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#

# Copyright (C) 2009, Google Inc.

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# This program is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; either version 2 of the License, or

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# This program is distributed in the hope that it will be useful, but

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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

# General Public License for more details.

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# You should have received a copy of the GNU General Public License

# along with this program; if not, write to the Free Software

# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

# 02110-1301, USA.

"""Ganeti configuration daemon server library.

Ganeti-confd is a daemon to query master candidates for configuration values.

It uses UDP+HMAC for authentication with a global cluster key.

"""

import logging

import time

from ganeti import constants

from ganeti import objects

from ganeti import errors

from ganeti import utils

from ganeti import serializer

from ganeti import ssconf

from ganeti.confd import querylib

class ConfdProcessor(object):

  """A processor for confd requests.

  @ivar reader: confd SimpleConfigReader

  @ivar disabled: whether confd serving is disabled

  """

  DISPATCH_TABLE = {

    constants.CONFD_REQ_PING: querylib.PingQuery,

    constants.CONFD_REQ_NODE_ROLE_BYNAME: querylib.NodeRoleQuery,

    constants.CONFD_REQ_NODE_PIP_BY_INSTANCE_IP:

      querylib.InstanceIpToNodePrimaryIpQuery,

    constants.CONFD_REQ_CLUSTER_MASTER: querylib.ClusterMasterQuery,

    constants.CONFD_REQ_NODE_PIP_LIST: querylib.NodesPipsQuery,

    constants.CONFD_REQ_MC_PIP_LIST: querylib.MasterCandidatesPipsQuery,

    constants.CONFD_REQ_INSTANCES_IPS_LIST: querylib.InstancesIpsQuery,

    }

  def __init__(self):

    """Constructor for ConfdProcessor

    """

    self.disabled = True

    self.hmac_key = utils.ReadFile(constants.CONFD_HMAC_KEY)

    self.reader = None

    assert \

      not constants.CONFD_REQS.symmetric_difference(self.DISPATCH_TABLE), \

      "DISPATCH_TABLE is unaligned with CONFD_REQS"

  def Enable(self):

    try:

      self.reader = ssconf.SimpleConfigReader()

      self.disabled = False

    except errors.ConfigurationError:

      self.disabled = True

      raise

  def Disable(self):

    self.disabled = True

    self.reader = None

  def ExecQuery(self, payload_in, ip, port):

    """Process a single UDP request from a client.

    @type payload_in: string

    @param payload_in: request raw data

    @type ip: string

    @param ip: source ip address

    @param port: integer

    @type port: source port

    """

    if self.disabled:

      logging.debug('Confd is disabled. Ignoring query.')

      return

    try:

      request = self.ExtractRequest(payload_in)

      reply, rsalt = self.ProcessRequest(request)

      payload_out = self.PackReply(reply, rsalt)

      return payload_out

    except errors.ConfdRequestError, err:

      logging.info('Ignoring broken query from %s:%d: %s', ip, port, err)

      return None

  def ExtractRequest(self, payload):

    """Extracts a ConfdRequest object from a serialized hmac signed string.

    This functions also performs signature/timestamp validation.

    """

    current_time = time.time()

    logging.debug("Extracting request with size: %d", len(payload))

    try:

      (message, salt) = serializer.LoadSigned(payload, self.hmac_key)

    except errors.SignatureError, err:

      msg = "invalid signature: %s" % err

      raise errors.ConfdRequestError(msg)

    try:

      message_timestamp = int(salt)

    except (ValueError, TypeError):

      msg = "non-integer timestamp: %s" % salt

      raise errors.ConfdRequestError(msg)

    skew = abs(current_time - message_timestamp)

    if skew > constants.CONFD_MAX_CLOCK_SKEW:

      msg = "outside time range (skew: %d)" % skew

      raise errors.ConfdRequestError(msg)

    try:

      request = objects.ConfdRequest.FromDict(message)

    except AttributeError, err:

      raise errors.ConfdRequestError('%s' % err)

    return request

  def ProcessRequest(self, request):

    """Process one ConfdRequest request, and produce an answer

    @type request: L{objects.ConfdRequest}

    @rtype: (L{objects.ConfdReply}, string)

    @return: tuple of reply and salt to add to the signature

    """

    logging.debug("Processing request: %s", request)

    if request.protocol != constants.CONFD_PROTOCOL_VERSION:

      msg = "wrong protocol version %d" % request.protocol

      raise errors.ConfdRequestError(msg)

    if request.type not in constants.CONFD_REQS:

      msg = "wrong request type %d" % request.type

      raise errors.ConfdRequestError(msg)

    rsalt = request.rsalt

    if not rsalt:

      msg = "missing requested salt"

      raise errors.ConfdRequestError(msg)

    query_object = self.DISPATCH_TABLE[request.type](self.reader)

    status, answer = query_object.Exec(request.query)

    reply = objects.ConfdReply(

              protocol=constants.CONFD_PROTOCOL_VERSION,

              status=status,

              answer=answer,

              serial=self.reader.GetConfigSerialNo(),

              )

    logging.debug("Sending reply: %s", reply)

    return (reply, rsalt)

  def PackReply(self, reply, rsalt):

    """Serialize and sign the given reply, with salt rsalt

    @type reply: L{objects.ConfdReply}

    @type rsalt: string

    """

    return serializer.DumpSigned(reply.ToDict(), self.hmac_key, rsalt)