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<html><head><title>Gavare's eXperimental Emulator: Networking</title> |
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<b>Gavare's eXperimental Emulator:</b></font><br> |
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<font color="#000000" size="6"><b>Networking</b> |
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</font></td></tr></table></td></tr></table><p> |
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$Id: networking.html,v 1.3 2006/09/26 08:49:35 debug Exp $ |
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Copyright (C) 2003-2006 Anders Gavare. All rights reserved. |
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Redistribution and use in source and binary forms, with or without |
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<a href="./">Back to the index</a> |
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<p><br> |
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<h2>Networking</h2> |
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<p> |
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<ul> |
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<li><a href="#intro">Introduction</a> |
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<li><a href="#multihost">Network across multiple hosts</a> |
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<li><a href="#direct_example_1">Direct-access example 1: udp_snoop</a> |
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</ul> |
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<p><br> |
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<a name="intro"></a> |
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<h3>Introduction:</h3> |
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GXemul's current networking layer supports two modes: |
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<p><ol> |
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<li>A NAT-like layer, which allows guest OSes to access the outside |
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internet world (IPv4 only, so far). When only one machine is being |
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emulated, the following default values apply to the guest OS:<pre> |
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IPv4 address: 10.0.0.1 |
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Netmask: 255.0.0.0 |
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Gateway / default route: 10.0.0.254 |
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Nameserver: 10.0.0.254 |
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</pre>To the outside world, it will seem as if the host is doing all the |
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networking, since the emulator is just a normal user process |
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on the host. |
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<p> |
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<li>A direct-access layer, allowing external tools to read/write raw |
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ethernet packages from/to the emulator. |
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</ol> |
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<p><i>NOTE:</i> Both these modes have problems. The NAT-like layer is very |
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"hackish" and was only meant as a proof-of-concept, to see if networking |
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like this would work with e.g. NetBSD as a guest OS. (If you are |
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interested in the technical details, and the reasons why NAT networking is |
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implemented this way, you might want to read the <a |
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href="technical.html#net"> networking section in the technical |
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documentation</a>.) Because of the obvious limitations with the NAT |
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approach, I have also included support for direct packet access, but this |
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is not designed for security or anything like that. |
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<p><font color="#ff0000">Use the networking features at your own risk. |
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</font> |
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<p>The emulated machine must of course have a NIC which is emulated |
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sufficiently. At the moment, the following NICs should work: |
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<ul> |
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<li><tt><b>ether</b></tt>, the "fake" experimental ethernet device |
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(documented <a href="experiments.html#expdevices_ether">here</a>) |
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<li><tt><b>le</b></tt>, Turbochannel Lance Ethernet, as used in |
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DECstation 5000/200 ("3max") |
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<li><tt><b>mec</b></tt>, the SGI O2's ethernet controller |
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<li><tt><b>dec21143</b></tt>, Digital's 21143 NIC (known as <tt>dc</tt> |
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in OpenBSD, or <tt>tlp</tt> in NetBSD) |
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</ul> |
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<p><br> |
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<a name="multihost"></a> |
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<h3>Network across multiple hosts:</h3> |
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<p>The way to emulate a network of multiple emulated machines, whether |
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they are actually running on the same physical host, or on multiple hosts, |
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is to use <a href="configfiles.html">configuration files</a>, and the |
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"direct-access" method of networking. |
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<p>Although it <i>is</i> possible to have more than one machine per |
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configuration file, I strongly recommend against it. Please use one |
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configuration file for one emulated machine. |
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<p>Here is a simple example: |
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<p><table border="0" width="100%"><tr><td width="40"> </td> |
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<td><pre> |
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<font color="#2020cf">! Configuration file for a |
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! "client" machine, netbooting |
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! of another machine.</font> |
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<b>net(</b> |
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<b>local_port(15000)</b> |
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<b>add_remote(<font color="#ff003f">"localhost:15001"</font>)</b> |
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<b>)</b> |
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<b>machine(</b> |
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<b>name(<font color="#ff003f">"client machine"</font>)</b> |
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<b>serial_nr(1)</b> <font color="#2020cf">! 10.0.0.1</font> |
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<b>type(<font color="#ff003f">"sgi"</font>)</b> |
