fix: handle race condition in get_protocol calls

src/hackney.erl

@@ -245,13 +245,13 @@ try_new_h3_connection(Host, Port, Transport, Options, PoolHandler) ->
           case hackney_conn:connect(ConnPid, ConnectTimeout) of
             ok ->
               %% Verify it's HTTP/3
-              case hackney_conn:get_protocol(ConnPid) of
+              case catch hackney_conn:get_protocol(ConnPid) of
                 http3 ->
                   %% Register for multiplexing
                   PoolHandler:register_h3(Host, Port, Transport, ConnPid, Options),
                   {ok, ConnPid};
                 _ ->
-                  %% Not HTTP/3, close and fail
+                  %% Not HTTP/3 or connection terminated, close and fail
                   catch hackney_conn:stop(ConnPid),
                   hackney_altsvc:mark_h3_blocked(Host, Port),
                   false
@@ -302,12 +302,18 @@ connect_pool_new(Transport, Host, Port, Options, PoolHandler) ->
   end.
 
 %% @private Register HTTP/2 connection for multiplexing if applicable
+%% Uses catch to handle race condition where connection terminates before call
 maybe_register_h2(ConnPid, Host, Port, Transport, Options, PoolHandler) ->
-  case hackney_conn:get_protocol(ConnPid) of
+  case catch hackney_conn:get_protocol(ConnPid) of
     http2 ->
       %% HTTP/2 negotiated - register for connection sharing
       PoolHandler:register_h2(Host, Port, Transport, ConnPid, Options);
     http1 ->
+      ok;
+    http3 ->
+      ok;
+    {'EXIT', _} ->
+      %% Connection terminated before we could check - ignore
       ok
   end.
 

src/hackney_pool.erl

@@ -23,7 +23,8 @@
 %% HTTP/2 connection pooling
 -export([checkout_h2/4,
          register_h2/5,
-         unregister_h2/2]).
+         unregister_h2/2,
+         unregister_h2_all/0]).
 
 %% HTTP/3 connection pooling
 -export([checkout_h3/4,
@@ -173,6 +174,13 @@ unregister_h2(Pid, Options) ->
     gen_server:cast(Pool, {unregister_h2, Pid}),
     ok.
 
+%% @doc Remove all HTTP/2 connections from the default pool.
+%% Used for testing to ensure clean state between tests.
+-spec unregister_h2_all() -> ok.
+unregister_h2_all() ->
+    Pool = find_pool(default, []),
+    gen_server:call(Pool, unregister_h2_all).
+
 %%====================================================================
 %% HTTP/3 Connection Pooling
 %%====================================================================
@@ -508,7 +516,11 @@ handle_call({checkout_h3, Key}, _From, #state{h3_connections = H3Conns} = State)
                     H3Conns2 = maps:remove(Key, H3Conns),
                     {reply, none, State#state{h3_connections = H3Conns2}}
             end
-    end.
+    end;
+
+handle_call(unregister_h2_all, _From, State) ->
+    %% Clear all HTTP/2 connections (for testing)
+    {reply, ok, State#state{h2_connections = #{}}}.
 
 handle_cast({checkin, _PoolInfo, Pid}, State) ->
     State2 = do_checkin(Pid, State),