Python API: Synchronous mode.

Change-Id: Ic8f186dbb35bb4e2e191d311cab51315a88a2d81
Signed-off-by: Ole Troan <ot@cisco.com>

6 files changed, 380 insertions, 149 deletions

diff --git a/src/vlibmemory/memclnt.api b/src/vlibmemory/memclnt.api
index 0532d7b6a85..c38b483ca0a 100644
--- a/src/vlibmemory/memclnt.api
+++ b/src/vlibmemory/memclnt.api
@@ -48,15 +48,28 @@ define memclnt_delete_reply {
     u64 handle;               /* in case the client wonders */
 };
 
-/* 
+/*
  * Client RX thread exit
  */
-
 define rx_thread_exit {
     u8 dummy;
 };
 
 /*
+ * Client RX thread suspend
+ */
+define memclnt_rx_thread_suspend {
+    u8 dummy;
+};
+
+/*
+ * Client read timeout
+ */
+define memclnt_read_timeout {
+    u8 dummy;
+};
+
+/*
  * RPC
  */
 define rpc_call {
diff --git a/src/vpp-api/python/Makefile.am b/src/vpp-api/python/Makefile.am
index cd8db4f6c36..540768229c5 100644
--- a/src/vpp-api/python/Makefile.am
+++ b/src/vpp-api/python/Makefile.am
@@ -39,7 +39,7 @@ libpneum_la_LDFLAGS = -module
 libpneum_la_CPPFLAGS =
 
 # TODO: Support both Python 2 and 3.
-install-exec-local:
+install-exec-local: $(lib_LTLIBRARIES)
 	cd $(srcdir);							\
 	mkdir -p $(pythondir);						\
 	mkdir -p $(pyexecdir); 						\
diff --git a/src/vpp-api/python/pneum/pneum.c b/src/vpp-api/python/pneum/pneum.c
index 37c8d8fe5f9..da9d69dfd4f 100644
--- a/src/vpp-api/python/pneum/pneum.c
+++ b/src/vpp-api/python/pneum/pneum.c
@@ -22,9 +22,7 @@
 #include <netinet/in.h>
 #include <netdb.h>
 #include <signal.h>
-#include <setjmp.h>
 #include <stdbool.h>
-
 #include <vnet/vnet.h>
 #include <vlib/vlib.h>
 #include <vlib/unix/unix.h>
@@ -35,6 +33,16 @@
 
 #include "pneum.h"
 
+/*
+ * Asynchronous mode:
+ *  Client registers a callback. All messages are sent to the callback.
+ * Synchronous mode:
+ *  Client calls blocking read().
+ *  Clients are expected to collate events on a queue.
+ *  pneum_write() -> suspends RX thread
+ *  pneum_read() -> resumes RX thread
+ */
+
 #define vl_typedefs             /* define message structures */
 #include <vpp/api/vpe_all_api_h.h>
 #undef vl_typedefs
@@ -47,15 +55,50 @@ vlib_main_t vlib_global_main;
 vlib_main_t **vlib_mains;
 
 typedef struct {
-  u8 rx_thread_jmpbuf_valid;
   u8 connected_to_vlib;
-  jmp_buf rx_thread_jmpbuf;
   pthread_t rx_thread_handle;
+  pthread_t timeout_thread_handle;
+  pthread_mutex_t queue_lock;
+  pthread_cond_t suspend_cv;
+  pthread_cond_t resume_cv;
+  pthread_mutex_t timeout_lock;
+  pthread_cond_t timeout_cv;
+  pthread_cond_t timeout_cancel_cv;
+  pthread_cond_t terminate_cv;
 } pneum_main_t;
 
