Relay MAC commands sent as a response to a relay forward request are ignored

[adriansmares]

When LBM is compiled with relay RX support, LBM will ignore relay MAC commands (FPort 0) which are sent as a response to a uplink forwarding request (FPort 226). This happens because the following part of the MAC command parser checks the TX port instead of the RX port:

SWL2001/smtc_modem_core/lr1mac/src/lr1_stack_mac_layer.c

Lines 1424 to 1440 in c4f386a

	#if defined( RELAY_RX )
	default: {
	if( ( lr1_mac->tx_fport_present == true ) && ( lr1_mac->tx_fport == FPORT_RELAY ) )
	{
	lr1_mac->nwk_payload_size = 0; // Don't process data on FPORT 226 as MAC command
	}
	else
	{
	const bool mac_is_known = relay_rx_mac_parser( lr1_mac );
	if( mac_is_known == false )
	{
	lr1_mac->nwk_payload_size = 0;
	SMTC_MODEM_HAL_TRACE_PRINTF( " Unknown mac command %02x\n", cmd_identifier );
	}
	}
	}
	break;

I think this is a mistake, as non-relay MAC commands are processed, but relay MAC commands themselves cannot be sent as a response to a relay forwarding request. A possible fixup may be to check the RX metadata instead:

if( ( lr1_mac->rx_down_data.rx_metadata.rx_fport_present == true ) && ( lr1_mac->rx_down_data.rx_metadata.rx_fport == FPORT_RELAY ) )

[lbm-team]

Hello @adriansmares,

Thanks for the catch!
It will be fixed in the next release.
In the meantime, your proposal is valid.

[lbm-team]

Hello,

This issue was solved in the release v4.4.0-feature-relay.
I will let you close the issue if the fix is ok for you.

[adriansmares]

The fix looks good to me and I cannot reproduce this anymore in v4.4.0-feature-relay 👍 .