AX.25 on Linux - Revision history

KI5QKX: mw push

2026-05-02T19:48:01Z

mw push

KI5QKX: fix links

2026-05-01T18:02:46Z

fix links

← Older revision		Revision as of 18:02, 1 May 2026
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	=== Kernel discussions ===		=== Kernel discussions ===

	* [https://lore.kernel.org/netdev/20260421021824.1293976-1-kuba@kernel.org/ Jakub Kicinski’s April 21, 2026 patch proposing removal of the in-tree amateur-radio networking subsystem]		* [https://lore.kernel.org/netdev/20260421021824.1293976-1-kuba@kernel.org/ Jakub Kicinski’s April 21, 2026 patch], proposing removal of the in-tree amateur-radio networking subsystem
	* [https://lore.kernel.org/lkml/20260423235422.1541768-1-kuba@kernel.org/ Jakub Kicinski’s April 23, 2026 pull-request thread with more discussion]		* [https://lore.kernel.org/lkml/20260423235422.1541768-1-kuba@kernel.org/ Jakub Kicinski’s April 23, 2026 pull-request thread], with more discussion
	* [https://lore.kernel.org/netdev/20260424232427.792249-1-stephen@networkplumber.org/ Stephen Hemminger’s April 24, 2026 iproute2 cleanup patch noting that AX.25, ROSE, and NET/ROM have been removed upstream]		* [https://lore.kernel.org/netdev/20260424232427.792249-1-stephen@networkplumber.org/ Stephen Hemminger’s April 24, 2026 iproute2 cleanup patch], noting that AX.25, ROSE, and NET/ROM have been removed upstream
	* [https://lore.kernel.org/netdev/CAEoi9W6ZRw6aEh62Xbgkg-TW8URHbVp6dHTT9krFiTkotjTuTA@mail.gmail.com/ Dan Cross on the likely user-space direction, including TUN/TAP for IP over AX.25]		* [https://lore.kernel.org/netdev/CAEoi9W6ZRw6aEh62Xbgkg-TW8URHbVp6dHTT9krFiTkotjTuTA@mail.gmail.com/ Dan Cross on the likely user-space direction], including TUN/TAP for IP over AX.25

	=== Independent coverage ===		=== Independent coverage ===

	* [https://lwn.net/Articles/1068928/ LWN coverage from April 22, 2026 summarizing the broader kernel code-removal effort]		* [https://lwn.net/Articles/1068928/ LWN coverage from April 22, 2026], summarizing the broader kernel code-removal effort
	* [https://www.phoronix.com/news/Linux-7.1-PR-Remove-Old-Net Phoronix coverage from April 24, 2026 on the pull request removing legacy networking code, including AX.25]		* [https://www.phoronix.com/news/Linux-7.1-PR-Remove-Old-Net Phoronix coverage from April 24, 2026], on the pull request removing legacy networking code, including AX.25

	=== Repositories and source trees ===		=== Repositories and source trees ===
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	=== Older HOWTOs ===		=== Older HOWTOs ===

	* [http://www.tldp.org/HOWTO/AX25-HOWTO/ Jeff ~~Tranter’s~~ Linux AX.25 HOWTO], useful mainly as historical background now		* [http://www.tldp.org/HOWTO/AX25-HOWTO/ Jeff Tranter VE3ICH’s 2001 Linux AX.25 HOWTO], useful mainly as historical background now

	=== Protocol references ===		=== Protocol references ===

KI5QKX: fix heading typo

2026-05-01T18:00:35Z

fix heading typo

← Older revision		Revision as of 18:00, 1 May 2026
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	== Further reading ==		== Further reading ==

	=== ARDC groups.io discussions ==		=== ARDC groups.io discussions ===

	* [https://ardc.groups.io/g/community/topic/119004386 Boudewijn VE3TOK’s thread and discussion about paths forward]		* [https://ardc.groups.io/g/community/topic/119004386 Boudewijn VE3TOK’s thread and discussion about paths forward]

KI5QKX: add some 44net mailing list links

2026-05-01T18:00:00Z

add some 44net mailing list links

← Older revision		Revision as of 18:00, 1 May 2026
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	== Further reading ==		== Further reading ==

