NAME¶
accf_http —
buffer incoming connections
until a certain complete HTTP requests arrive
SYNOPSIS¶
options ACCEPT_FILTER_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 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 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
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¶
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
Perlstein.