NAME
pflog – packet filter logging BPF tap
SYNOPSIS
device pflog
DESCRIPTION
The pflog is a BPF tap 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 BPF tap, or stored to disk using pflogd(8).
The pflog0 BPF tap 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 BPF tap 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;
};
The number of pflog devices can be configured with the net.pflog.if_count sysctl.
EXAMPLES
Monitor all packets logged on pflog0:
# tcpdump -n -e -ttt -i pflog0
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.
BUGS
FreeBSD does not set a process id in the pid field in pfloghdr.