man: document the new EmitLLDP= .network setting

Also, beef up the LLDP documentation a bit.

1 files changed, 22 insertions, 2 deletions

diff --git a/man/systemd.network.xml b/man/systemd.network.xml
index bbdcace563..b6f81cc9ba 100644
--- a/man/systemd.network.xml
+++ b/man/systemd.network.xml
@@ -335,17 +335,37 @@
         <varlistentry>
           <term><varname>LLDP=</varname></term>
           <listitem>
-            <para>Controls support for LLDP reception. Accepts a boolean or the special value
+            <para>Controls support for Ethernet LLDP packet reception. LLDP is a link-layer protocol commonly
+            implemented on professional routers and bridges which announces which physical port a system is connected
+            to, as well as other related data. Accepts a boolean or the special value
             <literal>routers-only</literal>. When true, incoming LLDP packets are accepted and a database of all LLDP
             neighbors maintained. If <literal>routers-only</literal> is set only LLDP data of various types of routers
             is collected and LLDP data about other types of devices ignored (such as stations, telephones and
             others). If false, LLDP reception is disabled. Defaults to <literal>routers-only</literal>. Use
             <citerefentry><refentrytitle>networkctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> to query the
-            collected neighbor data.
+            collected neighbor data. LLDP is only available on Ethernet links. See <varname>EmitLLDP=</varname> below
+            for enabling LLDP packet emission from the local system.
             </para>
           </listitem>
         </varlistentry>
         <varlistentry>
+          <term><varname>EmitLLDP=</varname></term>
+          <listitem>
+            <para>Controls support for Ethernet LLDP packet emission. Accepts a boolean parameter and defaults to
+            false. If enabled a short LLDP packet with information about the local system is sent out in regular
+            intervals on the link. The LLDP packet will contain information about the local host name, the local
+            machine ID (as stored in
+            <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>) and the
+            local interface name, as well as the pretty hostname of the system (as set in
+            <citerefentry><refentrytitle>machine-info</refentrytitle><manvolnum>5</manvolnum></citerefentry>). LLDP
+            emission is only available on Ethernet links. Note that this setting passed data suitable for
+            identification of host to the network and should thus not be used on untrusted networks, where such
+            identification data should not be made available. Use this option to enable other systems to identify on
+            which interface they are connected to this system. See <varname>LLDP=</varname> above for an option to
+            enable LLDP reception.</para>
+          </listitem>
+        </varlistentry>
+        <varlistentry>
           <term><varname>BindCarrier=</varname></term>
           <listitem>
             <para>A port or a list of ports. When set, controls the