Provided by: conntrackd_1.4.6-2build2_amd64 
NAME
conntrackd.conf - configuration file for conntrackd daemon
DESCRIPTION
conntrackd.conf is the main configuration file for the conntrackd(8) daemon. It is loaded by calling
`conntrackd -C conntrackd.conf'.
The format of this file is simple, using brackets for sections and key-value pairs for concrete
configuration directives:
section1 {
option1 value1
option2 value2
}
section2 {
option3 value3
subsection1 {
option4 value4
}
}
You should consider this file as case-sensitive. Empty lines and lines starting with the '#' character
are ignored.
Before starting to develop a new configuration, you may want to learn the concepts behind this technlogy
at http://conntrack-tools.netfilter.org/manual.html.
There are complete configuration examples at the end of this man page.
SYNC
This top-level section defines how conntrackd(8) should handle synchronization with other cluster nodes.
There are 3 main synchronization modes or protocols: NOTRACK, ALARM and FTFW.
There are 3 transport protocols as well: TCP, Multicast and UDP.
You have to choose one synchronization mode and one transport protocol.
Also, there are some general options in this section.
Mode FTFW
This mode is based on a reliable protocol that performs message tracking. Thus, the protocol can recover
from message loss, re-ordering and corruption.
In this synchronization mode you may configure ResendQueueSize, CommitTimeout, PurgeTimeout,
ACKWindowSize , DisableExternalCache and StartupResync.
ResendQueueSize <value>
Size of the resend queue (in objects). This is the maximum number of objects that can be stored
waiting to be confirmed via acknoledgment. If you keep this value low, the daemon will have less
chances to recover state-changes under message omission. On the other hand, if you keep this value
high, the daemon will consume more memory to store dead objects.
Example: ResendQueueSize 131072
Default is 131072 objects.
CommitTimeout <seconds>
This parameter allows you to set an initial fixed timeout for the committed entries when this node
goes from backup to primary. This mechanism provides a way to purge entries that were not
recovered appropriately after the specified fixed timeout. If you set a low value, TCP entries in
Established states with no traffic may hang. For example, an SSH connection without KeepAlive
enabled.
Example: CommitTimeout 180
By default, this option is not set (the daemon uses an approximate timeout value calculation
mechanism).
PurgeTimeout <seconds>
If the firewall replica goes from primary to backup, the `conntrackd -t command' is invoked in the
script. This command schedules a flush of the table in N seconds.
This is useful to purge the connection tracking table of zombie entries and avoid clashes with old
entries if you trigger several consecutive hand-overs.
Default is 60 seconds.
ACKWindowSize <value>
Set the acknowledgement window size. If you decrease this value, the number of acknowlegdments
increases. More acknowledgments means more overhead as conntrackd(8) has to handle more control
messages. On the other hand, if you increase this value, the resend queue gets more populated.
This results in more overhead in the queue releasing.
Example: ACKWindowSize 300
If not set, default window size is 300 (value is based on some practical experiments measuring the
cycles spent by the acknowledgment handling with oprofile).
DisableExternalCache <on|off>
This clause allows you to disable the external cache. Thus, the state entries are directly
injected into the kernel conntrack table. As a result, you save memory in user-space but you
consume slots in the kernel conntrack table for backup state entries. Moreover, disabling the
external cache means more CPU consumption. You need a Linux kernel >= 2.6.29 to use this feature.
If you are installing conntrackd(8) for first time, please read the user manual and I encourage
you to consider using the fail-over scripts instead of enabling this option!
By default, this clause is set off.
StartupResync <on|off>
Order conntrackd to request a complete conntrack table resync against the other node at startup. A
single request will be made.
This is useful to get in sync with another node which has been running while we were down.
Example: StartupResync on
By default, this clause is set off.
Mode ALARM
This mode is spamming. It is based on a alarm-based protocol that periodically re-sends the flow state to
the backup firewall replicas. This protocol consumes a lot of bandwidth but it resolves synchronization
problems fast.
In this synchronization mode you may configure RefreshTime, CacheTimeout, CommitTimeout and PurgeTimeout.
RefreshTime <seconds>
If a conntrack entry is not modified in <= N seconds, then a message is broadcasted. For example,
this mechanism may be used to resynchronize nodes that just joined the multicast group.
