | busnum | 277+-----------+--------+------------+---------------------------------------------------+ 278| 0x12C | 4 | | devnum | 279+-----------+--------+------------+---------------------------------------------------+ 280| 0x130 | 4 | | speed | 281+-----------+--------+------------+---------------------------------------------------+ 282| 0x134 | 2 | | idVendor | 283+-----------+--------+------------+---------------------------------------------------+ 284| 0x136 | 2 | | idProduct | 285+-----------+--------+------------+---------------------------------------------------+ 286| 0x138 | 2 | | bcdDevice | 287+-----------+--------+------------+---------------------------------------------------+ 288| 0x139 | 1 | | bDeviceClass | 289+-----------+--------+------------+---------------------------------------------------+ 290| 0x13A | 1 | | bDeviceSubClass | 291+-----------+--------+------------+---------------------------------------------------+ 292| 0x13B | 1 | | bDeviceProtocol | 293+-----------+--------+------------+---------------------------------------------------+ 294| 0x13C | 1 | | bConfigurationValue | 295+-----------+--------+------------+---------------------------------------------------+ 296| 0x13D | 1 | | bNumConfigurations | 297+-----------+--------+------------+---------------------------------------------------+ 298| 0x13E | 1 | | bNumInterfaces | 299+-----------+--------+------------+---------------------------------------------------+ 300 301The following four commands have a common basic header called 302'usbip_header_basic', and their headers, called 'usbip_header' (before 303transfer_buffer payload), have the same length, therefore paddings are needed. 304 305usbip_header_basic: 306 307+-----------+--------+---------------------------------------------------+ 308| Offset | Length | Description | 309+===========+========+===================================================+ 310| 0 | 4 | command | 311+-----------+--------+---------------------------------------------------+ 312| 4 | 4 | seqnum: sequential number that identifies requests| 313| | | and corresponding responses; | 314| | | incremented per connection | 315+-----------+--------+---------------------------------------------------+ 316| 8 | 4 | devid: specifies a remote USB device uniquely | 317| | | instead of busnum and devnum; | 318| | | for client (request), this value is | 319| | | ((busnum << 16) | devnum); | 320| | | for server (response), this shall be set to 0 | 321+-----------+--------+---------------------------------------------------+ 322| 0xC | 4 | direction: | 323| | | | 324| | | - 0: USBIP_DIR_OUT | 325| | | - 1: USBIP_DIR_IN | 326| | | | 327| | | only used by client, for server this shall be 0 | 328+-----------+--------+---------------------------------------------------+ 329| 0x10 | 4 | ep: endpoint number | 330| | | only used by client, for server this shall be 0; | 331| | | for UNLINK, this shall be 0 | 332+-----------+--------+---------------------------------------------------+ 333 334USBIP_CMD_SUBMIT: 335 Submit an URB 336 337+-----------+--------+---------------------------------------------------+ 338| Offset | Length | Description | 339+===========+========+===================================================+ 340| 0 | 20 | usbip_header_basic, 'command' shall be 0x00000001 | 341+-----------+--------+---------------------------------------------------+ 342| 0x14 | 4 | transfer_flags: possible values depend on the | 343| | | USBIP_URB transfer_flags. | 344| | | Refer to include/uapi/linux/usbip.h and | 345| | | Documentation/driver-api/usb/URB.rst. | 346| | | Refer to usbip_pack_cmd_submit() and | 347| | | tweak_transfer_flags() in drivers/usb/usbip/ | 348| | | usbip_common.c. | 349+-----------+--------+---------------------------------------------------+ 350| 0x18 | 4 | transfer_buffer_length: | 351| | | use URB transfer_buffer_length | 352+-----------+--------+---------------------------------------------------+ 353| 0x1C | 4 | start_frame: use URB start_frame; | 354| | | initial frame for ISO transfer; | 355| | | shall be set to 0 if not ISO transfer | 356+-----------+--------+---------------------------------------------------+ 357| 0x20 | 4 | number_of_packets: number of ISO packets; | 358| | | shall be set to 0xffffffff if not ISO transfer | 359+-----------+--------+---------------------------------------------------+ 360| 0x24 | 4 | interval: maximum time for the request on the | 361| | | server-side host controller | 362+-----------+--------+---------------------------------------------------+ 363| 0x28 | 8 | setup: data bytes for USB setup, filled with | 364| | | zeros if not used. | 