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ip_allocator_dhcp.py
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ip_allocator_dhcp.py
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"""
Copyright 2020 The Magma Authors.
This source code is licensed under the BSD-style license found in the
LICENSE file in the root directory of this source tree.
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
Allocates IP address as per DHCP server in the uplink network.
"""
from __future__ import (
absolute_import,
division,
print_function,
unicode_literals,
)
import json
import logging
import subprocess
import tempfile
import threading
from copy import deepcopy
from datetime import datetime
from ipaddress import IPv4Network, ip_address, ip_network
from threading import Condition
from typing import Any, Dict, List, Optional
from magma.mobilityd.ip_descriptor import IPDesc, IPState, IPType
from .dhcp_desc import DHCPDescriptor, DHCPState
from .ip_allocator_base import IPAllocator, NoAvailableIPError
from .mac import MacAddress, create_mac_from_sid
from .mobility_store import MobilityStore
from .utils import IPAddress, IPNetwork
DEFAULT_DHCP_REQUEST_RETRY_FREQUENCY = 10
DEFAULT_DHCP_REQUEST_RETRY_DELAY = 1
LEASE_RENEW_WAIT_MIN = 200
DHCP_HELPER_CLI = "dhcp_helper_cli.py"
LOG = logging.getLogger('mobilityd.dhcp.alloc')
DHCP_ACTIVE_STATES = [DHCPState.ACK, DHCPState.OFFER]
class IPAllocatorDHCP(IPAllocator):
MAX_DHCP_PROCS: int = 3
dhcp_helper_procs: List[subprocess.Popen] = []
def __init__(
self, store: MobilityStore, retry_limit: int = 300, start: bool = True,
iface: str = "eth2", lease_renew_wait_min: float = LEASE_RENEW_WAIT_MIN, # TODO read this from config file
) -> None:
"""
Allocate IP address for SID using DHCP server.
SID is mapped to MAC address using function defined in mac.py
then this mac address used in DHCP request to allocate new IP
from DHCP server.
This IP is also cached to improve performance in case of
reallocation for same SID in short period of time.
Args:
store: Moblityd storage instance
retry_limit: try DHCP request
iface: DHCP interface.
"""
self._store = store
self.dhcp_wait = Condition()
self._retry_limit = retry_limit # default wait for two minutes
self._iface = iface
self._lease_renew_wait_min = lease_renew_wait_min
self._monitor_thread: Optional[threading.Thread] = threading.Thread(
target=self._monitor_dhcp_state,
daemon=True,
)
self._monitor_thread_event = threading.Event()
if start:
self.start_monitor_thread()
def start_monitor_thread(self) -> None:
if self._monitor_thread is None:
self._monitor_thread = threading.Thread(
target=self._monitor_dhcp_state,
daemon=True,
)
self._monitor_thread.start()
def stop_monitor_thread(self, join: bool = False, reset: bool = False) -> None:
self._monitor_thread_event.set()
if join and self._monitor_thread:
self._monitor_thread.join()
if reset:
self._monitor_thread = None
self._monitor_thread_event.clear()
def _monitor_dhcp_state(self) -> None:
"""
monitor DHCP client state.
"""
while True:
wait_time = self._lease_renew_wait_min
with self.dhcp_wait:
for _, dhcp_desc in self._store.dhcp_store.items():
logging.debug("monitor: %s", dhcp_desc)