 pneum_main_t pneum_main;
-
 pneum_callback_t pneum_callback;
+u16 read_timeout = 0;
+bool rx_is_running = false;
+
+static void
+init (void)
+{
+  pneum_main_t *pm = &pneum_main;
+  memset(pm, 0, sizeof(*pm));
+  pthread_mutex_init(&pm->queue_lock, NULL);
+  pthread_cond_init(&pm->suspend_cv, NULL);
+  pthread_cond_init(&pm->resume_cv, NULL);
+  pthread_mutex_init(&pm->timeout_lock, NULL);
+  pthread_cond_init(&pm->timeout_cv, NULL);
+  pthread_cond_init(&pm->timeout_cancel_cv, NULL);
+  pthread_cond_init(&pm->terminate_cv, NULL);
+}
+
+static void
+cleanup (void)
+{
+  pneum_main_t *pm = &pneum_main;
+  pthread_cond_destroy(&pm->suspend_cv);
+  pthread_cond_destroy(&pm->resume_cv);
+  pthread_cond_destroy(&pm->timeout_cv);
+  pthread_cond_destroy(&pm->timeout_cancel_cv);
+  pthread_cond_destroy(&pm->terminate_cv);
+  pthread_mutex_destroy(&pm->queue_lock);
+  pthread_mutex_destroy(&pm->timeout_lock);
+  memset (pm, 0, sizeof (*pm));
+}
 
 /*
  * Satisfy external references when -lvlib is not available.
@@ -75,11 +118,6 @@ static void
 pneum_api_handler (void *msg)
 {
   u16 id = ntohs(*((u16 *)msg));
-  if (id == VL_API_RX_THREAD_EXIT) {
-    pneum_main_t *pm = &pneum_main;
-    vl_msg_api_free(msg);
-    longjmp(pm->rx_thread_jmpbuf, 1);
-  }
   msgbuf_t *msgbuf = (msgbuf_t *)(((u8 *)msg) - offsetof(msgbuf_t, data));
   int l = ntohl(msgbuf->data_len);
   if (l == 0)
@@ -101,16 +139,108 @@ pneum_rx_thread_fn (void *arg)
 
   q = am->vl_input_queue;
 
-  /* So we can make the rx thread terminate cleanly */
-  if (setjmp(pm->rx_thread_jmpbuf) == 0) {
-    pm->rx_thread_jmpbuf_valid = 1;
-    while (1)
-      while (!unix_shared_memory_queue_sub(q, (u8 *)&msg, 0))
-        pneum_api_handler((void *)msg);
-  }
+  while (1)
+    while (!unix_shared_memory_queue_sub(q, (u8 *)&msg, 0))
+      {
+	u16 id = ntohs(*((u16 *)msg));
+	switch (id) {
+	case VL_API_RX_THREAD_EXIT:
+	  vl_msg_api_free((void *) msg);
+	  /* signal waiting threads that this thread is about to terminate */
+	  pthread_mutex_lock(&pm->queue_lock);
+	  pthread_cond_signal(&pm->terminate_cv);
+	  pthread_mutex_unlock(&pm->queue_lock);
+	  pthread_exit(0);
+	  return 0;
+	  break;
+
+	case VL_API_MEMCLNT_RX_THREAD_SUSPEND:
+	  vl_msg_api_free((void * )msg);
+	  /* Suspend thread and signal reader */
+	  pthread_mutex_lock(&pm->queue_lock);
+	  pthread_cond_signal(&pm->suspend_cv);
+	  /* Wait for the resume signal */
+	  pthread_cond_wait (&pm->resume_cv, &pm->queue_lock);
+	  pthread_mutex_unlock(&pm->queue_lock);
+	  break;
+
+	case VL_API_MEMCLNT_READ_TIMEOUT:
+	  clib_warning("Received read timeout in async thread\n");
+	  vl_msg_api_free((void *) msg);
+	  break;
+
+	default:
+	  pneum_api_handler((void *)msg);
+	}
+      }
+}
+
+static void *
+pneum_timeout_thread_fn (void *arg)
+{
+  vl_api_memclnt_read_timeout_t *ep;
+  pneum_main_t *pm = &pneum_main;
+  api_main_t *am = &api_main;
+  struct timespec ts;
+  struct timeval tv;
+  u16 timeout;
+  int rv;
+
+  while (1)
+    {
+      /* Wait for poke */
+      pthread_mutex_lock(&pm->timeout_lock);
+      pthread_cond_wait (&pm->timeout_cv, &pm->timeout_lock);
+      timeout = read_timeout;
+      gettimeofday(&tv, NULL);
+      ts.tv_sec = tv.tv_sec + timeout;
+      ts.tv_nsec = 0;
+      rv = pthread_cond_timedwait (&pm->timeout_cancel_cv,
+				   &pm->timeout_lock, &ts);
+      pthread_mutex_unlock(&pm->timeout_lock);
+      if (rv == ETIMEDOUT)
+	{
+	  ep = vl_msg_api_alloc (sizeof (*ep));
+	  ep->_vl_msg_id = ntohs(VL_API_MEMCLNT_READ_TIMEOUT);
+	  vl_msg_api_send_shmem(am->vl_input_queue, (u8 *)&ep);
+	}
+    }
   pthread_exit(0);
 }
 
