update to reflect new api
Submitted by: Max Laier <max@love2party.net> Obtained from: NetBSD (with changes)
This commit is contained in:
sam
parent
b73973612a
commit
b7d6bb09bb
@ -1,3 +1,5 @@
|
||||
.\" $NetBSD: pfil.9,v 1.22 2003/07/01 13:04:06 wiz Exp $
|
||||
.\"
|
||||
.\" Copyright (c) 1996 Matthew R. Green
|
||||
.\" All rights reserved.
|
||||
.\"
|
||||
@ -25,105 +27,109 @@
|
||||
.\" SUCH DAMAGE.
|
||||
.\"
|
||||
.\" $FreeBSD$
|
||||
.Dd August 4, 1996
|
||||
.Dd September 8, 2003
|
||||
.Dt PFIL 9
|
||||
.Os
|
||||
.Sh NAME
|
||||
.Nm pfil ,
|
||||
.Nm pfil_head_register ,
|
||||
.Nm pfil_head_unregister ,
|
||||
.Nm pfil_head_get ,
|
||||
.Nm pfil_hook_get ,
|
||||
.Nm pfil_add_hook ,
|
||||
.Nm pfil_remove_hook
|
||||
.Nm pfil_remove_hook ,
|
||||
.Nm pfil_run_hooks
|
||||
.Nd packet filter interface
|
||||
.Sh SYNOPSIS
|
||||
.In sys/param.h
|
||||
.In sys/mbuf.h
|
||||
.In sys/socket.h
|
||||
.In net/if.h
|
||||
.In net/pfil.h
|
||||
.Ft "struct packet_filter_hook *"
|
||||
.Fn pfil_hook_get "int flag" "struct pfil_head *ph"
|
||||
.Ft int
|
||||
.Fo pfil_add_hook
|
||||
.Fa "int \*[lp]*func\*[rp]\*[lp]void *, int, struct ifnet *, int, struct mbuf **\*[rp]"
|
||||
.Fa "int flags"
|
||||
.Fa "struct pfil_head *ph"
|
||||
.Fc
|
||||
.Fn pfil_head_register "struct pfil_head *head"
|
||||
.Ft int
|
||||
.Fo pfil_remove_hook
|
||||
.Fa "int \*[lp]*func\*[rp]\*[lp]void *, int, struct ifnet *, int, struct mbuf **\*[rp]"
|
||||
.Fa "int flags"
|
||||
.Fa "struct pfil_head *ph"
|
||||
.Fc
|
||||
.Fn pfil_head_unregister "struct pfil_head *head"
|
||||
.Ft struct pfil_head *
|
||||
.Fn pfil_head_get "int af" "u_long dlt"
|
||||
.Ft struct packet_filter_hook *
|
||||
.Fn pfil_hook_get "int dir" "struct pfil_head *head"
|
||||
.Ft void
|
||||
.Fn pfil_add_hook "int (*func)()" "void *arg" "int flags" "struct pfil_head *"
|
||||
.Ft void
|
||||
.Fn pfil_remove_hook "int (*func)()" "void *arg" "int flags" "struct pfil_head *"
|
||||
.Ft int
|
||||
.Fn (*func) "void *arg" "struct mbuf **mp" "struct ifnet *" "int dir"
|
||||
.Ft int
|
||||
.Fn pfil_run_hooks "struct pfil_head *head" "struct mbuf **mp" "struct ifnet *" "int dir"
|
||||
.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 its first argument, and the
|
||||
flags for which lists to add the function to.
|
||||
The possible values for these
|
||||
flags are some combination of
|
||||
.Dv PFIL_IN
|
||||
and
|
||||
.Dv PFIL_OUT .
|
||||
The
|
||||
.Fn pfil_remove_hook
|
||||
removes a hook from the specified lists.
|
||||
framework allows for a specified function to be invoked for every
|
||||
incoming or outgoing packet for a particular network I/O stream.
|
||||
These hooks may be used to implement a firewall or perform packet
|
||||
transformations.
|
||||
.Pp
|
||||
The
|
||||
.Fa func
|
||||
argument is a function with the following prototype.
|
||||
.Pp
|
||||
.Ft int
|
||||
.Fn func "void *data" "int hlen" "struct ifnet *net" "int dir" "struct mbuf **m"
|
||||
.Pp
|
||||
The
|
||||
.Fa data
|
||||
describes the packet.
|
||||
Currently, this may only be a pointer to an
|
||||
.Vt ip
|
||||
Packet filtering points are registered with
|
||||
.Fn pfil_head_register .
|
||||
Filtering points are identified by a key (void *) and a data link type
|
||||
(int) in the
|
||||
.Em pfil_head
|
||||
structure.
