%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 2013. 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%
%%
%%
%% Implements the handling of incoming and outgoing Diameter messages
%% except CER/CEA, DWR/DWA and DPR/DPA. That is, the messages that a
%% diameter client sends of receives.
%%
-module(diameter_traffic).
%% towards diameter
-export([send_request/4]).
%% towards diameter_watchdog
-export([receive_message/4]).
%% towards diameter_service
-export([make_recvdata/1,
peer_up/1,
peer_down/1,
failover/1,
pending/1]).
%% Other callbacks.
-export([send/1]). %% send from remote node
-include_lib("diameter/include/diameter.hrl").
-include("diameter_internal.hrl").
-define(RELAY, ?DIAMETER_DICT_RELAY).
-define(BASE, ?DIAMETER_DICT_COMMON). %% Note: the RFC 3588 dictionary
-define(DEFAULT_TIMEOUT, 5000). %% for outgoing requests
%% Table containing outgoing requests for which a reply has yet to be
%% received.
-define(REQUEST_TABLE, diameter_request).
%% Workaround for dialyzer's lack of understanding of match specs.
-type match(T)
:: T | '_' | '$1' | '$2' | '$3' | '$4'.
%% Record diameter:call/4 options are parsed into.
-record(options,
{filter = none :: diameter:peer_filter(),
extra = [] :: list(),
timeout = ?DEFAULT_TIMEOUT :: 0..16#FFFFFFFF,
detach = false :: boolean()}).
%% Term passed back to receive_message/4 with every incoming message.
-record(recvdata,
{peerT :: ets:tid(),
service_name :: diameter:service_name(),
apps :: [#diameter_app{}],
sequence :: diameter:sequence()}).
%% Record stored in diameter_request for each outgoing request.
-record(request,
{ref :: match(reference()), %% used to receive answer
caller :: match(pid()), %% calling process
handler :: match(pid()), %% request process
transport :: match(pid()), %% peer process
caps :: match(#diameter_caps{}), %% of connection
packet :: match(#diameter_packet{})}). %% of request
%% ---------------------------------------------------------------------------
%% # make_recvdata/1
%% ---------------------------------------------------------------------------
make_recvdata([SvcName, PeerT, Apps, Mask | _]) ->
#recvdata{service_name = SvcName,
peerT = PeerT,
apps = Apps,
sequence = Mask}.
%% Take a list so that the caller (diameter_service) can be upgraded
%% first if new members are added. Note that receive_message/4 might
%% still get an old term from any watchdog started in old code.
%% ---------------------------------------------------------------------------
%% peer_up/1
%% ---------------------------------------------------------------------------
%% Insert an element that is used to detect whether or not there has
%% been a failover when inserting an outgoing request.
peer_up(TPid) ->
ets:insert(?REQUEST_TABLE, {TPid}).
%% ---------------------------------------------------------------------------
%% peer_down/1
%% ---------------------------------------------------------------------------
peer_down(TPid) ->
ets:delete(?REQUEST_TABLE, TPid),
failover(TPid).
%% ---------------------------------------------------------------------------
%% pending/1
%% ---------------------------------------------------------------------------
pending(TPids) ->
MatchSpec = [{{'$1',
#request{caller = '$2',
handler = '$3',
transport = '$4',
_ = '_'},
'_'},
[?ORCOND([{'==', T, '$4'} || T <- TPids])],
[{{'$1', [{{caller, '$2'}},
{{handler, '$3'}},
{{transport, '$4'}}]}}]}],
try
ets:select(?REQUEST_TABLE, MatchSpec)
catch
error: badarg -> [] %% service has gone down
end.
%% ---------------------------------------------------------------------------
%% # receive_message/4
%%
%% Handle an incoming Diameter message.
%% ---------------------------------------------------------------------------
%% Handle an incoming Diameter message in the watchdog process. This
%% used to come through the service process but this avoids that
%% becoming a bottleneck.
receive_message(TPid, Pkt, Dict0, RecvData)
when is_pid(TPid) ->
#diameter_packet{header = #diameter_header{is_request = R}} = Pkt,
recv(R,
(not R) andalso lookup_request(Pkt, TPid),
TPid,
Pkt,
Dict0,
RecvData).
%% Incoming request ...
recv(true, false, TPid, Pkt, Dict0, RecvData) ->
try
spawn(fun() -> recv_request(TPid, Pkt, Dict0, RecvData) end)
catch
error: system_limit = E -> %% discard
?LOG({error, E}, now())
end;
%% ... answer to known request ...
recv(false, #request{ref = Ref, handler = Pid} = Req, _, Pkt, Dict0, _) ->
Pid ! {answer, Ref, Req, Dict0, Pkt};
%% Note that failover could have happened prior to this message being
%% received and triggering failback. That is, both a failover message
%% and answer may be on their way to the handler process. In the worst
%% case the request process gets notification of the failover and
%% sends to the alternate peer before an answer arrives, so it's
%% always the case that we can receive more than one answer after
%% failover. The first answer received by the request process wins,
%% any others are discarded.
%% ... or not.
recv(false, false, _, _, _, _) ->
ok.
%% ---------------------------------------------------------------------------
%% recv_request/4
%% ---------------------------------------------------------------------------
recv_request(TPid,
#diameter_packet{header = #diameter_header{application_id = Id}}
= Pkt,
Dict0,
#recvdata{peerT = PeerT, apps = Apps}
= RecvData) ->
recv_request(diameter_service:find_incoming_app(PeerT, TPid, Id, Apps),
TPid,
Pkt,
Dict0,
RecvData).
%% recv_request/5
recv_request({#diameter_app{id = Id, dictionary = Dict} = App, Caps},
TPid,
Pkt,
Dict0,
RecvData) ->
recv_R(App,
TPid,
Caps,
Dict0,
RecvData,
diameter_codec:decode(Id, Dict, Pkt));
%% Note that the decode is different depending on whether or not Id is
%% ?APP_ID_RELAY.
%% DIAMETER_APPLICATION_UNSUPPORTED 3007
%% A request was sent for an application that is not supported.
recv_request(#diameter_caps{} = Caps, TPid, Pkt, Dict0, _) ->
As = collect_avps(Pkt),
protocol_error(3007, TPid, Caps, Dict0, Pkt#diameter_packet{avps = As});
recv_request(false, _, _, _, _) -> %% transport has gone down
ok.
collect_avps(Pkt) ->
case diameter_codec:collect_avps(Pkt) of
{_Bs, As} ->
As;
As ->
As
end.
%% recv_R/6
%% Wrong number of bits somewhere in the message: reply.
