%%% @doc Per-tunnel server session for Connect-UDP-Bind
%%% (draft-ietf-masque-connect-udp-listen-11). Sibling of
%%% `masque_server_session' / `masque_h2_server_session'; one module
%%% serves both h2 and h3 by dispatching on a `transport' field, the
%%% same shape used by `masque_ip_server_session'.
%%%
%%% Responsibilities:
%%%
%%% <ul>
%%% <li>Run the handler's `init/2' and splice the resulting
%%% `{response_headers, _}' action into the 2xx response so the
%%% proxy emits `Connect-UDP-Bind: ?1' and `Proxy-Public-Address'.</li>
%%% <li>Own the per-session compression tables (own + peer, via
%%% `masque_compression_table').</li>
%%% <li>Drain capsules off the request stream and dispatch
%%% `COMPRESSION_ASSIGN' / `ACK' / `CLOSE' to the table; pass
%%% any other capsule to the handler's `handle_capsule/3'.</li>
%%% <li>Decode incoming HTTP datagrams: extract context-id, look up
%%% the compression-table entry, decode the inner Bound UDP
%%% Proxying Payload via `masque_udp_bind_payload', and call
%%% `masque_udp_bind_proxy_handler:handle_bind_packet/3'.</li>
%%% <li>Apply handler actions (`{send_bind_packet, Peer, Bytes}',
%%% `{compression_assign, _}', `{compression_ack, _}',
%%% `{compression_close, _}', plus the legacy `send_capsule' /
%%% `close_session').</li>
%%% </ul>
%%%
%%% Deliberately minimal in this first PR:
%%%
%%% <ul>
%%% <li>Wait-for-ACK on send is implemented via the table's
%%% `state' field; an outbound mapping is `pending_ack' until
%%% `COMPRESSION_ACK' arrives. The session emits compressed
%%% payloads only against `installed' entries; otherwise it
%%% falls through to the uncompressed channel if open, or
%%% drops the packet.</li>
%%% <li>The `max_pending_compression_responses' bound and the
%%% post-close prohibition are deferred to a follow-up PR; the
%%% hooks are in place but the policy is permissive.</li>
%%% </ul>
-module(masque_udp_bind_server_session).
-behaviour(gen_server).
-export([start_link/1]).
-export([init/1, handle_call/3, handle_cast/2, handle_info/2,
terminate/2, code_change/3]).
-include("masque.hrl").
-include("masque_udp_bind.hrl").
-record(state, {
transport :: h2 | h3,
conn :: pid(),
stream_id :: non_neg_integer(),
router :: pid() | undefined,
handler :: module(),
h_state :: term(),
req :: map(),
%% Bind classification + advertised public address list.
bind_scope :: scoped | unscoped,
public_addresses :: [{inet:ip_address(), inet:port_number()}],
%% Per-session compression tables.
own_table :: masque_compression_table:state(),
peer_table :: masque_compression_table:state(),
cap_buf = <<>> :: binary(),
max_cap :: pos_integer(),
cap_fin_seen = false :: boolean(),
%% Actions returned by handler init, applied after response
%% headers have been emitted.
pending_actions :: [term()] | undefined,
start_time :: integer() | undefined
}).
-define(PROXY_ROLE, proxy).
%%====================================================================
%% API
%%====================================================================
-spec start_link(map()) -> {ok, pid()} | ignore | {error, term()}.
start_link(Args) ->
gen_server:start_link(?MODULE, Args, []).
