问题描述
家里配置了一套软路由，使用有 1~2 年都非常稳定，速度和稳定性都很好。
但是，上周末家里的软路由出现问题，WAN 口频繁掉线，掉线后在 2 分钟之后又自动重连，过 30 分钟~2 个小时之间又再次掉线重连，该现象一直持续。
查看日志后关键信息显示是 Interface 'wan' has link connectivity loss 紧接着就 Interface 'wan' is now down （具体日志在后文）
配置信息
上海电信宽带 + 光猫 DHCP 自动拨号
软路由是 R2S/R5S + github 主流固件
路由器是 Redmi AX5 + AX 5400
网络链路是 光猫（千兆口）-> 软路由 Wan -> 软路由 Lan -> 无线路由器 Wan （所有设备都是连接 Redmi 无线路由器）
排查思路及结果
分别是 R2S/R5S + 两套 openwrt 固件（都重刷 DHDAXCW+stupidloud ）总共四次尝试，均是相同报错。备注：只换了机器，网线和电源还是一套
无线路由器有线插了 NAS+树莓派，把它们都拔下来后，依旧是相同报错。
无线路由器从 AX5 换成 AX5400 ，网络配置不变，依旧是相同报错。
把软路由从家庭网络中去除，变成 光猫 -> 无线路由器，因为没有 openwrt 了，获取不到日志，但使用过程是「正常」的，玩了几把游戏都没有掉线体验。
相关日志
全量日志： https://gist.github.com/Wei-Xia/58e206ec7cb6e11b3c7f1c14f6bb3c0b
报错部分：
Sun Aug 6 21:36:56 2023 daemon.notice netifd: Network device 'eth0' link is up
Sun Aug 6 21:36:56 2023 daemon.notice netifd: Interface 'wan' has link connectivity
Sun Aug 6 21:36:56 2023 daemon.notice netifd: Interface 'wan' is setting up now
Sun Aug 6 21:36:56 2023 kern.info kernel: [21954.520425] rk_gmac-dwmac fe2a0000.ethernet eth0: Link is Up - 1Gbps/Full - flow control off
Sun Aug 6 21:36:56 2023 daemon.notice netifd: Interface 'wan6' has link connectivity
Sun Aug 6 21:36:56 2023 daemon.notice netifd: Interface 'wan6' is setting up now
Sun Aug 6 21:36:56 2023 daemon.notice netifd: wan (26341): udhcpc: started, v1.36.0
Sun Aug 6 21:36:56 2023 daemon.notice netifd: wan (26341): udhcpc: broadcasting discover
Sun Aug 6 21:36:57 2023 kern.info kernel: [21955.468674] rk_gmac-dwmac fe2a0000.ethernet eth0: Link is Down
Sun Aug 6 21:36:57 2023 daemon.notice netifd: Network device 'eth0' link is down
Sun Aug 6 21:36:57 2023 daemon.notice netifd: Interface 'wan' has link connectivity loss
Sun Aug 6 21:36:57 2023 daemon.notice netifd: Interface 'wan6' has link connectivity loss
Sun Aug 6 21:36:57 2023 daemon.notice netifd: wan (26341): udhcpc: received SIGTERM
Sun Aug 6 21:36:57 2023 daemon.notice netifd: wan (26341): udhcpc: entering released state
Sun Aug 6 21:36:57 2023 daemon.notice netifd: wan (26341): Command failed: ubus call network.interface notify_proto { "action": 0, "link-up": false, "keep": false, "interface": "wan" } (Permission denied)
Sun Aug 6 21:36:57 2023 daemon.notice netifd: Interface 'wan' is now down
Sun Aug 6 21:36:57 2023 daemon.notice netifd: Interface 'wan6' is now down
Sun Aug 6 21:37:18 2023 daemon.notice netifd: Network device 'eth0' link is up
Sun Aug 6 21:37:18 2023 daemon.notice netifd: Interface 'wan' has link connectivity
Sun Aug 6 21:37:18 2023 daemon.notice netifd: Interface 'wan' is setting up now
Sun Aug 6 21:37:18 2023 daemon.notice netifd: Interface 'wan6' has link connectivity
Sun Aug 6 21:37:18 2023 daemon.notice netifd: Interface 'wan6' is setting up now
Sun Aug 6 21:37:18 2023 kern.info kernel: [21976.870422] rk_gmac-dwmac fe2a0000.ethernet eth0: Link is Up - 1Gbps/Full - flow control off
Sun Aug 6 21:37:18 2023 daemon.notice netifd: wan (27250): udhcpc: started, v1.36.0
Sun Aug 6 21:37:18 2023 daemon.notice netifd: wan (27250): udhcpc: broadcasting discover
Sun Aug 6 21:37:21 2023 kern.info kernel: [21979.893842] rk_gmac-dwmac fe2a0000.ethernet eth0: Link is Down
Sun Aug 6 21:37:21 2023 daemon.notice netifd: Network device 'eth0' link is down
Sun Aug 6 21:37:21 2023 daemon.notice netifd: Interface 'wan' has link connectivity loss
Sun Aug 6 21:37:21 2023 daemon.notice netifd: Interface 'wan6' has link connectivity loss
Sun Aug 6 21:37:21 2023 daemon.notice netifd: wan (27250): udhcpc: broadcasting discover
Sun Aug 6 21:37:21 2023 daemon.notice netifd: wan (27250): udhcpc: received SIGTERM
Sun Aug 6 21:37:21 2023 daemon.notice netifd: wan (27250): udhcpc: entering released state
Sun Aug 6 21:37:21 2023 daemon.notice netifd: wan (27250): Command failed: ubus call network.interface notify_proto { "action": 0, "link-up": false, "keep": false, "interface": "wan" } (Permission denied)
Sun Aug 6 21:37:21 2023 daemon.notice netifd: Interface 'wan' is now down
Sun Aug 6 21:37:21 2023 daemon.notice netifd: Interface 'wan6' is now down
Sun Aug 6 21:37:31 2023 daemon.notice netifd: Network device 'eth0' link is up
Sun Aug 6 21:37:31 2023 daemon.notice netifd: Interface 'wan' has link connectivity
Sun Aug 6 21:37:31 2023 daemon.notice netifd: Interface 'wan' is setting up now
Sun Aug 6 21:37:31 2023 daemon.notice netifd: Interface 'wan6' has link connectivity
Sun Aug 6 21:37:31 2023 daemon.notice netifd: Interface 'wan6' is setting up now
Sun Aug 6 21:37:31 2023 kern.info kernel: [21989.381455] rk_gmac-dwmac fe2a0000.ethernet eth0: Link is Up - 1Gbps/Full - flow control off
Sun Aug 6 21:37:31 2023 daemon.notice netifd: wan (27967): udhcpc: started, v1.36.0