00492fb846
MFC after: 1 week Sponsored by: Chelsio Communications Differential Revision: https://reviews.freebsd.org/D27557
519 lines
13 KiB
Groff
519 lines
13 KiB
Groff
.\"-
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.\" Copyright (c) 2010 The FreeBSD Foundation
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.\" All rights reserved.
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.\"
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.\" This documentation was written by CK Software GmbH under sponsorship from
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.\" the FreeBSD Foundation.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd December 10, 2020
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.Dt VNET 9
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.Os
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.Sh NAME
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.Nm VNET
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.Nd "network subsystem virtualization infrastructure"
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.Sh SYNOPSIS
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.Cd "options VIMAGE"
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.Cd "options VNET_DEBUG"
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.Pp
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.In net/vnet.h
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.\"------------------------------------------------------------
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.Ss "Constants and Global Variables"
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.\"
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.Dv VNET_SETNAME
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.\" "set_vnet"
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.Dv VNET_SYMPREFIX
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.\" "vnet_entry_"
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.Vt extern struct vnet *vnet0;
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.\"------------------------------------------------------------
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.Ss "Variable Declaration"
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.Fo VNET
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.Fa "name"
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.Fc
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.\"
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.Fo VNET_NAME
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.Fa "name"
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.Fc
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.\"
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.Fo VNET_DECLARE
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.Fa "type" "name"
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.Fc
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.\"
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.Fo VNET_DEFINE
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.Fa "type" "name"
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.Fc
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.\"
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.Fo VNET_DEFINE_STATIC
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.Fa "type" "name"
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.Fc
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.\"
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.Bd -literal
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#define V_name VNET(name)
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.Ed
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.\" ------------------------------------------------------------
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.Ss "Virtual Instance Selection"
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.\"
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.Fo CRED_TO_VNET
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.Fa "struct ucred *"
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.Fc
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.\"
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.Fo TD_TO_VNET
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.Fa "struct thread *"
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.Fc
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.\"
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.Fo P_TO_VNET
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.Fa "struct proc *"
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.Fc
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.\"
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.Fo IS_DEFAULT_VNET
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.Fa "struct vnet *"
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.Fc
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.\"
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.Fo VNET_ASSERT
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.Fa exp msg
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.Fc
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.\"
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.Fo CURVNET_SET
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.Fa "struct vnet *"
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.Fc
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.\"
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.Fo CURVNET_SET_QUIET
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.Fa "struct vnet *"
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.Fc
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.\"
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.Fn CURVNET_RESTORE
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.\"
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.Fo VNET_ITERATOR_DECL
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.Fa "struct vnet *"
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.Fc
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.\"
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.Fo VNET_FOREACH
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.Fa "struct vnet *"
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.Fc
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.\" ------------------------------------------------------------
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.Ss "Locking"
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.\"
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.Fn VNET_LIST_RLOCK
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.Fn VNET_LIST_RUNLOCK
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.Fn VNET_LIST_RLOCK_NOSLEEP
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.Fn VNET_LIST_RUNLOCK_NOSLEEP
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.\" ------------------------------------------------------------
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.Ss "Startup and Teardown Functions"
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.\"
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.Ft "struct vnet *"
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.Fo vnet_alloc
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.Fa void
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.Fc
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.\"
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.Ft void
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.Fo vnet_destroy
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.Fa "struct vnet *"
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.Fc
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.\"
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.Fo VNET_SYSINIT
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.Fa ident
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.Fa "enum sysinit_sub_id subsystem"
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.Fa "enum sysinit_elem_order order"
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.Fa "sysinit_cfunc_t func"
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.Fa "const void *arg"
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.Fc
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.\"
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.Fo VNET_SYSUNINIT
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.Fa ident
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.Fa "enum sysinit_sub_id subsystem"
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.Fa "enum sysinit_elem_order order"
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.Fa "sysinit_cfunc_t func"
