Osmocom E1 recorder
(C) 2016 by Harald Welte <laforge@gnumonks.org>

The idea of this program is to be able to passively record E1/T1 based
communications for purposes of data analysis.

Recording of a single E1 link always requires two E1 interface cards,
one for each direction.

Recording can be performed either
* passively, using a E1 Tap aapter
* asa proxy / man-in-the-middle

All timeslots will be opened in "raw" mode, making sure the recording
will work wheter or not there is HLDC-based signalling (MTP or LAPD),
PCM voice, TRAU frames or anything else on the line.

Recording will be done on a per-timeslot basis, dumping the raw bytes
read for this timeslot into a file.

New files are started regularly, after reaching a pre-determined file
size limit.  File names contain RTC time stamping and timeslot number.

Later possible extensions could include automatic detection of the
payload and a more intelligent storage format (e.g. in case of HDLC
bsaed signalling).