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92 lines
2.7 KiB

commit 72bb3dbf0ecdf3ec96aee80e5d152c8be4394da1
Author: Liping Zhang <zlpnobody@gmail.com>
Date: Mon Feb 6 19:47:47 2017 +0800
xshared: using the blocking file lock request when we wait indefinitely
When using "-w" to avoid concurrent instances, we try to do flock() every
one second until it success. But one second maybe too long in some
situations, and it's hard to select a suitable interval time. So when
using "iptables -w" to wait indefinitely, it's better to block until
it become success.
Now do some performance tests. First, flush all the iptables rules in
filter table, and run "iptables -w -S" endlessly:
# iptables -F
# iptables -X
# while : ; do
iptables -w -S >&- &
done
Second, after adding and deleting the iptables rules 100 times, measure
the time cost:
# time for i in $(seq 100); do
iptables -w -A INPUT
iptables -w -D INPUT
done
Before this patch:
real 1m15.962s
user 0m0.224s
sys 0m1.475s
Apply this patch:
real 0m1.830s
user 0m0.168s
sys 0m1.130s
Signed-off-by: Liping Zhang <zlpnobody@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
diff --git a/iptables/xshared.c b/iptables/xshared.c
index 055acf2..f0a5ddd 100644
--- a/iptables/xshared.c
+++ b/iptables/xshared.c
@@ -1,4 +1,5 @@
#include <getopt.h>
+#include <errno.h>
#include <libgen.h>
#include <netdb.h>
#include <stdbool.h>
@@ -258,27 +259,29 @@ bool xtables_lock(int wait, struct timeval *wait_interval)
if (fd < 0)
return true;
+ if (wait == -1) {
+ if (flock(fd, LOCK_EX) == 0)
+ return true;
+
+ fprintf(stderr, "Can't lock %s: %s\n", XT_LOCK_NAME,
+ strerror(errno));
+ return false;
+ }
+
while (1) {
if (flock(fd, LOCK_EX | LOCK_NB) == 0)
return true;
- else if (wait >= 0 && timercmp(&time_left, wait_interval, <))
+ else if (timercmp(&time_left, wait_interval, <))
return false;
if (++i % 10 == 0) {
- if (wait != -1)
- fprintf(stderr, "Another app is currently holding the xtables lock; "
- "still %lds %ldus time ahead to have a chance to grab the lock...\n",
- time_left.tv_sec, time_left.tv_usec);
- else
- fprintf(stderr, "Another app is currently holding the xtables lock; "
- "waiting for it to exit...\n");
+ fprintf(stderr, "Another app is currently holding the xtables lock; "
+ "still %lds %ldus time ahead to have a chance to grab the lock...\n",
+ time_left.tv_sec, time_left.tv_usec);
}
wait_time = *wait_interval;
select(0, NULL, NULL, NULL, &wait_time);
- if (wait == -1)
- continue;
-
timersub(&time_left, wait_interval, &time_left);
}
}