[#549] network/Address: Add TLS

There is no TLS protocol support in
`go-multiaddr` library, but there is
public function that can register any
protocol that can be implemented outside
the library. Also `TLSEnabled` function
for parsing TLS protocol from
`network.Address` was added.

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>

pkg/network/tls.go

@@ -0,0 +1,67 @@
+package network
+
+import (
+	"fmt"
+
+	"github.com/multiformats/go-multiaddr"
+)
+
+// There is implementation of TLS protocol for
+// github.com/multiformats/go-multiaddr library in this file.
+//
+// After addition TLS protocol via `multiaddr.AddProtocol` function
+// the library is ready to parse "tls" protocol with empty body, e.g.:
+//
+//		"/dns4/localhost/tcp/8080/tls"
+
+const (
+	tlsProtocolName = "tls"
+
+	// tlsProtocolCode is chosen according to its draft version's code in
+	// original multiaddr repository: https://github.com/multiformats/multicodec.
+	tlsProtocolCode = 0x01c0
+)
+
+// tls var is used for (un)wrapping other multiaddrs around TLS multiaddr.
+var tls multiaddr.Multiaddr
+
+func init() {
+	tlsProtocol := multiaddr.Protocol{
+		Name:  tlsProtocolName,
+		Code:  tlsProtocolCode,
+		Size:  0,
+		VCode: multiaddr.CodeToVarint(tlsProtocolCode),
+	}
+
+	err := multiaddr.AddProtocol(tlsProtocol)
+	if err != nil {
+		panic(fmt.Errorf("could not add 'TLS' protocol to multiadd library: %w", err))
+	}
+
+	tls, err = multiaddr.NewMultiaddr("/" + tlsProtocolName)
+	if err != nil {
+		panic(fmt.Errorf("could not init 'TLS' protocol with multiadd library: %w", err))
+	}
+}
+
+// TLSEnabled searches for wrapped TLS protocol in multiaddr.
+func (a Address) TLSEnabled() bool {
+	for _, protoc := range a.ma.Protocols() {
+		if protoc.Code == tlsProtocolCode {
+			return true
+		}
+	}
+
+	return false
+}
+
+// AddTLS encapsulates a Address if there is no TLS yet.
+func (a *Address) AddTLS() {
+	// not need to add TLS if it is
+	// already included
+	if a.TLSEnabled() {
+		return
+	}
+
+	a.ma = a.ma.Encapsulate(tls)
+}