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