'\" te
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.\" Copyright (C) 2012, Joyent, Inc. All Rights Reserved.
.\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License").  You may not use this file except in compliance with the License.
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.TH NET_HOOK_REGISTER 9F "Mar 5, 2012"
.SH NAME
net_hook_register \- add a hook to be called in event processing
.SH SYNOPSIS
.nf
#include <sys/neti.h>

\fBint\fR \fBnet_hook_register\fR(\fBnet_handle_t\fR \fIinfo\fR, \fBchar\fR *\fIevent\fR, \fBhook_t\fR *\fIhook\fR);
.fi

.SH INTERFACE LEVEL
illumos DDI specific (illumos DDI).
.SH PARAMETERS
.ne 2
.na
\fB\fIinfo\fR\fR
.ad
.RS 8n
value returned from a successful call to \fBnet_protocol_register()\fR.
.RE

.sp
.ne 2
.na
\fB\fIname\fR\fR
.ad
.RS 8n
unique name for this hook.
.RE

.sp
.ne 2
.na
\fB\fIhook\fR\fR
.ad
.RS 8n
pointer to a \fBhook_t\fR structure.
.RE

.SH DESCRIPTION
The \fBnet_hook_register()\fR function uses hooks that allow callbacks to be
registered with events that belong to a network protocol. A successful call to
\fBnet_hook_register()\fR requires that a valid handle for a network protocol be
provided (the \fIinfo\fR parameter), along with a unique name and a hook
description that includes a reference to an available event. No two hooks on the
same netstack may share a name.
.sp
.LP
While it is possible to use the same \fBhook_t\fR structure with multiple calls
to \fBnet_hook_register()\fR, it is not encouraged.
.sp
.LP
The \fBhook_t\fR structure passed in with this function is described by
\fBhook_t\fR(9S). The following describes how this structure is used.
.sp
.ne 2
.na
\fB\fBh_func\fR\fR
.ad
.RS 23n
Must be non-NULL and represent a function that fits the specified interface.
.RE

.sp
.ne 2
.na
\fB\fBh_name\fR\fR
.ad
.RS 23n
Gives the hook a name that represents its owner. No duplication of \fBh_name\fR
among the hooks present for an event is allowed.
.RE

.sp
.ne 2
.na
\fB\fBh_flags\fR\fR
.ad
.RS 23n
Currently unused and must be set to 0.
.RE

.sp
.ne 2
.na
\fB\fBh_hint, h_hintvalue\fR\fR
.ad
.RS 23n
Specify a hint to \fBnet_hook_register()\fR on how to insert this hook. If the
hint cannot be specified, then an error is returned.
.RE

.sp
.ne 2
.na
\fB\fBh_arg;\fR\fR
.ad
.RS 23n
May take any value that the consumer wishes to have passed back when the hook
is activated.
.RE

.SH RETURN VALUES
If the \fBnet_hook_register()\fR function succeeds, 0 is returned. Otherwise,
one of the following errors is returned:
.sp
.ne 2
.na
\fBENOMEM\fR
.ad
.RS 10n
The system cannot allocate any more memory to support registering this hook.
.RE

.sp
.ne 2
.na
\fBENXIO\fR
.ad
.RS 10n
A hook cannot be found among the given family of events.
.RE

.sp
.ne 2
.na
\fBEEXIST\fR
.ad
.RS 10n
A hook with the given \fBh_name\fR already exists on that event.
.RE

.sp
.ne 2
.na
\fBESRCH\fR
.ad
.RS 10n
A before or after dependency cannot be satisfied due to the hook with
.RE

.sp
.ne 2
.na
\fBEBUSY\fR
.ad
.RS 10n
The \fBh_hint\fR field specifies a hint that cannot currently be satisfied
because it conflicts with another hook. An example of this might be specifying
\fBHH_FIRST\fR or \fBHH_LAST\fR when another hook has already been registered
with this value.
.RE

.sp
.ne 2
.na
\fBESHUTDOWN\fR
.ad
.RS 10n
The netstack corresponding to \fIinfo\fR is condemned or no longer exists.

.SH CONTEXT
The \fBnet_hook_register()\fR function may be called from user  or kernel
context.
.SH ATTRIBUTES
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Committed
.TE

.SH SEE ALSO
.BR net_hook_unregister (9F),
.BR hook_t (9S)