Failure to register AdvertisementMonitor not propagated to D-Bus

[bojanpotocnik]

As described in hbldh/bleak#1136, if kernel does not support Advertising Monitor, the failure to Add Advertisement Patterns Monitor is not propagated.

Example using btmgmt, where the error is detected because MGMT command is actually executed:

➜  ~ btmgmt          
[mgmt]# version
Version 5.66
[mgmt]# revision 
MGMT Version 1, revision 14
[mgmt]# menu monitor 
...
[mgmt]# features 
Reading adv monitor features failed with status 0x01 (Unknown Command)

btmon --mgmt output:

@ MGMT Command: Read Advertisement Monitor Features (0x0051) plen 0
@ MGMT Event: Command Status (0x0002) plen 3
      Read Advertisement Monitor Features (0x0051)
        Status: Unknown Command (0x01)

However, when executing "equivalent" D-Bus call, no MGMT commands are invoked at all (btmon output empty)

➜  ~ dbus-send --system --dest=org.bluez --print-reply /org/bluez/hci0 org.freedesktop.DBus.Properties.Get string:org.bluez.AdvertisementMonitorManager1 string:SupportedFeatures
method return time=1669724095.627868 sender=:1.95589 -> destination=:1.95986 serial=307 reply_serial=2
   variant       array [
      ]

Note that empty array is returned also on kernel 5.14, where using advertising monitor actually works.

This is not the same as #203 (monitor can be used there via btmgmt), however it probably has the same problems of errors not propagating to D-Bus.

[Vudentz]

@bojanpotocnik Im surprised the interface even exists if the kernel doesn't support it as it is probably useless to have it if none of the commands would work, that said perhaps the controller don't actually support the MSFT command to enable it on 5.14?

[bojanpotocnik]

it is probably useless to have it if none of the commands would work

I agree, that would be even better way to solve it.

that said perhaps the controller don't actually support the MSFT command to enable it on 5.14?

I'm not sure what exactly you meant by this, but otherwise passive scanning on 5.14 works fine using the same BlueZ version.