implement support for 3-digit MNC with leading zeros

Enable representing three-digit MNC with leading zeros. The MNCs 23 and 023 are
actually different; so far we treated both as 23. Re-encode an incoming BCD or
string of 023 as it were, i.e. not dropping the leading zero as 23.

Break ABI compatibility by changing the size and ordering of structs
gprs_ra_id, osmo_plmn_id, osmo_cell_global_id, ... by adding an mnc_3_digits
flag.

Change ordering in gprs_ra_id because the canonical oder is {Mobile Country
Code, Mobile Network Code}, so have the mcc member first.

ABI compatibility cannot be maintained for struct gprs_ra_id, since it is a
direct member of structs bssgp_bvc_ctx and bssgp_paging_info, and even just
adding a flag to the end would cause ABI changes of those structs. Similarly,
osmo_plmn_id is a direct member of osmo_location_area_id, and so forth.

Add new API to set and read this additional flag to preserve leading zeros:
- osmo_plmn_to_bcd(), osmo_plmn_from_bcd() after
  gsm48_mcc_mnc_to_bcd() and gsm48_mcc_mnc_from_bcd().
- gsm48_decode_lai2(), gsm48_generate_lai2() after
  gsm48_decode_lai(), gsm48_generate_lai().
- gsm0808_create_layer3_2() after gsm0808_create_layer3() and gsm0808_create_layer3_aoip().
- various osmo_*_name() functions in gsm23003.h (osmo_rai_name() still in
  gsm48.h close to struct gprs_ra_id definition). The amount and duplication of
  these may seem a bit overboard, but IMO they do make sense in this way.
  Though most code will soon see patches unifying the data structures used, in
  some cases (vty, ctrl) they are required singled out. Without these
  functions, the formatting ("%0*u", mnc_3_digits ?  3 : 2, mnc) would be
  duplicated all over our diverse repositories.

In various log output, include the leading MNC zeros.

Mark one TODO in card_fs_sim.c, I am not sure how to communicate a leading zero
to/from a SIM card FS. The focus here is on the core network / BSS.

To indicate ABI incompatibility, bump libosmogsm and libosmogb LIBVERSIONs;
adjust debian files accordingly.

Implementation choices:

- The default behavior upon zero-initialization will be the mnc_3_digits flag
  set to false, which yields exactly the previous behavior.

- I decided against packing the mnc with the mnc_3_digits field into a
  sub-struct because it would immediately break all builds of dependent
  projects: it would require immediate merging of numerous patches in other
  repositories, and it would make compiling older code against a newer
  libosmocore unneccessarily hard.

Change-Id: Id2240f7f518494c9df6c8bda52c0d5092f90f221

1 files changed, 72 insertions, 54 deletions

diff --git a/src/gsm/gsm48.c b/src/gsm/gsm48.c
index b58e9e2c..c2affaeb 100644
--- a/src/gsm/gsm48.c
+++ b/src/gsm/gsm48.c
@@ -30,6 +30,7 @@
 #include <string.h>
 #include <stdbool.h>
 #include <inttypes.h>
+#include <ctype.h>
 
 #include <osmocom/core/utils.h>
 #include <osmocom/core/byteswap.h>
@@ -180,6 +181,19 @@ const char *rr_cause_name(uint8_t cause)
 	return get_value_string(rr_cause_names, cause);
 }
 
+/*! Return MCC-MNC-LAC-RAC as string, in a static buffer.
+ * \param[in] rai  RAI to encode.
+ * \returns Static string buffer.
+ */
+const char *osmo_rai_name(const struct gprs_ra_id *rai)
+{
+	static char buf[32];
+	snprintf(buf, sizeof(buf), "%s-%s-%u-%u",
+		 osmo_mcc_name(rai->mcc), osmo_mnc_name(rai->mnc, rai->mnc_3_digits), rai->lac,
+		 rai->rac);
+	return buf;
+}
+
 /* FIXME: convert to value_string */
 static const char *cc_state_names[32] = {
 	"NULL",
@@ -418,15 +432,6 @@ const char *gsm48_mi_type_name(uint8_t mi)
 	return get_value_string(mi_type_names, mi);
 }
 
