X-Git-Url: http://git.onelab.eu/?a=blobdiff_plain;f=lib%2Frconn.c;h=ba606fb5eaba2ee1881887d024004dff169c1773;hb=5d69c233557908e25f25acaa8d21da10de1a2868;hp=1668ad9906cdf98e9a31724e0593f0e523e3ab38;hpb=e334e4e0e775a431677bf54a5ece134167fe514d;p=sliver-openvswitch.git

diff --git a/lib/rconn.c b/lib/rconn.c
index 1668ad990..ba606fb5e 100644
--- a/lib/rconn.c
+++ b/lib/rconn.c
@@ -1,6 +1,6 @@
 /* Copyright (c) 2008 The Board of Trustees of The Leland Stanford
  * Junior University
- * 
+ *
  * We are making the OpenFlow specification and associated documentation
  * (Software) available for public use and benefit with the expectation
  * that others will use, modify and enhance the Software and contribute
@@ -13,10 +13,10 @@
  * distribute, sublicense, and/or sell copies of the Software, and to
  * permit persons to whom the Software is furnished to do so, subject to
  * the following conditions:
- * 
+ *
  * The above copyright notice and this permission notice shall be
  * included in all copies or substantial portions of the Software.
- * 
+ *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
@@ -25,62 +25,145 @@
  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
- * 
+ *
  * The name and trademarks of copyright holder(s) may NOT be used in
  * advertising or publicity pertaining to the Software or any
  * derivatives without specific, written prior permission.
  */
 
+#include <config.h>
 #include "rconn.h"
 #include <assert.h>
 #include <errno.h>
+#include <limits.h>
 #include <stdlib.h>
 #include <string.h>
-#include "buffer.h"
+#include "ofpbuf.h"
+#include "openflow/openflow.h"
 #include "poll-loop.h"
-#include "ofp-print.h"
+#include "sat-math.h"
+#include "timeval.h"
 #include "util.h"
 #include "vconn.h"
 
 #define THIS_MODULE VLM_rconn
 #include "vlog.h"
 
+#define STATES                                  \
+    STATE(VOID, 1 << 0)                         \
+    STATE(BACKOFF, 1 << 1)                      \
+    STATE(CONNECTING, 1 << 2)                   \
+    STATE(ACTIVE, 1 << 3)                       \
+    STATE(IDLE, 1 << 4)
+enum state {
+#define STATE(NAME, VALUE) S_##NAME = VALUE,
+    STATES
+#undef STATE
+};
+
+static const char *
+state_name(enum state state)
+{
+    switch (state) {
+#define STATE(NAME, VALUE) case S_##NAME: return #NAME;
+        STATES
+#undef STATE
+    }
+    return "***ERROR***";
+}
+
 /* A reliable connection to an OpenFlow switch or controller.
  *
  * See the large comment in rconn.h for more information. */
 struct rconn {
-    bool reliable;
-    char *name;
+    enum state state;
+    time_t state_entered;
+
     struct vconn *vconn;
-    bool connected;
-    struct queue txq;
-    int txq_limit;
-    time_t backoff_deadline;
+    char *name;
+    bool reliable;
+
+    struct ofp_queue txq;
+
     int backoff;
     int max_backoff;
+    time_t backoff_deadline;
+    time_t last_received;
     time_t last_connected;
     unsigned int packets_sent;
 
+    /* In S_ACTIVE and S_IDLE, probably_admitted reports whether we believe
+     * that the peer has made a (positive) admission control decision on our
+     * connection.  If we have not yet been (probably) admitted, then the
+     * connection does not reset the timer used for deciding whether the switch
+     * should go into fail-open mode.
+     *
+     * last_admitted reports the last time we believe such a positive admission
+     * control decision was made. */
+    bool probably_admitted;
+    time_t last_admitted;
+
+    /* These values are simply for statistics reporting, not used directly by
+     * anything internal to the rconn (or the secchan for that matter). */
+    unsigned int packets_received;
+    unsigned int n_attempted_connections, n_successful_connections;
+    time_t creation_time;
+    unsigned long int total_time_connected;
+
+    /* If we can't connect to the peer, it could be for any number of reasons.
+     * Usually, one would assume it is because the peer is not running or
+     * because the network is partitioned.  But it could also be because the
+     * network topology has changed, in which case the upper layer will need to
+     * reassess it (in particular, obtain a new IP address via DHCP and find
+     * the new location of the controller).  We set this flag when we suspect
+     * that this could be the case. */
+    bool questionable_connectivity;
+    time_t last_questioned;
+
     /* Throughout this file, "probe" is shorthand for "inactivity probe".
      * When nothing has been received from the peer for a while, we send out
      * an echo request as an inactivity probe packet.  We should receive back
      * a response. */
     int probe_interval;         /* Secs of inactivity before sending probe. */
-    time_t probe_sent;          /* Time at which last probe sent, or 0 if none
-                                 * has been sent since 'last_connected'. */
+
+    /* Messages sent or received are copied to the monitor connections. */
+#define MAX_MONITORS 8
+    struct vconn *monitors[8];
+    size_t n_monitors;
 };
 