	=== ~~Protocol references =~~==		=== ARDC groups.io discussions ==

	* [https://~~files~~.~~tapr~~.~~org~~/~~tech_docs~~/~~AX25~~/~~AX25.2.2.1997.pdf AX.25 Link Access Protocol for Amateur Packet Radio, Version 2.2]~~		* [https://ardc.groups.io/g/community/topic/119004386 Boudewijn VE3TOK’s thread and discussion about paths forward]
	* [https:/~~/ax25.net/ AX.25 Layer 2~~]		* [https://ardc.groups.io/g/community/topic/119004386 Bernard F6BVP’s retrospective and thoughts on the change]
	* [https://~~www~~.~~on7lds~~.~~net/42~~/~~sites~~/~~default~~/~~files~~/~~AGWPEAPI.HTM AGWPE TCP/IP API reference]~~
	* [https://github.com/wb2osz/direwolf/blob/master/doc/AX25_plus_FEC_equals_FX25.pdf Dire Wolf’s AX.25 framing and ~~FEC documentation~~]

	=== Kernel discussions ===		=== Kernel discussions ===
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	* [http://www.tldp.org/HOWTO/AX25-HOWTO/ Jeff Tranter’s Linux AX.25 HOWTO], useful mainly as historical background now		* [http://www.tldp.org/HOWTO/AX25-HOWTO/ Jeff Tranter’s Linux AX.25 HOWTO], useful mainly as historical background now

			=== Protocol references ===

			* [https://files.tapr.org/tech_docs/AX25/AX25.2.2.1997.pdf AX.25 Link Access Protocol for Amateur Packet Radio, Version 2.2]
			* [https://ax25.net/ AX.25 Layer 2]
			* [https://www.on7lds.net/42/sites/default/files/AGWPEAPI.HTM AGWPE TCP/IP API reference]
			* [https://github.com/wb2osz/direwolf/blob/master/doc/AX25_plus_FEC_equals_FX25.pdf Dire Wolf’s AX.25 framing and FEC documentation]

	== Related pages ==		== Related pages ==

KI5QKX: add links to other coverage and mailing list thread

2026-05-01T17:40:00Z

add links to other coverage and mailing list thread

← Older revision		Revision as of 17:40, 1 May 2026
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	=== Kernel discussions ===		=== Kernel discussions ===

	* [https://lore.kernel.org/netdev/20260421021824.1293976-1-kuba@kernel.org/ Jakub Kicinski’s April 20, 2026 patch proposing removal of the in-tree amateur-radio networking subsystem]		* [https://lore.kernel.org/netdev/20260421021824.1293976-1-kuba@kernel.org/ Jakub Kicinski’s April 21, 2026 patch proposing removal of the in-tree amateur-radio networking subsystem]
			* [https://lore.kernel.org/lkml/20260423235422.1541768-1-kuba@kernel.org/ Jakub Kicinski’s April 23, 2026 pull-request thread with more discussion]
	* [https://lore.kernel.org/netdev/20260424232427.792249-1-stephen@networkplumber.org/ Stephen Hemminger’s April 24, 2026 iproute2 cleanup patch noting that AX.25, ROSE, and NET/ROM have been removed upstream]		* [https://lore.kernel.org/netdev/20260424232427.792249-1-stephen@networkplumber.org/ Stephen Hemminger’s April 24, 2026 iproute2 cleanup patch noting that AX.25, ROSE, and NET/ROM have been removed upstream]
	* [https://lore.kernel.org/netdev/CAEoi9W6ZRw6aEh62Xbgkg-TW8URHbVp6dHTT9krFiTkotjTuTA@mail.gmail.com/ Dan Cross on the likely user-space direction, including TUN/TAP for IP over AX.25]		* [https://lore.kernel.org/netdev/CAEoi9W6ZRw6aEh62Xbgkg-TW8URHbVp6dHTT9krFiTkotjTuTA@mail.gmail.com/ Dan Cross on the likely user-space direction, including TUN/TAP for IP over AX.25]
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	* [https://lwn.net/Articles/1068928/ LWN coverage from April 22, 2026 summarizing the broader kernel code-removal effort]		* [https://lwn.net/Articles/1068928/ LWN coverage from April 22, 2026 summarizing the broader kernel code-removal effort]
			* [https://www.phoronix.com/news/Linux-7.1-PR-Remove-Old-Net Phoronix coverage from April 24, 2026 on the pull request removing legacy networking code, including AX.25]

	=== Repositories and source trees ===		=== Repositories and source trees ===

KI5QKX: Add ax.25/fx.25 paper

2026-05-01T17:34:56Z

Add ax.25/fx.25 paper

← Older revision		Revision as of 17:34, 1 May 2026
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	* [https://ax25.net/ AX.25 Layer 2]		* [https://ax25.net/ AX.25 Layer 2]
	* [https://www.on7lds.net/42/sites/default/files/AGWPEAPI.HTM AGWPE TCP/IP API reference]		* [https://www.on7lds.net/42/sites/default/files/AGWPEAPI.HTM AGWPE TCP/IP API reference]
			* [https://github.com/wb2osz/direwolf/blob/master/doc/AX25_plus_FEC_equals_FX25.pdf Dire Wolf’s AX.25 framing and FEC documentation]

