compl l3: move Paging Response handling out of bsc_find_msc()

Instead of iterating the llist of gsm_paging_requests first to find an MSC, and
then again right away to mark the paging as served, do both in the same step.

Change-Id: I447e61afc9934f3a5a82f6076e41c155d3328041

3 files changed, 62 insertions, 117 deletions

diff --git a/include/osmocom/bsc/paging.h b/include/osmocom/bsc/paging.h
index 2be71c39f..449a2ebaa 100644
--- a/include/osmocom/bsc/paging.h
+++ b/include/osmocom/bsc/paging.h
@@ -59,11 +59,7 @@ struct gsm_paging_request {
 int paging_request_bts(struct gsm_bts *bts, struct bsc_subscr *bsub, int type,
 			struct bsc_msc_data *msc);
 
-/* stop paging requests */
-void paging_request_stop(struct llist_head *bts_list,
-			 struct gsm_bts *_bts, struct bsc_subscr *bsub,
-			 struct gsm_subscriber_connection *conn,
-			 struct msgb *msg);
+struct bsc_msc_data *paging_request_stop(struct gsm_bts *bts, struct bsc_subscr *bsub);
 
 /* update paging load */
 void paging_update_buffer_space(struct gsm_bts *bts, uint16_t);
@@ -71,8 +67,6 @@ void paging_update_buffer_space(struct gsm_bts *bts, uint16_t);
 /* pending paging requests */
 unsigned int paging_pending_requests_nr(struct gsm_bts *bts);
 
-struct bsc_msc_data *paging_get_msc(struct gsm_bts *bts, struct bsc_subscr *bsub);
-
 void paging_flush_bts(struct gsm_bts *bts, struct bsc_msc_data *msc);
 void paging_flush_network(struct gsm_network *net, struct bsc_msc_data *msc);
 
diff --git a/src/osmo-bsc/gsm_08_08.c b/src/osmo-bsc/gsm_08_08.c
index 4c5391860..984e83044 100644
--- a/src/osmo-bsc/gsm_08_08.c
+++ b/src/osmo-bsc/gsm_08_08.c
@@ -196,11 +196,9 @@ static struct bsc_msc_data *bsc_find_msc(struct gsm_subscriber_connection *conn,
 	struct bsc_msc_data *msc_round_robin_next = NULL;
 	struct bsc_msc_data *msc_round_robin_first = NULL;
 	uint8_t round_robin_next_nr;
-	struct bsc_subscr *subscr;
 	bool is_emerg = false;
 	int16_t nri_v = -1;
 	bool is_null_nri = false;
-	struct gsm_bts *bts;
 
 	if (msgb_l3len(msg) < sizeof(*gh)) {
 		LOGP(DRSL, LOGL_ERROR, "There is no GSM48 header here.\n");
@@ -213,27 +211,6 @@ static struct bsc_msc_data *bsc_find_msc(struct gsm_subscriber_connection *conn,
 
 	is_emerg = (pdisc == GSM48_PDISC_MM && mtype == GSM48_MT_MM_CM_SERV_REQ) && is_cm_service_for_emerg(msg);
 
-	/* Has the subscriber been paged from a connected MSC? */
-	bts = conn_get_bts(conn);
-	if (bts && pdisc == GSM48_PDISC_RR && mtype == GSM48_MT_RR_PAG_RESP) {
-		subscr = bsc_subscr_find_by_mi(conn->network->bsc_subscribers, mi);
-		if (subscr) {
-			msc_target = paging_get_msc(bts, subscr);
-			bsc_subscr_put(subscr);
-			if (is_msc_usable(msc_target, is_emerg)) {
-				LOG_COMPL_L3(pdisc, mtype, LOGL_DEBUG, "%s matches earlier Paging from msc %d\n",
-					     osmo_mobile_identity_to_str_c(OTC_SELECT, mi), msc_target->nr);
-				rate_ctr_inc(&msc_target->msc_ctrs->ctr[MSC_CTR_MSCPOOL_SUBSCR_PAGED]);
-				return msc_target;
-			} else {
-				LOG_COMPL_L3(pdisc, mtype, LOGL_DEBUG,
-					     "%s matches earlier Paging from msc %d, but this MSC is not connected\n",
-					     osmo_mobile_identity_to_str_c(OTC_SELECT, mi), msc_target->nr);
-			}
-			msc_target = NULL;
-		}
-	}
-
 #define LOG_NRI(LOGLEVEL, FORMAT, ARGS...) \
 	LOGP(DMSC, LOGLEVEL, "%s NRI(%d)=0x%x=%d: " FORMAT, osmo_mobile_identity_to_str_c(OTC_SELECT, mi), \
 	     net->nri_bitlen, nri_v, nri_v, ##ARGS)
@@ -347,34 +324,6 @@ static struct bsc_msc_data *bsc_find_msc(struct gsm_subscriber_connection *conn,
 #undef LOG_NRI
 }
 
