The down-script previously flushed the kill-switch source set on tunnel-down, which
disarmed the 'ip saddr @vpn_egress_gateway_src oifname != tun0 drop' rule exactly when
the tunnel was down — leaving fail-closed to ride only on the stale SNAT source being
non-routable (could leak if the edge NATed it). Retain the set instead: the drop rule
stays armed so any vpn-class packet leaving the WAN while the tunnel is down is EXPLICITLY
dropped (edge-independent). Safe because the up-script flush+re-adds the source on every
reconnect. Validated behavior: WS-NET fault-injection on k3s-dev-3 (2026-08-24).
Co-Authored-By: Claude Opus 4.8 <[email protected]>
jakman85andClaude Opus 4.8
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