NAME

pflog —

packet filter logging interface

SYNOPSIS

device pflog

DESCRIPTION

The pflog interface is a device which makes visible all packets logged by the packet filter, pf(4). Logged packets can easily be monitored in real time by invoking tcpdump(1) on the pflog interface, or stored to disk using pflogd(8).

The pflog0 interface is created when the pflog module is loaded; further instances can be created using ifconfig(8). The pflog module is loaded automatically if both pf(4) and pflogd(8) are enabled.

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];
	u_int32_t	ridentifier;
};

EXAMPLES

Create a pflog interface and monitor all packets logged on it:

# ifconfig pflog create
pflog1
# ifconfig pflog1 up
# tcpdump -n -e -ttt -i pflog1

HISTORY

The pflog device first appeared in OpenBSD 3.0.

BUGS

FreeBSD does not set a process id in the pid field in pfloghdr.