doc, tools: Update to code to show example MAX_FDS

Place in the code the ability for end operators to know how
to modify MAX_FDS so that they can run large scale operations.

Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>

doc/user/setup.rst

@@ -6,8 +6,8 @@ Basic Setup
 After installing FRR, some basic configuration must be completed before it is
 ready to use.
 
-Daemons File
+Daemons Configuration File
-------------
+--------------------------
 After a fresh install, starting FRR will do nothing. This is because daemons
 must be explicitly enabled by editing a file in your configuration directory.
 This file is usually located at :file:`/etc/frr/daemons` and determines which
@@ -34,19 +34,6 @@ systemd. The file initially looks like this:
    bfdd=no
    fabricd=no
 
-To enable a particular daemon, simply change the corresponding 'no' to 'yes'.
-Subsequent service restarts should start the daemon.
-
-Daemons Configuration File
---------------------------
-There is another file that controls the default options passed to daemons when
-starting FRR as a service. This file is located in your configuration
-directory, usually at :file:`/etc/frr/daemons`.
-
-This file has several parts. Here is an example:
-
-::
-
    #
    # If this option is set the /etc/init.d/frr script automatically loads
    # the config via "vtysh -b" when the servers are started.
@@ -71,6 +58,7 @@ This file has several parts. Here is an example:
    bfdd_options="  --daemon -A 127.0.0.1"
    fabricd_options="  --daemon -A 127.0.0.1"
 
+   #MAX_FDS=1024
    # The list of daemons to watch is automatically generated by the init script.
    #watchfrr_options=""
 
@@ -83,6 +71,13 @@ This file has several parts. Here is an example:
 
 Breaking this file down:
 
+::
+
+  bgpd=yes
+
+To enable a particular daemon, simply change the corresponding 'no' to 'yes'.
+Subsequent service restarts should start the daemon.
+
 ::
 
    vtysh_enable=yes
@@ -91,6 +86,16 @@ As the comment says, this causes :ref:`VTYSH <vty-shell>` to apply
 configuration when starting the daemons. This is useful for a variety of
 reasons touched on in the VTYSH documentation and should generally be enabled.
 
+::
+
+   MAX_FDS=1024
+
+This allows the operator to control the number of open file descriptors
+each daemon is allowed to start with.  The current assumed value on
+most operating systems is 1024.  If the operator plans to run bgp with
+several thousands of peers than this is where we would modify FRR to
+allow this to happen.
+
 ::
 
    zebra_options=" -s 90000000 --daemon -A 127.0.0.1"

tools/etc/frr/daemons

@@ -56,6 +56,14 @@ bfdd_options="   -A 127.0.0.1"
 fabricd_options="-A 127.0.0.1"
 vrrpd_options="  -A 127.0.0.1"
 
+#
+# This is the maximum number of FD's that will be available.
+# Upon startup this is read by the control files and ulimit
+# is called.  Uncomment and use a reasonable value for your
+# setup if you are expecting a large number of peers in
+# say BGP.
+#MAX_FDS=1024
+
 # The list of daemons to watch is automatically generated by the init script.
 #watchfrr_options=""