关于 DHCPv6 获取的 PD 前缀 Lifetime 可能导致 wan6 定期断连的问题

OP 路由器上跑的是 openwrt 官方 23.05rc3 ，WAN6 配置成 DHCPv6 客户端，从 ISP 的服务器获取 PD 前缀。 最近发现 WAN6 大约 6 小时左右就会掉线一次
本来以为是 cx341a 网卡的问题，换到 i226 上发现还是有问题。日志中 Netifd 提示：
daemon.notice netifd: Interface 'wan6' has lost the connection
10s 内又重新连上

抓包 ISP 的 DHCPv6 数据包发现：
Ethernet II, Src: Cisco_3d:de:8c (10:f9:20:3d:de:8c), Dst: NECPlatf_ (<secret>)
Internet Protocol Version 6, Src: fe80::12f9:20ff:fe3d:de8c, Dst: fe80::<secret>
User Datagram Protocol, Src Port: 547, Dst Port: 546
DHCPv6
Message type: Advertise (2)
Transaction ID: 0x8540de
Client Identifier
Server Identifier
Reconfigure Accept
Identity Association for Prefix Delegation
Option: Identity Association for Prefix Delegation (25)
Length: 41
IAID: 00000000
T1: 7200
T2: 10800
IA Prefix
Option: IA Prefix (26)
Length: 25
Preferred lifetime: 12600
Valid lifetime: 14400
Prefix length: 56
Prefix address: 2400:2410:<secret>00::

每次分配的 PD 前缀都是固定的。
理论上不应该在过期之前自动续租吗？不知为何出现了 6 小时整 wan6 就会失去连接的问题。不桥接 openwrt 直接把运营商路由器接到 ONU 上就没有这个问题，对运营商路由器抓包里 IAPD 的 Lifetime 是完全一样的。

在 WAN6 连接 2 小时 5 分钟时运行 ifstatus wan6：

{ "up": true, "pending": false, "available": true, "autostart": true, "dynamic": false, "uptime": 8442, "l3_device": "eth2", "proto": "dhcpv6", "device": "eth2", "metric": 0, "dns_metric": 0, "delegation": true, "ipv4-address": [

    ],
    "ipv6-address": [

    ],
    "ipv6-prefix": [
            {
                    "address": "2400:2410:<secret>00::",
                    "mask": 56,
                    "preferred": 11358,
                    "valid": 13158,
                    "class": "wan6",
                    "assigned": {
                            "lan": {
                                    "address": "2400:2410:<secret>00::",
                                    "mask": 64
                            }
                    }
            }
    ],
    "ipv6-prefix-assignment": [

    ],
    "route": [
            {
                    "target": "::",
                    "mask": 0,
                    "nexthop": "fe80::12f9:20ff:fe3d:de8c",
                    "metric": 512,
                    "valid": 1798,
                    "source": "2400:2410:<secret>00::/56"
            }
    ],
    "dns-server": [
            "2404:1a8:7f01:a::3",
            "2404:1a8:7f01:b::3"
    ],
    "dns-search": [
            "flets-east.jp",
            "iptvf.jp"
    ],
    "neighbors": [

    ],
    "inactive": {
            "ipv4-address": [

            ],
            "ipv6-address": [

            ],
            "route": [

            ],
            "dns-server": [

            ],
            "dns-search": [

            ],
            "neighbors": [

            ]
    },
    "data": {
            "passthru": "00170020240401a87f01000a0000000000000003240401a87f01000b0000000000000003001800190a666c6574732d65617374026a7000056970747666026a7000001f0020240401a811020000000000000000000a240401a811020000000000000000000b"
    }

}