|
||||
The
|
||||
.Fa net
|
||||
Packet filters use the key and data link type to look up the filtering
|
||||
point with which they register themselves.
|
||||
The key is unique to the filtering point.
|
||||
The data link type is a
|
||||
.Xr bpf 4
|
||||
DLT constant indicating what kind of header is present on the packet
|
||||
at the filtering point.
|
||||
Filtering points may be unregistered with the
|
||||
.Fn pfil_head_unregister
|
||||
function.
|
||||
.Pp
|
||||
Packet filters register/unregister themselves with a filtering point
|
||||
with the
|
||||
.Fn pfil_add_hook
|
||||
and
|
||||
.Fa m
|
||||
arguments describe the network interface and the mbuf holding data for this
|
||||
packet.
|
||||
The
|
||||
.Fa 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
|
||||
.Va errno
|
||||
to indicate the nature of the error.
|
||||
It is the hook's responsibility to free the chain if the packet is being dropped.
|
||||
.Fn pfil_remove_hook
|
||||
functions, respectively.
|
||||
The head is looked up using the
|
||||
.Fn pfil_head_get
|
||||
function, which takes the key and data link type that the packet filter
|
||||
expects.
|
||||
Filters may provide an argument to be passed to the filter when
|
||||
invoked on a packet.
|
||||
.Pp
|
||||
When a filter is invoked, the packet appears just as if it
|
||||
.Dq came off the wire .
|
||||
That is, all protocol fields are in network byte order.
|
||||
The filter is called with its specified argument, the pointer to the
|
||||
pointer to the mbuf containing the packet, the pointer to the network
|
||||
interface that the packet is traversing, and the direction (PFIL_IN
|
||||
or PFIL_OUT) that the packet is traveling.
|
||||
The filter may change which mbuf the mbuf ** argument references.
|
||||
The filter returns an errno if the packet processing is to stop, or 0
|
||||
if the processing is to continue.
|
||||
If the packet processing is to stop, it is the responsibility of the
|
||||
filter to free the packet.
|
||||
.Pp
|
||||
The
|
||||
.Nm
|
||||
interface is enabled in the kernel via the
|
||||
.Cd PFIL_HOOKS
|
||||
.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
|
||||
.Fn pfil_head_get
|
||||
returns the pfil_head structure for the given key/dlt.
|
||||
.Fn pfil_add_hook
|
||||
and
|
||||
.Fn pfil_remove_hook
|
||||
are expected to always succeed.
|
||||
return 0 if successful. If called with flag PFIL_WAITOK,
|
||||
.Fn pfil_remove_hook
|
||||
is expected to always succeed.
|
||||
.Pp
|
||||
.Fn pfil_head_unregister
|
||||
might sleep!
|
||||
.Sh HISTORY
|
||||
The
|
||||
.Nm
|
||||
@ -132,7 +138,7 @@ interface first appeared in
|
||||
The
|
||||
.Nm
|
||||
input and output lists were originally implemented as
|
||||
.In sys/queue.h
|
||||
.Fd \*[Lt]sys/queue.h\*[Gt]
|
||||
.Dv LIST
|
||||
structures;
|
||||
however this was changed in
|
||||
@ -140,9 +146,8 @@ however this was changed in
|
||||
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.
|
||||
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
|
||||
@ -151,11 +156,31 @@ interface was changed in 1.4T to accept a 3rd parameter to both
|
||||
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
|
||||
This was done primarily in order to support filtering of IPv6.
|
||||
.Pp
|
||||
In 1.5K, the
|
||||
.Nm
|
||||
implementation will need changes to suit a threaded kernel model.
|
||||
framework was changed to work with an arbitrary number of filtering points,
|
||||
as well as be less IP-centric.
|
||||
.Pp
|
||||
Fine-grained locking was adding in FreeBSD 5.2.
|
||||
.Sh BUGS
|
||||
.Fn pfil_hook_get
|
||||
is only safe for internal use.
|
||||
.Pp
|
||||
FreeBSD implements only hooks for AF_INET and AF_INET6.
|
||||
Packets diverted through these hooks have data in
|
||||
host byte order contrary to the above statements.
|
||||
.Pp
|
||||
The
|
||||
.Xr bridge 4
|
||||
diverts inbound AF_INET traffic, but contrary to the above
|
||||
statements, the data is provided in host byte order.
|
||||
.Pp
|
||||
When a pfil_head is being modified no traffic is diverted
|
||||
(to avoid deadlock).
|
||||
This means that unwanted traffic may flow for a short period
|
||||
of time.
|
||||
.Sh SEE ALSO
|
||||
.Xr bpf 4
|
||||
.Xr bpf 4 ,
|
||||
.Xr bridge 4
|
||||
|
||||
Loading…
Reference in New Issue
Block a user