[nft PATCH 4/4] doc: document monitor op

[Arturo Borrero Gonzalez <arturo.borrero.glez@gmail.com>]

Let's add some documentation about the monitor operation.

Signed-off-by: Arturo Borrero Gonzalez <arturo.borrero.glez@gmail.com>
---
 doc/nft.xml |   42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/doc/nft.xml b/doc/nft.xml
index 61ca03a..41c0840 100644
--- a/doc/nft.xml
+++ b/doc/nft.xml
@@ -2099,6 +2099,48 @@ filter input iif eth0 drop
 				</programlisting>
 			</para>
 		</refsect2>
+		<refsect2>
+			<title>monitor</title>
+			<para>
+				The monitor command allows you to listen to Netlink events produced
+				by the nf_tables subsystem, related to creation and deletion of objects.
+				When they ocurr, nft will print to stdout the monitored events in either
+				XML, JSON or native nft format.
+			</para>
+			<para>
+				To filter events related to a concrete object, use one of the keywords 'tables', 'chains', 'sets', 'rules', 'elements'.
+			</para>
+			<para>
+				To filter events related to a concrete action, use keyword 'new' or 'destroy'.
+			</para>
+			<para>
+				Hit ^C to finish the monitor operation.
+			</para>
+			<example>
+				<title>Listen to all events, report in native nft format</title>
+				<programlisting>
+% nft monitor
+				</programlisting>
+			</example>
+			<example>
+				<title>Listen to added tables, report in XML format</title>
+				<programlisting>
+% nft monitor new tables xml
+				</programlisting>
+			</example>
+			<example>
+				<title>Listen to deleted rules, report in JSON format</title>
+				<programlisting>
+% nft monitor destroy rules json
+				</programlisting>
+			</example>
+			<example>
+				<title>Listen to both new and destroyed chains, in native nft format</title>
+				<programlisting>
+% nft monitor chains
+				</programlisting>
+			</example>
+		</refsect2>
 	</refsect1>
 
 	<refsect1>