randomly generate the server config ID and check whether it matches

handshake/server_config.go

@@ -2,6 +2,7 @@ package handshake
 
 import (
 	"bytes"
+	"crypto/rand"
 
 	"github.com/lucas-clemente/quic-go/crypto"
 )
@@ -10,13 +11,20 @@ import (
 type ServerConfig struct {
 	kex crypto.KeyExchange
 	kd  *crypto.KeyData
+	ID  []byte
 }
 
 // NewServerConfig creates a new server config
 func NewServerConfig(kex crypto.KeyExchange, kd *crypto.KeyData) *ServerConfig {
+	id := make([]byte, 16)
+	_, err := rand.Reader.Read(id)
+	if err != nil {
+		panic(err)
+	}
 	return &ServerConfig{
 		kex: kex,
 		kd:  kd,
+		ID:  id,
 	}
 }
 
@@ -24,7 +32,7 @@ func NewServerConfig(kex crypto.KeyExchange, kd *crypto.KeyData) *ServerConfig {
 func (s *ServerConfig) Get() []byte {
 	var serverConfig bytes.Buffer
 	WriteHandshakeMessage(&serverConfig, TagSCFG, map[Tag][]byte{
-		TagSCID: []byte{0xC5, 0x1C, 0x73, 0x6B, 0x8F, 0x48, 0x49, 0xAE, 0xB3, 0x00, 0xA2, 0xD4, 0x4B, 0xA0, 0xCF, 0xDF},
+		TagSCID: s.ID,
 		TagKEXS: []byte("C255"),
 		TagAEAD: []byte("CC20"),
 		TagPUBS: append([]byte{0x20, 0x00, 0x00}, s.kex.PublicKey()...),