route: remove RTM_LOCK on openbsd

RTM_LOCK is no longer defined on OpenBSD as of version 6.4, see and

CL 419180 broke the build on openbsd/arm64 and openbsd/mips64 due to
RTM_LOCK not being defined on these platforms because these ports were
based on OpenBSD versions newer than 6.4. Earlier OpenBSD versions are
no longer supported since Go 1.15 per

For golang/go#54035

Change-Id: I476a60ab2a082c7ddc763b5dbaf279ba47dcc1e1
TryBot-Result: Gopher Robot <>
Auto-Submit: Tobias Klauser <>
Reviewed-by: Cherry Mui <>
Run-TryBot: Tobias Klauser <>
Reviewed-by: Bryan Mills <>
diff --git a/route/sys_openbsd.go b/route/sys_openbsd.go
index 038fb77..21f1d3d 100644
--- a/route/sys_openbsd.go
+++ b/route/sys_openbsd.go
@@ -73,7 +73,6 @@
 		unix.RTM_LOSING:     rtm,
 		unix.RTM_REDIRECT:   rtm,
 		unix.RTM_MISS:       rtm,
-		unix.RTM_LOCK:       rtm,
 		unix.RTM_RESOLVE:    rtm,
 		unix.RTM_NEWADDR:    ifam,
 		unix.RTM_DELADDR:    ifam,