Manual Pages  — PFLOG

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;
};

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

tcpdump(1), inet(4), inet6(4), netintro(4), pf(4), ifconfig(8), pflogd(8)