%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 2010-2011. All Rights Reserved.
%%
%% The contents of this file are subject to the Erlang Public License,
%% Version 1.1, (the "License"); you may not use this file except in
%% compliance with the License. You should have received a copy of the
%% Erlang Public License along with this software. If not, it can be
%% retrieved online at http://www.erlang.org/.
%%
%% Software distributed under the License is distributed on an "AS IS"
%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
%% the License for the specific language governing rights and limitations
%% under the License.
%%
%% %CopyrightEnd%
%%
-module(diameter_tcp).
-behaviour(gen_server).
%% interface
-export([start/3]).
%% child start from supervisor
-export([start_link/1]).
%% child start from here
-export([init/1]).
%% gen_server callbacks
-export([handle_call/3,
handle_cast/2,
handle_info/2,
code_change/3,
terminate/2]).
-include_lib("diameter/include/diameter.hrl").
-define(ERROR(T), erlang:error({T, ?MODULE, ?LINE})).
-define(DEFAULT_PORT, 3868). %% RFC 3588, ch 2.1
-define(LISTENER_TIMEOUT, 30000).
-define(FRAGMENT_TIMEOUT, 1000).
%% The same gen_server implementation supports three different kinds
%% of processes: an actual transport process, one that will club it to
%% death should the parent die before a connection is established, and
%% a process owning the listening port.
%% Listener process state.
-record(listener, {socket :: inet:socket(),
count = 1 :: non_neg_integer(),
tref :: reference()}).
%% Monitor process state.
-record(monitor,
{parent :: pid(),
transport = self() :: pid()}).
-type tref() :: reference(). %% timer reference
-type length() :: 0..16#FFFFFF. %% message length from Diameter header
-type size() :: non_neg_integer(). %% accumulated binary size
-type frag() :: {length(), size(), binary(), list(binary())}
| binary().
%% Accepting/connecting transport process state.
-record(transport,
{socket :: inet:socket(), %% accept or connect socket
parent :: pid(), %% of process that started us
module :: module(), %% gen_tcp-like module
frag = <<>> :: binary() | {tref(), frag()}}). %% message fragment
%% The usual transport using gen_tcp can be replaced by anything
%% sufficiently gen_tcp-like by passing a 'module' option as the first
%% (for simplicity) transport option. The transport_module diameter_etcp
%% uses this to set itself as the module to call, its start/3 just
%% calling start/3 here with the option set.
%% ---------------------------------------------------------------------------
%% # start/3
%% ---------------------------------------------------------------------------
start({T, Ref}, #diameter_service{capabilities = Caps}, Opts) ->
diameter_tcp_sup:start(), %% start tcp supervisors on demand
{Mod, Rest} = split(Opts),
Addrs = Caps#diameter_caps.host_ip_address,
Arg = {T, Ref, Mod, self(), Rest, Addrs},
diameter_tcp_sup:start_child(Arg).
split([{module, M} | Opts]) ->
{M, Opts};
split(Opts) ->
{gen_tcp, Opts}.
%% start_link/1
start_link(T) ->
proc_lib:start_link(?MODULE,
init,
[T],
infinity,
diameter_lib:spawn_opts(server, [])).
%% ---------------------------------------------------------------------------
%% # init/1
%% ---------------------------------------------------------------------------
init(T) ->
gen_server:enter_loop(?MODULE, [], i(T)).
%% i/1
%% A transport process.
i({T, Ref, Mod, Pid, Opts, Addrs})
when T == accept;
T == connect ->
erlang:monitor(process, Pid),
%% Since accept/connect might block indefinitely, spawn a process
%% that does nothing but kill us with the parent until call
%% returns.
