xref: /dragonfly/share/man/man9/accf_http.9 (revision 984263bc)
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2.\" Copyright (c) 2000 Alfred Perlstein
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26.\" $FreeBSD: src/share/man/man9/accf_http.9,v 1.1.2.6 2002/07/02 01:03:59 brian Exp $
27.\" "
28.Dd November 15, 2000
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.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.Xr accf_http 9
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 filedescriptor 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.Xr accf_http 9
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 EXAMPLE
75Assuming ACCEPT_FILTER_HTTP has been included in the kernel config
76file or the module
77.Xr accf_http 9
78has been loaded, this will enable the http accept filter
79on the socket
80.Fa sok .
81.Bd -literal -offset 0i
82	struct accept_filter_arg afa;
83
84	bzero(&afa, sizeof(afa));
85	strcpy(afa.af_name, "httpready");
86	setsockopt(sok, SOL_SOCKET, SO_ACCEPTFILTER, &afa, sizeof(afa));
87.Ed
88.Sh SEE ALSO
89.Xr setsockopt 2 ,
90.Xr accept_filter 9
91.Sh HISTORY
92The accept filter mechanism and the
93accf_http filter were introduced in
94.Fx 4.0 .
95.Sh AUTHORS
96This manual page and the filter were written by
97.An Alfred Perlstein .
98