%%% @doc MASQUE CONNECT-UDP listener over HTTP/2.
%%%
%%% Wraps `h2:start_server/3' with a handler fun that validates the
%%% Extended CONNECT envelope (RFC 8441 + RFC 9298), matches the
%%% request path against the configured URI template, and spawns a
%%% per-tunnel `masque_h2_server_session' on acceptance.
%%%
%%% For the cert/key config this follows `erlang_h2' conventions:
%%% both are PEM file paths (string or binary). `quic_h3' takes DER
%%% binaries, so the `masque' facade exposes two distinct start
%%% functions and the test helpers keep both forms around.
-module(masque_h2_server).
-export([
start_listener/2,
stop_listener/1,
h2_handlers/1,
try_reserve_tunnel/2,
release_tunnel/1
]).
-include("masque.hrl").
-include("masque_ip.hrl").
-type listener_name() :: atom().
-type listener_opts() :: map().
-export_type([listener_name/0, listener_opts/0]).
%%====================================================================
%% API
%%====================================================================
-spec start_listener(listener_name(), listener_opts()) ->
{ok, h2:server_ref()} | {error, term()}.
start_listener(Name, Opts0) when is_atom(Name), is_map(Opts0) ->
persistent_term:erase({masque_drain, Name}),
Opts = defaults(Opts0),
Port = maps:get(port, Opts),
#{handler := Handler} = h2_handlers(Opts#{drain_key => Name}),
ServerOpts = #{
cert => maps:get(cert, Opts),
key => maps:get(key, Opts),
handler => Handler,
enable_connect_protocol => true,
settings => merged_settings(Opts)
},
ServerOpts1 = case maps:find(acceptors, Opts) of
{ok, N} -> ServerOpts#{acceptors => N};
error -> ServerOpts
end,
case h2:start_server(Name, Port, ServerOpts1) of
{ok, Ref} ->
persistent_term:put({masque_h2_ref, Name}, Ref),
persistent_term:put({masque_h2_name, Ref}, Name),
{ok, Ref};
Error -> Error
end.
-spec stop_listener(h2:server_ref() | listener_name()) -> ok | {error, term()}.
stop_listener({_, _, _} = Ref) ->
case persistent_term:get({masque_h2_name, Ref}, undefined) of
undefined -> ok;
Name ->
persistent_term:erase({masque_drain, Name}),
persistent_term:erase({masque_h2_ref, Name}),
persistent_term:erase({masque_h2_name, Ref})
end,
h2:stop_server(Ref);
stop_listener(Name) when is_atom(Name) ->
case persistent_term:get({masque_h2_ref, Name}, undefined) of
undefined ->
{error, {no_ref_for_name, Name}};
Ref ->
stop_listener(Ref)
end.
-spec h2_handlers(map()) ->
#{handler := fun((pid(), non_neg_integer(), binary(), binary(),
list()) -> any())}.
h2_handlers(Opts0) ->
Opts = defaults(Opts0),
Dispatch = build_dispatch(Opts),
#{handler => make_dispatch_fun(Dispatch)}.
%%====================================================================
%% Internal
%%====================================================================
defaults(Opts) ->
D = #{
uri_template => ?MASQUE_DEFAULT_URI_TEMPLATE,
tcp_uri_template => ?MASQUE_DEFAULT_TCP_URI_TEMPLATE,
ip_uri_template => ?MASQUE_DEFAULT_IP_URI_PATH_PATTERN,
handler => masque_udp_proxy_handler,
tcp_handler => masque_tcp_proxy_handler,
ip_handler => masque_ip_proxy_handler,
bind_handler => masque_udp_bind_proxy_handler,
accept_bind => false
},
maps:merge(D, Opts).
default_resolver(Host) when is_binary(Host) ->
default_resolver(binary_to_list(Host));
default_resolver(Host) when is_list(Host) ->
V4 = case inet_res:lookup(Host, in, a) of
[] -> []; Xs -> Xs
end,
V6 = case inet_res:lookup(Host, in, aaaa) of
[] -> []; Ys -> Ys
end,
case V4 ++ V6 of
[] -> {error, nxdomain};
Addrs -> {ok, Addrs}
end.