{ok, MPid} = diameter_tcp_sup:start_child(#monitor{parent = Pid}),
Sock = i(T, Ref, Mod, Pid, Opts, Addrs),
MPid ! {stop, self()}, %% tell the monitor to die
setopts(Mod, Sock),
#transport{parent = Pid,
module = Mod,
socket = Sock};
%% A monitor process to kill the transport if the parent dies.
i(#monitor{parent = Pid, transport = TPid} = S) ->
proc_lib:init_ack({ok, self()}),
erlang:monitor(process, Pid),
erlang:monitor(process, TPid),
S;
%% In principle a link between the transport and killer processes
%% could do the same thing: have the accepting/connecting process be
%% killed when the killer process dies as a consequence of parent
%% death. However, a link can be unlinked and this is exactly what
%% gen_tcp seems to so. Links should be left to supervisors.
i({listen, LRef, APid, {Mod, Opts, Addrs}}) ->
{[LA, LP], Rest} = proplists:split(Opts, [ip, port]),
LAddr = get_addr(LA, Addrs),
LPort = get_port(LP),
{ok, LSock} = Mod:listen(LPort, gen_opts(LAddr, Rest)),
proc_lib:init_ack({ok, self(), {LAddr, LSock}}),
erlang:monitor(process, APid),
true = diameter_reg:add_new({?MODULE, listener, {LRef, {LAddr, LSock}}}),
start_timer(#listener{socket = LSock}).
%% i/6
i(accept, Ref, Mod, Pid, Opts, Addrs) ->
{LAddr, LSock} = listener(Ref, {Mod, Opts, Addrs}),
proc_lib:init_ack({ok, self(), [LAddr]}),
Sock = ok(accept(Mod, LSock)),
diameter_peer:up(Pid),
Sock;
i(connect, _, Mod, Pid, Opts, Addrs) ->
{[LA, RA, RP], Rest} = proplists:split(Opts, [ip, raddr, rport]),
LAddr = get_addr(LA, Addrs),
RAddr = get_addr(RA, []),
RPort = get_port(RP),
proc_lib:init_ack({ok, self(), [LAddr]}),
Sock = ok(connect(Mod, RAddr, RPort, gen_opts(LAddr, Rest))),
diameter_peer:up(Pid, {RAddr, RPort}),
Sock.
ok({ok, T}) ->
T;
ok(No) ->
x(No).
x(Reason) ->
exit({shutdown, Reason}).
%% listener/2
listener(LRef, T) ->
l(diameter_reg:match({?MODULE, listener, {LRef, '_'}}), LRef, T).
%% Existing process with the listening socket ...
l([{{?MODULE, listener, {_, AS}}, LPid}], _, _) ->
LPid ! {accept, self()},
AS;
%% ... or not: start one.
l([], LRef, T) ->
{ok, _, AS} = diameter_tcp_sup:start_child({listen, LRef, self(), T}),
AS.
%% get_addr/2
get_addr(As, Def) ->
diameter_lib:ipaddr(addr(As, Def)).
%% Take the first address from the service if several are unspecified.
addr([], [Addr | _]) ->
Addr;
addr([{_, Addr}], _) ->
Addr;
addr(As, Addrs) ->
?ERROR({invalid_addrs, As, Addrs}).
%% get_port/1
get_port([{_, Port}]) ->
Port;
get_port([]) ->
?DEFAULT_PORT;
get_port(Ps) ->
?ERROR({invalid_ports, Ps}).
%% gen_opts/2
gen_opts(LAddr, Opts) ->
{L,_} = proplists:split(Opts, [binary, packet, active]),
[[],[],[]] == L orelse ?ERROR({reserved_options, Opts}),
[binary,
{packet, 0},
{active, once},
{ip, LAddr}
| Opts].
%% ---------------------------------------------------------------------------
%% # handle_call/3
%% ---------------------------------------------------------------------------
handle_call(_, _, State) ->
{reply, nok, State}.
%% ---------------------------------------------------------------------------
%% # handle_cast/2
%% ---------------------------------------------------------------------------
handle_cast(_, State) ->
{noreply, State}.
