update for new -tpg argument

rrqnet.8.adoc

@@ -25,7 +25,7 @@ OPTIONS
 
 Note that any options must be given in the fixed order:
 
-    [-v] [-4] [-B n] [-T n] [-m mcast] [-t tap]
+    [-v] [-tpg] [-4] [-B n] [-T n] [-m mcast] [-t tap]
 
 *-v*::
 
@@ -33,6 +33,13 @@ This tells *rrqnet* to log its operation on +stderr+. Use *-vv* to
 also see logs about connections and messaging, or *-vvv* for *rrqnet*
 to be insanely verbose on +stderr+ about virtually everything.
 
+-tpg::
+
+This enables a special UDP transport quirk where *rrqnet* expands any
+packet in the range [1461,1477] bytes to be of 1478 bytes instead. It
+is a work-around for an observed problem in a NAT traversal case for
+certain packet sizes in that range.
+
 *-4*::
 
 This directs *rrqnet* to use an ipv4-only socket for its UDP. By