1.\" $OpenBSD: pfsync.4,v 1.28 2009/02/17 10:05:18 dlg Exp $ 2.\" 3.\" Copyright (c) 2002 Michael Shalayeff 4.\" Copyright (c) 2003-2004 Ryan McBride 5.\" All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 17.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 18.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 19.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 20.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 21.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF MIND, 22.\" USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 23.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 24.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 25.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26.\" 27.Dd October 17, 2023 28.Dt PFSYNC 4 29.Os 30.Sh NAME 31.Nm pfsync 32.Nd packet filter state table sychronisation interface 33.Sh SYNOPSIS 34.Cd "device pfsync" 35.Sh DESCRIPTION 36The 37.Nm 38interface is a pseudo-device which exposes certain changes to the state 39table used by 40.Xr pf 4 . 41State changes can be viewed by invoking 42.Xr tcpdump 1 43on the 44.Nm 45interface. 46If configured with a physical synchronisation interface, 47.Nm 48will also send state changes out on that interface, 49and insert state changes received on that interface from other systems 50into the state table. 51.Pp 52By default, all local changes to the state table are exposed via 53.Nm . 54State changes from packets received by 55.Nm 56over the network are not rebroadcast. 57Updates to states created by a rule marked with the 58.Ar no-sync 59keyword are ignored by the 60.Nm 61interface (see 62.Xr pf.conf 5 63for details). 64.Pp 65The 66.Nm 67interface will attempt to collapse multiple state updates into a single 68packet where possible. 69The maximum number of times a single state can be updated before a 70.Nm 71packet will be sent out is controlled by the 72.Ar maxupd 73parameter to ifconfig 74(see 75.Xr ifconfig 8 76and the example below for more details). 77The sending out of a 78.Nm 79packet will be delayed by a maximum of one second. 80.Sh NETWORK SYNCHRONISATION 81States can be synchronised between two or more firewalls using this 82interface, by specifying a synchronisation interface using 83.Xr ifconfig 8 . 84For example, the following command sets fxp0 as the synchronisation 85interface: 86.Bd -literal -offset indent 87# ifconfig pfsync0 syncdev fxp0 88.Ed 89.Pp 90By default, state change messages are sent out on the synchronisation 91interface using IP multicast packets to the 224.0.0.240 group address. 92An alternative destination address for 93.Nm 94packets can be specified using the 95.Ic syncpeer 96keyword. 97This can be used in combination with 98.Xr ipsec 4 99to protect the synchronisation traffic. 100In such a configuration, the syncdev should be set to the 101.Xr enc 4 102interface, as this is where the traffic arrives when it is decapsulated, 103e.g.: 104.Bd -literal -offset indent 105# ifconfig pfsync0 syncpeer 10.0.0.2 syncdev enc0 106.Ed 107.Pp 108It is important that the pfsync traffic be well secured 109as there is no authentication on the protocol and it would 110be trivial to spoof packets which create states, bypassing the pf ruleset. 111Either run the pfsync protocol on a trusted network \- ideally a network 112dedicated to pfsync messages such as a crossover cable between two firewalls, 113or specify a peer address and protect the traffic with 114.Xr ipsec 4 . 115.Pp 116When new features are introduced to 117.Xr pf 4 118the format of messages used by 119.Nm 120might change. 121.Nm 122will by default use the latest format. 