Updated the documentation

Signed-off-by: Henrik Kjölhede <hkjolhede@gmail.com>

doc/lxc-usernet.sgml.in

@@ -63,6 +63,10 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
       <para>
       <command>user</command> <command>type</command> <command>bridge</command> <command>number</command>
       </para>
+      <para>or</para>
+      <para>
+      <command>@group</command> <command>type</command> <command>bridge</command> <command>number</command>
+      </para>
       <para>
       Where
       </para>
@@ -80,6 +84,17 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 	  </listitem>
 	</varlistentry>
 
+	<varlistentry>
+	  <term>
+	    <option>@group</option>
+	  </term>
+	  <listitem>
+	    <para>
+	      is the groupname to which this entry applies.
+	    </para>
+	  </listitem>
+	</varlistentry>
+
 	<varlistentry>
 	  <term>
 	    <option>type</option>
@@ -110,12 +125,22 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 	  </term>
 	  <listitem>
 	    <para>
-	      is the number of network interfaces of the given type which the
-	      given user may attach to the given bridge, for instance <filename>2</filename>.
+	      is the number or quota of network interfaces of the given type which the
+	      given user or group may attach to the given bridge, for instance <filename>2</filename>.
 	     </para>
 	  </listitem>
 	</varlistentry>
       </variablelist>
+
+      <para>
+        Since a user can be be specified both by username as well as one or 
+        more usergroups, it is possible that several configuration lines 
+        enable that user to create network interfaces. In such cases, any 
+        interfaces create are counted towards the quotas of the user or group 
+        in the order in which they appear in the file. If the quota of one 
+        line is full, the rest will be parsed until one is found or the end of 
+        the file.
+      </para>
     </refsect2>
 
   </refsect1>