During code review, it was indicated that some TLV protocols that we
will likely deal with in the near future also employ an I, and instance
value of a tag. Add TLIV support.
A usage example for a manually implemented TLIV structure is found in
tests/libosmo-gtlv/gtlv_test.c.
A usage example for a generated TLIV protocol is found in
tests/libosmo-gtlv/test_tliv/.
Related: SYS#5599
Change-Id: I0a076e54dfba6038cc779cb7c8f3967d212226aa
Defining a protocol of message types with lists of IEs bears a lot of
repetitive, copy-paste-error-prone writing out of data structures.
Add a third layer to libosmo-gtlv, which allows helpful code generation.
By non-repetitive data structures that briefly describe the protocol's
messages and IEs, generate possibly repetitive IE list arrays and
decoded-struct definitions automatically, avoiding grunt work errors.
I tried C macros for this at first, but it became too convoluted.
Generating C code that can be read and grepped makes things easier.
A usage example is found in tests/libosmo-gtlv/test_gtlv_gen/.
Related: SYS#5599
Change-Id: Ifb3ea54d2797ce060b95834aa117725ec2d6c4cf
Add osmo_gtlv_coding: describe the value part of a TLV (decode and
encode), describe a struct with its members, and get/put readily decoded
structs from/to a raw PDU, directly.
With osmo_gtlv_coding defined for a protocol's tags, we only deal with
encoded PDUs or fully decoded C structs, no TLV related
re-implementations clutter up the message handling code.
A usage example is given in gtlv_dec_enc_test. The first real use will be
the PFCP protocol in osmo-upf.git.
With osmo_gtlv_coding, there still is a lot of monkey work involved in
describing the decoded structs. A subsequent patch adds a generator for
osmo_gtlv_coding and message structs from tag value lists.
Related: SYS#5599
Change-Id: I65de793105882a452124ee58adb0e58469e6e796
An all new TLV parser supporting:
- Any size of T and L (determined by callback function),
- "Grouped IEs", so that an IE payload is a nested IE structure,
- optional/mandatory/multi-occurence IEs,
- decoding unordered tags (or enforcing strict order).
Will be used for PFCP message decoding and encoding, a T16L16V protocol
which requires above features.
Upcoming patches add
- translating PDUs to plain C structs and vice versa
- TLV generator to reduce repetition a in protocol definition
- TLIV capability
Previously, the way we deal with TLVs causes a lot of code
re-implementation: the TL decoding is taken care of by the API, but for
encoding, we essentially re-implement each protocol and each encoded
message in the individual programs. This API is an improvement in that
we only once implement the TL coding (or just use osmo_t8l8v_cfg /
osmo_t16l16v_cfg), get symmetric de- and encoding of the TL, and only
need to deal with the value part of each IE.
The common pattern of
- store TL preliminarily,
- write V data and
- update L after V is complete
is conveniently done by osmo_gtlv_put_update_tl().
Related: SYS#5599
Change-Id: Ib0fd00d9f288ffe13b7e67701f3e47073587404a
Neels Hofmeyr