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.Fa "const void *arg"
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.Fc
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.\" ------------------------------------------------------------
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.Ss "Eventhandlers"
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.\"
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.Fo VNET_GLOBAL_EVENTHANDLER_REGISTER
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.Fa "const char *name"
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.Fa "void *func"
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.Fa "void *arg"
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.Fa "int priority"
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.Fc
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.\"
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.Fo VNET_GLOBAL_EVENTHANDLER_REGISTER_TAG
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.Fa "eventhandler_tag tag"
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.Fa "const char *name"
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.Fa "void *func"
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.Fa "void *arg"
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.Fa "int priority"
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.Fc
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.\" ------------------------------------------------------------
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.Ss "Sysctl Handling"
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.Fo SYSCTL_VNET_INT
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.Fa parent nbr name access ptr val descr
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.Fc
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.Fo SYSCTL_VNET_PROC
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.Fa parent nbr name access ptr arg handler fmt descr
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.Fc
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.Fo SYSCTL_VNET_STRING
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.Fa parent nbr name access arg len descr
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.Fc
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.Fo SYSCTL_VNET_STRUCT
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.Fa parent nbr name access ptr type descr
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.Fc
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.Fo SYSCTL_VNET_UINT
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.Fa parent nbr name access ptr val descr
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.Fc
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.Fo VNET_SYSCTL_ARG
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.Fa req arg1
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.Fc
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.\" ------------------------------------------------------------
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.Sh DESCRIPTION
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.Nm
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is the name of a technique to virtualize the network stack.
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The basic idea is to change global resources most notably variables into
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per network stack resources and have functions, sysctls, eventhandlers,
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etc. access and handle them in the context of the correct instance.
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Each (virtual) network stack is attached to a
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.Em prison ,
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with
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.Vt vnet0
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being the unrestricted default network stack of the base system.
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.Pp
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The global defines for
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.Dv VNET_SETNAME
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and
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.Dv VNET_SYMPREFIX
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are shared with
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.Xr kvm 3
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to access internals for debugging reasons.
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.\" ------------------------------------------------------------
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.Ss "Variable Declaration"
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.\"
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Variables are virtualized by using the
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.Fn VNET_DEFINE
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macro rather than writing them out as
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.Em type name .
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One can still use static initialization, e.g.,
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.Pp
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.Dl Li VNET_DEFINE(int, foo) = 1;
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.Pp
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Variables declared with the static keyword can use the
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.Fn VNET_DEFINE_STATIC
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macro, e.g.,
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.Pp
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.Dl Li VNET_DEFINE_STATIC(SLIST_HEAD(, bar), bars);
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.Pp
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Static initialization is not possible when the virtualized variable
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would need to be referenced, e.g., with
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.Dq TAILQ_HEAD_INITIALIZER() .
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In that case a
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.Fn VNET_SYSINIT
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based initialization function must be used.
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.Pp
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External variables have to be declared using the
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.Fn VNET_DECLARE
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macro.
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In either case the convention is to define another macro,
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that is then used throughout the implementation to access that variable.
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The variable name is usually prefixed by
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.Em V_
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to express that it is virtualized.
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The
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.Fn VNET
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macro will then translate accesses to that variable to the copy of the
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currently selected instance (see the
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.Sx "Virtual instance selection"
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section):
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.Pp
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.Dl Li #define V_name VNET(name)
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.Pp
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.Em NOTE:
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Do not confuse this with the convention used by
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.Xr VFS 9 .
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.Pp
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The
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.Fn VNET_NAME
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macro returns the offset within the memory region of the virtual network
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stack instance.
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It is usually only used with
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.Fn SYSCTL_VNET_*
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macros.