	=== Kernel discussions ===		=== Kernel discussions ===

KI5QKX: add some further reading

2026-05-01T17:30:05Z

add some further reading

← Older revision		Revision as of 17:30, 1 May 2026
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	== Further reading ==		== Further reading ==

			=== Protocol references ===

			* [https://files.tapr.org/tech_docs/AX25/AX25.2.2.1997.pdf AX.25 Link Access Protocol for Amateur Packet Radio, Version 2.2]
			* [https://ax25.net/ AX.25 Layer 2]
			* [https://www.on7lds.net/42/sites/default/files/AGWPEAPI.HTM AGWPE TCP/IP API reference]

	=== Kernel discussions ===		=== Kernel discussions ===

KI5QKX: Add tncattach discussion

2026-05-01T17:15:50Z

Add tncattach discussion

← Older revision		Revision as of 17:15, 1 May 2026
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	== Timeline ==		== Timeline ==

	This change happened in “upstream Linux” first, referring to the mainline Linux kernel project. Distributions like Debian, Ubuntu, Fedora~~, and others~~ decide for themselves when to ship newer kernels, and long-term-support distributions may stay on older kernel lines for quite a while.		This change happened in “upstream Linux” first, referring to the mainline Linux kernel project. Distributions like Debian, Ubuntu, and Fedora decide for themselves when to ship newer kernels, and long-term-support distributions may stay on older kernel lines for quite a while.

	That means this probably is not hitting most existing stations tomorrow. In many cases, you will keep working until your distribution moves you to a kernel that no longer includes the in-tree AX.25 code, whether that happens in a major distribution upgrade or in a later kernel update.		That means this probably is not hitting most existing stations tomorrow. In many cases, you will keep working until your distribution moves you to a kernel that no longer includes the in-tree AX.25 code, whether that happens in a major distribution upgrade or in a later kernel update.
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	An understanding of the difference between in-kernel and user-space implementations of AX.25 is helpful when considering the impact of the kernel code removal and the options for moving forward.		An understanding of the difference between in-kernel and user-space implementations of AX.25 is helpful when considering the impact of the kernel code removal and the options for moving forward.

	The in-kernel code worked like a device driver. The <code>/etc/axports</code> file named and described AX.25 ports for the Linux AX.25 tools, while utilities like <code>kissattach</code> connected a KISS TNC or pseudo-tty to the kernel stack and created an <code>ax</code> network interface. You could assign that interface an IP address, network applications could interact with it like any other network interface, and code in the kernel would handle AX.25 framing and interacting with the TNC using [https://www.ka9q.net/papers/kiss.html the KISS protocol]. If your main use of <code>kissattach</code> was simply to turn a KISS TNC into a Linux network device for IP networking, a separate user-space project called [https://github.com/markqvist/tncattach tncattach] may also be worth a look.		The in-kernel code worked like a device driver. The <code>/etc/axports</code> file named and described AX.25 ports for the Linux AX.25 tools, while utilities like <code>kissattach</code> connected a KISS TNC or pseudo-tty to the kernel stack and created an <code>ax</code> network interface. You could assign that interface an IP address, network applications could interact with it like any other network interface, and code in the kernel would handle AX.25 framing and interacting with the TNC using [https://www.ka9q.net/papers/kiss.html the KISS protocol].

	A user-space implementation, on the other hand, implements AX.25 in an executable binary that you run separately, not as part of the kernel. It might interface with an external hardware TNC over a serial port, it might work with a software soundmodem, or it might be an all-in-one soundmodem and software TNC combined. You configure it to talk to your radio by various means, and it in turn provides a KISS, AGWPE, TCP, or other interface for other applications to use. This is less like a device driver and more like a server daemon that client applications can connect to.		A user-space implementation, on the other hand, implements AX.25 in an executable binary that you run separately, not as part of the kernel. It might interface with an external hardware TNC over a serial port, it might work with a software soundmodem, or it might be an all-in-one soundmodem and software TNC combined. You configure it to talk to your radio by various means, and it in turn provides a KISS, AGWPE, TCP, or other interface for other applications to use. This is less like a device driver and more like a server daemon that client applications can connect to.
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	If your goal is specifically IP over AX.25, the range of options has narrowed.		If your goal is specifically IP over AX.25, the range of options has narrowed.

