Support AMQP over WebSocket in Erlang client

 ## What?
Implement the AMQP over WebSocket Binding Committee Specification 01 in
the AMQP 1.0 Erlang client:
https://docs.oasis-open.org/amqp-bindmap/amqp-wsb/v1.0/cs01/amqp-wsb-v1.0-cs01.html

 ## Why?
1. This allows writing integration tests for the server implementation
   of AMQP over WebSocket.
2. Erlang and Elixir clients can use AMQP over WebSocket in environments
   where firewalls prohibit access to the AMQP port.

 ## How?
Use gun as WebSocket client.

The new module `amqp10_client_socket` handles socket operations (open, close, send) for:
* TCP sockets
* SSL sockets
* WebSockets

Prior to this commit, the amqp10_client_connection process closed only the
write end of the socket after it sent the AMQP close performative.
This commit removed premature socket closure because:
1. There is no equivalent feature provided in Gun since sending a
   WebSocket close frame causes Gun to cleanly close the connection for
   both writing and reading.
2. It's unnecessary and can result in unexpected and confusing behaviour on the server.
3. It's better practive to keep the TCP connection fully open until
   the AMQP closing handshake completes.
4. When amqp10_client_frame_reader terminates, it will cleanly close
   the socket for both writing and reading.

deps/amqp10_client/Makefile

@@ -29,7 +29,7 @@ endef
 PACKAGES_DIR ?= $(abspath PACKAGES)
 
 BUILD_DEPS = rabbit_common elvis_mk
-DEPS = amqp10_common credentials_obfuscation
+DEPS = amqp10_common credentials_obfuscation gun
 TEST_DEPS = rabbit rabbitmq_ct_helpers
 LOCAL_DEPS = ssl inets crypto public_key
 

deps/amqp10_client/src/amqp10_client_connection.erl

@@ -43,8 +43,6 @@
 
 -export([format_status/1]).
 
--type amqp10_socket() :: {tcp, gen_tcp:socket()} | {ssl, ssl:sslsocket()}.
-
 -type milliseconds() :: non_neg_integer().
 
 -type address() :: inet:socket_address() | inet:hostname().
@@ -60,6 +58,8 @@
       address => address(),
       port => inet:port_number(),
       tls_opts => {secure_port, [ssl:tls_option()]},
+      ws_path => string(),
+      ws_opts => gun:opts(),
       notify => pid() | none, % the pid to send connection events to
       notify_when_opened => pid() | none,
       notify_when_closed => pid() | none,
@@ -83,14 +83,13 @@
          sessions_sup :: pid() | undefined,
          pending_session_reqs = [] :: [term()],
          reader :: pid() | undefined,
-         socket :: amqp10_socket() | undefined,
+         socket :: amqp10_client_socket:socket() | undefined,
          idle_time_out :: non_neg_integer() | undefined,
          heartbeat_timer :: timer:tref() | undefined,
          config :: connection_config()
         }).
 
--export_type([connection_config/0,
-              amqp10_socket/0]).
+-export_type([connection_config/0]).
 
 %% -------------------------------------------------------------------
 %% Public API.
@@ -152,7 +151,7 @@ start_link(Sup, Config) ->
 set_other_procs(Pid, OtherProcs) ->
     gen_statem:cast(Pid, {set_other_procs, OtherProcs}).
 
--spec socket_ready(pid(), amqp10_socket()) -> ok.
+-spec socket_ready(pid(), amqp10_client_socket:socket()) -> ok.
 socket_ready(Pid, Socket) ->
     gen_statem:cast(Pid, {socket_ready, Socket}).
 
