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This patch adds support to synchronize expectations between
firewalls. This addition aims to re-use as much as possible
of the existing infrastructure for stability reasons. The
expectation support has been tested with the FTP helper.
This extension requires libnetfilter_conntrack 1.0.0.
If this is the first time you're playing with conntrackd,
I *strongly* recommend you to get working setup of conntrackd
without expectation support before as described in the
documentation. Then, enabling expectation support is rather
easy.
To know more about expectations, if you're not familiar with them,
I suggest you to read:
"Netfilter's Connection Tracking System"
http://people.netfilter.org/pablo/docs/login.pdf
Reprinted from ;login: The Magazine of USENIX, vol. 31, no. 3
(Berkeley, CA: USENIX Association, 2006, pp40-45.)
In short, expectations allow one Linux firewall to filter multi-flow
traffic like FTP, SIP and H.323.
In my testbed, there are two firewalls in a primary-backup configuration
running keepalived. The use a couple of floating cluster IP address
(192.168.0.100 and 192.168.1.100) that are used by the client. These
firewalls protect one FTP server (192.168.1.2) that will be accessed by
one client.
In ASCII art, it looks like this:
192.168.0.100 192.168.1.100
eth1 eth2
fw-1
/ \ FTP
-- client ------ ------ server --
192.168.0.2 \ / 192.168.1.2
fw-2
This is the rule-set for the firewalls:
-A POSTROUTING -t nat -s 192.168.0.2/32 -d 192.168.1.2/32 -j SNAT --to-source 192.168.1.100
-A INPUT -p tcp -m tcp --dport 22 -j ACCEPT
-A INPUT -m state --state INVALID -j DROP
-A FORWARD -m state --state RELATED -j ACCEPT
-A FORWARD -i eth2 -m state --state ESTABLISHED -j ACCEPT
-A FORWARD -i eth1 -p tcp -m tcp --dport 21 --tcp-flags FIN,SYN,RST,ACK SYN -m state --state NEW -j ACCEPT
-A FORWARD -i eth1 -p tcp -m state --state ESTABLISHED -j ACCEPT
-A FORWARD -m state --state INVALID -j LOG --log-prefix "invalid: "
The following steps detail how to check that the expectation support
works fine for conntrackd:
1) You have to enable the expectation support in the configuration
file with the following option:
Sync {
...
Options {
ExpectationSync {
ftp
sip
h323
}
}
}
This enables expectation synchronization for the FTP, SIP and H.323 helpers.
You can alternatively use:
Sync {
...
Options {
ExpectationSync On
}
}
To enable expectation synchronization for all helpers.
2) Make sure you have loaded the FTP helper in both firewalls.
root@fw1# modprobe nf_conntrack_ftp
root@fw2# modprobe nf_conntrack_ftp
3) Switch to the client. Start one FTP control connection to one
server that is protected by the firewalls, enter passive mode:
(term-1) user@client$ nc 192.168.1.2 21
220 dummy FTP server
USER anonymous
331 Please specify the password.
PASS nothing
230 Login successful.
PASV
227 Entering Passive Mode (192,168,1,2,163,11).
This means that port 163*256+11=41739 will be used for the data
traffic. Read this if you are not familiar with the FTP protocol:
http://www.freefire.org/articles/ftpexample.php
3) Switch to fw-1 (primary) to check that the expectation is in the
internal cache.
root@fw1# conntrackd -i exp
proto=6 src=192.168.0.2 dst=192.168.1.2 sport=0 dport=41739 mask-src=255.255.255.255 mask-dst=255.255.255.255 sport=0 dport=65535 master-src=192.168.0.2 master-dst=192.168.1.2 sport=36390 dport=21 [active since 5s]
4) Switch to fw-2 (backup) to check that the expectation has been successfully
replicated.
root@fw2# conntrackd -e exp
proto=6 src=192.168.0.2 dst=192.168.1.2 sport=0 dport=41739 mask-src=255.255.255.255 mask-dst=255.255.255.255 sport=0 dport=65535 master-src=192.168.0.2 master-dst=192.168.1.2 sport=36390 dport=21 [active since 8s]
5) Make the primary firewall fw-1 fail. Now fw-2 becomes primary.
6) Switch to fw-2 (primary) to commit the external cache into the kernel.
root@fw2# conntrackd -c exp
The logs should display that the commit was successful:
root@fw2# tail -100f /var/log/conntrackd.log
[Wed Dec 7 22:16:31 2011] (pid=19195) [notice] committing external cache: expectations
[Wed Dec 7 22:16:31 2011] (pid=19195) [notice] Committed 1 new entries
[Wed Dec 7 22:16:31 2011] (pid=19195) [notice] commit has taken 0.000366 seconds
7) Switch to the client. Open a new terminal and connect to the port that
has been announced by the server:
(term-2) user@client$ nc -vvv 192.168.1.2 41739
(UNKNOWN) [192.168.1.2] 41739 (?) open
8) Switch to term-1 and ask for the file listing:
[...]
227 Entering Passive Mode (192,168,1,2,163,11).
LIST
9) Switch to term-2, it should display the listing. That means
everything has worked fine.
You may want to try disabling the expectation support and
repeating the steps to check that *it does not work* without
the state-synchronization.
