NAME

SYNOPSIS

DESCRIPTION

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 single 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.

Where more than one firewall might actively handle packets, e.g. with certain ospfd(8), bgpd(8) or carp(4) configurations, it is beneficial to defer transmission of the initial packet of a connection. The pfsync state insert message is sent immediately; the packet is queued until either this message is acknowledged by another system, or a timeout has expired. This behaviour is enabled with the defer parameter to ifconfig(8).

NETWORK SYNCHRONISATION

# ifconfig fxp0 inet 172.19.13.1/28
# ifconfig pfsync0 syncdev fxp0

By default, state change messages are sent out on the synchronisation interface using IP multicast packets to the 224.0.0.240 group address. An alternative destination address for pfsync packets can be specified using the syncpeer keyword.

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 packets which create states, bypassing the pf ruleset. Only run the pfsync protocol on a trusted network - ideally a network dedicated to pfsync messages such as a crossover cable between two firewalls.

EXAMPLES

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 interfaces are configured as follows (firewall A unless otherwise indicated):

/etc/hostname.sis0:

/etc/hostname.sis1:

/etc/hostname.sis2:

/etc/hostname.carp0:

inet 10.0.0.1 255.255.255.0 10.0.0.255 \
	vhid 1 carpdev sis0 pass foo

/etc/hostname.carp1:

inet 192.168.0.1 255.255.255.0 192.168.0.255 \
	vhid 2 carpdev sis1 pass bar

/etc/hostname.pfsync0:

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) interfaces should be set to something higher than the primary's. For example, if firewall B is the backup, its /etc/hostname.carp1 would look like this:

inet 192.168.0.1 255.255.255.0 192.168.0.255 \
	vhid 2 pass bar advskew 100

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

net.inet.carp.preempt=1

SEE ALSO

HISTORY

The pfsync protocol and kernel implementation were significantly modified between OpenBSD 4.4 and OpenBSD 4.5. The two protocols are incompatible and will not interoperate.

BUGS