-static void to_bcd(uint8_t *bcd, uint16_t val)
-{
-	bcd[2] = val % 10;
-	val = val / 10;
-	bcd[1] = val % 10;
-	val = val / 10;
-	bcd[0] = val % 10;
-}
-
 /*! Checks is particular message is cipherable in A/Gb mode according to
  *         3GPP TS 24.008 § 4.7.1.2
  *  \param[in] hdr Message header
@@ -451,64 +456,61 @@ bool gsm48_hdr_gmm_cipherable(const struct gsm48_hdr *hdr)
 	}
 }
 
-/* Convert MCC + MNC to BCD representation
- * \param[out] bcd_dst caller-allocated memory for output
- * \param[in] mcc Mobile Country Code
- * \param[in] mnc Mobile Network Code
- *
- * Convert given mcc and mnc to BCD and write to *bcd_dst, which must be an
- * allocated buffer of (at least) 3 bytes length. */
+/* Convert MCC + MNC to BCD representation, legacy implementation.
+ * Instead use osmo_plmn_to_bcd(), which is also capable of converting
+ * 3-digit MNC that have leading zeros. For parameters, also see there. */
 void gsm48_mcc_mnc_to_bcd(uint8_t *bcd_dst, uint16_t mcc, uint16_t mnc)
 {
-	uint8_t bcd[3];
-
-	to_bcd(bcd, mcc);
-	bcd_dst[0] = bcd[0] | (bcd[1] << 4);
-	bcd_dst[1] = bcd[2];
-
-	to_bcd(bcd, mnc);
-	/* FIXME: do we need three-digit MNC? See Table 10.5.3 */
-	if (mnc > 99) {
-		bcd_dst[1] |= bcd[2] << 4;
-		bcd_dst[2] = bcd[0] | (bcd[1] << 4);
-	} else {
-		bcd_dst[1] |= 0xf << 4;
-		bcd_dst[2] = bcd[1] | (bcd[2] << 4);
-	}
+	const struct osmo_plmn_id plmn = {
+		.mcc = mcc,
+		.mnc = mnc,
+		.mnc_3_digits = false,
+	};
+	osmo_plmn_to_bcd(bcd_dst, &plmn);
 }
 
-/* Convert given 3-byte BCD buffer to integers and write results to *mcc and
- * *mnc. The first three BCD digits result in the MCC and the remaining ones in
- * the MNC. */
+/* Convert given 3-byte BCD buffer to integers, legacy implementation.
+ * Instead use osmo_plmn_from_bcd(), which is also capable of converting
+ * 3-digit MNC that have leading zeros. For parameters, also see there. */
 void gsm48_mcc_mnc_from_bcd(uint8_t *bcd_src, uint16_t *mcc, uint16_t *mnc)
 {
-	*mcc = (bcd_src[0] & 0x0f) * 100
-	     + (bcd_src[0] >> 4) * 10
-	     + (bcd_src[1] & 0x0f);
-
-	if ((bcd_src[1] & 0xf0) == 0xf0) {
-		*mnc = (bcd_src[2] & 0x0f) * 10
-		     + (bcd_src[2] >> 4);
-	} else {
-		*mnc = (bcd_src[2] & 0x0f) * 100
-		     + (bcd_src[2] >> 4) * 10
-		     + (bcd_src[1] >> 4);
-	}
+	struct osmo_plmn_id plmn;
+	osmo_plmn_from_bcd(bcd_src, &plmn);
+	*mcc = plmn.mcc;
+	*mnc = plmn.mnc;
 }
 
