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diff --git a/static/freebsd/man4/xnb.4 3.html b/static/freebsd/man4/xnb.4 3.html new file mode 100644 index 00000000..0b35e750 --- /dev/null +++ b/static/freebsd/man4/xnb.4 3.html @@ -0,0 +1,111 @@ +<table class="head"> + <tr> + <td class="head-ltitle">XNB(4)</td> + <td class="head-vol">Device Drivers Manual</td> + <td class="head-rtitle">XNB(4)</td> + </tr> +</table> +<div class="manual-text"> +<section class="Sh"> +<h1 class="Sh" id="NAME"><a class="permalink" href="#NAME">NAME</a></h1> +<p class="Pp"><code class="Nm">xnb</code> — <span class="Nd">Xen + Paravirtualized Backend Ethernet Driver</span></p> +</section> +<section class="Sh"> +<h1 class="Sh" id="SYNOPSIS"><a class="permalink" href="#SYNOPSIS">SYNOPSIS</a></h1> +<p class="Pp">To compile this driver into the kernel, place the following lines + in your kernel configuration file:</p> +<div class="Bd Pp Bd-indent"><code class="Cd">options XENHVM</code> +<br/> +<code class="Cd">device xenpci</code></div> +</section> +<section class="Sh"> +<h1 class="Sh" id="DESCRIPTION"><a class="permalink" href="#DESCRIPTION">DESCRIPTION</a></h1> +<p class="Pp">The <code class="Nm">xnb</code> driver provides the back half of a + paravirtualized <a class="Xr">xen(4)</a> network connection. The netback and + netfront drivers appear to their respective operating systems as Ethernet + devices linked by a crossover cable. Typically, <code class="Nm">xnb</code> + will run on Domain 0 and the netfront driver will run on a guest domain. + However, it is also possible to run <code class="Nm">xnb</code> on a guest + domain. It may be bridged or routed to provide the netfront domain access to + other guest domains or to a physical network.</p> +<p class="Pp">In most respects, the <code class="Nm">xnb</code> device appears + to the OS as any other Ethernet device. It can be configured at runtime + entirely with <a class="Xr">ifconfig(8)</a>. 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 + <a class="Sx" href="#CAVEATS">CAVEATS</a> before enabling txcsum, rxcsum, or + tso.</p> +</section> +<section class="Sh"> +<h1 class="Sh" id="SYSCTL_VARIABLES"><a class="permalink" href="#SYSCTL_VARIABLES">SYSCTL + VARIABLES</a></h1> +<p class="Pp">The following read-only variables are available via + <a class="Xr">sysctl(8)</a>:</p> +<dl class="Bl-tag"> + <dt id="dev.xnb._d.dump_rings"><var class="Va">dev.xnb.%d.dump_rings</var></dt> + <dd>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 get traffic statistics.</dd> + <dt id="dev.xnb._d.unit_test_results"><var class="Va">dev.xnb.%d.unit_test_results</var></dt> + <dd>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 log.</dd> +</dl> +</section> +<section class="Sh"> +<h1 class="Sh" id="SEE_ALSO"><a class="permalink" href="#SEE_ALSO">SEE + ALSO</a></h1> +<p class="Pp"><a class="Xr">arp(4)</a>, <a class="Xr">netintro(4)</a>, + <a class="Xr">ng_ether(4)</a>, <a class="Xr">xen(4)</a>, + <a class="Xr">ifconfig(8)</a></p> +</section> +<section class="Sh"> +<h1 class="Sh" id="HISTORY"><a class="permalink" href="#HISTORY">HISTORY</a></h1> +<p class="Pp">The <code class="Nm">xnb</code> device driver first appeared in + <span class="Ux">FreeBSD 10.0</span>.</p> +</section> +<section class="Sh"> +<h1 class="Sh" id="AUTHORS"><a class="permalink" href="#AUTHORS">AUTHORS</a></h1> +<p class="Pp">The <code class="Nm">xnb</code> driver was written by + <span class="An">Alan Somers</span> + <<a class="Mt" href="mailto:asomers@FreeBSD.org">asomers@FreeBSD.org</a>> + and John Suykerbuyk.</p> +</section> +<section class="Sh"> +<h1 class="Sh" id="CAVEATS"><a class="permalink" href="#CAVEATS">CAVEATS</a></h1> +<p class="Pp">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. 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, a correct checksum must be attached to any packets + bound for that physical interface. Currently, + <span class="Ux">FreeBSD</span> 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 + <code class="Nm">xnb</code>, which must then calculate the checksum in + software before passing the packet to the OS.</p> +<p class="Pp">For this reason, it is recommended that if + <code class="Nm">xnb</code> is bridged to a physical 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.</p> +</section> +<section class="Sh"> +<h1 class="Sh" id="BUGS"><a class="permalink" href="#BUGS">BUGS</a></h1> +<p class="Pp">The <code class="Nm">xnb</code> 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.</p> +</section> +</div> +<table class="foot"> + <tr> + <td class="foot-date">June 6, 2014</td> + <td class="foot-os">FreeBSD 15.0</td> + </tr> +</table> |