On Mon, 9 Dec 2019, Yuan, Shengquan wrote: > Hi, > > I tried to use usbmon to capture the USB packets when inserting a > u-disk, however, I didn't see the SET_ADDRESS request To understand what's going on, you need to know how usbmon works. It intercepts data at the point where the kernel sends it to or receives it from the host controller driver. usbmon is not directly aware of the actual packets that get transmitted on the USB bus. > Below is the packet list, in packet 88, the host suddenly uses > address 74 to communicate with U-disk. I am wondering whether usbmon > will capture SET_ADDRESS request? > > 71 8.463514 host 1.1.1 USB 64 URB_INTERRUPT in > 72 8.463536 host 1.1.0 USBHUB 64 GET_STATUS Request [Port 6] > 73 8.463553 1.1.0 host USBHUB 68 GET_STATUS Response [Port 6] > 74 8.463613 host 1.1.0 USBHUB 64 SET_FEATURE Request [Port 6: PORT_RESET] > 75 8.463626 1.1.0 host USBHUB 64 SET_FEATURE Response [Port 6: PORT_RESET] > 76 8.523469 host 1.1.0 USBHUB 64 GET_STATUS Request [Port 6] > 77 8.523487 1.1.0 host USBHUB 68 GET_STATUS Response [Port 6] > 78 8.523495 host 1.1.0 USBHUB 64 CLEAR_FEATURE Request [Port 6: C_PORT_RESET] > 79 8.523501 1.1.0 host USBHUB 64 CLEAR_FEATURE Response [Port 6: C_PORT_RESET] > 80 8.583690 host 1.0.0 USB 64 GET DESCRIPTOR Request DEVICE > 81 8.583781 1.0.0 host USB 82 GET DESCRIPTOR Response DEVICE > 82 8.583820 host 1.1.0 USBHUB 64 SET_FEATURE Request [Port 6: PORT_RESET] > 83 8.583837 1.1.0 host USBHUB 64 SET_FEATURE Response [Port 6: PORT_RESET] > 84 8.643643 host 1.1.0 USBHUB 64 GET_STATUS Request [Port 6] > 85 8.643666 1.1.0 host USBHUB 68 GET_STATUS Response [Port 6] > 86 8.643675 host 1.1.0 USBHUB 64 CLEAR_FEATURE Request [Port 6: C_PORT_RESET] > 87 8.643680 1.1.0 host USBHUB 64 CLEAR_FEATURE Response [Port 6: C_PORT_RESET] > 88 8.723558 host 1.74.0 USB 64 GET DESCRIPTOR Request DEVICE > 89 8.723650 1.74.0 host USB 82 GET DESCRIPTOR Response DEVICE > 90 8.723692 host 1.74.0 USB 64 GET DESCRIPTOR Request BOS usbmon _will_ capture Set-Address packets if the kernel sends them. However, the kernel does not always send them. I'm going to guess that the USB host controller for your bus 1 is xHCI. Unlike other types of host controller, an xHCI host controller automatically sends a Set-Address packet whenever it discovers a new device has been plugged in, with no need for the kernel to tell it to do so. As a result, there is no data for usbmon to intercept and so no Set-Address packet shows up in the usbmon output. Alan Stern
