net/tcp: don't use MD5 signature and bind to device on non-Linux OS

net/tcp/listen.go

@@ -69,7 +69,7 @@ func (lf *ListenerFactory) NewListener(v *vrf.VRF, laddr *net.TCPAddr, ttl uint8
 	}
 
 	if v.Name() != vrf.DefaultVRFName {
-		err = unix.SetsockoptString(fd, SOL_IP, unix.SO_BINDTODEVICE, v.Name())
+		err = bindToDev(fd, v.Name())
 		if err != nil {
 			unix.Close(fd)
 			return nil, fmt.Errorf("unable to set SO_BINDTODEVICE (%s): %v", v.Name(), err)

net/tcp/md5sig.go

@@ -1,3 +1,5 @@
+//go:build linux
+
 package tcp
 
 import (

net/tcp/md5sig_stub.go

@@ -0,0 +1,12 @@
+//go:build !linux
+
+package tcp
+
+import (
+	"fmt"
+	"net"
+)
+
+func setTCPMD5Option(fd int, addr net.IP, md5secret string) error {
+	return fmt.Errorf("setting md5 is not supported")
+}

net/tcp/tcp.go

@@ -130,7 +130,7 @@ func (c *Conn) SetNoDelay() error {
 
 // SetBindToDev sets the SO_BINDTODEVICE option
 func (c *Conn) SetBindToDev(devName string) error {
-	return unix.SetsockoptString(c.fd, unix.IPPROTO_TCP, unix.SO_BINDTODEVICE, devName)
+	return bindToDev(c.fd, devName)
 }
 
 // MockConn is mocked TCP connection

net/tcp/tcp_linux.go

@@ -0,0 +1,10 @@
+//go:build linux
+
+package tcp
+
+import "golang.org/x/sys/unix"
+
+// bindToDev sets the SO_BINDTODEVICE option
+func bindToDev(fd int, devName string) error {
+	return unix.SetsockoptString(fd, unix.IPPROTO_TCP, unix.SO_BINDTODEVICE, devName)
+}

net/tcp/tcp_stub.go

@@ -0,0 +1,10 @@
+//go:build !linux
+
+package tcp
+
+import "fmt"
+
+// bindToDev sets the SO_BINDTODEVICE option
+func bindToDev(fd int, devName string) error {
+	return fmt.Errorf("binding to device is not supported")
+}