%%====================================================================
%% gen_server
%%====================================================================
init(#{conn := Conn, stream_id := StreamId, transport := Transport,
router := Router,
handler := Handler, handler_opts := HOpts, req := Req}) ->
process_flag(trap_exit, true),
erlang:monitor(process, Router),
MaxCap = maps:get(max_capsule_size, HOpts,
?MASQUE_DEFAULT_MAX_CAPSULE_SIZE),
BindScope = maps:get(bind, Req, unscoped),
case init_handler(Handler, Req, HOpts) of
{ok, HState, Actions} ->
{Headers, OtherActions} = take_response_headers(Actions),
PublicAddrs = read_public_addresses(Headers),
Families = lists:usort([family_of(IP)
|| {IP, _P} <- PublicAddrs]),
TableOpts = #{advertised_families => Families,
max_entries =>
maps:get(max_compression_contexts, HOpts,
1024)},
State = #state{
transport = Transport,
conn = Conn,
stream_id = StreamId,
router = Router,
handler = Handler,
h_state = HState,
req = Req,
bind_scope = BindScope,
public_addresses = PublicAddrs,
own_table = masque_compression_table:new_own(?PROXY_ROLE,
TableOpts),
peer_table = masque_compression_table:new_peer(?PROXY_ROLE,
TableOpts),
max_cap = MaxCap,
pending_actions = OtherActions
},
{ok, {State, Headers}};
{stop, Reason} ->
{stop, Reason}
end.
handle_call(finalize, _From,
{#state{pending_actions = Actions} = State, Headers})
when Actions =/= undefined ->
case send_response(State, 200, base_response_headers() ++ Headers) of
ok ->
case claim_stream(State#state{pending_actions = undefined}) of
{ok, S2} ->
masque_metrics:tunnel_opened(
#{protocol => udp_bind,
transport => State#state.transport}),
{reply, ok,
run_init_actions(Actions,
S2#state{start_time =
erlang:monotonic_time(millisecond)})};
{error, _} = Err ->
{reply, Err, State}
end;
{error, _} = Err ->
{reply, Err, State}
end;
handle_call(_Req, _From, S) ->
{reply, {error, unknown_call}, S}.
handle_cast(connection_closed, S) ->
{stop, connection_closed, S};
handle_cast(_Msg, S) ->
{noreply, S}.
handle_info({masque_datagram_in, StreamId, Payload},
#state{transport = h3, stream_id = StreamId} = S) ->
masque_metrics:bytes_in(byte_size(Payload),
#{protocol => udp_bind, transport => h3}),
handle_inbound_datagram(Payload, S);
handle_info({masque_stream_data, StreamId, Data, Fin},
#state{stream_id = StreamId} = S) ->
handle_stream_bytes(Data, Fin, S);
handle_info({quic_h3, _Conn, {data, StreamId, Data, Fin}},
#state{transport = h3, stream_id = StreamId} = S) ->
handle_stream_bytes(Data, Fin, S);
handle_info({masque_stream_reset, StreamId, _ErrorCode},
#state{stream_id = StreamId} = S) ->
{stop, peer_reset, S};
handle_info({'DOWN', _MRef, process, _Pid, _Reason}, S) ->
{stop, router_gone, S};
handle_info(Msg, S) ->
%% Hand all other messages (notably {udp, ...} from the bind
%% handler's gen_udp socket) through the handler's handle_info/2.
dispatch(handle_info, [Msg], S).
terminate(Reason, #state{} = S) ->
emit_tunnel_closed(S),
terminate_transport(Reason, S),
_ = case S#state.router of
undefined -> ok;
R -> try masque_server_connection:unregister_session(
R, S#state.stream_id) catch _:_ -> ok end
end,
try_callback(S#state.handler, terminate,
[Reason, S#state.h_state]),
ok.
code_change(_OldVsn, S, _Extra) ->
{ok, S}.
emit_tunnel_closed(#state{start_time = undefined}) -> ok;
emit_tunnel_closed(#state{start_time = T, transport = Transport}) ->
Duration = erlang:monotonic_time(millisecond) - T,
masque_metrics:tunnel_closed(Duration,
#{protocol => udp_bind,
transport => Transport}).
%%====================================================================
%% Inbound datagram path
%%====================================================================
handle_inbound_datagram(Payload, #state{} = S) ->
case masque_datagram:decode(Payload) of
{ok, {0, Inner}} ->
handle_context_zero(Inner, S);
{ok, {Ctx, Inner}} when is_integer(Ctx), Ctx > 0 ->
handle_known_context(Ctx, Inner, S);
{error, _} ->
{noreply, S}
end.