-static struct rconn *create_rconn(const char *name, int txq_limit,
-                                  int probe_interval, int max_backoff,
-                                  struct vconn *);
+static unsigned int elapsed_in_this_state(const struct rconn *);
+static unsigned int timeout(const struct rconn *);
+static bool timed_out(const struct rconn *);
+static void state_transition(struct rconn *, enum state);
 static int try_send(struct rconn *);
+static int reconnect(struct rconn *);
 static void disconnect(struct rconn *, int error);
-static time_t probe_deadline(const struct rconn *);
+static void flush_queue(struct rconn *);
+static void question_connectivity(struct rconn *);
+static void copy_to_monitor(struct rconn *, const struct ofpbuf *);
+static bool is_connected_state(enum state);
+static bool is_admitted_msg(const struct ofpbuf *);
 
-/* Creates and returns a new rconn that connects (and re-connects as necessary)
- * to the vconn named 'name'.
- *
- * 'txq_limit' is the maximum length of the send queue, in packets.
+/* Creates a new rconn, connects it (reliably) to 'name', and returns it. */
+struct rconn *
+rconn_new(const char *name, int inactivity_probe_interval, int max_backoff)
+{
+    struct rconn *rc = rconn_create(inactivity_probe_interval, max_backoff);
+    rconn_connect(rc, name);
+    return rc;
+}
+
+/* Creates a new rconn, connects it (unreliably) to 'vconn', and returns it. */
+struct rconn *
+rconn_new_from_vconn(const char *name, struct vconn *vconn) 
+{
+    struct rconn *rc = rconn_create(60, 0);
+    rconn_connect_unreliably(rc, name, vconn);
+    return rc;
+}
+
+/* Creates and returns a new rconn.
  *
  * 'probe_interval' is a number of seconds.  If the interval passes once
  * without an OpenFlow message being received from the peer, the rconn sends
@@ -93,21 +176,87 @@ static time_t probe_deadline(const struct rconn *);
  * failure until it reaches 'max_backoff'.  If 0 is specified, the default of
  * 60 seconds is used. */
 struct rconn *
-rconn_new(const char *name, int txq_limit, int probe_interval, int max_backoff)
+rconn_create(int probe_interval, int max_backoff)
 {
-    return create_rconn(name, txq_limit, probe_interval, max_backoff, NULL);
+    struct rconn *rc = xcalloc(1, sizeof *rc);
+
+    rc->state = S_VOID;
+    rc->state_entered = time_now();
+
+    rc->vconn = NULL;
+    rc->name = xstrdup("void");
+    rc->reliable = false;
+
+    queue_init(&rc->txq);
+
+    rc->backoff = 0;
+    rc->max_backoff = max_backoff ? max_backoff : 60;
+    rc->backoff_deadline = TIME_MIN;
+    rc->last_received = time_now();
+    rc->last_connected = time_now();
+
+    rc->packets_sent = 0;
+
+    rc->probably_admitted = false;
+    rc->last_admitted = time_now();
+
+    rc->packets_received = 0;
+    rc->n_attempted_connections = 0;
+    rc->n_successful_connections = 0;
+    rc->creation_time = time_now();
+    rc->total_time_connected = 0;
+
+    rc->questionable_connectivity = false;
+    rc->last_questioned = time_now();
+
+    rc->probe_interval = probe_interval ? MAX(5, probe_interval) : 0;
+
+    rc->n_monitors = 0;
+
+    return rc;
 }
 
