check: Add tun support

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

cr-check.c

@@ -26,6 +26,7 @@
 #include "tty.h"
 #include "ptrace.h"
 #include "kerndat.h"
+#include "tun.h"
 
 static int check_tty(void)
 {
@@ -559,6 +560,7 @@ int cr_check(void)
 	ret |= check_ptrace_peeksiginfo();
 	ret |= check_mem_dirty_track();
 	ret |= check_posix_timers();
+	ret |= check_tun();
 
 	if (!ret)
 		pr_msg("Looks good.\n");

include/tun.h

@@ -10,4 +10,5 @@ extern const struct fdtype_ops tunfile_dump_ops;
 int dump_tun_link(NetDeviceEntry *nde, struct cr_fdset *fds);
 int restore_one_tun(NetDeviceEntry *nde, int nlsk);
 extern struct collect_image_info tunfile_cinfo;
+int check_tun(void);
 #endif

tun.c

@@ -44,6 +44,29 @@
 
 #define TUN_DEV_GEN_PATH	"/dev/net/tun"
 
+int check_tun(void)
+{
+	int fd, idx = 13, ret;
+
+	if (opts.check_ms_kernel) {
+		pr_warn("Skipping tun support check\n");
+		return 0;
+	}
+
+	fd = open(TUN_DEV_GEN_PATH, O_RDWR);
+	if (fd < 0) {
+		pr_perror("Can't check tun support");
+		return 0;
+	}
+
+	ret = ioctl(fd, TUNSETIFINDEX, &idx);
+	if (ret < 0)
+		pr_perror("No proper support for tun dump/restore");
+
+	close(fd);
+	return ret;
+}
+
 static LIST_HEAD(tun_links);
 
 struct tun_link {