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26 .\" $FreeBSD: src/share/man/man9/accept_filter.9,v 1.2.2.6 2002/12/29 16:35:39 schweikh Exp $
35 .Nm accept_filt_generic_mod_event ,
37 .Nd filter incoming connections
43 .Fn accept_filt_add "struct accept_filter *filt"
45 .Fn accept_filt_del "char *name"
47 .Fn accept_filt_generic_mod_event "module_t mod" "int event" "void *data"
48 .Ft struct accept_filter *
49 .Fn accept_filt_get "char *name"
51 Accept filters allow an application to request
52 that the kernel pre-process incoming connections.
53 An accept filter is requested via the
55 system call, passing in an
59 .Sh IMPLEMENTATION NOTES
60 A module that wants to be an accept filter
61 must provide a struct accept_filter to the system:
63 struct accept_filter {
66 __P((struct socket *so, void *arg, int waitflag));
68 __P((struct socket *so, char *arg));
70 __P((struct socket *so));
71 SLIST_ENTRY(accept_filter) accf_next; /* next on the list */
75 The module should register it with the function
77 passing a pointer to a struct accept_filter, allocated with
81 .Fa struct accept_filter
83 .Bl -tag -width accf_callbackXXX
86 this is how it will be accessed from userland.
88 The callback that the kernel will do
89 once the connection is established.
90 It is the same as a socket upcall
91 and will be called when the connection is established
92 and whenever new data arrives on the socket,
93 unless the callback modifies the socket's flags.
97 installs the filter onto
100 Called whenever the user removes the accept filter on the socket.
104 passed the same string used in accept_filter.accf_name during registration
106 .Fn accept_filt_add ,
107 the kernel will then disallow and further userland use of the filter.
110 is used internally to locate which accept filter to use via the
114 .Fn accept_filt_generic_mod_event
115 provides a simple way to avoid duplicate
116 code for accept filters which don't use
117 argument field to load and unload
118 themselves. It is a function that can be
119 put in the load/unload struct
129 The accept filter mechanism was introduced in
132 This manual page was written by
133 .An Alfred Perlstein ,
134 Sheldon Hearn and Jeroen Ruigrok van der Werven.
135 The accept filter concept was pioneered by David Filo at Yahoo!
136 and refined to be a loadable module system by Alfred Perlstein.