Initial commit

2021-01-24 19:51:48 +01:00
commit 42c1c5fa66
13 changed files with 1003 additions and 0 deletions
@@ -0,0 +1,148 @@
+from enum import Enum
+import ipaddress
+import json
+import struct
+import binascii
+import os
+from os import path
+from select import select
+import threading
+import subprocess
+import logging
+
+from eventfd import EventFD
+import posix_ipc
+
+HANDLER_SCRIPT = path.join(path.dirname(__file__), 'udhcpc_handler.py')
+AWAIT_INTERVAL = 0.1
+VENDOR_ID = 'docker'
+
+class EventType(Enum):
+    BOUND = 'bound'
+    RENEW = 'renew'
+    DECONFIG = 'deconfig'
+    LEASEFAIL = 'leasefail'
+
+logger = logging.getLogger('net-dhcp')
+
+class DHCPClientError(Exception):
+    pass
+
+def _nspopen_wrapper(netns):
+    return lambda cmd, *args, **kwargs: subprocess.Popen(['nsenter', f'-n{netns}', '--'] + cmd, *args, **kwargs)
+class DHCPClient:
+    def __init__(self, iface, v6=False, once=False, hostname=None, event_listener=None):
+        self.iface = iface
+        self.v6 = v6
+        self.once = once
+        self.event_listeners = [DHCPClient._attr_listener]
+        if event_listener:
+            self.event_listeners.append(event_listener)
+
+        self.netns = None
+        if isinstance(iface, dict):
+            self.netns = iface['netns']
+            logger.debug('udhcpc using netns %s', self.netns)
+
+        Popen = _nspopen_wrapper(self.netns) if self.netns else subprocess.Popen
+        bin_path = '/usr/bin/udhcpc6' if v6 else '/sbin/udhcpc'
+        cmdline = [bin_path, '-s', HANDLER_SCRIPT, '-i', iface['ifname'], '-f']
+        cmdline.append('-q' if once else '-R')
+        if hostname:
+            cmdline.append('-x')
+            if v6:
+                # TODO: We encode the fqdn for DHCPv6 because udhcpc6 seems to be broken
+                # flags: S bit set (see RFC4704)
+                enc_hostname = hostname.encode('utf-8')
+                enc_hostname = struct.pack('BB', 0b0001, len(enc_hostname)) + enc_hostname
+                enc_hostname = binascii.hexlify(enc_hostname).decode('ascii')
+                hostname_opt = f'0x27:{enc_hostname}'
+            else:
+                hostname_opt = f'hostname:{hostname}'
+            cmdline.append(hostname_opt)
+        if not v6:
+            cmdline += ['-V', VENDOR_ID]
+
+        self._suffix = '6' if v6 else ''
+        self._event_queue = posix_ipc.MessageQueue(f'/udhcpc{self._suffix}_{iface["address"].replace(":", "_")}', \
+            flags=os.O_CREAT | os.O_EXCL, max_messages=2, max_message_size=1024)
+        self.proc = Popen(cmdline, env={'EVENT_QUEUE': self._event_queue.name}, stdin=subprocess.DEVNULL,
+            stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
+        if hostname:
+            logger.debug('[udhcpc%s#%d] using hostname "%s"', self._suffix, self.proc.pid, hostname)
+
+        self._has_lease = threading.Event()
+        self.ip = None
+        self.gateway = None
+        self.domain = None
+
+        self._shutdown_event = EventFD()
+        self.shutdown = False
+        self._event_thread = threading.Thread(target=self._read_events)
+        self._event_thread.start()
+
+    def _attr_listener(self, event_type, event):
+        if event_type in (EventType.BOUND, EventType.RENEW):
+            self.ip = ipaddress.ip_interface(event['ip'])
+            if 'gateway' in event:
+                self.gateway = ipaddress.ip_address(event['gateway'])
+            else:
+                self.gateway = None
+            self.domain = event.get('domain')
+            self._has_lease.set()
+        elif event_type == EventType.DECONFIG:
+            self._has_lease.clear()
+            self.ip = None
+            self.gateway = None
+            self.domain = None
+
+    def _read_events(self):
+        while True:
+            r, _w, _e = select([self._shutdown_event, self._event_queue.mqd], [], [])
+            if self._shutdown_event in r:
+                break
+
+            msg, _priority = self._event_queue.receive()
+            event = json.loads(msg.decode('utf-8'))
+            try:
+                event['type'] = EventType(event['type'])
+            except ValueError:
+                logger.warning('udhcpc%s#%d unknown event "%s"', self._suffix, self.proc.pid, event)
+                continue
+
+            logger.debug('[udhcp%s#%d event] %s', self._suffix, self.proc.pid, event)
+            for listener in self.event_listeners:
+                try:
+                    listener(self, event['type'], event)
+                except Exception as ex:
+                    logger.exception(ex)
+        self.shutdown = True
+        del self._shutdown_event
+
+    def await_ip(self, timeout=10):
+        if not self._has_lease.wait(timeout=timeout):
+            raise DHCPClientError(f'Timed out waiting for lease from udhcpc{self._suffix}')
+
+        return self.ip
+
+    def finish(self, timeout=5):
+        if self.shutdown or self._shutdown_event.is_set():
+            return
+
+        try:
+            if self.proc.returncode is not None and (not self.once or self.proc.returncode != 0):
+                raise DHCPClientError(f'udhcpc{self._suffix} exited early with code {self.proc.returncode}')
+            if self.once:
+                self.await_ip()
+            else:
+                self.proc.terminate()
+
+            if self.proc.wait(timeout=timeout) != 0:
+                raise DHCPClientError(f'udhcpc{self._suffix} exited with non-zero exit code {self.proc.returncode}')
+
+            return self.ip
+        finally:
+            self._shutdown_event.set()
+            self._event_thread.join()
+            self._event_queue.close()
+            self._event_queue.unlink()