from __future__ import print_function
import sys, os, logging, collections, struct, json, threading, glob
+import atexit
+
logging.basicConfig(level=logging.DEBUG)
import vpp_api
def eprint(*args, **kwargs):
+ """Print critical diagnostics to stderr."""
print(*args, file=sys.stderr, **kwargs)
+def vpp_atexit(self):
+ """Clean up VPP connection on shutdown."""
+ if self.connected:
+ eprint ('Cleaning up VPP on exit')
+ self.disconnect()
+
class VPP():
+ """VPP interface.
+
+ This class provides the APIs to VPP. The APIs are loaded
+ from provided .api.json files and makes functions accordingly.
+ These functions are documented in the VPP .api files, as they
+ are dynamically created.
+
+ Additionally, VPP can send callback messages; this class
+ provides a means to register a callback function to receive
+ these messages in a background thread.
+ """
def __init__(self, apifiles = None, testmode = False):
+ """Create a VPP API object.
+
+ apifiles is a list of files containing API
+ descriptions that will be loaded - methods will be
+ dynamically created reflecting these APIs. If not
+ provided this will load the API files from VPP's
+ default install location.
+ """
self.messages = {}
self.id_names = []
self.id_msgdef = []
self.buffersize = 10000
self.connected = False
self.header = struct.Struct('>HI')
+ self.results_lock = threading.Lock()
self.results = {}
self.timeout = 5
- self.apifile = []
+ self.apifiles = []
if not apifiles:
# Pick up API definitions from default directory
apifiles = glob.glob('/usr/share/vpp/api/*.api.json')
for file in apifiles:
- self.apifile.append(file)
with open(file) as apidef_file:
api = json.load(apidef_file)
for t in api['types']:
for m in api['messages']:
self.add_message(m[0], m[1:])
+ self.apifiles = apifiles
# Basic sanity check
if len(self.messages) == 0 and not testmode:
raise ValueError(1, 'Missing JSON message definitions')
+ # Make sure we allow VPP to clean up the message rings.
+ atexit.register(vpp_atexit, self)
class ContextId(object):
+ """Thread-safe provider of unique context IDs."""
def __init__(self):
self.context = 0
+ self.lock = threading.Lock()
def __call__(self):
- self.context += 1
- return self.context
+ """Get a new unique (or, at least, not recently used) context."""
+ with self.lock:
+ self.context += 1
+ return self.context
get_context = ContextId()
def status(self):
+ """Debug function: report current VPP API status to stdout."""
print('Connected') if self.connected else print('Not Connected')
- print('Read API definitions from', self.apifile)
+ print('Read API definitions from', ', '.join(self.apifiles))
def __struct (self, t, n = None, e = -1, vl = None):
+ """Create a packing structure for a message."""
base_types = { 'u8' : 'B',
'u16' : 'H',
'u32' : 'I',
raise ValueError(1, 'Invalid message type: ' + t)
def __struct_type(self, encode, msgdef, buf, offset, kwargs):
+ """Get a message packer or unpacker."""
if encode:
return self.__struct_type_encode(msgdef, buf, offset, kwargs)
else:
def make_function(self, name, i, msgdef, multipart, async):
if (async):
- f = lambda **kwargs: (self._call_vpp_async(i, msgdef, multipart, **kwargs))
+ f = lambda **kwargs: (self._call_vpp_async(i, msgdef, **kwargs))
else:
f = lambda **kwargs: (self._call_vpp(i, msgdef, multipart, **kwargs))
args = self.messages[name]['args']
setattr(self, name, self.make_function(name, i, msgdef, multipart, async))
def _write (self, buf):
+ """Send a binary-packed message to VPP."""
if not self.connected:
raise IOError(1, 'Not connected')
return vpp_api.write(str(buf))
self.vpp_dictionary_maxid = max(self.vpp_dictionary_maxid, i)
def connect(self, name, chroot_prefix = None, async = False, rx_qlen = 32):
- msg_handler = self.msg_handler if not async else self.msg_handler_async
- if not chroot_prefix:
- rv = vpp_api.connect(name, msg_handler, rx_qlen)
+ """Attach to VPP.
+
+ name - the name of the client.
+ chroot_prefix - if VPP is chroot'ed, the prefix of the jail
+ async - if true, messages are sent without waiting for a reply
+ rx_qlen - the length of the VPP message receive queue between
+ client and server.
