Take the line rate as a constant so nothing has to be plugged in, and drop the config box

system.go

@@ -585,6 +585,9 @@ func withIoctlSocket(fn func(fd int) []checkResult) []checkResult {
 	return fn(fd)
 }
 
+// Nothing here waits for a carrier: the two ports are the two ends of the cable
+// under test, so with no cable there will never be one, and a dead wire is a
+// result to report rather than a reason to refuse to start.
 func configureSystem(ifnames []string, ethertypes []uint16) []checkResult {
 	return withIoctlSocket(func(fd int) []checkResult {
 		out := []checkResult{checkGovernor(wantGovernor)}