macOS 26.4 emits RTM_MISS on the routing socket for every failed route
lookup. skipRouteMessage never inspected the message type, so each miss
woke the monitor as a link change and triggered a netcheck. On networks
without an IPv6 default route the netcheck's IPv6 DERP probes fail and
emit more RTM_MISS messages, sustaining the loop indefinitely: netchecks
run at roughly 40x the intended rate, with sustained probe traffic and
corresponding CPU and battery cost.
RTM_MISS scales with traffic volume, not network state, and is never
the leading signal for a topology change: route withdrawals emit
RTM_DELETE synchronously before any subsequent lookup can miss, so
ignoring it loses no signal. Other routing daemons (bird, dhcpcd, frr)
ignore it as well.
Same fix as coder/tailscale@e956a95074.
Fixes#19324
Signed-off-by: Doug Bryant <dougbryant@anthropic.com>
CPU profiling a containerboot subnet router on a large tailnet showed
roughly 40% of CPU spent in serveWatchIPNBus JSON-encoding the full
netmap on every update. containerboot only reads SelfNode fields from
those notifications (and does a peer lookup when TailnetTargetFQDN is
set), so it does not need every intermediate netmap delta.
Set ipn.NotifyRateLimit on all three WatchIPNBus calls so netmap
notifications are coalesced to one per 3s. Initial-state delivery is
unaffected since the rateLimitingBusSender flushes the first send
immediately.
Updates #cleanup
Signed-off-by: Doug Bryant <dougbryant@anthropic.com>
Doug Bryant