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Linux X25 Stack¶
The Linux kernel has had an (experimental?) X.25 implementation for ages. Surprisingly, this is still present even in 2023.
The kernel code appears to support- X.25 over LAPB/Ethernet (DTE role; DCE requires kernel patch)
- X.25 over generic HDLC
- this would work e.g. over DAHDI_NET devices, and hence over BRI/PRI cards supported by DAHDI
- X.25 over X.21 using a FarSite FarSync card
There also apparently was an async_x25 driver for running X.25 over asynchronous serial ports, but that appears to be gone from present-day Linux.
x25-utils¶
The original code can be found at https://www.baty.hanse.de/linux-x25/
The ancient userspace utility code has been imported into a git repo at https://gitea.osmocom.org/retronetworking/x25-utils
X.25 over HDLC / DAHDI¶
roox reported in April 2023 that he sucessfully tested AF_X25 socket connections between 2 Linux machines over the hdlcX interfaces you get with DAHDI/nethdlc (Linux generic HDLC layer)
- https://pmtu.de/.dump/af_x25_sockets_server.c
- https://pmtu.de/.dump/af_x25_sockets_client.c
- https://pmtu.de/.dump/x25-hacks.tar.gz (contains the above, plus also af_packet server/client)
Example x25trace output¶
# x25trace --------------------------------------------------------------------- Port: hdlc0 X.25: LCI 001 : CALL ACCEPTED Packet Size: 07 07 Window Size: 2 2 Port: hdlc0 X.25: LCI 001 : CLEAR REQUEST - Cause DTE Originated - Diag 0 Port: hdlc0 X.25: LCI 001 : CLEAR CONFIRMATION ---------------------------------------------------------------------
Updated by laforge 3 months ago · 1 revisions