%% Scoped bind: context-id 0 keeps RFC 9298 CONNECT-UDP semantics.
%% Unscoped bind: context-id 0 is reserved (drop).
handle_context_zero(Inner, #state{bind_scope = scoped} = S) ->
%% Treat as a raw UDP payload to the scoped peer. The scoped peer
%% lives in `req()' under target_host / target_port; for v1 we
%% defer to handle_packet/2 if exported (legacy UDP semantics).
dispatch(handle_packet, [Inner], S);
handle_context_zero(_Inner, S) ->
%% Unscoped: malformed; per draft-11 we drop. Counter bump goes
%% in a follow-up PR.
{noreply, S}.
handle_known_context(Ctx, Inner, #state{} = S) ->
case masque_compression_table:lookup_by_id(S#state.peer_table, Ctx) of
{ok, #compression_entry{ip_version = 0}} ->
handle_uncompressed_payload(Inner, S);
{ok, #compression_entry{ip_version = V,
address = A,
port = P}}
when V =:= 4; V =:= 6 ->
Peer = {A, P},
handle_bind_to_peer(Peer, Inner, S);
not_found ->
%% Unknown context ID. Per draft-11 sections 4 and 5
%% these arrive on a context the peer never installed:
%% drop. (Telemetry attribution lands in a follow-up.)
{noreply, S}
end.
handle_uncompressed_payload(Inner, S) ->
case masque_udp_bind_payload:decode_uncompressed(Inner) of
{ok, {_V, IP, Port}, UdpPayload} ->
handle_bind_to_peer({IP, Port}, UdpPayload, S);
{error, _} ->
{noreply, S}
end.
handle_bind_to_peer(Peer, UdpPayload, #state{handler = Handler,
h_state = HS} = S) ->
case erlang:function_exported(Handler, handle_bind_packet, 3) of
true ->
case Handler:handle_bind_packet(Peer, UdpPayload, HS) of
{ok, HS2} ->
{noreply, S#state{h_state = HS2}};
{ok, HS2, Actions} ->
apply_actions_noreply(Actions,
S#state{h_state = HS2});
{drop, _Reason, HS2} ->
{noreply, S#state{h_state = HS2}};
{stop, R, HS2} ->
{stop, R, S#state{h_state = HS2}}
end;
false ->
{noreply, S}
end.
%%====================================================================
%% Capsule path
%%====================================================================
handle_stream_bytes(Data, Fin,
#state{cap_buf = Buf, max_cap = Max} = S) ->
New = <<Buf/binary, Data/binary>>,
case byte_size(New) > Max of
true ->
reset_and_stop(capsule_buffer_overflow, S);
false ->
drain_capsules(New, Fin, S#state{cap_fin_seen = Fin})
end.
drain_capsules(Buf, Fin, S) ->
case masque_capsule:decode(Buf) of
{ok, {Type, Value, Rest}} ->
case dispatch_capsule(Type, Value, S) of
{noreply, S2} ->
drain_capsules(Rest, Fin, S2#state{cap_buf = <<>>});
Stop ->
Stop
end;
{more, _} when Fin, Buf =/= <<>> ->
reset_and_stop(truncated_capsule, S);
{more, _} ->
{noreply, S#state{cap_buf = Buf}};
{error, _Reason} ->
reset_and_stop(malformed_capsule, S)
end.
dispatch_capsule(?MASQUE_CAPSULE_COMPRESSION_ASSIGN, Body, S) ->
case masque_compression_capsule:decode_assign(Body) of
{ok, Assign} ->
handle_peer_assign(Assign, S);
{error, _} ->
reset_and_stop(malformed_capsule, S)
end;
dispatch_capsule(?MASQUE_CAPSULE_COMPRESSION_ACK, Body, S) ->
case masque_compression_capsule:decode_ack(Body) of
{ok, Ack} -> handle_peer_ack(Ack, S);
{error, _} -> reset_and_stop(malformed_capsule, S)
end;
dispatch_capsule(?MASQUE_CAPSULE_COMPRESSION_CLOSE, Body, S) ->
case masque_compression_capsule:decode_close(Body) of
{ok, Close} -> handle_peer_close(Close, S);
{error, _} -> reset_and_stop(malformed_capsule, S)
end;
dispatch_capsule(Type, Value, S) ->
%% Unknown capsule: defer to handler's handle_capsule/3, otherwise
%% silently drop per RFC 9297.