# Only process active records.
if dhcp_desc.state not in DHCP_ACTIVE_STATES:
continue
now = datetime.now()
logging.debug("monitor time: %s", now)
if now >= dhcp_desc.lease_expiration_time:
logging.debug("sending lease allocate")
with tempfile.NamedTemporaryFile() as tmpfile:
call_args = [
DHCP_HELPER_CLI,
"--mac", str(dhcp_desc.mac),
"--vlan", str(dhcp_desc.vlan),
"--interface", self._iface,
"--save-file", tmpfile.name,
"--json",
"allocate",
]
dhcp_cli_response = self._get_dhcp_helper_cli_response(call_args, tmpfile.name)
self._parse_dhcp_helper_cli_response_to_store(
dhcp_desc=dhcp_desc, dhcp_response=dhcp_cli_response,
mac=dhcp_desc.mac, vlan=dhcp_desc.vlan,
)
elif now >= dhcp_desc.lease_renew_deadline:
logging.debug("sending lease renewal")
with tempfile.NamedTemporaryFile() as tmpfile:
call_args = [
DHCP_HELPER_CLI,
"--mac", str(dhcp_desc.mac),
"--vlan", str(dhcp_desc.vlan),
"--interface", self._iface,
"--save-file", tmpfile.name,
"--json",
"renew",
"--ip", str(dhcp_desc.ip),
"--server-ip", str(dhcp_desc.server_ip),
]
dhcp_cli_response = self._get_dhcp_helper_cli_response(call_args, tmpfile.name)
self._parse_dhcp_helper_cli_response_to_store(
dhcp_desc=dhcp_desc, dhcp_response=dhcp_cli_response,
mac=dhcp_desc.mac, vlan=dhcp_desc.vlan,
)
else:
time_to_renew = dhcp_desc.lease_renew_deadline - now
wait_time = min(
wait_time, time_to_renew.total_seconds(),
)
# default in wait is 30 sec
logging.debug("lease renewal check after: %s sec", wait_time)
self._monitor_thread_event.wait(wait_time)
if self._monitor_thread_event.is_set():
break
def add_ip_block(self, ipblock: IPNetwork) -> None:
logging.warning(
"No need to allocate block for DHCP allocator: %s",
ipblock,
)
def remove_ip_blocks(
self, ipblocks: List[IPNetwork],
force: bool = False,
) -> List[IPNetwork]:
""" Makes the indicated block(s) unavailable for allocation
If force is False, blocks that have any addresses currently allocated
will not be removed. Otherwise, if force is True, the indicated blocks
will be removed regardless of whether any addresses have been allocated
and any allocated addresses will no longer be served.
Removing a block entails removing the IP addresses within that block
from the internal state machine.
Args:
ipblocks (ipaddress.ip_network): variable number of objects of type
ipaddress.ip_network, representing the blocks that are intended
to be removed. The blocks should have been explicitly added and
not yet removed. Any blocks that are not active in the IP
allocator will be ignored with a warning.
force (bool): whether to forcibly remove the blocks indicated. If
False, will only remove a block if no addresses from within the
block have been allocated. If True, will remove all blocks
regardless of whether any addresses have been allocated from
them.
Returns a set of the blocks that have been successfully removed.
"""
remove_blocks = set(ipblocks) & self._store.assigned_ip_blocks
logging.debug(
"Current assigned IP blocks: %s",
self._store.assigned_ip_blocks,
)
logging.debug("IP blocks to remove: %s", ipblocks)
extraneous_blocks = set(ipblocks) ^ remove_blocks
# check unknown ip blocks
if extraneous_blocks:
logging.warning(
"Cannot remove unknown IP block(s): %s",
extraneous_blocks,
)
del extraneous_blocks
# "soft" removal does not remove blocks which have IPs allocated
if not force:
allocated_ip_block_set = self._store.ip_state_map.get_allocated_ip_block_set()
remove_blocks -= allocated_ip_block_set
del allocated_ip_block_set
# Remove the associated IP addresses
remove_ips = (ip for block in remove_blocks for ip in block.hosts())
for ip in remove_ips:
for state in (IPState.FREE, IPState.RELEASED, IPState.REAPED):
ip_desc = self._store.ip_state_map.remove_ip_from_state(ip, state)
if ip_desc:
self._release_dhcp_ip(ip_desc)
if force:
ip_desc = self._store.ip_state_map.remove_ip_from_state(
ip,
IPState.ALLOCATED,
)
if ip_desc:
self._release_dhcp_ip(ip_desc)
else:
assert not self._store.ip_state_map.test_ip_state(
ip,
IPState.ALLOCATED,
), \
"Unexpected ALLOCATED IP %s from a soft IP block " \
