chore: hy client should not force UDP addr for quic Dial

pkg/core/client.go

@@ -25,7 +25,9 @@ import (
 var ErrClosed = errors.New("closed")
 
 type Client struct {
-	serverAddr       string
+	serverAddr string
+	serverName string // QUIC SNI
+
 	sendBPS, recvBPS uint64
 	auth             []byte
 
@@ -50,8 +52,18 @@ func NewClient(serverAddr string, auth []byte, tlsConfig *tls.Config, quicConfig
 	pktConnFunc pktconns.ClientPacketConnFunc, sendBPS uint64, recvBPS uint64, quicReconnectFunc func(err error),
 ) (*Client, error) {
 	quicConfig.DisablePathMTUDiscovery = quicConfig.DisablePathMTUDiscovery || pmtud.DisablePathMTUDiscovery
+	// QUIC wants server name, but our serverAddr is usually host:port,
+	// so we try to extract it from serverAddr.
+	serverName, _, err := net.SplitHostPort(serverAddr)
+	if err != nil {
+		// It's possible that we have some weird serverAddr combined with weird PacketConn implementation,
+		// that doesn't follow the standard host:port format. So it's ok if we run into error here.
+		// Server name should be set in tlsConfig in that case.
+		serverName = ""
+	}
 	c := &Client{
 		serverAddr:        serverAddr,
+		serverName:        serverName,
 		sendBPS:           sendBPS,
 		recvBPS:           recvBPS,
 		auth:              auth,
@@ -75,16 +87,12 @@ func (c *Client) connect() error {
 		_ = c.pktConn.Close()
 	}
 	// New connection
-	pktConn, err := c.pktConnFunc(c.serverAddr)
+	pktConn, sAddr, err := c.pktConnFunc(c.serverAddr)
 	if err != nil {
 		return err
 	}
-	serverUDPAddr, err := net.ResolveUDPAddr("udp", c.serverAddr)
-	if err != nil {
-		_ = pktConn.Close()
-		return err
-	}
-	quicConn, err := quic.Dial(pktConn, serverUDPAddr, c.serverAddr, c.tlsConfig, c.quicConfig)
+	// Dial QUIC
+	quicConn, err := quic.Dial(pktConn, sAddr, c.serverName, c.tlsConfig, c.quicConfig)
 	if err != nil {
 		_ = pktConn.Close()
 		return err