	The [https://lore.kernel.org/netdev/20260421021824.1293976-1-kuba@kernel.org/ upstream discussion] explicitly points out that IP over AX.25 can, in principle, be handled from user space via TUN/TAP integration rather than by requiring the historic kernel implementation.		The [https://lore.kernel.org/netdev/20260421021824.1293976-1-kuba@kernel.org/ upstream discussion] explicitly points out that IP over AX.25 can, in principle, be handled from user space, as via TUN/TAP integration, rather than by requiring the historic kernel implementation.

	One current project worth investigating is [https://github.com/markqvist/tncattach tncattach], a separate user-space tool that creates a Linux network interface from a KISS-compatible TNC without relying on the old kernel AX.25 stack. It is aimed at IP or Ethernet-style networking over a TNC rather than at preserving the historic Linux AX.25 interface model, so it should be understood as a different approach rather than a drop-in replacement for <code>kissattach</code>.

	That does not mean there is one complete drop-in replacement ready for every old Linux AX.25 workflow today. It does suggest a long-term architectural direction:		That does not mean there is one complete drop-in replacement ready for every old Linux AX.25 workflow today. It does suggest a long-term architectural direction:
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	For now, end users may need to stay on an older kernel until a user-space solution emerges. Interested developers might look into this as an area for contributions to new or existing projects.		For now, end users may need to stay on an older kernel until a user-space solution emerges. Interested developers might look into this as an area for contributions to new or existing projects.

			One current project that might be relevant for IP over amateur radio projects is [https://github.com/markqvist/tncattach tncattach], a separate user-space tool that creates a Linux network interface from a KISS-compatible TNC without relying on the old kernel AX.25 stack.

			It is not a user-space replacement for the old Linux AX.25 stack, and it should not be understood as preserving the historic Linux AX.25 interface model. It is aimed instead at IP or Ethernet-style networking over a TNC. If your main use of <code>kissattach</code> was simply to turn a KISS TNC into a Linux network device for IP networking, then <code>tncattach</code> may be worth a look.

			It may also be a useful reference point for future development. Even if it does not solve every AX.25-specific use case by itself, it shows one way to bridge a KISS-compatible TNC to a Linux network device without the old kernel stack, and that approach could potentially be extended further or incorporated into other projects.

	== Further reading ==		== Further reading ==

KI5QKX: Add tncattach discussion

2026-05-01T16:59:29Z

Add tncattach discussion

← Older revision		Revision as of 16:59, 1 May 2026
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	* If your setup uses KISS or AGWPE to talk to a software TNC, hardware TNC, or packet-radio application, you are probably not affected by the kernel removal.		* If your setup uses KISS or AGWPE to talk to a software TNC, hardware TNC, or packet-radio application, you are probably not affected by the kernel removal.
	* If your setup uses Linux AX.25 interfaces like <code>ax0</code>, <code>kissattach</code>, <code>/etc/axports</code>, or <code>ax25d</code>, it will not keep working unchanged on newer kernels.		* If your setup uses Linux AX.25 interfaces like <code>ax0</code>, <code>kissattach</code>, <code>/etc/axports</code>, or <code>ax25d</code>, it will not keep working unchanged on newer kernels.
	* Nothing breaks immediately just because the upstream kernel changed. Existing systems keep working until you update them~~, replace them, or rebuild them around newer kernels~~.		* Nothing breaks immediately just because the upstream kernel changed. Existing systems keep working until you update them to a kernel released after the change.

	For years, Linux included an in-kernel implementation of AX.25, Net/ROM, and ROSE. This provided network interfaces for connected-mode packet, and user-space applications could rely on those interfaces for their AX.25 needs. This page explains what changed, how to tell whether your station depends on that older model, and what practical options exist now.		This page explains what changed, how to tell whether your station depends on that older model, and what practical options exist now.

	== What is changing ==		== What is changing ==
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	That means this probably is not hitting most existing stations tomorrow. In many cases, you will keep working until your distribution moves you to a kernel that no longer includes the in-tree AX.25 code, whether that happens in a major distribution upgrade or in a later kernel update.		That means this probably is not hitting most existing stations tomorrow. In many cases, you will keep working until your distribution moves you to a kernel that no longer includes the in-tree AX.25 code, whether that happens in a major distribution upgrade or in a later kernel update.

	The practical takeaway is ~~simple~~: you likely have some time to plan, but you may want to pay attention to updates that include newer kernels.		The practical takeaway is: you likely have some time to plan, but you may want to pay attention to updates that include newer kernels.

