sk_attach_filter(9) [centos man page]

SK_ATTACH_FILTER(9)						 Linux Networking					       SK_ATTACH_FILTER(9)

NAME

       sk_attach_filter - attach a socket filter

SYNOPSIS

       int sk_attach_filter(struct sock_fprog * fprog, struct sock * sk);

ARGUMENTS

       fprog
	   the filter program

       sk
	   the socket to use

DESCRIPTION

       Attach the user's filter code. We first run some sanity checks on it to make sure it does not explode on us later. If an error occurs or
       there is insufficient memory for the filter a negative errno code is returned. On success the return is zero.

COPYRIGHT

Kernel Hackers Manual 3.10					     June 2014						       SK_ATTACH_FILTER(9)

ACCEPT_FILTER(9)					   BSD Kernel Developer's Manual					  ACCEPT_FILTER(9)

NAME

     accept_filter, accept_filt_add, accept_filt_del, accept_filt_generic_mod_event, accept_filt_get -- filter incoming connections

SYNOPSIS

     #include <sys/types.h>
     #include <sys/module.h>
     #include <sys/socket.h>
     #define ACCEPT_FILTER_MOD
     #include <sys/socketvar.h>

     int
     accept_filt_add(struct accept_filter *filt);

     int
     accept_filt_del(char *name);

     int
     accept_filt_generic_mod_event(module_t mod, int event, void *data);

     struct accept_filter *
     accept_filt_get(char *name);

DESCRIPTION

     Accept filters allow an application to request that the kernel pre-process incoming connections.  An accept filter is requested via the
     setsockopt(2) system call, passing in an optname of SO_ACCEPTFILTER.

IMPLEMENTATION NOTES

     A module that wants to be an accept filter must provide a struct accept_filter to the system:

     struct accept_filter {
	     char    accf_name[16];
	     void    (*accf_callback)(struct socket *so, void *arg, int waitflag);
	     void *  (*accf_create)(struct socket *so, char *arg);
	     void    (*accf_destroy)(struct socket *so);
	     SLIST_ENTRY(accept_filter) accf_next;   /* next on the list */
     };

     The module should register it with the function accept_filt_add(), passing a pointer to a struct accept_filter, allocated with malloc(9).

     The fields of struct accept_filter are as follows:

     accf_name	    Name of the filter; this is how it will be accessed from userland.

     accf_callback  The callback that the kernel will do once the connection is established.  It is the same as a socket upcall and will be called
		    when the connection is established and whenever new data arrives on the socket, unless the callback modifies the socket's
		    flags.

     accf_create    Called whenever a setsockopt(2) installs the filter onto a listening socket.

     accf_destroy   Called whenever the user removes the accept filter on the socket.

     The accept_filt_del() function passed the same string used in accept_filter.accf_name during registration with accept_filt_add(), the kernel
     will then disallow and further userland use of the filter.

     The accept_filt_get() function is used internally to locate which accept filter to use via the setsockopt(2) system call.

     The accept_filt_generic_mod_event() function provides a simple way to avoid duplication of code for accept filters which do not use the argu-
     ment field to load and unload themselves.	This function can be used in the moduledata_t struct for the DECLARE_MODULE(9) macro.

SEE ALSO

     setsockopt(2), accf_data(9), accf_dns(9), accf_http(9), malloc(9)

HISTORY

     The accept filter mechanism was introduced in FreeBSD 4.0.

AUTHORS

     This manual page was written by Alfred Perlstein, Sheldon Hearn and Jeroen Ruigrok van der Werven.

     The accept filter concept was pioneered by David Filo at Yahoo! and refined to be a loadable module system by Alfred Perlstein.

BSD
								   June 25, 2000							       BSD