+void
+pneum_rx_suspend (void)
+{
+  api_main_t *am = &api_main;
+  pneum_main_t *pm = &pneum_main;
+  vl_api_memclnt_rx_thread_suspend_t *ep;
+
+  if (!pm->rx_thread_handle) return;
+  pthread_mutex_lock(&pm->queue_lock);
+  if (rx_is_running)
+    {
+      ep = vl_msg_api_alloc (sizeof (*ep));
+      ep->_vl_msg_id = ntohs(VL_API_MEMCLNT_RX_THREAD_SUSPEND);
+      vl_msg_api_send_shmem(am->vl_input_queue, (u8 *)&ep);
+      /* Wait for RX thread to tell us it has suspendend */
+      pthread_cond_wait(&pm->suspend_cv, &pm->queue_lock);
+      rx_is_running = false;
+    }
+  pthread_mutex_unlock(&pm->queue_lock);
+}
+
+void
+pneum_rx_resume (void)
+{
+  pneum_main_t *pm = &pneum_main;
+  if (!pm->rx_thread_handle) return;
+  pthread_mutex_lock(&pm->queue_lock);
+  if (rx_is_running) return;
+  pthread_cond_signal(&pm->resume_cv);
+  rx_is_running = true;
+  pthread_mutex_unlock(&pm->queue_lock);
+}
+
 uword *
 pneum_msg_table_get_hash (void)
 {
@@ -126,12 +256,13 @@ pneum_msg_table_size(void)
 }
 
 int
-pneum_connect (char * name, char * chroot_prefix, pneum_callback_t cb, 
+pneum_connect (char * name, char * chroot_prefix, pneum_callback_t cb,
                int rx_qlen)
 {
   int rv = 0;
   pneum_main_t *pm = &pneum_main;
 
+  init();
   if (chroot_prefix != NULL)
     vl_set_memory_root_path (chroot_prefix);
 
@@ -154,6 +285,16 @@ pneum_connect (char * name, char * chroot_prefix, pneum_callback_t cb,
       return (-1);
     }
     pneum_callback = cb;
+    rx_is_running = true;
+  }
+
+  /* Start read timeout thread */
+  rv = pthread_create(&pm->timeout_thread_handle, NULL,
+		      pneum_timeout_thread_fn, 0);
+  if (rv) {
+    clib_warning("pthread_create returned %d", rv);
+    vl_client_api_unmap();
+    return (-1);
   }
 
   pm->connected_to_vlib = 1;
@@ -167,31 +308,69 @@ pneum_disconnect (void)
   api_main_t *am = &api_main;
   pneum_main_t *pm = &pneum_main;
 
