Waldo

Detect external Internet IP address changes from any machine, and update a DNS entry in a Google Cloud DNS Managed Zone with that new IP address.

Problem Statement

I moved from having a static IPv4 public IP address on my home Internet connection, to having a dynamic IPv4 address. How was I going to be able to figure out the IP address to SSH into if it could possibly change?

There must be a way to detect if has changed, and update my DNS records accordingly.

Run Locally

1. Configure Application Default Credentials for your Google Cloud Project.
2. Download the resulting JSON file to your local machine.
3. Determine a DNS entry that will be updated in the managed zone.
4. Run binary.

go run waldo.go --credentialsPath adc.json --managedZone $ZONEFROMCLOUDDNS --project $PROJECTNAME --recordName fqdn.to.keep.updated.tld

Run On Kubernetes

First, you need to create a secret containing your service account credentials.

kubectl create secret generic waldo-creds --from-file=waldo-creds.json

Edit waldo-deployment.yaml to contain your zone name, record name. etc.

Then create the deployment.

kubectl apply -f waldo-deployment.yaml

Command Line Flags

-credentialsPath string
  Path to JSON credentials file for updating DNS.
-managedZone string
  Zone name in Google Cloud DNS.
-project string
  Project name within Google Cloud associated with Managed Zone.
-recordName string
  DNS Host Resource Record to Update in Cloud DNS.
-recordType string
  RR Datatype for the DNS record. (default "A")
-recordttl int
  TTL (minutes) for the DNS record TTL (default 60)
-waitDuration duration
  Interval in seconds to check public IP address. (default 5m0s)

Future plans when time permits.

• Dry run support for Record Adds and Deletes.
• Handle both IPv4 and IPv6.
• Notification Upon IP Change: Slack, Email, IRC, SMS

References Used in Development

• https://godoc.org/golang.org/x/oauth2/google
• https://cloud.google.com/dns/api/v1/changes/create
• https://github.com/kelseyhightower/dns01-exec-plugins/blob/master/googledns/client.go