%%
%% DIAMETER_INVALID_AVP_BITS 3009
%% A request was received that included an AVP whose flag bits are
%% set to an unrecognized value, or that is inconsistent with the
%% AVP's definition.
%%
recv_R(_App,
TPid,
Caps,
Dict0,
_RecvData,
#diameter_packet{errors = [Bs | _]} = Pkt)
when is_bitstring(Bs) ->
protocol_error(3009, TPid, Caps, Dict0, Pkt);
%% Either we support this application but don't recognize the command
%% or we're a relay and the command isn't proxiable.
%%
%% DIAMETER_COMMAND_UNSUPPORTED 3001
%% The Request contained a Command-Code that the receiver did not
%% recognize or support. This MUST be used when a Diameter node
%% receives an experimental command that it does not understand.
%%
recv_R(#diameter_app{id = Id},
TPid,
Caps,
Dict0,
_RecvData,
#diameter_packet{header = #diameter_header{is_proxiable = P},
msg = M}
= Pkt)
when ?APP_ID_RELAY /= Id, undefined == M;
?APP_ID_RELAY == Id, not P ->
protocol_error(3001, TPid, Caps, Dict0, Pkt);
%% Error bit was set on a request.
%%
%% DIAMETER_INVALID_HDR_BITS 3008
%% A request was received whose bits in the Diameter header were
%% either set to an invalid combination, or to a value that is
%% inconsistent with the command code's definition.
%%
recv_R(_App,
TPid,
Caps,
Dict0,
_RecvData,
#diameter_packet{header = #diameter_header{is_error = true}}
= Pkt) ->
protocol_error(3008, TPid, Caps, Dict0, Pkt);
%% A message in a locally supported application or a proxiable message
%% in the relay application. Don't distinguish between the two since
%% each application has its own callback config. That is, the user can
%% easily distinguish between the two cases.
recv_R(App, TPid, Caps, Dict0, RecvData, Pkt) ->
request_cb(App, TPid, Caps, Dict0, RecvData, examine(Pkt)).
%% Note that there may still be errors but these aren't protocol
%% (3xxx) errors that lead to an answer-message.
request_cb(App,
TPid,
Caps,
Dict0,
#recvdata{service_name = SvcName}
= RecvData,
Pkt) ->
request_cb(cb(App, handle_request, [Pkt, SvcName, {TPid, Caps}]),
App,
TPid,
Caps,
Dict0,
RecvData,
[],
Pkt).
%% examine/1
%%
%% Look for errors in a decoded message. It's odd/unfortunate that
%% 501[15] aren't protocol errors.
%% DIAMETER_INVALID_MESSAGE_LENGTH 5015
%%
%% This error is returned when a request is received with an invalid
%% message length.
examine(#diameter_packet{header = #diameter_header{length = Len},
bin = Bin,
errors = Es}
= Pkt)
when Len < 20;
0 /= Len rem 4;
8*Len /= bit_size(Bin) ->
Pkt#diameter_packet{errors = [5015 | Es]};
%% DIAMETER_UNSUPPORTED_VERSION 5011
%% This error is returned when a request was received, whose version
%% number is unsupported.
examine(#diameter_packet{header = #diameter_header{version = V},
errors = Es}
= Pkt)
when V /= ?DIAMETER_VERSION ->
Pkt#diameter_packet{errors = [5011 | Es]};
examine(Pkt) ->
Pkt.
%% request_cb/8
%% A reply may be an answer-message, constructed either here or by
%% the handle_request callback. The header from the incoming request
%% is passed into the encode so that it can retrieve the relevant
%% command code in this case. It will also then ignore Dict and use
%% the base encoder.
request_cb({reply, Ans},
#diameter_app{dictionary = Dict},
TPid,
_Caps,
Dict0,
_RecvData,
Fs,
Pkt) ->
reply(Ans, dict(Dict, Dict0, Ans), TPid, Fs, Pkt);
%% An 3xxx result code, for which the E-bit is set in the header.
request_cb({protocol_error, RC},
_App,
TPid,
Caps,
Dict0,
_RecvData,
Fs,
Pkt)
when 3000 =< RC, RC < 4000 ->
protocol_error(RC, TPid, Caps, Dict0, Fs, Pkt);
%% RFC 3588 says we must reply 3001 to anything unrecognized or
%% unsupported. 'noreply' is undocumented (and inappropriately named)
%% backwards compatibility for this, protocol_error the documented
%% alternative.
request_cb(noreply,
_App,
TPid,
Caps,
Dict0,
_RecvData,
Fs,
Pkt) ->
protocol_error(3001, TPid, Caps, Dict0, Fs, Pkt);
%% Relay a request to another peer. This is equivalent to doing an
%% explicit call/4 with the message in question except that (1) a loop
%% will be detected by examining Route-Record AVP's, (3) a
%% Route-Record AVP will be added to the outgoing request and (3) the
%% End-to-End Identifier will default to that in the
%% #diameter_header{} without the need for an end_to_end_identifier
%% option.
%%
%% relay and proxy are similar in that they require the same handling
%% with respect to Route-Record and End-to-End identifier. The
%% difference is that a proxy advertises specific applications, while
%% a relay advertises the relay application. If a callback doesn't
%% want to distinguish between the cases in the callback return value
%% then 'resend' is a neutral alternative.
%%
request_cb({A, Opts},
#diameter_app{id = Id}
= App,
TPid,
Caps,
Dict0,
RecvData,
Fs,
Pkt)
when A == relay, Id == ?APP_ID_RELAY;
A == proxy, Id /= ?APP_ID_RELAY;
A == resend ->
resend(Opts, App, TPid, Caps, Dict0, RecvData, Fs, Pkt);
request_cb(discard, _, _, _, _, _, _, _) ->
ok;
request_cb({eval_packet, RC, F}, App, TPid, Caps, Dict0, RecvData, Fs, Pkt) ->
request_cb(RC, App, TPid, Caps, Dict0, RecvData, [F|Fs], Pkt);
request_cb({eval, RC, F}, App, TPid, Caps, Dict0, RecvData, Fs, Pkt) ->
request_cb(RC, App, TPid, Caps, Dict0, RecvData, Fs, Pkt),
diameter_lib:eval(F).
%% dict/3
%% An incoming answer, not yet decoded.
dict(Dict, Dict0, #diameter_packet{header
= #diameter_header{is_request = false,
is_error = E},
msg = undefined}) ->
if E -> Dict0; true -> Dict end;
dict(Dict, Dict0, [Msg]) ->
dict(Dict, Dict0, Msg);
dict(Dict, Dict0, #diameter_packet{msg = Msg}) ->
dict(Dict, Dict0, Msg);
dict(_Dict, Dict0, ['answer-message' | _]) ->
Dict0;
dict(Dict, Dict0, Rec) ->
try
'answer-message' = Dict0:rec2msg(element(1,Rec)),
Dict0
catch
error:_ -> Dict
end.
