1.\" 2.\" Copyright (c) 2000 Alfred Perlstein 3.\" 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR 16.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT, 19.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25.\" 26.\" $FreeBSD: src/share/man/man9/accf_http.9,v 1.11 2005/01/18 20:52:51 ru Exp $ 27.\" " 28.Dd September 4, 2008 29.Os 30.Dt ACCF_HTTP 9 31.Sh NAME 32.Nm accf_http 33.Nd "buffer incoming connections until a certain complete HTTP requests arrive" 34.Sh SYNOPSIS 35.Cd "options INET" 36.Cd "pseudo-device accf_http" 37.Sh DESCRIPTION 38This is a filter to be placed on a socket that will be using 39.Fn accept 40to receive incoming HTTP connections. 41.Pp 42It prevents the application from receiving the connected descriptor via 43.Fn accept 44until either a full HTTP/1.0 or HTTP/1.1 HEAD or GET request has 45been buffered by the kernel. 46.Pp 47If something other than a HTTP/1.0 or 48HTTP/1.1 HEAD or GET request is received the kernel will 49allow the application to receive the connection descriptor 50via 51.Fn accept . 52.Pp 53The utility of 54.Nm 55is that a server will not have to context switch several times 56before performing the initial parsing of the request. 57This effectively reduces the amount of required CPU utilization 58to handle incoming requests by keeping active 59processes in preforking servers such as Apache low 60and reducing the size of the file descriptor set that needs 61to be managed by interfaces such as 62.Fn select , 63.Fn poll 64or 65.Fn kevent 66based servers. 67.Sh EXAMPLES 68If the accf_data accept filter is present in the kernel configuration, 69this will enable the http accept filter 70on the socket 71.Fa sok . 72.Bd -literal -offset 0i 73 struct accept_filter_arg afa; 74 75 bzero(&afa, sizeof(afa)); 76 strcpy(afa.af_name, "httpready"); 77 setsockopt(sok, SOL_SOCKET, SO_ACCEPTFILTER, &afa, sizeof(afa)); 78.Ed 79.Sh SEE ALSO 80.Xr setsockopt 2 , 81.Xr accept_filter 9 82.Sh HISTORY 83The accept filter mechanism and the 84accf_http filter were introduced in 85.Fx 4.0 . 86They were ported to 87.Nx 88by Coyote Point Systems and appeared in 89.Nx 5.0 . 90.Sh AUTHORS 91This manual page and the filter were written by 92.An Alfred Perlstein . 93