diff --git a/lib/conntest.ml b/lib/conntest.ml
index e2c95fc..6c97f76 100644
--- a/lib/conntest.ml
+++ b/lib/conntest.ml
@@ -132,6 +132,27 @@ module Make
       done;
       !acc
 
+      let map_rev_shortcircuit f r =
+        let i = ref 0 in
+        let len = length r in
+        let ring_copy = Array.copy r.ring in
+        while !i < len do
+          let idx_opt = wrap_reverse_i r !i in
+          match idx_opt with
+          | None -> i := len
+          | Some idx ->
+            let value_opt = get_previous r !i in
+            match value_opt with
+            | None -> ring_copy.(idx) <- None; i := succ !i
+            | Some x ->
+              match f x with
+              | None -> i := len
+              | Some y ->
+                ring_copy.(idx) <- Some y; i := succ !i
+        done;
+        { r with ring = ring_copy }
+    
+
   end
 
   module Udp_flow = struct
@@ -348,6 +369,27 @@ module Make
                 *)
                 Log.debug (fun m -> m "feed_source: packet_index_diff < 0");
                 let did_set = ref false in
+                let map_rev_shortcircuit f r =
+                  let i = ref 0 in
+                  let len = Ring.length r in
+                  let ring_copy = Array.copy r.Ring.ring in
+                  while !i < len do
+                    let idx_opt = Ring.wrap_reverse_i r !i in
+                    match idx_opt with
+                    | None -> i := len
+                    | Some idx ->
+                      let value_opt = Ring.get_previous r !i in
+                      match value_opt with
+                      | None -> ring_copy.(idx) <- None; i := succ !i
+                      | Some x ->
+                        match f x with
+                        | None -> i := len
+                        | Some y ->
+                          ring_copy.(idx) <- Some y; i := succ !i
+                  done;
+                  { r with Ring.ring = ring_copy }
+                
+                in
                 (*> goto perf; could use something like 'find_map_rev'
                   * which would try the latest packets first -
                     * which should be more often hit