DNS service not working for System VMs on a fresh new install Cloudstack

##### ISSUE TYPE

* Other

##### COMPONENT NAME

~~~
UI, System VMs
~~~

##### CLOUDSTACK VERSION

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CloudStack 4.18
~~~

##### CONFIGURATION

Zone with default Advanced networking with Isolation method as VLAN
Zone has only one "Physical Network 1" with all traffic types Guest, Management, Public, Storage passing through it
KVM
Management Server and KVM Host are same. Its a testing environment
OpenVswitch and DPDK enabled and created bridge interface using OpenVswitch commands
Primany and Secondary with NFS mount points

##### OS / ENVIRONMENT

Ubuntu 22.04.2 LTS
Codename: jammy

##### SUMMARY

The System VMs Agent state is not Up

##### STEPS TO REPRODUCE

~~~
Install a fresh new Ubuntu 22.04 LTS server
Enable OpenVswitch and dpdk over the interface and create bridge interface
Perform the install of cloudstack on a server. Also make this server as KVM Host.
Configure Cloudstack as zone with default advanced networking
Zone has only one "Physical Network 1" with all traffic types Guest, Management, Public, Storage
passing through it
~~~

##### EXPECTED RESULTS

~~~
The System VMs Agent state is OK
~~~

##### ACTUAL RESULTS

~~~
After the Cloudstack install and basic configuration of zone,

Go system vms section, we notice the state is "running" but the Agent state is not "OK"

Accessed one of the system vm using commands like ssh -i /root/.ssh/id_rsa.cloud -p 3922 root@link-local

Issued command /usr/local/cloud/systemvm/ssvm-check.sh

Noticed error ERROR: DNS not resolving cloudstack.apache.org

Confirmed Google DNS server is there at resolv.conf

Checked the service cloud status and noticed the system vm can't communicate with port 8250 of management server
over the management server IP

Further troubleshooting shows from inside system vm, only able to ping management server IP
but no connection with any active ports of management server like ssh port , management ports like 8250 etc

While checking the traffic over the bridge interface using ovs-tcpdump , we have noticed the
incoming traffic from system vms towards bridge interface are reaching but no outgoing response
towards system vms. Below is a sample captured traffic at bridge interface over
cloudstack port number 8250. We believe that we setup the openvswitch dpdk setup correctly
and not sure what we are missing from our side.

12:08:52.312394 IP SVMIP.33940 > MGMTIP.8250: Flags [S], seq 3467199111, win 64240, options [mss 1460,nop,nop,sackOK,nop,wscale 7], length 0
<.............E..4\.@.@.....?...?... :..B.........................
12:08:53.314315 IP SVMIP.33940 > MGMTIP..8250: Flags [S], seq 3467199111, win 64240, options [mss 1460,nop,nop,sackOK,nop,wscale 7], length 0

issued the command "ovs-ofctl dump-flows cloudbr0" and got below result. Looks like the rule is fine

cookie=0x0, duration=148279.131s, table=0, n_packets=7453119, n_bytes=2575374706, priority=0 actions=NORMAL

Not sure what we are missing.

~~~

从 System VM 入口 `ssvm-check.sh` 开始，在所述的 Ubuntu 22.04、KVM 和 Open vSwitch 设置中复现所描述的 DNS 和管理服务器端口 8250 故障。检查 `cloudbr0` 的流量和连接路径；完成的标准是 System VM agent 状态为 OK、DNS 能够解析，并且与管理服务器的连接能够收到响应。

由索引模型根据 Issue 内容生成。