systemd/rules.d/82-net-auto-link-local.rules

# do not edit this file, it will be overwritten on update

ACTION=="remove", GOTO="net_link_local_end"
SUBSYSTEM!="net", GOTO="net_link_local_end"

# Network interfaces for which only Link-Local communication (i.e. IPv4LL, …)
# makes sense, because they almost certainy will point to another host, not an
# internet router.

# (Note: matches against VID/PID go into 82-net-auto-link-local.hwdb instead)

# Thunderbolt host-to-host connections
DRIVERS=="thunderbolt-net", ENV{ID_NET_AUTO_LINK_LOCAL_ONLY}="1"

LABEL="net_link_local_end"
hwdb,rules: mark host-to-host network devices as only requiring link local addressing This is a generalization of this logic: https://github.com/NetworkManager/NetworkManager/blob/main/data/90-nm-thunderbolt.rules It applies not just to thunderbolt, but to any kind of device, even matched by vendor/product, via hwdb. I added two entries for Prolific PC-to-PC devices (of which I have one lying around). 2023-10-30 15:53:59 +00:00			`# do not edit this file, it will be overwritten on update`

			`ACTION=="remove", GOTO="net_link_local_end"`
			`SUBSYSTEM!="net", GOTO="net_link_local_end"`

			`# Network interfaces for which only Link-Local communication (i.e. IPv4LL, …)`
			`# makes sense, because they almost certainy will point to another host, not an`
			`# internet router.`

			`# (Note: matches against VID/PID go into 82-net-auto-link-local.hwdb instead)`

			`# Thunderbolt host-to-host connections`
			`DRIVERS=="thunderbolt-net", ENV{ID_NET_AUTO_LINK_LOCAL_ONLY}="1"`

			`LABEL="net_link_local_end"`