%% RFC 9298 requires `SETTINGS_ENABLE_CONNECT_PROTOCOL = 1'.
%% `h2:start_server/3' also honors `enable_connect_protocol => true'
%% directly; merging into `settings' is a no-op for those paths but
%% keeps user-supplied tuning (e.g. SETTINGS_MAX_FRAME_SIZE).
merged_settings(Opts) ->
User = maps:get(settings, Opts, #{}),
User#{enable_connect_protocol => 1}.
build_dispatch(Opts) ->
#{udp_template => maps:get(uri_template, Opts),
tcp_template => maps:get(tcp_uri_template, Opts),
ip_template => maps:get(ip_uri_template, Opts),
udp_handler => maps:get(handler, Opts),
tcp_handler => maps:get(tcp_handler, Opts),
ip_handler => maps:get(ip_handler, Opts),
bind_handler => maps:get(bind_handler, Opts),
accept_bind => maps:get(accept_bind, Opts),
resolver => maps:get(resolver, Opts, fun default_resolver/1),
handler_opts => maps:merge(
maps:merge(
maps:with([address_pool, routes, mtu], Opts),
maps:with(
[bind_address, bind_port, bind_socket_opts,
public_addresses, public_address_fun,
peer_filter_fun, scrub_fun, allow_private,
allow_loopback,
max_compression_contexts,
max_compression_contexts_in,
max_compression_contexts_out,
max_pending_compression_responses], Opts)),
maps:get(handler_opts, Opts, #{})),
fallback => maps:get(fallback, Opts, undefined),
max_tunnels => maps:get(max_tunnels_per_connection, Opts, 0),
name => maps:get(drain_key, Opts, undefined)}.
make_dispatch_fun(Dispatch) ->
fun(Conn, StreamId, Method, Path, Headers) ->
dispatch_request(Conn, StreamId, Method, Path, Headers, Dispatch)
end.
dispatch_request(Conn, StreamId, Method, Path, Headers, Dispatch) ->
case masque:is_draining(maps:get(name, Dispatch, undefined)) of
true ->
reject(Conn, StreamId, overload);
false ->
dispatch_request_1(Conn, StreamId, Method, Path, Headers,
Dispatch)
end.
dispatch_request_1(Conn, StreamId, Method, Path, Headers, Dispatch) ->
#{udp_template := UdpTpl, tcp_template := TcpTpl,
ip_template := IpTpl,
udp_handler := UdpHandler, tcp_handler := TcpHandler,
ip_handler := IpHandler,
bind_handler := BindHandler,
accept_bind := AcceptBind,
resolver := Resolver,
handler_opts := HandlerOpts, fallback := Fallback} = Dispatch,
case validate(Method, Path, Headers, UdpTpl, TcpTpl, IpTpl,
AcceptBind) of
{ok, Req0} ->
Protocol = maps:get(protocol, Req0),
HandlerMod = case Protocol of
udp -> UdpHandler;
tcp -> TcpHandler;
ip -> IpHandler;
udp_bind -> BindHandler
end,
Req1 = Req0#{handler_opts => HandlerOpts},
case resolve_target(Protocol, Req1, Resolver) of
{ok, Req} ->
MaxT = maps:get(max_tunnels, Dispatch, 0),
case accept_request(HandlerMod, Req) of
accept when MaxT > 0 ->
case try_reserve_tunnel(Conn, MaxT) of
true ->
spawn_session(Conn, StreamId, Protocol,
HandlerMod, HandlerOpts, Req);
false ->
reject(Conn, StreamId, overload)
end;
accept ->
spawn_session(Conn, StreamId, Protocol,
HandlerMod, HandlerOpts, Req);
{reject, Reason} ->
reject(Conn, StreamId, Reason);
{reject, Reason, Extra} when is_list(Extra) ->
reject(Conn, StreamId, Reason, Extra)
end;
{error, Reason} ->
reject(Conn, StreamId, Reason)
end;
{error, Reason} ->
case Fallback of
undefined ->
reject(Conn, StreamId, Reason);
Fun when is_function(Fun, 5) ->
Fun(Conn, StreamId, Method, Path, Headers)
end
end.
