USB over IP: How to remote-access your USB devices over the network

 

First appearing in 2005 in Takahiro Hirofuchi's kickass paper, there are much better guides on USB/IP, like Linux Magazine's, Ridgerun's, etc. From 2009 USB/IP was accepted into mainline Linux kernel and up-to-date documentation on it tends to get lost in the Linux haystack. The wrinkle here is USB/IP running on Slackware 14.2-current as of July 2019. Unlike Debian/Ubuntu you cannot usually seamlessly install USB/IP (or most other things) on Slackware. A little DIY is in order.

I know that is cold comfort compared to Debian's 'apt install'. Indeed, Slackware too has its (a little rickety) SlackBuild scripts. But in USB/IP case there is no SlackBuild as it was already included in the kernel. Well, after a fashion.

But take heart: in 30 years of Slackware I seldom fail to install the things I want. This is a chance to poke a little into the innards of Linux. You have the source code in all its glory. And it is built beautifully - I say this as one who has seen Microsoft Windows NT source code [shudder]. 

And the experience will prove useful in the rare instances Debian's installs fail, like the time I installed the Java development kit and could no longer log into my desktop. This means when things fail the same methods work: paste the error into google and look for the patches and workarounds. But I digress; back to USB/IP.  

I should test my Acer aspireM3's USB webcam before the install breaks things:

# mplayer tv:// -tv driver=v4l2:width=640:height=480 -vo xv -tv device=/dev/video1

Let's verify that my Slackware kernel actuall has USB/IP:

root@aspireM3:~# ls -lR /usr/src/linux/ | grep -i usbip
-rw-r--r-- 1 root root  1172 Jan 26  2019 sysfs-platform-usbip-vudc
-rw-r--r-- 1 root root 23365 Jan 26  2019 usbip_protocol.txt

drwxr-xr-x 2 root root  4096 Jan 26  2019 usbip/
/usr/src/linux/drivers/usb/usbip:
-rw-r--r-- 1 root root 18694 Jan 26  2019 usbip_common.c
-rw-r--r-- 1 root root 10117 Jan 26  2019 usbip_common.h
-rw-r--r-- 1 root root  3969 Jan 26  2019 usbip_event.c
drwxr-xr-x  3 root root   4096 Jan 27  2019 usbip/

Looks good. A look at the kernel's config file shows that the binary has not been left out at compile time:

root@aspireM3:~# grep -i usbip /usr/src/linux/.config

CONFIG_USBIP_CORE=m

CONFIG_USBIP_VHCI_HCD=m

CONFIG_USBIP_VHCI_HC_PORTS=8

CONFIG_USBIP_VHCI_NR_HCS=1

CONFIG_USBIP_HOST=m

# CONFIG_USBIP_DEBUG is not set

And finally, locate the kernel modules (ie device drivers) themselves:

# ls -l /lib/modules/4.19.18/kernel/drivers/usb/usbip

total 128

-rw-r--r-- 1 root root 22576 Jan 27  2019 usbip-core.ko

-rw-r--r-- 1 root root 42480 Jan 27  2019 usbip-host.ko

-rw-r--r-- 1 root root 58016 Jan 27  2019 vhci-hcd.ko

And it runs OK:

# modprobe -v usbip-core

insmod /lib/modules/4.19.18/kernel/drivers/usb/usbip/usbip-core.ko

Let's launch the USB/IP server daemon:

# usbipd -D

-su: usbipd: command not found

Oops. The userspace binaries are not installed. Let's see if my Slackware installation has the userspace source code:

