From d34e75f4738322ee5c805d4b09b8b4c1e8fdaebd Mon Sep 17 00:00:00 2001
From: Cursor Agent <cursoragent@cursor.com>
Date: Tue, 14 Jul 2026 03:36:31 +0000
Subject: [PATCH 1/2] feat: add ECH multiaddr protocol

Co-authored-by: Marco Munizaga <git@marcopolo.io>
---
 ech_test.go    | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
 protocols.go   |  9 +++++++++
 transcoders.go | 27 +++++++++++++++++++++++++++
 3 files changed, 86 insertions(+)
 create mode 100644 ech_test.go

diff --git a/ech_test.go b/ech_test.go
new file mode 100644
index 0000000..fe46422
--- /dev/null
+++ b/ech_test.go
@@ -0,0 +1,50 @@
+package multiaddr
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestECHProtocol(t *testing.T) {
+	echConfigList := []byte{0x00, 0x04, 0xff, 0xff, 0x00, 0x00}
+	const encodedECHConfigList = "uAAT__wAA"
+
+	protocol := ProtocolWithName("ech")
+	require.Equal(t, P_ECH, protocol.Code)
+	require.Equal(t, []byte{0xf9, 0x4c}, protocol.VCode)
+	require.Equal(t, LengthPrefixedVarSize, protocol.Size)
+	require.NotNil(t, protocol.Transcoder)
+	require.Equal(t, protocol, ProtocolWithCode(P_ECH))
+
+	component, err := NewComponent("ech", encodedECHConfigList)
+	require.NoError(t, err)
+	require.Equal(t, "/ech/"+encodedECHConfigList, component.String())
+	require.Equal(t, echConfigList, component.RawValue())
+	require.Equal(t, append([]byte{0xf9, 0x4c, 0x06}, echConfigList...), component.Bytes())
+
+	addr, err := NewMultiaddr("/ip4/192.0.2.1/tcp/443/tls/ech/" + encodedECHConfigList)
+	require.NoError(t, err)
+	require.Equal(t, "/ip4/192.0.2.1/tcp/443/tls/ech/"+encodedECHConfigList, addr.String())
+
+	value, err := addr.ValueForProtocol(P_ECH)
+	require.NoError(t, err)
+	require.Equal(t, encodedECHConfigList, value)
+
+	fromBytes, err := NewMultiaddrBytes(addr.Bytes())
+	require.NoError(t, err)
+	require.True(t, addr.Equal(fromBytes))
+}
+
+func TestECHAcceptsAnyMultibaseEncoding(t *testing.T) {
+	addr, err := NewMultiaddr("/quic-v1/ech/baacp77yaaa")
+	require.NoError(t, err)
+	require.Equal(t, "/quic-v1/ech/uAAT__wAA", addr.String())
+}
+
+func TestECHRejectsInvalidValues(t *testing.T) {
+	for _, value := range []string{"not-multibase", "u"} {
+		_, err := NewComponent("ech", value)
+		require.Error(t, err)
+	}
+}
diff --git a/protocols.go b/protocols.go
index 0e74b5a..a1d76ea 100644
--- a/protocols.go
+++ b/protocols.go
@@ -34,6 +34,7 @@ const (
 	P_GARLIC32          = 447
 	P_P2P_WEBRTC_DIRECT = 276 // Deprecated. use webrtc-direct instead
 	P_TLS               = 448
+	P_ECH               = 9849
 	P_SNI               = 449
 	P_NOISE             = 454
 	P_WS                = 477
@@ -245,6 +246,13 @@ var (
 		Code:  P_TLS,
 		VCode: CodeToVarint(P_TLS),
 	}
+	protoECH = Protocol{
+		Name:       "ech",
+		Code:       P_ECH,
+		VCode:      CodeToVarint(P_ECH),
+		Size:       LengthPrefixedVarSize,
+		Transcoder: TranscoderECH,
+	}
 	protoSNI = Protocol{
 		Name:       "sni",
 		Size:       LengthPrefixedVarSize,
@@ -324,6 +332,7 @@ func init() {
 		protoUNIX,
 		protoP2P_WEBRTC_DIRECT,
 		protoTLS,
+		protoECH,
 		protoSNI,
 		protoNOISE,
 		protoWS,
diff --git a/transcoders.go b/transcoders.go
index 03b39ae..30e2bec 100644
--- a/transcoders.go
+++ b/transcoders.go
@@ -463,6 +463,33 @@ func validateCertHash(b []byte) error {
 	return err
 }
 
+var TranscoderECH = NewTranscoderFromFunctions(echStB, echBtS, validateECH)
+
+func echStB(s string) ([]byte, error) {
+	_, data, err := multibase.Decode(s)
+	if err != nil {
+		return nil, err
+	}
+	if err := validateECH(data); err != nil {
+		return nil, err
+	}
+	return data, nil
+}
+
+func echBtS(b []byte) (string, error) {
+	if err := validateECH(b); err != nil {
+		return "", err
+	}
+	return multibase.Encode(multibase.Base64url, b)
+}
+
+func validateECH(b []byte) error {
+	if len(b) == 0 {
+		return errors.New("empty ECHConfigList")
+	}
+	return nil
+}
+
 var TranscoderHTTPPath = NewTranscoderFromFunctions(httpPathStB, httpPathBtS, validateHTTPPath)
 
 func httpPathStB(s string) ([]byte, error) {

From 7d6b2ed55e0702fdf8d530863ebb2b3dc3e6df88 Mon Sep 17 00:00:00 2001
From: Cursor Agent <cursoragent@cursor.com>
Date: Tue, 14 Jul 2026 03:37:21 +0000
Subject: [PATCH 2/2] test: compare ECH protocol lookup fields

Co-authored-by: Marco Munizaga <git@marcopolo.io>
---
 ech_test.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ech_test.go b/ech_test.go
index fe46422..8174e36 100644
--- a/ech_test.go
+++ b/ech_test.go
@@ -15,7 +15,7 @@ func TestECHProtocol(t *testing.T) {
 	require.Equal(t, []byte{0xf9, 0x4c}, protocol.VCode)
 	require.Equal(t, LengthPrefixedVarSize, protocol.Size)
 	require.NotNil(t, protocol.Transcoder)
-	require.Equal(t, protocol, ProtocolWithCode(P_ECH))
+	require.Equal(t, "ech", ProtocolWithCode(P_ECH).Name)
 
 	component, err := NewComponent("ech", encodedECHConfigList)
 	require.NoError(t, err)