VDSM Hook 例子

您必须确保不管从哪个来源安装到您的系统中的 Hook
脚本，都针对您的环境进行过全面的测试。

目标：.
此 Hook 脚本将根据 hostusb 自定义属性的值来使得虚拟机能够使用主机上的
USB 设备。如果该自定义选项的值未被设置，则不会执行任何操作。

Important

使用此 Hook
要求必须把虚拟机固定在单独一台主机上运行，该虚拟机的迁移操作都会失败。

  1. hostusb=0x[\da-fA-F]{4}:0x[\da-fA-F]{4}(&0x[\da-fA-F]{4}:0x[\da-fA-F]{4})*

上面使用的正则表达式使得 hostusb
这个自定义属性能够接受一个或者多个由“:”分隔的两个四位十六进制数（例如
0x1234:0xbeef）的组合，如果是多个的话则它们之间由“&”分隔。其中每个组合表示一个主机上的
USB 设备，前面一个四位十六进制数表示厂商的 ID，后一个十六进制数表示产品
ID（例如刚才的例子，0x1234 表示厂商，0xbeef 表示产品）。

脚本：.
/usr/libexec/vdsm/hooks/before_vm_start/50_hostusb

  1. #!/usr/bin/python
  3. import re
  4. import os
  5. import sys
  6. import grp
  7. import pwd
  8. import traceback
  10. import hooking
  12. '''
  13. host usb hook
  14. =============
  16.           !!! Disclaimer !!!
  17. *******************************************
  18. The host side usb support wasn't thoroughly
  19. tests in kvm!
  20. *******************************************
  22. add hosts usb device/s to VM:
  24. <hostdev mode='subsystem' type='usb'>
  25.     <source>
  26.         <vendor id='0x1234'/>
  27.         <product id='0xbeef'/>
  28.     </source>
  29. </hostdev>
  31. syntax:
  32.     hostusb=0x1234:0xbeef&0x2222:0xabaa
  33.     i.e.
  34.     hostusb=VendorId:ProductId (can add more then one with '&' separator)
  36. Note:
  37.     The VM must be pinned to host and this hook will
  38.     fail any migration attempt.
  39. '''
  41. HOOK_HOSTUSB_PATH = '/var/run/vdsm/hooks/hostusb-permissions'
  44. def log_dev_owner(devpath, user, group):
  45.     entry = devpath + ":" + str(user) + ":" + str(group)
  47.     if not os.path.isdir(os.path.dirname(HOOK_HOSTUSB_PATH)):
  48.         os.mkdir(os.path.dirname(HOOK_HOSTUSB_PATH))
  50.     if os.path.isfile(HOOK_HOSTUSB_PATH):
  51.         f = file(HOOK_HOSTUSB_PATH, 'r')
  52.         for line in f:
  53.             if entry == line:
  54.                 f.close()
  55.                 return
  57.     f = file(HOOK_HOSTUSB_PATH, 'a')
  58.     f.writelines(entry)
  59.     f.close()
  62. def chown(vendorid, productid):
  64.     # remove the 0x from the vendor and product id
  65.     devid = vendorid[2:] + ':' + productid[2:]
  66.     command = ['lsusb', '-d', devid]
  67.     retcode, out, err = hooking.execCmd(command, sudo=False, raw=True)
  68.     if retcode != 0:
  69.         sys.stderr.write('hostusb: cannot find usb device: %s\n' % devid)
  70.         sys.exit(2)
  72.     # find the device path:
  73.     # /dev/bus/usb/xxx/xxx
  74.     devpath = '/dev/bus/usb/' + out[4:7] + '/' + out[15:18]
  75.     stat = os.stat(devpath)
  77.     group = grp.getgrnam('qemu')
  78.     gid = group.gr_gid
  79.     user = pwd.getpwnam('qemu')
  80.     uid = user.pw_uid
  82.     # we don't use os.chown because we need sudo
  83.     owner = str(uid) + ':' + str(gid)
  84.     command = ['/bin/chown', owner, devpath]
  85.     retcode, out, err = hooking.execCmd(command, sudo=True, raw=True)
  86.     if retcode != 0:
  87.         sys.stderr.write('hostusb: error chown %s to %s, err = %s\n' %
  88.                          (devpath, owner, err))
  89.         sys.exit(2)
  91.     log_dev_owner(devpath, stat.st_uid, stat.st_gid)
  94. def create_usb_device(domxml, vendorid, productid):
  95.     hostdev = domxml.createElement('hostdev')
  96.     hostdev.setAttribute('mode', 'subsystem')
  97.     hostdev.setAttribute('type', 'usb')
  99.     source = domxml.createElement('source')
  100.     hostdev.appendChild(source)
  102.     vendor = domxml.createElement('vendor')
  103.     vendor.setAttribute('id', vendorid)
  104.     source.appendChild(vendor)
  106.     product = domxml.createElement('product')
  107.     product.setAttribute('id', productid)
  108.     source.appendChild(product)
  110.     return hostdev
  112. if 'hostusb' in os.environ:
  113.     try:
  114.         regex = re.compile('^0x[\d,A-F,a-f]{4}$')
  115.         domxml = hooking.read_domxml()
  116.         devices = domxml.getElementsByTagName('devices')[0]
  118.         for usb in os.environ['hostusb'].split('&'):
  119.             vendorid, productid = usb.split(':')
  120.             if len(regex.findall(vendorid)) != 1 or \
  121.                     len(regex.findall(productid)) != 1:
  122.                 sys.stderr.write('hostusb: bad input, expected 0x0000 format '
  123.                                  'for vendor and product id, input: %s:%s\n' %
  124.                                  (vendorid, productid))
  125.                 sys.exit(2)
  127.             hostdev = create_usb_device(domxml, vendorid, productid)
  128.             devices.appendChild(hostdev)
  129.             chown(vendorid, productid)
  131.         hooking.write_domxml(domxml)
  132.     except:
  133.         sys.stderr.write('hostusb: [unexpected error]: %s\n' %
  134.                          traceback.format_exc())
  135.         sys.exit(2)