-/* Creates and returns a new rconn that is initially connected to 'vconn' and
- * has the given 'name'.  The rconn will not re-connect after the connection
- * drops.
- *
- * 'txq_limit' is the maximum length of the send queue, in packets. */
-struct rconn *
-rconn_new_from_vconn(const char *name, int txq_limit, struct vconn *vconn)
+int
+rconn_connect(struct rconn *rc, const char *name)
+{
+    rconn_disconnect(rc);
+    free(rc->name);
+    rc->name = xstrdup(name);
+    rc->reliable = true;
+    return reconnect(rc);
+}
+
+void
+rconn_connect_unreliably(struct rconn *rc,
+                         const char *name, struct vconn *vconn)
 {
     assert(vconn != NULL);
-    return create_rconn(name, txq_limit, 0, 0, vconn);
+    rconn_disconnect(rc);
+    free(rc->name);
+    rc->name = xstrdup(name);
+    rc->reliable = false;
+    rc->vconn = vconn;
+    rc->last_connected = time_now();
+    state_transition(rc, S_ACTIVE);
+}
+
+void
+rconn_disconnect(struct rconn *rc)
+{
+    if (rc->state != S_VOID) {
+        if (rc->vconn) {
+            vconn_close(rc->vconn);
+            rc->vconn = NULL;
+        }
+        free(rc->name);
+        rc->name = xstrdup("void");
+        rc->reliable = false;
+
+        rc->backoff = 0;
+        rc->backoff_deadline = TIME_MIN;
+
+        state_transition(rc, S_VOID);
+    }
 }
 
 /* Disconnects 'rc' and frees the underlying storage. */
@@ -115,73 +264,169 @@ void
 rconn_destroy(struct rconn *rc)
 {
     if (rc) {
+        size_t i;
+
         free(rc->name);
         vconn_close(rc->vconn);
+        flush_queue(rc);
         queue_destroy(&rc->txq);
+        for (i = 0; i < rc->n_monitors; i++) {
+            vconn_close(rc->monitors[i]);
+        }
         free(rc);
     }
 }
 
+static unsigned int
+timeout_VOID(const struct rconn *rc)
+{
+    return UINT_MAX;
+}
+
+static void
+run_VOID(struct rconn *rc)
+{
+    /* Nothing to do. */
+}
+
+static int
+reconnect(struct rconn *rc)
+{
+    int retval;
+
+    VLOG_WARN("%s: connecting...", rc->name);
+    rc->n_attempted_connections++;
+    retval = vconn_open(rc->name, OFP_VERSION, &rc->vconn);
+    if (!retval) {
+        rc->backoff_deadline = time_now() + rc->backoff;
+        state_transition(rc, S_CONNECTING);
+    } else {
+        VLOG_WARN("%s: connection failed (%s)", rc->name, strerror(retval));
+        rc->backoff_deadline = TIME_MAX; /* Prevent resetting backoff. */
+        disconnect(rc, 0);
+    }
+    return retval;
+}
+
+static unsigned int
+timeout_BACKOFF(const struct rconn *rc)
+{
+    return rc->backoff;
+}
+
+static void
+run_BACKOFF(struct rconn *rc)
+{
+    if (timed_out(rc)) {
+        reconnect(rc);
+    }
+}
+
+static unsigned int
+timeout_CONNECTING(const struct rconn *rc)
+{
+    return MAX(1, rc->backoff);
+}
+
+static void
+run_CONNECTING(struct rconn *rc)
+{
+    int retval = vconn_connect(rc->vconn);
+    if (!retval) {
+        VLOG_WARN("%s: connected", rc->name);
+        rc->n_successful_connections++;
+        state_transition(rc, S_ACTIVE);
+        rc->last_connected = rc->state_entered;
+    } else if (retval != EAGAIN) {
+        VLOG_WARN("%s: connection failed (%s)", rc->name, strerror(retval));
+        disconnect(rc, retval);
+    } else if (timed_out(rc)) {
+        VLOG_WARN("%s: connection timed out", rc->name);
+        rc->backoff_deadline = TIME_MAX; /* Prevent resetting backoff. */
+        disconnect(rc, 0);
+    }
+}
+
+static void
+do_tx_work(struct rconn *rc)
+{
+    if (!rc->txq.n) {
+        return;
+    }
+    while (rc->txq.n > 0) {
+        int error = try_send(rc);
+        if (error) {
+            break;
+        }
+    }
+    if (!rc->txq.n) {
+        poll_immediate_wake();
+    }
+}
+
+static unsigned int
+timeout_ACTIVE(const struct rconn *rc)
+{
+    if (rc->probe_interval) {
+        unsigned int base = MAX(rc->last_received, rc->state_entered);
+        unsigned int arg = base + rc->probe_interval - rc->state_entered;
+        return arg;
+    }
+    return UINT_MAX;
+}
+
+static void
+run_ACTIVE(struct rconn *rc)
+{
+    if (timed_out(rc)) {
+        unsigned int base = MAX(rc->last_received, rc->state_entered);
+        rconn_send(rc, make_echo_request(), NULL);
+        VLOG_DBG("%s: idle %u seconds, sending inactivity probe",
+                 rc->name, (unsigned int) (time_now() - base));
+        state_transition(rc, S_IDLE);
+        return;
+    }
+
+    do_tx_work(rc);
+}
+
+static unsigned int
+timeout_IDLE(const struct rconn *rc)
+{
+    return rc->probe_interval;
+}
+
+static void
+run_IDLE(struct rconn *rc)
+{
+    if (timed_out(rc)) {
+        question_connectivity(rc);
+        VLOG_ERR("%s: no response to inactivity probe after %u "
+                 "seconds, disconnecting",
+                 rc->name, elapsed_in_this_state(rc));
+        disconnect(rc, 0);
+    } else {
+        do_tx_work(rc);
+    }
+}
+
 /* Performs whatever activities are necessary to maintain 'rc': if 'rc' is
  * disconnected, attempts to (re)connect, backing off as necessary; if 'rc' is
  * connected, attempts to send packets in the send queue, if any. */
 void
 rconn_run(struct rconn *rc)
 {
-    if (!rc->vconn) {
-        if (rc->reliable && time(0) >= rc->backoff_deadline) {
-            int retval;
-
-            retval = vconn_open(rc->name, &rc->vconn);
-            if (!retval) {
-                rc->backoff_deadline = time(0) + rc->backoff;
-                rc->connected = false;
-            } else {
-                VLOG_WARN("%s: connection failed (%s)",
-                          rc->name, strerror(retval)); 
-                disconnect(rc, 0);
-            }
-        }
-    } else if (!rc->connected) {
-        int error = vconn_connect(rc->vconn);
-        if (!error) {
-            VLOG_WARN("%s: connected", rc->name);
-            if (vconn_is_passive(rc->vconn)) {
-                fatal(0, "%s: passive vconn not supported in switch",
-                      rc->name);
-            }
-            rc->connected = true;
-        } else if (error != EAGAIN) {
-            VLOG_WARN("%s: connection failed (%s)", rc->name, strerror(error));
-            disconnect(rc, 0);
+    int old_state;
+    do {
+        old_state = rc->state;
+        switch (rc->state) {
+#define STATE(NAME, VALUE) case S_##NAME: run_##NAME(rc); break;
+            STATES
+#undef STATE
+        default:
+            NOT_REACHED();
         }
-    } else {
-        if (rc->probe_interval) {
-            time_t now = time(0);
-            if (now >= probe_deadline(rc)) {
-                if (!rc->probe_sent) {
-                    queue_push_tail(&rc->txq, make_echo_request());
-                    rc->probe_sent = now;
-                    VLOG_DBG("%s: idle %d seconds, sending inactivity probe",
-                             rc->name, (int) (now - rc->last_connected)); 
-                } else {
-                    VLOG_ERR("%s: no response to inactivity probe after %d "
-                             "seconds, disconnecting",
-                             rc->name, (int) (now - rc->probe_sent));
-                    disconnect(rc, 0);
-                }
-            }
-        }
-        while (rc->txq.n > 0) {
-            int error = try_send(rc);
-            if (error == EAGAIN) {
-                break;
-            } else if (error) {
-                disconnect(rc, error);
-                return;
-            }
-        }
-    }
+    } while (rc->state != old_state);
 }
 
