[client] Fix udp forwarder deadline (#3364)

client/firewall/uspfilter/forwarder/udp.go

@@ -245,33 +245,29 @@ func (c *udpPacketConn) copy(ctx context.Context, dst net.Conn, src net.Conn, bu
 	defer bufPool.Put(bufp)
 	buffer := *bufp
 
-	if err := src.SetReadDeadline(time.Now().Add(udpTimeout)); err != nil {
-		return fmt.Errorf("set read deadline: %w", err)
-	}
-	if err := src.SetWriteDeadline(time.Now().Add(udpTimeout)); err != nil {
-		return fmt.Errorf("set write deadline: %w", err)
-	}
-
 	for {
-		select {
+		if ctx.Err() != nil {
-		case <-ctx.Done():
 			return ctx.Err()
-		default:
-			n, err := src.Read(buffer)
-			if err != nil {
-				if isTimeout(err) {
-					continue
-				}
-				return fmt.Errorf("read from %s: %w", direction, err)
-			}
-
-			_, err = dst.Write(buffer[:n])
-			if err != nil {
-				return fmt.Errorf("write to %s: %w", direction, err)
-			}
-
-			c.updateLastSeen()
 		}
+
+		if err := src.SetDeadline(time.Now().Add(udpTimeout)); err != nil {
+			return fmt.Errorf("set read deadline: %w", err)
+		}
+
+		n, err := src.Read(buffer)
+		if err != nil {
+			if isTimeout(err) {
+				continue
+			}
+			return fmt.Errorf("read from %s: %w", direction, err)
+		}
+
+		_, err = dst.Write(buffer[:n])
+		if err != nil {
+			return fmt.Errorf("write to %s: %w", direction, err)
+		}
+
+		c.updateLastSeen()
 	}
 }