# ls -l /usr/src/linux/tools/usb/usbip/src

total 96

-rw-r--r-- 1 root root   440 Jan 26  2019 Makefile.am

-rw-r--r-- 1 root root  4406 Jan 26  2019 usbip.c

-rw-r--r-- 1 root root  1292 Jan 26  2019 usbip.h

-rw-r--r-- 1 root root  5404 Jan 26  2019 usbip_attach.c

-rw-r--r-- 1 root root  5169 Jan 26  2019 usbip_bind.c

-rw-r--r-- 1 root root  2922 Jan 26  2019 usbip_detach.c

-rw-r--r-- 1 root root  9713 Jan 26  2019 usbip_list.c

-rw-r--r-- 1 root root  6179 Jan 26  2019 usbip_network.c

-rw-r--r-- 1 root root  5295 Jan 26  2019 usbip_network.h

-rw-r--r-- 1 root root  1536 Jan 26  2019 usbip_port.c

-rw-r--r-- 1 root root  3494 Jan 26  2019 usbip_unbind.c

-rw-r--r-- 1 root root 15083 Jan 26  2019 usbipd.c

-rw-r--r-- 1 root root  1630 Jan 26  2019 utils.c

-rw-r--r-- 1 root root   863 Jan 26  2019 utils.h

Yes, I do. I just need to compile it but it fails:

/usr/src/linux/tools/usb/usbip# ./autogen.sh

/usr/src/linux/tools/usb/usbip# ./configure

/usr/src/linux/tools/usb/usbip# make

make  all-recursive

make[1]: Entering directory '/usr/src/linux-4.19.18/tools/usb/usbip'

Making all in libsrc

make[2]: Entering directory '/usr/src/linux-4.19.18/tools/usb/usbip/libsrc'

  CC       libusbip_la-usbip_device_driver.lo

usbip_device_driver.c: In function �..read_usb_vudc_device�..:

usbip_device_driver.c:106:2: error: �..strncpy�.. specified bound 256 equals destination size [Werror=stringop-truncation]

  strncpy(dev->path, path, SYSFS_PATH_MAX);

  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

usbip_device_driver.c:125:2: error: �..strncpy�.. specified bound 32 equals dest

ination size [-Werror=stringop-truncation]

  strncpy(dev->busid, name, SYSFS_BUS_ID_SIZE);

  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

cc1: all warnings being treated as errors

make[2]: *** [Makefile:471: libusbip_la-usbip_device_driver.lo] Error 1

make[2]: Leaving directory '/usr/src/linux-4.19.18/tools/usb/usbip/libsrc'

make[1]: *** [Makefile:497: all-recursive] Error 1

make[1]: Leaving directory '/usr/src/linux-4.19.18/tools/usb/usbip'

make: *** [Makefile:365: all] Error 2

It does not look serious. What used to be a compiler warning has now been classified as an error so the compiler obligingly stops. A quick google comes up with a patch:

https://patchwork.kernel.org/project/linux-usb/patch/20180721021232.GR14131@deca

dent.org.uk/

> +++ b/tools/usb/usbip/libsrc/usbip_common.c

> @@ -226,8 +226,8 @@ int read_usb_device(struct udev_device *

>       path = udev_device_get_syspath(sdev);

>       name = udev_device_get_sysname(sdev);

>

> -     strncpy(udev->path,  path,  SYSFS_PATH_MAX);

> -     strncpy(udev->busid, name, SYSFS_BUS_ID_SIZE);

> +     snprintf(udev->path, SYSFS_PATH_MAX, "%s", path);

> +     snprintf(udev->busid, SYSFS_BUS_ID_SIZE, "%s", name);

So I just edit usbip_device_driver.c:

# vi libsrc/usbip_device_driver.c

 And at line 106

        strncpy(dev->path, path, SYSFS_PATH_MAX);

 Is changed to

        // strncpy(dev->path, path, SYSFS_PATH_MAX); cmheong 2021-03-27

        snprintf(dev->path, SYSFS_PATH_MAX, "%s", path);

At line 125:

strncpy(dev->busid, name, SYSFS_BUS_ID_SIZE);

           Became

snprintf(dev->busid, SYSFS_BUS_ID_SIZE, "%s", name);

Anow for the file usbip_common.c line 230:

