.\"     $NetBSD: bpf.9,v 1.3 2010/12/02 12:54:13 wiz Exp $
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.Dd June 8, 2010
.Dt BPF 9
.Os
.Sh NAME
.Nm bpf
.Nd Berkeley Packet Filter kernel interface
.Sh SYNOPSIS
.In sys/mbuf.h
.In net/bpf.h
.Sh DESCRIPTION
.Nm
is called via an operations vector described by the following struct:
.Pp
.Bd -literal
struct bpf_ops {
        void (*bpf_attach)(struct ifnet *, u_int, u_int, struct bpf_if **);
        void (*bpf_detach)(struct ifnet *);
        void (*bpf_change_type)(struct ifnet *, u_int, u_int);

        void (*bpf_tap)(struct bpf_if *, u_char *, u_int);
        void (*bpf_mtap)(struct bpf_if *, struct mbuf *);
        void (*bpf_mtap2)(struct bpf_if *, void *, u_int, struct mbuf *);
        void (*bpf_mtap_af)(struct bpf_if *, uint32_t, struct mbuf *);
        void (*bpf_mtap_et)(struct bpf_if *, uint16_t, struct mbuf *);
        void (*bpf_mtap_sl_in)(struct bpf_if *, u_char *, struct mbuf **);
        void (*bpf_mtap_sl_out)(struct bpf_if *, u_char *, struct mbuf *);
};
.Ed
.Pp
This vector is found from
.Vt struct bpf_ops *
.Va bpf_ops .
It is either a
.Dq stub
implementation or a real implementation, depending on whether
.Nm
is absent or present in the kernel, respectively.
.Sh CODE REFERENCES
The
.Nm
implementation is located in
.Pa sys/net/bpf.c ,
the stub implementation is in
.Pa sys/net/bpf_stub.c ,
and
.Pa sys/net/bpf.h
describes the interface.