socket-util: add new helper socket_xattr_supported()

src/test/test-socket-util.c

@@ -4,6 +4,7 @@
 #include <grp.h>
 #include <linux/pkt_sched.h>
 #include <netinet/ip.h>
+#include <sys/stat.h>
 #include <unistd.h>
 
 #include "alloc-util.h"
@@ -550,4 +551,16 @@ TEST(tos_to_priority) {
         ASSERT_EQ(tos_to_priority(0xff), TC_PRIO_CONTROL);
 }
 
+TEST(socket_xattr_supported) {
+        int r;
+
+        r = socket_xattr_supported();
+        ASSERT_OK(r);
+
+        log_info("Extended attributes on socket inodes supported: %s", yes_no(r));
+
+        /* A second call must agree with the first. */
+        ASSERT_EQ(socket_xattr_supported(), r);
+}
+
 DEFINE_TEST_MAIN(LOG_DEBUG);