dispatch(handle_capsule, [Type, Value], S).
handle_peer_assign(Assign, S) ->
case masque_compression_table:install(S#state.peer_table, Assign) of
{ok, T2} ->
ack_peer_assign(Assign#compression_assign.context_id,
S#state{peer_table = T2});
{error, _} ->
reset_and_stop(malformed_capsule, S)
end.
ack_peer_assign(Id, S) ->
Bytes = iolist_to_binary(
masque_compression_capsule:encode(
#compression_ack{context_id = Id})),
send_capsule_bytes(Bytes, S).
handle_peer_ack(Ack, S) ->
case masque_compression_table:install_ack(S#state.own_table, Ack) of
{ok, T2} ->
{noreply, S#state{own_table = T2}};
{error, _} ->
reset_and_stop(malformed_capsule, S)
end.
handle_peer_close(Close, #state{own_table = OT, peer_table = PT} = S) ->
%% A close can refer to a context owned by either side. Try the
%% own table first; fall through to the peer table.
case masque_compression_table:install_close(OT, Close) of
{ok, OT2} ->
{noreply, S#state{own_table = OT2}};
{error, unknown_context} ->
case masque_compression_table:install_close(PT, Close) of
{ok, PT2} -> {noreply, S#state{peer_table = PT2}};
{error, _} -> reset_and_stop(malformed_capsule, S)
end
end.
%%====================================================================
%% Action interpreter
%%====================================================================
apply_actions_noreply(Actions, State) ->
case do_actions(Actions, State) of
{ok, S2} -> {noreply, S2};
{stop, Reason, S2} -> {stop, Reason, S2}
end.
run_init_actions([], S) -> S;
run_init_actions(Actions, S) ->
case do_actions(Actions, S) of
{ok, S2} -> S2;
{stop, Reason, _} -> exit(Reason)
end.
do_actions([], S) -> {ok, S};
do_actions([{send_bind_packet, Peer, Bytes} | Rest], S) ->
do_actions(Rest, send_bind_payload(Peer, Bytes, S));
do_actions([{compression_assign, Entry} | Rest], S) ->
do_actions(Rest, send_compression_assign(Entry, S));
do_actions([{compression_ack, Id} | Rest], S) ->
Bytes = masque_compression_capsule:encode(
#compression_ack{context_id = Id}),
do_actions(Rest, send_capsule_bytes_or_state(Bytes, S));
do_actions([{compression_close, Id} | Rest], S) ->
Bytes = masque_compression_capsule:encode(
#compression_close{context_id = Id}),
do_actions(Rest, send_capsule_bytes_or_state(Bytes, S));
do_actions([{send_capsule, Type, Value} | Rest], S) ->
Enc = masque_capsule:encode(Type, Value),
do_actions(Rest, send_capsule_bytes_or_state(Enc, S));
do_actions([close_session | _Rest], S) ->
{stop, normal, S};
do_actions([{close_session, _Code, _Msg} | _Rest], S) ->
{stop, normal, S};
do_actions([_Unknown | Rest], S) ->
do_actions(Rest, S).
%% Ignore the response_headers action if it leaks past init - those
%% have already been spliced into the 2xx and reapplying them is a
%% no-op on the wire.
%% (Handled implicitly by the fall-through clause above.)
