sgsn: Copy the msisdn to the sgsn_data and use it in PDP activation

The MSISDN should be present for "security" reasons in the first
activation of a PDP context. Take the encoded MSISDN, store it for
future use and then put it into the PDP activation request.

The MM Context contains a field for a decoded MSISDN already. As
we need to forward the data to the GGSN I want to avoid having to
store TON and NPI in another place. Simply store the data in the
encoded form.
diff --git a/openbsc/src/gprs/gprs_subscriber.c b/openbsc/src/gprs/gprs_subscriber.c
index 60f223a..52e7ba7 100644
--- a/openbsc/src/gprs/gprs_subscriber.c
+++ b/openbsc/src/gprs/gprs_subscriber.c
@@ -1,6 +1,7 @@
 /* MS subscriber data handling */
 
 /* (C) 2014 by sysmocom s.f.m.c. GmbH
+ * (C) 2015 by Holger Hans Peter Freyther
  *
  * All Rights Reserved
  *
@@ -259,9 +260,22 @@
 static void gprs_subscr_gsup_insert_data(struct gsm_subscriber *subscr,
 					 struct gprs_gsup_message *gsup_msg)
 {
+	struct sgsn_subscriber_data *sdata = subscr->sgsn_data;
 	unsigned idx;
 	int rc;
 
+	if (gsup_msg->msisdn_enc) {
+		if (gsup_msg->msisdn_enc_len > sizeof(sdata->msisdn)) {
+			LOGP(DGPRS, LOGL_ERROR, "MSISDN too long (%zu)\n",
+				gsup_msg->msisdn_enc_len);
+			sdata->msisdn_len = 0;
+		} else {
+			memcpy(sdata->msisdn, gsup_msg->msisdn_enc,
+				gsup_msg->msisdn_enc_len);
+			sdata->msisdn_len = gsup_msg->msisdn_enc_len;
+		}
+	}
+
 	if (gsup_msg->pdp_info_compl) {
 		rc = gprs_subscr_pdp_data_clear(subscr);
 		if (rc > 0)