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Bug #6124
closedFeature #5502: MS-side LLC implementation
LLC Dummy frames received from osmo-pcu dropped due to invalid FCS
Start date:
07/31/2023
Due date:
% Done:
100%
Resolution:
Spec Reference:
Description
I usually get this warning when receiving LLC dummy fames:
20230731162447732 DLLC INFO llc_prim.c:199 Rx from lower layers: GRR-UNITDATA.indication
20230731162447732 DLLC DEBUG llc_grr.c:97 Rx GRR-UNITDATA.indication: SAPI=3 (SNDCP3), UI func=UI C/R=1 PM=1 E=0 IP=0 N(U)=0 FCS=2b2b2b
20230731162447732 DLLC NOTICE llc.c:847 LLE(ca7cb1c3/db2e1be6,SNDCP3){ASSIGNED_ADM} Dropping frame with invalid FCS 0x2b2b2b vs exp 0x561485: 43 c0 01 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
That LLC-PDU matches the llc dummy frame:
static const uint8_t llc_dummy_command[] = {
0x43, 0xc0, 0x01, 0x2b, 0x2b, 0x2b
};
Need to find out whether it's a bug in osmo-pcu or in libosmo-gprs at the MS side.
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