Example: RefreshTime 15
CacheTimeout <seconds>
If we don't receive a notification about the state of an entry in the external cache after N
seconds, then remove it.
Example: CacheTimeout 180
CommitTimeout <seconds>
Same as in FTFW mode.
PurgeTimeout <seconds>
Same as in FTFW mode.
Mode NOTRACK
Is the most simple mode as it is based on a best effort replication protocol, ie. unreliable protocol.
This protocol sends and receives the state information without performing any specific checking.
In this synchronization mode you may configure DisableInternalCache, DisableExternalCache, CommitTimeout,
PurgeTimeout and StartupResync.
DisableInternalCache <on|off>
This clause allows you to disable the internal cache. Thus, the synchronization messages are
directly sent through the dedicated link.
This option is set off by default.
DisableExternalCache <on|off>
Same as in FTFW mode.
CommitTimeout <seconds>
Same as in FTFW mode.
PurgeTimeout <seconds>
Same as in FTFW mode.
StartupResync <on|off>
Same as in FTFW mode.
MULTICAST
This section indicates to conntrackd(8) to use multicast as transport mechanism between nodes of the
firewall cluster.
Please note you can specify more than one dedicated link. Thus, if one dedicated link fails, the daemon
can fail-over to another. Note that adding more than one dedicated link does not mean that state-updates
will be sent to all of them. There is only one active dedicated link at a given moment.
The Default keyword indicates that this interface will be selected as the initial dedicated link. You can
have up to 4 redundant dedicated links.
Note: use different multicast groups for every redundant link.
Example:
Multicast Default {
IPv4_address 225.0.0.51
Group 3781
IPv4_interface 192.168.100.101
Interface eth3
SndSocketBuffer 1249280
RcvSocketBuffer 1249280
Checksum on
}
Multicast {
IPv4_address 225.0.0.51
Group 3782
IPv4_interface 192.168.100.102
Interface eth4
SndSocketBuffer 1249280
RcvSocketBuffer 1249280
Checksum on
}
IPv4_address <address>
Multicast address: The address that you use as destination in the synchronization messages. You do
not have to add this IP to any of your existing interfaces.
Example: IPv4_address 255.0.0.50
Group <number>
The multicast group that identifies the cluster.
Example: Group 3780
If any doubt, do not modify this value.
IPv4_interface <address>
IP address of the interface that you are going to use to send the synchronization messages.
Remember that you must use a dedicated link for the synchronization messages.
Example: IPv4_interface 192.168.100.100
Interface <name>
The name of the interface that you are going to use to send the synchronization messages.
Example: Interface eth2
SndSocketBuffer <number>
This transport protocol sender uses a buffer to enqueue the packets that are going to be
transmitted. The default size of this socket buffer is available at
/proc/sys/net/core/wmem_default.
This value determines the chances to have an overrun in the sender queue. The overrun results in
packet loss, thus, losing state information that would have to be retransmitted. If you notice
some packet loss, you may want to increase the size of the buffer. The system default size is
usually around ~100 KBytes which is fairly small for busy firewalls.
Note: The NOTRACK protocol is best effort, it is really recommended to increase the buffer size.
Example: SndSocketBuffer 1249280
RcvSocketBuffer <number>
This transport protocol receiver uses a buffer to enqueue the packets that the socket is pending
to handle. The default size of this socket buffer is available at /proc/sys/net/core/rmem_default.
This value determines the chances to have an overrun in the receiver queue. The overrun results
in packet loss, thus, losing state information that would have to be retransmitted. If you notice
some packet loss, you may want to increase the size of the buffer. The system default size is
usually around ~100 KBytes which is fairly small for busy firewalls.
Note: The NOTRACK protocol is best effort, it is really recommended to increase the buffer size.
Example: RcvSocketBuffer 1249280
Checksum <on|off>
Enable/Disable message checksumming. This is a good property to achieve fault-tolerance. In case
of doubt, use it.
UDP
This section indicates to conntrackd(8) to use UDP as transport mechanism between nodes of the firewall
cluster.
As in the Multicast configuration, you may especify several fail-over dedicated links using the Default
keyword.