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.\" ------------------------------------------------------------
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.Ss "Virtual Instance Selection"
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.\"
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There are three different places where the current virtual
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network stack pointer is stored and can be taken from:
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.Bl -enum -offset indent
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.It
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a
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.Em prison :
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.Dl "(struct prison *)->pr_vnet"
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.Pp
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For convenience the following macros are provided:
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.Bd -literal -compact -offset indent
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.Fn CRED_TO_VNET "struct ucred *"
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.Fn TD_TO_VNET "struct thread *"
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.Fn P_TO_VNET "struct proc *"
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.Ed
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.It
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a
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.Em socket :
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.Dl "(struct socket *)->so_vnet"
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.It
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an
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.Em interface :
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.Dl "(struct ifnet *)->if_vnet"
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.El
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.Pp
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.\"
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In addition the currently active instance is cached in
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.Dq "curthread->td_vnet"
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which is usually only accessed through the
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.Dv curvnet
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macro.
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.Pp
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.\"
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To set the correct context of the current virtual network instance, use the
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.Fn CURVNET_SET
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or
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.Fn CURVNET_SET_QUIET
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macros.
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The
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.Fn CURVNET_SET_QUIET
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version will not record vnet recursions in case the kernel was compiled
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with
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.Cd "options VNET_DEBUG"
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and should thus only be used in well known cases, where recursion is
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unavoidable.
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Both macros will save the previous state on the stack and it must be restored
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with the
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.Fn CURVNET_RESTORE
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macro.
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.Pp
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.Em NOTE:
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As the previous state is saved on the stack, you cannot have multiple
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.Fn CURVNET_SET
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calls in the same block.
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.Pp
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.Em NOTE:
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As the previous state is saved on the stack, a
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.Fn CURVNET_RESTORE
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call has to be in the same block as the
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.Fn CURVNET_SET
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call or in a subblock with the same idea of the saved instances as the
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outer block.
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.Pp
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.Em NOTE:
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As each macro is a set of operations and, as previously explained, cannot
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be put into its own block when defined, one cannot conditionally set
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the current vnet context.
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The following will
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.Em not
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work:
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.Bd -literal -offset indent
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if (condition)
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CURVNET_SET(vnet);
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.Ed
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.Pp
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nor would this work:
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.Bd -literal -offset indent
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if (condition) {
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CURVNET_SET(vnet);
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}
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CURVNET_RESTORE();
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.Ed
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.Pp
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.\"
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Sometimes one needs to loop over all virtual instances, for example to update
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virtual from global state, to run a function from a
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.Xr callout 9
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for each instance, etc.
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For those cases the
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.Fn VNET_ITERATOR_DECL
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and
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.Fn VNET_FOREACH
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macros are provided.
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The former macro defines the variable that iterates over the loop,
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and the latter loops over all of the virtual network stack instances.
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See
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.Sx "Locking"
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for how to savely traverse the list of all virtual instances.
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.Pp
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.\"
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The
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.Fn IS_DEFAULT_VNET
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macro provides a safe way to check whether the currently active instance is the
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unrestricted default network stack of the base system
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.Pq Vt vnet0 .
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.Pp
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.\"
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The
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.Fn VNET_ASSERT
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macro provides a way to conditionally add assertions that are only active with
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.Cd "options VIMAGE"
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compiled in and either
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.Cd "options VNET_DEBUG"
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or
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.Cd "options INVARIANTS"
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enabled as well.
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It uses the same semantics as
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.Xr KASSERT 9 .
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.\" ------------------------------------------------------------
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.Ss "Locking"
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.\"
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For public access to the list of virtual network stack instances
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e.g., by the
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.Fn VNET_FOREACH
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macro, read locks are provided.
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Macros are used to abstract from the actual type of the locks.
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If a caller may sleep while traversing the list, it must use the
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.Fn VNET_LIST_RLOCK
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and
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.Fn VNET_LIST_RUNLOCK
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macros.
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Otherwise, the caller can use
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.Fn VNET_LIST_RLOCK_NOSLEEP
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and
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.Fn VNET_LIST_RUNLOCK_NOSLEEP .
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.\" ------------------------------------------------------------
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.Ss "Startup and Teardown Functions"
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.\"
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To start or tear down a virtual network stack instance the internal
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functions
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.Fn vnet_alloc
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and
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.Fn vnet_destroy
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are provided and called from the jail framework.