%% protocol_error/6
protocol_error(RC, TPid, Caps, Dict0, Fs, Pkt) ->
#diameter_caps{origin_host = {OH,_},
origin_realm = {OR,_}}
= Caps,
#diameter_packet{avps = Avps, errors = Es}
= Pkt,
?LOG({error, RC}, Pkt),
reply(answer_message({OH, OR, RC}, Dict0, Avps),
Dict0,
TPid,
Fs,
Pkt#diameter_packet{errors = [RC | Es]}).
%% Note that reply/5 may set the result code once more. It's set in
%% answer_message/3 in case reply/5 doesn't.
%% protocol_error/5
protocol_error(RC, TPid, Caps, Dict0, Pkt) ->
protocol_error(RC, TPid, Caps, Dict0, [], Pkt).
%% resend/7
%%
%% Resend a message as a relay or proxy agent.
resend(Opts,
#diameter_app{}
= App,
TPid,
#diameter_caps{origin_host = {OH,_}}
= Caps,
Dict0,
RecvData,
Fs,
#diameter_packet{avps = Avps}
= Pkt) ->
{Code, _Flags, Vid} = Dict0:avp_header('Route-Record'),
resend(is_loop(Code, Vid, OH, Dict0, Avps),
Opts,
App,
TPid,
Caps,
Dict0,
RecvData,
Fs,
Pkt).
%% DIAMETER_LOOP_DETECTED 3005
%% An agent detected a loop while trying to get the message to the
%% intended recipient. The message MAY be sent to an alternate peer,
%% if one is available, but the peer reporting the error has
%% identified a configuration problem.
resend(true, _Opts, _App, TPid, Caps, Dict0, _RecvData, Fs, Pkt) ->
protocol_error(3005, TPid, Caps, Dict0, Fs, Pkt);
%% 6.1.8. Relaying and Proxying Requests
%%
%% A relay or proxy agent MUST append a Route-Record AVP to all requests
%% forwarded. The AVP contains the identity of the peer the request was
%% received from.
resend(false,
Opts,
App,
TPid,
#diameter_caps{origin_host = {_,OH}}
= Caps,
Dict0,
#recvdata{service_name = SvcName,
sequence = Mask},
Fs,
#diameter_packet{header = Hdr0,
avps = Avps}
= Pkt) ->
Route = #diameter_avp{data = {Dict0, 'Route-Record', OH}},
Seq = diameter_session:sequence(Mask),
Hdr = Hdr0#diameter_header{hop_by_hop_id = Seq},
Msg = [Hdr, Route | Avps],
resend(send_request(SvcName, App, Msg, Opts), TPid, Caps, Dict0, Fs, Pkt).
%% The incoming request is relayed with the addition of a
%% Route-Record. Note the requirement on the return from call/4 below,
%% which places a requirement on the value returned by the
%% handle_answer callback of the application module in question.
%%
%% Note that there's nothing stopping the request from being relayed
%% back to the sender. A pick_peer callback may want to avoid this but
%% a smart peer might recognize the potential loop and choose another
%% route. A less smart one will probably just relay the request back
%% again and force us to detect the loop. A pick_peer that wants to
%% avoid this can specify filter to avoid the possibility.
%% Eg. {neg, {host, OH} where #diameter_caps{origin_host = {OH, _}}.
%%
%% RFC 6.3 says that a relay agent does not modify Origin-Host but
%% says nothing about a proxy. Assume it should behave the same way.
%% resend/6
%%
%% Relay a reply to a relayed request.
%% Answer from the peer: reset the hop by hop identifier and send.
resend(#diameter_packet{bin = B}
= Pkt,
TPid,
_Caps,
_Dict0,
Fs,
#diameter_packet{header = #diameter_header{hop_by_hop_id = Id},
transport_data = TD}) ->
P = Pkt#diameter_packet{bin = diameter_codec:hop_by_hop_id(Id, B),
transport_data = TD},
eval_packet(P, Fs),
send(TPid, P);
%% TODO: counters
%% Or not: DIAMETER_UNABLE_TO_DELIVER.
resend(_, TPid, Caps, Dict0, Fs, Pkt) ->
protocol_error(3002, TPid, Caps, Dict0, Fs, Pkt).
%% is_loop/5
%%
%% Is there a Route-Record AVP with our Origin-Host?
is_loop(Code,
Vid,
Bin,
_Dict0,
[#diameter_avp{code = Code, vendor_id = Vid, data = Bin} | _]) ->
true;
is_loop(_, _, _, _, []) ->
false;
is_loop(Code, Vid, OH, Dict0, [_ | Avps])
when is_binary(OH) ->
is_loop(Code, Vid, OH, Dict0, Avps);
is_loop(Code, Vid, OH, Dict0, Avps) ->
is_loop(Code, Vid, Dict0:avp(encode, OH, 'Route-Record'), Dict0, Avps).
%% reply/5
%%
%% Send a locally originating reply.
%% Skip the setting of Result-Code and Failed-AVP's below. This is
%% currently undocumented.
reply([Msg], Dict, TPid, Fs, Pkt)
when is_list(Msg);
is_tuple(Msg) ->
reply(Msg, Dict, TPid, Fs, Pkt#diameter_packet{errors = []});
%% No errors or a diameter_header/avp list.
reply(Msg, Dict, TPid, Fs, #diameter_packet{errors = Es} = ReqPkt)
when [] == Es;
is_record(hd(Msg), diameter_header) ->
Pkt = encode(Dict, make_answer_packet(Msg, ReqPkt), Fs),
incr(send, Pkt, Dict, TPid), %% count result codes in sent answers
send(TPid, Pkt);
%% Or not: set Result-Code and Failed-AVP AVP's.
reply(Msg, Dict, TPid, Fs, #diameter_packet{errors = [H|_] = Es} = Pkt) ->
reply(rc(Msg, rc(H), [A || {_,A} <- Es], Dict),
Dict,
TPid,
Fs,
Pkt#diameter_packet{errors = []}).
eval_packet(Pkt, Fs) ->
lists:foreach(fun(F) -> diameter_lib:eval([F,Pkt]) end, Fs).
%% make_answer_packet/2
%% A reply message clears the R and T flags and retains the P flag.
