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Linux flushes an interface's IPv6 addresses when the link goes down, so `Iface::link_up` failed with EHOSTUNREACH when re-adding the v6 default route on any dual-stack device: the gateway was no longer on-link. We now set `keep_addr_on_down=1` in every namespace so global addresses survive the transition. The kernel drops link-local addresses regardless of that sysctl, so `link_up` re-adds the seeded link-local as well. Closes #46 Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Frando
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September 11, 2026 17:07
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Iface::link_upfailed with EHOSTUNREACH on any dual-stack device afterlink_down, because Linux flushes IPv6 addresses when a link goes down and the v6 default route then has no on-link gateway. Every namespace now setskeep_addr_on_down=1so global addresses survive the transition. The kernel drops link-local addresses regardless of that sysctl, solink_upalso re-adds the seeded link-local, which restores the interface to its exact pre-down state.The new
link_down_up_dual_stacktest reproduces the failure from the issue and checks that both v6 addresses and v6 connectivity are back after the flap. I also verified theRouterPreset::Homescenario from the issue and theIpv6Profile::Realisticprofile manually.Closes #46
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