basic + fundamental: Clean up includes

Split out of #37344.

src/basic/socket-util.c

@@ -1,8 +1,6 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 
-#include <arpa/inet.h>
-#include <errno.h>
-#include <limits.h>
+#include <fcntl.h>
 #include <linux/if.h>
 #include <linux/if_arp.h>
 #include <mqueue.h>
@@ -10,10 +8,7 @@
 #include <netdb.h>
 #include <netinet/ip.h>
 #include <poll.h>
-#include <stddef.h>
-#include <stdint.h>
 #include <stdio.h>
-#include <stdlib.h>
 #include <sys/ioctl.h>
 #include <unistd.h>
 
@@ -21,22 +16,23 @@
 #include "errno-util.h"
 #include "escape.h"
 #include "fd-util.h"
-#include "fileio.h"
 #include "format-ifname.h"
+#include "format-util.h"
+#include "in-addr-util.h"
 #include "io-util.h"
 #include "log.h"
 #include "memory-util.h"
 #include "parse-util.h"
 #include "path-util.h"
+#include "pidref.h"
 #include "process-util.h"
 #include "random-util.h"
 #include "socket-util.h"
+#include "sparse-endian.h"
 #include "string-table.h"
 #include "string-util.h"
 #include "strv.h"
 #include "sysctl-util.h"
-#include "user-util.h"
-#include "utf8.h"
 
 #if ENABLE_IDN
 #  define IDN_FLAGS NI_IDN
@@ -1688,7 +1684,7 @@ int socket_set_option(int fd, int af, int opt_ipv4, int opt_ipv6, int val) {
 }
 
 int socket_get_mtu(int fd, int af, size_t *ret) {
-        int mtu, r;
+        int mtu = 0, r; /* Avoid maybe-uninitialized false positive */
 
         if (af == AF_UNSPEC) {
                 af = socket_get_family(fd);