%% ---------------------------------------------------------------------------
%% # handle_info/2
%% ---------------------------------------------------------------------------
handle_info(T, #transport{} = S) ->
{noreply, #transport{} = t(T,S)};
handle_info(T, #listener{} = S) ->
{noreply, #listener{} = l(T,S)};
handle_info(T, #monitor{} = S) ->
m(T,S),
x(T).
%% ---------------------------------------------------------------------------
%% # code_change/3
%% ---------------------------------------------------------------------------
code_change(_, State, _) ->
{ok, State}.
%% ---------------------------------------------------------------------------
%% # terminate/2
%% ---------------------------------------------------------------------------
terminate(_, _) ->
ok.
%% ---------------------------------------------------------------------------
%% start_timer/1
start_timer(#listener{count = 0} = S) ->
S#listener{tref = erlang:start_timer(?LISTENER_TIMEOUT, self(), close)};
start_timer(S) ->
S.
%% m/2
%%
%% Transition monitor state.
%% Transport is telling us to die.
m({stop, TPid}, #monitor{transport = TPid}) ->
ok;
%% Transport has died.
m({'DOWN', _, process, TPid, _}, #monitor{transport = TPid}) ->
ok;
%% Transport parent has died.
m({'DOWN', _, process, Pid, _}, #monitor{parent = Pid,
transport = TPid}) ->
exit(TPid, {shutdown, parent}).
%% l/2
%%
%% Transition listener state.
%% Another accept transport is attaching.
l({accept, TPid}, #listener{count = N} = S) ->
erlang:monitor(process, TPid),
S#listener{count = N+1};
%% Accepting process has died.
l({'DOWN', _, process, _, _}, #listener{count = N} = S) ->
start_timer(S#listener{count = N-1});
%% Timeout after the last accepting process has died.
l({timeout, TRef, close = T}, #listener{tref = TRef,
count = 0}) ->
x(T);
l({timeout, _, close}, #listener{} = S) ->
S.
%% t/2
%%
%% Transition transport state.
t(T,S) ->
case transition(T,S) of
ok ->
S;
#transport{} = NS ->
NS;
{stop, Reason} ->
x(Reason);
stop ->
x(T)
end.
%% transition/2
%% Incoming message.
transition({tcp, Sock, Data}, #transport{socket = Sock,
module = M}
= S) ->
setopts(M, Sock),
recv(Data, S);
transition({tcp_closed, Sock}, #transport{socket = Sock}) ->
stop;
transition({tcp_error, Sock, _Reason} = T, #transport{socket = Sock} = S) ->
?ERROR({T,S});
%% Outgoing message.
transition({diameter, {send, Bin}}, #transport{socket = Sock,
module = M}) ->
case send(M, Sock, Bin) of
ok ->
ok;
{error, Reason} ->
{stop, {send, Reason}}
end;
%% Request to close the transport connection.
transition({diameter, {close, Pid}}, #transport{parent = Pid,
socket = Sock,
module = M}) ->
M:close(Sock),
stop;
%% Timeout for reception of outstanding packets.
transition({timeout, TRef, flush}, S) ->
flush(TRef, S);
%% Request for the local port number.
transition({resolve_port, RPid}, #transport{socket = Sock,
module = M})
when is_pid(RPid) ->
RPid ! lport(M, Sock),
ok;
%% Parent process has died.
transition({'DOWN', _, process, Pid, _}, #transport{parent = Pid}) ->
stop.
%% Crash on anything unexpected.
%% recv/2
%%
%% Reassemble fragmented messages and extract multple message sent
%% using Nagle.
recv(Bin, #transport{parent = Pid, frag = Head} = S) ->
S#transport{frag = recv(Pid, Head, Bin)}.
%% recv/3
%% No previous fragment.
recv(Pid, <<>>, Bin) ->
rcv(Pid, Bin);
recv(Pid, {TRef, Head}, Bin) ->
erlang:cancel_timer(TRef),
rcv(Pid, Head, Bin).