@@ -186,10 +185,10 @@ expecting_socket(_EvtType, {socket_ready, Socket},
     Sasl = credentials_obfuscation:decrypt(maps:get(sasl, Cfg)),
     case Sasl of
         none ->
-            ok = socket_send(Socket, ?AMQP_PROTOCOL_HEADER),
+            ok = amqp10_client_socket:send(Socket, ?AMQP_PROTOCOL_HEADER),
             {next_state, hdr_sent, State1};
         _ ->
-            ok = socket_send(Socket, ?SASL_PROTOCOL_HEADER),
+            ok = amqp10_client_socket:send(Socket, ?SASL_PROTOCOL_HEADER),
             {next_state, sasl_hdr_sent, State1}
     end;
 expecting_socket(_EvtType, {set_other_procs, OtherProcs}, State) ->
@@ -205,9 +204,12 @@ expecting_socket({call, From}, begin_session,
 sasl_hdr_sent(_EvtType, {protocol_header_received, 3, 1, 0, 0}, State) ->
     {next_state, sasl_hdr_rcvds, State};
 sasl_hdr_sent({call, From}, begin_session,
-               #state{pending_session_reqs = PendingSessionReqs} = State) ->
+              #state{pending_session_reqs = PendingSessionReqs} = State) ->
     State1 = State#state{pending_session_reqs = [From | PendingSessionReqs]},
-    {keep_state, State1}.
+    {keep_state, State1};
+sasl_hdr_sent(info, {'DOWN', MRef, process, _Pid, _},
+              #state{reader_m_ref = MRef}) ->
+    {stop, {shutdown, reader_down}}.
 
 sasl_hdr_rcvds(_EvtType, #'v1_0.sasl_mechanisms'{
                             sasl_server_mechanisms = {array, symbol, AvailableMechs}},
@@ -228,7 +230,7 @@ sasl_hdr_rcvds({call, From}, begin_session,
 
 sasl_init_sent(_EvtType, #'v1_0.sasl_outcome'{code = {ubyte, 0}},
                #state{socket = Socket} = State) ->
-    ok = socket_send(Socket, ?AMQP_PROTOCOL_HEADER),
+    ok = amqp10_client_socket:send(Socket, ?AMQP_PROTOCOL_HEADER),
     {next_state, hdr_sent, State};
 sasl_init_sent(_EvtType, #'v1_0.sasl_outcome'{code = {ubyte, C}},
                #state{} = State) when C==1;C==2;C==3;C==4 ->
@@ -285,7 +287,7 @@ open_sent({call, From}, begin_session,
           #state{pending_session_reqs = PendingSessionReqs} = State) ->
     State1 = State#state{pending_session_reqs = [From | PendingSessionReqs]},
     {keep_state, State1};
-open_sent(info, {'DOWN', MRef, _, _, _},
+open_sent(info, {'DOWN', MRef, process, _, _},
           #state{reader_m_ref = MRef}) ->
     {stop, {shutdown, reader_down}}.
 
@@ -294,46 +296,56 @@ opened(_EvtType, heartbeat, State = #state{idle_time_out = T}) ->
     {ok, Tmr} = start_heartbeat_timer(T),
     {keep_state, State#state{heartbeat_timer = Tmr}};
 opened(_EvtType, {close, Reason}, State) ->
-    %% We send the first close frame and wait for the reply.
     %% TODO: stop all sessions writing
     %% We could still accept incoming frames (See: 2.4.6)
     case send_close(State, Reason) of
-        ok              -> {next_state, close_sent, State};
-        {error, closed} -> {stop, normal, State};
-        Error           -> {stop, Error, State}
+        ok ->
+            %% "After writing this frame the peer SHOULD continue to read from the connection
+            %% until it receives the partner's close frame (in order to guard against
+            %% erroneously or maliciously implemented partners, a peer SHOULD implement a
+            %% timeout to give its partner a reasonable time to receive and process the close
+            %% before giving up and simply closing the underlying transport mechanism)." [§2.4.3]
+            {next_state, close_sent, State, {state_timeout, ?TIMEOUT, received_no_close_frame}};
+        {error, closed} ->
+            {stop, normal, State};
+        Error ->
+            {stop, Error, State}
     end;
 opened(_EvtType, #'v1_0.close'{} = Close, State = #state{config = Config}) ->
     %% We receive the first close frame, reply and terminate.
     ok = notify_closed(Config, Close),
-    _ = send_close(State, none),
-    {stop, normal, State};
+    case send_close(State, none) of
+        ok              -> {stop, normal, State};
+        {error, closed} -> {stop, normal, State};
+        Error           -> {stop, Error, State}
+    end;
 opened({call, From}, begin_session, State) ->
     {Ret, State1} = handle_begin_session(From, State),
     {keep_state, State1, [{reply, From, Ret}]};
-opened(info, {'DOWN', MRef, _, _, _Info},
-            State = #state{reader_m_ref = MRef, config = Config}) ->
+opened(info, {'DOWN', MRef, process, _, _Info},
+       #state{reader_m_ref = MRef, config = Config}) ->
     %% reader has gone down and we are not already shutting down
     ok = notify_closed(Config, shutdown),
-    {stop, normal, State};
+    {stop, normal};
 opened(_EvtType, Frame, State) ->
     logger:warning("Unexpected connection frame ~tp when in state ~tp ",
-                             [Frame, State]),
-    {keep_state, State}.
+                   [Frame, State]),
+    keep_state_and_data.
 
