accf_http(9)

NAME

accf_http - buffer incoming connections until a certain com

plete HTTP
requests arrive

SYNOPSIS

options INET
options ACCEPT_FILTER_HTTP
kldload accf_http

DESCRIPTION

This is a filter to be placed on a socket that will be using

accept() to
receive incoming HTTP connections.

It prevents the application from receiving the connected de

scriptor via
accept() until either a full HTTP/1.0 or HTTP/1.1 HEAD or

GET request has
been buffered by the kernel.

If something other than a HTTP/1.0 or HTTP/1.1 HEAD or GET

request is
received the kernel will allow the application to receive

the connection
descriptor via accept().

The utility of accf_http is such that a server will not have

to context
switch several times before performing the initial parsing

of the
request. This effectively reduces the amount of required

CPU utilization
to handle incoming requests by keeping active processes in

preforking
servers such as Apache low and reducing the size of the file

descriptor
set that needs to be managed by interfaces such as select(),

poll() or
kevent() based servers.

The accf_http kernel option is also a module that can be en

abled at runtime via kldload(8) if the INET option has been compiled in

to the kernel.

EXAMPLES

Assuming ACCEPT_FILTER_HTTP has been included in the kernel

config file
or the accf_http module has been loaded, this will enable

the http accept
filter on the socket sok.

struct accept_filter_arg afa;

bzero(&afa, sizeof(afa));
strcpy(afa.af_name, "httpready");
setsockopt(sok, SOL_SOCKET, SO_ACCEPTFILTER, &afa,

sizeof(afa));

SEE ALSO

setsockopt(2), accept_filter(9)

HISTORY

The accept filter mechanism and the accf_http filter were

introduced in
FreeBSD 4.0.

AUTHORS

This manual page and the filter were written by Alfred Perl

stein.

BSD November 15, 2000

BSD