123If synchronization with a peer running an older version of FreeBSD is needed the 124.Ar version 125parameter can be used. 126E.g.: 127.Bd -literal -offset indent 128# ifconfig pfsync0 version 1301 129.Ed 130.Pp 131.Bd 132Currently the following versions are supported: 133.Bl -tag -width indent 134.It Cm 1301 135FreeBSD releases 13.2 and older. 136Compatibility with FreeBSD 13.1 has been verified. 137.It Cm 1400 138FreeBSD release 14.0. 139.El 140.Ed 141.Pp 142.Nm 143has the following 144.Xr sysctl 8 145tunables: 146.Bl -tag -width ".Va net.pfsync" 147.It Va net.pfsync.carp_demotion_factor 148Value added to 149.Va net.inet.carp.demotion 150while 151.Nm 152tries to perform its bulk update. 153See 154.Xr carp 4 155for more information. 156Default value is 240. 157.It Va net.pfsync.pfsync_buckets 158The number of 159.Nm 160buckets. 161This affects the performance and memory tradeoff. 162Defaults to twice the number of CPUs. 163Change only if benchmarks show this helps on your workload. 164.El 165.Sh EXAMPLES 166.Nm 167and 168.Xr carp 4 169can be used together to provide automatic failover of a pair of firewalls 170configured in parallel. 171One firewall will handle all traffic until it dies, is shut down, or is 172manually demoted, at which point the second firewall will take over 173automatically. 174.Pp 175Both firewalls in this example have three 176.Xr sis 4 177interfaces. 178sis0 is the external interface, on the 10.0.0.0/24 subnet; sis1 is the 179internal interface, on the 192.168.0.0/24 subnet; and sis2 is the 180.Nm 181interface, using the 192.168.254.0/24 subnet. 182A crossover cable connects the two firewalls via their sis2 interfaces. 183On all three interfaces, firewall A uses the .254 address, while firewall B 184uses .253. 185The interfaces are configured as follows (firewall A unless otherwise 186indicated): 187.Pp 188Interfaces configuration in 189.Pa /etc/rc.conf : 190.Bd -literal -offset indent 191network_interfaces="lo0 sis0 sis1 sis2" 192ifconfig_sis0="10.0.0.254/24" 193ifconfig_sis0_alias0="inet 10.0.0.1/24 vhid 1 pass foo" 194ifconfig_sis1="192.168.0.254/24" 195ifconfig_sis1_alias0="inet 192.168.0.1/24 vhid 2 pass bar" 196ifconfig_sis2="192.168.254.254/24" 197pfsync_enable="YES" 198pfsync_syncdev="sis2" 199.Ed 200.Pp 201.Xr pf 4 202must also be configured to allow 203.Nm 204and 205.Xr carp 4 206traffic through. 207The following should be added to the top of 208.Pa /etc/pf.conf : 209.Bd -literal -offset indent 210pass quick on { sis2 } proto pfsync keep state (no-sync) 211pass on { sis0 sis1 } proto carp keep state (no-sync) 212.Ed 213.Pp 214It is preferable that one firewall handle the forwarding of all the traffic, 215therefore the 216.Ar advskew 217on the backup firewall's 218.Xr carp 4 219vhids should be set to something higher than 220the primary's. 221For example, if firewall B is the backup, its 222carp1 configuration would look like this: 223.Bd -literal -offset indent 224ifconfig_sis1_alias0="inet 192.168.0.1/24 vhid 2 pass bar advskew 100" 225.Ed 226.Pp 227The following must also be added to 228.Pa /etc/sysctl.conf : 229.Bd -literal -offset indent 230net.inet.carp.preempt=1 231.Ed 232.Sh SEE ALSO 233.Xr tcpdump 1 , 234.Xr bpf 4 , 235.Xr carp 4 , 236.Xr enc 4 , 237.Xr inet 4 , 238.Xr inet6 4 , 239.Xr ipsec 4 , 240.Xr netintro 4 , 241.Xr pf 4 , 242.Xr pf.conf 5 , 243.Xr protocols 5 , 244.Xr rc.conf 5 , 245.Xr ifconfig 8 246.Sh HISTORY 247The 248.Nm 249device first appeared in 250.Ox 3.3 . 251It was first imported to 252.Fx 5.3 . 253.Pp 254The 255.Nm 256protocol and kernel implementation were significantly modified in 257.Fx 9.0 . 258The newer protocol is not compatible with older one and will not interoperate 259with it. 260