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.c

@@ -0,0 +1,130 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#include "fd-util.h"
+#include "fileio.h"
+#include "log.h"
+#include "macro.h"
+#include "path-util.h"
+#include "string-util.h"
+#include "sysctl-util.h"
+
+char *sysctl_normalize(char *s) {
+        char *n;
+
+        n = strpbrk(s, "/.");
+
+        /* If the first separator is a slash, the path is
+         * assumed to be normalized and slashes remain slashes
+         * and dots remains dots. */
+
+        if (n && *n == '.')
+                /* Dots become slashes and slashes become dots. Fun. */
+                do {
+                        if (*n == '.')
+                                *n = '/';
+                        else
+                                *n = '.';
+
+                        n = strpbrk(n + 1, "/.");
+                } while (n);
+
+        path_simplify(s, true);
+
+        /* Kill the leading slash, but keep the first character of the string in the same place. */
+        if (*s == '/' && *(s+1))
+                memmove(s, s+1, strlen(s));
+
+        return s;
+}
+
+int sysctl_write(const char *property, const char *value) {
+        char *p;
+        _cleanup_close_ int fd = -1;
+
+        assert(property);
+        assert(value);
+
+        log_debug("Setting '%s' to '%.*s'.", property, (int) strcspn(value, NEWLINE), value);
+
+        p = strjoina("/proc/sys/", property);
+        fd = open(p, O_WRONLY|O_CLOEXEC);
+        if (fd < 0)
+                return -errno;
+
+        if (!endswith(value, "\n"))
+                value = strjoina(value, "\n");
+
+        if (write(fd, value, strlen(value)) < 0)
+                return -errno;
+
+        return 0;
+}
+
+int sysctl_writef(const char *property, const char *format, ...) {
+        _cleanup_free_ char *v = NULL;
+        va_list ap;
+        int r;
+
+        va_start(ap, format);
+        r = vasprintf(&v, format, ap);
+        va_end(ap);
+
+        if (r < 0)
+                return -ENOMEM;
+
+        return sysctl_write(property, v);
+}
+
+int sysctl_write_ip_property(int af, const char *ifname, const char *property, const char *value) {
+        const char *p;
+
+        assert(IN_SET(af, AF_INET, AF_INET6));
+        assert(property);
+        assert(value);
+
+        p = strjoina("/proc/sys/net/ipv", af == AF_INET ? "4" : "6",
+                     ifname ? "/conf/" : "", strempty(ifname),
+                     property[0] == '/' ? "" : "/", property);
+
+        log_debug("Setting '%s' to '%s'", p, value);
+
+        return write_string_file(p, value, WRITE_STRING_FILE_VERIFY_ON_FAILURE | WRITE_STRING_FILE_DISABLE_BUFFER);
+}
+
+int sysctl_read(const char *property, char **ret) {
+        char *p;
+
+        assert(property);
+        assert(ret);
+
+        p = strjoina("/proc/sys/", property);
+        return read_full_virtual_file(p, ret, NULL);
+}
+
+int sysctl_read_ip_property(int af, const char *ifname, const char *property, char **ret) {
+        _cleanup_free_ char *value = NULL;
+        const char *p;
+        int r;
+
+        assert(IN_SET(af, AF_INET, AF_INET6));
+        assert(property);
+
+        p = strjoina("/proc/sys/net/ipv", af == AF_INET ? "4" : "6",
+                     ifname ? "/conf/" : "", strempty(ifname),
+                     property[0] == '/' ? "" : "/", property);
+
+        r = read_full_virtual_file(p, &value, NULL);
+        if (r < 0)
+                return r;
+
+        truncate_nl(value);
+        if (ret)
+                *ret = TAKE_PTR(value);
+
+        return r;
+}