[srsran-users] Feature request - Enhance the protocol configuration options (PCO) support (PDN Connectivity Request)

[Keith E. Fleming]

Greetings fellow users of srsRAN!!!!! I have been doing a lot of testing lately with an older (LG K7, 2018) and newer (IPhone 12, 2022) handsets, and have a feature request

Issue Description

When the LG makes a PDN connectivity request, under "Protocol Configuration Options" it includes these reasonable options:

Internet Protocol Control Protocol (0x8021)
DNS Server IP address (0x000d)
P-CSCF IPv4 address (0x000c)
IP address allocation via NAS signalling (0x000a)
MS Support of network requested bearer control (0x0005)
IPv4 link MTU (0x0010)

When the IPhone 12 sends the same request, we see these PCO:

Internet Protocol Control Protocol (0x8021)
DNS Server IP address (0x000d)
IP address allocation via NAS signalling (0x000a)
MS Support of network requested bearer control (0x0005)
IPv4 link MTU (0x0010)
MS support of local address in TFT indicator (0x0011)
PDU session ID (0x001a)
OSI network layer (0x0023)
Unknown (0x0024)

So the IPhone didn't ask for a P-CSCF address (I probably just didn't have VoLTE turned on when I made the test) but the PDN is rejected due to one or more of the last four options above that the LG does not ask for. My version of Wireshark does not even know how to interpret that last one

Setup Details

Centos 8, Intel i5-7600k, Ettus B200, LG K7 and IPhone 12 handsets, "real" USIM with known IMSI,Ki,OPc, UHD version 3.15.0, external GPSDO

Expected Behavior

I would like for the IPhone's PDN connectivity request to succeed even if that means telling the handset what it wants to hear :)

Actual Behaviour

Nothing in the logs (srsEPC / srsENB, both set to "debug"), but in the IPhone wireshark trace, one sees the PDN conn reject with ESM cause "service option not supported"

Steps to reproduce the problem

Unlocked IPhone 12, IMSI/Ki/OPc in srsEPC user_db.csv, make the IPhone discover the srsENB network, do something Internet related to force a data session (although the IPhone probably will already be trying to do this). The data session will fail. A Wireshark trace capturing port 36412 will show the S1AP messaging.

Additional Information
Thank you in advance!
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