Проект OpenNet: MAN accept_filter (9) Ядро (FreeBSD и Linux)

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accept_filter (9)

>> accept_filter (9) ( FreeBSD man: Ядро )

BSD mandoc

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>
Fd #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 Fa optname of SO_ACCEPTFILTER

IMPLEMENTATION NOTES

A module that wants to be an accept filter must provide a Vt 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 Vt struct accept_filter , allocated with malloc(9).

The fields of Vt 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 argument field to load and unload themselves. This function can be used in the Vt moduledata_t struct for the DECLARE_MODULE9 macro.