%% RFC 9484 §4.7.1 — hostname targets resolved before accept/1
resolve_target(ip, #{ip_target := Target} = Req, Resolver)
when is_binary(Target) ->
case Resolver(Target) of
{ok, Addrs} -> {ok, Req#{resolved_addresses => Addrs}};
{error, _} -> {error, resolution_failed}
end;
resolve_target(ip, #{ip_target := {_,_,_,_} = A} = Req, _Resolver) ->
{ok, Req#{resolved_addresses => [A]}};
resolve_target(ip, #{ip_target := {_,_,_,_,_,_,_,_} = A} = Req, _Resolver) ->
{ok, Req#{resolved_addresses => [A]}};
resolve_target(ip, Req, _Resolver) ->
{ok, Req#{resolved_addresses => []}};
resolve_target(_, Req, _Resolver) ->
{ok, Req}.
spawn_session(Conn, StreamId, Protocol, Handler, HOpts, Req) ->
Args = #{conn => Conn, stream_id => StreamId,
protocol => Protocol, transport => h2,
handler => Handler, handler_opts => HOpts, req => Req},
case masque_h2_session_sup:start_session(Args) of
{ok, _Pid} -> ok;
{error, Reason} -> reject(Conn, StreamId, map_init_error(Reason))
end.
map_init_error({resolution_failed, _}) -> resolution_failed;
map_init_error({reject, Err}) -> Err;
map_init_error(_) -> resolution_failed.
validate(Method, Path, Headers, UdpTemplate, TcpTemplate, IpTemplate,
AcceptBind) ->
case Method of
<<"CONNECT">> ->
Protocol = header(<<":protocol">>, Headers),
case Protocol of
?MASQUE_CONNECT_UDP_PROTOCOL when AcceptBind ->
match_udp_or_bind(Path, Headers, UdpTemplate);
?MASQUE_CONNECT_UDP_PROTOCOL ->
match_path(Path, Headers, UdpTemplate, udp);
?MASQUE_CONNECT_TCP_PROTOCOL ->
match_path(Path, Headers, TcpTemplate, tcp);
?MASQUE_CONNECT_IP_PROTOCOL ->
match_ip_path(Path, Headers, IpTemplate);
_ ->
{error, bad_protocol}
end;
_ ->
{error, bad_method}
end.
match_udp_or_bind(Path, Headers, Template) ->
case masque_uri_udp_bind:parse_bind_header(Headers) of
bind ->
case masque_uri_udp_bind:match(Template, Path) of
{ok, #{target_host := Host, target_port := Port,
bind := Scope}} ->
Authority = case header(<<":authority">>, Headers) of
undefined -> <<"">>;
A -> A
end,
Scheme = case header(<<":scheme">>, Headers) of
undefined -> <<"https">>;
S -> S
end,
{ok, #{
method => <<"CONNECT">>,
protocol => udp_bind,
bind => Scope,
path => Path,
authority => Authority,
scheme => Scheme,
target_host => Host,
target_port => Port,
headers => Headers
}};
{error, bad_port} -> {error, bad_port};
{error, bad_host} -> {error, bad_host};
{error, _} -> {error, bad_path}
end;
_ ->
match_path(Path, Headers, Template, udp)
end.
%% h2_connection strips `:scheme' and `:authority' from the handler
%% headers (they stay in the stream record but are not exposed). We
%% still populate the Req map with best-effort values so the handler
%% callback sees a consistent shape on both transports.
match_path(Path, Headers, Template, Protocol) ->
case masque_uri:match(Template, Path) of
{ok, #{target_host := Host, target_port := Port}} ->
Authority = case header(<<":authority">>, Headers) of
undefined -> header(<<"host">>, Headers, <<>>);
A -> A
end,
{ok, #{
method => <<"CONNECT">>,
protocol => Protocol,
path => Path,
authority => Authority,
scheme => <<"https">>,
target_host => Host,
target_port => Port,
headers => Headers
}};
{error, bad_port} -> {error, bad_port};
{error, bad_host} -> {error, bad_host};
{error, _} -> {error, bad_path}
end.
