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
  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
  46
  47 class VServer:
  48
  49     INITSCRIPTS = [('/etc/rc.vinit', 'start'),
  50                    ('/etc/rc.d/rc', '%(runlevel)d')]
  51
  52     def __init__(self, name):
  53
  54         self.name = name
  55         self.config = self.__read_config_file("/etc/vservers.conf")
  56         self.config.update(self.__read_config_file("/etc/vservers/%s.conf" %
  57                                                    self.name))
  58         self.flags = 0
  59         flags = self.config["S_FLAGS"].split(" ")
  60         if "lock" in flags:
  61             self.flags |= FLAGS_LOCK
  62         if "nproc" in flags:
  63             self.flags |= FLAGS_NPROC
  64         self.remove_caps = ~CAP_SAFE
  65         self.ctx = int(self.config["S_CONTEXT"])
  66
  67     config_var_re = re.compile(r"^ *([A-Z_]+)=(.*)\n?$", re.MULTILINE)
  68
  69     def __read_config_file(self, filename):
  70
  71         f = open(filename, "r")
  72         data = f.read()
  73         f.close()
  74         config = {}
  75         for m in self.config_var_re.finditer(data):
  76             (key, val) = m.groups()
  77             config[key] = val.strip('"')
  78         return config
  79
  80     def __do_chroot(self):
  81
  82         return os.chroot("%s/%s" % (VROOTDIR, self.name))
  83
  84     def open(self, filename, mode = "r", bufsize = -1):
  85
  86         (sendsock, recvsock) = passfdimpl.socketpair()
  87         child_pid = os.fork()
  88         if child_pid == 0:
  89             try:
  90                 # child process
  91                 self.__do_chroot()
  92                 f = open(filename, mode)
  93                 passfdimpl.sendmsg(f.fileno(), sendsock)
  94                 os._exit(0)
  95             except EnvironmentError, ex:
  96                 (result, errmsg) = (ex.errno, ex.strerror)
  97             except Exception, ex:
  98                 (result, errmsg) = (255, str(ex))
  99             os.write(sendsock, errmsg)
 100             os._exit(result)
 101
 102         # parent process
 103
 104         # XXX - need this since a lambda can't raise an exception
 105         def __throw(ex):
 106             raise ex
 107
 108         os.close(sendsock)
 109         throw = lambda : __throw(Exception(errmsg))
 110         while True:
 111             try:
 112                 (pid, status) = os.waitpid(child_pid, 0)
 113                 if os.WIFEXITED(status):
 114                     result = os.WEXITSTATUS(status)
 115                     if result != 255:
 116                         errmsg = os.strerror(result)
 117                         throw = lambda : __throw(IOError(result, errmsg))
 118                     else:
 119                         errmsg = "unexpected exception in child"
 120                 else:
 121                     result = -1
 122                     errmsg = "child killed"
 123                 break
 124             except OSError, ex:
 125                 if ex.errno != errno.EINTR:
 126                     os.close(recvsock)
 127                     raise ex
 128         fcntl.fcntl(recvsock, fcntl.F_SETFL, os.O_NONBLOCK)
 129         try:
 130             (fd, errmsg) = passfdimpl.recvmsg(recvsock)
 131         except OSError, ex:
 132             if ex.errno != errno.EAGAIN:
 133                 throw = lambda : __throw(ex)
 134             fd = 0
 135         os.close(recvsock)
 136         if not fd:
 137             throw()
 138
 139         return os.fdopen(fd, mode, bufsize)
 140
 141     def __do_chcontext(self, state_file = None):
 142
 143         vserverimpl.chcontext(self.ctx, self.remove_caps)
 144         if not state_file:
 145             return
 146         print >>state_file, "S_CONTEXT=%d" % self.ctx
 147         print >>state_file, "S_PROFILE=%s" % self.config.get("S_PROFILE", "")
 148         state_file.close()
 149
 150     def __prep(self, runlevel, log):
 151
 152         """ Perform all the crap that the vserver script does before
 153         actually executing the startup scripts. """
 154
 155         # remove /var/run and /var/lock/subsys files
 156         # but don't remove utmp from the top-level /var/run
 157         RUNDIR = "/var/run"
 158         LOCKDIR = "/var/lock/subsys"
 159         filter_fn = lambda fs: filter(lambda f: f != 'utmp', fs)