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<b>subtype(<font color="#ff003f">"o2"</font>)</b> |
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<b>load(<font color="#ff003f">"netbsd-GENERIC32_IP3x.gz"</font>)</b> |
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<b>)</b> |
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</pre></td><td width="20"> </td><td><pre> |
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<font color="#2020cf">! Configuration file for the |
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! "server" machine.</font> |
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<b>net(</b> |
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<b>local_port(15001)</b> |
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<b>add_remote(<font color="#ff003f">"localhost:15000"</font>)</b> |
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<b>)</b> |
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<b>machine(</b> |
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<b>name(<font color="#ff003f">"nfs server"</font>)</b> |
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<b>serial_nr(2)</b> <font color="#2020cf">! 10.0.0.2</font> |
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<b>type(<font color="#ff003f">"dec"</font>)</b> |
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<b>subtype(<font color="#ff003f">"3max"</font>)</b> |
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<b>disk(<font color="#ff003f">"nbsd_pmax.img"</font>)</b> |
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<b>)</b> |
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</pre></td><td width="20"> </td></tr></table> |
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<p>This example creates a network using the default settings (10.0.0.0/8), |
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but it also uses the direct-access networking mode to allow the network |
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to be connected to other emulator instances. <tt>local_port(15000)</tt> |
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means that anything coming in to UDP port 15000 on the host is added to |
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the network. All ethernet packets on the network are also sent out to all |
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other connected machines (those added with <tt>add_remote()</tt>). |
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<p>As you can see in the example, this is a configuration file for |
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netbooting a NetBSD/sgimips diskless machine, with a NetBSD/pmax machine |
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acting as the nfs server. Note that the nfs server has ports 15000 and |
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15001 reversed, compared to the client! |
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<p>"<tt>localhost</tt>" can be changed to the Internet hostname of a |
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remote machine, to run the simulation across a physical network. |
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<p><font color="#ff0000"><b>NOTE:</b> There is no error checking or |
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security checking of any kind. All UDP packets arriving at the input port |
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are added to the emulated ethernet. This is not very good of course; use |
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this feature at your own risk.</font> |
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<p><br> |
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<a name="direct_example_1"></a> |
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<h3>Direct-access example 1: udp_snoop:</h3> |
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The most basic example of how the simple direct-access system works is a small |
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program in the <tt>experiments/</tt> directory, <tt>udp_snoop</tt>, which simply |
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dumps incoming UDP packets to the terminal, in hex and ASCII. |
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<p>The easiest way to test the example is to download a <a href="ftp://ftp.netbsd.org/pub/NetBSD/NetBSD-3.1/pmax/binary/kernel/netbsd-INSTALL.gz"> |
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NetBSD/pmax INSTALL kernel</a>, and start the emulator with a configuration file |
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looking something like this: |
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<pre> |
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net( |
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add_remote("localhost:12300") |
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) |
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machine( |
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subtype(3max) |
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load("netbsd-INSTALL.gz") |
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) |
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</pre> |
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<p>In addition to the machine section, you can see that there is also a |
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<tt>net()</tt> section. It defaults to emulating a 10.0.0.0/8 IPv4 NATed |
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network, but there is also an additional "raw output", to UDP port 12300. |
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<p>Now, do the following: |
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<ul> |
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<li>Start the emulator with the configuration file, i.e. |
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<tt><b>gxemul @testconfig</b></tt>. |
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<li>Start <tt><b>udp_snoop 12300</b></tt> in another terminal. |
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<li>Inside emulated NetBSD/pmax, type <tt><b>ifconfig le0 10.0.0.1</b></tt>. |
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</ul> |
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<p>This should be enough to see broadcast messages from the guest OS which |
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are not directed to the gateway. It might look like this: |
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<pre> |
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$ ./udp_snoop 12300 |
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ff ff ff ff ff ff 10 20 30 00 00 10 08 06 00 01 ....... 0....... |
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08 00 06 04 00 01 10 20 30 00 00 10 0a 00 00 02 ....... 0....... |
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00 00 00 00 00 00 0a 00 00 02 00 00 00 00 00 00 ................ |
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00 00 00 00 00 00 00 00 00 00 00 00 ............ |
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33 33 ff 00 00 10 10 20 30 00 00 10 86 dd 60 00 33..... 0.....`. |
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00 00 00 20 00 01 00 00 00 00 00 00 00 00 00 00 ... ............ |
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00 00 00 00 00 00 ff 02 00 00 00 00 00 00 00 00 ................ |
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00 01 ff 00 00 10 3a 00 01 00 05 02 00 00 83 00 ......:......... |
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80 83 00 00 00 00 ff 02 00 00 00 00 00 00 00 00 ................ |
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00 01 ff 00 00 10 ...... |
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... |
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</pre> |
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