44aae623ab
This adds a new ng_device command, NGM_DEVICE_ETHERALIGN, which has no associated args. After the command arrives, the device begins adjusting all packets sent out its hook to have ETHER_ALIGN bytes of padding at the beginning of the packet. The ETHER_ALIGN padding is added only when running on an architecture that requires strict alignment of IP headers (based on the __NO_STRICT_ALIGNMENT macro, which is only #define'd on x86 as of this writing). This also adds ascii <-> binary command translation to ng_device, both for the existing NGM_DEVICE_GET_DEVNAME and the new ETHERALIGN command. This also gives a name to every ng_device node when it is constructed, using the cdev device name (ngd0, ngd1, etc). This makes it easier to address command msgs to the device using ngctl(8). Reviewed by: donner, ray, adrian Differential Revision: https://reviews.freebsd.org/D32905 MFC after: 1 week
105 lines
3.3 KiB
Groff
105 lines
3.3 KiB
Groff
.\" Copyright (c) 2002 Mark Santcroos <marks@ripe.net>
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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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.\" 3. The name of the author may not be used to endorse or promote products
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.\" derived from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd November 8, 2021
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.Dt NG_DEVICE 4
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.Os
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.Sh NAME
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.Nm ng_device
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.Nd device netgraph node type
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.Sh SYNOPSIS
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.In netgraph/ng_device.h
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.Sh DESCRIPTION
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A
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.Nm device
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node is both a netgraph node and a system device interface.
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When a
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.Nm device
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node is created, a new device entry appears which is accessible via the
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regular file operators such as
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.Xr open 2 ,
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.Xr close 2 ,
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.Xr read 2 ,
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.Xr write 2 ,
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etc.
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.Pp
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The first node is created as
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.Pa /dev/ngd0 ,
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subsequent nodes are
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.Pa /dev/ngd1 , /dev/ngd2 ,
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etc.
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.Sh HOOKS
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A
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.Nm device
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node has a single hook with an arbitrary name.
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All data coming in over the hook will be presented to the device
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for
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.Xr read 2 .
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All data coming in from the device entry by
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.Xr write 2
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will be forwarded to the hook.
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.Sh CONTROL MESSAGES
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The
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.Nm device
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node supports the generic control messages, plus the following:
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.Bl -tag -width 3n
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.It Dv NGM_DEVICE_GET_DEVNAME
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Returns the device name corresponding to the node.
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.It Dv NGM_DEVICE_ETHERALIGN
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Apply the system ETHER_ALIGN offset to mbufs sent out the node's hook,
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if running on an architecture that requires strict alignment.
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Use this option when the data being injected via the device node ultimately
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ends up being fed into the protocol stack as ethernet packets (e.g., via
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an
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.Xr ng_eiface 4
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node).
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.El
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.\" Additionally, the node accepts
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.\" .Xr ioctl 2 Ns s
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.\" from the device entry.
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.\" These will be encapsulated into
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.\" .Xr netgraph 4
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.\" messages and send out to the hook.
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.Sh SHUTDOWN
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This node shuts down upon receipt of a
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.Dv NGM_SHUTDOWN
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control message, or upon hook disconnection.
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The associated device entry is removed and becomes available
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for use by future
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.Nm device
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nodes.
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.Sh SEE ALSO
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.Xr netgraph 4 ,
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.Xr ngctl 8
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.Sh HISTORY
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The
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.Nm device
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node type was first implemented in
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.Fx 5.0 .
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.Sh AUTHORS
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.An Mark Santcroos Aq Mt marks@ripe.net
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.An Gleb Smirnoff Aq Mt glebius@FreeBSD.org
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