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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 alive control message to the notrack mode.
This helps to diagnose problems in the synchronization and
the state of the channel, specifically for TCP-based channels.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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In 9406f29b89f6727c3db5485d109466701393b4d4, we added different
return values for the UNIX sockets that we use to extract the
daemon statistics. Unfortunately, I forgot to change this
as well. This patch fixes a problem that blocks the client
socket indefinitely.
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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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 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 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 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 fixes double insertion in the tx_list if we receive
two (or more) consecutive resync request in short time.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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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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- add len field to nethdr
- implement buffered send/recv to batch messages
- stop using netlink format for network messages: use similar TLV-based format
- reduce synchronization messages size up to 60%
- introduce periodic alive messages for sync-nack protocol
- timeslice alarm implementation: remove alarm pthread, remove locking
- simplify debugging functions: use nfct_snprintf instead
- remove major use of libnfnetlink functions: use libnetfilter_conntrack API
- deprecate conntrackd -F, use conntrack -F instead
- major rework of the network infrastructure: much simple, less messy
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- remove several debug calls
- create a child to dispatch dump requests: this will help to simplify the
current locking schema. Later.
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o remove reminiscents of delay destroy message and relax transitions
o remove confusing StripNAT parameter: NAT support enabled by default
o relax event tracking: *_update callbacks use cache_update_force
o use wraparound-aware functions after/before/between
o lots of cleanups
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- flush nack queue in the conntrackd -f path
- do not increase add_fail counter for EEXIST errors
- cleanup sync-nack code
- improve mcast_recv_netmsg: sanity check before checksumming!
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