| ACCF_HTTP(9) | Kernel Developer's Manual | ACCF_HTTP(9) | 
accf_http —
options INET
pseudo-device accf_http
accept() to receive incoming HTTP connections.
Once installed on a listening socket, this filter is activated when a connection becomes ready to receive data (at which point accept(2) would usually return the connected descriptor to the application). The filter prevents the descriptor from being returned immediately to the application via accept(2). The descriptor is made available to the application via accept(2) only when one of the following conditions is met:
The utility of accf_http is 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.
struct accept_filter_arg afa; bzero(&afa, sizeof(afa)); strcpy(afa.af_name, "httpready"); setsockopt(sok, SOL_SOCKET, SO_ACCEPTFILTER, &afa, sizeof(afa));
accf_http filter
  were introduced in FreeBSD 4.0. They were ported to
  NetBSD by Coyote Point Systems and appeared in
  NetBSD 5.0.
| September 4, 2008 | NetBSD 9.4 |