-static int handle_page_resp(struct gsm_subscriber_connection *conn, struct msgb *msg,
-			    const struct osmo_mobile_identity *mi)
-{
-	struct bsc_subscr *subscr = NULL;
-	struct gsm_bts *bts = conn_get_bts(conn);
-
-	if (!bts) {
-		/* should never happen */
-		LOGP(DRSL, LOGL_ERROR, "Paging Response without lchan\n");
-		return -1;
-	}
-
-	if (mi->type == GSM_MI_TYPE_NONE)
-		return -1;
-
-	subscr = bsc_subscr_find_by_mi(conn->network->bsc_subscribers, mi);
-	if (!subscr) {
-		LOGP(DMSC, LOGL_ERROR, "Non active subscriber got paged.\n");
-		rate_ctr_inc(&conn->lchan->ts->trx->bts->bts_ctrs->ctr[BTS_CTR_PAGING_NO_ACTIVE_PAGING]);
-		rate_ctr_inc(&conn->network->bsc_ctrs->ctr[BSC_CTR_PAGING_NO_ACTIVE_PAGING]);
-		return -1;
-	}
-
-	paging_request_stop(&conn->network->bts_list, bts, subscr, conn, msg);
-	bsc_subscr_put(subscr);
-	return 0;
-}
-
 static void parse_powercap(struct gsm_subscriber_connection *conn, struct msgb *msg)
 {
 	struct gsm48_hdr *gh = msgb_l3(msg);
@@ -433,6 +382,7 @@ int bsc_compl_l3(struct gsm_lchan *lchan, struct msgb *msg, uint16_t chosen_chan
 {
 	struct gsm_subscriber_connection *conn;
 	struct bsc_subscr *bsub = NULL;
+	struct bsc_msc_data *paged_from_msc;
 	struct bsc_msc_data *msc;
 	struct msgb *create_l3;
 	struct gsm0808_speech_codec_list scl;
@@ -454,6 +404,9 @@ int bsc_compl_l3(struct gsm_lchan *lchan, struct msgb *msg, uint16_t chosen_chan
 	pdisc = gsm48_hdr_pdisc(gh);
 	mtype = gsm48_hdr_msg_type(gh);
 
+	bts = lchan->ts->trx->bts;
+	OSMO_ASSERT(bts);
+
 	if (osmo_mobile_identity_decode_from_l3(&mi, msg, false)) {
 		LOG_COMPL_L3(pdisc, mtype, LOGL_ERROR, "Cannot extract Mobile Identity: %s\n",
 			     msgb_hexdump_c(OTC_SELECT, msg));
@@ -482,8 +435,37 @@ int bsc_compl_l3(struct gsm_lchan *lchan, struct msgb *msg, uint16_t chosen_chan
 
 	log_set_context(LOG_CTX_BSC_SUBSCR, conn->bsub);
 
