Add APN utility function to libosmogsm

The current functions are used to 'qualify' an APN from the
user-supplied APN name (name identifier) towards the fully-qualified
APN name which is used in the .grps DNS zone.

1 files changed, 38 insertions, 0 deletions

diff --git a/src/gsm/apn.c b/src/gsm/apn.c
new file mode 100644
index 00000000..413130aa
--- /dev/null
+++ b/src/gsm/apn.c
@@ -0,0 +1,38 @@
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <osmocom/gsm/apn.h>
+
+#define APN_OI_GPRS_FMT	"mnc%03u.mcc%03u.gprs"
+#define APN_GPRS_FMT	"%s.mnc%03u.mcc%03u.gprs"
+
+static char apn_strbuf[APN_MAXLEN+1];
+
+char *osmo_apn_qualify(unsigned int mcc, unsigned int mnc, const char *ni)
+{
+	snprintf(apn_strbuf, sizeof(apn_strbuf)-1, APN_GPRS_FMT,
+		ni, mnc, mcc);
+	apn_strbuf[sizeof(apn_strbuf)-1] = '\0';
+
+	return apn_strbuf;
+}
+
+char *osmo_apn_qualify_from_imsi(const char *imsi,
+				 const char *ni, int have_3dig_mnc)
+{
+	char cbuf[3+1], nbuf[3+1];
+
+	strncpy(cbuf, imsi, 3);
+	cbuf[3] = '\0';
+
+	if (have_3dig_mnc) {
+		strncpy(nbuf, imsi+3, 3);
+		nbuf[3] = '\0';
+	} else {
+		strncpy(nbuf, imsi+3, 2);
+		nbuf[2] = '\0';
+	}
+	return osmo_apn_qualify(atoi(cbuf), atoi(nbuf), ni);
+}