-  if (pm->rx_thread_jmpbuf_valid) {
+  if (!pm->connected_to_vlib) return 0;
+
+  if (pm->rx_thread_handle) {
     vl_api_rx_thread_exit_t *ep;
     uword junk;
     ep = vl_msg_api_alloc (sizeof (*ep));
     ep->_vl_msg_id = ntohs(VL_API_RX_THREAD_EXIT);
     vl_msg_api_send_shmem(am->vl_input_queue, (u8 *)&ep);
-    pthread_join(pm->rx_thread_handle, (void **) &junk);
-  }
-  if (pm->connected_to_vlib) {
-    vl_client_disconnect();
-    vl_client_api_unmap();
-    pneum_callback = 0;
+
+    /* wait (with timeout) until RX thread has finished */
+    struct timespec ts;
+    struct timeval tv;
+    gettimeofday(&tv, NULL);
+    ts.tv_sec = tv.tv_sec + 5;
+    ts.tv_nsec = 0;
+    pthread_mutex_lock(&pm->queue_lock);
+    int rv = pthread_cond_timedwait(&pm->terminate_cv, &pm->queue_lock, &ts);
+    pthread_mutex_unlock(&pm->queue_lock);
+    /* now join so we wait until thread has -really- finished */
+    if (rv == ETIMEDOUT)
+      pthread_cancel(pm->rx_thread_handle);
+    else
+      pthread_join(pm->rx_thread_handle, (void **) &junk);
   }
-  memset (pm, 0, sizeof (*pm));
+  if (pm->timeout_thread_handle)
+    pthread_cancel(pm->timeout_thread_handle);
+
+  vl_client_disconnect();
+  vl_client_api_unmap();
+  pneum_callback = 0;
+
+  cleanup();
 
   return (0);
 }
 
+static void
+set_timeout (unsigned short timeout)
+{
+  pneum_main_t *pm = &pneum_main;
+  pthread_mutex_lock(&pm->timeout_lock);
+  read_timeout = timeout;
+  pthread_cond_signal(&pm->timeout_cv);
+  pthread_mutex_unlock(&pm->timeout_lock);
+}
+
+static void
+unset_timeout (void)
+{
+  pneum_main_t *pm = &pneum_main;
+  pthread_mutex_lock(&pm->timeout_lock);
+  pthread_cond_signal(&pm->timeout_cancel_cv);
+  pthread_mutex_unlock(&pm->timeout_lock);
+}
+
 int
-pneum_read (char **p, int *l)
+pneum_read (char **p, int *l, u16 timeout)
 {
   unix_shared_memory_queue_t *q;
   api_main_t *am = &api_main;
   pneum_main_t *pm = &pneum_main;
   uword msg;
+  msgbuf_t *msgbuf;
 
   if (!pm->connected_to_vlib) return -1;
 
@@ -199,21 +378,48 @@ pneum_read (char **p, int *l)
 
   if (am->our_pid == 0) return (-1);
 
+  /* Poke timeout thread */
+  if (timeout)
+    set_timeout(timeout);
+
   q = am->vl_input_queue;
   int rv = unix_shared_memory_queue_sub(q, (u8 *)&msg, 0);
   if (rv == 0) {
     u16 msg_id = ntohs(*((u16 *)msg));
-    msgbuf_t *msgbuf = (msgbuf_t *)(((u8 *)msg) - offsetof(msgbuf_t, data));
-    *l = ntohl(msgbuf->data_len);
-    if (*l == 0) {
-      printf("Unregistered API message: %d\n", msg_id);
-      return (-1);
+    switch (msg_id) {
+    case VL_API_RX_THREAD_EXIT:
+      printf("Received thread exit\n");
+      return -1;
+    case VL_API_MEMCLNT_RX_THREAD_SUSPEND:
+      printf("Received thread suspend\n");
+      goto error;
+    case VL_API_MEMCLNT_READ_TIMEOUT:
+      printf("Received read timeout %ds\n", timeout);
+      goto error;
+
+    default:
+      msgbuf = (msgbuf_t *)(((u8 *)msg) - offsetof(msgbuf_t, data));
+      *l = ntohl(msgbuf->data_len);
+      if (*l == 0) {
+	printf("Unregistered API message: %d\n", msg_id);
+	goto error;
+      }
     }
     *p = (char *)msg;
+
+    /* Let timeout notification thread know we're done */
+    unset_timeout();
+
   } else {
     printf("Read failed with %d\n", rv);
   }
   return (rv);
+
+ error:
+  vl_msg_api_free((void *) msg);
+  /* Client might forget to resume RX thread on failure */
+  pneum_rx_resume ();
+  return -1;
 }
 
