[Bug]: 先做上传速度测试，然后做下载速度测试，下载的慢启动时间过长 #485
Description
What happened?
我使用xquic做速度测试，在建立连接的xqc_conn上先创建一个stream用于上传数据，速度在1秒内就能达到100mbps，并保持稳定，20秒后关闭此stream。等待10秒后，再在原来的xqc_conn上创建一个stream，做下载测试，此时下载过程的慢启动很慢，需要20多秒才能达到高速，此现象在环境中必现。客户端和服务器rtt 250ms左右，网络较好，偶尔丢包
速度打印如下
conn handshake, start upload
2025-05-29 06:47:31.909 speed: 134.21mbps/s
2025-05-29 06:47:32.901 speed: 0.0kbps/s
2025-05-29 06:47:34.216 speed: 177.1mbps/s
2025-05-29 06:47:35.102 speed: 197.84mbps/s
2025-05-29 06:47:35.939 speed: 38.25mbps/s
2025-05-29 06:47:37.627 speed: 205.52mbps/s
2025-05-29 06:47:37.921 speed: 134.21mbps/s
2025-05-29 06:47:39.106 speed: 88.90mbps/s
2025-05-29 06:47:39.979 speed: 154.25mbps/s
2025-05-29 06:47:41.235 speed: 88.83mbps/s
2025-05-29 06:47:42.991 speed: 259.78mbps/s
2025-05-29 06:47:43.216 speed: 88.70mbps/s
2025-05-29 06:47:43.900 speed: 103.69mbps/s
2025-05-29 06:47:45.053 speed: 109.39mbps/s
2025-05-29 06:47:46.073 speed: 197.82mbps/s
2025-05-29 06:47:47.073 speed: 3.46mbps/s
2025-05-29 06:47:47.912 speed: 197.53mbps/s
2025-05-29 06:47:48.907 speed: 238.21mbps/s
2025-05-29 06:47:49.917 speed: 169.13mbps/s
2025-05-29 06:47:50.904 speed: 134.21mbps/s
start delay ====
2025-05-29 06:47:51.913 speed: 25.31mbps/s
2025-05-29 06:47:52.912 speed: 0.0kbps/s
2025-05-29 06:47:53.910 speed: 0.0kbps/s
2025-05-29 06:47:54.908 speed: 0.0kbps/s
2025-05-29 06:47:55.906 speed: 0.0kbps/s
2025-05-29 06:47:56.905 speed: 0.0kbps/s
2025-05-29 06:47:57.902 speed: 0.0kbps/s
2025-05-29 06:47:58.917 speed: 0.0kbps/s
2025-05-29 06:47:59.903 speed: 0.0kbps/s
2025-05-29 06:48:00.916 speed: 0.0kbps/s
start download ====
2025-05-29 06:48:01.911 speed: 217.17kbps/s
2025-05-29 06:48:02.913 speed: 339.55kbps/s
2025-05-29 06:48:03.910 speed: 377.12kbps/s
2025-05-29 06:48:04.910 speed: 481.3kbps/s
2025-05-29 06:48:05.906 speed: 537.29kbps/s
2025-05-29 06:48:06.906 speed: 556.48kbps/s
2025-05-29 06:48:07.904 speed: 688.53kbps/s
2025-05-29 06:48:08.903 speed: 735.36kbps/s
2025-05-29 06:48:09.907 speed: 876.84kbps/s
2025-05-29 06:48:10.903 speed: 971.49kbps/s
2025-05-29 06:48:11.907 speed: 1.10mbps/s
2025-05-29 06:48:12.904 speed: 1.31mbps/s
2025-05-29 06:48:13.906 speed: 1.41mbps/s
2025-05-29 06:48:14.907 speed: 1.67mbps/s
2025-05-29 06:48:15.904 speed: 1.91mbps/s
2025-05-29 06:48:16.908 speed: 2.22mbps/s
2025-05-29 06:48:17.903 speed: 2.52mbps/s
2025-05-29 06:48:18.906 speed: 2.90mbps/s
2025-05-29 06:48:19.902 speed: 3.29mbps/s
2025-05-29 06:48:20.905 speed: 3.98mbps/s
2025-05-29 06:48:21.905 speed: 4.42mbps/s
2025-05-29 06:48:22.907 speed: 5.25mbps/s
2025-05-29 06:48:23.906 speed: 6.12mbps/s
2025-05-29 06:48:24.904 speed: 6.91mbps/s
2025-05-29 06:48:25.905 speed: 8.16mbps/s
2025-05-29 06:48:26.905 speed: 9.38mbps/s
2025-05-29 06:48:27.905 speed: 10.86mbps/s
2025-05-29 06:48:28.905 speed: 12.85mbps/s
2025-05-29 06:48:29.906 speed: 14.69mbps/s
2025-05-29 06:48:30.905 speed: 16.95mbps/s
2025-05-29 06:48:31.904 speed: 20.37mbps/s
2025-05-29 06:48:32.904 speed: 22.56mbps/s
2025-05-29 06:48:33.905 speed: 24.23mbps/s
2025-05-29 06:48:34.906 speed: 39.53mbps/s
2025-05-29 06:48:35.904 speed: 71.79mbps/s
2025-05-29 06:48:36.905 speed: 88.83mbps/s
2025-05-29 06:48:37.905 speed: 100.35mbps/s
2025-05-29 06:48:38.905 speed: 100.72mbps/s
2025-05-29 06:48:39.905 speed: 108.13mbps/s
2025-05-29 06:48:40.906 speed: 125.56mbps/s
2025-05-29 06:48:41.905 speed: 122.9mbps/s
2025-05-29 06:48:42.905 speed: 111.69mbps/s
2025-05-29 06:48:43.904 speed: 171.40mbps/s
2025-05-29 06:48:44.904 speed: 185.58mbps/s
2025-05-29 06:48:45.904 speed: 227.36mbps/s
2025-05-29 06:48:46.904 speed: 219.70mbps/s
2025-05-29 06:48:47.904 speed: 124.19mbps/s
2025-05-29 06:48:48.904 speed: 287.93mbps/s
2025-05-29 06:48:49.905 speed: 342.54mbps/s
2025-05-29 06:48:50.904 speed: 322.12mbps/s
2025-05-29 06:48:51.905 speed: 252.72mbps/s
2025-05-29 06:48:52.905 speed: 218.1mbps/s
Steps To Reproduce
https://github.com/shungo2020/quic
测试代码可复现