Add 'Upgrade' header parsing

Not parsing product tokens, I don't see much point.

src/cowboy_http_req.erl

@@ -227,13 +227,7 @@ parse_header(Name, Req=#http_req{p_headers=PHeaders}) ->
 
 %% @doc Default values for semantic header parsing.
 -spec parse_header_default(http_header()) -> any().
-parse_header_default('Accept') -> undefined;
-parse_header_default('Accept-Charset') -> undefined;
-parse_header_default('Accept-Encoding') -> undefined;
-parse_header_default('Accept-Language') -> undefined;
 parse_header_default('Connection') -> [];
-parse_header_default('If-Match') -> undefined;
-parse_header_default('If-None-Match') -> undefined;
 parse_header_default(_Name) -> undefined.
 
 %% @doc Semantically parse headers.
@@ -288,6 +282,11 @@ parse_header(Name, Req, Default)
 		fun (Value) ->
 			cowboy_http:http_date(Value)
 		end);
+parse_header(Name, Req, Default) when Name =:= 'Upgrade' ->
+	parse_header(Name, Req, Default,
+		fun (Value) ->
+			cowboy_http:nonempty_list(Value, fun cowboy_http:token_ci/2)
+		end);
 parse_header(Name, Req, Default) ->
 	{Value, Req2} = header(Name, Req, Default),
 	{undefined, Value, Req2}.

src/cowboy_http_websocket.erl

@@ -72,16 +72,13 @@ upgrade(ListenerPid, Handler, Opts, Req) ->
 		{'EXIT', _Reason} -> upgrade_error(Req)
 	end.
 
-%% @todo We need a function to properly parse headers according to their ABNF,
-%%       instead of having ugly code like this case here.
-%% @todo Upgrade is a list of products and should be parsed as such.
 -spec websocket_upgrade(#state{}, #http_req{}) -> {ok, #state{}, #http_req{}}.
 websocket_upgrade(State, Req) ->
 	{ConnTokens, Req2}
 		= cowboy_http_req:parse_header('Connection', Req),
 	true = lists:member(<<"upgrade">>, ConnTokens),
-	{WS, Req3} = cowboy_http_req:header('Upgrade', Req2),
-	<<"websocket">> = cowboy_bstr:to_lower(WS),
+	%% @todo Should probably send a 426 if the Upgrade header is missing.
+	{[<<"websocket">>], Req3} = cowboy_http_req:parse_header('Upgrade', Req2),
 	{Version, Req4} = cowboy_http_req:header(<<"Sec-Websocket-Version">>, Req3),
 	websocket_upgrade(Version, State, Req4).