linux bridge 场景下的一个bug

nova-compute在尝试将一个tap设备加到网桥上，但是始终都无法加成功。

但是这个操作会触发 nova-postrouting-bottom 这种神奇的东西

2022-09-24 23:48:05.314 6 ERROR os_vif oslo_concurrency.processutils.ProcessExecutionError: Unexpected error while running command.
2022-09-24 23:48:05.314 6 ERROR os_vif Command: iptables-restore -c
2022-09-24 23:48:05.314 6 ERROR os_vif Exit code: 2
2022-09-24 23:48:05.314 6 ERROR os_vif Stdout: ''
2022-09-24 23:48:05.314 6 ERROR os_vif Stderr: "iptables-restore v1.8.4 (nf_tables): Chain 'nova-postrouting-bottom' does not exist\nError occurred at line: 10\nTry `iptables-restore -h' or 'iptables-restore --help' for more information.\n"

这个集群全是flat网络，没有安全组，根本用不上iptables。

这一连串反应导致nova-compute 频繁崩溃。

Converting VIF {"id": "46e9efe9-895a-47ff-aa76-96e2081f49c5", "address": "fa:16:3e:a1:09:22", "network": {"id": "6e84e478-6b59-4f9e-b927-44f20e242990", "bridge": "brq6e84e478-6b", "label": "manage", "subnets": [{"cidr": "10.120.24.0/21", "dns": [{"address": "10.100.1.10", "type": "dns", "version": 4, "meta": {}}], "gateway": {"address": "10.120.31.254", "type": "gateway", "version": 4, "meta": {}}, "ips": [{"address": "10.120.29.129", "type": "fixed", "version": 4, "meta": {}, "floating_ips": []}], "routes": [], "version": 4, "meta": {"dhcp_server": "10.120.29.3"}}], "meta": {"injected": false, "tenant_id": "f087ad5bdf8542faa4dc902793e37638", "mtu": 1500, "physical_network": "physnet3", "tunneled": false, "should_create_bridge": true}}, "type": "bridge", "details": {"connectivity": "l2", "port_filter": false}, "devname": "tap46e9efe9-89", "ovs_interfaceid": null, "qbh_params": null, "qbg_params": null, "active": true, "vnic_type": "normal", "profile": {}, "preserve_on_delete": false, "meta": {}} nova_to_osvif_vif /var/lib/kolla/venv/lib/python3.6/site-packages/nova/network/os_vif_util.py:501

10.120.29.129 更神奇的是这个ip竟然还是通的，这个ip恰好是mysql三节点的主节点（没做高可用），导致无法直接回收该接口。

由于compute频繁奔溃，导致其他节点的卷无法被挂载。 从而导致其他业务也无法恢复。