bsc_scan_msc_msg: check protocol discriminator
The function assumed an MM protocol discriminator without verifying it.
diff --git a/openbsc/src/osmo-bsc/osmo_bsc_filter.c b/openbsc/src/osmo-bsc/osmo_bsc_filter.c
index a71871f..14e0b71 100644
--- a/openbsc/src/osmo-bsc/osmo_bsc_filter.c
+++ b/openbsc/src/osmo-bsc/osmo_bsc_filter.c
@@ -336,6 +336,7 @@
struct gsm_network *net;
struct gsm48_loc_area_id *lai;
struct gsm48_hdr *gh;
+ uint8_t pdisc;
uint8_t mtype;
int length = msgb_l3len(msg);
@@ -347,6 +348,10 @@
gh = (struct gsm48_hdr *) msgb_l3(msg);
length -= (const char *)&gh->data[0] - (const char *)gh;
+ pdisc = gsm48_hdr_pdisc(gh);
+ if (pdisc != GSM48_PDISC_MM)
+ return 0;
+
mtype = gsm48_hdr_msg_type(gh);
net = conn->bts->network;
msc = conn->sccp_con->msc;