move IPPROTO_TLS to netdev to avoid src/syscall dependency

netdev.go

@@ -4,6 +4,12 @@ import (
 	"time"
 )
 
+const (
+	// Made up, not a real IP protocol number.  This is used to create a
+	// TLS socket on the device, assuming the device supports mbed TLS.
+	IPPROTO_TLS = 0xFE
+)
+
 // netdev is the current netdev, set by the application with useNetdev()
 var netdev netdever
 

tlssock.go

@@ -31,7 +31,7 @@ func DialTLS(addr string) (*TLSConn, error) {
 		port = 443
 	}
 
-	fd, err := netdev.Socket(syscall.AF_INET, syscall.SOCK_STREAM, syscall.IPPROTO_TLS)
+	fd, err := netdev.Socket(syscall.AF_INET, syscall.SOCK_STREAM, IPPROTO_TLS)
 	if err != nil {
 		return nil, err
 	}