NAME

pfsync – packet filter state table sychronisation interface

SYNOPSIS

pseudo-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(8) on the pfsync interface.  If configured with a physical syn-

chronisation 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 single

state can be updated before a pfsync packet will be sent out is con-

trolled by the maxupd parameter to ifconfig (see ifconfig(8) and the ex-

ample 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 benefical to

defer transmission of the initial packet of a connection.  The pfsync

state insert message is sent immediately; the packet is queued until ei-

ther this message is acknowledged by another system, or a timeout has ex-

pired.  This behaviour is enabled with the defer parameter to

ifconfig(8).

NETWORK SYNCHRONISATION

States can be synchronised between two or more firewalls using this in-

terface, by specifying a synchronisation interface using ifconfig(8).

For example, the following command configures an address on fxp0 and sets

it as the synchronisation interface:

# ifconfig fxp0 inet 172.19.13.1/28

# ifconfig pfsync0 syncdev fxp0

By default, state change messages are sent out on the synchronisation in-

terface 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 traf-

fic 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 packets

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).

EXAMPLES

pfsync and carp(4) can be used together to provide automatic failover of

a pair of firewalls configured in parallel.  One firewall will handle 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 in-

terface, 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:

inet 10.0.0.254 255.255.255.0 NONE

/etc/hostname.sis1:

inet 192.168.0.254 255.255.255.0 NONE

/etc/hostname.sis2:

inet 192.168.254.254 255.255.255.0 NONE

/etc/hostname.carp0:

inet 10.0.0.1 255.255.255.0 10.0.0.255 vhid 1 pass foo

/etc/hostname.carp1:

inet 192.168.0.1 255.255.255.0 192.168.0.255 vhid 2 pass bar

/etc/hostname.pfsync0:

up 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 traf-

fic, 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

bpf(4), carp(4), enc(4), inet(4), inet6(4), ipsec(4), netintro(4), pf(4),

hostname.if(5), pf.conf(5), protocols(5), ifconfig(8), ifstated(8),

tcpdump(8)

NAME     pfsync – packet filter state table sychronisation interface

SYNOPSIS     pseudo-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(8) on the pfsync interface.  If configured with a physical syn-     chronisation 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 single     state can be updated before a pfsync packet will be sent out is con-     trolled by the maxupd parameter to ifconfig (see ifconfig(8) and the ex-     ample 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 benefical to     defer transmission of the initial packet of a connection.  The pfsync     state insert message is sent immediately; the packet is queued until ei-     ther this message is acknowledged by another system, or a timeout has ex-     pired.  This behaviour is enabled with the defer parameter to     ifconfig(8).

NETWORK SYNCHRONISATION     States can be synchronised between two or more firewalls using this in-     terface, by specifying a synchronisation interface using ifconfig(8).     For example, the following command configures an address on fxp0 and sets     it as the synchronisation interface:

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

By default, state change messages are sent out on the synchronisation in-     terface 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 traf-     fic 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 packets     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).

EXAMPLES     pfsync and carp(4) can be used together to provide automatic failover of     a pair of firewalls configured in parallel.  One firewall will handle 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 in-     terface, 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:

inet 10.0.0.254 255.255.255.0 NONE

/etc/hostname.sis1:

inet 192.168.0.254 255.255.255.0 NONE

/etc/hostname.sis2:

inet 192.168.254.254 255.255.255.0 NONE

/etc/hostname.carp0:

inet 10.0.0.1 255.255.255.0 10.0.0.255 vhid 1 pass foo

/etc/hostname.carp1:

inet 192.168.0.1 255.255.255.0 192.168.0.255 vhid 2 pass bar

/etc/hostname.pfsync0:

up 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 traf-     fic, 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     bpf(4), carp(4), enc(4), inet(4), inet6(4), ipsec(4), netintro(4), pf(4),     hostname.if(5), pf.conf(5), protocols(5), ifconfig(8), ifstated(8),     tcpdump(8)