It'll be called a bunch, so worth a bit of effort. Could go further, but not yet.
(really, should hook into wgengine/monitor and only re-read on netlink changes?)
name old time/op new time/op delta
DefaultRouteInterface-8 60.8µs ±11% 44.6µs ± 5% -26.65% (p=0.000 n=20+19)
name old alloc/op new alloc/op delta
DefaultRouteInterface-8 3.29kB ± 0% 0.55kB ± 0% -83.21% (p=0.000 n=20+20)
name old allocs/op new allocs/op delta
DefaultRouteInterface-8 9.00 ± 0% 6.00 ± 0% -33.33% (p=0.000 n=20+20)
Brad Fitzpatrick