ofproto: Prefer "master" and "other" connections for snooping over "slave".

This makes "ovs-ofctl snoop" and anything else that connects to the
switch's "snoop" socket typically more useful in the presence of multiple
controllers, since the "master" connection is the one with the most
interesting traffic.

Suggested-by: Justin Pettit <jpettit@nicira.com>

diff --git a/ofproto/ofproto.c b/ofproto/ofproto.c
index 0ee69effbe6f978a149582b01001f3587ccd6518..dcf8683ff37ea007a41d75e1fc375c2b1e0e71e6 100644 (file)
--- a/ofproto/ofproto.c
+++ b/ofproto/ofproto.c
@@ -963,25 +963,47 @@ process_port_change(struct ofproto *ofproto, int error, char *devname)
     }
 }
 
+/* Returns a "preference level" for snooping 'ofconn'.  A higher return value
+ * means that 'ofconn' is more interesting for monitoring than a lower return
+ * value. */
+static int
+snoop_preference(const struct ofconn *ofconn)
+{
+    switch (ofconn->role) {
+    case NX_ROLE_MASTER:
+        return 3;
+    case NX_ROLE_OTHER:
+        return 2;
+    case NX_ROLE_SLAVE:
+        return 1;
+    default:
+        /* Shouldn't happen. */
+        return 0;
+    }
+}
+
 /* One of ofproto's "snoop" pvconns has accepted a new connection on 'vconn'.
  * Connects this vconn to a controller. */
 static void
 add_snooper(struct ofproto *ofproto, struct vconn *vconn)
 {
-    struct ofconn *ofconn;
+    struct ofconn *ofconn, *best;
 
-    /* Arbitrarily pick the first controller in the list for monitoring.  We
-     * could do something smarter or more flexible later, if it ever proves
-     * useful. */
+    /* Pick a controller for monitoring. */
+    best = NULL;
     LIST_FOR_EACH (ofconn, struct ofconn, node, &ofproto->all_conns) {
-        if (ofconn->type == OFCONN_CONTROLLER) {
-            rconn_add_monitor(ofconn->rconn, vconn);
-            return;
+        if (ofconn->type == OFCONN_CONTROLLER
+            && (!best || snoop_preference(ofconn) > snoop_preference(best))) {
+            best = ofconn;
         }
+    }
 
+    if (best) {
+        rconn_add_monitor(best->rconn, vconn);
+    } else {
+        VLOG_INFO_RL(&rl, "no controller connection to snoop");
+        vconn_close(vconn);
     }
-    VLOG_INFO_RL(&rl, "no controller connection to monitor");
-    vconn_close(vconn);
 }
 
 int

diff --git a/utilities/ovs-ofctl.8.in b/utilities/ovs-ofctl.8.in
index d84b4819be92cdb09eb9a776172ae0c695503f95..8d48d98a323e64e76f10dbd0e413b4a96ffdebd4 100644 (file)
--- a/utilities/ovs-ofctl.8.in
+++ b/utilities/ovs-ofctl.8.in
@@ -155,8 +155,16 @@ Thus, this command can be used to view OpenFlow protocol activity
 between a switch and its controller.
 .IP
 When a switch has more than one controller configured, only the
-protocol to and from a single controller, chosen arbitrarily by Open
-vSwitch, is given.  If a switch has no controller configured, or if
+traffic to and from a single controller is output.  If none of the
+controllers is configured as a master or a slave (using a Nicira
+extension to OpenFlow), then a controller is chosen arbitrarily among
+them.  If there is a master controller, it is chosen; otherwise, if
+there are any controllers that are not masters or slaves, one is
+chosen arbitrarily; otherwise, a slave controller is chosen
+arbitrarily.  This choice is made once at connection time and does not
+change as controllers reconfigure their roles.
+.IP
+If a switch has no controller configured, or if
 the configured controller is disconnected, no traffic is sent, so
 monitoring will not show any traffic.
 .