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cloud-floating-ip

Implement a floating/virtual IP by configuring cloud provider's routes.

Choose an arbitrary private IP address, and cloud-floating-ip will configure route for that IP to the AWS or GCP instance of your choice.

Instances preparation

To choose a virtual IP: this address must be available, and not used elsewhere in the VPC; it doesn't have to be part of an existing subnet range.

All EC2/GCE instances that may become "primary" (carry the floating IP) at some point should be allowed by the cloud provider to route traffic: SourceDestCheck (EC2) or canIpForward (GCE) must be enabled.

Those instances should be able to accept traffic to the floating IP. To that effect, we can assign the virtual IP address to a loopback or a dummy interface on all instances:

# we can do that on all instances
ip link add dummy0 type dummy
ip address add 10.200.0.50/32 dev dummy0
ip link set dev dummy0 up

This can be persisted in network configurations (eg. in /etc/network/interfaces or /etc/sysconfig/network-scripts/).

Usage

To route the floating IP to the current instance:

# see what would change
cloud-floating-ip -i 10.200.0.50 preempt --dry-run

# apply the changes
cloud-floating-ip -i 10.200.0.50 preempt

The IP can be preempted by other instances in the VPC, by using the same preempt command.

To verify the status ("primary" or "standby") of any instance:

cloud-floating-ip -i 10.200.0.50 status

When cloud-floating-ip runs on the target instance, most settings (region, instance id, cloud provider, ...) can be guessed from the instance metadata. To act on a remote instance, we must be more explicit (or use a configuration file). Eg:

cloud-floating-ip -o aws -i 10.200.0.50 -t i-0e3f4ac17545ce580 -r eu-west-1 status
cloud-floating-ip -o aws -i 10.200.0.50 -t i-0e3f4ac17545ce580 -r eu-west-1 preempt

cloud-floating-ip -o gce -i 10.200.0.50 -p my-gcp-project \
  -t my-gce-instance -z europe-west1-b status

To store the configuration (and save repetitive -i ... arguments):

cat<<EOF > /etc/cloud-floating-ip.yaml
ip: 10.200.0.50
quiet: true
EOF

Multihomed instances

When the instance has only one interface attached to the VPC, cloud-floating-ip will find and use this interface automatically.

If the instance has more than one external interfaces (and/or networks), we need one of the following options to choose the target interface we'll route traffic to:

Provide either:

  • --interface : the target interface name (ie. eni-xxxx on AWS, nicX on GCE)
  • --subnet : the target network interface's subnet name
  • --target-ip : the target network interface's private IP

Options

The ip argument is mandatory. Other settings can be collected from instance's metadata when running cloud-floating-ip from an AWS or GCE instance.

Those settings can be stored in the /etc/cloud-floating-ip.yaml configuration file. You can also pass them through environments (upper case, prefixed by CFI_).

Usage:
  cloud-floating-ip [flags]
  cloud-floating-ip [command]

Available Commands:
  destroy     Delete the routes managed by cloud-floating-ip
  help        Help about any command
  preempt     Preempt an IP address and route it to the instance
  status      Display the status of the instance (owner or standby)

Flags:
  -c, --config string              config file (default is /etc/cloud-floating-ip.yaml)
  -i, --ip string                  IP address
  -d, --dry-run                    dry-run mode
  -q, --quiet                      quiet mode
  -h, --help                       help for cloud-floating-ip
  -o, --hoster string              hosting provider (aws or gce)
  -t, --instance string            instance name
  -f, --interface string           network interface ID
  -s, --subnet string              subnet ID
  -g, --target-ip string           target private IP
  -m, --ignore-main-table          (AWS) ignore routes in main table
  -a, --aws-access-key-id string   (AWS) access key Id
  -k, --aws-secret-key string      (AWS) secret key
  -r, --region string              (AWS) region name
  -b, --table strings              (AWS) only consider this route table (may be specified several times)
  -p, --project string             (GCP) project id
  -z, --zone string                (GCP) zone name

Required privileges

On EC2, the account running cloud-floating-ip must have the following rights:

ec2:DescribeInstances
ec2:DescribeRouteTables
ec2:CreateRoute
ec2:ReplaceRoute
ec2:DeleteRoute

On GCE:

compute.instances.get
compute.routes.get
compute.routes.create
compute.routes.delete
container.operations.get
container.operations.list

Limitations

  • On GCE, cloud-floating-ip won't delete already created, pre-existing routes with a distinct custom name
  • IPv4 only, for now