diff options
| author | Lorenzo Colitti <lorenzo@google.com> | 2017-03-16 16:55:02 +0900 |
|---|---|---|
| committer | Pablo Neira Ayuso <pablo@netfilter.org> | 2017-03-21 14:54:03 +0100 |
| commit | 999eaa241212d3952ddff39a99d0d55a74e3639e (patch) | |
| tree | d68411f36cc17dd8fe2672f1ece0184a4e58f9e6 /iptables/ip6tables.c | |
| parent | 6e2e169eb66b63d2991e1c7ada931e3cdb0ced32 (diff) | |
iptables-restore: support acquiring the lock.
Currently, ip[6]tables-restore does not perform any locking, so it
is not safe to use concurrently with ip[6]tables.
This patch makes ip[6]tables-restore wait for the lock if -w
was specified. Arguments to -w and -W are supported in the same
was as they are in ip[6]tables.
The lock is not acquired on startup. Instead, it is acquired when
a new table handle is created (on encountering '*') and released
when the table is committed (COMMIT). This makes it possible to
keep long-running iptables-restore processes in the background
(for example, reading commands from a pipe opened by a system
management daemon) and simultaneously run iptables commands.
If -w is not specified, then the command proceeds without taking
the lock.
Tested as follows:
1. Run iptables-restore -w, and check that iptables commands work
with or without -w.
2. Type "*filter" into the iptables-restore input. Verify that
a) ip[6]tables commands without -w fail with "another app is
currently holding the xtables lock...".
b) ip[6]tables commands with "-w 2" fail after 2 seconds.
c) ip[6]tables commands with "-w" hang until "COMMIT" is
typed into the iptables-restore window.
3. With the lock held by an ip6tables-restore process:
strace -e flock /tmp/iptables/sbin/iptables-restore -w 1 -W 100000
shows 11 calls to flock and fails.
4. Run an iptables-restore with -w and one without -w, and check:
a) Type "*filter" in the first and then the second, and the
second exits with an error.
b) Type "*filter" in the second and "*filter" "-S" "COMMIT"
into the first. The rules are listed only when the first
copy sees "COMMIT".
Signed-off-by: Narayan Kamath <narayan@google.com>
Signed-off-by: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Diffstat (limited to 'iptables/ip6tables.c')
| -rw-r--r-- | iptables/ip6tables.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/iptables/ip6tables.c b/iptables/ip6tables.c index 4d77721b..579d347b 100644 --- a/iptables/ip6tables.c +++ b/iptables/ip6tables.c @@ -1779,7 +1779,7 @@ int do_command6(int argc, char *argv[], char **table, generic_opt_check(command, cs.options); /* Attempt to acquire the xtables lock */ - if (!restore && !xtables_lock(wait, &wait_interval)) { + if (!restore && xtables_lock(wait, &wait_interval) == XT_LOCK_BUSY) { fprintf(stderr, "Another app is currently holding the xtables lock. "); if (wait == 0) fprintf(stderr, "Perhaps you want to use the -w option?\n"); |