Add PFIL_MPSAFE flag to give hint to pfil(9) that the underlying firewall
[dragonfly.git] / share / man / man9 / pfil.9
CommitLineData
445813b7 1.\" $NetBSD: pfil.9,v 1.24 2004/01/01 15:24:35 wiz Exp $
77e0b69a 2.\" $DragonFly: src/share/man/man9/pfil.9,v 1.9 2008/09/20 06:08:13 sephe Exp $
445813b7
SW
3.\"
4.\" Copyright (c) 1996 Matthew R. Green
5.\" All rights reserved.
6.\"
7.\" Redistribution and use in source and binary forms, with or without
8.\" modification, are permitted provided that the following conditions
9.\" are met:
10.\" 1. Redistributions of source code must retain the above copyright
11.\" notice, this list of conditions and the following disclaimer.
12.\" 2. Redistributions in binary form must reproduce the above copyright
13.\" notice, this list of conditions and the following disclaimer in the
14.\" documentation and/or other materials provided with the distribution.
15.\" 3. The name of the author may not be used to endorse or promote products
16.\" derived from this software without specific prior written permission.
17.\"
18.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
19.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
20.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
21.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
22.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
23.\" BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
24.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
25.\" AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
26.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28.\" SUCH DAMAGE.
29.\"
6b53241a 30.Dd September 15, 2008
445813b7
SW
31.Dt PFIL 9
32.Os
33.Sh NAME
34.Nm pfil ,
35.Nm pfil_head_register ,
36.Nm pfil_head_unregister ,
37.Nm pfil_head_get ,
445813b7
SW
38.Nm pfil_add_hook ,
39.Nm pfil_remove_hook ,
40.Nm pfil_run_hooks
41.Nd packet filter interface
42.Sh SYNOPSIS
43.In sys/param.h
44.In sys/mbuf.h
45.In net/if.h
46.In net/pfil.h
6b53241a
SZ
47.Ft typedef int
48.Fn (*pfil_func_t) "void *arg" "struct mbuf **mp" "struct ifnet *ifp" "int dir"
445813b7
SW
49.Ft int
50.Fn pfil_head_register "struct pfil_head *ph"
51.Ft int
52.Fn pfil_head_unregister "struct pfil_head *pfh"
53.Ft struct pfil_head *
54.Fn pfil_head_get "int type" "u_long val"
445813b7 55.Ft void
9ed495de 56.Fn pfil_add_hook "pfil_func_t func" "void *arg" "int flags" "struct pfil_head *ph"
445813b7 57.Ft void
9ed495de 58.Fn pfil_remove_hook "pfil_func_t func" "void *arg" "int flags" "struct pfil_head *ph"
445813b7 59.Ft int
445813b7
SW
60.Fn pfil_run_hooks "struct pfil_head *ph" "struct mbuf **mp" "struct ifnet *ifp" "int dir"
61.Sh DESCRIPTION
62The
63.Nm
64framework allows for a specified function to be invoked for every
65incoming or outgoing packet for a particular network I/O stream.
66These hooks may be used to implement a firewall or perform packet
67transformations.
68.Pp
69Packet filtering points are registered with
70.Fn pfil_head_register .
71Filtering points are identified by a key (void *) and a data link type
72(int) in the
73.Em pfil_head
74structure.
75Packet filters use the key and data link type to look up the filtering
76point with which they register themselves.
77The key is unique to the filtering point.
78The data link type is a
79.Xr bpf 4
80DLT constant indicating what kind of header is present on the packet
81at the filtering point.
82Filtering points may be unregistered with the
83.Fn pfil_head_unregister
84function.
85.Pp
86Packet filters register/unregister themselves with a filtering point
87with the
88.Fn pfil_add_hook
89and
90.Fn pfil_remove_hook
91functions, respectively.
92The head is looked up using the
93.Fn pfil_head_get
94function, which takes the key and data link type that the packet filter
95expects.
96Filters may provide an argument to be passed to the filter when
97invoked on a packet.
98.Pp
99When a filter is invoked, the packet appears just as if it
100.Dq came off the wire .
101That is, all protocol fields are in network byte order.
102The filter is called with its specified argument, the pointer to the
103pointer to the mbuf containing the packet, the pointer to the network
104interface that the packet is traversing, and the direction
105.Dv ( PFIL_IN
106or
107.Dv PFIL_OUT ,
108see also below) that the packet is traveling.
109The filter may change which mbuf the mbuf ** argument references.
0f09e575
SW
110The filter returns an
111.Va errno
112if the packet processing is to stop, or 0 if the processing is to continue.
445813b7
SW
113If the packet processing is to stop, it is the responsibility of the
114filter to free the packet.
115.Pp
116The
117.Em flags
118parameter, used in the
119.Fn pfil_add_hook
120and
121.Fn pfil_remove_hook
122functions, indicates when the filter should be called.
123The flags are:
77e0b69a 124.Bl -tag -offset indent -width PFIL_MPSAFE -compact
445813b7
SW
125.It PFIL_IN
126call me on incoming packets
127.It PFIL_OUT
128call me on outgoing packets
129.It PFIL_ALL
130call me on all of the above
77e0b69a
SZ
131.It PFIL_MPSAFE
132call me without BGL
445813b7 133.El
445813b7
SW
134.Sh SEE ALSO
135.Xr bpf 4
136.Sh HISTORY
137The
138.Nm
139interface first appeared in
140.Nx 1.3 .
141The
142.Nm
143input and output lists were originally implemented as
44cb301e 144.In sys/queue.h
445813b7
SW
145.Dv LIST
146structures;
147however this was changed in
148.Nx 1.4
149to
150.Dv TAILQ
151structures.
152This change was to allow the input and output filters to be processed in
153reverse order, to allow the same path to be taken, in or out of the kernel.
154.Pp
155The
156.Nm
157interface was changed in 1.4T to accept a 3rd parameter to both
158.Fn pfil_add_hook
159and
160.Fn pfil_remove_hook ,
161introducing the capability of per-protocol filtering.
162This was done primarily in order to support filtering of IPv6.
163.Pp
164In 1.5K, the
165.Nm
166framework was changed to work with an arbitrary number of filtering points,
167as well as be less IP-centric.
168.Pp
169The
170.Nm
171interface was imported from
172.Nx
173into
4b2d9c41
SW
174.Dx 1.0
175and was reworked to suit a threaded kernel model in
6b53241a 176.Dx 2.1 .
445813b7
SW
177.Sh AUTHORS
178The
179.Nm
180interface was designed and implemented by Matthew R. Green, with help
181from Darren Reed, Jason R. Thorpe and Charles M. Hannum.
182Darren Reed added support for IPv6 in addition to IPv4.
183Jason R. Thorpe added support for multiple hooks and other clean up.