osmo-bts-trx/trx_if.c: introduce TRXD header version handling

It may be necessary to extend the message specific header with
more information. Since this is not a TLV-based protocol, we
need to include the header format version.

  +-----------------+---------------------------+
  | 7 6 5 4 3 2 1 0 | bit numbers (value range) |
  +-----------------+---------------------------+
  | X X X X . . . . | header version (0..15)    |
  +-----------------+---------------------------+
  | . . . . . X X X | TDMA TN (0..7)            |
  +-----------------+---------------------------+
  | . . . . X . . . | RESERVED (0)              |
  +-----------------+---------------------------+

Instead of prepending an additional byte, it was decided to use
4 MSB bits of the first octet, which used to be zero-initialized
due to the value range of TDMA TN (0..7). Therefore the current
header format has implicit version 0.

Otherwise Wireshark (or trx_sniff.py) would have to guess the
header version, or alternatively follow the control channel
looking for the version setting command.

This change introduces a new structure 'trx_ul_burst_ind', which
represents an Uplink burst and the corresponding meta info. The
purpose of this structure is to avoid overloading the existing
functions, such as trx_sched_ul_burst(), with more and more
arguments every time we bump the version.

On receipt of a TRXD message, trx_data_read_cb() now parses
the header version, and calls the corresponding dissector
functions, e.g. trx_data_handle_(hdr|burst)_v0().

Change-Id: I171c18229ca3e5cab70de0064a31e47c78602c0c
Related: OS#4006

1 files changed, 13 insertions, 13 deletions

diff --git a/src/common/scheduler.c b/src/common/scheduler.c
index 3f804a90..83779d79 100644
--- a/src/common/scheduler.c
+++ b/src/common/scheduler.c
@@ -1313,11 +1313,10 @@ static int trx_sched_calc_frame_loss(struct l1sched_trx *l1t,
 	return 0;
 }
 
-/* process uplink burst */
-int trx_sched_ul_burst(struct l1sched_trx *l1t, uint8_t tn, uint32_t fn,
-	sbit_t *bits, uint16_t nbits, int8_t rssi, int16_t toa256)
+/* Process an Uplink burst indication */
+int trx_sched_ul_burst(struct l1sched_trx *l1t, struct trx_ul_burst_ind *bi)
 {
-	struct l1sched_ts *l1ts = l1sched_trx_get_ts(l1t, tn);
+	struct l1sched_ts *l1ts = l1sched_trx_get_ts(l1t, bi->tn);
 	struct l1sched_chan_state *l1cs;
 	const struct trx_sched_frame *frame;
 	uint8_t offset, period, bid;
@@ -1329,7 +1328,7 @@ int trx_sched_ul_burst(struct l1sched_trx *l1t, uint8_t tn, uint32_t fn,
 
 	/* get frame from multiframe */
 	period = l1ts->mf_period;
-	offset = fn % period;
+	offset = bi->fn % period;
 	frame = l1ts->mf_frames + offset;
 
 	chan = frame->ul_chan;
@@ -1346,28 +1345,29 @@ int trx_sched_ul_burst(struct l1sched_trx *l1t, uint8_t tn, uint32_t fn,
 		return -EINVAL;
 
 	/* calculate how many TDMA frames were potentially lost */
-	trx_sched_calc_frame_loss(l1t, l1cs, tn, fn);
+	trx_sched_calc_frame_loss(l1t, l1cs, bi->tn, bi->fn);
 
 	/* update TDMA frame counters */
-	l1cs->last_tdma_fn = fn;
+	l1cs->last_tdma_fn = bi->fn;
 	l1cs->proc_tdma_fs++;
 
 	/* decrypt */
-	if (bits && l1cs->ul_encr_algo) {
+	if (bi->burst_len && l1cs->ul_encr_algo) {
 		ubit_t ks[114];
 		int i;
 
-		osmo_a5(l1cs->ul_encr_algo, l1cs->ul_encr_key, fn, NULL, ks);
+		osmo_a5(l1cs->ul_encr_algo, l1cs->ul_encr_key, bi->fn, NULL, ks);
 		for (i = 0; i < 57; i++) {
 			if (ks[i])
-				bits[i + 3] = - bits[i + 3];
+				bi->burst[i + 3] = - bi->burst[i + 3];
 			if (ks[i + 57])
-				bits[i + 88] = - bits[i + 88];
+				bi->burst[i + 88] = - bi->burst[i + 88];
 		}
 	}
 
-	/* put burst to function */
-	func(l1t, tn, fn, chan, bid, bits, nbits, rssi, toa256);
+	/* put burst to function
+	 * TODO: rather pass a pointer to trx_ul_burst_ind */
+	func(l1t, bi->tn, bi->fn, chan, bid, bi->burst, bi->burst_len, bi->rssi, bi->toa256);
 
 	return 0;
 }