lchan activation: add explicit encryption info to activation

For intra-BSC handover, the previous encryption is copied from the old lchan,
which of course is not available during inter-BSC handover.  Hence the lchan
activation info needs to include an explicit encryption information, and we
must not rely on the presence of the previous lchan to copy encryption
information from.

Add struct lchan_activate_info.encr to allow passing encryption info through
lchan_activate() without requiring a previous struct gsm_lchan to be present.

Instead of copying from the old lchan, always copy encryption info to
lchan_activate_info, and during activation, just before sending the Channel
Activation, copy the lchan_activate_info.encr to the new lchan.

This prepares for upcoming I5b269f50bd2092516bfdf87746196983d3ac49d1 which
obtains the encryption information from an intra-BSC-incoming Handover Request
message.

Related: OS#3842
Related: I5b269f50bd2092516bfdf87746196983d3ac49d1
Change-Id: Ib3d259a5711add65ab7298bfa3977855a17a1642

4 files changed, 10 insertions, 10 deletions

diff --git a/include/osmocom/bsc/gsm_data.h b/include/osmocom/bsc/gsm_data.h
index 47ca5e839..ba28a6b1c 100644
--- a/include/osmocom/bsc/gsm_data.h
+++ b/include/osmocom/bsc/gsm_data.h
@@ -528,6 +528,7 @@ struct lchan_activate_info {
 	/* This always is for a specific lchan, so its lchan->type indicates full or half rate.
 	 * When a dyn TS was selected, the lchan->type has been set to the desired rate. */
 	enum gsm48_chan_mode chan_mode;
+	struct gsm_encr encr;
 	/* AMR config */
 	uint16_t s15_s0;
 	bool requires_voice_stream;
diff --git a/src/osmo-bsc/assignment_fsm.c b/src/osmo-bsc/assignment_fsm.c
index c17b55509..9c0c40028 100644
--- a/src/osmo-bsc/assignment_fsm.c
+++ b/src/osmo-bsc/assignment_fsm.c
@@ -484,6 +484,7 @@ void assignment_fsm_start(struct gsm_subscriber_connection *conn, struct gsm_bts
 		.activ_for = FOR_ASSIGNMENT,
 		.for_conn = conn,
 		.chan_mode = conn->lchan->ch_mode_rate.chan_mode,
+		.encr = conn->lchan->encr,
 		.s15_s0 = conn->lchan->ch_mode_rate.s15_s0,
 		.requires_voice_stream = conn->assignment.requires_voice_stream,
 		.msc_assigned_cic = req->msc_assigned_cic,
diff --git a/src/osmo-bsc/handover_fsm.c b/src/osmo-bsc/handover_fsm.c
index a3d25d629..9c86b7090 100644
--- a/src/osmo-bsc/handover_fsm.c
+++ b/src/osmo-bsc/handover_fsm.c
@@ -358,6 +358,7 @@ static void handover_start_intra_bsc(struct gsm_subscriber_connection *conn)
 		.activ_for = FOR_HANDOVER,
 		.for_conn = conn,
 		.chan_mode = conn->lchan->tch_mode,
+		.encr = conn->lchan->encr,
 		.requires_voice_stream = conn->lchan->mgw_endpoint_ci_bts ? true : false,
 		.msc_assigned_cic = conn->ho.inter_bsc_in.msc_assigned_cic,
 		.re_use_mgw_endpoint_from_lchan = conn->lchan,
diff --git a/src/osmo-bsc/lchan_fsm.c b/src/osmo-bsc/lchan_fsm.c
index 2b7dc9753..7af2ea01c 100644
--- a/src/osmo-bsc/lchan_fsm.c
+++ b/src/osmo-bsc/lchan_fsm.c
@@ -518,14 +518,6 @@ static void lchan_fsm_wait_ts_ready_onenter(struct osmo_fsm_inst *fi, uint32_t p
 
 	lchan->conn = info->for_conn;
 
-	if (old_lchan)
-		lchan->encr = old_lchan->encr;
-	else {
-		lchan->encr = (struct gsm_encr){
-			.alg_id = RSL_ENC_ALG_A5(0),	/* no encryption */
-		};
-	}
-
 	/* If there is a previous lchan, and the new lchan is on the same cell as previous one,
 	 * take over power and TA values. Otherwise, use max power and zero TA. */
 	if (old_lchan && old_lchan->ts->trx->bts == bts) {
@@ -585,14 +577,17 @@ static void lchan_fsm_wait_ts_ready_onenter(struct osmo_fsm_inst *fi, uint32_t p
 	use_mgwep_ci = lchan_use_mgw_endpoint_ci_bts(lchan);
 
 	LOG_LCHAN(lchan, LOGL_INFO,
-		  "Activation requested: %s voice=%s MGW-ci=%s type=%s tch-mode=%s\n",
+		  "Activation requested: %s voice=%s MGW-ci=%s type=%s tch-mode=%s encr-alg=A5/%u ck=%s\n",
 		  lchan_activate_mode_name(lchan->activate.info.activ_for),
 		  lchan->activate.info.requires_voice_stream ? "yes" : "no",
 		  lchan->activate.info.requires_voice_stream ?
 			(use_mgwep_ci ? mgwep_ci_name(use_mgwep_ci) : "new")
 			: "none",
 		  gsm_lchant_name(lchan->type),
-		  gsm48_chan_mode_name(lchan->tch_mode));
+		  gsm48_chan_mode_name(lchan->tch_mode),
+		  (lchan->activate.info.encr.alg_id ? : 1)-1,
+		  lchan->activate.info.encr.key_len ? osmo_hexdump_nospc(lchan->activate.info.encr.key,
+									 lchan->activate.info.encr.key_len) : "none");
 
 	/* Ask for the timeslot to make ready for this lchan->type.
 	 * We'll receive LCHAN_EV_TS_READY or LCHAN_EV_TS_ERROR in response. */
@@ -657,6 +652,8 @@ static void lchan_fsm_wait_activ_ack_onenter(struct osmo_fsm_inst *fi, uint32_t
 		break;
 	}
 
+	lchan->encr = lchan->activate.info.encr;
+
 	rc = rsl_tx_chan_activ(lchan, act_type, ho_ref);
 	if (rc)
 		lchan_fail_to(LCHAN_ST_UNUSED, "Tx Chan Activ failed: %s (%d)", strerror(-rc), rc);