-close_sent(_EvtType, heartbeat, State) ->
-    {next_state, close_sent, State};
-close_sent(_EvtType, {'EXIT', _Pid, shutdown}, State) ->
+close_sent(_EvtType, heartbeat, _Data) ->
+    keep_state_and_data;
+close_sent(_EvtType, {'EXIT', _Pid, shutdown}, _Data) ->
     %% monitored processes may exit during closure
-    {next_state, close_sent, State};
-close_sent(_EvtType, {'DOWN', _Ref, process, ReaderPid, _},
-           #state{reader = ReaderPid} = State) ->
-    %% if the reader exits we probably wont receive a close frame
-    {stop, normal, State};
-close_sent(_EvtType, #'v1_0.close'{} = Close, State = #state{config = Config}) ->
+    keep_state_and_data;
+close_sent(_EvtType, {'DOWN', _Ref, process, ReaderPid, _Reason},
+           #state{reader = ReaderPid}) ->
+    %% if the reader exits we probably won't receive a close frame
+    {stop, normal};
+close_sent(_EvtType, #'v1_0.close'{} = Close, #state{config = Config}) ->
     ok = notify_closed(Config, Close),
-    %% TODO: we should probably set up a timer before this to ensure
-    %% we close down event if no reply is received
-    {stop, normal, State}.
+    {stop, normal};
+close_sent(state_timeout, received_no_close_frame, _Data) ->
+    {stop, normal}.
 
 set_other_procs0(OtherProcs, State) ->
     #{sessions_sup := SessionsSup,
@@ -435,22 +447,15 @@ send_open(#state{socket = Socket, config = Config0}) ->
     Encoded = amqp10_framing:encode_bin(Open),
     Frame = amqp10_binary_generator:build_frame(0, Encoded),
     ?DBG("CONN <- ~tp", [Open]),
-    socket_send(Socket, Frame).
+    amqp10_client_socket:send(Socket, Frame).
 
 
 send_close(#state{socket = Socket}, _Reason) ->
     Close = #'v1_0.close'{},
     Encoded = amqp10_framing:encode_bin(Close),
     Frame = amqp10_binary_generator:build_frame(0, Encoded),
     ?DBG("CONN <- ~tp", [Close]),
-    Ret = socket_send(Socket, Frame),
-    case Ret of
-        ok -> _ =
-              socket_shutdown(Socket, write),
-              ok;
-        _  -> ok
-    end,
-    Ret.
+    amqp10_client_socket:send(Socket, Frame).
 
 send_sasl_init(State, anon) ->
     Frame = #'v1_0.sasl_init'{mechanism = {symbol, <<"ANONYMOUS">>}},
@@ -474,21 +479,11 @@ send(Record, FrameType, #state{socket = Socket}) ->
     Encoded = amqp10_framing:encode_bin(Record),
     Frame = amqp10_binary_generator:build_frame(0, FrameType, Encoded),
     ?DBG("CONN <- ~tp", [Record]),
-    socket_send(Socket, Frame).
+    amqp10_client_socket:send(Socket, Frame).
 
 send_heartbeat(#state{socket = Socket}) ->
     Frame = amqp10_binary_generator:build_heartbeat_frame(),
-    socket_send(Socket, Frame).
-
-socket_send({tcp, Socket}, Data) ->
-    gen_tcp:send(Socket, Data);
-socket_send({ssl, Socket}, Data) ->
-    ssl:send(Socket, Data).
-
-socket_shutdown({tcp, Socket}, How) ->
-    gen_tcp:shutdown(Socket, How);
-socket_shutdown({ssl, Socket}, How) ->
-    ssl:shutdown(Socket, How).
+    amqp10_client_socket:send(Socket, Frame).
 
 notify_opened(#{notify_when_opened := none}, _) ->
     ok;