%%====================================================================
%% Outbound datagram + capsule emit
%%====================================================================
send_bind_payload({IP, Port}, UdpPayload, S) ->
Tuple = {family_of(IP), IP, Port},
case masque_compression_table:lookup_by_tuple(S#state.own_table,
Tuple) of
{ok, #compression_entry{state = installed,
ip_version = 0}} ->
%% The own-table uncompressed mapping is open and ACKed:
%% emit the payload on its context-id, with the inner
%% peer tuple.
send_uncompressed(Tuple, UdpPayload, S);
{ok, #compression_entry{state = installed, context_id = Id,
ip_version = V}} when V =:= 4; V =:= 6 ->
send_compressed(Id, UdpPayload, S);
_ ->
%% No mapping yet (or not yet ACKed). Try the
%% uncompressed channel if the peer opened one for us;
%% otherwise drop.
try_uncompressed_fallback(Tuple, UdpPayload, S)
end.
try_uncompressed_fallback(Tuple, UdpPayload, S) ->
case find_peer_uncompressed(S#state.peer_table) of
{ok, Id} ->
case masque_udp_bind_payload:encode_uncompressed(
Tuple, UdpPayload, advertised_families(S)) of
{ok, Inner} ->
send_datagram(Id, Inner, S);
{error, _} -> S
end;
not_found ->
S
end.
find_peer_uncompressed(Table) ->
case [Entry || Entry <- masque_compression_table:entries(Table),
Entry#compression_entry.ip_version =:= 0] of
[#compression_entry{context_id = Id} | _] -> {ok, Id};
[] -> not_found
end.
send_uncompressed(Tuple, UdpPayload, S) ->
case find_own_uncompressed(S#state.own_table) of
{ok, Id} ->
case masque_udp_bind_payload:encode_uncompressed(
Tuple, UdpPayload, advertised_families(S)) of
{ok, Inner} -> send_datagram(Id, Inner, S);
{error, _} -> S
end;
not_found -> S
end.
find_own_uncompressed(Table) ->
case [Entry || Entry <- masque_compression_table:entries(Table),
Entry#compression_entry.ip_version =:= 0,
Entry#compression_entry.state =:= installed] of
[#compression_entry{context_id = Id} | _] -> {ok, Id};
[] -> not_found
end.
send_compressed(Id, UdpPayload, S) ->
Inner = masque_udp_bind_payload:encode_compressed(UdpPayload),
send_datagram(Id, Inner, S).
send_datagram(Ctx, Inner, #state{transport = h3, conn = C,
stream_id = Sid} = S) ->
Enc = masque_datagram:encode(Ctx, Inner),
_ = quic_h3:send_datagram(C, Sid, Enc),
masque_metrics:bytes_out(iolist_size(Inner),
#{protocol => udp_bind, transport => h3}),
S;
send_datagram(Ctx, Inner, #state{transport = h2} = S) ->
%% h2 carries datagrams as RFC 9297 DATAGRAM-type capsules.
%% h2_capsule:encode/2 builds the type+length frame for the
%% `datagram' atom internally (matches the existing UDP / IP
%% session pattern).
Inner1 = iolist_to_binary(masque_datagram:encode(Ctx, Inner)),
Cap = h2_capsule:encode(datagram, Inner1),
{noreply, S2} = send_capsule_bytes(Cap, S),
S2.
send_compression_assign(Entry, S) ->
Bytes = masque_compression_capsule:encode(
#compression_assign{
context_id = Entry#compression_entry.context_id,
ip_version = Entry#compression_entry.ip_version,
address = Entry#compression_entry.address,
port = Entry#compression_entry.port}),
send_capsule_bytes_or_state(Bytes, S).
send_capsule_bytes_or_state(Bytes, S) ->
{noreply, S2} = send_capsule_bytes(iolist_to_binary(Bytes), S),
S2.
send_capsule_bytes(Bytes, #state{transport = h3, conn = C,
stream_id = Sid} = S) ->
_ = quic_h3:send_data(C, Sid, Bytes, false),
masque_metrics:bytes_out(byte_size(Bytes),
#{protocol => udp_bind, transport => h3}),
{noreply, S};
send_capsule_bytes(Bytes, #state{transport = h2, conn = C,
stream_id = Sid} = S) ->
_ = h2:send_data(C, Sid, Bytes),
masque_metrics:bytes_out(byte_size(Bytes),
#{protocol => udp_bind, transport => h2}),
{noreply, S}.
