as per legacy code, the NAS functions in nr_nas_msg.c were encoding
the header in the plain header contained in MM_msg
(e.g. plain -> mm_msg -> header in fgs_nas_message_t). The same
header was encoded in the mobility management message contained
in the same struct (e.g. plain -> mm_msg -> registration_request
-> protocoldiscriminator). As this was more complicated than
necessary, the goal of this commit is to simplify the code and
improve readability. Namely:
* Refactor MM_msg into fgmm_nas_message_plain_t to contain
(1) 5GMM Header
(2) 5GMM Payload union
* Use fgmm_nas_message_plain_t and fgmm_nas_msg_security_protected_t
in the 5GMM NAS procedures
* Remove NAS header IEs from 5GMM messages structs and use
the header in fgs_nas_message_plain_t.
This reduce also the repetitions of header members in each
of the 5GMM messages structs.
* Rename struct to distinguish between 5GMM and 5GSM
* Remove fgs_nas_message_t and nas_msg_header_t,
use directly basic 5GS struct definitions, simplify the code
* The callbacks in nr_nas_msg.c are now doing
(1) encode header with the common NAS lib
(2) encode contents with the 5GMM libs
* improve code readibility in the process
Guido Casati
63d7f26cfd