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77d2c87b17
Router.Set reconciled tailscale0's addresses only against the in-memory r.addrs map, which starts empty each run. After a restart the kernel can still hold the addresses a previous profile put on tailscale0. With no record of them, Set never removed them, leaving two tailnets' CGNAT addresses on the interface. That broke connectivity, because the kernel could source traffic from the wrong IP. Fix this by scanning the addresses actually on the interface and, after reconciling the desired set, removing any in Tailscale's CGNAT/ULA ranges that aren't in the config. Non-Tailscale addresses are never touched, and IPv6 addresses are skipped when IPv6 is unavailable, since delAddress no-ops there. To avoid a netlink dump on every Set, the scan runs only on the first Set and when the desired address set changes. This also needs the iptables DelLoopbackRule to tolerate a missing rule: an orphan left by a previous instance never went through AddLoopbackRule here, and iptables (unlike nftables) errors when deleting an absent rule, which would otherwise block the address delete. Fixes #19974 Signed-off-by: Brendan Creane <bcreane@gmail.com>