# Copyright 2005 Princeton University

import errno
import fcntl
import os
import re

import linuxcaps
import passfdimpl

from vserver_vars import *

CAP_SAFE = (linuxcaps.CAP_CHOWN |
            linuxcaps.CAP_DAC_OVERRIDE |
            linuxcaps.CAP_DAC_READ_SEARCH |
            linuxcaps.CAP_FOWNER |
            linuxcaps.CAP_FSETID |
            linuxcaps.CAP_KILL |
            linuxcaps.CAP_SETGID |
            linuxcaps.CAP_SETUID |
            linuxcaps.CAP_SETPCAP |
            linuxcaps.CAP_SYS_TTY_CONFIG |
            linuxcaps.CAP_LEASE |
            linuxcaps.CAP_SYS_CHROOT |
            linuxcaps.CAP_SYS_PTRACE)

#
# XXX - these are the flags taken from chcontext.c, but they don't match
# up with those apparently used by the kernel
#
FLAGS_LOCK = 1
FLAGS_SCHED = 2
FLAGS_NPROC = 4
FLAGS_PRIVATE = 8
FLAGS_FAKEINIT = 16
FLAGS_HIDEINFO = 32
FLAGS_ULIMIT = 64


              
class VServer:

    def __init__(self, name):

        self.name = name
        self.config = self.__read_config_file("/etc/vservers.conf")
        self.config.update(self.__read_config_file("/etc/vservers/%s.conf" %
                                                   self.name))
        self.flags = 0
        flags = self.config["S_FLAGS"].split(" ")
        if "lock" in flags:
            self.flags |= FLAGS_LOCK
        if "nproc" in flags:
            self.flags |= FLAGS_NPROC
        self.remove_caps = ~CAP_SAFE
        print "%x %x" % (self.flags, ~self.remove_caps)

    config_var_re = re.compile(r"^ *([A-Z_]+)=(.*)\n?$", re.MULTILINE)

    def __read_config_file(self, filename):

        f = open(filename, "r")
        data = f.read()
        f.close()
        config = {}
        for m in self.config_var_re.finditer(data):
            (key, val) = m.groups()
            config[key] = val.strip('"')
        return config

    def open(self, filename, mode = "r"):

        (sendsock, recvsock) = passfdimpl.socketpair()
        child_pid = os.fork()
        if child_pid == 0:
            try:
                # child process
                os.chroot("%s/%s" % (VROOTDIR, self.name))
                f = open(filename, mode)
                passfdimpl.sendmsg(f.fileno(), sendsock)
                os._exit(0)
            except EnvironmentError, ex:
                (result, errmsg) = (ex.errno, ex.strerror)
            except Exception, ex:
                (result, errmsg) = (255, str(ex))
            os.write(sendsock, errmsg)
            os._exit(result)

        # parent process

        # XXX - need this since a lambda can't raise an exception
        def __throw(ex):
            raise ex

        os.close(sendsock)
        throw = lambda : __throw(Exception(errmsg))
        while True:
            try:
                (pid, status) = os.waitpid(child_pid, 0)
                if os.WIFEXITED(status):
                    result = os.WEXITSTATUS(status)
                    if result != 255:
                        errmsg = os.strerror(result)
                        throw = lambda : __throw(IOError(result, errmsg))
                    else:
                        errmsg = "unexpected exception in child"
                else:
                    result = -1
                    errmsg = "child killed"
                break
            except OSError, ex:
                if ex.errno != errno.EINTR:
                    os.close(recvsock)
                    raise ex
        fcntl.fcntl(recvsock, fcntl.F_SETFL, os.O_NONBLOCK)
        try:
            (fd, errmsg) = passfdimpl.recvmsg(recvsock)
        except OSError, ex:
            if ex.errno != errno.EAGAIN:
                throw = lambda : __throw(ex)
            fd = 0
        os.close(recvsock)
        if not fd:
            throw()

        return os.fdopen(fd)