client/tailscale,ipn/{ipnlocal,localapi}: check UDP GRO config (#10071)

Updates tailscale/corp#9990

Signed-off-by: Jordan Whited <jordan@tailscale.com>

net/netkernelconf/netkernelconf_default.go

@@ -0,0 +1,12 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build !linux
+
+package netkernelconf
+
+// CheckUDPGROForwarding is unimplemented for non-Linux platforms. Refer to the
+// docstring in _linux.go.
+func CheckUDPGROForwarding(tunInterface, defaultRouteInterface string) (warn, err error) {
+	return nil, nil
+}