Flush timeout message from message queue when canceling timer

In ct_netconfc, if a timer expired 'at the same time' as the server
sent the rpc-reply, the timeout message might already be in the
client's message queue when the client removed the timer ref from its
'pending' list. This caused a crash in the client since the timer ref
could no longer be found when handling the timeout message.

This commit fixes the problem by always flushing the timeout message
from the message queue when canceling a timer.

1 files changed, 18 insertions, 10 deletions

diff --git a/lib/common_test/src/ct_netconfc.erl b/lib/common_test/src/ct_netconfc.erl
index 0de7bf03af..05977e5649 100644
--- a/lib/common_test/src/ct_netconfc.erl
+++ b/lib/common_test/src/ct_netconfc.erl
@@ -1272,6 +1272,14 @@ set_request_timer(T) ->
     {ok,TRef} = timer:send_after(T,{Ref,timeout}),
     {Ref,TRef}.
 
+%%%-----------------------------------------------------------------
+cancel_request_timer(undefined,undefined) ->
+    ok;
+cancel_request_timer(Ref,TRef) ->
+    _ = timer:cancel(TRef),
+    receive {Ref,timeout} -> ok
+    after 0 -> ok
+    end.
 
 %%%-----------------------------------------------------------------
 client_hello(Options) when is_list(Options) ->
@@ -1404,9 +1412,9 @@ handle_error(Reason, State) ->
 		   Pending ->
 		       %% Assuming the first request gets the
 		       %% first answer
-		       P=#pending{tref=TRef,caller=Caller} =
+		       P=#pending{tref=TRef,ref=Ref,caller=Caller} =
 			   lists:last(Pending),
-		       _ = timer:cancel(TRef),
+		       cancel_request_timer(Ref,TRef),
 		       Reason1 = {failed_to_parse_received_data,Reason},
 		       ct_gen_conn:return(Caller,{error,Reason1}),
 		       lists:delete(P,Pending)
@@ -1492,8 +1500,8 @@ decode({Tag,Attrs,_}=E, #state{connection=Connection,pending=Pending}=State) ->
 			{error,Reason} ->
 			    {noreply,State#state{hello_status = {error,Reason}}}
 		    end;
-		#pending{tref=TRef,caller=Caller} ->
-		    _ = timer:cancel(TRef),
+		#pending{tref=TRef,ref=Ref,caller=Caller} ->
+		    cancel_request_timer(Ref,TRef),
 		    case decode_hello(E) of
 			{ok,SessionId,Capabilities} ->
 			    ct_gen_conn:return(Caller,ok),
@@ -1519,9 +1527,8 @@ decode({Tag,Attrs,_}=E, #state{connection=Connection,pending=Pending}=State) ->
 	    %% there is just one pending that matches (i.e. has
 	    %% undefined msg_id and op)
 	    case [P || P = #pending{msg_id=undefined,op=undefined} <- Pending] of
-		[#pending{tref=TRef,
-			  caller=Caller}] ->
-		    _ = timer:cancel(TRef),
+		[#pending{tref=TRef,ref=Ref,caller=Caller}] ->
+		    cancel_request_timer(Ref,TRef),
 		    ct_gen_conn:return(Caller,E),
 		    {noreply,State#state{pending=[]}};
 		_ ->
@@ -1542,8 +1549,8 @@ get_msg_id(Attrs) ->
 
 decode_rpc_reply(MsgId,{_,Attrs,Content0}=E,#state{pending=Pending} = State) ->
     case lists:keytake(MsgId,#pending.msg_id,Pending) of
-	{value, #pending{tref=TRef,op=Op,caller=Caller}, Pending1} ->
-	    _ = timer:cancel(TRef),
+	{value, #pending{tref=TRef,ref=Ref,op=Op,caller=Caller}, Pending1} ->
+	    cancel_request_timer(Ref,TRef),
 	    Content = forward_xmlns_attr(Attrs,Content0),
 	    {CallerReply,{ServerReply,State2}} =
 		do_decode_rpc_reply(Op,Content,State#state{pending=Pending1}),
@@ -1555,10 +1562,11 @@ decode_rpc_reply(MsgId,{_,Attrs,Content0}=E,#state{pending=Pending} = State) ->
 	    %% pending that matches (i.e. has undefined msg_id and op)
 	    case [P || P = #pending{msg_id=undefined,op=undefined} <- Pending] of
 		[#pending{tref=TRef,
+			  ref=Ref,
 			  msg_id=undefined,
 			  op=undefined,
 			  caller=Caller}] ->
-		    _ = timer:cancel(TRef),
+		    cancel_request_timer(Ref,TRef),
 		    ct_gen_conn:return(Caller,E),
 		    {noreply,State#state{pending=[]}};
 		_ ->