Dear USB Linux Mailing List. I have been trying to write a USB IP Virtual Device as your protocol (https://docs.kernel.org/usb/usbip_protocol.html). Currently I am in the step of writing the code that responds to the OP_REQ_IMPORT package, I have been writing the code accordingly to the, previously mentioned, documentation, https://docs.kernel.org/usb/usbip_protocol.html, and some USB resources https://www.usb.org/defined-class-codes. When attaching my USB IP Virtual Device as here `sudo usbip --debug --tcp-port 3000 attach --remote=localhost -d 2-2` I get the following error ``` usbip: debug: usbip_network.c:28:[usbip_setup_port_number] parsing port arg '3000' usbip: info: using port 3000 ("3000") usbip: debug: usbip.c:129:[run_command] running command: `attach' libusbip: debug: vhci_driver.c:269:[usbip_vhci_driver_open] available ports: 16 libusbip: debug: vhci_driver.c:281:[usbip_vhci_driver_open] available controllers: 1 libusbip: debug: vhci_driver.c:128:[refresh_imported_device_list] controller 0 libusbip: debug: vhci_driver.c:67:[parse_status] hub hs port 0 status 4 speed 0 devid 0 libusbip: debug: vhci_driver.c:69:[parse_status] sockfd 0 lbusid 0-0 libusbip: debug: vhci_driver.c:67:[parse_status] hub hs port 1 status 4 speed 0 devid 0 libusbip: debug: vhci_driver.c:69:[parse_status] sockfd 0 lbusid 0-0 libusbip: debug: vhci_driver.c:67:[parse_status] hub hs port 2 status 4 speed 0 devid 0 libusbip: debug: vhci_driver.c:69:[parse_status] sockfd 0 lbusid 0-0 libusbip: debug: vhci_driver.c:67:[parse_status] hub hs port 3 status 4 speed 0 devid 0 libusbip: debug: vhci_driver.c:69:[parse_status] sockfd 0 lbusid 0-0 libusbip: debug: vhci_driver.c:67:[parse_status] hub hs port 4 status 4 speed 0 devid 0 libusbip: debug: vhci_driver.c:69:[parse_status] sockfd 0 lbusid 0-0 libusbip: debug: vhci_driver.c:67:[parse_status] hub hs port 5 status 4 speed 0 devid 0 libusbip: debug: vhci_driver.c:69:[parse_status] sockfd 0 lbusid 0-0 libusbip: debug: vhci_driver.c:67:[parse_status] hub hs port 6 status 4 speed 0 devid 0 libusbip: debug: vhci_driver.c:69:[parse_status] sockfd 0 lbusid 0-0 libusbip: debug: vhci_driver.c:67:[parse_status] hub hs port 7 status 4 speed 0 devid 0 libusbip: debug: vhci_driver.c:69:[parse_status] sockfd 0 lbusid 0-0 libusbip: debug: vhci_driver.c:67:[parse_status] hub ss port 8 status 4 speed 0 devid 0 libusbip: debug: vhci_driver.c:69:[parse_status] sockfd 0 lbusid 0-0 libusbip: debug: vhci_driver.c:67:[parse_status] hub ss port 9 status 4 speed 0 devid 0 libusbip: debug: vhci_driver.c:69:[parse_status] sockfd 0 lbusid 0-0 libusbip: debug: vhci_driver.c:67:[parse_status] hub ss port 10 status 4 speed 0 devid 0 libusbip: debug: vhci_driver.c:69:[parse_status] sockfd 0 lbusid 0-0 libusbip: debug: vhci_driver.c:67:[parse_status] hub ss port 11 status 4 speed 0 devid 0 libusbip: debug: vhci_driver.c:69:[parse_status] sockfd 0 lbusid 0-0 libusbip: debug: vhci_driver.c:67:[parse_status] hub ss port 12 status 4 speed 0 devid 0 libusbip: debug: vhci_driver.c:69:[parse_status] sockfd 0 lbusid 0-0 libusbip: debug: vhci_driver.c:67:[parse_status] hub ss port 13 status 4 speed 0 devid 0 libusbip: debug: vhci_driver.c:69:[parse_status] sockfd 0 lbusid 0-0 libusbip: debug: vhci_driver.c:67:[parse_status] hub ss port 14 status 4 speed 0 devid 0 libusbip: debug: vhci_driver.c:69:[parse_status] sockfd 0 lbusid 0-0 libusbip: debug: vhci_driver.c:67:[parse_status] hub ss port 15 status 4 speed 0 devid 0 libusbip: debug: vhci_driver.c:69:[parse_status] sockfd 0 lbusid 0-0 libusbip: debug: vhci_driver.c:104:[parse_status] exit usbip: debug: usbip_attach.c:100:[import_device] got free port 0 libusbip: debug: vhci_driver.c:367:[usbip_vhci_attach_device2] writing: 0 3 131074 2 libusbip: debug: vhci_driver.c:372:[usbip_vhci_attach_device2] attach attribute path: /sys/devices/platform/vhci_hcd.0/attach libusbip: debug: vhci_driver.c:380:[usbip_vhci_attach_device2] attached port: 0 ``` (With a success code of 0) Which I have not found very informative, but when attaching this https://github.com/bulwarkid/virtual-fido.git USB IP Virtual Device, I found success. This I proceeded to reverse engineer the working USB IP Device with Wireshark, which led mo to the fact that the connection start with the interchange ``` OP_REQ_IMPORT: 00000000 01 11 80 03 00 00 00 00 ....... 00000008 32 2d 32 00 00 00 00 00 00 00 00 00 00 00 00 00 2-2..... ........ 00000018 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ........ ........ OP_REP_IMPORT: 00000000 01 11 00 03 00 00 00 00 2f 64 65 76 69 63 65 2f ........ /device/ 00000010 30 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0....... ........ 00000020 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ........ ........ 00000030 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ........ ........ 00000040 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ........ ........ 00000050 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ........ ........ 00000060 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ........ ........ 00000070 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ........ ........ 00000080 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ........ ........ 00000090 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ........ ........ 000000A0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ........ ........ 000000B0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ........ ........ 000000C0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ........ ........ 000000D0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ........ ........ 000000E0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ........ ........ 000000F0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ........ ........ 00000100 00 00 00 00 00 00 00 00 32 2d 32 00 00 00 00 00 ........ 2-2..... 00000110 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ........ ........ 00000120 00 00 00 00 00 00 00 00 00 00 00 02 00 00 00 02 ........ ........ 00000130 00 00 00 02 00 00 00 00 00 00 00 00 00 00 01 01 ........ ........ ``` And replicating the same exact behavior in my application in my application, I get the same exact error, and is actually error that I share in the start of this email. So I would appreciate any help that could help mo to get out of thick wall brick where I found myself now. As an extra remark, I have not understood yet which are supposed to contain the fields: transfer_flags, setup and transfer buffer. I guess it has something to do with the USB specification (https://www.usb.org/document-library/usb-20-specification), Which have to still finish reading. Cordially, Pixiae
