diff --git a/docs/changes.txt b/docs/changes.txt
index 3f5b767..76d76bb 100644
--- a/docs/changes.txt
+++ b/docs/changes.txt
@@ -74,3 +74,7 @@ v0.6
 * nfqws2: reasm support negative overlaps. gaps are not supported.
 * nfqws2,zapret-auto: changed retransmission detection scheme.
 * zapret-auto: udp_in/udp_out failure detection
+
+v0.6.1
+
+* zapret-lib, zapret-auto: condition and stopif orchestrators
diff --git a/lua/zapret-auto.lua b/lua/zapret-auto.lua
index 7e9115f..0ea49bb 100644
--- a/lua/zapret-auto.lua
+++ b/lua/zapret-auto.lua
@@ -255,3 +255,54 @@ function circular(ctx, desync)
 
 	return verdict
 end
+
+-- test iff functions
+function cond_true(desync)
+	return true
+end
+function cond_false(desync)
+	return false
+end
+-- arg: percent - of true . 50 by default
+function cond_random(desync)
+	return math.random(0,99)<(tonumber(desync.arg.percent) or 50)
+end
+-- check iff function available. error if not
+function require_iff(desync, name)
+	if not desync.arg.iff then
+		error(name..": missing 'iff' function")
+	end
+	if type(_G[desync.arg.iff])~="function" then
+		error(name..": invalid 'iff' function '"..desync.arg.iff.."'")
+	end
+end
+-- execute further desync instances only if user-provided 'iff' function returns true
+-- for example, this can be used by custom protocol detectors
+-- arg: iff - condition function. takes desync as arg and returns bool. (cant use 'if' because of reserved word)
+-- arg: neg - invert condition function result
+function condition(ctx, desync)
+	require_iff(desync, "condition")
+	orchestrate(ctx, desync)
+	if logical_xor(_G[desync.arg.iff](desync), desync.arg.neg) then
+		DLOG("condition: true")
+		return replay_execution_plan(desync)
+	else
+		DLOG("condition: false")
+		plan_clear(desync)
+	end
+end
+-- clear execution plan if user provided 'iff' functions returns true
+-- can be used with other orchestrators to stop execution conditionally
+-- arg: iff - condition function. takes desync as arg and returns bool. (cant use 'if' because of reserved word)
+-- arg: neg - invert condition function result
+function stopif(ctx, desync)
+	require_iff(desync, "stopif")
+	orchestrate(ctx, desync)
+	if logical_xor(_G[desync.arg.iff](desync), desync.arg.neg) then
+		DLOG("stopif: true")
+		plan_clear(desync)
+	else
+		-- do not do anything. allow other orchestrator to finish the plan
+		DLOG("stopif: false")
+	end
+end
diff --git a/lua/zapret-lib.lua b/lua/zapret-lib.lua
index 30c9c37..f1e75bb 100644
--- a/lua/zapret-lib.lua
+++ b/lua/zapret-lib.lua
@@ -156,6 +156,9 @@ end
 function plan_instance_pop(desync)
 	return (desync.plan and #desync.plan>0) and table.remove(desync.plan, 1)
 end
+function plan_clear(desync)
+	while table.remove(desync.plan) do end
+end
 -- this approach allows nested orchestrators
 function orchestrate(ctx, desync)
 	if not desync.plan then
@@ -170,6 +173,10 @@ function desync_copy(desync)
 		-- preserve lua state
 		dcopy.track.lua_state = desync.track.lua_state
 	end
+	if desync.plan then
+		-- preserve execution plan
+		dcopy.plan = desync.plan
+	end
 	return dcopy
 end
 -- redo what whould be done without orchestration
@@ -318,6 +325,9 @@ function str_or_hex(s)
 		return s
 	end
 end
+function logical_xor(a,b)
+	return a and not b or not a and b
+end
 -- print to DLOG any variable. tables are expanded in the tree form, unprintables strings are hex dumped
 function var_debug(v)
 	local function dbg(v,level)