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.\" $FreeBSD$ 27.\" " 28.Dd November 15, 2000 29.Dt ACCF_HTTP 9 30.Os 31.Sh NAME 32.Nm accf_http 33.Nd "buffer incoming connections until a certain complete HTTP requests arrive" 34.Sh SYNOPSIS 35.Nm options INET 36.Nm options ACCEPT_FILTER_HTTP 37.Nm kldload accf_http 38.Sh DESCRIPTION 39This is a filter to be placed on a socket that will be using 40.Fn accept 41to receive incoming HTTP connections. 42.Pp 43It prevents the application from receiving the connected descriptor via 44.Fn accept 45until either a full HTTP/1.0 or HTTP/1.1 HEAD or GET request has 46been buffered by the kernel. 47.Pp 48If something other than a HTTP/1.0 or 49HTTP/1.1 HEAD or GET request is received the kernel will 50allow the application to receive the connection descriptor 51via 52.Fn accept . 53.Pp 54The utility of 55.Nm 56is such that a server will not have to context switch several times 57before performing the initial parsing of the request. 58This effectively reduces the amount of required CPU utilization 59to handle incoming requests by keeping active 60processes in preforking servers such as Apache low 61and reducing the size of the file descriptor set that needs 62to be managed by interfaces such as 63.Fn select , 64.Fn poll 65or 66.Fn kevent 67based servers. 68.Pp 69The 70.Nm 71kernel option is also a module that can be enabled at runtime via 72.Xr kldload 8 73if the INET option has been compiled into the kernel. 74.Sh EXAMPLES 75Assuming ACCEPT_FILTER_HTTP has been included in the kernel config 76file or the 77.Nm 78module 79has been loaded, this will enable the http accept filter 80on the socket 81.Fa sok . 82.Bd -literal -offset 0i 83 struct accept_filter_arg afa; 84 85 bzero(&afa, sizeof(afa)); 86 strcpy(afa.af_name, "httpready"); 87 setsockopt(sok, SOL_SOCKET, SO_ACCEPTFILTER, &afa, sizeof(afa)); 88.Ed 89.Sh SEE ALSO 90.Xr setsockopt 2 , 91.Xr accept_filter 9 92.Sh HISTORY 93The accept filter mechanism and the 94accf_http filter were introduced in 95.Fx 4.0 . 96.Sh AUTHORS 97This manual page and the filter were written by 98.An Alfred Perlstein . 99