 /* Causes the next call to poll_block() to wake up when rconn_run() should be
@@ -189,44 +434,42 @@ rconn_run(struct rconn *rc)
 void
 rconn_run_wait(struct rconn *rc)
 {
-    if (rc->vconn) {
-        if (rc->txq.n) {
-            vconn_wait(rc->vconn, WAIT_SEND);
-        }
-        if (rc->probe_interval) {
-            poll_timer_wait((probe_deadline(rc) - time(0)) * 1000);
-        }
-    } else {
-        poll_timer_wait((rc->backoff_deadline - time(0)) * 1000);
+    unsigned int timeo = timeout(rc);
+    if (timeo != UINT_MAX) {
+        unsigned int expires = sat_add(rc->state_entered, timeo);
+        unsigned int remaining = sat_sub(expires, time_now());
+        poll_timer_wait(sat_mul(remaining, 1000));
     }
-}
 
-/* Returns the time at which, should nothing be received, we should send out an
- * inactivity probe (if none has yet been sent) or conclude that the connection
- * is dead (if a probe has already been sent). */
-static time_t
-probe_deadline(const struct rconn *rc) 
-{
-    assert(rc->probe_interval);
-    return (rc->probe_interval
-            + (rc->probe_sent ? rc->probe_sent : rc->last_connected));
+    if ((rc->state & (S_ACTIVE | S_IDLE)) && rc->txq.n) {
+        vconn_wait(rc->vconn, WAIT_SEND);
+    }
 }
 
