ACCF_DNS(9FREEBSD) - Linux man page online | System kernel interfaces

Buffer incoming DNS requests until the whole first request is present.

July 16, 2008
ACCF_DNS(9) BSD Kernel Developer's Manual ACCF_DNS(9)


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 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.


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_data(9), accf_http(9)


The accept filter mechanism was introduced in FreeBSD 4.0.


This manual page and the filter were written by David Malone.
BSD July 16, 2008 BSD
This manual Reference Other manuals
accf_dns(9freebsd) referred by accept_filt_add(9freebsd) | accept_filt_del(9freebsd) | accept_filt_generic_mod_event(9freebsd) | accept_filt_get(9freebsd) | accept_filter(9freebsd) | accf_data(9freebsd)
refer to accept_filter(9freebsd) | accf_data(9freebsd) | accf_http(9freebsd) | getsockopt(2)
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