%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 2010-2013. 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%
%%
-module(diameter_codec).
-export([encode/2,
decode/2,
decode/3,
collect_avps/1,
decode_header/1,
sequence_numbers/1,
hop_by_hop_id/2,
msg_name/2,
msg_id/1]).
%% Towards generated encoders (from diameter_gen.hrl).
-export([pack_avp/1,
pack_avp/2]).
-include_lib("diameter/include/diameter.hrl").
-include("diameter_internal.hrl").
-define(MASK(N,I), ((I) band (1 bsl (N)))).
%% 0 1 2 3
%% 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
%% +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
%% | Version | Message Length |
%% +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
%% | command flags | Command-Code |
%% +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
%% | Application-ID |
%% +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
%% | Hop-by-Hop Identifier |
%% +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
%% | End-to-End Identifier |
%% +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
%% | AVPs ...
%% +-+-+-+-+-+-+-+-+-+-+-+-+-
%%% ---------------------------------------------------------------------------
%%% # encode/[2-4]
%%% ---------------------------------------------------------------------------
encode(Mod, #diameter_packet{} = Pkt) ->
try
e(Mod, Pkt)
catch
error: Reason ->
%% Be verbose since a crash report may be truncated and
%% encode errors are self-inflicted.
X = {?MODULE, encode, {Reason, ?STACK}},
diameter_lib:error_report(X, {?MODULE, encode, [Mod, Pkt]}),
exit(X)
end;
encode(Mod, Msg) ->
Seq = diameter_session:sequence(),
Hdr = #diameter_header{version = ?DIAMETER_VERSION,
end_to_end_id = Seq,
hop_by_hop_id = Seq},
encode(Mod, #diameter_packet{header = Hdr,
msg = Msg}).
e(_, #diameter_packet{msg = [#diameter_header{} = Hdr | As]} = Pkt) ->
Avps = encode_avps(As),
Length = size(Avps) + 20,
#diameter_header{version = Vsn,
cmd_code = Code,
application_id = Aid,
hop_by_hop_id = Hid,
end_to_end_id = Eid}
= Hdr,
Flags = make_flags(0, Hdr),
Pkt#diameter_packet{header = Hdr,
bin = <<Vsn:8, Length:24,
Flags:8, Code:24,
Aid:32,
Hid:32,
Eid:32,
Avps/binary>>};
e(Mod, #diameter_packet{header = Hdr, msg = Msg} = Pkt) ->
#diameter_header{version = Vsn,
hop_by_hop_id = Hid,
end_to_end_id = Eid}
= Hdr,
MsgName = rec2msg(Mod, Msg),
{Code, Flags0, Aid} = msg_header(Mod, MsgName, Hdr),
Flags = make_flags(Flags0, Hdr),
Avps = encode_avps(Mod, MsgName, values(Msg)),
Length = size(Avps) + 20,
Pkt#diameter_packet{header = Hdr#diameter_header
{length = Length,
cmd_code = Code,
application_id = Aid,
is_request = 0 /= ?MASK(7, Flags),
is_proxiable = 0 /= ?MASK(6, Flags),
is_error = 0 /= ?MASK(5, Flags),
is_retransmitted = 0 /= ?MASK(4, Flags)},
bin = <<Vsn:8, Length:24,
Flags:8, Code:24,
Aid:32,
Hid:32,
Eid:32,
Avps/binary>>}.
%% make_flags/2
make_flags(Flags0, #diameter_header{is_request = R,
is_proxiable = P,
is_error = E,
is_retransmitted = T}) ->
{Flags, 3} = lists:foldl(fun(B,{F,N}) -> {mf(B,F,N), N-1} end,
{Flags0, 7},
[R,P,E,T]),
Flags.
mf(undefined, F, _) ->
F;
mf(B, F, N) -> %% reset the affected bit
(F bxor (F band (1 bsl N))) bor bit(B, N).
bit(true, N) -> 1 bsl N;
bit(false, _) -> 0.
%% values/1
values([H|T])
when is_atom(H) ->
T;
values(Avps) ->
Avps.
%% encode_avps/3
%% Specifying values as a #diameter_avp list bypasses arity and other
%% checks: the values are expected to be already encoded and the AVP's
%% presented are simply sent. This is needed for relay agents, since
%% these have to be able to resend whatever comes.
