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1 dpavlin 32 <html><head><title>Gavare's eXperimental Emulator:&nbsp;&nbsp;&nbsp;Networking</title>
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7     <b>Gavare's eXperimental Emulator:</b></font><br>
8     <font color="#000000" size="6"><b>Networking</b>
9     </font></td></tr></table></td></tr></table><p>
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41    
42    
43     <a href="./">Back to the index</a>
44    
45     <p><br>
46     <h2>Networking</h2>
47    
48     <p>
49     <ul>
50     <li><a href="#intro">Introduction</a>
51     <li><a href="#multihost">Network across multiple hosts</a>
52     <li><a href="#direct_example_1">Direct-access example 1: udp_snoop</a>
53     </ul>
54    
55    
56    
57    
58    
59    
60    
61     <p><br>
62     <a name="intro"></a>
63     <h3>Introduction:</h3>
64    
65     GXemul's current networking layer supports two modes:
66    
67     <p><ol>
68     <li>A NAT-like layer, which allows guest OSes to access the outside
69     internet world (IPv4 only, so far). When only one machine is being
70     emulated, the following default values apply to the guest OS:<pre>
71     IPv4 address: 10.0.0.1
72     Netmask: 255.0.0.0
73     Gateway / default route: 10.0.0.254
74     Nameserver: 10.0.0.254
75     </pre>To the outside world, it will seem as if the host is doing all the
76     networking, since the emulator is just a normal user process
77     on the host.
78     <p>
79     <li>A direct-access layer, allowing external tools to read/write raw
80     ethernet packages from/to the emulator.
81     </ol>
82    
83     <p><i>NOTE:</i> Both these modes have problems. The NAT-like layer is very
84     "hackish" and was only meant as a proof-of-concept, to see if networking
85     like this would work with e.g. NetBSD as a guest OS. (If you are
86     interested in the technical details, and the reasons why NAT networking is
87     implemented this way, you might want to read the <a
88     href="technical.html#net"> networking section in the technical
89     documentation</a>.) Because of the obvious limitations with the NAT
90     approach, I have also included support for direct packet access, but this
91     is not designed for security or anything like that.
92    
93     <p><font color="#ff0000">Use the networking features at your own risk.
94     </font>
95    
96    
97     <p>The emulated machine must of course have a NIC which is emulated
98     sufficiently. At the moment, the following NICs should work:
99     <ul>
100     <li><tt><b>ether</b></tt>, the "fake" experimental ethernet device
101     (documented <a href="experiments.html#expdevices_ether">here</a>)
102     <li><tt><b>le</b></tt>, Turbochannel Lance Ethernet, as used in
103     DECstation 5000/200 ("3max")
104     <li><tt><b>mec</b></tt>, the SGI O2's ethernet controller
105     <li><tt><b>dec21143</b></tt>, Digital's 21143 NIC (known as <tt>dc</tt>
106     in OpenBSD, or <tt>tlp</tt> in NetBSD)
107     </ul>
108    
109    
110    
111    
112    
113    
114    
115     <p><br>
116     <a name="multihost"></a>
117     <h3>Network across multiple hosts:</h3>
118    
119     <p>The way to emulate a network of multiple emulated machines, whether
120     they are actually running on the same physical host, or on multiple hosts,
121     is to use <a href="configfiles.html">configuration files</a>, and the
122     "direct-access" method of networking.
123    
124     <p>Although it <i>is</i> possible to have more than one machine per
125     configuration file, I strongly recommend against it. Please use one
126     configuration file for one emulated machine.