        // strncpy(udev->path,  path,  SYSFS_PATH_MAX); // cmheong 2021-03-27

        // strncpy(udev->busid, name, SYSFS_BUS_ID_SIZE);

Becomes

        snprintf(udev->path, SYSFS_PATH_MAX, "%s", path);

        snprintf(udev->busid, SYSFS_BUS_ID_SIZE, "%s", name);

Now some Slackware versions, depending on the date of your install, you might get an additional error:

  CC       usbip_network.o

usbip_network.c: In function âusbip_net_pack_usb_deviceâ:

usbip_network.c:91:32: error: taking address of packed member of âstruct usbip_

usb_deviceâ may result in an unaligned pointer value [-Werror=address-of-packed

-member]

   91 |  usbip_net_pack_uint32_t(pack, &udev->busnum);

      |                                ^~~~~~~~~~~~~

We just need to tell the compiler not to freak out and treat the warning as an error. This can be done by changing line 12174 of the 'configure' file:

/usr/src/linux/tools/usb/usbip$vi configure

EXTRA_CFLAGS="-Wall -Wno-error=address-of-packed-member -Werror -Wextra -std=gnu

99"

After which the compile completes successfully:

# make

make  all-recursive

make[1]: Entering directory '/usr/src/linux-4.19.18/tools/usb/usbip'

Making all in libsrc

make[2]: Entering directory '/usr/src/linux-4.19.18/tools/usb/usbip/libsrc'

  CC       libusbip_la-usbip_common.lo

  CC       libusbip_la-usbip_host_common.lo

  CC       libusbip_la-vhci_driver.lo

  CC       libusbip_la-sysfs_utils.lo

  CCLD     libusbip.la

make[2]: Leaving directory '/usr/src/linux-4.19.18/tools/usb/usbip/libsrc'

Making all in src

make[2]: Entering directory '/usr/src/linux-4.19.18/tools/usb/usbip/src'

  CC       usbip.o

  CC       utils.o

  CC       usbip_network.o

  CC       usbip_attach.o

  CC       usbip_detach.o

  CC       usbip_list.o

  CC       usbip_bind.o

  CC       usbip_unbind.o

  CC       usbip_port.o

  CCLD     usbip

  CC       usbipd.o

  CCLD     usbipd

make[2]: Leaving directory '/usr/src/linux-4.19.18/tools/usb/usbip/src'

make[2]: Entering directory '/usr/src/linux-4.19.18/tools/usb/usbip'

make[2]: Leaving directory '/usr/src/linux-4.19.18/tools/usb/usbip'

make[1]: Leaving directory '/usr/src/linux-4.19.18/tools/usb/usbip'

Now the server daemon runs:

# /usr/src/linux/tools/usb/usbip/src/usbipd -D

A quick check:

/usr/src/linux/tools/usb/usbip# ps -ef | grep -e usbip

root     23597     2  0 14:57 ?        00:00:00 [usbip_event]

root     23608     1  0 19:53 ?        00:00:00 /usr/src/linux/tools/usb/usbip/src/.libs/lt-usbipd -D

root     23835  1533  0 19:54 pts/0    00:00:00 grep -e usbip

Next we list the USB devices available to the server:

/usr/src/linux/tools/usb/usbip# /usr/src/linux/tools/usb/usbip/src/usbip list --local

 - busid 1-3.1 (0835:8501)

   Action Star Enterprise Co., Ltd : unknown product (0835:8501)

 - busid 1-3.2 (046d:c077)

   Logitech, Inc. : M105 Optical Mouse (046d:c077)

 - busid 1-3.3 (13ba:0017)

   PCPlay : PS/2 Keyboard+Mouse Adapter (13ba:0017)

 - busid 1-3.4 (10c4:ea60)

   Cygnal Integrated Products, Inc. : CP2102/CP2109 UART Bridge Controller [CP21

0x family] (10c4:ea60)