%% Message as a list of #diameter_avp{} ...
encode_avps(_, _, [#diameter_avp{} | _] = Avps) ->
encode_avps(reorder(Avps, [], Avps));
%% ... or as a tuple list or record.
encode_avps(Mod, MsgName, Values) ->
Mod:encode_avps(MsgName, Values).
%% reorder/1
reorder([#diameter_avp{index = 0} | _] = Avps, Acc, _) ->
Avps ++ Acc;
reorder([#diameter_avp{index = N} = A | Avps], Acc, _)
when is_integer(N) ->
lists:reverse(Avps, [A | Acc]);
reorder([H | T], Acc, Avps) ->
reorder(T, [H | Acc], Avps);
reorder([], Acc, _) ->
Acc.
%% encode_avps/1
encode_avps(Avps) ->
list_to_binary(lists:map(fun pack_avp/1, Avps)).
%% msg_header/3
msg_header(Mod, 'answer-message' = MsgName, Header) ->
0 = Mod:id(), %% assert
#diameter_header{application_id = Aid,
cmd_code = Code}
= Header,
{-1, Flags, ?DIAMETER_APP_ID_COMMON} = Mod:msg_header(MsgName),
{Code, Flags, Aid};
msg_header(Mod, MsgName, _) ->
Mod:msg_header(MsgName).
%% rec2msg/2
rec2msg(_, [Name|_])
when is_atom(Name) ->
Name;
rec2msg(Mod, Rec) ->
Mod:rec2msg(element(1, Rec)).
%%% ---------------------------------------------------------------------------
%%% # decode/2
%%% ---------------------------------------------------------------------------
%% Unsuccessfully decoded AVPs will be placed in #diameter_packet.errors.
decode(Mod, Pkt) ->
decode(Mod:id(), Mod, Pkt).
%% If we're a relay application then just extract the avp's without
%% any decoding of their data since we don't know the application in
%% question.
decode(?APP_ID_RELAY, _, #diameter_packet{} = Pkt) ->
case collect_avps(Pkt) of
{Bs, As} ->
Pkt#diameter_packet{avps = As,
errors = [Bs]};
As ->
Pkt#diameter_packet{avps = As}
end;
%% Otherwise decode using the dictionary.
decode(_, Mod, #diameter_packet{header = Hdr} = Pkt) ->
#diameter_header{cmd_code = CmdCode,
is_request = IsRequest,
is_error = IsError}
= Hdr,
MsgName = if IsError andalso not IsRequest ->
'answer-message';
true ->
Mod:msg_name(CmdCode, IsRequest)
end,
decode_avps(MsgName, Mod, Pkt, collect_avps(Pkt));
decode(Id, Mod, Bin)
when is_bitstring(Bin) ->
decode(Id, Mod, #diameter_packet{header = decode_header(Bin), bin = Bin}).
decode_avps(MsgName, Mod, Pkt, {Bs, Avps}) -> %% invalid avp bits ...
?LOG(invalid, Pkt#diameter_packet.bin),
#diameter_packet{errors = Failed}
= P
= decode_avps(MsgName, Mod, Pkt, Avps),
P#diameter_packet{errors = [Bs | Failed]};
decode_avps('', Mod, Pkt, Avps) -> %% unknown message ...
?LOG(unknown, {Mod, Pkt#diameter_packet.header}),
Pkt#diameter_packet{avps = lists:reverse(Avps),
errors = [3001]}; %% DIAMETER_COMMAND_UNSUPPORTED
%% msg = undefined identifies this case.
decode_avps(MsgName, Mod, Pkt, Avps) -> %% ... or not
{Rec, As, Failed} = Mod:decode_avps(MsgName, Avps),
?LOGC([] /= Failed, failed, {Mod, Failed}),
Pkt#diameter_packet{msg = Rec,
errors = Failed,
avps = As}.
%%% ---------------------------------------------------------------------------
%%% # decode_header/1
%%% ---------------------------------------------------------------------------
decode_header(<<Version:8,
MsgLength:24,
CmdFlags:1/binary,
CmdCode:24,
ApplicationId:32,
HopByHopId:32,
EndToEndId:32,
_/bitstring>>) ->
<<R:1, P:1, E:1, T:1, _:4>>
= CmdFlags,
%% 3588 (ch 3) says that reserved bits MUST be set to 0 and ignored
%% by the receiver.
