bts: Start a DL TBF if needed after establishment of an UL TBF

Currently an existing DL TBF can get lost in the process of
establishing an UL TBF via RACH. This can lead to stalled connections
until the network sends more LLC frames.

This commit adds a check for a non-empty LLC queue after the UL TBF
has been established to rcv_control_ack (GPRS_RLCMAC_UL_ASS_WAIT_ACK
path) to eventually establish a new DL TBF on the UL TBF's PACCH.

Sponsored-by: On-Waves ehf
4 files changed