The first byte in data_ind->msgUnitParam.u8Buffer is not part of the GSM
frame, but something else, it is also skipped in the call to
pcu_rx_data_ind_pdtch().
This patch fixes GSM RLC/MAC UL packet decoding in wireshark, especially
ACK/NACK packets are now displayed correctly (amongst others).
In order to use this feature, sysmoBTS requires option "-M", otherwise
the traffic is forwarded through socket interface.
This is essential, if PCU runs on processor of sysmoBTS. The reaction
time and delay of PDTCH frames could heavily degrade proper packet flow.
Holger Hans Peter Freyther
Daniel Willmann