PFSYNC(4)						   BSD Kernel Interfaces Manual 						 PFSYNC(4)

NAME

     pfsync -- packet filter state table sychronisation interface

SYNOPSIS

     device pfsync

DESCRIPTION

     The pfsync interface is a pseudo-device which exposes certain changes to the state table used by pf(4).  State changes can be viewed by
     invoking tcpdump(1) on the pfsync interface.  If configured with a physical synchronisation interface, pfsync will also send state changes
     out on that interface, and insert state changes received on that interface from other systems into the state table.

     By default, all local changes to the state table are exposed via pfsync.  State changes from packets received by pfsync over the network are
     not rebroadcast.  Updates to states created by a rule marked with the no-sync keyword are ignored by the pfsync interface (see pf.conf(5) for
     details).

     The pfsync interface will attempt to collapse multiple state updates into a single packet where possible.	The maximum number of times a sin-
     gle state can be updated before a pfsync packet will be sent out is controlled by the maxupd parameter to ifconfig (see ifconfig(8) and the
     example below for more details).  The sending out of a pfsync packet will be delayed by a maximum of one second.

NETWORK SYNCHRONISATION

     States can be synchronised between two or more firewalls using this interface, by specifying a synchronisation interface using ifconfig(8).
     For example, the following command sets fxp0 as the synchronisation interface:

	   # ifconfig pfsync0 syncdev fxp0

     By default, state change messages are sent out on the synchronisation interface using IP multicast packets to the 244.0.0.240 group address.
     An alternative destination address for pfsync packets can be specified using the syncpeer keyword.  This can be used in combination with
     ipsec(4) to protect the synchronisation traffic.  In such a configuration, the syncdev should be set to the enc(4) interface, as this is
     where the traffic arrives when it is decapsulated, e.g.:

	   # ifconfig pfsync0 syncpeer 10.0.0.2 syncdev enc0

     It is important that the pfsync traffic be well secured as there is no authentication on the protocol and it would be trivial to spoof pack-
     ets which create states, bypassing the pf ruleset.  Either run the pfsync protocol on a trusted network - ideally a network dedicated to
     pfsync messages such as a crossover cable between two firewalls, or specify a peer address and protect the traffic with ipsec(4).

     pfsync has the following sysctl(8) tunables:

     net.pfsync.carp_demotion_factor
		 Value added to net.inet.carp.demotion while pfsync tries to perform its bulk update.  See carp(4) for more information.  Default
		 value is 240.

EXAMPLES

     pfsync and carp(4) can be used together to provide automatic failover of a pair of firewalls configured in parallel.  One firewall will han-
     dle all traffic until it dies, is shut down, or is manually demoted, at which point the second firewall will take over automatically.

     Both firewalls in this example have three sis(4) interfaces.  sis0 is the external interface, on the 10.0.0.0/24 subnet; sis1 is the internal
     interface, on the 192.168.0.0/24 subnet; and sis2 is the pfsync interface, using the 192.168.254.0/24 subnet.  A crossover cable connects the
     two firewalls via their sis2 interfaces.  On all three interfaces, firewall A uses the .254 address, while firewall B uses .253.  The inter-
     faces are configured as follows (firewall A unless otherwise indicated):

     Interfaces configuration in /etc/rc.conf:

	   network_interfaces="lo0 sis0 sis1 sis2"
	   ifconfig_sis0="10.0.0.254/24"
	   ifconfig_sis0_alias0="inet 10.0.0.1/24 vhid 1 pass foo"
	   ifconfig_sis1="192.168.0.254/24"
	   ifconfig_sis1_alias0="inet 192.168.0.1/24 vhid 2 pass bar"
	   ifconfig_sis2="192.168.254.254/24"
	   pfsync_enable="YES"
	   pfsync_syncdev="sis2"

     pf(4) must also be configured to allow pfsync and carp(4) traffic through.  The following should be added to the top of /etc/pf.conf:

	   pass quick on { sis2 } proto pfsync keep state (no-sync)
	   pass on { sis0 sis1 } proto carp keep state (no-sync)

     It is preferable that one firewall handle the forwarding of all the traffic, therefore the advskew on the backup firewall's carp(4) vhids
     should be set to something higher than the primary's.  For example, if firewall B is the backup, its carp1 configuration would look like
     this: would look like this:

	   ifconfig_sis1_alias0="inet 192.168.0.1/24 vhid 2 pass bar advskew 100"

     The following must also be added to /etc/sysctl.conf:

	   net.inet.carp.preempt=1

SEE ALSO

     tcpdump(1), bpf(4), carp(4), enc(4), inet(4), inet6(4), ipsec(4), netintro(4), pf(4), pf.conf(5), protocols(5), rc.conf(5), ifconfig(8)

HISTORY

     The pfsync device first appeared in OpenBSD 3.3.  It was first imported to FreeBSD 5.3.

     The pfsync protocol and kernel implementation were significantly modified in FreeBSD 9.0.	The newer protocol is not compatible with older
     one and will not interoperate with it.

BSD
								 December 20, 2011							       BSD