Add Gun Websocket handlers and protocol support

This functionality can be used to implement custom protocols
on top of Websocket, but may also be used to decode frame
contents on the fly if necessary.

The default_protocol option defines what module should be
used when no protocol was selected.

The protocols option is a list of key/value pairs used to
select the handler depending on the protocol that the server
accepted.

The feature is currently experimental.

1 files changed, 46 insertions, 27 deletions

diff --git a/src/gun_http.erl b/src/gun_http.erl
index f5eef71..8ebd42e 100644
--- a/src/gun_http.erl
+++ b/src/gun_http.erl
@@ -29,7 +29,8 @@
 
 -type io() :: head | {body, non_neg_integer()} | body_close | body_chunked.
 
--type websocket_info() :: {websocket, reference(), binary(), [binary()], [], gun:ws_opts()}. %% key, extensions, protocols, options
+%% @todo Make that a record.
+-type websocket_info() :: {websocket, reference(), binary(), [binary()], gun:ws_opts()}. %% key, extensions, options
 
 -record(stream, {
 	ref :: reference() | websocket_info(),
@@ -164,8 +165,8 @@ handle_head(Data, State=#http_state{owner=Owner, version=ClientVersion,
 	{Version, Status, _, Rest} = cow_http:parse_status_line(Data),
 	{Headers, Rest2} = cow_http:parse_headers(Rest),
 	case {Status, StreamRef} of
-		{101, {websocket, _, WsKey, WsExtensions, WsProtocols, WsOpts}} ->
-			ws_handshake(Rest2, State, Headers, WsKey, WsExtensions, WsProtocols, WsOpts);
+		{101, {websocket, _, WsKey, WsExtensions, WsOpts}} ->
+			ws_handshake(Rest2, State, Headers, WsKey, WsExtensions, WsOpts);
 		_ ->
 			In = response_io_from_headers(Method, Version, Status, Headers),
 			IsFin = case In of head -> fin; _ -> nofin end,
@@ -174,7 +175,7 @@ handle_head(Data, State=#http_state{owner=Owner, version=ClientVersion,
 					ok;
 				true ->
 					StreamRef2 = case StreamRef of
-						{websocket, SR, _, _, _, _} -> SR;
+						{websocket, SR, _, _, _} -> SR;
 						_ -> StreamRef
 					end,
 					Owner ! {gun_response, self(), StreamRef2,
@@ -330,7 +331,7 @@ cancel(State, StreamRef) ->
 %% HTTP does not provide any way to figure out what streams are unprocessed.
 down(#http_state{streams=Streams}) ->
 	KilledStreams = [case Ref of
-		{websocket, Ref2, _, _, _, _} -> Ref2;
+		{websocket, Ref2, _, _, _} -> Ref2;
 		_ -> Ref
 	end || #stream{ref=Ref} <- Streams],
 	{KilledStreams, []}.
@@ -425,53 +426,59 @@ end_stream(State=#http_state{streams=[_|Tail]}) ->
 ws_upgrade(#http_state{version='HTTP/1.0'}, _, _, _, _, _, _) ->
 	error; %% @todo
 ws_upgrade(State=#http_state{socket=Socket, transport=Transport, out=head},
-		StreamRef, Host, Port, Path, Headers, WsOpts) ->
+		StreamRef, Host, Port, Path, Headers0, WsOpts) ->
 	{Headers1, GunExtensions} = case maps:get(compress, WsOpts, false) of
 		true -> {[{<<"sec-websocket-extensions">>,
 				<<"permessage-deflate; client_max_window_bits; server_max_window_bits=15">>}
-			|Headers],
+			|Headers0],
 			[<<"permessage-deflate">>]};
-		false -> {Headers, []}
+		false -> {Headers0, []}
+	end,
+	Headers2 = case maps:get(protocols, WsOpts, []) of
+		[] -> Headers1;
+		ProtoOpt ->
+			<< _, _, Proto/bits >> = iolist_to_binary([[<<", ">>, P] || {P, _} <- ProtoOpt]),
+			[{<<"sec-websocket-protocol">>, Proto}|Headers1]
 	end,
 	Key = cow_ws:key(),
-	Headers2 = [
+	Headers3 = [
 		{<<"connection">>, <<"upgrade">>},
 		{<<"upgrade">>, <<"websocket">>},
 		{<<"sec-websocket-version">>, <<"13">>},
 		{<<"sec-websocket-key">>, Key}
-		|Headers1
+		|Headers2
 	],
 	IsSecure = Transport:secure(),
-	Headers3 = case lists:keymember(<<"host">>, 1, Headers) of
-		true -> Headers2;
-		false when Port =:= 80, not IsSecure -> [{<<"host">>, Host}|Headers2];
-		false when Port =:= 443, IsSecure -> [{<<"host">>, Host}|Headers2];
-		false -> [{<<"host">>, [Host, $:, integer_to_binary(Port)]}|Headers2]
+	Headers = case lists:keymember(<<"host">>, 1, Headers0) of
+		true -> Headers3;
+		false when Port =:= 80, not IsSecure -> [{<<"host">>, Host}|Headers3];
+		false when Port =:= 443, IsSecure -> [{<<"host">>, Host}|Headers3];
+		false -> [{<<"host">>, [Host, $:, integer_to_binary(Port)]}|Headers3]
 	end,
-	Transport:send(Socket, cow_http:request(<<"GET">>, Path, 'HTTP/1.1', Headers3)),
+	Transport:send(Socket, cow_http:request(<<"GET">>, Path, 'HTTP/1.1', Headers)),
 	new_stream(State#http_state{connection=keepalive, out=head},
-		{websocket, StreamRef, Key, GunExtensions, [], WsOpts}, <<"GET">>).
+		{websocket, StreamRef, Key, GunExtensions, WsOpts}, <<"GET">>).
 