"removal "
# Clean up SID maps
for sid in list(self._store.sid_ips_map):
self._store.sid_ips_map.pop(sid)
# Remove the IP blocks
self._store.assigned_ip_blocks -= remove_blocks
# Can't use generators here
remove_sids = tuple(
sid for sid in self._store.sid_ips_map
if not self._store.sid_ips_map[sid]
)
for sid in remove_sids:
self._store.sid_ips_map.pop(sid)
for block in remove_blocks:
logging.info('Removed IP block %s from IPv4 address pool', block)
return list(remove_blocks)
def list_added_ip_blocks(self) -> List[IPNetwork]:
return list(deepcopy(self._store.assigned_ip_blocks))
def list_allocated_ips(self, ipblock: IPNetwork) -> List[IPAddress]:
""" List IP addresses allocated from a given IP block
Args:
ipblock (ipaddress.ip_network): ip network to add
e.g. ipaddress.ip_network("10.0.0.0/24")
Return:
list of IP addresses (ipaddress.ip_address)
"""
return [
ip for ip in
self._store.ip_state_map.list_ips(IPState.ALLOCATED)
if ip in ipblock
]
def get_dhcp_desc_from_store(
self, mac: MacAddress,
vlan: int,
) -> Optional[DHCPDescriptor]:
"""
Get DHCP description for given MAC.
Args:
mac: Mac address of the client
vlan: vlan id if the IP allocated in a VLAN
Returns: Current DHCP info.
"""
key = mac.as_redis_key(vlan)
if key in self._store.dhcp_store:
return self._store.dhcp_store[key]
LOG.debug("lookup error for %s", str(key))
return None
def alloc_ip_address(self, sid: str, vlan_id: int) -> IPDesc:
"""
Assumption: one-to-one mappings between SID and IP.
Args:
sid (string): universal subscriber id
vlan_id: vlan of the APN
Returns:
ipaddress.ip_address: IP address allocated
Raises:
NoAvailableIPError: if run out of available IP addresses
"""
mac = create_mac_from_sid(sid)
dhcp_desc = self.get_dhcp_desc_from_store(mac, vlan_id)
LOG.debug(
"allocate IP for %s mac %s dhcp_desc %s", sid, mac,
dhcp_desc,
)
if not dhcp_desc or not dhcp_allocated_ip(dhcp_desc):
with tempfile.NamedTemporaryFile() as tmpfile:
call_args = [
DHCP_HELPER_CLI,
"--mac", str(mac),
"--vlan", str(vlan_id),
"--interface", self._iface,
"--save-file", tmpfile.name,
"--json",
"allocate",
]
dhcp_response = self._get_dhcp_helper_cli_response(call_args, tmpfile.name)
with self.dhcp_wait:
dhcp_desc = self._parse_dhcp_helper_cli_response_to_store(
dhcp_desc=dhcp_desc, dhcp_response=dhcp_response,
mac=mac, vlan=vlan_id,
)
if dhcp_desc and dhcp_desc.ip and dhcp_desc.subnet:
ip_block = ip_network(dhcp_desc.subnet)
ip_desc = IPDesc(
ip=ip_address(dhcp_desc.ip),
state=IPState.ALLOCATED,
sid=sid,
ip_block=ip_block,
ip_type=IPType.DHCP,
vlan_id=vlan_id,
)
self._store.assigned_ip_blocks.add(ip_block)
self._store.ip_state_map.add_ip_to_state(
ip=ip_address(dhcp_desc.ip),
ip_desc=ip_desc,
state=IPState.ALLOCATED,
)
return ip_desc
else:
msg = f"No available IP addresses From DHCP for SID: {sid} MAC {mac}"
raise NoAvailableIPError(msg)
def _parse_dhcp_helper_cli_response_to_store(
self, dhcp_desc: Optional[DHCPDescriptor], dhcp_response: Dict[str, Any],
mac: MacAddress, vlan: int,
) -> Optional[DHCPDescriptor]:
if dhcp_response:
dhcp_desc = DHCPDescriptor(
mac=mac,
ip=dhcp_response["ip"],
vlan=vlan,
state_requested=DHCPState.ACK,
state=DHCPState.ACK,
subnet=str(IPv4Network(dhcp_response["subnet"], strict=False)),
server_ip=ip_address(dhcp_response["server_ip"]) if dhcp_response["server_ip"] else None,
router_ip=ip_address(dhcp_response["router_ip"]) if dhcp_response["router_ip"] else None,
lease_expiration_time=int(dhcp_response["lease_expiration_time"]),
)
self._store.dhcp_store[mac.as_redis_key(vlan)] = dhcp_desc
self._store.dhcp_gw_info.update_ip(dhcp_desc.router_ip, vlan)
return dhcp_desc
@staticmethod
def _get_dhcp_helper_cli_response(call_args: List[str], save_file: str) -> Dict[str, Any]:
ret = subprocess.run(
call_args,
capture_output=True,
check=False,
)
if ret.returncode != 0:
call_str = " ".join(call_args)
logging.error(
"CLI call '%s' failed with return code %s and error %s",
call_str, ret.returncode, ret.stderr,
)
raise NoAvailableIPError('Failed to call dhcp_helper_cli.')
