honor config.NetworkInterface in NodeNetworks

[notnoop]

Fixes #8445 .

Nomad 0.12 introduces NodeNetworks structs in #8208 but it looks like it may be out of sync from earlier network interpretation, namely, .NodeResources.Networks. NodeResources.Networks honors network_interface from config, but looks like .NodeResources.Networks uses the "default" network (as specified by ip route). This mis-attribution result into pods getting assigned unexpected ip addresses.

It's notable that NodeResources aren't reported when using nomad node status -json - we must use curl.

To test this, I had a simple nomad agent with network_interface = "eth2" config. Notice how NodeNetworks and Networks report different interface names before, and with the fix both point to eth2.

The command:

curl -sSL localhost:4646/v1/node/$(nomad node status -self -json | jq -r .ID) | jq '{NodeNetworks: .NodeResources.NodeNetworks, Networks: .NodeResources.Networks}

Before

{
  "NodeNetworks": [
    {
      "Mode": "bridge",
      "Device": "",
      "MacAddress": "",
      "Speed": 0,
      "Addresses": null
    },
    {
      "Mode": "host",
      "Device": "eth0",
      "MacAddress": "08:00:27:81:14:5e",
      "Speed": 1000,
      "Addresses": [
        {
          "Family": "ipv4",
          "Alias": "default",
          "Address": "10.0.2.15",
          "ReservedPorts": "",
          "Gateway": ""
        }
      ]
    }
  ],
  "Networks": [
    {
      "Mode": "bridge",
      "Device": "",
      "CIDR": "",
      "IP": "",
      "MBits": 0,
      "DNS": null,
      "ReservedPorts": null,
      "DynamicPorts": null
    },
    {
      "Mode": "host",
      "Device": "eth2",
      "CIDR": "10.199.0.200/32",
      "IP": "10.199.0.200",
      "MBits": 1000,
      "DNS": null,
      "ReservedPorts": null,
      "DynamicPorts": null
    }
  ]
}

After

{
  "NodeNetworks": [
    {
      "Addresses": null,
      "Device": "",
      "MacAddress": "",
      "Mode": "bridge",
      "Speed": 0
    },
    {
      "Addresses": [
        {
          "Address": "10.199.0.200",
          "Alias": "default",
          "Family": "ipv4",
          "Gateway": "",
          "ReservedPorts": ""
        }
      ],
      "Device": "eth2",
      "MacAddress": "08:00:27:7c:5f:ec",
      "Mode": "host",
      "Speed": 1000
    }
  ],
  "Networks": [
    {
      "CIDR": "",
      "DNS": null,
      "Device": "",
      "DynamicPorts": null,
      "IP": "",
      "MBits": 0,
      "Mode": "bridge",
      "ReservedPorts": null
    },
    {
      "CIDR": "10.199.0.200/32",
      "DNS": null,
      "Device": "eth2",
      "DynamicPorts": null,
      "IP": "10.199.0.200",
      "MBits": 1000,
      "Mode": "host",
      "ReservedPorts": null
    }
  ]
}

[schmichael]

Thanks for jumping on this!

[nickethier]

👍 Thanks for getting this!

[github-actions]

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