%%====================================================================
%% Transport-specific glue
%%====================================================================
send_response(#state{transport = h3, conn = C, stream_id = S}, Status, Hdrs) ->
quic_h3:send_response(C, S, Status, Hdrs);
send_response(#state{transport = h2, conn = C, stream_id = S}, Status, Hdrs) ->
h2:send_response(C, S, Status, Hdrs).
claim_stream(#state{transport = h3, conn = C, stream_id = Sid,
cap_buf = Buf} = S) ->
case quic_h3:set_stream_handler(C, Sid, self()) of
ok ->
{ok, S};
{ok, Chunks} ->
More = iolist_to_binary([D || {D, _Fin} <- Chunks]),
{ok, S#state{cap_buf = <<Buf/binary, More/binary>>}};
{error, _} = Err ->
Err
end;
claim_stream(#state{transport = h2} = S) ->
{ok, S}.
reset_and_stop(Reason, #state{transport = h3, conn = C,
stream_id = Sid} = S) ->
_ = (try quic_h3:cancel(C, Sid, ?MASQUE_H3_MESSAGE_ERROR) catch _:_ -> ok end),
{stop, Reason, S};
reset_and_stop(Reason, #state{transport = h2, conn = C,
stream_id = Sid} = S) ->
_ = (try h2:cancel(C, Sid, protocol_error) catch _:_ -> ok end),
{stop, Reason, S}.
terminate_transport(normal, #state{transport = h3, conn = C,
stream_id = Sid}) ->
_ = (try quic_h3:send_data(C, Sid, <<>>, true) catch _:_ -> ok end),
ok;
terminate_transport(_Reason, _S) ->
ok.
%%====================================================================
%% Handler / opts plumbing
%%====================================================================
init_handler(Handler, Req, HOpts) ->
case erlang:function_exported(Handler, init, 2) of
true ->
case Handler:init(Req, HOpts) of
{ok, HState} -> {ok, HState, []};
{ok, HState, Actions} -> {ok, HState, Actions};
{stop, Reason} -> {stop, Reason};
Other -> {stop, {bad_init, Other}}
end;
false ->
{ok, undefined, []}
end.
dispatch(CB, Extra, #state{handler = Handler, h_state = HS} = S) ->
case erlang:function_exported(Handler, CB, length(Extra) + 1) of
true ->
case apply(Handler, CB, Extra ++ [HS]) of
{ok, HS2} -> {noreply, S#state{h_state = HS2}};
{ok, HS2, Actions} -> apply_actions_noreply(
Actions, S#state{h_state = HS2});
{stop, R, HS2} -> {stop, R, S#state{h_state = HS2}};
_ -> {noreply, S}
end;
false ->
{noreply, S}
end.
try_callback(Mod, Fun, Args) ->
Arity = length(Args),
case erlang:function_exported(Mod, Fun, Arity) of
true -> (try apply(Mod, Fun, Args) catch _:_ -> ok end);
false -> ok
end.
%%====================================================================
%% Helpers
%%====================================================================
base_response_headers() ->
[{<<"capsule-protocol">>, <<"?1">>}].
%% Pull the {response_headers, _} action out of the init action list
%% so the session can splice it into the 2xx; everything else stays
%% to be applied after the response.
take_response_headers(Actions) ->
take_response_headers(Actions, [], []).
take_response_headers([], Hdrs, Other) ->
{lists:reverse(Hdrs), lists:reverse(Other)};
take_response_headers([{response_headers, Pairs} | Rest], Hdrs, Other) ->
take_response_headers(Rest, lists:reverse(Pairs) ++ Hdrs, Other);
take_response_headers([X | Rest], Hdrs, Other) ->
take_response_headers(Rest, Hdrs, [X | Other]).
read_public_addresses(Headers) ->
case masque_uri_udp_bind:parse_proxy_public_address(Headers) of
{ok, Addrs} -> Addrs;
{error, _} -> []
end.
advertised_families(#state{public_addresses = Addrs}) ->
lists:usort([family_of(IP) || {IP, _} <- Addrs]).
family_of({_,_,_,_}) -> 4;
family_of({_,_,_,_,_,_,_,_}) -> 6.