%% The E flag will be set at encode. 6.2 of 3588 requires the same P
%% flag on an answer as on the request. A #diameter_packet{} returned
%% from a handle_request callback can circumvent this by setting its
%% own header values.
make_answer_packet(#diameter_packet{header = Hdr,
msg = Msg,
transport_data = TD},
#diameter_packet{header = ReqHdr}) ->
Hdr0 = ReqHdr#diameter_header{version = ?DIAMETER_VERSION,
is_request = false,
is_error = undefined,
is_retransmitted = false},
#diameter_packet{header = fold_record(Hdr0, Hdr),
msg = Msg,
transport_data = TD};
%% Binaries and header/avp lists are sent as-is.
make_answer_packet(Bin, #diameter_packet{transport_data = TD})
when is_binary(Bin) ->
#diameter_packet{bin = Bin,
transport_data = TD};
make_answer_packet([#diameter_header{} | _] = Msg,
#diameter_packet{transport_data = TD}) ->
#diameter_packet{msg = Msg,
transport_data = TD};
%% Otherwise, preserve transport_data.
make_answer_packet(Msg, #diameter_packet{transport_data = TD} = Pkt) ->
make_answer_packet(#diameter_packet{msg = Msg, transport_data = TD}, Pkt).
%% rc/1
rc({RC, _}) ->
RC;
rc(RC) ->
RC.
%% rc/4
rc(#diameter_packet{msg = Rec} = Pkt, RC, Failed, DictT) ->
Pkt#diameter_packet{msg = rc(Rec, RC, Failed, DictT)};
rc(Rec, RC, Failed, DictT)
when is_integer(RC) ->
set(Rec,
lists:append([rc(Rec, {'Result-Code', RC}, DictT),
failed_avp(Rec, Failed, DictT)]),
DictT).
%% Reply as name and tuple list ...
set([_|_] = Ans, Avps, _) ->
Ans ++ Avps; %% Values nearer tail take precedence.
%% ... or record.
set(Rec, Avps, Dict) ->
Dict:'#set-'(Avps, Rec).
%% rc/3
%%
%% Turn the result code into a list if its optional and only set it if
%% the arity is 1 or {0,1}. In other cases (which probably shouldn't
%% exist in practise) we can't know what's appropriate.
rc([MsgName | _], {'Result-Code' = K, RC} = T, Dict) ->
case Dict:avp_arity(MsgName, 'Result-Code') of
1 -> [T];
{0,1} -> [{K, [RC]}];
_ -> []
end;
rc(Rec, T, Dict) ->
rc([Dict:rec2msg(element(1, Rec))], T, Dict).
%% failed_avp/3
failed_avp(_, [] = No, _) ->
No;
failed_avp(Rec, Failed, Dict) ->
[fa(Rec, [{'AVP', Failed}], Dict)].
%% Reply as name and tuple list ...
fa([MsgName | Values], FailedAvp, Dict) ->
R = Dict:msg2rec(MsgName),
try
Dict:'#info-'(R, {index, 'Failed-AVP'}),
{'Failed-AVP', [FailedAvp]}
catch
error: _ ->
Avps = proplists:get_value('AVP', Values, []),
A = #diameter_avp{name = 'Failed-AVP',
value = FailedAvp},
{'AVP', [A|Avps]}
end;
%% ... or record.
fa(Rec, FailedAvp, Dict) ->
try
{'Failed-AVP', [FailedAvp]}
catch
error: _ ->
Avps = Dict:'get-'('AVP', Rec),
A = #diameter_avp{name = 'Failed-AVP',
value = FailedAvp},
{'AVP', [A|Avps]}
end.
%% 3. Diameter Header
%%
%% E(rror) - If set, the message contains a protocol error,
%% and the message will not conform to the ABNF
%% described for this command. Messages with the 'E'
%% bit set are commonly referred to as error
%% messages. This bit MUST NOT be set in request
%% messages. See Section 7.2.
%% 3.2. Command Code ABNF specification
%%
%% e-bit = ", ERR"
%% ; If present, the 'E' bit in the Command
%% ; Flags is set, indicating that the answer
%% ; message contains a Result-Code AVP in
%% ; the "protocol error" class.
%% 7.1.3. Protocol Errors
%%
%% Errors that fall within the Protocol Error category SHOULD be treated
%% on a per-hop basis, and Diameter proxies MAY attempt to correct the
%% error, if it is possible. Note that these and only these errors MUST
%% only be used in answer messages whose 'E' bit is set.
%% Thus, only construct answers to protocol errors. Other errors
%% require an message-specific answer and must be handled by the
%% application.
%% 6.2. Diameter Answer Processing
%%
%% When a request is locally processed, the following procedures MUST be
%% applied to create the associated answer, in addition to any
%% additional procedures that MAY be discussed in the Diameter
%% application defining the command:
%%
%% - The same Hop-by-Hop identifier in the request is used in the
%% answer.
%%
%% - The local host's identity is encoded in the Origin-Host AVP.
%%
%% - The Destination-Host and Destination-Realm AVPs MUST NOT be
%% present in the answer message.
%%
%% - The Result-Code AVP is added with its value indicating success or
%% failure.
%%
%% - If the Session-Id is present in the request, it MUST be included
%% in the answer.
%%
%% - Any Proxy-Info AVPs in the request MUST be added to the answer
%% message, in the same order they were present in the request.
%%
%% - The 'P' bit is set to the same value as the one in the request.
%%
%% - The same End-to-End identifier in the request is used in the
%% answer.
%%
%% Note that the error messages (see Section 7.3) are also subjected to
%% the above processing rules.
%% 7.3. Error-Message AVP
%%
%% The Error-Message AVP (AVP Code 281) is of type UTF8String. It MAY
%% accompany a Result-Code AVP as a human readable error message. The
%% Error-Message AVP is not intended to be useful in real-time, and
%% SHOULD NOT be expected to be parsed by network entities.
%% answer_message/3
answer_message({OH, OR, RC}, Dict0, Avps) ->
{Code, _, Vid} = Dict0:avp_header('Session-Id'),
['answer-message', {'Origin-Host', OH},
{'Origin-Realm', OR},
{'Result-Code', RC}
| session_id(Code, Vid, Dict0, Avps)].
session_id(Code, Vid, Dict0, Avps)
when is_list(Avps) ->
try
{value, #diameter_avp{data = D}} = find_avp(Code, Vid, Avps),
[{'Session-Id', [Dict0:avp(decode, D, 'Session-Id')]}]
catch
error: _ ->
[]
end.
%% find_avp/3
find_avp(Code, Vid, Avps)
when is_integer(Code), (undefined == Vid orelse is_integer(Vid)) ->
find(fun(A) -> is_avp(Code, Vid, A) end, Avps).
