This is a filter to be placed on a socket that will be using
to receive incoming HTTP connections.
It prevents the application from receiving the connected descriptor via
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
The utility of
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
kernel option is also a module that can be enabled at runtime via
if the INET option has been compiled into the kernel.
Assuming ACCEPT_FILTER_HTTP has been included in the kernel config
file or the
has been loaded, this will enable the http accept filter
on the socket
struct accept_filter_arg afa;
setsockopt(sok, SOL_SOCKET, SO_ACCEPTFILTER, &afa, sizeof(afa));