Example:
UDP {
IPv4_address 172.16.0.1
IPv4_Destination_Address 172.16.0.2
Port 3781
Interface eth3
SndSocketBuffer 1249280
RcvSocketBuffer 1249280
Checksum on
}
IPv4_address <address>
UDP IPv4 address that this firewall uses to listen to events.
Example: IPv4_address 192.168.2.100
IPv6_address <address>
UDP IPv6 address that this firewall uses to listen to events.
Example: IPv6_address fe80::215:58ff:fe28:5a27
IPv4_Destination_Address <address>
Destination IPv4 UDP address that receives events, ie. the other firewall's dedicated link
address.
Example: IPv4_Destination_Address 192.168.2.101
IPv6_Destionation_Address <address>
Destination IPv6 UDP address that receives events, ie. the other firewall's dedicated link
address.
Example: IPv6_Destination_Address fe80::2d0:59ff:fe2a:775c
Port <number>
UDP port used
Example: Port 3780
Interface <name>
Same as in the Multicast transport protocol configuration.
SndSocketBuffer <number>
Same as in the Multicast transport protocol configuration.
RcvSocketBuffer <number>
Same as in the Multicast transport protocol configuration.
Checksum <on|off>
Same as in the Multicast transport protocol configuration.
TCP
You can also use Unicast TCP to propagate events.
If you combine this transport with the NOTRACK mode, it becomes reliable.
The TCP transport protocol can be configured in exactly the same way as the UDP transport protocol.
As in the Multicast configuration, you may especify several fail-over dedicated links using the Default
keyword.
Example:
TCP {
IPv6_address fe80::215:58ff:fe28:5a27
IPv6_Destination_Address fe80::215:58ff:fe28:5a27
Port 3781
Interface eth2
SndSocketBuffer 1249280
RcvSocketBuffer 1249280
Checksum on
}
OPTIONS
Other unsorted options that are related to the synchronization protocol or transport mechanism.
TCPWindowTracking <on|off>
TCP state-entries have window tracking disabled by default, you can enable it with this option. As
said, default is off. This feature requires a Linux kernel >= 2.6.36.
ExpectationSync <on|{ list }>
Set this option on if you want to enable the synchronization of expectations. You have to specify
the list of helpers that you want to enable.
This feature requires a Linux kernel >= 3.5.
Example, sync all expectations:
ExpectationSync on
Example, sync given expectations:
ExpectationSync {
ftp
ras
q.931
h.245
sip
}
By default, this option is disabled.
GENERAL
This top-level section contains generic configuration directives for the conntrackd(8) daemon.
Systemd <on|off>
Enable systemd(1) runtime support if conntrackd(8) is compiled with the proper configuration. Then
you can use a service unit of Type=notify.
Obviously, this requires the init of your system to be systemd(1).
Note: systemd(1) watchdog is supported as well.
Example: Systemd on
By default runtime support is enabled if conntrackd was built with the systemd feature. Otherwise
is off.
Nice <value>
Deprecated. Conntrackd ignores this option and it will be removed in the future. Please note that
you can run nice(1) and renice(1) externally. Also note that conntrackd(8) now uses by default a
RT scheduler.
HashSize <value>
Number of buckets in the cache hashtable. The bigger it is, the closer it gets to O(1) at the cost
of consuming more memory. Read some documents about tuning hashtables for further reference.
Example: HashSize 32768
HashLimit <value>
Maximum number of conntracks, it should be double of /proc/sys/net/netfilter/nf_conntrack_max
since the daemon may keep some dead entries cached for possible retransmission during state
synchronization.
Example: HashLimit 131072
LogFile <on|off|filename>
Enable conntrackd(8) to log to a file.
Example: LogFile on
Default is off. The default logfile is /var/log/conntrackd.log.
Syslog <on|off|facility>
Enable connection logging via Syslog. If you set the facility, use the same as in the Stats
section, otherwise you'll get a warning message.
Example: Syslog local0
Default is off.
Lockfile <filename>
Lockfile to be used by conntrackd(8) (absolute path).
Example: LockFile /var/lock/conntrack.lock
Default is /var/lock/conntrack.lock.