 /*
@@ -241,12 +447,13 @@ pneum_write (char *p, int l)
 
   if (!pm->connected_to_vlib) return -1;
   if (!mp) return (-1);
+
   memcpy(mp, p, l);
   mp->client_index = pneum_client_index();
   q = am->shmem_hdr->vl_input_queue;
   rv = unix_shared_memory_queue_add(q, (u8 *)&mp, 0);
   if (rv != 0) {
-    printf("vpe_api_write fails: %d\n", rv);
+    clib_warning("vpe_api_write fails: %d\n", rv);
     /* Clear message */
     pneum_free(mp);
   }
diff --git a/src/vpp-api/python/pneum/pneum.h b/src/vpp-api/python/pneum/pneum.h
index 9312eb47817..c4b55ae0be1 100644
--- a/src/vpp-api/python/pneum/pneum.h
+++ b/src/vpp-api/python/pneum/pneum.h
@@ -22,11 +22,13 @@ typedef void (*pneum_callback_t)(unsigned char * data, int len);
 int pneum_connect(char * name, char * chroot_prefix, pneum_callback_t cb,
     int rx_qlen);
 int pneum_disconnect(void);
-int pneum_read(char **data, int *l);
+int pneum_read(char **data, int *l, unsigned short timeout);
 int pneum_write(char *data, int len);
 void pneum_free(void * msg);
 uword * pneum_msg_table_get_hash (void);
 int pneum_msg_table_size(void);
 uint32_t pneum_get_msg_index(unsigned char * name);
+void pneum_rx_suspend (void);
+void pneum_rx_resume (void);
 
 #endif
diff --git a/src/vpp-api/python/vpp_papi/pneum_wrap.c b/src/vpp-api/python/vpp_papi/pneum_wrap.c
index 748b96744aa..c5a7eea1e00 100644
--- a/src/vpp-api/python/vpp_papi/pneum_wrap.c
+++ b/src/vpp-api/python/vpp_papi/pneum_wrap.c
@@ -42,19 +42,19 @@ wrap_pneum_callback (unsigned char * data, int len)
 }
 
 static PyObject *
-wrap_connect (PyObject *self, PyObject *args)
+wrap_connect (PyObject *self, PyObject *args, PyObject *kw)
 {
   char * name, * chroot_prefix = NULL;
-  int rx_qlen=32; /* default rx queue length */
+  int rx_qlen = 32; /* default rx queue length */
   int rv;
   PyObject * temp = NULL;
   pneum_callback_t cb = NULL;
 
-  if (!PyArg_ParseTuple(args, "s|Ois:wrap_connect",
-			&name, &temp, &rx_qlen, &chroot_prefix))
+  if (!PyArg_ParseTuple(args, "sOzi:wrap_connect",
+			&name, &temp, &chroot_prefix, &rx_qlen))
     return (NULL);
 
-  if (temp)
+  if (temp != Py_None)
     {
       if (!PyCallable_Check(temp))
 	{
@@ -82,6 +82,7 @@ wrap_disconnect (PyObject *self, PyObject *args)
   Py_END_ALLOW_THREADS
   return PyLong_FromLong(rv);
 }
+
 static PyObject *
 wrap_write (PyObject *self, PyObject *args)
 {
@@ -90,6 +91,7 @@ wrap_write (PyObject *self, PyObject *args)
 
   if (!PyArg_ParseTuple(args, "s#", &data, &len))
     return NULL;
+
   Py_BEGIN_ALLOW_THREADS
   rv = pneum_write(data, len);
   Py_END_ALLOW_THREADS
@@ -102,9 +104,12 @@ wrap_read (PyObject *self, PyObject *args)
 {
   char *data;
   int len, rv;
+  unsigned short timeout;
 
+  if (!PyArg_ParseTuple(args, "H", &timeout))
+    return (NULL);
   Py_BEGIN_ALLOW_THREADS
-  rv = pneum_read(&data, &len);
+  rv = pneum_read(&data, &len, timeout);
   Py_END_ALLOW_THREADS
 
   if (rv != 0) { Py_RETURN_NONE; }
@@ -113,9 +118,9 @@ wrap_read (PyObject *self, PyObject *args)
 #else
   PyObject *ret = Py_BuildValue("s#", data, len);
 #endif
+  pneum_free(data);
   if (!ret) { Py_RETURN_NONE; }
 