with open(save_file, 'r', encoding="utf-8") as f:
dhcp_response = json.load(f)
return dhcp_response
def release_ip(self, ip_desc: IPDesc) -> None:
"""
Release IP address, this involves following steps.
1. send DHCP protocol packet to release the IP.
2. update IP block list.
3. update IP from ip-state.
Args:
ip_desc: release needs following info from IPDesc.
SID used to get mac address, IP assigned to this SID,
IP block of the IP address, vlan id of the APN.
Returns: None
"""
self._release_dhcp_ip(ip_desc)
# Remove the IP from free IP list, since DHCP is the
# owner of this IP
self._store.ip_state_map.remove_ip_from_state(ip_desc.ip, IPState.FREE)
list_allocated_ips = self._store.ip_state_map.list_ips(
IPState.ALLOCATED,
)
for ipaddr in list_allocated_ips:
if ipaddr in ip_desc.ip_block:
# found the IP, do not remove this ip_block
return
ip_block_network = ip_network(ip_desc.ip_block)
if ip_block_network in self._store.assigned_ip_blocks:
self._store.assigned_ip_blocks.remove(ip_block_network)
logging.debug(
"del: _assigned_ip_blocks %s ipblock %s",
self._store.assigned_ip_blocks, ip_desc.ip_block,
)
def _release_dhcp_ip(self, ip_desc: IPDesc) -> None:
logging.info("Releasing: %s", ip_desc)
mac = create_mac_from_sid(ip_desc.sid)
vlan = ip_desc.vlan_id
dhcp_desc = self.get_dhcp_desc_from_store(mac, vlan)
logging.info("Releasing dhcp desc: %s", dhcp_desc)
if dhcp_desc:
self._deque_old_process(ip_desc)
proc = subprocess.Popen(
[
DHCP_HELPER_CLI,
"--mac", str(mac),
"--vlan", str(vlan),
"--interface", self._iface,
"release",
"--ip", str(ip_desc.ip),
"--server-ip", str(dhcp_desc.server_ip),
],
)
self.dhcp_helper_procs.insert(0, proc)
key = mac.as_redis_key(vlan)
with self.dhcp_wait:
del self._store.dhcp_store[key]
else:
LOG.error("Unallocated DHCP release for MAC: %s", mac)
def _deque_old_process(self, ip_desc: IPDesc) -> None:
while len(self.dhcp_helper_procs) >= self.MAX_DHCP_PROCS:
oldest_proc = self.dhcp_helper_procs.pop()
if oldest_proc.poll() is None:
try:
oldest_proc.wait(timeout=10)
except subprocess.TimeoutExpired:
logging.warning(
"Unable to release IP %s."
"Killing release process "
"and moving on.", ip_desc.ip,
)
oldest_proc.kill()
def dhcp_allocated_ip(dhcp_desc: DHCPDescriptor) -> bool:
return dhcp_desc.ip_is_allocated()