| Commit message (Collapse) | Author | Age | Files | Lines |
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Currently, iptables programs will exit with an error if the
iptables lock cannot be acquired, but will silently continue if
the lock cannot be opened at all. This can cause unexpected
failures (with unhelpful error messages) in the presence of
concurrent updates, which can be very difficult to find in a
complex or multi-administrator system.
Instead, refuse to do anything if the lock cannot be acquired.
The behaviour is not affected by command-line flags because:
1. In order to reliably avoid concurrent modification, all
invocations of iptables commands must follow this behaviour.
2. Whether or not the lock can be opened is typically not
a run-time condition but is likely to be a configuration
error.
Existing systems that depended on things working mostly correctly
even if there was no lock might be affected by this change.
However, that is arguably a configuration error, and now that the
iptables lock is configurable, it is trivial to provide a lock
file that is always accessible: if nothing else, the iptables
binary itself can be used. The lock does not have to be writable,
only readable.
Tested by configuring the system to use an xtables.lock file in
a non-existent directory and observing that all commands failed.
Signed-off-by: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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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>
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1. Factor out repeated code to a new xs_has_arg function.
2. Add a new parse_wait_time option to parse the value of -w.
3. Make parse_wait_interval take argc and argv so its callers
can be simpler.
Signed-off-by: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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If quotes are escaped, nft -f is unable to parse and load the translated
ruleset.
Signed-off-by: Pablo M. Bermudo Garay <pablombg@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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ip[6]tables currently waits for 1 second for the xtables lock to be
freed if the -w option is used. We have seen that the lock is held
much less than that resulting in unnecessary delay when trying to
acquire the lock. This problem is even severe in case of latency
sensitive applications.
Introduce a new option 'W' to specify the wait interval in microseconds.
If this option is not specified, the command sleeps for 1 second by
default.
v1->v2: Change behavior to take millisecond sleep as an argument to
-w as suggested by Pablo. Also maintain current behavior for -w to
sleep for 1 second as mentioned by Liping.
v2->v3: Move the millisecond behavior to a new option as suggested
by Pablo.
v3->v4: Use select instead of usleep. Sleep every iteration for
the time specified in the "-W" argument. Update man page.
v4->v5: Fix compilation error when enabling nftables
v5->v6: Simplify -W so it only takes the interval wait in microseconds.
Bail out if -W is specific but -w is not.
Joint work with Pablo Neira.
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch adds an optional numeric argument
to -w option (added with 93587a0) so one can
specify how long to wait for an exclusive lock.
If the value isn't specified it works as before,
i.e. program waits indefinitely.
If user specifies it, program exits after
the given time interval passes.
This patch also adds the -w/--wait to nftables
compat code, so the parser doesn't complain.
[ In the original patch, iptables-compat -w X was not working,
I have fixed by adding the dummy code not to break scripts
using the new optional argument --pablo ]
Signed-off-by: Jiri Popelka <jpopelka@redhat.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch adds the following utilities:
* xtables
* xtables-restore
* xtables-save
* xtables-config
They all use Patrick's nf_tables infrastructure plus my compatibility
layer.
xtables, xtables-restore and xtables-save are syntax compatible with
ip[6]tables, ip[6]tables-restore and ip[6]tables-save.
Semantics aims to be similar, still the main exception is that there
is no commit operation. Thus, we incrementally add/delete rules without
entire table locking.
The following options are also not yet implemented:
-Z (this requires adding expr->ops->reset(...) so nft_counters can reset
internal state of expressions while dumping it)
-R and -E (this requires adding this feature to nf_tables)
-f (can be implemented with expressions: payload 6 (2-bytes) + bitwise a&b^!b + cmp neq 0)
-IPv6 support.
But those are a matter of time to get them done.
A new utility, xtables-config, is available to register tables and
chains. By default there is a configuration file that adds backward
compatible tables and chains under iptables/etc/xtables.conf. You have
to call this utility first to register tables and chains.
However, it would be possible to automagically register tables and
chains while using xtables and xtables-restore to get similar operation
than with iptables.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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There have been numerous complaints and bug reports over the years when admins
attempt to run more than one instance of iptables simultaneously. Currently
open bug reports which are related:
325: Parallel execution of the iptables is impossible
758: Retry iptables command on transient failure
764: Doing -Z twice in parallel breaks counters
822: iptables shows negative or other bad packet/byte counts
As Patrick notes in 325: "Since this has been a problem people keep running
into, I'd suggest to simply add some locking to iptables to catch the most
common case."
I started looking into alternatives to add locking, and of course the most
common/obvious solution is to use a pidfile. But this has various downsides,
such as if the application is terminated abnormally and the pidfile isn't
cleaned up. And this also requires a writable filesystem. Using a UNIX domain
socket file (e.g. in /var/run) has similar issues.
Starting in 2.2, Linux added support for abstract sockets. These sockets
require no filesystem, and automatically disappear once the application
terminates. This is the locking solution I chose to implement in ip[6]tables.
As an added bonus, since each network namespace has its own socket pool, an
ip[6]tables instance running in one namespace will not lock out an ip[6]tables
instance running in another namespace. A filesystem approach would have
to recognize and handle multiple network namespaces.
Signed-off-by: Phil Oester <kernel@linuxace.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This is useful for the upcoming patch about per-instance auxiliary
data.
Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
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`iptables -A INPUT -p tcp ! --syn` forgot the negation, i.e. it
was not present in a subsequent `iptables -S`.
Commit v1.4.11~77^2~9 missed the fact that after autoloading a proto
extension, cs.invert must not be touched until the next getopt call.
This is now fixed by having command_default return a value to indicate
whether to jump or not.
Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
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(Unclutter top-level dir)
Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
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