-ws_handshake(Buffer, State, Headers, Key, GunExtensions, GunProtocols, Opts) ->
+ws_handshake(Buffer, State, Headers, Key, GunExtensions, Opts) ->
 	%% @todo check upgrade, connection
 	case lists:keyfind(<<"sec-websocket-accept">>, 1, Headers) of
 		false ->
 			close;
 		{_, Accept} ->
 			case cow_ws:encode_key(Key) of
-				Accept -> ws_handshake_extensions(Buffer, State, Headers, GunExtensions, GunProtocols, Opts);
+				Accept -> ws_handshake_extensions(Buffer, State, Headers, GunExtensions, Opts);
 				_ -> close
 			end
 	end.
 
-ws_handshake_extensions(Buffer, State, Headers, GunExtensions, GunProtocols, Opts) ->
+ws_handshake_extensions(Buffer, State, Headers, GunExtensions, Opts) ->
 	case lists:keyfind(<<"sec-websocket-extensions">>, 1, Headers) of
 		false ->
-			ws_handshake_protocols(Buffer, State, Headers, #{}, GunProtocols);
+			ws_handshake_protocols(Buffer, State, Headers, #{}, Opts);
 		{_, ExtHd} ->
 			case ws_validate_extensions(cow_http_hd:parse_sec_websocket_extensions(ExtHd), GunExtensions, #{}, Opts) of
 				close -> close;
-				Extensions -> ws_handshake_protocols(Buffer, State, Headers, Extensions, GunProtocols)
+				Extensions -> ws_handshake_protocols(Buffer, State, Headers, Extensions, Opts)
 			end
 	end.
 
@@ -493,11 +500,23 @@ ws_validate_extensions(_, _, _, _) ->
 	close.
 
 %% @todo Validate protocols.
-ws_handshake_protocols(Buffer, State, Headers, Extensions, _GunProtocols = []) ->
-	Protocols = [],
-	ws_handshake_end(Buffer, State, Headers, Extensions, Protocols).
+ws_handshake_protocols(Buffer, State, Headers, Extensions, Opts) ->
+	case lists:keyfind(<<"sec-websocket-protocol">>, 1, Headers) of
+		false ->
+			ws_handshake_end(Buffer, State, Headers, Extensions,
+				maps:get(default_protocol, Opts, gun_ws_handler), Opts);
+		{_, Proto} ->
+			ProtoOpt = maps:get(protocols, Opts, []),
+			case lists:keyfind(Proto, 1, ProtoOpt) of
+				{_, Handler} ->
+					ws_handshake_end(Buffer, State, Headers, Extensions, Handler, Opts);
+				false ->
+					close
+			end
+	end.
 
-ws_handshake_end(Buffer, #http_state{owner=Owner, socket=Socket, transport=Transport}, Headers, Extensions, Protocols) ->
+ws_handshake_end(Buffer, #http_state{owner=Owner, socket=Socket, transport=Transport},
+		Headers, Extensions, Handler, Opts) ->
 	%% Send ourselves the remaining buffer, if any.
 	_ = case Buffer of
 		<<>> ->
@@ -506,4 +525,4 @@ ws_handshake_end(Buffer, #http_state{owner=Owner, socket=Socket, transport=Trans
 			{OK, _, _} = Transport:messages(),
 			self() ! {OK, Socket, Buffer}
 	end,
-	gun_ws:init(Owner, Socket, Transport, Headers, Extensions, Protocols).
+	gun_ws:init(Owner, Socket, Transport, Headers, Extensions, Handler, Opts).