and HTML-ize this, too

diff --git a/doc/antora/modules/raddb/pages/mods-available/icmp.adoc b/doc/antora/modules/raddb/pages/mods-available/icmp.adoc
new file mode 100644 (file)
index 0000000..c309f3f
--- /dev/null
+++ b/doc/antora/modules/raddb/pages/mods-available/icmp.adoc
@@ -0,0 +1,56 @@
+
+
+
+
+= ICMP Module
+
+The module `icmp` is used for sending ICMP Echo Request messages.
+
+This module is useful only for `xlat`.  Use it via the following expansion:
+
+
+The module will "ping" the given IP address.  If that IP address responds
+with an ICMP Echo Reply, then the result of the expansion will be `yes`.
+If that IP address does not respond within the timeout, then the result
+of the expansion will be `no`.
+
+The IP address does not have to be a fixed string.  It can be another
+expansion, such as:
+
+
+
+
+
+## Configuration Settings
+
+
+interface:: Which interface to use for sending ICMP packets.
+
+By default, packets are sent via the normal routing table.
+
+Specifying an interface forces the packets to be sent via
+that particular interface.
+
+
+
+timeout:: How long to wait for the reply.
+
+Default is `1` seconds, which should be plenty for nearly
+anything. Range is `0.1s` to `10s`.
+
+WARNING: You are strongly encouraged to NOT increase this
+value.  In fact, you are much better off decreasing it to a
+lower value.  Doing so will improve network stability and
+responsiveness.
+
+
+== Default Configuration
+
+```
+#      `%{icmp:192.0.2.1}`
+#      `%{icmp:%{NAS-IP-Address}}`
+icmp {
+#      interface = eth0
+       timeout = 1s
+}
+```