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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 $
27 .\" $DragonFly: src/share/man/man9/accept_filter.9,v 1.4 2006/10/19 18:44:00 swildner Exp $
36 .Nm accept_filt_generic_mod_event ,
38 .Nd filter incoming connections
44 .Fn accept_filt_add "struct accept_filter *filt"
46 .Fn accept_filt_del "char *name"
48 .Fn accept_filt_generic_mod_event "module_t mod" "int event" "void *data"
49 .Ft struct accept_filter *
50 .Fn accept_filt_get "char *name"
52 Accept filters allow an application to request
53 that the kernel pre-process incoming connections.
54 An accept filter is requested via the
56 system call, passing in an
60 .Sh IMPLEMENTATION NOTES
61 A module that wants to be an accept filter
62 must provide a struct accept_filter to the system:
64 struct accept_filter {
67 (struct socket *so, void *arg, int waitflag);
69 (struct socket *so, char *arg);
72 SLIST_ENTRY(accept_filter) accf_next; /* next on the list */
76 The module should register it with the function
78 passing a pointer to a struct accept_filter, allocated with
82 .Fa struct accept_filter
84 .Bl -tag -width accf_callbackXXX
87 this is how it will be accessed from userland.
89 The callback that the kernel will do
90 once the connection is established.
91 It is the same as a socket upcall
92 and will be called when the connection is established
93 and whenever new data arrives on the socket,
94 unless the callback modifies the socket's flags.
98 installs the filter onto
101 Called whenever the user removes the accept filter on the socket.
105 passed the same string used in accept_filter.accf_name during registration
107 .Fn accept_filt_add ,
108 the kernel will then disallow and further userland use of the filter.
111 is used internally to locate which accept filter to use via the
115 .Fn accept_filt_generic_mod_event
116 provides a simple way to avoid duplicate
117 code for accept filters which don't use
118 argument field to load and unload
119 themselves. It is a function that can be
120 put in the load/unload struct
130 The accept filter mechanism was introduced in
133 This manual page was written by
134 .An Alfred Perlstein ,
135 Sheldon Hearn and Jeroen Ruigrok van der Werven.
136 The accept filter concept was pioneered by David Filo at Yahoo!
137 and refined to be a loadable module system by Alfred Perlstein.