jcs.org
AppleTalk (EtherTalk) proxy
README: add
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LICENSE
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LICENSE
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Copyright (c) 2026 joshua stein <jcs@jcs.org>
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Permission to use, copy, modify, and distribute this software for any
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purpose with or without fee is hereby granted, provided that the above
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copyright notice and this permission notice appear in all copies.
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THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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# atalk-proxy
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`atalk-proxy` listens for AppleTalk DDP (Datagram Delivery Protocol) and
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AARP (AppleTalk Address Resolution Protocol) traffic on two ethernet interfaces
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and proxies packets between them.
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There are other solutions for this such as
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[multitalk](https://github.com/sfiera/multitalk)
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but this one has a few features I needed:
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- It does not require kernel or libpcap support for AppleTalk, as is the
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situation on OpenBSD. Packets are found by looking for specific bytes in the
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header.
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- It drops privileges after opening listening sockets using
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[`pledge`](https://man.openbsd.org/pledge).
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- Bare AARP packets that appear on the wire without a Logical-Link Control
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header are given an LLC encapsulation before proxying.
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- AARP replies that are sent out from the local side (`-t`) are inspected and
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the MAC address of the sender is replaced with the MAC of the egress (`-e`)
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interface.
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This works as a
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"[proxy ARP](https://en.wikipedia.org/wiki/Proxy_ARP)"
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solution so other network devices know to send traffic to the device running
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the proxy to reach devices on the proxy's other interface, which is likely
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needed on Wi-Fi networks.
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## Installation
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$ git clone https://github.com/jcs/atalk-proxy
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$ cd atalk-proxy
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$ make
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`atalk-proxy` was written on OpenBSD and has only been tested there.
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## Usage
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When using an emulated Macintosh Plus in
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[pce](https://github.com/jcs/pce)
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on my laptop, configured with an emulated DaynaPort SCSI ethernet device, and
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configured to use EtherTalk for AppleTalk traffic, it sends packets out through
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a
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[`tap`](https://man.openbsd.org/tap)
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interface on my laptop.
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I then run `atalk-proxy` to proxy traffic between that `tap0` interface and my
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laptop's wireless `iwx0` interface.
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That usage for me looks like:
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$ doas ./atalk-proxy -e iwx0 -t tap0
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This enables the emulated device to communicate with other devices on my
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network using AppleTalk.
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The `-d` flag can be used to print debugging information where each forwarded
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packet is described.
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$ doas ./atalk-proxy -d -e iwx0 -t tap0
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[12:47:35.599] [iwx0] listening on egress using outbound MAC 00:d4:9e:x:x:x
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[12:47:35.599] [tap0] listening on tap
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[12:47:45.386] [tap0] [ 50] AARP: is there a 65512.1? [-> iwx0]
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[12:47:45.741] [tap0] [ 50] AARP: is there a 65512.1? [-> iwx0]
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[12:47:46.072] [tap0] [ 50] AARP: is there a 65512.1? [-> iwx0]
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[12:47:46.402] [tap0] [ 50] AARP: is there a 65512.1? [-> iwx0]
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[12:47:46.734] [tap0] [ 50] AARP: is there a 65512.1? [-> iwx0]
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[12:47:47.063] [tap0] [ 50] AARP: is there a 65512.1? [-> iwx0]
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[12:47:47.420] [tap0] [ 50] AARP: is there a 65512.1? [-> iwx0]
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[12:47:47.735] [tap0] [ 50] AARP: is there a 65512.1? [-> iwx0]
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[12:47:48.067] [tap0] [ 50] AARP: is there a 65512.1? [-> iwx0]
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[12:47:48.396] [tap0] [ 50] AARP: is there a 65512.1? [-> iwx0]
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[12:47:48.750] [tap0] [ 42] ZIP: GetNetInfo [-> iwx0]
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[12:47:49.566] [tap0] [ 42] ZIP: GetNetInfo [-> iwx0]
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[12:47:50.404] [tap0] [ 42] ZIP: GetNetInfo [-> iwx0]
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[12:47:51.270] [tap0] [ 67] NBP: lookup: "nanomac:Macintosh Plus@*" [-> iwx0]
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[12:47:52.324] [tap0] [ 67] NBP: lookup: "nanomac:Macintosh Plus@*" [-> iwx0]
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[12:47:53.231] [tap0] [ 67] NBP: lookup: "nanomac:Macintosh Plus@*" [-> iwx0]
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[12:47:57.418] [tap0] [ 56] NBP: lookup: "=:AFPServer@*" [-> iwx0]
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[12:47:57.580] [iwx0] [ 42] AARP: who has 57344.0? tell 256.12 [-> tap0]
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[12:47:57.610] [tap0] [ 50] AARP: 65512.12 is at 00:80:19:c0:c0:c0: replacing MAC in outbound AARP reply [-> iwx0]
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[12:47:57.612] [iwx0] [ 57] NBP: reply[1]: "fs:AFPServer@*" [-> tap0]
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[12:47:58.593] [tap0] [621] echo from 65512.1 to 65280.224 [-> iwx0]
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[12:47:58.596] [iwx0] [621] echo from 65280.224 to 65512.1 [-> tap0]
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[12:47:58.622] [tap0] [ 43] transaction protocol [-> iwx0]
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[12:47:58.628] [iwx0] [470] transaction protocol [-> tap0]
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[12:47:59.134] [tap0] [ 56] NBP: lookup: "=:AFPServer@*" [-> iwx0]
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[12:47:59.443] [iwx0] [ 57] NBP: reply[1]: "fs:AFPServer@*" [-> tap0]
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[12:48:00.337] [tap0] [ 43] transaction protocol [-> iwx0]