Copyright (c) 2000 Alfred Perlstein
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$FreeBSD: stable/10/share/man/man9/accf_http.9 206622 2010-04-14 19:08:06Z uqs $
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.Dd November 15, 2000 .Dt ACCF_HTTP 9 .Os .Sh NAME .Nm accf_http .Nd "buffer incoming connections until a certain complete HTTP requests arrive" .Sh SYNOPSIS .Nm options INET .Nm options ACCEPT_FILTER_HTTP .Nm kldload accf_http .Sh DESCRIPTION This is a filter to be placed on a socket that will be using .Fn accept to receive incoming HTTP connections.
p It prevents the application from receiving the connected descriptor via .Fn accept until either a full HTTP/1.0 or HTTP/1.1 HEAD or GET request has been buffered by the kernel.
p 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 .Fn accept .
p The utility of .Nm 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 .Fn select , .Fn poll or .Fn kevent based servers.
p The .Nm kernel option is also a module that can be enabled at runtime via .Xr kldload 8 if the INET option has been compiled into the kernel. .Sh EXAMPLES Assuming ACCEPT_FILTER_HTTP has been included in the kernel config file or the .Nm module has been loaded, this will enable the http accept filter on the socket .Fa sok . d -literal -offset 0i struct accept_filter_arg afa; bzero(&afa, sizeof(afa)); strcpy(afa.af_name, "httpready"); setsockopt(sok, SOL_SOCKET, SO_ACCEPTFILTER, &afa, sizeof(afa)); .Ed .Sh SEE ALSO .Xr setsockopt 2 , .Xr accept_filter 9 .Sh HISTORY The accept filter mechanism and the accf_http filter were introduced in .Fx 4.0 . .Sh AUTHORS This manual page and the filter were written by .An Alfred Perlstein .