[srsran-users] NAS Short MAC invalid issue

[J Giovatto]

Hi Folks

I ran into this case where if after a successful attach (rinti 0x46) the 
ue looses the link with the enb for 5 minute with a constant uplink ping 
(1pps) to the epc.

Upon re-establish link (rinti 0x47) the ue does attach but con no longer 
complete the ping. I believe that uplink traffic is required to cause 
this, w/o traffic

I have not seen to behavior.

epc.log

18:29:12.220268 [S1AP   ] [I] Initial UE message: NAS Message Type Unknown
18:29:12.220270 [S1AP   ] [I] Received Initial UE message -- Service Request
18:29:12.220273 [NAS    ] [I] Service request -- S-TMSI 0x1f9da66e
18:29:12.220275 [NAS    ] [I] Service request -- eNB UE S1AP Id 2
18:29:12.220277 [S1AP   ] [D] Found IMSI 001011000000001 from M-TMSI 
0x1f9da66e
18:29:12.220374 [NAS    ] [W] Short integrity check failure. Local: 
count=29, [a9 78 63 5c], Received: count=29, [ff d2]
18:29:12.220376 [NAS    ] [I] Service Request -- Short MAC invalid
18:29:12.220378 [S1AP   ] [D] Saved UE context corresponding to MME UE 
S1AP Id 2
18:29:12.220379 [S1AP   ] [D] Added UE with MME-UE S1AP Id 2 to eNB with 
association 499
18:29:12.220381 [S1AP   ] [D] Sending message to eNB with SCTP 
association 499. MME UE S1AP ID 2, eNB UE S1AP ID 2
18:29:12.220734 [S1AP   ] [D] Transmitting S1AP PDU. eNB SCTP 
association Id: 499
18:29:12.221013 [NAS    ] [W] Service Request -- Short MAC invalid. 
Sending service reject.
18:29:12.221014 [NAS    ] [I] Service Reject -- eNB_UE_S1AP_ID 2 
MME_UE_S1AP_ID 2.
18:29:12.221137 [S1AP   ] [D] Waiting for S1-MME or S11 Message

enb.log

8:29:12.199121 [S1AP   ] [I] Tx S1AP SDU, InitialUEMessage, rnti=0x47
     0000: 00 0c 40 37 00 00 06 00 08 00 02 00 02 00 1a 00
     0010: 05 04 c7 1d ff d2 00 43 00 06 00 00 f1 10 00 07
18:29:12.200056 [MAC    ] [I] [ 3030] SCHED: DL tx rnti=0x47, cc=0, 
pid=0, mask=0x1000, dci=(3, 0), n_rtx=0, cfi=2, tbs=7, buffer=7/0, 
tti_tx_dl=3034
18:29:12.200065 [RLC    ] [I] Tx status PDU - SRB1: ACK_SN = 1, N_nack = 0
18:29:12.200070 [MAC    ] [I] [ 3030] 0x47 DL LCID=1 len=2
18:29:12.208086 [MAC    ] [I] [ 3038] SCHED: DL adaptive link: 
rnti=0x47, cqi=5, last_mcs=1, cqi_offset=0.002000
18:29:12.221162 [S1AP   ] [I] Rx S1AP SDU - DownlinkNASTransport
     0000: 00 0b 40 1c 00 00 03 00 00 00 02 00 02 00 08 00
     0010: 02 00 02 00 1a 00 09 08 07 4e 09 5b e0 5f 01 00
18:29:12.221164 [S1AP   ] [I] Checking UE S1 logical connection. eNB UE 
S1AP ID=2, MME UE S1AP ID=2
18:29:12.221177 [RRC    ] [I] Tx SRB1 PDU, rnti=0x47 - 
dlInformationTransfer (11 B)
     0000: 08 00 40 3a 70 4a df 02 f8 08 00
18:29:12.221184 [PDCP   ] [I] TX SRB1 PDU, SN=0, integrity=none, 
encryption=none
     0000: 00 08 00 40 3a 70 4a df 02 f8 08 00 00 00 00 00
18:29:12.221186 [RLC    ] [I] SRB1: Tx SDU (16 B, PDCP_SN=0 
tx_sdu_queue_len=1)
     0000: 00 08 00 40 3a 70 4a df 02 f8 08 00 00 00 00 00
18:29:12.226058 [MAC    ] [I] [ 3056] SCHED: DL tx rnti=0x47, cc=0, 
pid=0, mask=0x1000, dci=(0, 2), n_rtx=0, cfi=1, tbs=28, buffer=23/0, 
tti_tx_dl=3060
18:29:12.226074 [RLC    ] [I] SRB1: Tx PDU SN=0 (18 B)
     0000: a0 00 00 08 00 40 3a 70 4a df 02 f8 08 00 00 00
     0010: 00 00
18:29:12.226083 [MAC    ] [I] [ 3056] 0x47 DL LCID=1 len=18


ue.log

18:29:12.230272 [RRC    ] [I] SRB1 - Rx dlInformationTransfer (11 B)
18:29:12.230273 [NAS    ] [I] DL SRB1 PDU
     0000: 07 4e 09 5b e0 5f 01 00
18:29:12.230274 [NAS    ] [I] DL SRB1 Decrypted PDU
     0000: 07 4e 09 5b e0 5f 01 00
18:29:12.230279 [NAS    ] [I] Received service reject with EMM cause=0x9 
and t3446=0

Maybe this is related to issue #960 ?

Thanks

Joe

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