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authorken <ken@FreeBSD.org>2012-01-26 17:28:33 +0000
committerken <ken@FreeBSD.org>2012-01-26 17:28:33 +0000
commitcd0b224af303778d82d643263ea5e08ae3c2d239 (patch)
tree02d246e318dfa9bd9bf3c9953aa4289b14e0a197 /share/man
parent7ebf2a01cf80cb57e9b9cf58123fef55fa1ba239 (diff)
downloadFreeBSD-src-cd0b224af303778d82d643263ea5e08ae3c2d239.zip
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Start sentences on a new line, and fix a few other nits.
Prompted by: gjb MFC after: 1 week
Diffstat (limited to 'share/man')
-rw-r--r--share/man/man4/xnb.477
1 files changed, 42 insertions, 35 deletions
diff --git a/share/man/man4/xnb.4 b/share/man/man4/xnb.4
index f2d8f8a..bb2cd1d 100644
--- a/share/man/man4/xnb.4
+++ b/share/man/man4/xnb.4
@@ -1,6 +1,5 @@
.\" Copyright (c) 2012 Spectra Logic Corporation
-.\" All rights reserved.
-.\"
+.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
@@ -30,7 +29,7 @@
.\" Authors: Alan Somers (Spectra Logic Corporation)
.\"
.\" $FreeBSD$
-.\"
+.\"
.Dd January 6, 2012
.Dt XNB 4
@@ -50,24 +49,26 @@ The
.Nm
driver provides the back half of a paravirtualized
.Xr xen 4
-network connection. The netback and netfront drivers appear to their
-respective operating systems as Ethernet devices linked by a crossover cable.
+network connection.
+The netback and netfront drivers appear to their respective operating
+systems as Ethernet devices linked by a crossover cable.
Typically,
.Nm
will run on Domain 0 and the netfront driver will run on a guest domain.
However, it is also possible to run
.Nm
-on a guest domain. It may be bridged or routed to provide the netfront's
+on a guest domain.
+It may be bridged or routed to provide the netfront's
domain access to other guest domains or to a physical network.
.Pp
In most respects, the
.Nm
-device appears to the OS as an other Ethernet device. It can be configured at
-runtime entirely with
-.Xr ifconfig 8
-\&. In particular, it supports MAC changing, arbitrary MTU sizes, checksum
-offload for IP, UDP, and TCP for both receive and transmit, and TSO. However,
-see
+device appears to the OS as an other Ethernet device.
+It can be configured at runtime entirely with
+.Xr ifconfig 8 .
+In particular, it supports MAC changing, arbitrary MTU sizes, checksum
+offload for IP, UDP, and TCP for both receive and transmit, and TSO.
+However, see
.Sx CAVEATS
before enabling txcsum, rxcsum, or tso.
.Sh SYSCTL VARIABLES
@@ -76,47 +77,51 @@ The following read-only variables are available via
.Bl -tag -width indent
.It Va dev.xnb.%d.dump_rings
Displays information about the ring buffers used to pass requests between the
-netfront and netback. Mostly useful for debugging, but can also be used to
+netfront and netback.
+Mostly useful for debugging, but can also be used to
get traffic statistics.
.It Va dev.xnb.%d.unit_test_results
-Runs a builtin suite of unit tests and displays the results. Does not affect
-the operation of the driver in any way. Note that the test suite simulates
-error conditions; this will result in error messages being printed to the
-system system log.
+Runs a builtin suite of unit tests and displays the results.
+Does not affect the operation of the driver in any way.
+Note that the test suite simulates error conditions; this will result in
+error messages being printed to the system system log.
.Sh CAVEATS
Packets sent through Xennet pass over shared memory, so the protocol includes
-no form of link-layer checksum or CRC. Furthermore, Xennet drivers always
-report to their hosts that they support receive and transmit checksum
-offloading. They "offload" the checksum calculation by simply skipping it.
+no form of link-layer checksum or CRC.
+Furthermore, Xennet drivers always report to their hosts that they support
+receive and transmit checksum offloading.
+They "offload" the checksum calculation by simply skipping it.
That works fine for packets that are exchanged between two domains on the same
-machine. However, when a Xennet interface is bridged to a physical interface,
+machine.
+However, when a Xennet interface is bridged to a physical interface,
a correct checksum must be attached to any packets bound for that physical
-interface. Currently, FreeBSD lacks any mechanism for an ethernet device to
+interface.
+Currently, FreeBSD lacks any mechanism for an ethernet device to
inform the OS that newly received packets are valid even though their checksums
-are not. So if the netfront driver is configured to offload checksum
-calculations, it will pass non-checksumed packets to
-.Nm
-, which must then calculate the checksum in software before passing the packet
+are not.
+So if the netfront driver is configured to offload checksum calculations,
+it will pass non-checksumed packets to
+.Nm ,
+which must then calculate the checksum in software before passing the packet
to the OS.
.Pp
For this reason, it is recommended that if
.Nm
is bridged to a physcal interface, then transmit checksum offloading should be
-disabled on the netfront. The Xennet protocol does not have any mechanism for
-the netback to request the netfront to do this; the operator must do it
-manually.
+disabled on the netfront.
+The Xennet protocol does not have any mechanism for the netback to request
+the netfront to do this; the operator must do it manually.
.Sh SEE ALSO
.Xr arp 4 ,
.Xr netintro 4 ,
.Xr ng_ether 4 ,
-.Xr ifconfig 8 ,
-.Xr xen 4
+.Xr xen 4 ,
+.Xr ifconfig 8
.Sh HISTORY
The
.Nm
device driver first appeared in
-.Fx 10.0
-.
+.Fx 10.0 .
.Sh AUTHORS
The
.Nm
@@ -130,5 +135,7 @@ and
The
.Nm
driver does not properly checksum UDP datagrams that span more than one
-Ethernet frame. Nor does it correctly checksum IPv6 packets. To workaround
-that bug, disable transmit checksum offloading on the netfront driver.
+Ethernet frame.
+Nor does it correctly checksum IPv6 packets.
+To workaround that bug, disable transmit checksum offloading on the
+netfront driver.
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