PFLOG(4) BSD Kernel Interfaces Manual PFLOG(4)NAME
pflog -- packet filter logging interface
SYNOPSIS
device pflog
DESCRIPTION
The pflog interface is a pseudo-device which makes visible all packets logged by the packet filter, pf(4). Logged packets can easily be mon-
itored in real time by invoking tcpdump(1) on the pflog interface, or stored to disk using pflogd(8).
The pflog0 interface is created automatically at boot if both pf(4) and pflogd(8) are enabled; further instances can be created using
ifconfig(8).
Each packet retrieved on this interface has a header associated with it of length PFLOG_HDRLEN. This header documents the address family,
interface name, rule number, reason, action, and direction of the packet that was logged. This structure, defined in <net/if_pflog.h> looks
like
struct pfloghdr {
u_int8_t length;
sa_family_t af;
u_int8_t action;
u_int8_t reason;
char ifname[IFNAMSIZ];
char ruleset[PF_RULESET_NAME_SIZE];
u_int32_t rulenr;
u_int32_t subrulenr;
uid_t uid;
pid_t pid;
uid_t rule_uid;
pid_t rule_pid;
u_int8_t dir;
u_int8_t pad[3];
};
EXAMPLES
Create a pflog interface and monitor all packets logged on it:
# ifconfig pflog1 up
# tcpdump -n -e -ttt -i pflog1
SEE ALSO tcpdump(1)inet(4), inet6(4), netintro(4), pf(4), ifconfig(8), pflogd(8)HISTORY
The pflog device first appeared in OpenBSD 3.0.
BSD December 10, 2001 BSD
Check Out this Related Man Page
PFSYNC(4) BSD Kernel Interfaces Manual PFSYNC(4)NAME
pfsync -- packet filter state table logging 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 synchronisation interface, pfsync 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.
By default, all local changes to the state table are exposed via pfsync. However, state changes from packets received by pfsync over the
network are not rebroadcast. States created by a rule marked with the no-sync keyword are omitted from the pfsync interface (see pf.conf(5)
for details).
The pfsync 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 maxupd parameter to ifconfig (see ifconfig(8) and the example below
for more details).
Each packet retrieved on this interface has a header associated with it of length 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 struc-
ture is defined in <net/if_pfsync.h> as:
struct pfsync_header {
u_int8_t version;
u_int8_t af;
u_int8_t action;
u_int8_t count;
};
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. 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 syncpeer keyword, the peer address is used
as a destination for the pfsync traffic.
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) (it is not
supported at the moment on NetBSD due to the lack of any encapsulation pseudo-device).
There is a one-to-one correspondence between packets seen by bpf(4) on the pfsync interface, and packets sent out on the synchronisation
interface, i.e. a packet with 4 state deletion messages on pfsync means that the same 4 deletions were sent out on the synchronisation inter-
face. However, the actual packet contents may differ as the messages sent over the network are "compressed" where possible, containing only
the necessary information.
EXAMPLES
pfsync and 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.
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):
/etc/ifconfig.sis0:
inet 10.0.0.254 255.255.255.0 NONE
/etc/ifconfig.sis1:
inet 192.168.0.254 255.255.255.0 NONE
/etc/ifconfig.sis2:
inet 192.168.254.254 255.255.255.0 NONE
/etc/ifconfig.carp0:
inet 10.0.0.1 255.255.255.0 10.0.0.255 vhid 1 pass foo
/etc/ifconfig.carp1:
inet 192.168.0.1 255.255.255.0 192.168.0.255 vhid 2 pass bar
/etc/ifconfig.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
pass on { sis0 sis1 } proto carp
If it is preferable that one firewall handle the traffic, 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/ifconfig.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), inet(4), inet6(4), ipsec(4), netintro(4), pf(4), ifconfig.if(5), pf.conf(5), protocols(5), ifconfig(8), tcpdump(8)HISTORY
The pfsync device first appeared in OpenBSD 3.3.
CAVEATS
pfsync is not available when using pf(4) as a kernel module.
BSD April 12, 2010 BSD