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✏️ criu.py

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# Same as libcriu for C.

import socket
import errno
import fcntl
import os
import struct

import pycriu.rpc_pb2 as rpc

class _criu_comm:
    """
    Base class for communication classes.
    """
    COMM_SK = 0
    COMM_FD = 1
    COMM_BIN = 2
    comm_type = None
    comm = None
    sk = None

def connect(self, daemon):
        """
        Connect to criu and return socket object.
        daemon -- is for whether or not criu should daemonize if executing criu from binary(comm_bin).
        """
        pass

def disconnect(self):
        """
        Disconnect from criu.
        """
        pass

class _criu_comm_sk(_criu_comm):
    """
    Communication class for unix socket.
    """

def __init__(self, sk_path):
        self.comm_type = self.COMM_SK
        self.comm = sk_path

def connect(self, daemon):
        self.sk = socket.socket(socket.AF_UNIX, socket.SOCK_SEQPACKET)
        self.sk.connect(self.comm)

return self.sk

def disconnect(self):
        self.sk.close()

class _criu_comm_fd(_criu_comm):
    """
    Communication class for file descriptor.
    """

def __init__(self, fd):
        self.comm_type = self.COMM_FD
        self.comm = fd

def connect(self, daemon):
        self.sk = socket.fromfd(self.comm, socket.AF_UNIX,
                                socket.SOCK_SEQPACKET)

return self.sk

def disconnect(self):
        self.sk.close()

class _criu_comm_bin(_criu_comm):
    """
    Communication class for binary.
    """

def __init__(self, bin_path):
        self.comm_type = self.COMM_BIN
        self.comm = bin_path
        self.swrk = None
        self.daemon = None

def connect(self, daemon):
        # Kind of the same thing we do in libcriu
        css = socket.socketpair(socket.AF_UNIX, socket.SOCK_SEQPACKET)
        flags = fcntl.fcntl(css[1], fcntl.F_GETFD)
        fcntl.fcntl(css[1], fcntl.F_SETFD, flags | fcntl.FD_CLOEXEC)
        flags = fcntl.fcntl(css[0], fcntl.F_GETFD)
        fcntl.fcntl(css[0], fcntl.F_SETFD, flags & ~fcntl.FD_CLOEXEC)

self.daemon = daemon

p = os.fork()

if p == 0:

def exec_criu():
                os.close(0)
                os.close(1)
                os.close(2)

css[0].send(struct.pack('i', os.getpid()))
                os.execv(self.comm,
                         [self.comm, 'swrk',
                          "%d" % css[0].fileno()])
                os._exit(1)

if daemon:
                # Python has no daemon(3) alternative,
                # so we need to mimic it ourself.
                p = os.fork()

if p == 0:
                    os.setsid()

exec_criu()
                else:
                    os._exit(0)
            else:
                exec_criu()
        else:
            if daemon:
                os.waitpid(p, 0)

css[0].close()
        self.swrk = struct.unpack('i', css[1].recv(4))[0]
        self.sk = css[1]

return self.sk

def disconnect(self):
        self.sk.close()
        if not self.daemon:
            os.waitpid(self.swrk, 0)

class CRIUException(Exception):
    """
    Exception class for handling and storing criu errors.
    """
    typ = None
    _str = None

def __str__(self):
        return self._str

class CRIUExceptionInternal(CRIUException):
    """
    Exception class for handling and storing internal errors.
    """

def __init__(self, typ, s):
        self.typ = typ
        self._str = "%s failed with internal error: %s" % (
            rpc.criu_req_type.Name(self.typ), s)

class CRIUExceptionExternal(CRIUException):
    """
    Exception class for handling and storing criu RPC errors.
    """

def __init__(self, req_typ, resp_typ, errno):
        self.typ = req_typ
        self.resp_typ = resp_typ
        self.errno = errno
        self._str = self._gen_error_str()

def _gen_error_str(self):
        s = "%s failed: " % (rpc.criu_req_type.Name(self.typ), )

if self.typ != self.resp_typ:
            s += "Unexpected response type %d: " % (self.resp_typ, )

s += "Error(%d): " % (self.errno, )

if self.errno == errno.EBADRQC:
            s += "Bad options"

if self.typ == rpc.DUMP:
            if self.errno == errno.ESRCH:
                s += "No process with such pid"

if self.typ == rpc.RESTORE:
            if self.errno == errno.EEXIST:
                s += "Process with requested pid already exists"

s += "Unknown"

return s

class criu:
    """
    Call criu through RPC.
    """
    opts = None  #CRIU options in pb format

_comm = None  #Communication method

def __init__(self):
        self.use_binary('criu')
        self.opts = rpc.criu_opts()
        self.sk = None

def use_sk(self, sk_name):
        """
        Access criu using unix socket which that belongs to criu service daemon.
        """
        self._comm = _criu_comm_sk(sk_name)

def use_fd(self, fd):
        """
        Access criu using provided fd.
        """
        self._comm = _criu_comm_fd(fd)

def use_binary(self, bin_name):
        """
        Access criu by execing it using provided path to criu binary.
        """
        self._comm = _criu_comm_bin(bin_name)

def _send_req_and_recv_resp(self, req):
        """
        As simple as send request and receive response.
        """
        # In case of self-dump we need to spawn criu swrk detached
        # from our current process, as criu has a hard time separating
        # process resources from its own if criu is located in a same
        # process tree it is trying to dump.
        daemon = False
        if req.type == rpc.DUMP and not req.opts.HasField('pid'):
            daemon = True

try:
            if not self.sk:
                s = self._comm.connect(daemon)
            else:
                s = self.sk

if req.keep_open:
                self.sk = s

s.send(req.SerializeToString())

buf = s.recv(len(s.recv(1, socket.MSG_TRUNC | socket.MSG_PEEK)))

if not req.keep_open:
                self._comm.disconnect()

resp = rpc.criu_resp()
            resp.ParseFromString(buf)
        except Exception as e:
            raise CRIUExceptionInternal(req.type, str(e))

return resp

def check(self):
        """
        Checks whether the kernel support is up-to-date.
        """
        req = rpc.criu_req()
        req.type = rpc.CHECK

resp = self._send_req_and_recv_resp(req)