/ kernel routines / Accf_dns - Buffer Incoming DNS Requests Until The Whole First Request Is Present


accf_dns - buffer incoming DNS requests until the whole first request is present
SYNOPSIS
options INET

options ACCEPT_FILTER_DNS

kldload accf_dns
DESCRIPTION
This is a filter to be placed on a socket that will be using accept() to receive incoming connections.

It prevents the application from receiving the connected descriptor via accept() until a whole DNS request is available on the socket. It does this by reading the first two bytes of the request, to determine its size, and waiting until the required amount of data is available to be read.

The ACCEPT_FILTER_DNS kernel option is also a module that can be enabled at runtime via kldload if the INET option has been compiled into the kernel.
EXAMPLES
If the accf_dns module is available in the kernel, the following code will enable the DNS accept filter on a socket sok.

	struct accept_filter_arg afa; 
 
	bzero(&afa, sizeof(afa)); 
	strcpy(afa.af_name, "dnsready"); 
	setsockopt(sok, SOL_SOCKET, SO_ACCEPTFILTER, &afa, sizeof(afa));
SEE ALSO
setsockopt , accept_filter , accf_data , accf_http
HISTORY
The accept filter mechanism was introduced in FreeBSD 4.0.
AUTHORS
This manual page and the filter were written by David Malone.
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accf_http - buffer incoming connections until a certain complete HTTP requests arrive
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accf_data - buffer incoming connections until data arrives
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