|| FreeBSD Kernel Developer's Manual
buffer incoming DNS requests until the whole first request is present
| options ACCEPT_FILTER_DNS
This is a filter to be placed on a socket that will be using
() 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.
module is available in the kernel, the following code will enable the DNS accept filter on a socket
struct accept_filter_arg afa;
setsockopt(sok, SOL_SOCKET, SO_ACCEPTFILTER, &afa, sizeof(afa));
HISTORY The accept filter mechanism was introduced in
AUTHORS This manual page and the filter were written by