365+-----------+--------+---------------------------------------------------+ 366| 0x30 | n | transfer_buffer. | 367| | | If direction is USBIP_DIR_OUT then n equals | 368| | | transfer_buffer_length; otherwise n equals 0. | 369| | | For ISO transfers the padding between each ISO | 370| | | packets is not transmitted. | 371+-----------+--------+---------------------------------------------------+ 372| 0x30+n | m | iso_packet_descriptor | 373+-----------+--------+---------------------------------------------------+ 374 375USBIP_RET_SUBMIT: 376 Reply for submitting an URB 377 378+-----------+--------+---------------------------------------------------+ 379| Offset | Length | Description | 380+===========+========+===================================================+ 381| 0 | 20 | usbip_header_basic, 'command' shall be 0x00000003 | 382+-----------+--------+---------------------------------------------------+ 383| 0x14 | 4 | status: zero for successful URB transaction, | 384| | | otherwise some kind of error happened. | 385+-----------+--------+---------------------------------------------------+ 386| 0x18 | 4 | actual_length: number of URB data bytes; | 387| | | use URB actual_length | 388+-----------+--------+---------------------------------------------------+ 389| 0x1C | 4 | start_frame: use URB start_frame; | 390| | | initial frame for ISO transfer; | 391| | | shall be set to 0 if not ISO transfer | 392+-----------+--------+---------------------------------------------------+ 393| 0x20 | 4 | number_of_packets: number of ISO packets; | 394| | | shall be set to 0xffffffff if not ISO transfer | 395+-----------+--------+---------------------------------------------------+ 396| 0x24 | 4 | error_count | 397+-----------+--------+---------------------------------------------------+ 398| 0x28 | 8 | padding, shall be set to 0 | 399+-----------+--------+---------------------------------------------------+ 400| 0x30 | n | transfer_buffer. | 401| | | If direction is USBIP_DIR_IN then n equals | 402| | | actual_length; otherwise n equals 0. | 403| | | For ISO transfers the padding between each ISO | 404| | | packets is not transmitted. | 405+-----------+--------+---------------------------------------------------+ 406| 0x30+n | m | iso_packet_descriptor | 407+-----------+--------+---------------------------------------------------+ 408 409USBIP_CMD_UNLINK: 410 Unlink an URB 411 412+-----------+--------+---------------------------------------------------+ 413| Offset | Length | Description | 414+===========+========+===================================================+ 415| 0 | 20 | usbip_header_basic, 'command' shall be 0x00000002 | 416+-----------+--------+---------------------------------------------------+ 417| 0x14 | 4 | unlink_seqnum, of the SUBMIT request to unlink | 418+-----------+--------+---------------------------------------------------+ 419| 0x18 | 24 | padding, shall be set to 0 | 420+-----------+--------+---------------------------------------------------+ 421 422USBIP_RET_UNLINK: 423 Reply for URB unlink 424 425+-----------+--------+---------------------------------------------------+ 426| Offset | Length | Description | 427+===========+========+===================================================+ 428| 0 | 20 | usbip_header_basic, 'command' shall be 0x00000004 | 429+-----------+--------+---------------------------------------------------+ 430| 0x14 | 4 | status: This is similar to the status of | 431| | | USBIP_RET_SUBMIT (share the same memory offset). | 432| | | When UNLINK is successful, status is -ECONNRESET; | 433| | | when USBIP_CMD_UNLINK is after USBIP_RET_SUBMIT | 434| | | status is 0 | 435+-----------+--------+---------------------------------------------------+ 436| 0x18 | 24 | padding, shall be set to 0 | 437+-----------+--------+---------------------------------------------------+ 438 439EXAMPLE 440======= 441 442 The following data is captured from wire with Human Interface Devices (HID) 443 payload 444 445:: 446 447 CmdIntrIN: 00000001 00000d05 0001000f 00000001 00000001 00000200 00000040 ffffffff 00000000 00000004 00000000 00000000 448 CmdIntrOUT: 00000001 00000d06 0001000f 00000000 00000001 00000000 00000040 ffffffff 00000000 00000004 00000000 00000000 449 ffffffff860008a784ce5ae212376300000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000 450 RetIntrOut: 00000003 00000d06 00000000 00000000 00000000 00000000 00000040 ffffffff 00000000 00000000 00000000 00000000 451 RetIntrIn: 00000003 00000d05 00000000 00000000 00000000 00000000 00000040 ffffffff 00000000 00000000 00000000 00000000 452 ffffffff860011a784ce5ae2123763612891b1020100000400000000000000000000000000000000000000000000000000000000000000000000000000000000 453