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ACCF_DNS(9)		   Kernel Developer's Manual		   ACCF_DNS(9)

NAME
       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 en-
       abled at	runtime	via kldload(8) 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(2), accept_filter(9),	accf_data(9), accf_http(9)

HISTORY
       The accept filter mechanism was introduced in FreeBSD 4.0.

AUTHORS
       This manual page	and the	filter were written by David Malone.

FreeBSD	13.2			 July 16, 2008			   ACCF_DNS(9)

NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | SEE ALSO | HISTORY | AUTHORS

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