+	/* When receiving a Paging Response, stop Paging for this subscriber on all cells, and figure out which MSC
+	 * sent the Paging Request, if any. */
+	paged_from_msc = NULL;
+	if (pdisc == GSM48_PDISC_RR && mtype == GSM48_MT_RR_PAG_RESP) {
+		paged_from_msc = paging_request_stop(bts, conn->bsub);
+		if (!paged_from_msc) {
+			/* This looks like an unsolicited Paging Response. It is required to pick any MSC, because any
+			 * MT-CSFB calls were Paged by the MSC via SGs, and hence are not listed in the BSC. */
+			LOG_COMPL_L3(pdisc, mtype, LOGL_DEBUG,
+				     "%s Unsolicited Paging Response, possibly an MT-CSFB call.\n",
+				     osmo_mobile_identity_to_str_c(OTC_SELECT, &mi));
+
+			rate_ctr_inc(&bts->bts_ctrs->ctr[BTS_CTR_PAGING_NO_ACTIVE_PAGING]);
+			rate_ctr_inc(&bsc_gsmnet->bsc_ctrs->ctr[BSC_CTR_PAGING_NO_ACTIVE_PAGING]);
+		} else if (is_msc_usable(paged_from_msc, false)) {
+			LOG_COMPL_L3(pdisc, mtype, LOGL_DEBUG, "%s matches earlier Paging from msc %d\n",
+				     osmo_mobile_identity_to_str_c(OTC_SELECT, &mi), paged_from_msc->nr);
+			rate_ctr_inc(&paged_from_msc->msc_ctrs->ctr[MSC_CTR_MSCPOOL_SUBSCR_PAGED]);
+		} else {
+			LOG_COMPL_L3(pdisc, mtype, LOGL_DEBUG,
+				     "%s matches earlier Paging from msc %d, but this MSC is not connected\n",
+				     osmo_mobile_identity_to_str_c(OTC_SELECT, &mi), paged_from_msc->nr);
+			paged_from_msc = NULL;
+		}
+	}
+
 	/* find the MSC link we want to use */
-	msc = bsc_find_msc(conn, msg, &mi);
+	if (paged_from_msc)
+		msc = paged_from_msc;
+	else
+		msc = bsc_find_msc(conn, msg, &mi);
 	if (!msc) {
 		LOGP(DMSC, LOGL_ERROR, "Failed to find a MSC for a connection.\n");
 		rc = -1;
@@ -494,18 +476,7 @@ int bsc_compl_l3(struct gsm_lchan *lchan, struct msgb *msg, uint16_t chosen_chan
 	if (osmo_bsc_sigtran_new_conn(conn, msc) != BSC_CON_SUCCESS)
 		goto early_fail;
 
-	bts = conn_get_bts(conn);
-	if (!bts) {
-		/* should never happen */
-		LOG_COMPL_L3(pdisc, mtype, LOGL_ERROR, "%s: internal error: Compl L3 without BTS\n",
-			     osmo_mobile_identity_to_str_c(OTC_SELECT, &mi));
-		rc = -1;
-		goto early_fail;
-	}
-
 	parse_powercap(conn, msg);
-	if (pdisc == GSM48_PDISC_RR && mtype == GSM48_MT_RR_PAG_RESP)
-		handle_page_resp(conn, msg, &mi);
 
 	/* Send the Create Layer 3. */
 	use_scl = NULL;
diff --git a/src/osmo-bsc/paging.c b/src/osmo-bsc/paging.c
index 37ec61cef..0e5bf9fd0 100644
--- a/src/osmo-bsc/paging.c
+++ b/src/osmo-bsc/paging.c
@@ -387,13 +387,9 @@ int paging_request_bts(struct gsm_bts *bts, struct bsc_subscr *bsub, int type,
  *  to notify the paging originator that paging has completed.
  * \param[in] bts BTS on which we shall stop paging
  * \param[in] bsub subscriber which we shall stop paging
- * \param[in] conn connection to the subscriber (if any)
- * \param[in] msg message received from subscrbier (if any)
- * \returns 0 if an active paging request was stopped, an error code otherwise. */
-/* we consciously ignore the type of the request here */
-static int _paging_request_stop(struct gsm_bts *bts, struct bsc_subscr *bsub,
-				struct gsm_subscriber_connection *conn,
-				struct msgb *msg)
+ * \returns the MSC that paged the subscriber, if there was a pending request.
+ */
+static struct bsc_msc_data *paging_request_stop_bts(struct gsm_bts *bts, struct bsc_subscr *bsub)
 {
 	struct gsm_bts_paging_state *bts_entry = &bts->paging;
 	struct gsm_paging_request *req, *req2;
@@ -403,51 +399,47 @@ static int _paging_request_stop(struct gsm_bts *bts, struct bsc_subscr *bsub,
 	llist_for_each_entry_safe(req, req2, &bts_entry->pending_requests,
 				  entry) {
 		if (req->bsub == bsub) {
+			struct bsc_msc_data *from_msc = req->msc;
 			/* now give up the data structure */
 			paging_remove_request(&bts->paging, req);
 			LOG_BTS(bts, DPAG, LOGL_DEBUG, "Stop paging %s\n", bsc_subscr_name(bsub));
-			return 0;
+			return from_msc;
 		}
 	}
 
