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BRIDGE-HOWTO.md

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ipxbox by default just acts as a forwarding server between DOSbox clients, but it can be configured to bridge to a real network. What this means is that any clients connected to the server will also be connected to that network - similar to a VPN (unlike a VPN, it's not granting complete access to your entire network, only to things that use the IPX protocol, and nowadays few things do). If you have retro computers you can use this as a method to play online with other people, by having them connect to your ipxbox server.

First, a word of warning: DOSBox's IPX protocol is completely insecure. There's no encryption or authentication supported. For this reason, by default ipxbox blocks the IPX sockets associated with Windows file sharing. There's not a lot of damage you can do with the IPX protocol nowadays but there's still the possibility that if you use this on a public server, you might be exposing something on your network that you don't intend to.

There are two ways to set things up: ipxbox can either create a TAP device (use --enable_tap) or use libpcap to connect to a real Ethernet device. If you don't know what this means, you'll want to use the libpcap approach.

Find out which Ethernet interface (network card) you want to use by using the Linux ifconfig command. Usually the interface will be named something like eth0 but it can vary sometimes.

Programs don't usually have the permission to do raw network access. On Linux you can grant it to the ipxbox binary with the following command:

sudo setcap cap_net_raw,cap_net_admin=eip ./ipxbox

On other systems (BSD, etc.) only the root user can access raw sockets.

Next run ipxbox with the --pcap_device argument, eg.

./ipxbox --port=10000 --pcap_device=eth0

If working correctly, clients connecting to the server will now be bridged to eth0. You can test this using tcpdump to listen for IPX packets and checking if you see any when a client is connected.

$ sudo tcpdump -nli eth0 ipx
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
05:08:38.891724 IPX 00000000.02:cf:0d:86:54:e5.0002 > 00000000.02:ff:ff:ff:00:00.0002: ipx-#2 0
05:08:43.886672 IPX 00000000.02:cf:0d:86:54:e5.0002 > 00000000.02:ff:ff:ff:00:00.0002: ipx-#2 0
05:08:47.890883 IPX 00000000.02:cf:0d:86:54:e5.4002 > 00000000.ff:ff:ff:ff:ff:ff.6590: ipx-#6590 16
05:08:48.529183 IPX 00000000.02:cf:0d:86:54:e5.4002 > 00000000.ff:ff:ff:ff:ff:ff.6590: ipx-#6590 16
05:08:48.888311 IPX 00000000.02:cf:0d:86:54:e5.0002 > 00000000.02:ff:ff:ff:00:00.0002: ipx-#2 0

Configuring frame type

After following the above instructions you might find problems getting a retro computer to talk to DOSBox clients. The usual symptom will be that DOSBox clients will be able to see network traffic from the retro machine but not vice versa. This is most likely caused by a mismatch in frame type configuration.

Put simply, when IPX packets are transmitted on a LAN there are four different ways that they can be represented. It is important that all machines on the network are using the same setting (or to use a metaphor, they must all "talk the same language"). Different operating systems and network stacks have different defaults, and the default can even vary between versions. If the machines aren't talking to each other, this should be the first thing to check.

ipxbox

ipxbox itself by default uses IEEE 802.2 LLC framing, but the framing format can be changed by using the --ethernet_framing command line flag. For example:

./ipxbox --port=10000 --pcap_device=eth0 --ethernet_framing=eth-ii
--ethernet_framing value Description Notes
802.2 IEEE 802.3 with 802.2 LLC header ipxbox default, default for Novell Netware from v4.10 onwards
802.3raw Novell raw IEEE 802.3 Older Novell Netware default until Netware v4.10
snap IEEE 802.3 with 802.2 LLC and SNAP headers
eth-ii Ethernet II Most common framing format on modern LANs

Novell stack

The Novell stack is common to use under DOS with drivers named LSL.COM and IPXODI.COM. Framing is configured by editing the NET.CFG configuration file. Look for the line named FRAME, eg.

Link Driver NE2000
    INT 5
    PORT 340
    FRAME Ethernet_II

The following table shows the valid values for the FRAME field:

ipxbox name Name used in NET.CFG Description
802.2 Ethernet_802.2 802.3 with 802.2 LLC header; later Netware default (v4.10 onwards)
802.3raw Ethernet_802.3 Novell raw IEEE 802.3, older Netware default
snap Ethernet_SNAP 802.3 with 802.2 LLC and SNAP headers
eth-ii Ethernet_II Ethernet II

Packet driver IPX

If you're using packet drivers under DOS, you typically need to specify command line arguments to the packet driver on startup to configure the framing type. Check the help text or documentation for your packet driver to see what options exist. You may also find that your driver displays some information on startup that helps in debugging.

