ACCF_DNS(9)						   BSD 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 enabled 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_http(9) accf_data(9)

HISTORY

     The accept filter mechanism was introduced in FreeBSD 4.0.

AUTHORS

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

BSD
								   July 16, 2008							       BSD