Missing struct - O-RAN E2SM-RC

[japm48]

Hi,

First of all: thanks for the amazing work on this crate.

I'm trying to compile the O-RAN E2SM-RC spec using rs-asn1c, but unfortunately I'm missing some crucial sequences, like E2SM-RC-RANFunctionDefinition.

Not sure how to debug this.
Is there a possible workaround? (e.g. editing the ASN file or applying a patch).

I see a bunch of these warnings, probably related:

asn1_compiler::generator::asn::types::constructed::seq] Fields for some sequence additions may not be generated!

I have also tried with E2SM-KPM, and while it prints that warning, I'm not missing the equivalent field.

Log: rs-asn1c.log

ASN.1 sources:
E2SM-common-v04.asn.txt
E2SM-RC-v04.asn.txt

Command: rs-asn1c -d -d --codec aper --module rc.rs -- E2SM-common-v04.asn.txt E2SM-RC-v04.asn.txt

[gabhijit]

Hi @japm48,

Thanks for reporting the issue. One thing I didn't quite get is - What do you mean by "Missing definition of E2SM-RC-RANFunctionDefinition?

Does that mean that the structure is not getting generated or some fields in the structure are missing. The latter could be happening due to - the sequence addition fields - I took a quick look at the ASN file you sent -

-- **************************************************************
-- RAN Function Definition IEs
-- **************************************************************

E2SM-RC-RANFunctionDefinition ::= SEQUENCE{
	ranFunction-Name						RANfunction-Name,
	ranFunctionDefinition-EventTrigger		RANFunctionDefinition-EventTrigger			OPTIONAL,
	ranFunctionDefinition-Report			RANFunctionDefinition-Report				OPTIONAL,
	ranFunctionDefinition-Insert			RANFunctionDefinition-Insert				OPTIONAL,
	ranFunctionDefinition-Control			RANFunctionDefinition-Control				OPTIONAL,
	ranFunctionDefinition-Policy			RANFunctionDefinition-Policy				OPTIONAL,
	...,
	ranFunctionDefinition-Query				RANFunctionDefinition-Query					OPTIONAL
}

The optional ranFunctionDefinition-Query above is a sequence addition parameter, which are not supported, so only that field is missing from the structure or entire structure is not getting generated?

I started with some work on that but it's not yet quite done.

[japm48]

Thanks for the quick reply.

The issue is indeed that the whole struct is missing. After some debugging I found out that the real culprit is recursive structs.
In particular: the sequence RANParameter-Definition optionally includes itself (via RANParameter-Definition-Choice-LIST-Item or RANParameter-Definition-Choice-LIST-Item).

After removing the offending lines, RANParameter-Definition appears and also the original E2SM-RC-RANFunctionDefinition.
Now, I'm not sure if removing these optional fields the binary representation (using APER) is going to change.

E2SM-RC-v04_patched.diff.txt
E2SM-RC-v04_patched.asn.txt

[japm48]

Mmh, still with the patch it does not decode correctly.
I also tried replace the type by BOOLEAN OPTIONAL instead of removing the field, with the same results.
Not sure if it is because of my workaround and/or related to #133.
When I have time I will post an example from a .pcap capture.

[gabhijit]

Mmh, still with the patch it does not decode correctly. I also tried replace the type by BOOLEAN OPTIONAL instead of removing the field, with the same results. Not sure if it is because of my workaround and/or related to #133. When I have time I will post an example from a .pcap capture.

In general in ASN.1 codecs are closely tied to the structure definitions, so editing the structures will not help.

There appears to be an issue with the compiler - When such self referencing structures are not properly supported, the compilation should error out rather than generating wrong code and then will also look at how to work with these self referencing structures.

Will keep you posted - In the meanwhile any more debugging info with actual data would definitely help.

[gabhijit]

@japm48 :

I just tried the command you have used to generate the output Rust module and it indeed appears that there are a few structures missing from the generated module (rc.rs). Will need to look at what exactly is the problem.