.\" $OpenBSD: pfsync.4,v 1.22 2005/02/24 15:53:17 jmc Exp $ .\" .\" Copyright (c) 2002 Michael Shalayeff .\" Copyright (c) 2003-2004 Ryan McBride .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF MIND, .\" USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. .\" .Dd November 29, 2002 .Dt PFSYNC 4 .Os .Sh NAME .Nm pfsync .Nd packet filter state table logging interface .Sh SYNOPSIS .Cd "pseudo-device pfsync" .Sh DESCRIPTION The .Nm interface is a pseudo-device which exposes certain changes to the state table used by .Xr pf 4 . State changes can be viewed by invoking .Xr tcpdump 8 on the .Nm interface. If configured with a physical synchronisation interface, .Nm will also send state changes out on that interface using IP multicast, and insert state changes received on that interface from other systems into the state table. .Pp By default, all local changes to the state table are exposed via .Nm . However, state changes from packets received by .Nm over the network are not rebroadcast. States created by a rule marked with the .Ar no-sync keyword are omitted from the .Nm interface (see .Xr pf.conf 5 for details). .Pp The .Nm interface will attempt to collapse multiple updates of the same state into one message where possible. The maximum number of times this can be done before the update is sent out is controlled by the .Ar maxupd parameter to ifconfig (see .Xr ifconfig 8 and the example below for more details). .Pp Each packet retrieved on this interface has a header associated with it of length .Dv PFSYNC_HDRLEN . The header indicates the version of the protocol, address family, action taken on the following states, and the number of state table entries attached in this packet. This structure is defined in .Aq Pa net/if_pfsync.h as: .Bd -literal -offset indent struct pfsync_header { u_int8_t version; u_int8_t af; u_int8_t action; u_int8_t count; }; .Ed .Sh NETWORK SYNCHRONISATION States can be synchronised between two or more firewalls using this interface, by specifying a synchronisation interface using .Xr ifconfig 8 . For example, the following command sets fxp0 as the synchronisation interface: .Bd -literal -offset indent # ifconfig pfsync0 syncdev fxp0 .Ed .Pp By default, state change messages are sent out on the synchronisation interface using IP multicast packets. The protocol is IP protocol 240, PFSYNC, and the multicast group used is 224.0.0.240. When a peer address is specified using the .Ic syncpeer keyword, the peer address is used as a destination for the pfsync traffic, and the traffic can then be protected using .Xr ipsec 4 . In such a configuration, the syncdev should be set to the .Xr enc 4 interface, as this is where the traffic arrives when it is decapsulated, e.g.: .Bd -literal -offset indent # ifconfig pfsync0 syncpeer 10.0.0.2 syncdev enc0 .Ed .Pp 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 .Xr ipsec 4 . .Pp There is a one-to-one correspondence between packets seen by .Xr bpf 4 on the .Nm interface, and packets sent out on the synchronisation interface, i.e.\& a packet with 4 state deletion messages on .Nm means that the same 4 deletions were sent out on the synchronisation interface. However, the actual packet contents may differ as the messages sent over the network are "compressed" where possible, containing only the necessary information. .Sh EXAMPLES .Nm and .Xr carp 4 can be used together to provide automatic failover of a pair of firewalls configured in parallel. One firewall handles all traffic \- if it dies or is shut down, the second firewall takes over automatically. .Pp Both firewalls in this example have three .Xr 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 .Nm 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): .Pp .Pa /etc/hostname.sis0 : .Bd -literal -offset indent inet 10.0.0.254 255.255.255.0 NONE .Ed .Pp .Pa /etc/hostname.sis1 : .Bd -literal -offset indent inet 192.168.0.254 255.255.255.0 NONE .Ed .Pp .Pa /etc/hostname.sis2 : .Bd -literal -offset indent inet 192.168.254.254 255.255.255.0 NONE .Ed .Pp .Pa /etc/hostname.carp0 : .Bd -literal -offset indent inet 10.0.0.1 255.255.255.0 10.0.0.255 vhid 1 pass foo .Ed .Pp .Pa /etc/hostname.carp1 : .Bd -literal -offset indent inet 192.168.0.1 255.255.255.0 192.168.0.255 vhid 2 pass bar .Ed .Pp .Pa /etc/hostname.pfsync0 : .Bd -literal -offset indent up syncdev sis2 .Ed .Pp .Xr pf 4 must also be configured to allow .Nm and .Xr carp 4 traffic through. The following should be added to the top of .Pa /etc/pf.conf : .Bd -literal -offset indent pass quick on { sis2 } proto pfsync pass on { sis0 sis1 } proto carp keep state .Ed .Pp If it is preferable that one firewall handle the traffic, the .Ar advskew on the backup firewall's .Xr carp 4 interfaces should be set to something higher than the primary's. For example, if firewall B is the backup, its .Pa /etc/hostname.carp1 would look like this: .Bd -literal -offset indent inet 192.168.0.1 255.255.255.0 192.168.0.255 vhid 2 pass bar \e advskew 100 .Ed .Pp The following must also be added to .Pa /etc/sysctl.conf : .Bd -literal -offset indent net.inet.carp.preempt=1 .Ed .Sh SEE ALSO .Xr bpf 4 , .Xr carp 4 , .Xr enc 4 , .Xr inet 4 , .Xr inet6 4 , .Xr ipsec 4 , .Xr netintro 4 , .Xr pf 4 , .Xr hostname.if 5 , .Xr pf.conf 5 , .Xr protocols 5 , .Xr ifconfig 8 , .Xr tcpdump 8 .Sh HISTORY The .Nm device first appeared in .Ox 3.3 .