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.