-  pneum_free(data);
   return ret;
 }
 
@@ -147,12 +152,32 @@ wrap_msg_table (PyObject *self, PyObject *args)
   Py_RETURN_NONE;
 }
 
+static PyObject *
+wrap_suspend (PyObject *self, PyObject *args)
+{
+  Py_BEGIN_ALLOW_THREADS
+  pneum_rx_suspend();
+  Py_END_ALLOW_THREADS
+  Py_RETURN_NONE;
+}
+
+static PyObject *
+wrap_resume (PyObject *self, PyObject *args)
+{
+  Py_BEGIN_ALLOW_THREADS
+  pneum_rx_resume();
+  Py_END_ALLOW_THREADS
+  Py_RETURN_NONE;
+}
+
 static PyMethodDef vpp_api_Methods[] = {
   {"connect", wrap_connect, METH_VARARGS, "Connect to the VPP API."},
   {"disconnect", wrap_disconnect, METH_VARARGS, "Disconnect from the VPP API."},
   {"write", wrap_write, METH_VARARGS, "Write data to the VPP API."},
   {"read", wrap_read, METH_VARARGS, "Read data from the VPP API."},
   {"msg_table", wrap_msg_table, METH_VARARGS, "Get API dictionary."},
+  {"suspend", wrap_suspend, METH_VARARGS, "Suspend RX thread."},
+  {"resume", wrap_resume, METH_VARARGS, "Resume RX thread."},
   {NULL, NULL, 0, NULL}        /* Sentinel */
 };
 
diff --git a/src/vpp-api/python/vpp_papi/vpp_papi.py b/src/vpp-api/python/vpp_papi/vpp_papi.py
index 83247ffa04b..0c40f1710e5 100644
--- a/src/vpp-api/python/vpp_papi/vpp_papi.py
+++ b/src/vpp-api/python/vpp_papi/vpp_papi.py
@@ -16,7 +16,7 @@
 
 from __future__ import print_function
 import sys, os, logging, collections, struct, json, threading, glob
-import atexit
+import atexit, Queue
 
 logging.basicConfig(level=logging.DEBUG)
 import vpp_api
@@ -57,7 +57,7 @@ class VPP():
     provides a means to register a callback function to receive
     these messages in a background thread.
     """
-    def __init__(self, apifiles = None, testmode = False):
+    def __init__(self, apifiles = None, testmode = False, async_thread = True):
         """Create a VPP API object.
 
         apifiles is a list of files containing API
@@ -72,11 +72,15 @@ class VPP():
         self.buffersize = 10000
         self.connected = False
         self.header = struct.Struct('>HI')
-        self.results_lock = threading.Lock()
-        self.results = {}
-        self.timeout = 5
         self.apifiles = []
         self.event_callback = None
+        self.message_queue = Queue.Queue()
+        self.read_timeout = 0
+        self.vpp_api = vpp_api
+        if async_thread:
+            self.event_thread = threading.Thread(target=self.thread_msg_handler)
+            self.event_thread.daemon = True
+            self.event_thread.start()
 
         if not apifiles:
             # Pick up API definitions from default directory
@@ -346,7 +350,7 @@ class VPP():
                 f = self.make_function(name, i, msgdef, multipart, async)
                 setattr(self._api, name, FuncWrapper(f))
 
-                # olf API stuff starts here - will be removed in 17.07
+                # old API stuff starts here - will be removed in 17.07
                 if hasattr(self, name):
                     raise NameError(
                         3, "Conflicting name in JSON definition: `%s'" % name)
@@ -359,6 +363,12 @@ class VPP():
             raise IOError(1, 'Not connected')
         return vpp_api.write(str(buf))
 
+    def _read (self):
+        if not self.connected:
+            raise IOError(1, 'Not connected')
+
+        return vpp_api.read(self.read_timeout)
+
     def _load_dictionary(self):
         self.vpp_dictionary = {}
         self.vpp_dictionary_maxid = 0
@@ -372,6 +382,19 @@ class VPP():
             self.vpp_dictionary[name] = { 'id' : i, 'crc' : crc }
             self.vpp_dictionary_maxid = max(self.vpp_dictionary_maxid, i)
 
+    def connect_internal(self, name, msg_handler, chroot_prefix, rx_qlen, async):
+	rv = vpp_api.connect(name, msg_handler, chroot_prefix, rx_qlen)
+        if rv != 0:
+            raise IOError(2, 'Connect failed')
+        self.connected = True
+
+        self._load_dictionary()
+        self._register_functions(async=async)
+
+        # Initialise control ping
+        self.control_ping_index = self.vpp_dictionary['control_ping']['id']
+        self.control_ping_msgdef = self.messages['control_ping']
+
     def connect(self, name, chroot_prefix = None, async = False, rx_qlen = 32):
         """Attach to VPP.
 