%% The final argument here could be a list of AVP's, depending on the case,
%% but we're only searching at the top level.
is_avp(Code, Vid, #diameter_avp{code = Code, vendor_id = Vid}) ->
true;
is_avp(_, _, _) ->
false.
find(_, []) ->
false;
find(Pred, [H|T]) ->
case Pred(H) of
true ->
{value, H};
false ->
find(Pred, T)
end.
%% 7. Error Handling
%%
%% There are certain Result-Code AVP application errors that require
%% additional AVPs to be present in the answer. In these cases, the
%% Diameter node that sets the Result-Code AVP to indicate the error
%% MUST add the AVPs. Examples are:
%%
%% - An unrecognized AVP is received with the 'M' bit (Mandatory bit)
%% set, causes an answer to be sent with the Result-Code AVP set to
%% DIAMETER_AVP_UNSUPPORTED, and the Failed-AVP AVP containing the
%% offending AVP.
%%
%% - An AVP that is received with an unrecognized value causes an
%% answer to be returned with the Result-Code AVP set to
%% DIAMETER_INVALID_AVP_VALUE, with the Failed-AVP AVP containing the
%% AVP causing the error.
%%
%% - A command is received with an AVP that is omitted, yet is
%% mandatory according to the command's ABNF. The receiver issues an
%% answer with the Result-Code set to DIAMETER_MISSING_AVP, and
%% creates an AVP with the AVP Code and other fields set as expected
%% in the missing AVP. The created AVP is then added to the Failed-
%% AVP AVP.
%%
%% The Result-Code AVP describes the error that the Diameter node
%% encountered in its processing. In case there are multiple errors,
%% the Diameter node MUST report only the first error it encountered
%% (detected possibly in some implementation dependent order). The
%% specific errors that can be described by this AVP are described in
%% the following section.
%% 7.5. Failed-AVP AVP
%%
%% The Failed-AVP AVP (AVP Code 279) is of type Grouped and provides
%% debugging information in cases where a request is rejected or not
%% fully processed due to erroneous information in a specific AVP. The
%% value of the Result-Code AVP will provide information on the reason
%% for the Failed-AVP AVP.
%%
%% The possible reasons for this AVP are the presence of an improperly
%% constructed AVP, an unsupported or unrecognized AVP, an invalid AVP
%% value, the omission of a required AVP, the presence of an explicitly
%% excluded AVP (see tables in Section 10), or the presence of two or
%% more occurrences of an AVP which is restricted to 0, 1, or 0-1
%% occurrences.
%%
%% A Diameter message MAY contain one Failed-AVP AVP, containing the
%% entire AVP that could not be processed successfully. If the failure
%% reason is omission of a required AVP, an AVP with the missing AVP
%% code, the missing vendor id, and a zero filled payload of the minimum
%% required length for the omitted AVP will be added.
%% incr/4
%%
%% Increment a stats counter for an incoming or outgoing message.
%% Outgoing message as binary: don't count. (Sending binaries is only
%% partially supported.)
incr(_, #diameter_packet{msg = undefined}, _, _) ->
ok;
incr(recv = D, #diameter_packet{header = H, errors = [_|_]}, _, TPid) ->
incr(TPid, {diameter_codec:msg_id(H), D, error});
incr(Dir, Pkt, Dict, TPid) ->
#diameter_packet{header = #diameter_header{is_error = E}
= Hdr,
msg = Rec}
= Pkt,
RC = int(get_avp_value(Dict, 'Result-Code', Rec)),
PE = is_protocol_error(RC),
%% Check that the E bit is set only for 3xxx result codes.
(not (E orelse PE))
orelse (E andalso PE)
orelse x({invalid_error_bit, RC}, answer, [Dir, Pkt]),
irc(TPid, Hdr, Dir, rc_counter(Dict, Rec, RC)).
irc(_, _, _, undefined) ->
false;
irc(TPid, Hdr, Dir, Ctr) ->
incr(TPid, {diameter_codec:msg_id(Hdr), Dir, Ctr}).
%% incr/2
incr(TPid, Counter) ->
diameter_stats:incr(Counter, TPid, 1).
%% error_counter/2
%% RFC 3588, 7.6:
%%
%% All Diameter answer messages defined in vendor-specific
%% applications MUST include either one Result-Code AVP or one
%% Experimental-Result AVP.
%%
%% Maintain statistics assuming one or the other, not both, which is
%% surely the intent of the RFC.
rc_counter(Dict, Rec, undefined) ->
rcc(get_avp_value(Dict, 'Experimental-Result', Rec));
rc_counter(_, _, RC) ->
{'Result-Code', RC}.
%% Outgoing answers may be in any of the forms messages can be sent
%% in. Incoming messages will be records. We're assuming here that the
%% arity of the result code AVP's is 0 or 1.
rcc([{_,_,N} = T | _])
when is_integer(N) ->
T;
rcc({_,_,N} = T)
when is_integer(N) ->
T;
rcc(_) ->
undefined.
%% Extract the first good looking integer. There's no guarantee
%% that what we're looking for has arity 1.
int([N|_])
when is_integer(N) ->
N;
int(N)
when is_integer(N) ->
N;
int(_) ->
undefined.
is_protocol_error(RC) ->
3000 =< RC andalso RC < 4000.
-spec x(any(), atom(), list()) -> no_return().
%% Warn and exit request process on errors in an incoming answer.
x(Reason, F, A) ->
diameter_lib:warning_report(Reason, {?MODULE, F, A}),
x(Reason).
x(T) ->
exit(T).
%% ---------------------------------------------------------------------------
%% # send_request/4
%%
%% Handle an outgoing Diameter request.
%% ---------------------------------------------------------------------------
send_request(SvcName, AppOrAlias, Msg, Options)
when is_list(Options) ->
Rec = make_options(Options),
Ref = make_ref(),
Caller = {self(), Ref},
ReqF = fun() ->
exit({Ref, send_R(SvcName, AppOrAlias, Msg, Rec, Caller)})
end,
try spawn_monitor(ReqF) of
{_, MRef} ->
recv_A(MRef, Ref, Rec#options.detach, false)
catch
error: system_limit = E ->
{error, E}
end.
%% The R in send_R is because Diameter request are usually given short
%% names of the form XXR. (eg. CER, DWR, etc.) Similarly, answers have
%% names of the form XXA.
%% Don't rely on gen_server:call/3 for the timeout handling since it
%% makes no guarantees about not leaving a reply message in the
%% mailbox if we catch its exit at timeout. It currently *can* do so,
%% which is also undocumented.
recv_A(MRef, _, true, true) ->
erlang:demonitor(MRef, [flush]),
ok;
recv_A(MRef, Ref, Detach, Sent) ->
receive
Ref -> %% send has been attempted
recv_A(MRef, Ref, Detach, true);
{'DOWN', MRef, process, _, Reason} ->
answer_rc(Reason, Ref, Sent)
end.
