python/vserver.py

   1 # Copyright 2005 Princeton University
   2
   3 import errno
   4 import fcntl
   5 import os
   6 import re
   7 import traceback
   8
   9 import linuxcaps
  10 import passfdimpl
  11 import vserverimpl
  12
  13 from util_vserver_vars import *
  14
  15 CAP_SAFE = (linuxcaps.CAP_CHOWN |
  16             linuxcaps.CAP_DAC_OVERRIDE |
  17             linuxcaps.CAP_DAC_READ_SEARCH |
  18             linuxcaps.CAP_FOWNER |
  19             linuxcaps.CAP_FSETID |
  20             linuxcaps.CAP_KILL |
  21             linuxcaps.CAP_SETGID |
  22             linuxcaps.CAP_SETUID |
  23             linuxcaps.CAP_SETPCAP |
  24             linuxcaps.CAP_SYS_TTY_CONFIG |
  25             linuxcaps.CAP_LEASE |
  26             linuxcaps.CAP_SYS_CHROOT |
  27             linuxcaps.CAP_SYS_PTRACE)
  28
  29 #
  30 # these are the flags taken from the kernel linux/vserver/legacy.h
  31 #
  32 FLAGS_LOCK = 1
  33 FLAGS_SCHED = 2  # XXX - defined in util-vserver/src/chcontext.c
  34 FLAGS_NPROC = 4
  35 FLAGS_PRIVATE = 8
  36 FLAGS_INIT = 16
  37 FLAGS_HIDEINFO = 32
  38 FLAGS_ULIMIT = 64
  39 FLAGS_NAMESPACE = 128
  40
  41
  42
  43 class VServer:
  44
  45     INITSCRIPTS = [('/etc/rc.vinit', 'start'), ('/etc/rc.d/rc', '3')]
  46
  47     def __init__(self, name):
  48
  49         self.name = name
  50         self.config = self.__read_config_file("/etc/vservers.conf")
  51         self.config.update(self.__read_config_file("/etc/vservers/%s.conf" %
  52                                                    self.name))
  53         self.flags = 0
  54         flags = self.config["S_FLAGS"].split(" ")
  55         if "lock" in flags:
  56             self.flags |= FLAGS_LOCK
  57         if "nproc" in flags:
  58             self.flags |= FLAGS_NPROC
  59         self.remove_caps = ~CAP_SAFE
  60         self.ctx = int(self.config["S_CONTEXT"])
  61
  62     config_var_re = re.compile(r"^ *([A-Z_]+)=(.*)\n?$", re.MULTILINE)
  63
  64     def __read_config_file(self, filename):
  65
  66         f = open(filename, "r")
  67         data = f.read()
  68         f.close()
  69         config = {}
  70         for m in self.config_var_re.finditer(data):
  71             (key, val) = m.groups()
  72             config[key] = val.strip('"')
  73         return config
  74
  75     def __do_chroot(self):
  76
  77         return os.chroot("%s/%s" % (VROOTDIR, self.name))
  78
  79     def open(self, filename, mode = "r"):
  80
  81         (sendsock, recvsock) = passfdimpl.socketpair()
  82         child_pid = os.fork()
  83         if child_pid == 0:
  84             try:
  85                 # child process
  86                 self.__do_chroot()
  87                 f = open(filename, mode)
  88                 passfdimpl.sendmsg(f.fileno(), sendsock)
  89                 os._exit(0)
  90             except EnvironmentError, ex:
  91                 (result, errmsg) = (ex.errno, ex.strerror)
  92             except Exception, ex:
  93                 (result, errmsg) = (255, str(ex))
  94             os.write(sendsock, errmsg)
  95             os._exit(result)
  96
  97         # parent process
  98
  99         # XXX - need this since a lambda can't raise an exception
 100         def __throw(ex):
 101             raise ex
 102
 103         os.close(sendsock)
 104         throw = lambda : __throw(Exception(errmsg))
 105         while True:
 106             try:
 107                 (pid, status) = os.waitpid(child_pid, 0)
 108                 if os.WIFEXITED(status):
 109                     result = os.WEXITSTATUS(status)
 110                     if result != 255:
 111                         errmsg = os.strerror(result)
 112                         throw = lambda : __throw(IOError(result, errmsg))
 113                     else:
 114                         errmsg = "unexpected exception in child"
 115                 else:
 116                     result = -1
 117                     errmsg = "child killed"
 118                 break
 119             except OSError, ex:
 120                 if ex.errno != errno.EINTR:
 121                     os.close(recvsock)
 122                     raise ex
 123         fcntl.fcntl(recvsock, fcntl.F_SETFL, os.O_NONBLOCK)
 124         try:
 125             (fd, errmsg) = passfdimpl.recvmsg(recvsock)
 126         except OSError, ex:
 127             if ex.errno != errno.EAGAIN:
 128                 throw = lambda : __throw(ex)
 129             fd = 0
 130         os.close(recvsock)
 131         if not fd:
 132             throw()
 133
 134         return os.fdopen(fd)
 135
 136     def enter(self):
 137
 138         state_file = open("/var/run/vservers/%s.ctx" % self.name, "w")
 139         self.__do_chroot()
 140         vserverimpl.chcontext(self.ctx, self.remove_caps)
 141         print >>state_file, "S_CONTEXT=%d" % self.ctx
 142         print >>state_file, "S_PROFILE=%s" % self.config.get("S_PROFILE", "")
 143         state_file.close()
 144
 145     def start(self):
 146
 147         child_pid = os.fork()
 148         if child_pid == 0:
 149             # child process
 150             try:
 151                 # get a new session
 152                 os.setsid()
 153
 154                 # enter vserver context
 155                 self.enter()
 156
 157                 # use /dev/null for stdin, /var/log/boot.log for stdout/err
 158                 os.close(0)
 159                 os.close(1)
 160                 os.open("/dev/null", os.O_RDONLY)
 161                 os.open("/var/log/boot.log",
 162                         os.O_WRONLY | os.O_CREAT | os.O_TRUNC)
 163                 os.dup2(1, 2)
 164
 165                 # write same output that vserver script does
 166                 os.write(1, "Starting the virtual server %s\n" % self.name)
 167                 os.write(1, "Server %s is not running\n" % self.name)
 168
 169                 # execute each init script in turn
 170                 # XXX - we don't support all the possible scripts
 171                 for cmd in self.INITSCRIPTS:
 172                     os.spawnl(os.P_WAIT, *cmd)
 173             except Exception, ex:
 174                 traceback.print_exc()
 175             os._exit(0)
 176
 177         # parent process
 178         return child_pid