 /* Attempts to receive a packet from 'rc'.  If successful, returns the packet;
  * otherwise, returns a null pointer.  The caller is responsible for freeing
- * the packet (with buffer_delete()). */
-struct buffer *
+ * the packet (with ofpbuf_delete()). */
+struct ofpbuf *
 rconn_recv(struct rconn *rc)
 {
-    if (rc->vconn && rc->connected) {
-        struct buffer *buffer;
+    if (rc->state & (S_ACTIVE | S_IDLE)) {
+        struct ofpbuf *buffer;
         int error = vconn_recv(rc->vconn, &buffer);
         if (!error) {
-            rc->last_connected = time(0);
-            rc->probe_sent = 0;
+            copy_to_monitor(rc, buffer);
+            if (is_admitted_msg(buffer)
+                || time_now() - rc->last_connected >= 30) {
+                rc->probably_admitted = true;
+                rc->last_admitted = time_now();
+            }
+            rc->last_received = time_now();
+            rc->packets_received++;
+            if (rc->state == S_IDLE) {
+                state_transition(rc, S_ACTIVE);
+            }
             return buffer;
         } else if (error != EAGAIN) {
-            disconnect(rc, error); 
+            disconnect(rc, error);
         }
     }
     return NULL;
@@ -235,101 +478,124 @@ rconn_recv(struct rconn *rc)
 /* Causes the next call to poll_block() to wake up when a packet may be ready
  * to be received by vconn_recv() on 'rc'.  */
 void
-rconn_recv_wait(struct rconn *rc) 
+rconn_recv_wait(struct rconn *rc)
 {
     if (rc->vconn) {
         vconn_wait(rc->vconn, WAIT_RECV);
     }
 }
 
-/* Sends 'b' on 'rc'.  Returns 0 if successful, EAGAIN if at least 'txq_limit'
- * packets are already queued, otherwise a positive errno value. */
+/* Sends 'b' on 'rc'.  Returns 0 if successful (in which case 'b' is
+ * destroyed), or ENOTCONN if 'rc' is not currently connected (in which case
+ * the caller retains ownership of 'b').
+ *
+ * If 'n_queued' is non-null, then '*n_queued' will be incremented while the
+ * packet is in flight, then decremented when it has been sent (or discarded
+ * due to disconnection).  Because 'b' may be sent (or discarded) before this
+ * function returns, the caller may not be able to observe any change in
+ * '*n_queued'.
+ *
+ * There is no rconn_send_wait() function: an rconn has a send queue that it
+ * takes care of sending if you call rconn_run(), which will have the side
+ * effect of waking up poll_block(). */
 int
-do_send(struct rconn *rc, struct buffer *b, int txq_limit)
+rconn_send(struct rconn *rc, struct ofpbuf *b, int *n_queued)
 {
-    if (rc->vconn) {
-        if (rc->txq.n < txq_limit) {
-            queue_push_tail(&rc->txq, b);
-            if (rc->txq.n == 1) {
-                try_send(rc);
-            }
-            return 0;
-        } else {
-            return EAGAIN;
+    if (rconn_is_connected(rc)) {
+        copy_to_monitor(rc, b);
+        b->private = n_queued;
+        if (n_queued) {
+            ++*n_queued;
         }
+        queue_push_tail(&rc->txq, b);
+        if (rc->txq.n == 1) {
+            try_send(rc);
+        }
+        return 0;
     } else {
         return ENOTCONN;
     }
 }
 
-/* Sends 'b' on 'rc'.  Returns 0 if successful, EAGAIN if the send queue is
- * full, or ENOTCONN if 'rc' is not currently connected.
+/* Sends 'b' on 'rc'.  Increments '*n_queued' while the packet is in flight; it
+ * will be decremented when it has been sent (or discarded due to
+ * disconnection).  Returns 0 if successful, EAGAIN if '*n_queued' is already
+ * at least as large as 'queue_limit', or ENOTCONN if 'rc' is not currently
+ * connected.  Regardless of return value, 'b' is destroyed.
+ *
+ * Because 'b' may be sent (or discarded) before this function returns, the
+ * caller may not be able to observe any change in '*n_queued'.
  *
  * There is no rconn_send_wait() function: an rconn has a send queue that it
  * takes care of sending if you call rconn_run(), which will have the side
  * effect of waking up poll_block(). */
 int
-rconn_send(struct rconn *rc, struct buffer *b)
+rconn_send_with_limit(struct rconn *rc, struct ofpbuf *b,
+                      int *n_queued, int queue_limit)
 {
-    return do_send(rc, b, rc->txq_limit);
-}
-
-/* Sends 'b' on 'rc'.  Returns 0 if successful, EAGAIN if the send queue is
- * full, otherwise a positive errno value.
- *
- * Compared to rconn_send(), this function relaxes the queue limit, allowing
- * more packets than usual to be queued. */
-int
-rconn_force_send(struct rconn *rc, struct buffer *b)
-{
-    return do_send(rc, b, 2 * rc->txq_limit);
-}
-
-/* Returns true if 'rc''s send buffer is full,
- * false if it has room for at least one more packet. */
-bool
-rconn_is_full(const struct rconn *rc) 
-{
-    return rc->txq.n >= rc->txq_limit;
+    int retval;
+    retval = *n_queued >= queue_limit ? EAGAIN : rconn_send(rc, b, n_queued);
+    if (retval) {
+        ofpbuf_delete(b);
+    }
+    return retval;
 }
 
