Once I figured out that I needed to explicitly enable USB2 I was quite pleased with how simple USB access under KVM was. Firing up the custom app in the Windows KVM guest I could see the traffic going back and forth to each of the device endpoints and work out what was going on.Īll of this was much more flexible than using a standalone Windows box. Once this was done I was able to start Wireshark which rather nicely has full USB decoding support. modprobe usbmon created the appropriate /dev/usbmon files and I chowned the appropriate bus to my normal user. It was also happy to do the firmware update (along with various device resets on the way as it changed USB ID - this is why I needed the udev rule, to ensure every time the device re-appeared it would be seen by the KVM instance without manual intervention).Īfter that was complete I investigated usbmon. This gave me a Windows setup that could see the USB dongle and install the appropriate drivers. I dropped a udev rules file into /etc/udev/rules.d to ensure any device nodes created belonged to my normal user. I also told KVM to grab all the ZTE devices with -device usb-host,bus=ehci.0,vendorid=0x19d2. That involved passing -usb -device usb-ehci,id=ehci to KVM.
I hadn’t yet used the USB support in this, but I thought I’d see what it was capable of.įirstly I had to explicitly enable USB2 - the device wasn’t happy with the default USB1 only stack that KVM enabled. These days I don’t have a dedicated Windows box, but I do have a Windows 7 KVM virtual machine. I was also hoping to sniff the traffic to see how to drive the voice side of things. Recently I wanted to do a firmware upgrade of a ZTE 3G modem dongle, partly to provider unlock it and partly to try and enable some voice functionality. When I first wanted to reverse engineer a USB device that only had Windows drivers the “easy” option was to take a Windows machine, install usbsnoop on it and capture the traffic as a bunch of verbose text files. However hopefully these notes will remind me enough next time.) (This is something I did a few months ago, and I really should have noted down all the details then so I covered everything.
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