33 lines
1.3 KiB
Markdown
33 lines
1.3 KiB
Markdown
token ring hacks
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This repository contains some random hacks around Token Ring networks,
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developed in the context of retronetworking activities long after Token
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Ring became obsolete
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tr-bridge
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This is a small program that opens AF_PACKET sockets on an ethernet and
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a token ring net-device. This means you need to use a Linux kernel <= 3.5
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as token ring support was removed at that point.
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The program then bridges 802.2 LLC packets (such as those used in IBM SNA)
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between the two interfaces, performing the required bit-swapping of MAC
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addresses.
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There are two modes of operation: with and without MAC address tables.
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The first mode will bridge all frames, while the second will only selectively
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bridge frames for certain destination MAC addresses.
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This program has shown to work in principle, but there is one known problem:
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As it operates in promiscuous mode on the TR side, it does not set the 'C'
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flag in the token, meaning that it looks to the sender as if the frame was not
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properly received (copied) by the destination mac address. This may cause
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unnecessary retransmissions of frames on TR.
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As the setting of this bit is done inside the network device hardware/firmware,
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it is currently not known how (if any) work-around to that problem is possible.
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