ovs-ofctl: Add "snoop" command.

The "snoop" command does roughly the same thing as "monitor", but it is
easier to use in the common case where one just wants to look at the
OpenFlow controller connection for a bridge.  Instead of, for example,
   ovs-ofctl monitor unix:/var/run/openvswitch/br0.snoop
one merely types
   ovs-ofctl snoop br0

1 files changed, 22 insertions, 5 deletions

diff --git a/utilities/ovs-ofctl.8.in b/utilities/ovs-ofctl.8.in
index 3c19be3d..d84b4819 100644
--- a/utilities/ovs-ofctl.8.in
+++ b/utilities/ovs-ofctl.8.in
@@ -143,8 +143,24 @@ omitted and the \fB--strict\fR option is not used, all flows in the
 switch's tables are removed.  See \fBFlow Syntax\fR, below, for the 
 syntax of \fIflows\fR.
 .
-.TP
-\fBmonitor \fIswitch\fR [\fImiss-len\fR]
+.IP "\fBsnoop \fIswitch\fR"
+Connects to \fIswitch\fR and prints to the console all OpenFlow
+messages received.  Unlike other \fBovs\-ofctl\fR commands, if
+\fIswitch\fR is the name of a bridge, then the \fBsnoop\fR command
+connects to a Unix domain socket named
+\fB@RUNDIR@/\fIbridge\fB.snoop\fR.  \fBovs\-vswitchd\fR listens on
+such a socket for each bridge and sends to it all of the OpenFlow
+messages sent to or received from its configured OpenFlow controller.
+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
+the configured controller is disconnected, no traffic is sent, so
+monitoring will not show any traffic.
+.
+.IQ "\fBmonitor \fIswitch\fR [\fImiss-len\fR]"
 Connects to \fIswitch\fR and prints to the console all OpenFlow
 messages received.  Usually, \fIswitch\fR should specify a connection
 named on \fBovs\-openflowd\fR(8)'s \fB-l\fR or \fB--listen\fR command line
@@ -152,10 +168,11 @@ option.
 .IP
 If \fImiss-len\fR is provided, \fBovs\-ofctl\fR sends an OpenFlow ``set
 configuration'' message at connection setup time that requests
-\fImiss-len\fR bytes of each packet that misses the flow table.  The
-OpenFlow reference implementation does not send these messages to the
+\fImiss-len\fR bytes of each packet that misses the flow table.  Open vSwitch
+does not send these and other asynchronous messages to an
 \fBovs\-ofctl monitor\fR client connection unless a nonzero value is
-specified on this argument.
+specified on this argument.  (Thus, if \fImiss\-len\fR is not
+specified, very little traffic will ordinarily be printed.)
 .IP
 This command may be useful for debugging switch or controller
 implementations.