Introduce generic host config and related helpers

Add generic host config struct and related helpers for TCP-based probes
and use them for ctrl probe.

This will be used in follow-up patch for OpenVPN probe as well.

Change-Id: Ie321655a92cdbefbfaa056ac0d583397c83beccb
diff --git a/src/client.c b/src/client.c
new file mode 100644
index 0000000..6b37fc6
--- /dev/null
+++ b/src/client.c
@@ -0,0 +1,73 @@
+/* Generic client structure and related helpers */
+
+/* (C) 2018 by Harald Welte <laforge@gnumonks.org>
+ * (C) 2019 by sysmocom - s.f.m.c. GmbH.
+ * All Rights Reserved.
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ *
+ *  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.
+ */
+
+#include <stdbool.h>
+#include <string.h>
+#include <talloc.h>
+
+#include <osmocom/core/utils.h>
+
+#include "client.h"
+
+bool match_config(const struct host_cfg *cfg, const char *match, enum match_kind k)
+{
+	bool m_name = (strcmp(match, cfg->name) == 0),
+	     m_host = (strcmp(match, cfg->remote_host) == 0);
+
+	switch (k) {
+	case MATCH_NAME:
+		return m_name;
+	case MATCH_HOST:
+		return m_host;
+	case MATCH_EITHER:
+		return m_name | m_host;
+	case MATCH_BOTH:
+		return m_name & m_host;
+	default:
+		return false;
+	}
+
+	return false;
+}
+
+struct host_cfg *host_cfg_alloc(void *ctx, const char *name, const char *host, uint16_t port)
+{
+	struct host_cfg *cfg = talloc_zero(ctx, struct host_cfg);
+	if (!cfg)
+		return NULL;
+
+	cfg->name = talloc_strdup(cfg, name);
+	cfg->remote_host = talloc_strdup(cfg, host);
+	cfg->remote_port = port;
+
+	return cfg;
+}
+
+char *make_authority(void *ctx, const struct host_cfg *cfg)
+{
+	if (!cfg->remote_host)
+		return NULL;
+
+	return talloc_asprintf(ctx, "%s:%u", cfg->remote_host, cfg->remote_port);
+}