 /* Returns the total number of packets successfully sent on the underlying
  * vconn.  A packet is not counted as sent while it is still queued in the
  * rconn, only when it has been successfuly passed to the vconn.  */
 unsigned int
-rconn_packets_sent(const struct rconn *rc) 
+rconn_packets_sent(const struct rconn *rc)
 {
     return rc->packets_sent;
 }
 
+/* Adds 'vconn' to 'rc' as a monitoring connection, to which all messages sent
+ * and received on 'rconn' will be copied.  'rc' takes ownership of 'vconn'. */
+void
+rconn_add_monitor(struct rconn *rc, struct vconn *vconn)
+{
+    if (rc->n_monitors < ARRAY_SIZE(rc->monitors)) {
+        VLOG_WARN("new monitor connection from %s", vconn_get_name(vconn));
+        rc->monitors[rc->n_monitors++] = vconn;
+    } else {
+        VLOG_DBG("too many monitor connections, discarding %s",
+                 vconn_get_name(vconn));
+        vconn_close(vconn);
+    }
+}
+
 /* Returns 'rc''s name (the 'name' argument passed to rconn_new()). */
 const char *
-rconn_get_name(const struct rconn *rc) 
+rconn_get_name(const struct rconn *rc)
 {
     return rc->name;
 }
 
 /* Returns true if 'rconn' is connected or in the process of reconnecting,
- * false if 'rconn' is disconnected and will not be reconnected. */
+ * false if 'rconn' is disconnected and will not reconnect on its own. */
 bool
-rconn_is_alive(const struct rconn *rconn) 
+rconn_is_alive(const struct rconn *rconn)
 {
-    return rconn->reliable || rconn->vconn;
+    return rconn->state != S_VOID;
 }
 
 /* Returns true if 'rconn' is connected, false otherwise. */
 bool
 rconn_is_connected(const struct rconn *rconn)
 {
-    return rconn->vconn && !vconn_connect(rconn->vconn);
+    return is_connected_state(rconn->state);
 }
 
-/* Returns 0 if 'rconn' is connected, otherwise the number of seconds that it
- * has been disconnected. */
+/* Returns 0 if 'rconn' is connected.  Otherwise, if 'rconn' is in a "failure
+ * mode" (that is, it is not connected), returns the number of seconds that it
+ * has been in failure mode, ignoring any times that it connected but the
+ * controller's admission control policy caused it to be quickly
+ * disconnected. */
 int
-rconn_disconnected_duration(const struct rconn *rconn) 
+rconn_failure_duration(const struct rconn *rconn)
 {
-    return rconn_is_connected(rconn) ? 0 : time(0) - rconn->last_connected;
+    return rconn_is_connected(rconn) ? 0 : time_now() - rconn->last_admitted;
 }
 
 /* Returns the IP address of the peer, or 0 if the peer is not connected over
@@ -339,42 +605,111 @@ rconn_get_ip(const struct rconn *rconn)
 {
     return rconn->vconn ? vconn_get_ip(rconn->vconn) : 0;
 }
-
-static struct rconn *
-create_rconn(const char *name, int txq_limit, int probe_interval,
-             int max_backoff, struct vconn *vconn)
-{
-    struct rconn *rc = xmalloc(sizeof *rc);
-    assert(txq_limit > 0);
-    rc->reliable = vconn == NULL;
-    rc->connected = vconn != NULL;
-    rc->name = xstrdup(name);
-    rc->vconn = vconn;
-    queue_init(&rc->txq);
-    rc->txq_limit = txq_limit;
-    rc->backoff_deadline = time(0);
-    rc->backoff = 0;
-    rc->max_backoff = max_backoff ? max_backoff : 60;
-    rc->last_connected = time(0);
-    rc->probe_interval = (probe_interval
-                              ? MAX(5, probe_interval) : 0);
-    rc->probe_sent = 0;
-    rc->packets_sent = 0;
-    return rc;
+
+/* If 'rconn' can't connect to the peer, it could be for any number of reasons.
+ * Usually, one would assume it is because the peer is not running or because
+ * the network is partitioned.  But it could also be because the network
+ * topology has changed, in which case the upper layer will need to reassess it
+ * (in particular, obtain a new IP address via DHCP and find the new location
+ * of the controller).  When this appears that this might be the case, this
+ * function returns true.  It also clears the questionability flag and prevents
+ * it from being set again for some time. */
+bool
+rconn_is_connectivity_questionable(struct rconn *rconn)
+{
+    bool questionable = rconn->questionable_connectivity;
+    rconn->questionable_connectivity = false;
+    return questionable;
+}
+
+/* Returns the total number of packets successfully received by the underlying
+ * vconn.  */
+unsigned int
+rconn_packets_received(const struct rconn *rc)
+{
+    return rc->packets_received;
 }
 
