[iptables PATCH v2] iptables: accept lock file name at runtime

[Giuseppe Scrivano <gscrivan@redhat.com>]

allow users to override at runtime the lock file to use through the
XTABLES_LOCKFILE environment variable.

It allows using iptables from a network namespace owned by an user
that has no write access to XT_LOCK_NAME (by default under /run), and
without setting up a new mount namespace.

$ XTABLES_LOCKFILE=/tmp/xtables unshare -rn iptables ...

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>
---
 iptables/xshared.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/iptables/xshared.c b/iptables/xshared.c
index c1d1371a..caf1dfcc 100644
--- a/iptables/xshared.c
+++ b/iptables/xshared.c
@@ -249,12 +249,17 @@ void xs_init_match(struct xtables_match *match)
 static int xtables_lock(int wait, struct timeval *wait_interval)
 {
 	struct timeval time_left, wait_time;
+	const char *lock_file;
 	int fd, i = 0;
 
 	time_left.tv_sec = wait;
 	time_left.tv_usec = 0;
 
-	fd = open(XT_LOCK_NAME, O_CREAT, 0600);
+	lock_file = getenv("XTABLES_LOCKFILE");
+	if (lock_file == NULL || lock_file[0] == '\0')
+		lock_file = XT_LOCK_NAME;
+
+	fd = open(lock_file, O_CREAT, 0600);
 	if (fd < 0) {
 		fprintf(stderr, "Fatal: can't open lock file %s: %s\n",
 			XT_LOCK_NAME, strerror(errno));
-- 
2.26.2