accf_data(9) buffer incoming connections until data arrives


options INET
kldload accf_data


This is a filter to be placed on a socket that will be using Fn accept to receive incoming connections.

It prevents the application from receiving the connected descriptor via Fn accept until data arrives on the connection.

The Fa ACCEPT_FILTER_DATA 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.


Assuming ACCEPT_FILTER_DATA has been included in the kernel config file or the options INET module has been loaded, this will enable the data accept filter on the socket Fa sok .
        struct accept_filter_arg afa;
        bzero(&afa, sizeof(afa));
        strcpy(afa.af_name, "dataready");
        setsockopt(sok, SOL_SOCKET, SO_ACCEPTFILTER, &afa, sizeof(afa));


The accept filter mechanism and the accf_data filter were introduced in Fx 4.0 .


This manual page and the filter were written by An Alfred Perlstein .