+ """
+ msg_handler = self.msg_handler_sync if not async else self.msg_handler_async
+ if chroot_prefix is not None:
+ rv = vpp_api.connect(name, msg_handler, rx_qlen, chroot_prefix)
else:
- rv = vpp_api.connect(name, msg_handler, rx_qlen, chroot_prefix)
+ rv = vpp_api.connect(name, msg_handler, rx_qlen)
if rv != 0:
raise IOError(2, 'Connect failed')
self.control_ping_msgdef = self.messages['control_ping']
def disconnect(self):
+ """Detach from VPP."""
rv = vpp_api.disconnect()
+ self.connected = False
return rv
def results_wait(self, context):
- return (self.results[context]['e'].wait(self.timeout))
+ """In a sync call, wait for the reply
+
+ The context ID is used to pair reply to request.
+ """
+
+ # Results is filled by the background callback. It will
+ # raise the event when the context receives a response.
+ # Given there are two threads we have to be careful with the
+ # use of results and the structures under it, hence the lock.
+ with self.results_lock:
+ result = self.results[context]
+ ev = result['e']
+
+ timed_out = not ev.wait(self.timeout)
+
+ if timed_out:
+ raise IOError(3, 'Waiting for reply timed out')
+ else:
+ with self.results_lock:
+ result = self.results[context]
+ del self.results[context]
+ return result['r']
+
+ def results_prepare(self, context, multi=False):
+ """Prep for receiving a result in response to a request msg
+
+ context - unique context number sent in request and
+ returned in reply or replies
+ multi - true if we expect multiple messages from this
+ reply.
+ """
+
+ # The event is used to indicate that all results are in
+ new_result = {
+ 'e': threading.Event(),
+ }
+ if multi:
+ # Make it clear to the BG thread it's going to see several
+ # messages; messages are stored in a results array
+ new_result['m'] = True
+ new_result['r'] = []
+
+ new_result['e'].clear()
+
+ # Put the prepped result structure into results, at which point
+ # the bg thread can also access it (hence the thread lock)
+ with self.results_lock:
+ self.results[context] = new_result
+
+ def msg_handler_sync(self, msg):
+ """Process an incoming message from VPP in sync mode.
+
+ The message may be a reply or it may be an async notification.
+ """
+ r = self.decode_incoming_msg(msg)
+ if r is None:
+ return
+
+ # If we have a context, then use the context to find any
+ # request waiting for a reply
+ context = 0
+ if hasattr(r, 'context') and r.context > 0:
+ context = r.context
- def results_prepare(self, context):
- self.results[context] = {}
- self.results[context]['e'] = threading.Event()
- self.results[context]['e'].clear()
- self.results[context]['r'] = []
+ msgname = type(r).__name__
- def results_clean(self, context):
- del self.results[context]
+ if context == 0:
+ # No context -> async notification that we feed to the callback
+ if self.event_callback:
+ self.event_callback(msgname, r)
+ else:
+ # Context -> use the results structure (carefully) to find
+ # who we're responding to and return the message to that
+ # thread
+ with self.results_lock:
+ if context not in self.results:
+ eprint('Not expecting results for this context', context, r)
+ else:
+ result = self.results[context]
+
+ #
+ # Collect results until control ping
+ #
+
+ if msgname == 'control_ping_reply':
+ # End of a multipart
+ result['e'].set()
+ elif 'm' in self.results[context]:
+ # One element in a multipart
+ result['r'].append(r)
+ else:
+ # All of a single result
+ result['r'] = r
+ result['e'].set()
- def msg_handler(self, msg):
+ def decode_incoming_msg(self, msg):
if not msg:
eprint('vpp_api.read failed')
return
i, ci = self.header.unpack_from(msg, 0)
if self.id_names[i] == 'rx_thread_exit':
- return;
+ return
#
# Decode message and returns a tuple.
raise IOError(2, 'Reply message undefined')
r = self.decode(msgdef, msg)
- if 'context' in r._asdict():
- if r.context > 0:
- context = r.context
-
- msgname = type(r).__name__
- #
- # XXX: Call provided callback for event
- # Are we guaranteed to not get an event during processing of other messages?
- # How to differentiate what's a callback message and what not? Context = 0?
