bsc: Attempt to respond to paging to the MSC that paged
Inspect the message and see if it is a paging response,
then try to find the MSC that has paged this subscriber
and select this as the target MSC, also move the MSC to
the back of the list for 'load balancing'.
diff --git a/openbsc/src/osmo-bsc/osmo_bsc_filter.c b/openbsc/src/osmo-bsc/osmo_bsc_filter.c
index 7271fc8..200360a 100644
--- a/openbsc/src/osmo-bsc/osmo_bsc_filter.c
+++ b/openbsc/src/osmo-bsc/osmo_bsc_filter.c
@@ -53,8 +53,9 @@
}
}
-/* we will need to stop the paging request */
-static int handle_page_resp(struct gsm_subscriber_connection *conn, struct msgb *msg)
+/* extract a subscriber from the paging response */
+static struct gsm_subscriber *extract_sub(struct gsm_subscriber_connection *conn,
+ struct msgb *msg)
{
uint8_t mi_type;
char mi_string[GSM48_MI_SIZE];
@@ -64,7 +65,7 @@
if (msgb_l3len(msg) < sizeof(*gh) + sizeof(*resp)) {
LOGP(DMSC, LOGL_ERROR, "PagingResponse too small: %u\n", msgb_l3len(msg));
- return -1;
+ return NULL;
}
gh = msgb_l3(msg);
@@ -88,6 +89,14 @@
break;
}
+ return subscr;
+}
+
+/* we will need to stop the paging request */
+static int handle_page_resp(struct gsm_subscriber_connection *conn, struct msgb *msg)
+{
+ struct gsm_subscriber *subscr = extract_sub(conn, msg);
+
if (!subscr) {
LOGP(DMSC, LOGL_ERROR, "Non active subscriber got paged.\n");
return -1;
@@ -100,10 +109,36 @@
struct osmo_msc_data *bsc_find_msc(struct gsm_subscriber_connection *conn,
struct msgb *msg)
{
+ struct gsm48_hdr *gh;
+ int8_t pdisc;
+ uint8_t mtype;
struct osmo_bsc_data *bsc;
- struct osmo_msc_data *msc;
+ struct osmo_msc_data *msc, *pag_msc;
+ struct gsm_subscriber *subscr;
bsc = conn->bts->network->bsc_data;
+
+ if (msgb_l3len(msg) < sizeof(*gh)) {
+ LOGP(DMSC, LOGL_ERROR, "There is no GSM48 header here.\n");
+ return NULL;
+ }
+
+ gh = msgb_l3(msg);
+ pdisc = gh->proto_discr & 0x0f;
+ mtype = gh->msg_type & 0xbf;
+
+ /*
+ * We are asked to select a MSC here but they are not equal. We
+ * want to respond to a paging request on the MSC where we got the
+ * request from. This is where we need to decide where this connection
+ * will go.
+ */
+ if (pdisc == GSM48_PDISC_RR && mtype == GSM48_MT_RR_PAG_RESP)
+ goto paging;
+ else
+ goto round_robin;
+
+round_robin:
llist_for_each_entry(msc, &bsc->mscs, entry) {
if (!msc->msc_con->is_authenticated)
continue;
@@ -114,6 +149,34 @@
}
return NULL;
+
+paging:
+ subscr = extract_sub(conn, msg);
+
+ if (!subscr) {
+ LOGP(DMSC, LOGL_ERROR, "Got paged but no subscriber found.\n");
+ return NULL;
+ }
+
+ pag_msc = paging_get_data(conn->bts, subscr);
+ subscr_put(subscr);
+
+ llist_for_each_entry(msc, &bsc->mscs, entry) {
+ if (msc != pag_msc)
+ continue;
+
+ /*
+ * We don't check if the MSC is connected. In case it
+ * is not the connection will be dropped.
+ */
+
+ /* force round robin by moving it to the end */
+ llist_move_tail(&msc->entry, &bsc->mscs);
+ return msc;
+ }
+
+ LOGP(DMSC, LOGL_ERROR, "Got paged but no request found.\n");
+ return NULL;
}