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Bug #5791
closedmobile: "DLLAPD NOTICE lapdm.c:769 (dl=0x62c000000ef0) EA bit 0 is not allowed in GSM"
Start date:
11/25/2022
Due date:
% Done:
100%
Resolution:
Spec Reference:
Description
This message is frequently seen when "talking" to an Osmocom based network.
DLLAPD NOTICE lapdm.c:769 (dl=0x62c000000ef0) EA bit 0 is not allowed in GSM DLLAPD NOTICE lapdm.c:546 (dl=0x62c000000ef0) sending MDL-ERROR-IND 12
mobile originated GSMTAP traces in Wireshark confirm this warning:
$ tshark -r /tmp/lapdm.pcap -Y "(lapdm.ea == 0)" 9 1.786785 127.0.0.1 → 127.0.10.1 LAPDm 81 S, func=RR, N(R)=0 10 2.258601 127.0.0.1 → 127.0.10.1 LAPDm 81 S, func=RR, N(R)=0 11 2.728325 127.0.0.1 → 127.0.10.1 LAPDm 81 S, func=RR, N(R)=0 $ tshark -r /tmp/lapdm.pcap -Y "(lapdm.ea == 0)" -V | less GSM TAP Header, ARFCN: 73 (Downlink), TS: 1, Channel: SDCCH/8 (0) Version: 2 Header Length: 16 bytes Payload Type: GSM Um (MS<->BTS) (1) Time Slot: 1 ..00 0000 0100 1001 = ARFCN: 73 .0.. .... .... .... = Uplink: 0 0... .... .... .... = PCS band indicator: 0 Signal Level: -47 dBm Signal/Noise Ratio: 0 dB GSM Frame Number: 1195166 Channel Type: SDCCH/8 (8) Antenna Number: 0 Sub-Slot: 0 Link Access Procedure, Channel Dm (LAPDm) Address Field: 0x0e .00. .... = LPD: Normal GSM (0) ...0 11.. = SAPI: SMS/SS (3) .... ..1. = C/R: 1 .... ...0 = EA: More octets (0) Control field: S, func=RR, N(R)=0 (0x01) 000. .... = N(R): 0 .... 00.. = Supervisory frame type: Receiver ready (0x0) .... ..01 = Frame type: Supervisory frame (0x1) Length Field: 0x03 0000 00.. = Length: 0 .... ..1. = M: More segments (1) .... ...1 = EL: Final octet (1)
Looks like the S, func=RR
frames are encoded incorrectly by the network side? SAPI: SMS/SS (3)
is also suspicious.
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