From cb5c04cdf3388377a00600385a258f12fe0fdcf8 Mon Sep 17 00:00:00 2001 From: Harald Welte Date: Thu, 14 Apr 2022 14:44:21 +0200 Subject: [PATCH] Add README.md --- README.md | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) create mode 100644 README.md diff --git a/README.md b/README.md new file mode 100644 index 0000000..df33a7c --- /dev/null +++ b/README.md @@ -0,0 +1,32 @@ +token ring hacks +================ + +This repository contains some random hacks around Token Ring networks, +developed in the context of retronetworking activities long after Token +Ring became obsolete + + +tr-bridge +--------- + +This is a small program that opens AF_PACKET sockets on an ethernet and +a token ring net-device. This means you need to use a Linux kernel <= 3.5 +as token ring support was removed at that point. + +The program then bridges 802.2 LLC packets (such as those used in IBM SNA) +between the two interfaces, performing the required bit-swapping of MAC +addresses. + +There are two modes of operation: with and without MAC address tables. + +The first mode will bridge all frames, while the second will only selectively +bridge frames for certain destination MAC addresses. + +This program has shown to work in principle, but there is one known problem: +As it operates in promiscuous mode on the TR side, it does not set the 'C' +flag in the token, meaning that it looks to the sender as if the frame was not +properly received (copied) by the destination mac address. This may cause +unnecessary retransmissions of frames on TR. + +As the setting of this bit is done inside the network device hardware/firmware, +it is currently not known how (if any) work-around to that problem is possible.