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+%%
+%% %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_session).
+
+-export([sequence/0,
+ session_id/1,
+ origin_state_id/0]).
+
+%% towards diameter_sup
+-export([init/0]).
+
+-include("diameter_types.hrl").
+
+-define(INT64, 16#FFFFFFFFFFFFFFFF).
+-define(INT32, 16#FFFFFFFF).
+
+%% ---------------------------------------------------------------------------
+%% # sequence/0
+%%
+%% Output: 32-bit
+%% ---------------------------------------------------------------------------
+
+%% 3588, 3:
+%%
+%% Hop-by-Hop Identifier
+%% The Hop-by-Hop Identifier is an unsigned 32-bit integer field (in
+%% network byte order) and aids in matching requests and replies.
+%% The sender MUST ensure that the Hop-by-Hop identifier in a request
+%% is unique on a given connection at any given time, and MAY attempt
+%% to ensure that the number is unique across reboots. The sender of
+%% an Answer message MUST ensure that the Hop-by-Hop Identifier field
+%% contains the same value that was found in the corresponding
+%% request. The Hop-by-Hop identifier is normally a monotonically
+%% increasing number, whose start value was randomly generated. An
+%% answer message that is received with an unknown Hop-by-Hop
+%% Identifier MUST be discarded.
+%%
+%% End-to-End Identifier
+%% The End-to-End Identifier is an unsigned 32-bit integer field (in
+%% network byte order) and is used to detect duplicate messages.
+%% Upon reboot implementations MAY set the high order 12 bits to
+%% contain the low order 12 bits of current time, and the low order
+%% 20 bits to a random value. Senders of request messages MUST
+%% insert a unique identifier on each message. The identifier MUST
+%% remain locally unique for a period of at least 4 minutes, even
+%% across reboots. The originator of an Answer message MUST ensure
+%% that the End-to-End Identifier field contains the same value that
+%% was found in the corresponding request. The End-to-End Identifier
+%% MUST NOT be modified by Diameter agents of any kind. The
+%% combination of the Origin-Host (see Section 6.3) and this field is
+%% used to detect duplicates. Duplicate requests SHOULD cause the
+%% same answer to be transmitted (modulo the hop-by-hop Identifier
+%% field and any routing AVPs that may be present), and MUST NOT
+%% affect any state that was set when the original request was
+%% processed. Duplicate answer messages that are to be locally
+%% consumed (see Section 6.2) SHOULD be silently discarded.
+
+-spec sequence()
+ -> 'Unsigned32'().
+
+sequence() ->
+ Instr = {_Pos = 2, _Incr = 1, _Threshold = ?INT32, _SetVal = 0},
+ ets:update_counter(diameter_sequence, sequence, Instr).
+
+%% ---------------------------------------------------------------------------
+%% # origin_state_id/0
+%% ---------------------------------------------------------------------------
+
+%% 3588, 8.16:
+%%
+%% The Origin-State-Id AVP (AVP Code 278), of type Unsigned32, is a
+%% monotonically increasing value that is advanced whenever a Diameter
+%% entity restarts with loss of previous state, for example upon reboot.
+%% Origin-State-Id MAY be included in any Diameter message, including
+%% CER.
+%%
+%% A Diameter entity issuing this AVP MUST create a higher value for
+%% this AVP each time its state is reset. A Diameter entity MAY set
+%% Origin-State-Id to the time of startup, or it MAY use an incrementing
+%% counter retained in non-volatile memory across restarts.
+
+-spec origin_state_id()
+ -> 'Unsigned32'().
+
+origin_state_id() ->
+ ets:lookup_element(diameter_sequence, origin_state_id, 2).
+
+%% ---------------------------------------------------------------------------
+%% # session_id/1
+%% ---------------------------------------------------------------------------
+
+%% 3588, 8.8:
+%%
+%% The Session-Id MUST begin with the sender's identity encoded in the
+%% DiameterIdentity type (see Section 4.4). The remainder of the
+%% Session-Id is delimited by a ";" character, and MAY be any sequence
+%% that the client can guarantee to be eternally unique; however, the
+%% following format is recommended, (square brackets [] indicate an
+%% optional element):
+%%
+%% <DiameterIdentity>;<high 32 bits>;<low 32 bits>[;<optional value>]
+%%
+%% <high 32 bits> and <low 32 bits> are decimal representations of the
+%% high and low 32 bits of a monotonically increasing 64-bit value. The
+%% 64-bit value is rendered in two part to simplify formatting by 32-bit
+%% processors. At startup, the high 32 bits of the 64-bit value MAY be
+%% initialized to the time, and the low 32 bits MAY be initialized to
+%% zero. This will for practical purposes eliminate the possibility of
+%% overlapping Session-Ids after a reboot, assuming the reboot process
+%% takes longer than a second. Alternatively, an implementation MAY
+%% keep track of the increasing value in non-volatile memory.
+%%
+%% <optional value> is implementation specific but may include a modem's
+%% device Id, a layer 2 address, timestamp, etc.
+
+-spec session_id('DiameterIdentity'())
+ -> 'OctetString'().
+%% Note that Session-Id has type UTF8String and that any OctetString
+%% is a UTF8String.
+
+session_id(Host) ->
+ Instr = {_Pos = 2, _Incr = 1, _Threshold = ?INT64, _Set = 0},
+ N = ets:update_counter(diameter_sequence, session_base, Instr),
+ Hi = N bsr 32,
+ Lo = N band ?INT32,
+ [Host, ";", integer_to_list(Hi),
+ ";", integer_to_list(Lo),
+ ";", atom_to_list(node())].
+
+%% ---------------------------------------------------------------------------
+%% # init/0
+%% ---------------------------------------------------------------------------
+
+init() ->
+ Now = now(),
+ random:seed(Now),
+ Time = time32(Now),
+ Seq = (?INT32 band (Time bsl 20)) bor (random:uniform(1 bsl 20) - 1),
+ ets:insert(diameter_sequence, [{origin_state_id, Time},
+ {session_base, Time bsl 32},
+ {sequence, Seq}]),
+ Time.
+
+%% ---------------------------------------------------------
+%% INTERNAL FUNCTIONS
+%% ---------------------------------------------------------
+
+%% The minimum value represented by a Time value. (See diameter_types.)
+%% 32 bits extends to 2104.
+-define(TIME0, 62105714048). %% {{1968,1,20},{3,14,8}}
+
+time32(Now) ->
+ Time = calendar:now_to_universal_time(Now),
+ Diff = calendar:datetime_to_gregorian_seconds(Time) - ?TIME0,
+ Diff band ?INT32.