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They run the publicly provided methods to handle network stack
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startup and teardown.
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.Pp
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For public control, the system startup interface has been enhanced
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to not only handle a system boot but to also handle a virtual
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network stack startup and teardown.
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To the base system the
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.Fn VNET_SYSINIT
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and
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.Fn VNET_SYSUNINIT
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macros look exactly as if there were no virtual network stack.
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In fact, if
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.Cd "options VIMAGE"
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is not compiled in they are compiled to the standard
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.Fn SYSINIT
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macros.
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In addition to that they are run for each virtual network stack
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when starting or, in reverse order, when shutting down.
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.\" ------------------------------------------------------------
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.Ss "Eventhandlers"
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.\"
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Eventhandlers can be handled in two ways:
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.Pp
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.Bl -enum -offset indent -compact
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.It
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save the
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.Em tags
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returned in each virtual instance and properly free the eventhandlers
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on teardown using those, or
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.It
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use one eventhandler that will iterate over all virtual network
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stack instances.
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.El
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.Pp
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For the first case one can just use the normal
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.Xr EVENTHANDLER 9
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functions, while for the second case the
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.Fn VNET_GLOBAL_EVENTHANDLER_REGISTER
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and
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.Fn VNET_GLOBAL_EVENTHANDLER_REGISTER_TAG
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macros are provided.
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These differ in that
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.Fn VNET_GLOBAL_EVENTHANDLER_REGISTER_TAG
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takes an extra first argument that will carry the
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.Fa "tag"
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upon return.
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Eventhandlers registered with either of these will not run
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.Fa func
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directly but
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.Fa func
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will be called from an internal iterator function for each vnet.
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Both macros can only be used for eventhandlers that do not take
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additional arguments, as the variadic arguments from an
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.Xr EVENTHANDLER_INVOKE 9
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call will be ignored.
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.\" ------------------------------------------------------------
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.Ss "Sysctl Handling"
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.\"
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A
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.Xr sysctl 9
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can be virtualized by using one of the
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.Fn SYSCTL_VNET_*
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macros.
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.Pp
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They take the same arguments as the standard
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.Xr sysctl 9
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functions, with the only difference, that the
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.Fa ptr
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argument has to be passed as
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.Ql &VNET_NAME(foo)
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instead of
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.Ql &foo
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so that the variable can be selected from the correct memory
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region of the virtual network stack instance of the caller.
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.Pp
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For the very rare case a sysctl handler function would want to
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handle
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.Fa arg1
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itself the
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.Fn VNET_SYSCTL_ARG req arg1
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is provided that will translate the
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.Fa arg1
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argument to the correct memory address in the virtual network stack
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context of the caller.
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.\" ------------------------------------------------------------
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.Sh SEE ALSO
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.Xr jail 2 ,
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.Xr kvm 3 ,
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.Xr EVENTHANDLER 9 ,
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.\" .Xr pcpu 9 ,
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.Xr KASSERT 9 ,
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.Xr sysctl 9
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.\" .Xr SYSINIT 9
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.Pp
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Marko Zec, Implementing a Clonable Network Stack in the FreeBSD Kernel,
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USENIX ATC'03, June 2003, Boston
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.Sh HISTORY
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The virtual network stack implementation first appeared in
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.Fx 8.0 .
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.Sh AUTHORS
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.An -nosplit
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The
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.Nm
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framework was designed and implemented at the University of Zagreb by
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.An Marko Zec
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under sponsorship of the FreeBSD Foundation and NLnet Foundation,
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and later extended and refined by
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.An Bjoern A. Zeeb
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(also under FreeBSD Foundation sponsorship), and
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.An Robert Watson .
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.Pp
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This manual page was written by
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.An Bjoern A. Zeeb, CK Software GmbH,
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under sponsorship from the FreeBSD Foundation.
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