	== Am I affected? ==		== Am I affected? ==

	~~A good first check is whether~~ your ~~station~~ uses the ~~old~~ Linux kernel AX.25 model ~~or a user-space TNC/application model~~.		Yes, if your setup uses the Linux kernel AX.25 model. Probably not, if you use software that talks to devices directly.

	You are probably using the kernel AX.25 stack if:		You are probably using the kernel AX.25 stack if:
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	An understanding of the difference between in-kernel and user-space implementations of AX.25 is helpful when considering the impact of the kernel code removal and the options for moving forward.		An understanding of the difference between in-kernel and user-space implementations of AX.25 is helpful when considering the impact of the kernel code removal and the options for moving forward.

	The in-kernel code worked like a device driver. The <code>/etc/axports</code> file named and described AX.25 ports for the Linux AX.25 tools, while utilities like <code>kissattach</code> connected a KISS TNC or pseudo-tty to the kernel stack and created an <code>ax</code> network interface. You could assign that interface an IP address, network applications could interact with it like any other network interface, and code in the kernel would handle AX.25 framing and interacting with the TNC using [https://www.ka9q.net/papers/kiss.html the KISS protocol].		The in-kernel code worked like a device driver. The <code>/etc/axports</code> file named and described AX.25 ports for the Linux AX.25 tools, while utilities like <code>kissattach</code> connected a KISS TNC or pseudo-tty to the kernel stack and created an <code>ax</code> network interface. You could assign that interface an IP address, network applications could interact with it like any other network interface, and code in the kernel would handle AX.25 framing and interacting with the TNC using [https://www.ka9q.net/papers/kiss.html the KISS protocol]. If your main use of <code>kissattach</code> was simply to turn a KISS TNC into a Linux network device for IP networking, a separate user-space project called [https://github.com/markqvist/tncattach tncattach] may also be worth a look.

	A user-space implementation, on the other hand, implements AX.25 in an executable binary that you run separately, not as part of the kernel. It might interface with an external hardware TNC over a serial port, it might work with a software soundmodem, or it might be an all-in-one soundmodem and software TNC combined. You configure it to talk to your radio by various means, and it in turn provides a KISS, AGWPE, TCP, or other interface for other applications to use. This is less like a device driver and more like a server daemon that client applications can connect to.		A user-space implementation, on the other hand, implements AX.25 in an executable binary that you run separately, not as part of the kernel. It might interface with an external hardware TNC over a serial port, it might work with a software soundmodem, or it might be an all-in-one soundmodem and software TNC combined. You configure it to talk to your radio by various means, and it in turn provides a KISS, AGWPE, TCP, or other interface for other applications to use. This is less like a device driver and more like a server daemon that client applications can connect to.
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	\| Modem/TNC functions, KISS, AGWPE		\| Modem/TNC functions, KISS, AGWPE
	\| Another example of a user-space software-TNC design exposing standard host interfaces		\| Another example of a user-space software-TNC design exposing standard host interfaces
			\|-
			\| tncattach
			\| [https://github.com/markqvist/tncattach GitHub]
			\| KISS-based Linux network-device integration for IP and Ethernet-style networking
			\| Reference for bridging a KISS TNC to a Linux network device without the old AX.25 kernel stack
	\|-		\|-
	\| Pat		\| Pat
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	The [https://lore.kernel.org/netdev/20260421021824.1293976-1-kuba@kernel.org/ upstream discussion] explicitly points out that IP over AX.25 can, in principle, be handled from user space via TUN/TAP integration rather than by requiring the historic kernel implementation.		The [https://lore.kernel.org/netdev/20260421021824.1293976-1-kuba@kernel.org/ upstream discussion] explicitly points out that IP over AX.25 can, in principle, be handled from user space via TUN/TAP integration rather than by requiring the historic kernel implementation.

			One current project worth investigating is [https://github.com/markqvist/tncattach tncattach], a separate user-space tool that creates a Linux network interface from a KISS-compatible TNC without relying on the old kernel AX.25 stack. It is aimed at IP or Ethernet-style networking over a TNC rather than at preserving the historic Linux AX.25 interface model, so it should be understood as a different approach rather than a drop-in replacement for <code>kissattach</code>.

	That does not mean there is one complete drop-in replacement ready for every old Linux AX.25 workflow today. It does suggest a long-term architectural direction:		That does not mean there is one complete drop-in replacement ready for every old Linux AX.25 workflow today. It does suggest a long-term architectural direction:

KI5QKX: Updates for clarity and accuracy

2026-05-01T15:58:46Z

Updates for clarity and accuracy

Show changes