Who generates answer on "Get Current Data Bearer Technology" (--wds-get-current-data-bearer-technology)? It seems to occur only with qmimux...

[Martin Maurer]

Hello,

when calling

sudo qmicli -v -p -d /dev/cdc-wdm0 
--wds-get-current-data-bearer-technology --client-cid=15 
--client-no-release-cid

multiple time (one after the other), I get sometimes

Radio Access Technology: 'none'

and other times

Radio Access Technology: 'lte'


I am using qmimux. It seems it happens only with qmimux (1 or 2 
established connections).

When using no qmimux the answer seems to be stable correct.


Here two answers of the error case with qmimux:

[22 Oct 2023, 17:17:13] [Debug] [/dev/cdc-wdm0] received generic 
response (translated)...
<<<<<< QMUX:
<<<<<<   length  = 31
<<<<<<   flags   = 0x80
<<<<<<   service = "wds"
<<<<<<   client  = 16
<<<<<< QMI:
<<<<<<   flags       = "response"
<<<<<<   transaction = 1
<<<<<<   tlv_length  = 19
<<<<<<   message     = "Get Current Data Bearer Technology" (0x0044)
<<<<<< TLV:
<<<<<<   type       = "Result" (0x02)
<<<<<<   length     = 4
<<<<<<   value      = 00:00:00:00
<<<<<<   translated = SUCCESS
<<<<<< TLV:
<<<<<<   type       = "Current" (0x01)
<<<<<<   length     = 9
<<<<<<   value      = 02:20:00:00:00:00:00:00:00
<<<<<<   translated = [ network_type = '3gpp' rat_mask = '32' so_mask = 
'0' ]

[/dev/cdc-wdm0] Data bearer technology (current):
               Network type: '3gpp'
    Radio Access Technology: 'lte'
[/dev/cdc-wdm0] Client ID not released:
         Service: 'wds'
             CID: '16'
[22 Oct 2023, 17:17:13] [Debug] [/dev/cdc-wdm0] releasing 'wds' client 
with flags 'none'...
[22 Oct 2023, 17:17:13] [Debug] [/dev/cdc-wdm0] unregistered 'wds' 
client with ID '16'
[22 Oct 2023, 17:17:13] [Debug] Client released
[22 Oct 2023, 17:17:13] [Debug] Closed


or


[22 Oct 2023, 17:17:15] [Debug] [/dev/cdc-wdm0] received generic 
response (translated)...
<<<<<< QMUX:
<<<<<<   length  = 31
<<<<<<   flags   = 0x80
<<<<<<   service = "wds"
<<<<<<   client  = 16
<<<<<< QMI:
<<<<<<   flags       = "response"
<<<<<<   transaction = 1
<<<<<<   tlv_length  = 19
<<<<<<   message     = "Get Current Data Bearer Technology" (0x0044)
<<<<<< TLV:
<<<<<<   type       = "Result" (0x02)
<<<<<<   length     = 4
<<<<<<   value      = 00:00:00:00
<<<<<<   translated = SUCCESS
<<<<<< TLV:
<<<<<<   type       = "Current" (0x01)
<<<<<<   length     = 9
<<<<<<   value      = 02:00:04:00:00:00:00:00:00
<<<<<<   translated = [ network_type = '3gpp' rat_mask = '1024' so_mask 
= '0' ]

[/dev/cdc-wdm0] Data bearer technology (current):
               Network type: '3gpp'
    Radio Access Technology: 'none'
[/dev/cdc-wdm0] Client ID not released:
         Service: 'wds'
             CID: '16'
[22 Oct 2023, 17:17:15] [Debug] [/dev/cdc-wdm0] releasing 'wds' client 
with flags 'none'...
[22 Oct 2023, 17:17:15] [Debug] [/dev/cdc-wdm0] unregistered 'wds' 
client with ID '16'
[22 Oct 2023, 17:17:15] [Debug] Client released
[22 Oct 2023, 17:17:15] [Debug] Closed


PS: For my understanding the length of the answer is 9 bytes. network 
type seems to be 1 byte (in the answer "value"). rat_mask 2 bytes, 
so_mask 1 or 2 bytes. What are the remaining fields? Unknown? Or some 
fill bytes because of a minimum length?

It is not due to connection being disconnected, because it toggles 
randomly between "lte" and "none".

Is this something libqmi generates? Or is such an answer directly coming 
from the used modem (in this case a Quectel RM520N-GL)

and therefore I must clarify with support of Quectel?

Has someone already seen something similar?

Best regards,

Martin