127    
128     <p>Here is a simple example:
129    
130     <p><table border="0" width="100%"><tr><td width="40">&nbsp;</td>
131     <td><pre>
132     <font color="#2020cf">! Configuration file for a
133     ! "client" machine, netbooting
134     ! of another machine.</font>
135    
136     <b>net(</b>
137     <b>local_port(15000)</b>
138     <b>add_remote(<font color="#ff003f">"localhost:15001"</font>)</b>
139     <b>)</b>
140     <b>machine(</b>
141     <b>name(<font color="#ff003f">"client machine"</font>)</b>
142     <b>serial_nr(1)</b> <font color="#2020cf">! 10.0.0.1</font>
143    
144     <b>type(<font color="#ff003f">"sgi"</font>)</b>
145     <b>subtype(<font color="#ff003f">"o2"</font>)</b>
146     <b>load(<font color="#ff003f">"netbsd-GENERIC32_IP3x.gz"</font>)</b>
147     <b>)</b>
148     </pre></td><td width="20">&nbsp;</td><td><pre>
149     <font color="#2020cf">! Configuration file for the
150     ! "server" machine.</font>
151    
152     <b>net(</b>
153     <b>local_port(15001)</b>
154     <b>add_remote(<font color="#ff003f">"localhost:15000"</font>)</b>
155     <b>)</b>
156     <b>machine(</b>
157     <b>name(<font color="#ff003f">"nfs server"</font>)</b>
158     <b>serial_nr(2)</b> <font color="#2020cf">! 10.0.0.2</font>
159    
160     <b>type(<font color="#ff003f">"dec"</font>)</b>
161     <b>subtype(<font color="#ff003f">"3max"</font>)</b>
162     <b>disk(<font color="#ff003f">"nbsd_pmax.img"</font>)</b>
163     <b>)</b>
164     </pre></td><td width="20">&nbsp;</td></tr></table>
165    
166     <p>This example creates a network using the default settings (10.0.0.0/8),
167     but it also uses the direct-access networking mode to allow the network
168     to be connected to other emulator instances. <tt>local_port(15000)</tt>
169     means that anything coming in to UDP port 15000 on the host is added to
170     the network. All ethernet packets on the network are also sent out to all
171     other connected machines (those added with <tt>add_remote()</tt>).
172    
173     <p>As you can see in the example, this is a configuration file for
174     netbooting a NetBSD/sgimips diskless machine, with a NetBSD/pmax machine
175     acting as the nfs server. Note that the nfs server has ports 15000 and
176     15001 reversed, compared to the client!
177    
178     <p>"<tt>localhost</tt>" can be changed to the Internet hostname of a
179     remote machine, to run the simulation across a physical network.
180    
181     <p><font color="#ff0000"><b>NOTE:</b> There is no error checking or
182     security checking of any kind. All UDP packets arriving at the input port
183     are added to the emulated ethernet. This is not very good of course; use
184     this feature at your own risk.</font>
185    
186    
187    
188    
189    
190     <p><br>
191     <a name="direct_example_1"></a>
192     <h3>Direct-access example 1: udp_snoop:</h3>
193    
194     The most basic example of how the simple direct-access system works is a small
195     program in the <tt>experiments/</tt> directory, <tt>udp_snoop</tt>, which simply
196     dumps incoming UDP packets to the terminal, in hex and ASCII.
197    
198     <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">
199     NetBSD/pmax INSTALL kernel</a>, and start the emulator with a configuration file
200     looking something like this:
201    
202     <pre>
203     net(
204     add_remote("localhost:12300")
205     )
206    
207     machine(
208     subtype(3max)
209     load("netbsd-INSTALL.gz")
210     )
211     </pre>
212    
213     <p>In addition to the machine section, you can see that there is also a
214     <tt>net()</tt> section. It defaults to emulating a 10.0.0.0/8 IPv4 NATed
215     network, but there is also an additional "raw output", to UDP port 12300.
216    
217     <p>Now, do the following:
218     <ul>
219     <li>Start the emulator with the configuration file, i.e.
220     <tt><b>gxemul @testconfig</b></tt>.
221     <li>Start <tt><b>udp_snoop 12300</b></tt> in another terminal.
222     <li>Inside emulated NetBSD/pmax, type <tt><b>ifconfig le0 10.0.0.1</b></tt>.
223     </ul>
224    
225     <p>This should be enough to see broadcast messages from the guest OS which
226     are not directed to the gateway. It might look like this:
227    
228     <pre>
229     $ ./udp_snoop 12300
230     ff ff ff ff ff ff 10 20 30 00 00 10 08 06 00 01 ....... 0.......
231     08 00 06 04 00 01 10 20 30 00 00 10 0a 00 00 02 ....... 0.......
232     00 00 00 00 00 00 0a 00 00 02 00 00 00 00 00 00 ................
233     00 00 00 00 00 00 00 00 00 00 00 00 ............
234    
235     33 33 ff 00 00 10 10 20 30 00 00 10 86 dd 60 00 33..... 0.....`.
236     00 00 00 20 00 01 00 00 00 00 00 00 00 00 00 00 ... ............
237     00 00 00 00 00 00 ff 02 00 00 00 00 00 00 00 00 ................
238     00 01 ff 00 00 10 3a 00 01 00 05 02 00 00 83 00 ......:.........
239     80 83 00 00 00 00 ff 02 00 00 00 00 00 00 00 00 ................
240     00 01 ff 00 00 10 ......
241     ...
242     </pre>
243    
244    
245    
246    
247     </p>
248    
249     </body>
250     </html>
251    
252    

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