 160         garbage = reduce((lambda (out, ff), (dir, subdirs, files):
 161                           (out + map((dir + "/").__add__, ff(files)),
 162                            lambda fs: fs)),
 163                          list(os.walk(RUNDIR)),
 164                          ([], filter_fn))[0]
 165         garbage += filter(os.path.isfile, map((LOCKDIR + "/").__add__,
 166                                               os.listdir(LOCKDIR)))
 167         for f in garbage:
 168             os.unlink(f)
 169
 170         # set the initial runlevel
 171         f = open(RUNDIR + "/utmp", "w")
 172         utmp.set_runlevel(f, runlevel)
 173         f.close()
 174
 175         # mount /proc and /dev/pts
 176         self.__do_mount("none", "/proc", "proc")
 177         # XXX - magic mount options
 178         self.__do_mount("none", "/dev/pts", "devpts", 0, "gid=5,mode=0620")
 179
 180     def __do_mount(self, *mount_args):
 181
 182         try:
 183             mountimpl.mount(*mount_args)
 184         except OSError, ex:
 185             if ex.errno == errno.EBUSY:
 186                 # assume already mounted
 187                 return
 188             raise ex
 189
 190     def enter(self):
 191
 192         state_file = open("/var/run/vservers/%s.ctx" % self.name, "w")
 193         self.__do_chroot()
 194         self.__do_chcontext(state_file)
 195
 196     def start(self, wait, runlevel = 3):
 197
 198         child_pid = os.fork()
 199         if child_pid == 0:
 200             # child process
 201             try:
 202                 # get a new session
 203                 os.setsid()
 204
 205                 # open state file to record vserver info
 206                 state_file = open("/var/run/vservers/%s.ctx" % self.name, "w")
 207
 208                 # use /dev/null for stdin, /var/log/boot.log for stdout/err
 209                 os.close(0)
 210                 os.close(1)
 211                 os.open("/dev/null", os.O_RDONLY)
 212                 self.__do_chroot()
 213                 log = open("/var/log/boot.log", "w", 0)
 214                 os.dup2(1, 2)
 215
 216                 print >>log, ("%s: starting the virtual server %s" %
 217                               (time.asctime(time.gmtime()), self.name))
 218
 219                 # perform pre-init cleanup
 220                 self.__prep(runlevel, log)
 221
 222                 # execute each init script in turn
 223                 # XXX - we don't support all scripts that vserver script does
 224                 cmd_pid = 0
 225                 for cmd in self.INITSCRIPTS + [None]:
 226                     # wait for previous command to terminate, unless it
 227                     # is the last one and the caller has specified to wait
 228                     if cmd_pid and (cmd != None or wait):
 229                         try:
 230                             os.waitpid(cmd_pid, 0)
 231                         except:
 232                             print >>log, "error waiting for %s:" % cmd_pid
 233                             traceback.print_exc()
 234
 235                     # end of list
 236                     if cmd == None:
 237                         os._exit(0)
 238
 239                     # fork and exec next command
 240                     cmd_pid = os.fork()
 241                     if cmd_pid == 0:
 242                         try:
 243                             # enter vserver context
 244                             self.__do_chcontext(state_file)
 245                             arg_subst = { 'runlevel': runlevel }
 246                             cmd_args = [cmd[0]] + map(lambda x: x % arg_subst,
 247                                                       cmd[1:])
 248                             print >>log, "executing '%s'" % " ".join(cmd_args)
 249                             os.execl(cmd[0], *cmd_args)
 250                         except:
 251                             traceback.print_exc()
 252                             os._exit(1)
 253                     else:
 254                         # don't want to write state_file multiple times
 255                         state_file = None
 256
 257             # we get here due to an exception in the top-level child process
 258             except Exception, ex:
 259                 traceback.print_exc()
 260             os._exit(0)
 261
 262         # parent process
 263         return child_pid