+/* Returns a string representing the internal state of 'rc'.  The caller must
+ * not modify or free the string. */
+const char *
+rconn_get_state(const struct rconn *rc)
+{
+    return state_name(rc->state);
+}
+
+/* Returns the number of connection attempts made by 'rc', including any
+ * ongoing attempt that has not yet succeeded or failed. */
+unsigned int
+rconn_get_attempted_connections(const struct rconn *rc)
+{
+    return rc->n_attempted_connections;
+}
+
+/* Returns the number of successful connection attempts made by 'rc'. */
+unsigned int
+rconn_get_successful_connections(const struct rconn *rc)
+{
+    return rc->n_successful_connections;
+}
+
+/* Returns the time at which the last successful connection was made by
+ * 'rc'. */
+time_t
+rconn_get_last_connection(const struct rconn *rc)
+{
+    return rc->last_connected;
+}
+
+/* Returns the time at which 'rc' was created. */
+time_t
+rconn_get_creation_time(const struct rconn *rc)
+{
+    return rc->creation_time;
+}
+
+/* Returns the approximate number of seconds that 'rc' has been connected. */
+unsigned long int
+rconn_get_total_time_connected(const struct rconn *rc)
+{
+    return (rc->total_time_connected
+            + (rconn_is_connected(rc) ? elapsed_in_this_state(rc) : 0));
+}
+
+/* Returns the current amount of backoff, in seconds.  This is the amount of
+ * time after which the rconn will transition from BACKOFF to CONNECTING. */
+int
+rconn_get_backoff(const struct rconn *rc)
+{
+    return rc->backoff;
+}
+
+/* Returns the number of seconds spent in this state so far. */
+unsigned int
+rconn_get_state_elapsed(const struct rconn *rc)
+{
+    return elapsed_in_this_state(rc);
+}
+
 /* Tries to send a packet from 'rc''s send buffer.  Returns 0 if successful,
  * otherwise a positive errno value. */
 static int
 try_send(struct rconn *rc)
 {
     int retval = 0;
-    struct buffer *next = rc->txq.head->next;
+    struct ofpbuf *next = rc->txq.head->next;
+    int *n_queued = rc->txq.head->private;
     retval = vconn_send(rc->vconn, rc->txq.head);
     if (retval) {
+        if (retval != EAGAIN) {
+            disconnect(rc, retval);
+        }
         return retval;
     }
     rc->packets_sent++;
+    if (n_queued) {
+        --*n_queued;
+    }
     queue_advance_head(&rc->txq, next);
     return 0;
 }
@@ -383,33 +718,159 @@ try_send(struct rconn *rc)
  * nonzero, then it should be EOF to indicate the connection was closed by the
  * peer in a normal fashion or a positive errno value. */
 static void
-disconnect(struct rconn *rc, int error) 
+disconnect(struct rconn *rc, int error)
 {
-    time_t now = time(0);
-    
-    if (rc->vconn) {
-        if (error > 0) {
-            VLOG_WARN("%s: connection dropped (%s)",
-                      rc->name, strerror(error)); 
-        } else if (error == EOF) {
-            if (rc->reliable) {
-                VLOG_WARN("%s: connection closed", rc->name);
+    if (rc->reliable) {
+        time_t now = time_now();
+
+        if (rc->state & (S_CONNECTING | S_ACTIVE | S_IDLE)) {
+            if (error > 0) {
+                VLOG_WARN("%s: connection dropped (%s)",
+                          rc->name, strerror(error));
+            } else if (error == EOF) {
+                if (rc->reliable) {
+                    VLOG_WARN("%s: connection closed by peer", rc->name);
+                }
+            } else {
+                VLOG_WARN("%s: connection dropped", rc->name);
             }
+            vconn_close(rc->vconn);
+            rc->vconn = NULL;
+            flush_queue(rc);
+        }
+
+        if (now >= rc->backoff_deadline) {
+            rc->backoff = 1;
         } else {
-            VLOG_WARN("%s: connection dropped", rc->name); 
+            rc->backoff = MIN(rc->max_backoff, MAX(1, 2 * rc->backoff));
+            VLOG_WARN("%s: waiting %d seconds before reconnect\n",
+                      rc->name, rc->backoff);
         }
-        vconn_close(rc->vconn);
-        rc->vconn = NULL;
-        queue_clear(&rc->txq);
+        rc->backoff_deadline = now + rc->backoff;
+        state_transition(rc, S_BACKOFF);
+        if (now - rc->last_connected > 60) {
+            question_connectivity(rc);
+        }
+    } else {
+        rconn_disconnect(rc);
     }
+}
 
