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
  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 set_dlimit(self, blocktotal):
  85         path = "%s/%s" % (VROOTDIR, self.name)
  86         inodes, blockcount, size = vduimpl.vdu(path)
  87         vserverimpl.setdlimit(path, self.ctx, blockcount>>1, blocktotal, inodes, -1, 2)
  88
  89     def get_dlimit(self):
  90         path = "%s/%s" % (VROOTDIR, self.name)
  91         try:
  92             blocksused, blocktotal, inodesused, inodestotal, reserved = \
  93                         vserverimpl.getdlimit(path,self.ctx)
  94         except OSError, ex:
  95             if ex.errno == 3:
  96                 # get here if no vserver disk limit has been set for xid
  97                 # set blockused to -1 to indicate no limit
  98                 blocktotal = -1
  99
 100         return blocktotal
 101
 102     def open(self, filename, mode = "r", bufsize = -1):
 103
 104         (sendsock, recvsock) = passfdimpl.socketpair()
 105         child_pid = os.fork()
 106         if child_pid == 0:
 107             try:
 108                 # child process
 109                 self.__do_chroot()
 110                 f = open(filename, mode)
 111                 passfdimpl.sendmsg(f.fileno(), sendsock)
 112                 os._exit(0)
 113             except EnvironmentError, ex:
 114                 (result, errmsg) = (ex.errno, ex.strerror)
 115             except Exception, ex:
 116                 (result, errmsg) = (255, str(ex))
 117             os.write(sendsock, errmsg)
 118             os._exit(result)
 119
 120         # parent process
 121
 122         # XXX - need this since a lambda can't raise an exception
 123         def __throw(ex):
 124             raise ex
 125
 126         os.close(sendsock)
 127         throw = lambda : __throw(Exception(errmsg))
 128         while True:
 129             try:
 130                 (pid, status) = os.waitpid(child_pid, 0)
 131                 if os.WIFEXITED(status):
 132                     result = os.WEXITSTATUS(status)
 133                     if result != 255:
 134                         errmsg = os.strerror(result)
 135                         throw = lambda : __throw(IOError(result, errmsg))
 136                     else:
 137                         errmsg = "unexpected exception in child"
 138                 else:
 139                     result = -1
 140                     errmsg = "child killed"
 141                 break
 142             except OSError, ex:
 143                 if ex.errno != errno.EINTR:
 144                     os.close(recvsock)
 145                     raise ex
 146         fcntl.fcntl(recvsock, fcntl.F_SETFL, os.O_NONBLOCK)
 147         try:
 148             (fd, errmsg) = passfdimpl.recvmsg(recvsock)
 149         except OSError, ex:
 150             if ex.errno != errno.EAGAIN:
 151                 throw = lambda : __throw(ex)
 152             fd = 0
 153         os.close(recvsock)
 154         if not fd:
 155             throw()
 156
 157         return os.fdopen(fd, mode, bufsize)
 158
 159     def __do_chcontext(self, state_file = None):
 160
 161         vserverimpl.chcontext(self.ctx, self.remove_caps)
 162         if not state_file:
 163             return
 164         print >>state_file, "S_CONTEXT=%d" % self.ctx
 165         print >>state_file, "S_PROFILE=%s" % self.config.get("S_PROFILE", "")
 166         state_file.close()
 167
 168     def __prep(self, runlevel, log):
 169
 170         """ Perform all the crap that the vserver script does before
 171         actually executing the startup scripts. """
 172
 173         # remove /var/run and /var/lock/subsys files
 174         # but don't remove utmp from the top-level /var/run
 175         RUNDIR = "/var/run"
 176         LOCKDIR = "/var/lock/subsys"
 177         filter_fn = lambda fs: filter(lambda f: f != 'utmp', fs)
 178         garbage = reduce((lambda (out, ff), (dir, subdirs, files):
 179                           (out + map((dir + "/").__add__, ff(files)),
 180                            lambda fs: fs)),
 181                          list(os.walk(RUNDIR)),
 182                          ([], filter_fn))[0]
 183         garbage += filter(os.path.isfile, map((LOCKDIR + "/").__add__,
 184                                               os.listdir(LOCKDIR)))
 185         for f in garbage:
 186             os.unlink(f)
 187
 188         # set the initial runlevel
 189         f = open(RUNDIR + "/utmp", "w")
 190         utmp.set_runlevel(f, runlevel)
 191         f.close()
 192
 193         # mount /proc and /dev/pts
 194         self.__do_mount("none", "/proc", "proc")
 195         # XXX - magic mount options
 196         self.__do_mount("none", "/dev/pts", "devpts", 0, "gid=5,mode=0620")
 197
 198     def __do_mount(self, *mount_args):
 199
 200         try:
 201             mountimpl.mount(*mount_args)
 202         except OSError, ex:
 203             if ex.errno == errno.EBUSY:
 204                 # assume already mounted
 205                 return
 206             raise ex
 207
 208     def enter(self):
 209
 210         state_file = open("/var/run/vservers/%s.ctx" % self.name, "w")
 211         self.__do_chroot()
 212         self.__do_chcontext(state_file)
 213
 214     def start(self, wait, runlevel = 3):
 215
 216         child_pid = os.fork()
 217         if child_pid == 0:
 218             # child process
 219             try:
 220                 # get a new session
 221                 os.setsid()
 222
 223                 # open state file to record vserver info
 224                 state_file = open("/var/run/vservers/%s.ctx" % self.name, "w")
 225
 226                 # use /dev/null for stdin, /var/log/boot.log for stdout/err
 227                 os.close(0)
 228                 os.close(1)
 229                 os.open("/dev/null", os.O_RDONLY)
 230                 self.__do_chroot()
 231                 log = open("/var/log/boot.log", "w", 0)
 232                 os.dup2(1, 2)
 233
 234                 print >>log, ("%s: starting the virtual server %s" %
 235                               (time.asctime(time.gmtime()), self.name))
 236
 237                 # perform pre-init cleanup
 238                 self.__prep(runlevel, log)
 239
 240                 # execute each init script in turn
 241                 # XXX - we don't support all scripts that vserver script does
 242                 cmd_pid = 0
 243                 for cmd in self.INITSCRIPTS + [None]:
 244                     # wait for previous command to terminate, unless it
 245                     # is the last one and the caller has specified to wait
 246                     if cmd_pid and (cmd != None or wait):
 247                         try:
 248                             os.waitpid(cmd_pid, 0)
 249                         except:
 250                             print >>log, "error waiting for %s:" % cmd_pid
 251                             traceback.print_exc()
 252
 253                     # end of list
 254                     if cmd == None:
 255                         os._exit(0)
 256
 257                     # fork and exec next command
 258                     cmd_pid = os.fork()
 259                     if cmd_pid == 0:
 260                         try:
 261                             # enter vserver context
 262                             self.__do_chcontext(state_file)
 263                             arg_subst = { 'runlevel': runlevel }
 264                             cmd_args = [cmd[0]] + map(lambda x: x % arg_subst,
 265                                                       cmd[1:])
 266                             print >>log, "executing '%s'" % " ".join(cmd_args)
 267                             os.execl(cmd[0], *cmd_args)
 268                         except:
 269                             traceback.print_exc()
 270                             os._exit(1)
 271                     else:
 272                         # don't want to write state_file multiple times
 273                         state_file = None
 274
 275             # we get here due to an exception in the top-level child process
 276             except Exception, ex:
 277                 traceback.print_exc()
 278             os._exit(0)
 279
 280         # parent process
 281         return child_pid