From 502189ba42469d3332bc0658caa2bd0de1e3fcb9 Mon Sep 17 00:00:00 2001 From: Anders Svensson Date: Mon, 24 Aug 2015 16:14:49 +0200 Subject: Add service_opt() strict_mbit There are differing opinions on whether or not reception of an arbitrary AVP setting the M-bit is an error. 1.3.4 of RFC 6733 says this about how an existing Diameter application may be modified: o The M-bit allows the sender to indicate to the receiver whether or not understanding the semantics of an AVP and its content is mandatory. If the M-bit is set by the sender and the receiver does not understand the AVP or the values carried within that AVP, then a failure is generated (see Section 7). It is the decision of the protocol designer when to develop a new Diameter application rather than extending Diameter in other ways. However, a new Diameter application MUST be created when one or more of the following criteria are met: M-bit Setting An AVP with the M-bit in the MUST column of the AVP flag table is added to an existing Command/Application. An AVP with the M-bit in the MAY column of the AVP flag table is added to an existing Command/Application. The point here is presumably interoperability: that the command grammar should specify explicitly what mandatory AVPs much be understood, and that anything more is an error. On the other hand, 3.2 says thus about command grammars: avp-name = avp-spec / "AVP" ; The string "AVP" stands for *any* arbitrary AVP ; Name, not otherwise listed in that Command Code ; definition. The inclusion of this string ; is recommended for all CCFs to allow for ; extensibility. This renders 1.3.4 pointless unless "*any* AVP" is qualified by "not setting the M-bit", since the sender can effectively violate 1.3.4 without this necessitating an error at the receiver. If clients add arbitrary AVPs setting the M-bit then request handling becomes more implementation-dependent. The current interpretation in diameter is strict: if a command grammar doesn't explicitly allow an AVP setting the M-bit then reception of such an AVP is regarded as an error. The strict_mbit option now allows this behaviour to be changed, false turning all responsibility for the M-bit over to the user. --- lib/diameter/include/diameter_gen.hrl | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'lib/diameter/include') diff --git a/lib/diameter/include/diameter_gen.hrl b/lib/diameter/include/diameter_gen.hrl index ac2126cdc5..39ccdc9873 100644 --- a/lib/diameter/include/diameter_gen.hrl +++ b/lib/diameter/include/diameter_gen.hrl @@ -30,7 +30,10 @@ %% Key to a value in the process dictionary that determines whether or %% not an unrecognized AVP setting the M-bit should be regarded as an -%% error or not. See is_strict/0. +%% error or not. See is_strict/0. This is only used to relax M-bit +%% interpretation inside Grouped AVPs not setting the M-bit. The +%% service_opt() strict_mbit can be used to disable the check +%% globally. -define(STRICT_KEY, strict). %% Key that says whether or not we should do a best-effort decode @@ -447,7 +450,8 @@ relax(_, _) -> false. is_strict() -> - false /= getr(?STRICT_KEY). + diameter_codec:getopt(strict_mbit) + andalso false /= getr(?STRICT_KEY). %% relax/1 %% -- cgit v1.2.3