152 lines
4.3 KiB
Groff
152 lines
4.3 KiB
Groff
.\"
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.\" Copyright (c) 2000 Alfred Perlstein
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.\"
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\" "
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.Dd June 25, 2000
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.Os
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.Dt ACCEPT_FILTER 9
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.Sh NAME
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.Nm accept_filter ,
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.Nm accept_filt_add ,
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.Nm accept_filt_del ,
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.Nm accept_filt_generic_mod_event ,
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.Nm accept_filt_get
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.Nd filter incoming connections
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.Sh SYNOPSIS
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.In sys/types.h
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.In sys/module.h
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.In sys/socket.h
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.Fd #define ACCEPT_FILTER_MOD
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.In sys/socketvar.h
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.Ft int
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.Fn accept_filt_add "struct accept_filter *filt"
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.Ft int
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.Fn accept_filt_del "char *name"
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.Ft int
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.Fn accept_filt_generic_mod_event "module_t mod" "int event" "void *data"
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.Ft struct accept_filter *
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.Fn accept_filt_get "char *name"
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.Sh DESCRIPTION
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Accept filters allow an application to request
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that the kernel pre-process incoming connections.
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An accept filter is requested via the
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.Xr setsockopt 2
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system call, passing in an
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.Fa optname
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of
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.Dv SO_ACCEPTFILTER .
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.Sh IMPLEMENTATION NOTES
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A module that wants to be an accept filter
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must provide a
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.Vt "struct accept_filter"
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to the system:
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.Bd -literal
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struct accept_filter {
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char accf_name[16];
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void (*accf_callback)(struct socket *so, void *arg, int waitflag);
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void * (*accf_create)(struct socket *so, char *arg);
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void (*accf_destroy)(struct socket *so);
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SLIST_ENTRY(accept_filter) accf_next; /* next on the list */
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};
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.Ed
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.Pp
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The module should register it with the function
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.Fn accept_filt_add ,
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passing a pointer to a
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.Vt "struct accept_filter" ,
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allocated with
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.Xr malloc 9 .
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.Pp
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The fields of
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.Vt "struct accept_filter"
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are as follows:
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.Bl -tag -width ".Va accf_callback"
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.It Va accf_name
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Name of the filter;
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this is how it will be accessed from userland.
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.It Va accf_callback
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The callback that the kernel will do
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once the connection is established.
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It is the same as a socket upcall
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and will be called when the connection is established
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and whenever new data arrives on the socket,
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unless the callback modifies the socket's flags.
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.It Va accf_create
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Called whenever a
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.Xr setsockopt 2
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installs the filter onto
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a listening socket.
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.It Va accf_destroy
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Called whenever the user removes the accept filter on the socket.
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.El
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.Pp
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The
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.Fn accept_filt_del
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function
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passed the same string used in
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.Va accept_filter.accf_name
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during registration with
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.Fn accept_filt_add ,
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the kernel will then disallow and further userland use of the filter.
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.Pp
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The
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.Fn accept_filt_get
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function is used internally to locate which accept filter to use via the
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.Xr setsockopt 2
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system call.
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.Pp
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The
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.Fn accept_filt_generic_mod_event
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function provides a simple way to avoid duplication of code
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for accept filters which do not use the argument field to load
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and unload themselves.
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This function can be used in the
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.Vt moduledata_t
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struct for the
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.Xr DECLARE_MODULE 9
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macro.
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.Sh SEE ALSO
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.Xr setsockopt 2 ,
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.Xr accf_data 9 ,
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.Xr accf_http 9 ,
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.Xr malloc 9
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.Sh HISTORY
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The accept filter mechanism was introduced in
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.Fx 4.0 .
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.Sh AUTHORS
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This manual page was written by
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.An -nosplit
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.An Alfred Perlstein ,
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.An Sheldon Hearn
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and
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.An Jeroen Ruigrok van der Werven.
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.Pp
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The accept filter concept was pioneered by
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.An David Filo
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at Yahoo!\&
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and refined to be a loadable module system by
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.An Alfred Perlstein .
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