99 lines
3.2 KiB
Groff
99 lines
3.2 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 November 15, 2000
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.Os
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.Dt ACCF_HTTP 9
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.Sh NAME
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.Nm accf_http
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.Nd "buffer incoming connections until a certain complete HTTP requests arrive"
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.Sh SYNOPSIS
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.Nm options INET
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.Nm options ACCEPT_FILTER_HTTP
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.Nm kldload accf_http
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.Sh DESCRIPTION
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This is a filter to be placed on a socket that will be using
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.Fn accept
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to receive incoming HTTP connections.
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.Pp
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It prevents the application from receiving the connected descriptor via
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.Fn accept
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until either a full HTTP/1.0 or HTTP/1.1 HEAD or GET request has
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been buffered by the kernel.
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.Pp
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If something other than a HTTP/1.0 or
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HTTP/1.1 HEAD or GET request is received the kernel will
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allow the application to receive the connection descriptor
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via
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.Fn accept .
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.Pp
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The utility of
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.Nm
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is such that a server will not have to context switch several times
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before performing the initial parsing of the request.
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This effectively reduces the amount of required CPU utilization
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to handle incoming requests by keeping active
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processes in preforking servers such as Apache low
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and reducing the size of the file descriptor set that needs
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to be managed by interfaces such as
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.Fn select ,
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.Fn poll
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or
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.Fn kevent
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based servers.
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.Pp
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The
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.Nm
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kernel option is also a module that can be enabled at runtime via
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.Xr kldload 8
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if the INET option has been compiled into the kernel.
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.Sh EXAMPLE
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Assuming ACCEPT_FILTER_HTTP has been included in the kernel config
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file or the
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.Nm
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module
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has been loaded, this will enable the http accept filter
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on the socket
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.Fa sok .
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.Bd -literal -offset 0i
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struct accept_filter_arg afa;
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bzero(&afa, sizeof(afa));
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strcpy(afa.af_name, "httpready");
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setsockopt(sok, SOL_SOCKET, SO_ACCEPTFILTER, &afa, sizeof(afa));
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.Ed
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.Sh SEE ALSO
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.Xr setsockopt 2 ,
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.Xr accept_filter 9
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.Sh HISTORY
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The accept filter mechanism and the
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accf_http filter were introduced in
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.Fx 4.0 .
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.Sh AUTHORS
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This manual page and the filter were written by
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.An Alfred Perlstein .
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