Windows 9x

To configure framing under Windows 9x, go to Control Panel → Network and find the instance of "IPX/SPX-compatible Protocol" that is bound to your network card. Click "Properties", then the "Advanced" tab, and "Frame Type".

             IPX/SPX Frame Type Configuration

ipxbox name Name used in Windows 9x Description
802.2 Ethernet 802.2 802.3 with 802.2 LLC header
802.3raw Ethernet 802.3 Novell raw IEEE 802.3
eth-ii Ethernet II Ethernet II
Token Ring Do not use
Token Ring SNAP Do not use

Classic Mac OS

Macs running Classic Mac OS (not OS X) can access IPX networks by using the MacIPX system extension that was published by Novell. This was also included with some Mac games such as Doom and Hexen which included IPX support to allow them to join in games with DOS machines.

To configure framing, go to Control Panels → MacIPX. Double click "Ethernet" to open the Ethernet Access Configuration window. By default MacIPX attempts to automatically configure framing but if you encounter problems you can disable autodetection and manually specify it.

             MacIPX Frame Type Configuration

ipxbox name Name used in MacIPX Description
802.2 Ethernet 802.2 802.3 with 802.2 LLC header
802.3raw Ethernet 802.3 Novell raw IEEE 802.3
snap Ethernet 802.2 SNAP 802.3 with 802.2 LLC and SNAP headers
eth-ii Ethernet II Ethernet II

Advanced topic: TCP/IP over IPX

Much DOS software that communicates over the network (particularly using the TCP/IP protocol stack used on the Internet) uses the packet driver interface. There are packet drivers available for most network cards, providing a standard interface for sending and receiving data over the network.

Some forks of DOSbox can emulate the Novell NE2000 card, allowing such software to be used. However, vanilla DOSbox at the time of writing does not include this feature. Furthermore, it typically requires granting DOSbox special permission to be able to send and receive raw network packets. The ipxpkt.com driver is a packet driver that tunnels an Ethernet link over IPX packets, and ipxbox includes support for its protocol. This allows DOSbox users to use packet driver-based software.

First, a word of warning: the DOSBox IPX protocol is completely insecure. There's no encryption or authentication supported, and enabling this feature gives a potential backdoor into the network where the ipxbox server is running. If you don't understand the implications of this, don't enable this feature on a public-facing ipxbox server.

To use this feature:

  1. First set up an IPX bridge by following the instructions from the previous section.

  2. Read the warning in the paragraph above this list. Then add --enable_ipxpkt to the ipxbox command line. For example:

./ipxbox --port=10000 --pcap_device=eth0 --enable_ipxpkt

  1. Start a DOSbox client and connect to the server as normal. Make sure to mount a directory containing the ipxpkt.com driver.

  2. Start the packet driver as shown:

C:\>ipxpkt -i 0x60

Packet driver for IPX, version 11.3
Portions Copyright 1990, P. Kranenburg
Packet driver skeleton copyright 1988-93, Crynwr Software.
This program is freely copyable; source must be available; NO WARRANTY.
See the file COPYING.DOC for details; send FAX to +1-315-268-9201 for a copy.

This may take up to 30 seconds...
System: [345]86 processor, ISA bus, Two 8259s
Packet driver software interrupt is 0x60 (96)
My Ethernet address is 02:57:04:31:68:FA

C:\>
  1. Test the connection is working correctly by trying some software that uses the packet driver interface. The mTCP stack makes for a good first step. For example:
C:\>set mtcpcfg=c:\mtcp\mtcp.cfg
C:\>dhcp

mTCP DHCP Client by M Brutman (mbbrutman@gmail.com) (C)opyright 2008-2020
Version: Mar  7 2020

Timeout per request: 10 seconds, Retry attempts: 3
Sending DHCP requests, Press [ESC] to abort.

DHCP request sent, attempt 1: Offer received, Acknowledged

Good news everyone!

IPADDR 192.168.128.45
NETMASK 255.255.0.0
GATEWAY 192.168.60.1
NAMESERVER 8.8.8.8
LEASE_TIME 86400 seconds

Settings written to 'c:\mtcp\mtcp.cfg'

C:\>ping 8.8.8.8

mTCP Ping by M Brutman (mbbrutman@gmail.com) (C)opyright 2009-2020
Version: Mar  7 2020

ICMP Packet payload is 32 bytes.

Packet sequence number 0 received in 45.90 ms, ttl=114
Packet sequence number 1 received in 44.20 ms, ttl=114
Packet sequence number 2 received in 41.65 ms, ttl=114
Packet sequence number 3 received in 54.40 ms, ttl=114

Packets sent: 4, Replies received: 4, Replies lost: 0
Average time for a reply: 46.53 ms (not counting lost packets)