%% The RFC is quite unclear about the order of the bits in this
%% case. It writes
%%
%% 0 1 2 3 4 5 6 7
%% +-+-+-+-+-+-+-+-+
%% |R P E T r r r r|
%% +-+-+-+-+-+-+-+-+
%%
%% in defining these but the scale refers to the (big endian)
%% transmission order, first to last, not the bit order. That is,
%% R is the high order bit. It's odd that a standard reserves
%% low-order bit rather than high-order ones.
#diameter_header{version = Version,
length = MsgLength,
cmd_code = CmdCode,
application_id = ApplicationId,
hop_by_hop_id = HopByHopId,
end_to_end_id = EndToEndId,
is_request = 1 == R,
is_proxiable = 1 == P,
is_error = 1 == E,
is_retransmitted = 1 == T};
decode_header(_) ->
false.
%%% ---------------------------------------------------------------------------
%%% # sequence_numbers/1
%%% ---------------------------------------------------------------------------
%% The End-To-End identifier must be unique for at least 4 minutes. We
%% maintain a 24-bit wraparound counter, and add an 8-bit persistent
%% wraparound counter. The 8-bit counter is incremented each time the
%% system is restarted.
sequence_numbers({_,_} = T) ->
T;
sequence_numbers(#diameter_packet{bin = Bin})
when is_binary(Bin) ->
sequence_numbers(Bin);
sequence_numbers(#diameter_packet{header = #diameter_header{} = H}) ->
sequence_numbers(H);
sequence_numbers(#diameter_header{hop_by_hop_id = H,
end_to_end_id = E}) ->
{H,E};
sequence_numbers(<<_:12/binary, H:32, E:32, _/binary>>) ->
{H,E}.
%%% ---------------------------------------------------------------------------
%%% # hop_by_hop_id/2
%%% ---------------------------------------------------------------------------
hop_by_hop_id(Id, <<H:12/binary, _:32, T/binary>>) ->
<<H/binary, Id:32, T/binary>>.
%%% ---------------------------------------------------------------------------
%%% # msg_name/2
%%% ---------------------------------------------------------------------------
msg_name(Dict0, #diameter_header{application_id = ?APP_ID_COMMON,
cmd_code = C,
is_request = R}) ->
Dict0:msg_name(C,R);
msg_name(_, Hdr) ->
msg_id(Hdr).
%% Note that messages in different applications could have the same
%% name.
%%% ---------------------------------------------------------------------------
%%% # msg_id/1
%%% ---------------------------------------------------------------------------
msg_id(#diameter_packet{msg = [#diameter_header{} = Hdr | _]}) ->
msg_id(Hdr);
msg_id(#diameter_packet{header = #diameter_header{} = Hdr}) ->
msg_id(Hdr);
msg_id(#diameter_header{application_id = A,
cmd_code = C,
is_request = R}) ->
{A, C, if R -> 1; true -> 0 end};
msg_id(<<_:32, Rbit:1, _:7, CmdCode:24, ApplId:32, _/bitstring>>) ->
{ApplId, CmdCode, Rbit}.
%%% ---------------------------------------------------------------------------
%%% # collect_avps/1
%%% ---------------------------------------------------------------------------
%% Note that the returned list of AVP's is reversed relative to their
%% order in the binary. Note also that grouped avp's aren't unraveled,
%% only those at the top level.
collect_avps(#diameter_packet{bin = Bin}) ->
<<_:20/binary, Avps/bitstring>> = Bin,
collect_avps(Avps);
collect_avps(Bin) ->
collect_avps(Bin, 0, []).
collect_avps(<<>>, _, Acc) ->
Acc;
collect_avps(Bin, N, Acc) ->
try split_avp(Bin) of
{Rest, AVP} ->
collect_avps(Rest, N+1, [AVP#diameter_avp{index = N} | Acc])
catch
?FAILURE(_) ->
{Bin, Acc}
end.
%% 0 1 2 3
%% 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
%% +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
%% | AVP Code |
%% +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
%% |V M P r r r r r| AVP Length |
%% +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
%% | Vendor-ID (opt) |
%% +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
%% | Data ...
