test: zdtm -- Add proc-self test

Just open /proc/self/ns/net and check if
it remains the same on restore.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

test/zdtm/live/static/Makefile

@@ -66,6 +66,7 @@ TST_NOFILE	=				\
 		xids00				\
 		groups				\
 		file_fown			\
+		proc-self			\
 		eventfs00			\
 		signalfd00			\
 		inotify00			\

test/zdtm/live/static/proc-self.c

+#define _GNU_SOURCE         /* See feature_test_macros(7) */
+#include <unistd.h>
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <string.h>
+#include <utime.h>
+
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include "zdtmtst.h"
+
+const char *test_doc	= "Check for /proc/self/ns path restore";
+const char *test_author	= "Cyrill Gorcunov <gorcunov@openvz.org>";
+
+const char nspath[] = "/proc/self/ns/net";
+
+int read_fd_link(int lfd, char *buf, size_t size)
+{
+	ssize_t ret;
+	char t[32];
+
+	snprintf(t, sizeof(t), "/proc/self/fd/%d", lfd);
+	ret = readlink(t, buf, size - 1);
+	if (ret < 0) {
+		err("Can't read link of fd %d", lfd);
+		return -1;
+	}
+	buf[ret] = 0;
+
+	return 0;
+}
+
+int main(int argc, char *argv[])
+{
+	char path_orig[64], path_new[64];
+	int fd_self, fd_new;
+
+	test_init(argc, argv);
+
+	memset(path_orig, 0, sizeof(path_orig));
+	memset(path_new, 0, sizeof(path_new));
+
+	fd_self = open(nspath, O_RDONLY);
+	if (fd_self < 0) {
+		err("Can't open %s", nspath);
+		return -1;
+	}
+
+	if (read_fd_link(fd_self, path_orig, sizeof(path_orig))) {
+		err("Can't fill original path");
+		return -1;
+	}
+
+	test_daemon();
+	test_waitsig();
+
+	fd_new = open(nspath, O_RDONLY);
+	if (fd_new < 0) {
+		err("Can't open %s", nspath);
+		return -1;
+	}
+
+	if (read_fd_link(fd_new, path_new, sizeof(path_new))) {
+		err("Can't fill new path");
+		return -1;
+	}
+
+	if (memcmp(path_orig, path_new, sizeof(path_orig))) {
+		fail("Paths mismatch %s %s\n", path_orig, path_new);
+		return -1;
+	}
+
+	pass();
+	return 0;
+}