[CRIU] [PATCH] kerndat: redirect iptables output to /dev/null

[Pavel Tikhomirov]

fix for commit 68a938ea84f4 ("net/iptables: check iptables command has
wait option")

else each criu log contains iptables output:

(00.020184) Found task size of 7ffffffff000
Chain INPUT (policy ACCEPT)
target     prot opt source               destination

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination
(00.029481) irmap: Searching irmap cache in work dir

Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
---
 criu/kerndat.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/criu/kerndat.c b/criu/kerndat.c
index 8a639fd..1c0986f 100644
--- a/criu/kerndat.c
+++ b/criu/kerndat.c
@@ -441,12 +441,20 @@ int kerndat_loginuid(bool only_dump)
 
 static int kerndat_iptables_has_xtlocks(void)
 {
+	int fd;
 	char *argv[4] = { "sh", "-c", "iptables -w -L", NULL };
 
+	fd = open("/dev/null", O_RDWR);
+	if (fd < 0) {
+		fd = -1;
+		pr_perror("failed to open /dev/null, using log fd for xtlocks check");
+	}
+
 	kdat.has_xtlocks = 1;
-	if (cr_system(-1, -1, -1, "sh", argv, CRS_CAN_FAIL) == -1)
+	if (cr_system(fd, fd, fd, "sh", argv, CRS_CAN_FAIL) == -1)
 		kdat.has_xtlocks = 0;
 
+	close_safe(&fd);
 	return 0;
 }
 
-- 
2.5.5