basic: move shared/sysctl-util.[ch] → basic/

This is self-contained ans allows us later to use the provided APIs from
other code in src/basic/

src/basic/sysctl-util.h

@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#include "macro.h"
+#include "stdio-util.h"
+#include "string-util.h"
+
+char *sysctl_normalize(char *s);
+int sysctl_read(const char *property, char **value);
+int sysctl_write(const char *property, const char *value);
+int sysctl_writef(const char *property, const char *format, ...) _printf_(2, 3);
+
+int sysctl_read_ip_property(int af, const char *ifname, const char *property, char **ret);
+int sysctl_write_ip_property(int af, const char *ifname, const char *property, const char *value);
+static inline int sysctl_write_ip_property_boolean(int af, const char *ifname, const char *property, bool value) {
+        return sysctl_write_ip_property(af, ifname, property, one_zero(value));
+}
+
+#define DEFINE_SYSCTL_WRITE_IP_PROPERTY(name, type, format)           \
+        static inline int sysctl_write_ip_property_##name(int af, const char *ifname, const char *property, type value) { \
+                char buf[DECIMAL_STR_MAX(type)];                        \
+                xsprintf(buf, format, value);                           \
+                return sysctl_write_ip_property(af, ifname, property, buf); \
+        }
+
+DEFINE_SYSCTL_WRITE_IP_PROPERTY(int, int, "%i");
+DEFINE_SYSCTL_WRITE_IP_PROPERTY(uint32, uint32_t, "%" PRIu32);