NetlinkBufferSize <value>
Netlink event socket buffer size. If you do not specify this clause, the default buffer size value
in /proc/sys/net/core/rmem_default is used. This default value is usually around 100 Kbytes which
is fairly small for busy firewalls. This leads to event message dropping and high CPU consumption.
Example: NetlinkBufferSize 2097152
NetlinkBufferSizeMaxGrowth <value>
The daemon doubles the size of the netlink event socket buffer size if it detects netlink event
message dropping. This clause sets the maximum buffer size growth that can be reached.
Example: NetlinkBufferSizeMaxGrowth 8388608
NetlinkOverrunResync <on|off|value>
If the daemon detects that Netlink is dropping state-change events, it automatically schedules a
resynchronization against the Kernel after 30 seconds (default value). Resynchronizations are
expensive in terms of CPU consumption since the daemon has to get the full kernel state-table and
purge state-entries that do not exist anymore.
Note: Be careful of setting a very small value here.
Example: NetlinkOverrunResync on
The default value is 30 seconds. If not specified, the daemon assumes that this option is enabled
and uses the default value.
NetlinkEventsReliable <on|off>
If you want reliable event reporting over Netlink, set on this option. If you set on this clause,
it is a good idea to set off NetlinkOverrunResync.
You need Linux Kernel >= 2.6.31 for this option to work.
Example: NetlinkEventsReliable on
This option is off by default.
PollSecs <seconds>
By default, the daemon receives state updates following an event-driven model. You can modify
this behaviour by switching to polling mode with this clause.
This clause tells conntrackd(8) to dump the states in the kernel every N seconds. With regards to
synchronization mode, the polling mode can only guarantee that long-lifetime states are recovered.
The main advantage of this method is the reduction in the state replication at the cost of
reducing the chances of recovering connections.
Example: PollSecs 15
EventIterationLimit <value>
The daemon prioritizes the handling of state-change events coming from the core. With this clause,
you can set the maximum number of state-change events (those coming from kernel-space) that the
daemon will handle after which it will handle other events coming from the network or userspace.
A low value improves interactivity (in terms of real-time behaviour) at the cost of extra CPU
consumption.
Example: EventIterationLimit 100
Default (if not set) is 100.
UNIX
Unix socket configuration. This socket is used by conntrackd(8) to listen to external commands like
`conntrackd -k' or `conntrackd -n'.
Example:
UNIX {
Path /var/run/conntrackd.ctl
}
Path <filename>
Absolute path to the Unix socket.
Example: Path /var/run/conntrackd.ctl
Backlog <value>
Deprecated option.
FILTER
Event filtering. This clause allows you to filter certain traffic.
There are currently three filter-sets: Protocol, Address and State. The filter is attached to an action
that can be: Accept or Ignore. Thus, you can define the event filtering policy of the filter-sets in
positive or negative logic depending on your needs.
You can select if conntrackd(8) filters the event messages from user-space or kernel-space. The kernel-
space event filtering saves some CPU cycles by avoiding the copy of the event message from kernel-space
to user-space. The kernel-space event filtering is prefered, however, you require a Linux kernel >=
2.6.29 to filter from kernel-space.
The syntax for this section is: Filter From <from> { }.
If you want to select kernel-space event filtering, use the keyword Kernelspace instead of Userspace.
Example:
Filter From Userspace {
Protocol Accept {
TCP
SCTP
DCCP
}
Address Ignore {
IPv4_address 127.0.0.1
IPv6_address ::1
}
State Accept {
ESTABLISHED CLOSED TIME_WAIT CLOSE_WAIT for TCP
}
}
Protocol <policy> { <protocols list> }
Accept only certain protocols: You may want to replicate the state of flows depending on their
layer 4 protocol.
Policy is one of Accept or Ignore.
Protocols are: TCP, SCTP, DCCP, UDP, ICMP and IPv6-ICMP.
The ICMP and IPv6-ICMP protocols require a Linux kernel >= 2.6.31.
Example:
Protocol Accept {
TCP
SCTP
DCCP
}
Address <policy> { <addresses list> }
Ignore traffic for a certain set of IP's: Usually all the IP assigned to the firewall since local
traffic must be ignored, only forwarded connections are worth to replicate.
Note that these values depends on the local IPs that are assigned to the firewall.