match_ip_path(Path, Headers, Template) ->
case masque_uri_ip:parse_server_template(Template) of
{ok, T} ->
case masque_uri_ip:match(T, Path) of
{ok, #{target := Target, ipproto := IPProto}} ->
Authority = case header(<<":authority">>, Headers) of
undefined -> header(<<"host">>, Headers, <<>>);
A -> A
end,
{ok, #{
method => <<"CONNECT">>,
protocol => ip,
path => Path,
authority => Authority,
scheme => <<"https">>,
ip_target => Target,
ip_ipproto => IPProto,
headers => Headers
}};
{error, bad_target} -> {error, bad_host};
{error, bad_ipproto} -> {error, bad_port};
{error, _} -> {error, bad_path}
end;
{error, _} ->
{error, bad_path}
end.
header(Name, Headers, Default) ->
case lists:keyfind(Name, 1, Headers) of
{_, V} -> V;
false -> Default
end.
accept_request(HandlerMod, Req) ->
_ = code:ensure_loaded(HandlerMod),
case erlang:function_exported(HandlerMod, accept, 1) of
true -> HandlerMod:accept(Req);
false -> masque_handler:default_accept(Req)
end.
reject(Conn, StreamId, Reason) ->
reject(Conn, StreamId, Reason, []).
reject(Conn, StreamId, Reason, ExtraHeaders) ->
masque_metrics:tunnel_rejected(#{reason => Reason}),
Status = masque_errors:handshake_status(Reason),
Phrase = masque_errors:status_reason(Reason),
Body = <<Phrase/binary, "\n">>,
Base = [
{<<"content-type">>, <<"text/plain; charset=utf-8">>},
{<<"content-length">>, integer_to_binary(byte_size(Body))},
{<<"proxy-status">>, proxy_status_field(Reason)}
],
Headers = merge_extra_headers(Base, ExtraHeaders),
ok = h2:send_response(Conn, StreamId, Status, Headers),
ok = h2:send_data(Conn, StreamId, Body, true).
merge_extra_headers(Base, []) ->
Base;
merge_extra_headers(Base, Extra) ->
Keys = [K || {K, _} <- Extra],
Kept = [Pair || {K, _} = Pair <- Base, not lists:member(K, Keys)],
Extra ++ Kept.
proxy_status_field(Reason) ->
Error = proxy_status_error(Reason),
<<"masque; error=", Error/binary>>.
proxy_status_error(bad_method) -> <<"http_protocol_error">>;
proxy_status_error(bad_protocol) -> <<"http_protocol_error">>;
proxy_status_error(bad_path) -> <<"http_protocol_error">>;
proxy_status_error(bad_port) -> <<"http_protocol_error">>;
proxy_status_error(bad_host) -> <<"http_protocol_error">>;
proxy_status_error(resolution_failed) -> <<"dns_error">>;
proxy_status_error(upstream_timeout) -> <<"connection_timeout">>;
proxy_status_error(forbidden) -> <<"destination_ip_prohibited">>;
proxy_status_error(loop_detected) -> <<"proxy_loop_detected">>;
proxy_status_error(overload) -> <<"proxy_internal_error">>;
proxy_status_error(_) -> <<"proxy_internal_error">>.
header(Name, Headers) ->
case lists:keyfind(Name, 1, Headers) of
{_, V} -> V;
false -> undefined
end.
%%====================================================================
%% Per-connection tunnel counting
%%====================================================================
-spec try_reserve_tunnel(pid(), pos_integer()) -> boolean().
try_reserve_tunnel(Conn, Max) ->
_ = ets:insert_new(masque_h2_tunnel_counts, {Conn, 0}),
New = ets:update_counter(masque_h2_tunnel_counts, Conn, {2, 1}),
case New > Max of
true ->
_ = ets:update_counter(masque_h2_tunnel_counts, Conn, {2, -1}),
false;
false ->
true
end.
-spec release_tunnel(pid()) -> ok.
release_tunnel(Conn) ->
_ = try ets:update_counter(masque_h2_tunnel_counts, Conn, {2, -1, 0, 0})
catch error:badarg -> ok
end,
ok.