| PFLOG(4) | Device Drivers Manual | PFLOG(4) | 
pflog —
pseudo-device pflog
pflog interface is a pseudo-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(8) 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];
};
pflog interface and monitor all packets logged
  on it:
# ifconfig pflog1 up # tcpdump -n -e -ttt -i pflog1
pflog device first appeared in
  OpenBSD 3.0.
| August 17, 2018 | NetBSD 10.1 |