%% +-+-+-+-+-+-+-+-+
%% split_avp/1
split_avp(Bin) ->
8 =< size(Bin) orelse ?THROW(truncated_header),
<<Code:32, Flags:1/binary, Length:24, Rest/bitstring>>
= Bin,
DataSize = Length - 8, % size(Code+Flags+Length) = 8 octets
PadSize = (4 - (DataSize rem 4)) rem 4,
DataSize + PadSize =< size(Rest)
orelse ?THROW(truncated_data),
<<Data:DataSize/binary, _:PadSize/binary, R/bitstring>>
= Rest,
<<Vbit:1, Mbit:1, Pbit:1, _Reserved:5>>
= Flags,
0 == Vbit orelse 4 =< size(Data)
orelse ?THROW(truncated_vendor_id),
{Vid, D} = vid(Vbit, Data),
{R, #diameter_avp{code = Code,
vendor_id = Vid,
is_mandatory = 1 == Mbit,
need_encryption = 1 == Pbit,
data = D}}.
%% The RFC is a little misleading when stating that OctetString is
%% padded to a 32-bit boundary while other types align naturally. All
%% other types are already multiples of 32 bits so there's no need to
%% distinguish between types here. Any invalid lengths will result in
%% decode error in diameter_types.
vid(1, <<Vid:32, Data/bitstring>>) ->
{Vid, Data};
vid(0, Data) ->
{undefined, Data}.
%%% ---------------------------------------------------------------------------
%%% # pack_avp/1
%%% ---------------------------------------------------------------------------
%% The normal case here is data as an #diameter_avp{} list or an
%% iolist, which are the cases that generated codec modules use. The
%% other case is as a convenience in the relay case in which the
%% dictionary doesn't know about specific AVP's.
%% Grouped AVP whose components need packing ...
pack_avp(#diameter_avp{data = [#diameter_avp{} | _] = Avps} = A) ->
pack_avp(A#diameter_avp{data = encode_avps(Avps)});
%% ... data as a type/value tuple, possibly with header data, ...
pack_avp(#diameter_avp{data = {Type, Value}} = A)
when is_atom(Type) ->
pack_avp(A#diameter_avp{data = diameter_types:Type(encode, Value)});
pack_avp(#diameter_avp{data = {{_,_,_} = T, {Type, Value}}}) ->
pack_avp(T, iolist_to_binary(diameter_types:Type(encode, Value)));
pack_avp(#diameter_avp{data = {{_,_,_} = T, Bin}})
when is_binary(Bin) ->
pack_avp(T, Bin);
pack_avp(#diameter_avp{data = {Dict, Name, Value}} = A) ->
{Code, _Flags, Vid} = Hdr = Dict:avp_header(Name),
{Name, Type} = Dict:avp_name(Code, Vid),
pack_avp(A#diameter_avp{data = {Hdr, {Type, Value}}});
%% ... or as an iolist.
pack_avp(#diameter_avp{code = Code,
vendor_id = V,
is_mandatory = M,
need_encryption = P,
data = Data}) ->
Flags = lists:foldl(fun flag_avp/2, 0, [{V /= undefined, 2#10000000},
{M, 2#01000000},
{P, 2#00100000}]),
pack_avp({Code, Flags, V}, iolist_to_binary(Data)).
flag_avp({true, B}, F) ->
F bor B;
flag_avp({false, _}, F) ->
F.
%%% ---------------------------------------------------------------------------
%%% # pack_avp/2
%%% ---------------------------------------------------------------------------
pack_avp({Code, Flags, VendorId}, Bin)
when is_binary(Bin) ->
Sz = size(Bin),
pack_avp(Code, Flags, VendorId, Sz, pad(Sz rem 4, Bin)).
pad(0, Bin) ->
Bin;
pad(N, Bin) ->
P = 8*(4-N),
<<Bin/binary, 0:P>>.
%% Note that padding is not included in the length field as mandated by
%% the RFC.
%% pack_avp/5
%%
%% Prepend the vendor id as required.
pack_avp(Code, Flags, Vid, Sz, Bin)
when 0 == Flags band 2#10000000 ->
undefined = Vid, %% sanity check
pack_avp(Code, Flags, Sz, Bin);
pack_avp(Code, Flags, Vid, Sz, Bin) ->
pack_avp(Code, Flags, Sz+4, <<Vid:32, Bin/binary>>).
%% pack_avp/4
pack_avp(Code, Flags, Sz, Bin) ->
Length = Sz + 8,
<<Code:32, Flags:8, Length:24, Bin/binary>>.
