gsm0808: add BSSMAP Cell Identifier matching API

Add
* osmo_lai_cmp() (to use in gsm0808_cell_id_u_matches())
* osmo_cgi_cmp() (to use in gsm0808_cell_id_u_matches())
* gsm0808_cell_id_u_match() (to re-use for single IDs and lists)
* gsm0808_cell_ids_match()
* gsm0808_cell_id_matches_list()
* Unit tests in gsm0808_test.c

Rationale:

For inter-BSC handover, it is interesting to find matches between *differing*
Cell Identity kinds. For example, if a cell as CGI 23-42-3-5, and a HO for
LAC-CI 3-5 should be handled, we need to see the match.

This is most interesting for osmo-msc, i.e. to direct the BSSMAP Handover
Request towards the correct BSC or MSC.

It is also interesting for osmo-bsc's VTY interface, to be able to manage
cells' neighbors and to trigger manual handovers by various Cell Identity
handles, as the user would expect them.

Change-Id: I5535f0d149c2173294538df75764dd181b023312

1 files changed, 34 insertions, 0 deletions

diff --git a/src/gsm/gsm23003.c b/src/gsm/gsm23003.c
index 1d9cefe6..95fca91a 100644
--- a/src/gsm/gsm23003.c
+++ b/src/gsm/gsm23003.c
@@ -324,6 +324,40 @@ int osmo_plmn_cmp(const struct osmo_plmn_id *a, const struct osmo_plmn_id *b)
 	return osmo_mnc_cmp(a->mnc, a->mnc_3_digits, b->mnc, b->mnc_3_digits);
 }
 
+/* Compare two LAI.
+ * The order of comparison is MCC, MNC, LAC. See also osmo_plmn_cmp().
+ * \param a[in]  "Left" side LAI.
+ * \param b[in]  "Right" side LAI.
+ * \returns 0 if the LAI are equal, -1 if a < b, 1 if a > b. */
+int osmo_lai_cmp(const struct osmo_location_area_id *a, const struct osmo_location_area_id *b)
+{
+	int rc = osmo_plmn_cmp(&a->plmn, &b->plmn);
+	if (rc)
+		return rc;
+	if (a->lac < b->lac)
+		return -1;
+	if (a->lac > b->lac)
+		return 1;
+	return 0;
+}
+
+/* Compare two CGI.
+ * The order of comparison is MCC, MNC, LAC, CI. See also osmo_lai_cmp().
+ * \param a[in]  "Left" side CGI.
+ * \param b[in]  "Right" side CGI.
+ * \returns 0 if the CGI are equal, -1 if a < b, 1 if a > b. */
+int osmo_cgi_cmp(const struct osmo_cell_global_id *a, const struct osmo_cell_global_id *b)
+{
+	int rc = osmo_lai_cmp(&a->lai, &b->lai);
+	if (rc)
+		return rc;
+	if (a->cell_identity < b->cell_identity)
+		return -1;
+	if (a->cell_identity > b->cell_identity)
+		return 1;
+	return 0;
+}
+
 /*! Generate TS 23.003 Section 19.2 Home Network Realm/Domain (text form)
  *  \param out[out] caller-provided output buffer, at least 33 bytes long
  *  \param plmn[in] Osmocom representation of PLMN ID (MCC + MNC)