stats: Add the reporting framework

This commit provides the stats reporting framework that can manage
several types of measurement reporters. Initially support for
rate_ctr and the statsd protocol is included.

Sponsored-by: On-Waves ehf
diff --git a/include/osmocom/core/stats.h b/include/osmocom/core/stats.h
new file mode 100644
index 0000000..b4fb727
--- /dev/null
+++ b/include/osmocom/core/stats.h
@@ -0,0 +1,70 @@
+/* (C) 2015 by Sysmocom s.f.m.c. GmbH
+ *
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+#pragma once
+
+#include <sys/socket.h>
+#include <osmocom/core/linuxlist.h>
+
+enum stats_reporter_type {
+	STATS_REPORTER_STATSD,
+};
+
+struct stats_reporter {
+	enum stats_reporter_type type;
+	char *name;
+
+	/* config */
+	int enabled;
+	int interval;
+	char *name_prefix;
+	char *dest_addr_str;
+	char *bind_addr_str;
+	int dest_port;
+	int mtu;
+
+	/* state */
+	int running;
+	struct sockaddr dest_addr;
+	int dest_addr_len;
+	struct sockaddr bind_addr;
+	int bind_addr_len;
+	int fd;
+
+	struct llist_head list;
+};
+
+void stats_init(void *ctx);
+int stats_report();
+
+struct stats_reporter *stats_reporter_alloc(enum stats_reporter_type type,
+	const char *name);
+void stats_reporter_free(struct stats_reporter *srep);
+struct stats_reporter *stats_reporter_create_statsd(const char *name);
+
+struct stats_reporter *stats_reporter_find(enum stats_reporter_type type,
+	const char *name);
+
+int stats_reporter_set_remote_addr(struct stats_reporter *srep, const char *addr);
+int stats_reporter_set_remote_port(struct stats_reporter *srep, int port);
+int stats_reporter_set_local_addr(struct stats_reporter *srep, const char *addr);
+int stats_reporter_set_interval(struct stats_reporter *srep, int interval);
+int stats_reporter_set_name_prefix(struct stats_reporter *srep, const char *prefix);
+int stats_reporter_enable(struct stats_reporter *srep);
+int stats_reporter_disable(struct stats_reporter *srep);