After reception of SABM, the network responds with UA and enters the
establised multiframe state. If UA is not received by mobile, the SABM
is transmitted again, and the network must respond with UA again, unless
it is from a different mobile.
Add LAPDm collision test (contention resolution on network side).
DATA REQ with a msgb_l3len(msg) == 0 message does not make any
sense, log an error and return immediately before attempting to
send an empty I frame in lapd_send_i.
If a sequence error is received, the N(R) variable must still be used to
acknowledge previously transmitted frames.
If there are two subsequent sequence errors received, ignore it. (Ignore
every second subsequent error.) This happens if our reply with the REJ is
too slow, so the remote gets a T200 timeout and sends another frame with
a sequence error. Test showed that replying with two subsequent REJ
messages could the remote L2 process to abort. Replying too slow shouldn't
happen, but may happen over serial link between BB and LAPD.
Written-by: Andreas.Eversberg <jolly@eversberg.eu>
Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
Instead of mixing together the GSM layer 1 interface and RSL interface
with the implementation of LAPD, the core function of LAPD is now
extracted from LAPDm. The core implementation is now in lapd_core.c
and lapd_core.h respectively.
The lapd_core.c implements exactly one datalink instance for one SAP.
The surrounding implementation "lapdm.c" codes/decodes the layer 2
headers and handles multiplexing and datalink instances, as well as
translates primitives from/to RSL layer.
lapd_core.c can now be used for other LAPD implementations. (ISDN/ABIS)
Holger Hans Peter Freyther
Sylvain Munaut