You may specify several IPv4_address and/or IPv6_address directives. You can also specify networks
in CIDR format.
Policy is one of Accept or Ignore.
Example:
Address Ignore {
IPv4_address 127.0.0.1 # loopback
IPv4_address 192.168.0.100 # virtual IP 1
IPv4_address 192.168.1.100 # virtual IP 2
IPv4_address 192.168.100.100 # dedicated link ip
IPv4_address 192.168.0.0/24
IPv6_address ::1
}
State <policy> { <states list> for TCP }
Filter by flow state. This option introduces a trade-off in the replication: it reduces CPU
consumption at the cost of having lazy backup firewall replicas.
Note: only affects TCP flows.
The existing TCP states are: SYN_SENT, SYN_RECV, ESTABLISHED, FIN_WAIT, CLOSE_WAIT, LAST_ACK,
TIME_WAIT, CLOSED and LISTEN.
Policy is one of Accept or Ignore.
Example:
State Accept {
ESTABLISHED CLOSED TIME_WAIT CLOSE_WAIT for TCP
}
SCHEDULER
Select a different scheduler for the daemon, you can select between RR and FIFO and the process priority.
Using a RT scheduler reduces the chances to overrun the Netlink buffer and conntrackd(8) uses by default
RR unless FIFO is selected. See sched_setscheduler(2) for more information.
Example:
Scheduler {
Type FIFO
Priority 99
}
Type <type>
Supported values are RR or FIFO.
Default: RR
Priority <value>
Value of the scheduler priority. Minimum is 0, maximum is 99.
Default: 99 (as returned by sched_get_priority_max(2) for SCHED_RR)
STATS
This top-level section indicates conntrackd(8) to work as a statistic collector for the nf_conntrack
linux kernel subsystem.
LogFile <on|off|filename>
If you enable this option, the daemon writes the information about destroyed connections to a
logfile.
Default is off. Default filename is /var/log/conntrackd-stats.log.
NetlinkEventsReliable <on|off>
If you want reliable event reporting over Netlink, set on this option. If you set on this clause,
it is a good idea to set off NetlinkOverrunResync. This requires Linux kernel >= 2.6.31.
Default is off.
Syslog <on|off|facility>
Enable connection logging via Syslog. If you set the facility, use the same as in the General
section, otherwise you'll get a warning message.
Example: Syslog local0
Default is off.
HELPER
Note: this configuration is very advanced and has nothing to do with synchronization or stats collection.
This top-level section indicates conntrackd(8) to inject user-space helpers into the nf_conntrack linux
kernel subsystem. It will result in the nf_conntrack engine sending connections to userspace for further
processing.
Before this, you have to make sure you have registered the given user-space helper stub.
Example:
% nfct add helper ftp inet tcp
Each user-space helper should be registered using a Type section, which are named this way:
Type <name> <af> <transport>
Examples:
Helper {
Type ftp inet tcp {
QueueNum 0
QueueLen 10240
Policy ftp {
ExpectMax 1
ExpectTimeout 300
}
}
Type rpc inet tcp {
QueueNum 1
QueueLen 10240
Policy rpc {
ExpectMax 1
ExpectTimeout 300
}
}
Type rpc inet udp {
QueueNum 2
QueueLen 10240
Policy rpc {
ExpectMax 1
ExpectTimeout 300
}
}
Type tns inet tcp {
QueueNum 3
QueueLen 10240
Policy tns {
ExpectMax 1
ExpectTimeout 300
}
}
Type dhcpv6 inet6 udp {
QueueNum 4
QueueLen 10240
Policy dhcpv6 {
ExpectMax 1
ExpectTimeout 300
}
}
Type ssdp inet udp {
QueueNum 5
QueueLen 10240
Policy ssdp {
ExpectMax 1
ExpectTimeout 300
}
}
}
Parameters inside the Type section:
QueueNum <number>
Set NFQUEUE number you want to use to receive traffic from the kernel.
Example: QueueNum 0
QueueLen <number>
Maximum number of packets waiting in the queue to receive a verdict from user-space.
Rise value if you hit the following error message:
"nf_queue: full at X entries, dropping packet(s)"
Default is 1024.
