135 lines
4.2 KiB
Groff
135 lines
4.2 KiB
Groff
.\" $FreeBSD$
|
|
.\"
|
|
.\" Copyright (c) 1996 Matthew R. Green
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 3. The name of the author may not be used to endorse or promote products
|
|
.\" derived from this software without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
|
|
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
|
|
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
|
|
.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
|
|
.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
|
|
.\" BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
|
|
.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
|
|
.\" AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
|
|
.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.Dd August 4, 1996
|
|
.Dt PFIL 9
|
|
.Os
|
|
.Sh NAME
|
|
.Nm pfil ,
|
|
.Nm pfil_hook_get ,
|
|
.Nm pfil_add_hook ,
|
|
.Nm pfil_remove_hook
|
|
.Nd packet filter interface
|
|
.Sh SYNOPSIS
|
|
.Fd #include <sys/param.h>
|
|
.Fd #include <sys/mbuf.h>
|
|
.Fd #include <net/if.h>
|
|
.Fd #include <net/pfil.h>
|
|
.Ft struct packet_filter_hook *
|
|
.Fn pfil_hook_get "int" "struct pfil_head *"
|
|
.Ft void
|
|
.Fn pfil_add_hook "int (*func)()" "int flags" "struct pfil_head *"
|
|
.Ft void
|
|
.Fn pfil_remove_hook "int (*func)()" "int flags" "struct pfil_head *"
|
|
.\"(void *, int, struct ifnet *, int, struct mbuf **)
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm
|
|
interface allows a function to be called on every incoming or outgoing
|
|
packets. The hooks for these are embedded in the
|
|
.Fn ip_input
|
|
and
|
|
.Fn ip_output
|
|
routines. The
|
|
.Fn pfil_hook_get
|
|
function returns the first member of a particular hook, either the in or out
|
|
list. The
|
|
.Fn pfil_add_hook
|
|
function takes a function of the form below as it's first argument, and the
|
|
flags for which lists to add the function to. The possible values for these
|
|
flags are some combination of PFIL_IN and PFIL_OUT. The
|
|
.Fn pfil_remove_hook
|
|
removes a hook from the specified lists.
|
|
.Pp
|
|
The
|
|
.Va func
|
|
argument is a function with the following prototype.
|
|
.Pp
|
|
.Fn func "void *data" "int hlen" "struct ifnet *net" "int dir" "struct mbuf **m"
|
|
.Pp
|
|
The
|
|
.Va data
|
|
describes the packet. Currently, this may only be a pointer to a ip structure. The
|
|
.Va net
|
|
and
|
|
.Va m
|
|
arguments describe the network interface and the mbuf holding data for this
|
|
packet. The
|
|
.Va dir
|
|
is the direction; 0 for incoming packets and 1 for outgoing packets. if the function
|
|
returns non-zero, this signals an error and no further processing of this packet is
|
|
performed. The function should set errno to indicate the nature of the error.
|
|
It is the hook's responsibiliy to free the chain if the packet is being dropped.
|
|
.Pp
|
|
The
|
|
.Nm
|
|
interface is enabled in the kernel via the
|
|
.Sy PFIL_HOOKS
|
|
option.
|
|
.Sh RETURN VALUES
|
|
If successful
|
|
.Fn pfil_hook_get
|
|
returns the first member of the packet filter list,
|
|
.Fn pfil_add_hook
|
|
and
|
|
.Fn pfil_remove_hook
|
|
are expected to always succeed.
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
interface first appeared in
|
|
.Nx 1.3 .
|
|
The
|
|
.Nm
|
|
input and output lists were originally implemented as
|
|
.Fd <sys/queue.h>
|
|
.Dv LIST
|
|
structures;
|
|
however this was changed in
|
|
.Nx 1.4
|
|
to
|
|
.Dv TAILQ
|
|
structures. This change was to allow the input and output filters to be
|
|
processed in reverse order, to allow the same path to be taken, in or out
|
|
of the kernel.
|
|
.Pp
|
|
The
|
|
.Nm
|
|
interface was changed in 1.4T to accept a 3rd parameter to both
|
|
.Fn pfil_add_hook
|
|
and
|
|
.Fn pfil_remove_hook
|
|
, introducing the capability of per-protocol filtering. This was done
|
|
primarily in order to support filtering of IPv6.
|
|
.Sh BUGS
|
|
The current
|
|
.Nm
|
|
implementation will need changes to suit a threaded kernel model.
|
|
.Sh SEE ALSO
|
|
.Xr bpf 4
|