NAME
accf_http —
buffer incoming connections until a
certain complete 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 usingaccept()
to receive incoming HTTP connections.
It prevents the application from receiving the
connected descriptor 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 filedescriptor 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 enabled at runtime via
kldload(8) if the INET option has been compiled into 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
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 Perlstein.