%% send_R/5 has returned ...
answer_rc({Ref, Ans}, Ref, _) ->
Ans;
%% ... or not. Note that failure/encode are documented return values.
answer_rc(_, _, Sent) ->
{error, choose(Sent, failure, encode)}.
%% send_R/5
%%
%% In the process spawned for the outgoing request.
send_R(SvcName, AppOrAlias, Msg, Opts, Caller) ->
case pick_peer(SvcName, AppOrAlias, Msg, Opts) of
{{_,_,_} = Transport, Mask} ->
send_request(Transport, Mask, Msg, Opts, Caller, SvcName);
false ->
{error, no_connection};
{error, _} = No ->
No
end.
%% make_options/1
make_options(Options) ->
lists:foldl(fun mo/2, #options{}, Options).
mo({timeout, T}, Rec)
when is_integer(T), 0 =< T ->
Rec#options{timeout = T};
mo({filter, F}, #options{filter = none} = Rec) ->
Rec#options{filter = F};
mo({filter, F}, #options{filter = {all, Fs}} = Rec) ->
Rec#options{filter = {all, [F | Fs]}};
mo({filter, F}, #options{filter = F0} = Rec) ->
Rec#options{filter = {all, [F0, F]}};
mo({extra, L}, #options{extra = X} = Rec)
when is_list(L) ->
Rec#options{extra = X ++ L};
mo(detach, Rec) ->
Rec#options{detach = true};
mo(T, _) ->
?ERROR({invalid_option, T}).
%% ---------------------------------------------------------------------------
%% # send_request/6
%% ---------------------------------------------------------------------------
%% Send an outgoing request in its dedicated process.
%%
%% Note that both encode of the outgoing request and of the received
%% answer happens in this process. It's also this process that replies
%% to the caller. The service process only handles the state-retaining
%% callbacks.
%%
%% The module field of the #diameter_app{} here includes any extra
%% arguments passed to diameter:call/4.
send_request({TPid, Caps, App}
= Transport,
Mask,
Msg,
Opts,
Caller,
SvcName) ->
Pkt = make_prepare_packet(Mask, Msg),
send_R(cb(App, prepare_request, [Pkt, SvcName, {TPid, Caps}]),
Pkt,
Transport,
Opts,
Caller,
SvcName,
[]).
send_R({send, Msg}, Pkt, Transport, Opts, Caller, SvcName, Fs) ->
send_R(make_request_packet(Msg, Pkt),
Transport,
Opts,
Caller,
SvcName,
Fs);
send_R({discard, Reason} , _, _, _, _, _, _) ->
{error, Reason};
send_R(discard, _, _, _, _, _, _) ->
{error, discarded};
send_R({eval_packet, RC, F}, Pkt, T, Opts, Caller, SvcName, Fs) ->
send_R(RC, Pkt, T, Opts, Caller, SvcName, [F|Fs]);
send_R(E, _, {_, _, App}, _, _, _, _) ->
?ERROR({invalid_return, prepare_request, App, E}).
%% make_prepare_packet/2
%%
%% Turn an outgoing request as passed to call/4 into a diameter_packet
%% record in preparation for a prepare_request callback.
make_prepare_packet(_, Bin)
when is_binary(Bin) ->
#diameter_packet{header = diameter_codec:decode_header(Bin),
bin = Bin};
make_prepare_packet(Mask, #diameter_packet{msg = [#diameter_header{} = Hdr
| Avps]}
= Pkt) ->
Pkt#diameter_packet{msg = [make_prepare_header(Mask, Hdr) | Avps]};
make_prepare_packet(Mask, #diameter_packet{header = Hdr} = Pkt) ->
Pkt#diameter_packet{header = make_prepare_header(Mask, Hdr)};
make_prepare_packet(Mask, Msg) ->
make_prepare_packet(Mask, #diameter_packet{msg = Msg}).
%% make_prepare_header/2
make_prepare_header(Mask, undefined) ->
Seq = diameter_session:sequence(Mask),
make_prepare_header(#diameter_header{end_to_end_id = Seq,
hop_by_hop_id = Seq});
make_prepare_header(Mask, #diameter_header{end_to_end_id = undefined,
hop_by_hop_id = undefined}
= H) ->
Seq = diameter_session:sequence(Mask),
make_prepare_header(H#diameter_header{end_to_end_id = Seq,
hop_by_hop_id = Seq});
make_prepare_header(Mask, #diameter_header{end_to_end_id = undefined} = H) ->
Seq = diameter_session:sequence(Mask),
make_prepare_header(H#diameter_header{end_to_end_id = Seq});
make_prepare_header(Mask, #diameter_header{hop_by_hop_id = undefined} = H) ->
Seq = diameter_session:sequence(Mask),
make_prepare_header(H#diameter_header{hop_by_hop_id = Seq});
make_prepare_header(_, Hdr) ->
make_prepare_header(Hdr).
%% make_prepare_header/1
make_prepare_header(#diameter_header{version = undefined} = Hdr) ->
make_prepare_header(Hdr#diameter_header{version = ?DIAMETER_VERSION});
make_prepare_header(#diameter_header{} = Hdr) ->
Hdr;
make_prepare_header(T) ->
?ERROR({invalid_header, T}).
%% make_request_packet/2
%%
%% Reconstruct a diameter_packet from the return value of
%% prepare_request or prepare_retransmit callback.
make_request_packet(Bin, _)
when is_binary(Bin) ->
make_prepare_packet(false, Bin);
make_request_packet(#diameter_packet{msg = [#diameter_header{} | _]}
= Pkt,
_) ->
Pkt;
%% Returning a diameter_packet with no header from a prepare_request
%% or prepare_retransmit callback retains the header passed into it.
%% This is primarily so that the end to end and hop by hop identifiers
%% are retained.
make_request_packet(#diameter_packet{header = Hdr} = Pkt,
#diameter_packet{header = Hdr0}) ->
Pkt#diameter_packet{header = fold_record(Hdr0, Hdr)};
make_request_packet(Msg, Pkt) ->
Pkt#diameter_packet{msg = Msg}.
%% fold_record/2
fold_record(undefined, R) ->
R;
fold_record(Rec, R) ->
diameter_lib:fold_tuple(2, Rec, R).
