'Host' header is optional in HTTP/1.0

Krishnamurthy, Kristol, Mogul: "Key Differences between HTTP/1.0
and HTTP/1.1", "Internet address conservation".
http://www8.org/w8-papers/5c-protocols/key/key.html

Fixes issue #35 reported by Alex Kropivny.

src/cowboy_http_protocol.erl

@@ -148,10 +148,12 @@ header({http_header, _I, 'Host', _R, RawHost}, Req=#http_req{
 	case catch cowboy_dispatcher:split_host(RawHost2) of
 		{Host, RawHost3, undefined} ->
 			Port = default_port(Transport:name()),
-			dispatch(Req#http_req{host=Host, raw_host=RawHost3, port=Port,
+			dispatch(fun parse_header/2, Req#http_req{
+				host=Host, raw_host=RawHost3, port=Port,
 				headers=[{'Host', RawHost3}|Req#http_req.headers]}, State);
 		{Host, RawHost3, Port} ->
-			dispatch(Req#http_req{host=Host, raw_host=RawHost3, port=Port,
+			dispatch(fun parse_header/2, Req#http_req{
+				host=Host, raw_host=RawHost3, port=Port,
 				headers=[{'Host', RawHost3}|Req#http_req.headers]}, State);
 		{'EXIT', _Reason} ->
 			error_terminate(400, State)
@@ -168,24 +170,30 @@ header({http_header, _I, Field, _R, Value}, Req, State) ->
 	Field2 = format_header(Field),
 	parse_header(Req#http_req{headers=[{Field2, Value}|Req#http_req.headers]},
 		State);
-%% The Host header is required.
-header(http_eoh, #http_req{host=undefined}, State) ->
+%% The Host header is required in HTTP/1.1.
+header(http_eoh, #http_req{version={1, 1}, host=undefined}, State) ->
 	error_terminate(400, State);
+%% It is however optional in HTTP/1.0.
+header(http_eoh, Req=#http_req{version={1, 0}, transport=Transport,
+		host=undefined}, State=#state{buffer=Buffer}) ->
+	Port = default_port(Transport:name()),
+	dispatch(fun handler_init/2, Req#http_req{host=[], raw_host= <<>>,
+		port=Port, buffer=Buffer}, State#state{buffer= <<>>});
 header(http_eoh, Req, State=#state{buffer=Buffer}) ->
 	handler_init(Req#http_req{buffer=Buffer}, State#state{buffer= <<>>});
 header({http_error, _Bin}, _Req, State) ->
 	error_terminate(500, State).
 
--spec dispatch(#http_req{}, #state{}) -> ok.
-dispatch(Req=#http_req{host=Host, path=Path},
+-spec dispatch(fun((#http_req{}, #state{}) -> ok),
+	#http_req{}, #state{}) -> ok.
+dispatch(Next, Req=#http_req{host=Host, path=Path},
 		State=#state{dispatch=Dispatch}) ->
 	%% @todo We probably want to filter the Host and Path here to allow
 	%%       things like url rewriting.
 	case cowboy_dispatcher:match(Host, Path, Dispatch) of
 		{ok, Handler, Opts, Binds, HostInfo, PathInfo} ->
-			parse_header(Req#http_req{host_info=HostInfo, path_info=PathInfo,
-				bindings=Binds},
-				State#state{handler={Handler, Opts}});
+			Next(Req#http_req{host_info=HostInfo, path_info=PathInfo,
+				bindings=Binds}, State#state{handler={Handler, Opts}});
 		{error, notfound, host} ->
 			error_terminate(400, State);
 		{error, notfound, path} ->

test/http_SUITE.erl

@@ -21,17 +21,18 @@
 -export([chunked_response/1, headers_dupe/1, headers_huge/1,
 	keepalive_nl/1, nc_rand/1, pipeline/1, raw/1, ws0/1, ws8/1]). %% http.
 -export([http_200/1, http_404/1]). %% http and https.
+-export([http_10_hostless/1]). %% misc.
 
 %% ct.
 
 all() ->
-	[{group, http}, {group, https}].
+	[{group, http}, {group, https}, {group, misc}].
 
 groups() ->
 	BaseTests = [http_200, http_404],
 	[{http, [], [chunked_response, headers_dupe, headers_huge,
 		keepalive_nl, nc_rand, pipeline, raw, ws0, ws8] ++ BaseTests},
-	{https, [], BaseTests}].
+	{https, [], BaseTests}, {misc, [], [http_10_hostless]}].
 
 init_per_suite(Config) ->
 	application:start(inets),
@@ -62,16 +63,24 @@ init_per_group(https, Config) ->
 			{keyfile, DataDir ++ "key.pem"}, {password, "cowboy"}],
 		cowboy_http_protocol, [{dispatch, init_https_dispatch()}]
 	),
-	[{scheme, "https"}, {port, Port}|Config].
+	[{scheme, "https"}, {port, Port}|Config];
+init_per_group(misc, Config) ->
+	Port = 33082,
+	cowboy:start_listener(misc, 100,
+		cowboy_tcp_transport, [{port, Port}],
+		cowboy_http_protocol, [{dispatch, [{'_', [
+			{[], http_handler, []}
+	]}]}]),
+	[{port, Port}|Config].
 
-end_per_group(http, _Config) ->
-	cowboy:stop_listener(http),
-	ok;
 end_per_group(https, _Config) ->
 	cowboy:stop_listener(https),
 	application:stop(ssl),
 	application:stop(public_key),
 	application:stop(crypto),
+	ok;
+end_per_group(Listener, _Config) ->
+	cowboy:stop_listener(Listener),
 	ok.
 
 %% Dispatch configuration.
@@ -309,3 +318,9 @@ http_200(Config) ->
 http_404(Config) ->
 	{ok, {{"HTTP/1.1", 404, "Not Found"}, _Headers, _Body}} =
 		httpc:request(build_url("/not/found", Config)).
+
+%% misc.
+
+http_10_hostless(Config) ->
+	Packet = "GET / HTTP/1.0\r\n\r\n",
+	{Packet, 200} = raw_req(Packet, Config).