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diff --git a/share/man/man9/accept_filter.9 b/share/man/man9/accept_filter.9 new file mode 100644 index 0000000..3f89a0c --- /dev/null +++ b/share/man/man9/accept_filter.9 @@ -0,0 +1,152 @@ +.\" +.\" Copyright (c) 2000 Alfred Perlstein +.\" +.\" All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR +.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES +.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. +.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT, +.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT +.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, +.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY +.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT +.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF +.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. +.\" +.\" $FreeBSD$ +.\" " +.Dd June 25, 2000 +.Dt ACCEPT_FILTER 9 +.Os +.Sh NAME +.Nm accept_filter , +.Nm accept_filt_add , +.Nm accept_filt_del , +.Nm accept_filt_generic_mod_event , +.Nm accept_filt_get +.Nd filter incoming connections +.Sh SYNOPSIS +.In sys/types.h +.In sys/module.h +.In sys/socket.h +.Fd #define ACCEPT_FILTER_MOD +.In sys/socketvar.h +.Ft int +.Fn accept_filt_add "struct accept_filter *filt" +.Ft int +.Fn accept_filt_del "char *name" +.Ft int +.Fn accept_filt_generic_mod_event "module_t mod" "int event" "void *data" +.Ft struct accept_filter * +.Fn accept_filt_get "char *name" +.Sh DESCRIPTION +Accept filters allow an application to request +that the kernel pre-process incoming connections. +An accept filter is requested via the +.Xr setsockopt 2 +system call, passing in an +.Fa optname +of +.Dv SO_ACCEPTFILTER . +.Sh IMPLEMENTATION NOTES +A module that wants to be an accept filter +must provide a +.Vt "struct accept_filter" +to the system: +.Bd -literal +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 */ +}; +.Ed +.Pp +The module should register it with the function +.Fn accept_filt_add , +passing a pointer to a +.Vt "struct accept_filter" , +allocated with +.Xr malloc 9 . +.Pp +The fields of +.Vt "struct accept_filter" +are as follows: +.Bl -tag -width ".Va accf_callback" +.It Va accf_name +Name of the filter; +this is how it will be accessed from userland. +.It Va 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. +.It Va accf_create +Called whenever a +.Xr setsockopt 2 +installs the filter onto +a listening socket. +.It Va accf_destroy +Called whenever the user removes the accept filter on the socket. +.El +.Pp +The +.Fn accept_filt_del +function +passed the same string used in +.Va accept_filter.accf_name +during registration with +.Fn accept_filt_add , +the kernel will then disallow and further userland use of the filter. +.Pp +The +.Fn accept_filt_get +function is used internally to locate which accept filter to use via the +.Xr setsockopt 2 +system call. +.Pp +The +.Fn 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 +.Xr DECLARE_MODULE 9 +macro. +.Sh SEE ALSO +.Xr setsockopt 2 , +.Xr accf_data 9 , +.Xr accf_dns 9 , +.Xr accf_http 9 , +.Xr malloc 9 +.Sh HISTORY +The accept filter mechanism was introduced in +.Fx 4.0 . +.Sh AUTHORS +This manual page was written by +.An -nosplit +.An Alfred Perlstein , +.An Sheldon Hearn +and +.An Jeroen Ruigrok van der Werven. +.Pp +The accept filter concept was pioneered by +.An David Filo +at Yahoo!\& +and refined to be a loadable module system by +.An Alfred Perlstein . |
