python/vserver.py

   1 # Copyright 2005 Princeton University
   2
   3 import errno
   4 import fcntl
   5 import os
   6 import re
   7 import sys
   8 import time
   9 import traceback
  10
  11 import mountimpl
  12 import linuxcaps
  13 import passfdimpl
  14 import utmp
  15 import vserverimpl, vduimpl
  16
  17 from util_vserver_vars import *
  18
  19 CAP_SAFE = (linuxcaps.CAP_CHOWN |
  20             linuxcaps.CAP_DAC_OVERRIDE |
  21             linuxcaps.CAP_DAC_READ_SEARCH |
  22             linuxcaps.CAP_FOWNER |
  23             linuxcaps.CAP_FSETID |
  24             linuxcaps.CAP_KILL |
  25             linuxcaps.CAP_SETGID |
  26             linuxcaps.CAP_SETUID |
  27             linuxcaps.CAP_SETPCAP |
  28             linuxcaps.CAP_SYS_TTY_CONFIG |
  29             linuxcaps.CAP_LEASE |
  30             linuxcaps.CAP_SYS_CHROOT |
  31             linuxcaps.CAP_SYS_PTRACE)
  32
  33 #
  34 # these are the flags taken from the kernel linux/vserver/legacy.h
  35 #
  36 FLAGS_LOCK = 1
  37 FLAGS_SCHED = 2  # XXX - defined in util-vserver/src/chcontext.c
  38 FLAGS_NPROC = 4
  39 FLAGS_PRIVATE = 8
  40 FLAGS_INIT = 16
  41 FLAGS_HIDEINFO = 32
  42 FLAGS_ULIMIT = 64
  43 FLAGS_NAMESPACE = 128
  44
  45 # default values for new vserver scheduler
  46 SCHED_TOKENS_MIN = 50
  47 SCHED_TOKENS_MAX = 100
  48
  49
  50 class VServer:
  51
  52     INITSCRIPTS = [('/etc/rc.vinit', 'start'),
  53                    ('/etc/rc.d/rc', '%(runlevel)d')]
  54
  55     def __init__(self, name):
  56
  57         self.name = name
  58         self.config = self.__read_config_file("/etc/vservers.conf")
  59         self.config.update(self.__read_config_file("/etc/vservers/%s.conf" %
  60                                                    self.name))
  61         self.flags = 0
  62         flags = self.config["S_FLAGS"].split(" ")
  63         if "lock" in flags:
  64             self.flags |= FLAGS_LOCK
  65         if "nproc" in flags:
  66             self.flags |= FLAGS_NPROC
  67         self.remove_caps = ~CAP_SAFE
  68         self.ctx = int(self.config["S_CONTEXT"])
  69
  70     config_var_re = re.compile(r"^ *([A-Z_]+)=(.*)\n?$", re.MULTILINE)
  71
  72     def __read_config_file(self, filename):
  73
  74         f = open(filename, "r")
  75         data = f.read()
  76         f.close()
  77         config = {}
  78         for m in self.config_var_re.finditer(data):
  79             (key, val) = m.groups()
  80             config[key] = val.strip('"')
  81         return config
  82
  83     def __do_chroot(self):
  84
  85         return os.chroot("%s/%s" % (VROOTDIR, self.name))
  86
  87     def set_dlimit(self, blocktotal):
  88         path = "%s/%s" % (VROOTDIR, self.name)
  89         inodes, blockcount, size = vduimpl.vdu(path)
  90         blockcount = blockcount >> 1
  91
  92         if blocktotal > blockcount:
  93             vserverimpl.setdlimit(path, self.ctx, blockcount>>1, \
  94                                   blocktotal, inodes, -1, 2)
  95         else:
  96             # should raise some error value
  97             print "block limit (%d) ignored for vserver %s" %(blocktotal,self.name)
  98
  99     def get_dlimit(self):
 100         path = "%s/%s" % (VROOTDIR, self.name)
 101         try:
 102             blocksused, blocktotal, inodesused, inodestotal, reserved = \
 103                         vserverimpl.getdlimit(path,self.ctx)
 104         except OSError, ex:
 105             if ex.errno == 3:
 106                 # get here if no vserver disk limit has been set for xid
 107                 # set blockused to -1 to indicate no limit
 108                 blocktotal = -1
 109
 110         return blocktotal
 111
 112     def set_sched(self, shares, besteffort = True):
 113         global SCHED_TOKENS_MIN, SCHED_TOKENS_MAX
 114         tokensmin = SCHED_TOKENS_MIN
 115         tokensmax = SCHED_TOKENS_MAX
 116
 117         if besteffort is True:
 118             # magic "interval" value for Andy's scheduler to denote besteffort
 119             interval = 1000
 120             fillrate = shares
 121         else:
 122             interval = 1001
 123             fillrate = shares
 124
 125         try:
 126             vserverimpl.setsched(self.ctx,fillrate,interval,tokensmin,tokensmax)
 127         except OSError, ex:
 128             if ex.errno == 22:
 129                 print "kernel does not support vserver scheduler"
 130             else:
 131                 raise ex
 132
 133     def open(self, filename, mode = "r", bufsize = -1):
 134
 135         (sendsock, recvsock) = passfdimpl.socketpair()
 136         child_pid = os.fork()
 137         if child_pid == 0:
 138             try:
 139                 # child process
 140                 self.__do_chroot()
 141                 f = open(filename, mode)
 142                 passfdimpl.sendmsg(f.fileno(), sendsock)
 143                 os._exit(0)
 144             except EnvironmentError, ex:
 145                 (result, errmsg) = (ex.errno, ex.strerror)
 146             except Exception, ex:
 147                 (result, errmsg) = (255, str(ex))
 148             os.write(sendsock, errmsg)
 149             os._exit(result)
 150
 151         # parent process
 152
 153         # XXX - need this since a lambda can't raise an exception
 154         def __throw(ex):
 155             raise ex
 156
 157         os.close(sendsock)
 158         throw = lambda : __throw(Exception(errmsg))
 159         while True:
 160             try:
 161                 (pid, status) = os.waitpid(child_pid, 0)
 162                 if os.WIFEXITED(status):
 163                     result = os.WEXITSTATUS(status)
 164                     if result != 255:
 165                         errmsg = os.strerror(result)
 166                         throw = lambda : __throw(IOError(result, errmsg))
 167                     else:
 168                         errmsg = "unexpected exception in child"
 169                 else:
 170                     result = -1
 171                     errmsg = "child killed"
 172                 break
 173             except OSError, ex:
 174                 if ex.errno != errno.EINTR:
 175                     os.close(recvsock)
 176                     raise ex
 177         fcntl.fcntl(recvsock, fcntl.F_SETFL, os.O_NONBLOCK)
 178         try:
 179             (fd, errmsg) = passfdimpl.recvmsg(recvsock)
 180         except OSError, ex:
 181             if ex.errno != errno.EAGAIN:
 182                 throw = lambda : __throw(ex)
 183             fd = 0
 184         os.close(recvsock)
 185         if not fd:
 186             throw()
 187
 188         return os.fdopen(fd, mode, bufsize)
 189
 190     def __do_chcontext(self, state_file = None):
 191
 192         vserverimpl.chcontext(self.ctx, self.remove_caps)
 193         if not state_file:
 194             return
 195         print >>state_file, "S_CONTEXT=%d" % self.ctx
 196         print >>state_file, "S_PROFILE=%s" % self.config.get("S_PROFILE", "")
 197         state_file.close()
 198
 199     def __prep(self, runlevel, log):
 200
 201         """ Perform all the crap that the vserver script does before
 202         actually executing the startup scripts. """
 203
 204         # remove /var/run and /var/lock/subsys files
 205         # but don't remove utmp from the top-level /var/run
 206         RUNDIR = "/var/run"
 207         LOCKDIR = "/var/lock/subsys"
 208         filter_fn = lambda fs: filter(lambda f: f != 'utmp', fs)
 209         garbage = reduce((lambda (out, ff), (dir, subdirs, files):
 210                           (out + map((dir + "/").__add__, ff(files)),
 211                            lambda fs: fs)),
 212                          list(os.walk(RUNDIR)),
 213                          ([], filter_fn))[0]
 214         garbage += filter(os.path.isfile, map((LOCKDIR + "/").__add__,
 215                                               os.listdir(LOCKDIR)))