@@ -381,22 +404,22 @@ class VPP():
         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)
+        msg_handler = self.msg_handler_sync if not async \
+                      else self.msg_handler_async
+        return self.connect_internal(name, msg_handler, chroot_prefix, rx_qlen,
+                                     async)
 
-        if rv != 0:
-            raise IOError(2, 'Connect failed')
-        self.connected = True
+    def connect_sync (self, name, chroot_prefix = None, rx_qlen = 32):
+        """Attach to VPP in synchronous mode. Application must poll for events.
 
-        self._load_dictionary()
-        self._register_functions(async=async)
+        name - the name of the client.
+        chroot_prefix - if VPP is chroot'ed, the prefix of the jail
+        rx_qlen - the length of the VPP message receive queue between
+        client and server.
+        """
 
-        # Initialise control ping
-        self.control_ping_index = self.vpp_dictionary['control_ping']['id']
-        self.control_ping_msgdef = self.messages['control_ping']
+        return self.connect_internal(name, None, chroot_prefix, rx_qlen,
+                                     async=False)
 
     def disconnect(self):
         """Detach from VPP."""
@@ -404,56 +427,6 @@ class VPP():
         self.connected = False
         return rv
 
-    def results_wait(self, context):
-        """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.
 
@@ -473,32 +446,9 @@ class VPP():
 
         if context == 0:
             # No context -> async notification that we feed to the callback
-	    if self.event_callback:
-		self.event_callback(msgname, r)
+            self.message_queue.put_nowait(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()
+            raise IOError(2, 'RPC reply message received in event handler')
 
     def decode_incoming_msg(self, msg):
         if not msg:
@@ -556,16 +506,16 @@ class VPP():
         no response within the timeout window.
         """
 
-        # We need a context if not supplied, in order to get the
-        # response
-        context = kwargs.get('context', self.get_context())
-	kwargs['context'] = context
-
-        # Set up to receive a response
-        self.results_prepare(context, multi=multipart)
+        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)
 
-        # Output the message
-        self._call_vpp_async(i, msgdef, **kwargs)
+        vpp_api.suspend()
+        self._write(b)
 
         if multipart:
             # Send a ping after the request - we use its response
@@ -573,9 +523,30 @@ class VPP():
             self._control_ping(context)
 
         # Block until we get a reply.
-        r = self.results_wait(context)
+        rl = []
+        while (True):
+            msg = self._read()
+            if not msg:
+                print('PNEUM ERROR: OH MY GOD')
+                raise IOError(2, 'PNEUM read failed')
+
+            r = self.decode_incoming_msg(msg)
+            msgname = type(r).__name__
+            if not context in r or r.context == 0 or context != r.context:
+                self.message_queue.put_nowait(r)
+                continue
 
-        return r
+            if not multipart:
+                rl = r
+                break
+            if msgname == 'control_ping_reply':
+                break
+
+            rl.append(r)
+
+        vpp_api.resume()
+
+        return rl
 
     def _call_vpp_async(self, i, msgdef, **kwargs):
         """Given a message, send the message and await a reply.
@@ -613,3 +584,16 @@ class VPP():
         callback.
         """
         self.event_callback = callback
+
+    def thread_msg_handler(self):
+        """Python thread calling the user registerd message handler.
+
+        This is to emulate the old style event callback scheme. Modern
+        clients should provide their own thread to poll the event
+        queue.
+        """
+        while True:
+            r = self.message_queue.get()
+            msgname = type(r).__name__
+	    if self.event_callback:
+	        self.event_callback(msgname, r)