%% send_R/6
send_R(Pkt0,
{TPid, Caps, #diameter_app{dictionary = Dict} = App},
Opts,
{Pid, Ref},
SvcName,
Fs) ->
Pkt = encode(Dict, Pkt0, Fs),
#options{timeout = Timeout}
= Opts,
Req = #request{ref = Ref,
caller = Pid,
handler = self(),
transport = TPid,
caps = Caps,
packet = Pkt0},
try
TRef = send_request(TPid, Pkt, Req, SvcName, Timeout),
Pid ! Ref, %% tell caller a send has been attempted
handle_answer(SvcName,
App,
recv_A(Timeout, SvcName, App, Opts, {TRef, Req}))
after
erase_requests(Pkt)
end.
%% recv_A/5
recv_A(Timeout, SvcName, App, Opts, {TRef, #request{ref = Ref} = Req}) ->
%% Matching on TRef below ensures we ignore messages that pertain
%% to a previous transport prior to failover. The answer message
%% includes the #request{} since it's not necessarily Req; that
%% is, from the last peer to which we've transmitted.
receive
{answer = A, Ref, Rq, Dict0, Pkt} -> %% Answer from peer
{A, Rq, Dict0, Pkt};
{timeout = Reason, TRef, _} -> %% No timely reply
{error, Req, Reason};
{failover, TRef} -> %% Service says peer has gone down
retransmit(pick_peer(SvcName, App, Req, Opts),
Req,
Opts,
SvcName,
Timeout)
end.
%% handle_answer/3
handle_answer(SvcName, App, {error, Req, Reason}) ->
handle_error(App, Req, Reason, SvcName);
handle_answer(SvcName,
#diameter_app{dictionary = Dict}
= App,
{answer, Req, Dict0, Pkt}) ->
Mod = dict(Dict, Dict0, Pkt),
answer(examine(diameter_codec:decode(Mod, Pkt)),
SvcName,
Mod,
App,
Req).
%% We don't really need to do a full decode if we're a relay and will
%% just resend with a new hop by hop identifier, but might a proxy
%% want to examine the answer?
answer(Pkt, SvcName, Dict, App, #request{transport = TPid} = Req) ->
try
incr(recv, Pkt, Dict, TPid)
of
_ -> answer(Pkt, SvcName, App, Req)
catch
exit: {invalid_error_bit, _} = E ->
answer(Pkt#diameter_packet{errors = [E]}, SvcName, App, Req)
end.
answer(Pkt,
SvcName,
#diameter_app{module = ModX,
options = [{answer_errors, AE} | _]},
Req) ->
a(Pkt, SvcName, ModX, AE, Req).
a(#diameter_packet{errors = Es}
= Pkt,
SvcName,
ModX,
AE,
#request{transport = TPid,
caps = Caps,
packet = P})
when [] == Es;
callback == AE ->
cb(ModX, handle_answer, [Pkt, msg(P), SvcName, {TPid, Caps}]);
a(Pkt, SvcName, _, report, Req) ->
x(errors, handle_answer, [SvcName, Req, Pkt]);
a(Pkt, SvcName, _, discard, Req) ->
x({errors, handle_answer, [SvcName, Req, Pkt]}).
%% Note that we don't check that the application id in the answer's
%% header is what we expect. (TODO: Does the rfc says anything about
%% this?)
%% Note that failover starts a new timer and that expiry of an old
%% timer value is ignored. This means that an answer could be accepted
%% from a peer after timeout in the case of failover.
retransmit({{_,_,App} = Transport, _Mask}, Req, Opts, SvcName, Timeout) ->
try retransmit(Transport, Req, SvcName, Timeout) of
T -> recv_A(Timeout, SvcName, App, Opts, T)
catch
?FAILURE(Reason) -> {error, Req, Reason}
end;
retransmit(_, Req, _, _, _) -> %% no alternate peer
{error, Req, failover}.
%% pick_peer/4
%% Retransmission after failover: call-specific arguments have already
%% been appended in App.
pick_peer(SvcName,
App,
#request{packet = #diameter_packet{msg = Msg}},
Opts) ->
pick_peer(SvcName, App, Msg, Opts#options{extra = []});
pick_peer(_, _, undefined, _) ->
false;
pick_peer(SvcName,
AppOrAlias,
Msg,
#options{filter = Filter, extra = Xtra}) ->
diameter_service:pick_peer(SvcName,
AppOrAlias,
{fun(D) -> get_destination(D, Msg) end,
Filter,
Xtra}).
%% handle_error/4
handle_error(App,
#request{packet = Pkt,
transport = TPid,
caps = Caps},
Reason,
SvcName) ->
cb(App, handle_error, [Reason, msg(Pkt), SvcName, {TPid, Caps}]).
msg(#diameter_packet{msg = undefined, bin = Bin}) ->
Bin;
msg(#diameter_packet{msg = Msg}) ->
Msg.
%% encode/3
encode(Dict, Pkt, Fs) ->
P = encode(Dict, Pkt),
eval_packet(P, Fs),
P.
%% encode/2
%% Note that prepare_request can return a diameter_packet containing a
%% header or transport_data. Even allow the returned record to contain
%% an encoded binary. This isn't the usual case and doesn't properly
%% support retransmission but is useful for test.
%% A message to be encoded.
encode(Dict, #diameter_packet{bin = undefined} = Pkt) ->
diameter_codec:encode(Dict, Pkt);
%% An encoded binary: just send.
encode(_, #diameter_packet{} = Pkt) ->
Pkt.
%% send_request/5
send_request(TPid, #diameter_packet{bin = Bin} = Pkt, Req, _SvcName, Timeout)
when node() == node(TPid) ->
%% Store the outgoing request before sending to avoid a race with
%% reply reception.
TRef = store_request(TPid, Bin, Req, Timeout),
send(TPid, Pkt),
TRef;
%% Send using a remote transport: spawn a process on the remote node
%% to relay the answer.
send_request(TPid, #diameter_packet{} = Pkt, Req, SvcName, Timeout) ->
TRef = erlang:start_timer(Timeout, self(), TPid),
T = {TPid, Pkt, Req, SvcName, Timeout, TRef},
spawn(node(TPid), ?MODULE, send, [T]),
TRef.
%% send/1
send({TPid, Pkt, #request{handler = Pid} = Req, SvcName, Timeout, TRef}) ->
Ref = send_request(TPid,
Pkt,
Req#request{handler = self()},
SvcName,
Timeout),
Pid ! reref(receive T -> T end, Ref, TRef).
reref({T, Ref, R}, Ref, TRef) ->
{T, TRef, R};
reref(T, _, _) ->
T.
%% send/2
send(Pid, Pkt) ->
Pid ! {send, Pkt}.
