chore: add early conn interface to decrease unneeded write

common/convert/util.go

@@ -6,6 +6,7 @@ import (
 	"math/rand"
 	"net/http"
 	"strings"
+	"time"
 
 	"github.com/gofrs/uuid"
 )
@@ -317,6 +318,6 @@ func SetUserAgent(header http.Header) {
 }
 
 func VerifyMethod(cipher, password string) (err error) {
-	_, err = shadowimpl.FetchMethod(cipher, password)
+	_, err = shadowimpl.FetchMethod(cipher, password, time.Now)
 	return
 }

common/net/sing.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"net"
 
+	"github.com/sagernet/sing/common"
 	"github.com/sagernet/sing/common/bufio"
 	"github.com/sagernet/sing/common/network"
 )
@@ -16,6 +17,13 @@ type ExtendedConn = network.ExtendedConn
 type ExtendedWriter = network.ExtendedWriter
 type ExtendedReader = network.ExtendedReader
 
+func NeedHandshake(conn any) bool {
+	if earlyConn, isEarlyConn := common.Cast[network.EarlyConn](conn); isEarlyConn && earlyConn.NeedHandshake() {
+		return true
+	}
+	return false
+}
+
 // Relay copies between left and right bidirectionally.
 func Relay(leftConn, rightConn net.Conn) {
 	_ = bufio.CopyConn(context.TODO(), leftConn, rightConn)