BIRD: WIP adding direct protocol

docs/routing/bird/bird.md

@@ -103,6 +103,25 @@ filter crxnFilter
 
 TODO: Add a check about not installing RTD_UNREACHABLEs which babel will generate sometimes and which BIRD reportedly has undefined behavior with
 
+### Direct protocol
+
+TODO: fix/finish this section
+
+This provides BIRD with a manner of picking up the `subnet/prefix` pair that is assigned to local interfaces such that these can be imported into BIRD and later advertised.
+
+```
+protocol direct crxnDirect
+{
+    ipv6
+    {
+        table crxn;
+        import filter crxnFilter;
+    };
+    # Interfaces to find neighbours on
+    interface "eth*";
+}
+```
+
 ---
 
 Old stuff below WIP):