%% retransmit/4
retransmit({TPid, Caps, App}
= Transport,
#request{packet = Pkt0}
= Req,
SvcName,
Timeout) ->
have_request(Pkt0, TPid) %% Don't failover to a peer we've
andalso ?THROW(timeout), %% already sent to.
#diameter_packet{header = Hdr0} = Pkt0,
Hdr = Hdr0#diameter_header{is_retransmitted = true},
Pkt = Pkt0#diameter_packet{header = Hdr},
retransmit(cb(App, prepare_retransmit, [Pkt, SvcName, {TPid, Caps}]),
Transport,
Req#request{packet = Pkt},
SvcName,
Timeout,
[]).
retransmit({send, Msg},
Transport,
#request{packet = Pkt}
= Req,
SvcName,
Timeout,
Fs) ->
resend_request(make_request_packet(Msg, Pkt),
Transport,
Req,
SvcName,
Timeout,
Fs);
retransmit({discard, Reason}, _, _, _, _, _) ->
?THROW(Reason);
retransmit(discard, _, _, _, _, _) ->
?THROW(discarded);
retransmit({eval_packet, RC, F}, Transport, Req, SvcName, Timeout, Fs) ->
retransmit(RC, Transport, Req, SvcName, Timeout, [F|Fs]);
retransmit(T, {_, _, App}, _, _, _, _) ->
?ERROR({invalid_return, prepare_retransmit, App, T}).
resend_request(Pkt0,
{TPid, Caps, #diameter_app{dictionary = Dict}},
Req0,
SvcName,
Tmo,
Fs) ->
Pkt = encode(Dict, Pkt0, Fs),
Req = Req0#request{transport = TPid,
packet = Pkt0,
caps = Caps},
?LOG(retransmission, Req),
TRef = send_request(TPid, Pkt, Req, SvcName, Tmo),
{TRef, Req}.
%% store_request/4
store_request(TPid, Bin, Req, Timeout) ->
Seqs = diameter_codec:sequence_numbers(Bin),
TRef = erlang:start_timer(Timeout, self(), timeout),
ets:insert(?REQUEST_TABLE, {Seqs, Req, TRef}),
ets:member(?REQUEST_TABLE, TPid)
orelse (self() ! {failover, TRef}), %% failover/1 may have missed
TRef.
%% lookup_request/2
lookup_request(Msg, TPid) ->
Seqs = diameter_codec:sequence_numbers(Msg),
Spec = [{{Seqs, #request{transport = TPid, _ = '_'}, '_'},
[],
['$_']}],
case ets:select(?REQUEST_TABLE, Spec) of
[{_, Req, _}] ->
Req;
[] ->
false
end.
%% erase_requests/1
erase_requests(Pkt) ->
ets:delete(?REQUEST_TABLE, diameter_codec:sequence_numbers(Pkt)).
%% match_requests/1
match_requests(TPid) ->
Pat = {'_', #request{transport = TPid, _ = '_'}, '_'},
ets:select(?REQUEST_TABLE, [{Pat, [], ['$_']}]).
%% have_request/2
have_request(Pkt, TPid) ->
Seqs = diameter_codec:sequence_numbers(Pkt),
Pat = {Seqs, #request{transport = TPid, _ = '_'}, '_'},
'$end_of_table' /= ets:select(?REQUEST_TABLE, [{Pat, [], ['$_']}], 1).
%% ---------------------------------------------------------------------------
%% # failover/1-2
%% ---------------------------------------------------------------------------
failover(TPid)
when is_pid(TPid) ->
lists:foreach(fun failover/1, match_requests(TPid));
%% Note that a request process can store its request after failover
%% notifications are sent here: store_request/4 sends the notification
%% in that case.
%% Failover as a consequence of request_peer_down/1: inform the
%% request process.
failover({_, Req, TRef}) ->
#request{handler = Pid,
packet = #diameter_packet{msg = M}}
= Req,
M /= undefined andalso (Pid ! {failover, TRef}).
%% Failover is not performed when msg = binary() since sending
%% pre-encoded binaries is only partially supported. (Mostly for
%% test.)
%% get_destination/2
get_destination(Dict, Msg) ->
[str(get_avp_value(Dict, D, Msg)) || D <- ['Destination-Realm',
'Destination-Host']].
%% This is not entirely correct. The avp could have an arity 1, in
%% which case an empty list is a DiameterIdentity of length 0 rather
%% than the list of no values we treat it as by mapping to undefined.
%% This behaviour is documented.
str([]) ->
undefined;
str(T) ->
T.
%% get_avp_value/3
%%
%% Find an AVP in a message of one of three forms:
%%
%% - a message record (as generated from a .dia spec) or
%% - a list of an atom message name followed by 2-tuple, avp name/value pairs.
%% - a list of a #diameter_header{} followed by #diameter_avp{} records,
%%
%% In the first two forms a dictionary module is used at encode to
%% identify the type of the AVP and its arity in the message in
%% question. The third form allows messages to be sent as is, without
%% a dictionary, which is needed in the case of relay agents, for one.
%% Messages will be header/avps list as a relay and the only AVP's we
%% look for are in the common dictionary. This is required since the
%% relay dictionary doesn't inherit the common dictionary (which maybe
%% it should).
get_avp_value(?RELAY, Name, Msg) ->
get_avp_value(?BASE, Name, Msg);
%% Message sent as a header/avps list, probably a relay case but not
%% necessarily.
get_avp_value(Dict, Name, [#diameter_header{} | Avps]) ->
try
{Code, _, VId} = Dict:avp_header(Name),
[A|_] = lists:dropwhile(fun(#diameter_avp{code = C, vendor_id = V}) ->
C /= Code orelse V /= VId
end,
Avps),
avp_decode(Dict, Name, A)
catch
error: _ ->
undefined
end;
%% Outgoing message as a name/values list.
get_avp_value(_, Name, [_MsgName | Avps]) ->
case lists:keyfind(Name, 1, Avps) of
{_, V} ->
V;
_ ->
undefined
end;
%% Message is typically a record but not necessarily.
get_avp_value(Dict, Name, Rec) ->
try
Dict:'#get-'(Name, Rec)
catch
error:_ ->
undefined
end.
avp_decode(Dict, Name, #diameter_avp{value = undefined,
data = Bin}) ->
Dict:avp(decode, Bin, Name);
avp_decode(_, _, #diameter_avp{value = V}) ->
V.
cb(#diameter_app{module = [_|_] = M}, F, A) ->
eval(M, F, A);
cb([_|_] = M, F, A) ->
eval(M, F, A).
eval([M|X], F, A) ->
apply(M, F, A ++ X).
choose(true, X, _) -> X;
choose(false, _, X) -> X.
