From 141f79ce0b50f913f39241a8f6f64224a77a098a Mon Sep 17 00:00:00 2001
From: Leon Rinkel <leon@rinkel.me>
Date: Wed, 1 May 2024 10:36:14 +0200
Subject: [PATCH] Add support for SCION addresses

---
 multiaddr_test.go | 20 ++++++++++++++++++++
 protocols.go      | 10 ++++++++++
 transcoders.go    | 30 ++++++++++++++++++++++++++++++
 3 files changed, 60 insertions(+)

diff --git a/multiaddr_test.go b/multiaddr_test.go
index b33e94d..8f0752c 100644
--- a/multiaddr_test.go
+++ b/multiaddr_test.go
@@ -88,6 +88,10 @@ func TestConstructFails(t *testing.T) {
 		"/",
 		"",
 		"/p2p/QmxoHT6iViN5xAjoz1VZ553cL31U9F94ht3QvWR1FrEbZY", // sha256 multihash with digest len > 32
+		"/scion",
+		"/scion//udp/1234",
+		"/scion/0-",
+		"/scion/1234",
 	}
 
 	for _, a := range cases {
@@ -192,6 +196,10 @@ var good = []string{
 	"/ip4/127.0.0.1/tcp/127/wss",
 	"/ip4/127.0.0.1/tcp/127/webrtc-direct",
 	"/ip4/127.0.0.1/tcp/127/webrtc",
+	"/scion/0-0",
+	"/scion/1-ff00:0:110",
+	"/scion/1-ff00:0:110/ip4/1.2.3.4",
+	"/scion/1-ff00:0:110/ip6/::ffff:127.0.0.1/udp/111",
 }
 
 func TestConstructSucceeds(t *testing.T) {
@@ -433,6 +441,12 @@ func TestEncapsulate(t *testing.T) {
 	if d != nil {
 		t.Error("decapsulate /ip4 failed: ", d)
 	}
+
+	m5, _ := NewMultiaddr("/scion/1-ff00:0:110")
+	e := m5.Encapsulate(m)
+	if s := e.String(); s != "/scion/1-ff00:0:110/ip4/127.0.0.1/udp/1234" {
+		t.Error("encapsulate /scion/1-ff00:0:110/ip4/127.0.0.1/udp/1234 failed.", s)
+	}
 }
 
 func TestDecapsulateComment(t *testing.T) {
@@ -541,6 +555,11 @@ func TestGetValue(t *testing.T) {
 	a = newMultiaddr(t, "/ip4/0.0.0.0/unix/a/b/c/d") // ending in a path one.
 	assertValueForProto(t, a, P_IP4, "0.0.0.0")
 	assertValueForProto(t, a, P_UNIX, "/a/b/c/d")
+
+	a = newMultiaddr(t, "/scion/1-ff00:0:110/ip4/127.0.0.1/udp/1234")
+	assertValueForProto(t, a, P_SCION, "1-ff00:0:110")
+	assertValueForProto(t, a, P_IP4, "127.0.0.1")
+	assertValueForProto(t, a, P_UDP, "1234")
 }
 
 func FuzzNewMultiaddrBytes(f *testing.F) {
@@ -627,6 +646,7 @@ func TestRoundTrip(t *testing.T) {
 		"/ip4/127.0.0.1/udp/1234/quic-v1/webtransport/certhash/uEiDDq4_xNyDorZBH3TlGazyJdOWSwvo4PUo5YHFMrvDE8g",
 		"/p2p/QmbHVEEepCi7rn7VL7Exxpd2Ci9NNB6ifvqwhsrbRMgQFP",
 		"/p2p/QmbHVEEepCi7rn7VL7Exxpd2Ci9NNB6ifvqwhsrbRMgQFP/unix/a/b/c",
+		"/scion/1-ff00:0:110/ip6/::ffff:127.0.0.1/tcp/111",
 	} {
 		ma, err := NewMultiaddr(s)
 		if err != nil {
diff --git a/protocols.go b/protocols.go
index b01e6cb..7eb6e21 100644
--- a/protocols.go
+++ b/protocols.go
@@ -40,6 +40,7 @@ const (
 	P_PLAINTEXTV2       = 7367777
 	P_WEBRTC_DIRECT     = 280
 	P_WEBRTC            = 281
+	P_SCION             = 13639680
 )
 
 var (
@@ -273,6 +274,14 @@ var (
 		Code:  P_WEBRTC,
 		VCode: CodeToVarint(P_WEBRTC),
 	}
+	protoSCION = Protocol{
+		Name:       "scion",
+		Code:       P_SCION,
+		VCode:      CodeToVarint(P_SCION),
+		Size:       LengthPrefixedVarSize,
+		Path:       false,
+		Transcoder: TranscoderSCION,
+	}
 )
 
 func init() {
@@ -313,6 +322,7 @@ func init() {
 		protoPlaintextV2,
 		protoWebRTCDirect,
 		protoWebRTC,
+		protoSCION,
 	} {
 		if err := AddProtocol(p); err != nil {
 			panic(err)
diff --git a/transcoders.go b/transcoders.go
index 5387740..2d84cce 100644
--- a/transcoders.go
+++ b/transcoders.go
@@ -454,3 +454,33 @@ func validateCertHash(b []byte) error {
 	_, err := mh.Decode(b)
 	return err
 }
+
+var TranscoderSCION = NewTranscoderFromFunctions(scionStB, scionBtS, scionVal)
+
+func scionVal(b []byte) error {
+	// SCION IA is 16 bit ISD and 48 bit AS numbers separated by "-"
+	// ISD numbers formatted as decimal, AS numbering similar to IPv6
+	// E.g.: "0-0" or "1234-ff00:0:110"
+	if len(b) < 3 {
+		return fmt.Errorf("byte slice too short: %d", len(b))
+	}
+	if minus := bytes.IndexByte(b, '-'); minus < 0 {
+		return errors.New("scion addresses must contain '-'")
+	}
+	return nil
+}
+
+func scionStB(s string) ([]byte, error) {
+	b := []byte(s)
+	if err := scionVal(b); err != nil {
+		return nil, err
+	}
+	return b, nil
+}
+
+func scionBtS(b []byte) (string, error) {
+	if err := scionVal(b); err != nil {
+		return "", err
+	}
+	return string(b), nil
+}