Provided by: freebsd-manpages_10.1~RC1-1_all bug


     accf_dns — buffer incoming DNS requests until the whole first request is present


     options INET
     options ACCEPT_FILTER_DNS
     kldload accf_dns


     This is a filter to be placed on a socket that will be using accept() to receive incoming

     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.


     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));


     setsockopt(2), accept_filter(9), accf_http(9) accf_data(9)


     The accept filter mechanism was introduced in FreeBSD 4.0.


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