arm: add why when to set 'require-server-cookie yes;'

diff --git a/doc/arm/Bv9ARM-book.xml b/doc/arm/Bv9ARM-book.xml
index 3051411d74220c259745c7f56bb074556ec4e644..c6f6ec18356e8876913045f3d0b60a98c03650f3 100644 (file)
--- a/doc/arm/Bv9ARM-book.xml
+++ b/doc/arm/Bv9ARM-book.xml
@@ -6011,6 +6011,12 @@ options {
                  server cookie.
                  The default is <userinput>no</userinput>.
                </para>
+               <para>
+                 Set this to <userinput>yes</userinput> to test that DNS
+                 COOKIE clients correctly handle BADCOOKIE or if you are
+                 getting a lot of forged DNS requests with DNS COOKIES
+                 present.
+               </para>
              </listitem>
            </varlistentry>