%% rcv/3
%% Not even the first four bytes of the header.
rcv(Pid, Head, Bin)
when is_binary(Head) ->
rcv(Pid, <<Head/binary, Bin/binary>>);
%% Or enough to know how many bytes to extract.
rcv(Pid, {Len, N, Head, Acc}, Bin) ->
rcv(Pid, Len, N + size(Bin), Head, [Bin | Acc]).
%% rcv/5
%% Extract a message for which we have all bytes.
rcv(Pid, Len, N, Head, Acc)
when Len =< N ->
rcv(Pid, rcv1(Pid, Len, bin(Head, Acc)));
%% Wait for more packets.
rcv(_, Len, N, Head, Acc) ->
{start_timer(), {Len, N, Head, Acc}}.
%% rcv/2
%% Nothing left.
rcv(_, <<>> = Bin) ->
Bin;
%% Well, this isn't good. Chances are things will go south from here
%% but if we're lucky then the bytes we have extend to an intended
%% message boundary and we can recover by simply discarding them,
%% which is the result of receiving them.
rcv(Pid, <<_:1/binary, Len:24, _/binary>> = Bin)
when Len < 20 ->
diameter_peer:recv(Pid, Bin),
<<>>;
%% Enough bytes to extract a message.
rcv(Pid, <<_:1/binary, Len:24, _/binary>> = Bin)
when Len =< size(Bin) ->
rcv(Pid, rcv1(Pid, Len, Bin));
%% Or not: wait for more packets.
rcv(_, <<_:1/binary, Len:24, _/binary>> = Head) ->
{start_timer(), {Len, size(Head), Head, []}};
%% Not even 4 bytes yet.
rcv(_, Head) ->
{start_timer(), Head}.
%% rcv1/3
rcv1(Pid, Len, Bin) ->
<<Msg:Len/binary, Rest/binary>> = Bin,
diameter_peer:recv(Pid, Msg),
Rest.
%% bin/[12]
bin(Head, Acc) ->
list_to_binary([Head | lists:reverse(Acc)]).
bin({_, _, Head, Acc}) ->
bin(Head, Acc);
bin(Bin)
when is_binary(Bin) ->
Bin.
%% start_timer/0
%% An erroneously large message length may leave us with a fragment
%% that lingers if the peer doesn't have anything more to send. Start
%% a timer to force reception if an incoming message doesn't arrive
%% first. This won't stop a peer from sending a large bogus value and
%% following it up however but such a state of affairs can only go on
%% for so long since an unanswered DWR will eventually be the result.
%%
%% An erroneously small message length causes problems as well but
%% since all messages with length problems are discarded this should
%% also eventually lead to watchdog failover.
start_timer() ->
erlang:start_timer(?FRAGMENT_TIMEOUT, self(), flush).
flush(TRef, #transport{parent = Pid, frag = {TRef, Head}} = S) ->
diameter_peer:recv(Pid, bin(Head)),
S#transport{frag = <<>>};
flush(_, S) ->
S.
%% accept/2
accept(gen_tcp, LSock) ->
gen_tcp:accept(LSock);
accept(Mod, LSock) ->
Mod:accept(LSock).
%% connect/4
connect(gen_tcp, Host, Port, Opts) ->
gen_tcp:connect(Host, Port, Opts);
connect(Mod, Host, Port, Opts) ->
Mod:connect(Host, Port, Opts).
%% send/3
send(gen_tcp, Sock, Bin) ->
gen_tcp:send(Sock, Bin);
send(M, Sock, Bin) ->
M:send(Sock, Bin).
%% setopts/3
setopts(gen_tcp, Sock, Opts) ->
inet:setopts(Sock, Opts);
setopts(M, Sock, Opts) ->
M:setopts(Sock, Opts).
%% setopts/2
setopts(M, Sock) ->
case setopts(M, Sock, [{active, once}]) of
ok -> ok;
X -> x({setopts, M, Sock, X}) %% possibly on peer disconnect
end.
%% lport/2
lport(gen_tcp, Sock) ->
inet:port(Sock);
lport(M, Sock) ->
M:port(Sock).