You can also display expectation statistics by means of:
root@fwX# conntrackd -s exp
This update requires no changes in the primary-backup.sh script
that is used by the HA manager to interact with conntrackd. Thus,
we provide a backward compatible command line interface.
Regarding the Filter clause and expectations, we use the master
conntrack to filter expectation events. The filtering is performed
in user-space. No kernel-space filtering support for expectations
yet (this support should go in libnetfilter_conntrack at some
point).
This patch also includes support to disable caching and to allow
direct injection of expectations.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch fixes several minor nitpicks to support IPv6 failover:
* ICMPv6 type/code/id were missing in synchronization messages.
* The use of '-' as string in the configuration file was not allowed.
* Include example in configuration file under doc/.
Reported-by: Mohit Mehta <mohit.mehta@vyatta.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch adds a new option TCPWindowTracking that allows not
to disable TCP window tracking as it occurs by default.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch adds the clause `DisableInternalCache' that allows you
to bypass the internal cache. This clause can only be used with
the notrack synchronization mode.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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Under stress, the TCP stack may return EAGAIN if there is not
space left in the sender buffer. We also enqueue any other
error.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch adds support for TCP as protocol to replicate
state-changes between two daemons. Note that this only
makes sense with the notrack mode.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch adds the clause `DisableExternalCache' that allows you
to disable the external cache and to directly inject the entries
into the kernel conntrack table. As a result, the CPU consumption
of conntrackd increases. This clause can only be used with the
FT-FW and the notrack synchronization modes, but not with the
alarm mode.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch adds the NetlinkEventsReliable clause, this is useful
to turn on reliable Netlink event delivery. This features
requires a Linux kernel >= 2.6.31.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch is a cleanup, it removes a redudant declaration in the
parser.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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With this patch, you can change the scheduler policy and priority
for conntrackd. Using a RT scheduler policy reduces the chances to
hit ENOBUFS in Netlink.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch adds support for unicast UDP to the channel
infrastructure. With this patch, you can select UDP unicast to
propagate state-changes instead of multicast.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch adds two alias that removes an inconsistency in the
configuration file names. Now, the clauses that refers to Netlink
starts by the prefix "Netlink".
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch adds NetlinkOverrunResync. This option can be used to
set the amount of time after which the daemon resynchronizes itself
with the kernel state-table if it detects a Netlink overrun.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch adds ResendQueueSize, which sets the number of objects
that can be stored in the resend queue waiting to be confirmed.
The ResendBufferSize clause has been deprecated.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch adds the clause PollSecs that changes the normal
behaviour of conntrackd. With PollSecs set to > 0, conntrackd
polls every N seconds the entries.
This is the opposed behaviour of an event-driven behaviour but may
be useful for those that have really strong limitations in terms of
CPU consumption and want to perform a relaxed replication.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch adds support for redundant dedicated links. You can add
a pool of dedicated links that can be used if the current active
fails.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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Currently, the event handling can starve other event file
descriptors. This patch limits the number of event handling
iterations. The parameter is tunable via configuration file.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch adds CIDR-based filtering support. The current
implementation is O(n).
This patch also introduces the vector data type which is
used to store the IP address and the network mask.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch changes the current behaviour of the filtering selection.
Up to now, conntrackd has used the kernel version to select the
filtering method based on the following logic: If kernel is >= 2.6.26
we use BSF-based filtering from kernel-space, otherwise, default to
userspace.
However, this filtering method still lacks of IPv6 support and
it requires a patch that got into 2.6.29 to filter IPv6 addresses
from kernel-space. To fix this issue, we default to user-space
filtering and let the user choose the method via the configuration
file.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch adds the clause PurgeTimeout that sets the new timer
when conntrackd -t is called. This command is particularly useful
when the sysadmin triggers hand-overs between several nodes without
rebooting as it reduces the timers of the remaining entries in
the kernel. Thus, avoiding clashes between new and old entries that
may trigger INVALID packets.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch reworks the user-space filtering. Although we have
kernel-space filtering since Linux kernel >= 2.6.26, we keep userspace
filtering to ensure backward compatibility. Moreover, this patch
prepares the implementation of the kernel-space filtering via
libnetfilter_conntrack's high-level berkeley socket filter API.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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add missing string.h required by strdup in config parsing
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This patch introduces the TimeoutDestroy clause to determine how long a conntrack remains in the internal cache once it has been destroy from the kernel table.
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only which is incompatible AFAIK
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has been Max Kellermann and has no issues with relicensing their contributions.
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import only required C headers and put local headers on top to check
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o rename `persistent' mode to `alarm'
o rename `nack' mode to `ftfw'
o Now default synchronization mode is ftfw instead of alarm
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feature is particularly useful for active-active setup without connection persistency, ie. you cannot know which firewall would filter a packet that belongs to a connection.
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- use buffer of MTU size
conntrack:
- better protocol argument checkings
- fix per-protocol filtering, eg. conntrack -[L|E] -p tcp now works
- show per-protocol help, ie. conntrack -h -p tcp
- add alias --src for --orig-src and alias --dst for --orig-dst
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chain
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