syscall: deprecate routing message APIs for BSD variants

Also removes unnecessary test cases for avoiding unexpected failures on
newer operating systems.

Updates #14724.

Change-Id: I2291585d951fb70383da68293a6ac1ff3524c7f7
Reviewed-on: https://go-review.googlesource.com/22452
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/src/syscall/route_bsd.go b/src/syscall/route_bsd.go
index fe8259b..b364eea 100644
--- a/src/syscall/route_bsd.go
+++ b/src/syscall/route_bsd.go
@@ -176,6 +176,8 @@
 // RouteRIB returns routing information base, as known as RIB,
 // which consists of network facility information, states and
 // parameters.
+//
+// Deprecated: Use golang.org/x/net/route instead.
 func RouteRIB(facility, param int) ([]byte, error) {
 	mib := []_C_int{CTL_NET, AF_ROUTE, 0, 0, _C_int(facility), _C_int(param)}
 	// Find size.
@@ -194,6 +196,8 @@
 }
 
 // RoutingMessage represents a routing message.
+//
+// Deprecated: Use golang.org/x/net/route instead.
 type RoutingMessage interface {
 	sockaddr() ([]Sockaddr, error)
 }
@@ -208,6 +212,8 @@
 
 // RouteMessage represents a routing message containing routing
 // entries.
+//
+// Deprecated: Use golang.org/x/net/route instead.
 type RouteMessage struct {
 	Header RtMsghdr
 	Data   []byte
@@ -252,6 +258,8 @@
 
 // InterfaceMessage represents a routing message containing
 // network interface entries.
+//
+// Deprecated: Use golang.org/x/net/route instead.
 type InterfaceMessage struct {
 	Header IfMsghdr
 	Data   []byte
@@ -272,6 +280,8 @@
 
 // InterfaceAddrMessage represents a routing message containing
 // network interface address entries.
+//
+// Deprecated: Use golang.org/x/net/route instead.
 type InterfaceAddrMessage struct {
 	Header IfaMsghdr
 	Data   []byte
@@ -316,6 +326,8 @@
 
 // ParseRoutingMessage parses b as routing messages and returns the
 // slice containing the RoutingMessage interfaces.
+//
+// Deprecated: Use golang.org/x/net/route instead.
 func ParseRoutingMessage(b []byte) (msgs []RoutingMessage, err error) {
 	nmsgs, nskips := 0, 0
 	for len(b) >= anyMessageLen {
@@ -341,6 +353,8 @@
 
 // ParseRoutingSockaddr parses msg's payload as raw sockaddrs and
 // returns the slice containing the Sockaddr interfaces.
+//
+// Deprecated: Use golang.org/x/net/route instead.
 func ParseRoutingSockaddr(msg RoutingMessage) ([]Sockaddr, error) {
 	sas, err := msg.sockaddr()
 	if err != nil {