 - busid 1-3.5.1 (0835:8502)

   Action Star Enterprise Co., Ltd : unknown product (0835:8502)

 - busid 1-3.5.2 (046d:0829)

   Logitech, Inc. : unknown product (046d:0829)

 - busid 1-3.5.4 (0c45:62f1)

   Microdia : unknown product (0c45:62f1)

 - busid 2-1.3 (04f2:b300)

   Chicony Electronics Co., Ltd : unknown product (04f2:b300)

 - busid 2-1.4 (04ca:3006)

   Lite-On Technology Corp. : unknown product (04ca:3006)

Using the displayed busis, we use 'lsusb -v' to zero in on the webcam:

Bus 002 Device 003: ID 04f2:b300 Chicony Electronics Co., Ltd

  iManufacturer           1 Chicony Electronics Co., Ltd.

  iProduct                2 HD WebCam

  iSerial                 3 SN0001

 - busid 2-1.3 (04f2:b300)

Now I need to launch another kernel module:

# modprobe -v usbip-host

insmod /lib/modules/4.19.18/kernel/drivers/usb/usbip/usbip-host.ko

We now have the USB/IP server grab the webcam:

/usr/src/linux/tools/usb/usbip# /usr/src/linux/tools/usb/usbip/src/usbip bind --busid=2-1.3

usbip: info: bind device on busid 2-1.3: complete

Now we move over to the other (ie client) computer, and repeat the process of installing USB/IP. We then launch the USB/IP kernel client modules:

/usr/src/linux/tools/usb/usbip$modprobe -v vhci-hcd

insmod /lib/modules/4.19.62/kernel/drivers/usb/usbip/usbip-core.ko

insmod /lib/modules/4.19.62/kernel/drivers/usb/usbip/vhci-hcd.ko

Let's say the server's IP address is 12.34.56.78. We can see what USB device on the server is available over IP:

/usr/src/linux/tools/usb/usbip$src/usbip list --remote=12.34.56.78

Exportable USB devices

======================

 - 12.34.56.78

      2-1.3: Chicony Electronics Co., Ltd : unknown product (04f2:b300)

           : /sys/devices/pci0000:00/0000:00:1a.0/usb2/2-1/2-1.3

           : Miscellaneous Device / ? / Interface Association (ef/02/01). 

 

Ah it is a webcam ;7) We attach to it:

/usr/src/linux/tools/usb/usbip# /usr/src/linux/tools/usb/usbip/src/usbip attach -debug --remote=12.34.56.78 --busid=2-1.3

And we play the remote (ie server) webcam by using mplayer:

/usr/src/linux/tools/usb/usbip$ mplayer -cache 128 -tv device=/dev/video2:driver=v4l2:width=640:height=480:outfmt=i420 -vo xv tv://

Note that here I access /dev/video2, since my client laptop also has a webcam at /dev/video1, and the USB/IP attach made a new one at /dev/video2.  Also the server webcam resolution is 1080 x 720 but that seemed to mave maxed out my old 100Mbps fiber link. Dropping the resolution down to 640 x 480 worked out well.

You can see your attached USB device using:

/usr/src/linux/tools/usb/usbip$src/usbip port --remote=12.34.56.78

Imported USB devices

====================

Port 00: <Port in Use> at High Speed(480Mbps)

       Chicony Electronics Co., Ltd : unknown product (04f2:b300)

       3-1 -> usbip://192.168.1.4:3240/3-1.3

           -> remote bus/dev 003/003

Notice the port number 00. We will be needing it. Lastly once you are through with the webcam you release it so another computer can use it:

/usr/src/linux/tools/usb/usbip$src/usbip detach --port=00

usbip: info: Port 0 is now detached!

There you have it. USB/IP comes standard with Linux, and lets you access USB devices remotely. I had great fun spending an afternoon doing this to the boogie blues. Here's a video of Daisy tapping her feet to it:

Click on picture for the video

Happy Trails.