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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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We now include one pointer to the object in the extra section.
This is required to generalize this code for the expectation
support. We consume 4-8 bytes extra, but we will not need more
changes to support expectations which is a good idea.
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This patch simplifies cache_get_extra which now takes only one
parameter that is the cache_object. With it, the extra area can be
calculated.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch generalizes the network message building and parsing
to prepare the upcoming expectation support.
Basically, it renames:
- NET_T_STATE_* by NET_T_STATE_CT_*, as I plan to add NET_T_STATE_EXP_*
- BUILD_NETMSG by BUILD_NETMSG_FROM_CT, and build_payload by ct2msg.
I plan to add exp2msg.
- parse_payload by msg2ct, since I plan to add msg2exp.
- modify object_status_to_network_type to prepare the support of
expectations.
- add prefix ct_ to all parsing functions in parse.c, as we will have
similar functions to convert messages to expectation objects.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch generalizes the caching infrastructure to store different
object types. This patch is the first in the series to prepare
support for the synchronization of expectations.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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Most callers of queue_add() assume that it returns != 0 in case of
success. However, it may return -1 in case that the queue gets full.
In that case, most callers have to:
- release the object that they want to enqueue.
- decrement the refcount, in case they have bumped it.
However, most of these callers are using the tx_queue which currently
has no limit in size at all. This fix is necessary in case that I
decide to limit the size of the transmission queue in the future
(which makes a lot of sense indeed).
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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This patch adds the LOCAL_RET_* return values. The return value
LOCAL_RET_STOLEN which allows to leave a client socket open while
waiting for an operation to finish.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch adds the name field to identify the queue by means of
a string. This patch is used by the next one that introduces
per-queue statistics.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch renames the statistics option that displays the content
of the resend queue which is used by the ftfw mode.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch is a cleanup. It renames the mcast_track_*() functions
by nethdr_track_*() because this functions are related to message
sequence tracking. They are not stick to multicast at all.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch reworks conntrackd to make it independent of the protocol
used to propagate state-changes. This patch adds the channel layer
abstraction, this layer allows you to add support for different
protocols like unicast UDP or TIPC.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch removes debug() and debug_ct(), I haven't use the
debugging information that these functions provide in years.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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The lifetime feature is used by all working modes, it is useful to
know how long it has been an entry living in the cache. This patch
moves the lifetime feature to the main caching code.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch moves the existing `-v' behaviour to `-s queue' where it
really belongs. The `-v' option is now left to display the version
which is the common use of it.
# conntrackd -v
Connection tracking userspace daemon v0.9.9. Licensed under GPLv2.
(C) 2006-2009 Pablo Neira Ayuso <pablo@netfilter.org>
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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The network headers already contain the message type set. It is not
necessary to set it up again.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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With this patch, all the states updates are enqueued in the
tx_queue. Thus, there's a single output path. This patch adds a
simple refcounting mechanism to note when an object is sitting in
the txqueue. This patch also removes the alarm that is required by
the ftfw approach.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch adds a generic tx queue for all synchronization modes.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch moves the helloing logic into ftfw_xmit. Still, the
helloing is kept in ftfw_send as we still have two possible paths
for messages. This will be removed in the next patches to make all
message go over a single txqueue.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch unifies the tx_list and the tx_queue to have only one
transmission queue. Since the tx_list hold state objects and
tx_queue control messages, I have introduced a queue node type
that can be used to differenciate the kind of information that
the node stores: object or control message.
This patch also reworks the existing queue class to include a
file descriptor that can be used to know if there are new data
added to the queue (see QUEUE_F_EVFD flag).
In this change, I have also modified the current evfd to make the
file descriptor to make read operations non-blocking. Moreover,
it keeps a counter that is used to know how many messages are
inserted in the queue.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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Currently, the caching system is implemented in a two layer
architecture: hashtable (inner layer) and cache (upper layer).
This patch reworks the hash-cache infrastructure to solve some
initial design problems to make it more flexible, the main strong
points of this patch are:
* Memory handling is done in the cache layer, not in the inner
hashtable layer. This removes one of the main dependencies between
the hashtable and the cache classes.