- #
- #if not is_waiting_for_reply():
- if r.context == 0 and self.event_callback:
- self.event_callback(msgname, r)
- return
+ return r
- #
- # Collect results until control ping
- #
- if msgname == 'control_ping_reply':
- self.results[context]['e'].set()
- return
+ def msg_handler_async(self, msg):
+ """Process a message from VPP in async mode.
- if not context in self.results:
- eprint('Not expecting results for this context', context, r)
+ In async mode, all messages are returned to the callback.
+ """
+ r = self.decode_incoming_msg(msg)
+ if r is None:
return
- if 'm' in self.results[context]:
- self.results[context]['r'].append(r)
- return
+ msgname = type(r).__name__
- self.results[context]['r'] = r
- self.results[context]['e'].set()
+ if self.event_callback:
+ self.event_callback(msgname, msg)
- def msg_handler_async(self, msg):
- if not msg:
- eprint('vpp_api.read failed')
- return
+ def _control_ping(self, context):
+ """Send a ping command."""
+ self._call_vpp_async(self.control_ping_index,
+ self.control_ping_msgdef,
+ context=context)
- i, ci = self.header.unpack_from(msg, 0)
- if self.id_names[i] == 'rx_thread_exit':
- return;
+ def _call_vpp(self, i, msgdef, multipart, **kwargs):
+ """Given a message, send the message and await a reply.
- #
- # Decode message and returns a tuple.
- #
- msgdef = self.id_msgdef[i]
- if not msgdef:
- raise IOError(2, 'Reply message undefined')
+ msgdef - the message packing definition
+ i - the message type index
+ multipart - True if the message returns multiple
+ messages in return.
+ context - context number - chosen at random if not
+ supplied.
+ The remainder of the kwargs are the arguments to the API call.
- r = self.decode(msgdef, msg)
- msgname = type(r).__name__
+ The return value is the message or message array containing
+ the response. It will raise an IOError exception if there was
+ no response within the timeout window.
+ """
- self.event_callback(msgname, r)
+ # We need a context if not supplied, in order to get the
+ # response
+ context = kwargs.get('context', self.get_context())
+ kwargs['context'] = context
- def _control_ping(self, context):
- self._write(self.encode(self.control_ping_msgdef,
- { '_vl_msg_id' : self.control_ping_index,
- 'context' : context}))
+ # Set up to receive a response
+ self.results_prepare(context, multi=multipart)
- def _call_vpp(self, i, msgdef, multipart, **kwargs):
- if not 'context' in kwargs:
- context = self.get_context()
- kwargs['context'] = context
- else:
- context = kwargs['context']
- kwargs['_vl_msg_id'] = i
- b = self.encode(msgdef, kwargs)
-
- self.results_prepare(context)
- self._write(b)
+ # Output the message
+ self._call_vpp_async(i, msgdef, **kwargs)
if multipart:
- self.results[context]['m'] = True
+ # Send a ping after the request - we use its response
+ # to detect that we have seen all results.
self._control_ping(context)
- self.results_wait(context)
- r = self.results[context]['r']
- self.results_clean(context)
+
+ # Block until we get a reply.
+ r = self.results_wait(context)
+
return r
- def _call_vpp_async(self, i, msgdef, multipart, **kwargs):
+ def _call_vpp_async(self, i, msgdef, **kwargs):
+ """Given a message, send the message and await a reply.
+
+ msgdef - the message packing definition
+ i - the message type index
+ context - context number - chosen at random if not
+ supplied.
+ The remainder of the kwargs are the arguments to the API call.
+ """
if not 'context' in kwargs:
context = self.get_context()
kwargs['context'] = context
self._write(b)
def register_event_callback(self, callback):
+ """Register a callback for async messages.
+
+ This will be called for async notifications in sync mode,
+ and all messages in async mode. In sync mode, replies to
+ requests will not come here.
+
+ callback is a fn(msg_type_name, msg_type) that will be
+ called when a message comes in. While this function is
+ executing, note that (a) you are in a background thread and
+ may wish to use threading.Lock to protect your datastructures,
+ and (b) message processing from VPP will stop (so if you take
+ a long while about it you may provoke reply timeouts or cause
+ VPP to fill the RX buffer). Passing None will disable the
+ callback.
+ """
self.event_callback = callback
-
Code Review / vpp.git / commitdiff