host/gap: Add connection find by address API

This may be useful in some cases.

nimble/host/include/host/ble_gap.h

@@ -736,6 +736,22 @@ typedef int ble_gap_event_fn(struct ble_gap_event *event, void *arg);
  */
 int ble_gap_conn_find(uint16_t handle, struct ble_gap_conn_desc *out_desc);
 
+/**
+ * Searches for a connection with a peer with the specified address.
+ * If a matching connection is found, the supplied connection descriptor
+ * is filled correspondingly.
+ *
+ * @param addr      The ble address of a connected peer device to search for.
+ * @param out_desc  On success, this is populated with information relating to
+ *                  the matching connection.  Pass NULL if you don't need this
+ *                  information.
+ *
+ * @return          0 on success, BLE_HS_ENOTCONN if no matching connection was
+ *                  found.
+ */
+int ble_gap_conn_find_by_addr(const ble_addr_t *addr,
+                              struct ble_gap_conn_desc *out_desc);
+
 /**
  * Configures a connection to use the specified GAP event callback.  A
  * connection's GAP event callback is first specified when the connection is

nimble/host/src/ble_gap.c

@@ -436,6 +436,28 @@ ble_gap_conn_find(uint16_t handle, struct ble_gap_conn_desc *out_desc)
     }
 }
 
+int
+ble_gap_conn_find_by_addr(const ble_addr_t *addr,
+                          struct ble_gap_conn_desc *out_desc)
+{
+	struct ble_hs_conn *conn;
+
+	ble_hs_lock();
+
+	conn = ble_hs_conn_find_by_addr(addr);
+	if (conn != NULL && out_desc != NULL) {
+		ble_gap_fill_conn_desc(conn, out_desc);
+	}
+
+	ble_hs_unlock();
+
+	if (conn == NULL) {
+		return BLE_HS_ENOTCONN;
+	}
+
+	return 0;
+}
+
 static int
 ble_gap_extract_conn_cb(uint16_t conn_handle,
                         ble_gap_event_fn **out_cb, void **out_cb_arg)