 216         for f in garbage:
 217             os.unlink(f)
 218
 219         # set the initial runlevel
 220         f = open(RUNDIR + "/utmp", "w")
 221         utmp.set_runlevel(f, runlevel)
 222         f.close()
 223
 224         # mount /proc and /dev/pts
 225         self.__do_mount("none", "/proc", "proc")
 226         # XXX - magic mount options
 227         self.__do_mount("none", "/dev/pts", "devpts", 0, "gid=5,mode=0620")
 228
 229     def __do_mount(self, *mount_args):
 230
 231         try:
 232             mountimpl.mount(*mount_args)
 233         except OSError, ex:
 234             if ex.errno == errno.EBUSY:
 235                 # assume already mounted
 236                 return
 237             raise ex
 238
 239     def enter(self):
 240
 241         state_file = open("/var/run/vservers/%s.ctx" % self.name, "w")
 242         self.__do_chroot()
 243         self.__do_chcontext(state_file)
 244
 245     def start(self, wait, runlevel = 3):
 246
 247         child_pid = os.fork()
 248         if child_pid == 0:
 249             # child process
 250             try:
 251                 # get a new session
 252                 os.setsid()
 253
 254                 # open state file to record vserver info
 255                 state_file = open("/var/run/vservers/%s.ctx" % self.name, "w")
 256
 257                 # use /dev/null for stdin, /var/log/boot.log for stdout/err
 258                 os.close(0)
 259                 os.close(1)
 260                 os.open("/dev/null", os.O_RDONLY)
 261                 self.__do_chroot()
 262                 log = open("/var/log/boot.log", "w", 0)
 263                 os.dup2(1, 2)
 264
 265                 print >>log, ("%s: starting the virtual server %s" %
 266                               (time.asctime(time.gmtime()), self.name))
 267
 268                 # perform pre-init cleanup
 269                 self.__prep(runlevel, log)
 270
 271                 # execute each init script in turn
 272                 # XXX - we don't support all scripts that vserver script does
 273                 cmd_pid = 0
 274                 for cmd in self.INITSCRIPTS + [None]:
 275                     # wait for previous command to terminate, unless it
 276                     # is the last one and the caller has specified to wait
 277                     if cmd_pid and (cmd != None or wait):
 278                         try:
 279                             os.waitpid(cmd_pid, 0)
 280                         except:
 281                             print >>log, "error waiting for %s:" % cmd_pid
 282                             traceback.print_exc()
 283
 284                     # end of list
 285                     if cmd == None:
 286                         os._exit(0)
 287
 288                     # fork and exec next command
 289                     cmd_pid = os.fork()
 290                     if cmd_pid == 0:
 291                         try:
 292                             # enter vserver context
 293                             self.__do_chcontext(state_file)
 294                             arg_subst = { 'runlevel': runlevel }
 295                             cmd_args = [cmd[0]] + map(lambda x: x % arg_subst,
 296                                                       cmd[1:])
 297                             print >>log, "executing '%s'" % " ".join(cmd_args)
 298                             os.execl(cmd[0], *cmd_args)
 299                         except:
 300                             traceback.print_exc()
 301                             os._exit(1)
 302                     else:
 303                         # don't want to write state_file multiple times
 304                         state_file = None
 305
 306             # we get here due to an exception in the top-level child process
 307             except Exception, ex:
 308                 traceback.print_exc()
 309             os._exit(0)
 310
 311         # parent process
 312         return child_pid