---
name: "accf_http"
section: "9freebsd"
platform: "linux"
package: "freebsd-manpages"
version: "12.2-2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/accf_http/9freebsd"
---

# accf\_http(9freebsd)

buffer incoming connections until a certain complete HTTP requests arrive

## 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 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)](/kldload/8.md) 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)](/setsockopt/2.md), [accept\_filter(9)](/accept_filter/9.md)

## 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.