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.
diff --git a/include/osmocom/gsm/apn.h b/include/osmocom/gsm/apn.h
new file mode 100644
index 0000000..d8d7399
--- /dev/null
+++ b/include/osmocom/gsm/apn.h
@@ -0,0 +1,13 @@
+#pragma once
+
+#include <stdint.h>
+
+/* 23.003 Section 9.1.1, excluding any terminating zero byte */
+#define APN_NI_MAXLEN 63
+
+/* 23.003 Section 9.1, excluding any terminating zero byte */
+#define APN_MAXLEN 100
+
+char *osmo_apn_qualify(unsigned int mcc, unsigned int mnc, const char *ni);
+char *osmo_apn_qualify_from_imsi(const char *imsi,
+ const char *ni, int have_3dig_mnc);