-    if (now >= rc->backoff_deadline) {
-        rc->backoff = 1;
-    } else {
-        rc->backoff = MIN(rc->max_backoff, MAX(1, 2 * rc->backoff));
-        VLOG_WARN("%s: waiting %d seconds before reconnect\n",
-                  rc->name, rc->backoff);
+/* Drops all the packets from 'rc''s send queue and decrements their queue
+ * counts. */
+static void
+flush_queue(struct rconn *rc)
+{
+    if (!rc->txq.n) {
+        return;
+    }
+    while (rc->txq.n > 0) {
+        struct ofpbuf *b = queue_pop_head(&rc->txq);
+        int *n_queued = b->private;
+        if (n_queued) {
+            --*n_queued;
+        }
+        ofpbuf_delete(b);
+    }
+    poll_immediate_wake();
+}
+
+static unsigned int
+elapsed_in_this_state(const struct rconn *rc)
+{
+    return time_now() - rc->state_entered;
+}
+
+static unsigned int
+timeout(const struct rconn *rc)
+{
+    switch (rc->state) {
+#define STATE(NAME, VALUE) case S_##NAME: return timeout_##NAME(rc);
+        STATES
+#undef STATE
+    default:
+        NOT_REACHED();
+    }
+}
+
+static bool
+timed_out(const struct rconn *rc)
+{
+    return time_now() >= sat_add(rc->state_entered, timeout(rc));
+}
+
+static void
+state_transition(struct rconn *rc, enum state state)
+{
+    if (is_connected_state(state) && !is_connected_state(rc->state)) {
+        rc->probably_admitted = false;
+    }
+    if (rconn_is_connected(rc)) {
+        rc->total_time_connected += elapsed_in_this_state(rc);
+    }
+    VLOG_DBG("%s: entering %s", rc->name, state_name(state));
+    rc->state = state;
+    rc->state_entered = time_now();
+}
+
+static void
+question_connectivity(struct rconn *rc) 
+{
+    time_t now = time_now();
+    if (now - rc->last_questioned > 60) {
+        rc->questionable_connectivity = true;
+        rc->last_questioned = now;
     }
-    rc->backoff_deadline = now + rc->backoff;
-    rc->probe_sent = 0;
+}
+
+static void
+copy_to_monitor(struct rconn *rc, const struct ofpbuf *b)
+{
+    struct ofpbuf *clone = NULL;
+    int retval;
+    size_t i;
+
+    for (i = 0; i < rc->n_monitors; ) {
+        struct vconn *vconn = rc->monitors[i];
+
+        if (!clone) {
+            clone = ofpbuf_clone(b);
+        }
+        retval = vconn_send(vconn, clone);
+        if (!retval) {
+            clone = NULL;
+        } else if (retval != EAGAIN) {
+            VLOG_DBG("%s: closing monitor connection to %s: %s",
+                     rconn_get_name(rc), vconn_get_name(vconn),
+                     strerror(retval));
+            rc->monitors[i] = rc->monitors[--rc->n_monitors];
+            continue;
+        }
+        i++;
+    }
+    ofpbuf_delete(clone);
+}
+
+static bool
+is_connected_state(enum state state) 
+{
+    return (state & (S_ACTIVE | S_IDLE)) != 0;
+}
+
+static bool
+is_admitted_msg(const struct ofpbuf *b)
+{
+    struct ofp_header *oh = b->data;
+    uint8_t type = oh->type;
+    return !(type < 32
+             && (1u << type) & ((1u << OFPT_HELLO) |
+                                (1u << OFPT_ERROR) |
+                                (1u << OFPT_ECHO_REQUEST) |
+                                (1u << OFPT_ECHO_REPLY) |
+                                (1u << OFPT_VENDOR) |
+                                (1u << OFPT_FEATURES_REQUEST) |
+                                (1u << OFPT_FEATURES_REPLY) |
+                                (1u << OFPT_GET_CONFIG_REQUEST) |
+                                (1u << OFPT_GET_CONFIG_REPLY) |
+                                (1u << OFPT_SET_CONFIG)));
 }