* Remove excessive encapsulation: the former cache used to hide a
lot of details of the inner hashtable implementation.
* Fix over-hashing of some operations: lookup-delete-add required
three hash calculations. Similarly, the update-or-add operation
required two hash calculations. Now, we calculate the hash once
and re-use the value how many times as we need.
This patch simplifies the caching system. As a result, we save ~130
lines of code. Small code means and less complexity means less
chance to have bugs.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch adds networks statistics that you can check via
`conntrackd -s network'. This information is useful for
trouble-shooting.
This patch replaces several log messages that can be triggered in
runtime. The idea behind this patch is to avoid log message flooding
under errors.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch reduces the size of alive messages by removing the
"from" and "to" fields which are not of any help. This patch also
removes the IS_CTL() macro since it does not return true for
the control messages anymore but only for IS_ACK(), IS_NACK() and
IS_RESYNC().
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch adds more strict checking in the message type. We add a
new message type NET_T_CTL for control messages.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch includes resync messages in the tx queue. Thus, if a
resync message gets lost, it is resent.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch removes a IS_DATA(net) in tx_queue_xmit which is not
possible to happen anymore since there are no chances to have
data in the transmission queue (instead it is all in the
transmission list).
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch replaces the use of NFCT_Q_* in the message type by
specific network message type NET_T_*. The query types are reserved
for libnetfilter_conntrack operations.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch simplifies the message format of the replication
messages. As a result, we save four bytes. The netpld header
was introduced in the early protocol design. Today, it does
not have any reason to exist.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch simplifies mcast_buffered_send_netmsg() by removing the
length parameter. Instead, we use the length field in the nethdr
to know the message size to be sent.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch removes a forced run of the transmission queue.
This is not required since we currently have an event descriptor
that indicates when to give a queue run to push pending messages.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch adds the version field (8-bits long) to the nethdr
structure. This fields can be used to indicate the protocol version
in case that we detect an incompatibility between two conntrackd
daemons working with different protocol versions.
Unfortunately, this patch breaks backward compatibility, ie.
conntrackd <= 0.9.8 protocol is not compatible with the upcoming
conntrackd >= 0.9.9. Better do this now than later.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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Since the resend list/queue contain elements in order, we can break
looping once we find the first element that is after the ack/nack
window. This patch fixes a bottleneck in the ack/nack handling
reported by oprofile.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch introduces the option `-v' to show useful debugging
information, if any. As for now, only sync-ftfw.c make use of it to
display the content and the length of the resent list/queue. This
is useful to check for message leaks. Other working modes or
synchronization approaches may use it to display debugging
information in the future.
This patch removes _SIGNAL_DEBUG in sync-ftfw.c that was used for
for the same purpose. However, it could only be enabled at compilation
time and it uses signalling instead of the standard UNIX socket
interface that conntrackd provides.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This fixes two bugs when a hello message is received:
* We can create malformed nack messages during the helloing.
We have to reset the acknowlegdment window, otherwise we may
create malformed nack messages.
* We have to empty the resend list/queue when a hello message is
received, otherwise the entries get stuck to the resend queue
once the sequence number wraps around.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch fixes a race condition that can prevent one node from sending
the initial hello message required to reset the sequence tracking.
node A node B
| |
start | |
hello msg |----------------------->|
stop | |
start | |
|<-----------------------| hello-back msg
In the picture above, the node A never sends the hello messages. Thus,
the node B drops the next messages as they are in the before boundary.
This patch adds a new state to the the helloing state-machine to fix
this problem.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch fixes a race condition that can trigger a double
insertion to the tx_list. This happens if we receive two resync
request very close or resync just after a nack or vice-versa.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patches fixes a race that triggers a read-after-free access
to the tx_list. The state-entry is destroyed but it is still in the
list. The fix removes the state-entry from the tx_list in the destroy
path.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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Remove useless debug messages, now we have a pluging for tcpdump to
debug the FT-FW protocol.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This patch checks that the [from, to] interval of ack and nack messages
is OK. In other words, we check that: to >= from
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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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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use size_t
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remove init_alarm() before add_alarm()
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merge mod_alarm() into add_alarm(), remove alarm_set_expiration()
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