[layer23] Added (incomplete) ASSIGNMENT COMMAND handling

This commit features handling of ASSIGNMENT COMMAND. Currently only channel
descriptions "after time" are processed, which is mostly the case.
The ASSIGNMENT COMMAND is essential, because public networks assign an
SDCCH4/8 before actually assigning a TCH.

src/host/layer23/include/osmocom/bb/common/osmocom_data.h

@@ -27,7 +27,9 @@ struct osmol2_entity {
 
 /* RX measurement statistics */
 struct rx_meas_stat {
+	uint32_t last_fn;
 	uint32_t frames;
+	uint32_t snr;
 	uint32_t berr;
 	uint32_t rxlev;
 };

src/host/layer23/include/osmocom/bb/mobile/gsm48_rr.h

@@ -69,9 +69,16 @@ struct gsm48_rr_cd {
 	uint8_t			hsn;
 	uint8_t			chan_nr; /* type, slot, sub slot */
 	uint8_t			link_id;
-	uint8_t			ta; /* timing advance */
+	uint8_t			ind_tx_power; /* last indicated power */
+	uint8_t			ind_ta; /* last indicated ta */
 	uint8_t			mob_alloc_lv[9]; /* len + up to 64 bits */
-	uint8_t			start_t1, start_t2, start_t3; /* start. time */
+	uint8_t			freq_list_lv[131]; /* len + 130 octets */
+	uint8_t			freq_seq_lv[10]; /* len + 9 octets */
+	uint8_t			cell_desc_lv[17]; /* len + 16 octets */
+	uint8_t			start; /* start time available */
+	struct gsm_time		start_tm; /* start time */
+	uint8_t			mode; /* mode of channel */
+	uint8_t			cipher; /* ciphering of channel */
 };
 
 /* measurements */
@@ -146,12 +153,12 @@ struct gsm48_rrlayer {
 	uint8_t			hando_susp_state;
 	uint8_t			assign_susp_state;
 	uint8_t			resume_last_state;
-	struct gsm48_rr_cd	cd_last;
+	struct gsm48_rr_cd	cd_last; /* store last cd in case of failure */
+	struct gsm48_rr_cd	cd_before; /* before start time */
+	struct gsm48_rr_cd	cd_after; /* after start time */
 
 	/* measurements */
 	struct gsm48_rr_meas	meas;
-	uint8_t			ind_tx_power; /* last indicated power */
-	uint8_t			ind_ta; /* last indicated ta */
 
 	/* BA range */
 	uint8_t			ba_ranges;

src/host/layer23/src/common/l1ctl.c

@@ -149,7 +149,9 @@ static int rx_ph_data_ind(struct osmocom_ms *ms, struct msgb *msg)
 		rsl_chan_nr_str(dl->chan_nr), tm.t1, tm.t2, tm.t3,
 		hexdump(ccch->data, sizeof(ccch->data)));
 
+	meas->last_fn = ntohl(dl->frame_nr);
 	meas->frames++;
+	meas->snr += dl->snr;
 	meas->berr += dl->num_biterr;
 	meas->rxlev += dl->rx_level;