Example: QueueLen 10240
Policy <name> { }
Set the expectation policy for the given helper.
This sub-section contains 2 directives: ExpectMax <number> (maximum number of simultaneous
expectations) and ExpecTimeout <seconds> (maximum living time for one expectation).
COMPLETE EXAMPLES
Find below some real-life working examples.
STATS EXAMPLE
This configuration example tells conntrackd(8) to work as a stats collector.
Stats {
LogFile on
NetlinkEventsReliable Off
Syslog off
}
General {
Systemd on
HashSize 8192
HashLimit 65535
Syslog on
LockFile /var/lock/conntrack.lock
UNIX {
Path /var/run/conntrackd.ctl
}
NetlinkBufferSize 262142
NetlinkBufferSizeMaxGrowth 655355
Filter {
Protocol Accept {
TCP
UDP
}
Address Ignore {
IPv4_address 127.0.0.1
IPv6_address ::1
}
}
}
SYNC EXAMPLE 1
This example configures synchronization in FTFW mode with Multicast transport.
It includes common general configuration as well.
Note: this is one of the recommended setups for conntrackd(8) in a firewall cluster environment.
Sync {
Mode FTFW {
ResendQueueSize 131072
PurgeTimeout 60
ACKWindowSize 300
DisableExternalCache Off
}
Multicast {
IPv4_address 225.0.0.50
Group 3780
IPv4_interface 192.168.100.100
Interface eth2
SndSocketBuffer 1249280
RcvSocketBuffer 1249280
Checksum on
}
Multicast Default {
IPv4_address 225.0.0.51
Group 3781
IPv4_interface 192.168.100.101
Interface eth3
SndSocketBuffer 1249280
RcvSocketBuffer 1249280
Checksum on
}
Options {
TCPWindowTracking Off
ExpectationSync On
}
}
General {
Systemd on
HashSize 32768
HashLimit 131072
LogFile on
Syslog off
LockFile /var/lock/conntrack.lock
UNIX {
Path /var/run/conntrackd.ctl
}
NetlinkBufferSize 2097152
NetlinkBufferSizeMaxGrowth 8388608
NetlinkOverrunResync On
NetlinkEventsReliable Off
EventIterationLimit 100
Filter From Userspace {
Protocol Accept {
TCP
SCTP
DCCP
}
Address Ignore {
IPv4_address 127.0.0.1
IPv4_address 192.168.100.0/24
IPv6_address ::1
}
}
}
SYNC EXAMPLE 2
This example configures synchronization in NOTRACK mode with TCP transport.
It includes common general configuration as well.
Sync {
Mode NOTRACK {
DisableInternalCache on
DisableExternalCache on
}
TCP {
IPv4_address 192.168.2.100
IPv4_Destination_Address 192.168.2.101
Port 3780
Interface eth2
SndSocketBuffer 1249280
RcvSocketBuffer 1249280
Checksum on
}
Options {
TCPWindowTracking Off
ExpectationSync On
}
}
General {
Systemd on
HashSize 32768
HashLimit 131072
LogFile on
Syslog off
LockFile /var/lock/conntrack.lock
UNIX {
Path /var/run/conntrackd.ctl
}
NetlinkBufferSize 2097152
NetlinkBufferSizeMaxGrowth 8388608
NetlinkOverrunResync On
NetlinkEventsReliable Off
EventIterationLimit 100
Filter From Userspace {
Protocol Accept {
TCP
SCTP
DCCP
}
Address Ignore {
IPv4_address 127.0.0.1
IPv4_address 192.168.0.0/16
IPv6_address ::1
}
State Accept {
ESTABLISHED CLOSED TIME_WAIT CLOSE_WAIT for TCP
}
}
}
SEE ALSO
conntrackd(8), conntrack(8), nfct(8), http://conntrack-tools.netfilter.org/manual.html
AUTHOR
Pablo Neira Ayuso wrote and maintains the conntrackd tool.
This manual page was written by Arturo Borrero Gonzalez <arturo@debian.org> based on the conntrackd
tarball config examples.
Please send bug reports to <netfilter-devel@lists.netfilter.org>. Subscription is required.
This documentation is free/libre under the terms of the GPLv2+.
Jan 27, 2019 CONNTRACKD.CONF(5)