-/*! Encode TS 04.08 Location Area Identifier
- *  \param[out] caller-provided memory for output
+/*! Encode TS 04.08 Location Area Identifier, legacy implementation.
+ * Instead use gsm48_generate_lai2(), which is capable of three-digit MNC with leading zeros.
+ *  \param[out] lai48 caller-provided memory for output
  *  \param[in] mcc Mobile Country Code
  *  \param[in] mnc Mobile Network Code
  *  \param[in] lac Location Area Code */
 void gsm48_generate_lai(struct gsm48_loc_area_id *lai48, uint16_t mcc,
 			uint16_t mnc, uint16_t lac)
 {
-	gsm48_mcc_mnc_to_bcd(&lai48->digits[0], mcc, mnc);
-	lai48->lac = osmo_htons(lac);
+	const struct osmo_location_area_id lai = {
+		.plmn = {
+			.mcc = mcc,
+			.mnc = mnc,
+			.mnc_3_digits = false,
+		},
+		.lac = lac,
+	};
+	gsm48_generate_lai2(lai48, &lai);
+}
+
+/*! Encode TS 04.08 Location Area Identifier.
+ *  \param[out] lai48 caller-provided memory for output.
+ *  \param[in] lai input of MCC-MNC-LAC. */
+void gsm48_generate_lai2(struct gsm48_loc_area_id *lai48, const struct osmo_location_area_id *lai)
+{
+	osmo_plmn_to_bcd(&lai48->digits[0], &lai->plmn);
+	lai48->lac = osmo_htons(lai->lac);
 }
 
-/*! Decode TS 04.08 Location Area Identifier
+/*! Decode TS 04.08 Location Area Identifier, legacy implementation.
+ * Instead use gsm48_decode_lai2(), which is capable of three-digit MNC with leading zeros.
  *  \param[in] Location Area Identifier (encoded)
  *  \param[out] mcc Mobile Country Code
  *  \param[out] mnc Mobile Network Code
@@ -519,11 +521,25 @@ void gsm48_generate_lai(struct gsm48_loc_area_id *lai48, uint16_t mcc,
 int gsm48_decode_lai(struct gsm48_loc_area_id *lai, uint16_t *mcc,
 		     uint16_t *mnc, uint16_t *lac)
 {
-	gsm48_mcc_mnc_from_bcd(&lai->digits[0], mcc, mnc);
-	*lac = osmo_ntohs(lai->lac);
+	struct osmo_location_area_id decoded;
+	gsm48_decode_lai2(lai, &decoded);
+	*mcc = decoded.plmn.mcc;
+	*mnc = decoded.plmn.mnc;
+	*lac = decoded.lac;
 	return 0;
 }
 
+/*! Decode TS 04.08 Location Area Identifier.
+ *  \param[in] Location Area Identifier (encoded).
+ *  \param[out] decoded Target buffer to write decoded values of MCC-MNC-LAC.
+ *
+ * Attention: this function returns true integers, not hex! */
+void gsm48_decode_lai2(const struct gsm48_loc_area_id *lai, struct osmo_location_area_id *decoded)
+{
+	osmo_plmn_from_bcd(&lai->digits[0], &decoded->plmn);
+	decoded->lac = osmo_ntohs(lai->lac);
+}
+
 /*! Set DTX mode in Cell Options IE (3GPP TS 44.018)
  *  \param[in] op Cell Options structure in which DTX parameters will be set
  *  \param[in] full Mode for full-rate channels
@@ -682,10 +698,12 @@ void gsm48_parse_ra(struct gprs_ra_id *raid, const uint8_t *buf)
 	if ((buf[1] >> 4) == 0xf) {
 		raid->mnc = (buf[2] & 0xf) * 10;
 		raid->mnc += (buf[2] >> 4) * 1;
+		raid->mnc_3_digits = false;
 	} else {
 		raid->mnc = (buf[2] & 0xf) * 100;
 		raid->mnc += (buf[2] >> 4) * 10;
 		raid->mnc += (buf[1] >> 4) * 1;
+		raid->mnc_3_digits = true;
 	}
 
 	raid->lac = osmo_load16be(buf + 3);
@@ -704,7 +722,7 @@ void gsm48_encode_ra(struct gsm48_ra_id *out, const struct gprs_ra_id *raid)
 	out->digits[0] = ((raid->mcc / 100) % 10) | (((raid->mcc / 10) % 10) << 4);
 	out->digits[1] = raid->mcc % 10;
 
-	if (raid->mnc < 100) {
+	if (raid->mnc < 100 && !raid->mnc_3_digits) {
 		out->digits[1] |= 0xf0;
 		out->digits[2] = ((raid->mnc / 10) % 10) | ((raid->mnc % 10) << 4);
 	} else {