-	return -ENOENT;
+	return NULL;
 }
 
 /*! Stop paging on all other bts'
- * \param[in] bts_list list of BTSs to iterate
- * \param[in] _bts BTS which has received a paging response
+ * \param[in] bts BTS which has received a paging response
  * \param[in] bsub subscriber
- * \param[in] msgb L3 message that we have received from \a bsub on \a _bts */
-void paging_request_stop(struct llist_head *bts_list,
-			 struct gsm_bts *_bts, struct bsc_subscr *bsub,
-			 struct gsm_subscriber_connection *conn,
-			 struct msgb *msg)
+ * \returns the MSC that paged the subscriber, if there was a pending request.
+ */
+struct bsc_msc_data *paging_request_stop(struct gsm_bts *bts, struct bsc_subscr *bsub)
 {
-	struct gsm_bts *bts;
-
-	log_set_context(LOG_CTX_BSC_SUBSCR, bsub);
-	conn->bsub = bsc_subscr_get(bsub);
-	gscon_update_id(conn);
+	struct gsm_bts *bts_i;
+	struct bsc_msc_data *paged_from_msc;
+	OSMO_ASSERT(bts);
+
+	paged_from_msc = paging_request_stop_bts(bts, bsub);
+	if (paged_from_msc) {
+		rate_ctr_inc(&bts->bts_ctrs->ctr[BTS_CTR_PAGING_RESPONDED]);
+		rate_ctr_inc(&bts->network->bsc_ctrs->ctr[BSC_CTR_PAGING_RESPONDED]);
+	}
 
-	/* Stop this first and dispatch the request */
-	if (_bts) {
-		if (_paging_request_stop(_bts, bsub, conn, msg) == 0) {
-			rate_ctr_inc(&_bts->bts_ctrs->ctr[BTS_CTR_PAGING_RESPONDED]);
-			rate_ctr_inc(&_bts->network->bsc_ctrs->ctr[BSC_CTR_PAGING_RESPONDED]);
+	llist_for_each_entry(bts_i, &bsc_gsmnet->bts_list, list) {
+		struct bsc_msc_data *paged_from_msc2 = paging_request_stop_bts(bts_i, bsub);
+		if (!paged_from_msc && paged_from_msc2) {
+			/* If this happened, it would be a bit weird: it means there was no Paging Request
+			 * pending on the BTS that sent the Paging Reponse, but there *is* a Paging Request
+			 * pending on a different BTS. But why not return an MSC when we found one. */
+			paged_from_msc = paged_from_msc2;
 		}
 	}
 
-	/* Make sure to cancel this everywhere else */
-	llist_for_each_entry(bts, bts_list, list) {
-		/* Sort of an optimization. */
-		if (bts == _bts)
-			continue;
-		_paging_request_stop(bts, bsub, NULL, NULL);
-	}
-	log_set_context(LOG_CTX_BSC_SUBSCR, NULL);
+	return paged_from_msc;
 }
 
-
 /*! Update the BTS paging buffer slots on given BTS */
 void paging_update_buffer_space(struct gsm_bts *bts, uint16_t free_slots)
 {
@@ -472,18 +464,6 @@ unsigned int paging_pending_requests_nr(struct gsm_bts *bts)
 	return requests;
 }
 
-/*! Find any paging data for the given subscriber at the given BTS. */
-struct bsc_msc_data *paging_get_msc(struct gsm_bts *bts, struct bsc_subscr *bsub)
-{
-	struct gsm_paging_request *req;
-
-	llist_for_each_entry(req, &bts->paging.pending_requests, entry)
-		if (req->bsub == bsub)
-			return req->msc;
-
-	return NULL;
-}
-
 /*! Flush all paging requests at a given BTS for a given MSC (or NULL if all MSC should be flushed). */
 void paging_flush_bts(struct gsm_bts *bts, struct bsc_msc_data *msc)
 {