feat(nlb): add eip auto selection support for nlb

docs/guide/service/annotations.md

@@ -174,6 +174,21 @@ on the load balancer.
         service.beta.kubernetes.io/aws-load-balancer-eip-allocations: eipalloc-xyz, eipalloc-zzz
         ```
 
+- <a name="eip-tags">`service.beta.kubernetes.io/aws-load-balancer-eip-tags`</a> specifies a set of AWS tags to dynamically select unassociated Elastic IPs for an internet-facing NLB.
+
+    !!!note
+        - This configuration is optional, and you can use it to assign static IP addresses to your NLB by tag selection.
+        - You must specify tags in the format `key1=value1,key2=value2`.
+        - The controller will select unassociated EIPs matching all tags and assign them to the NLB subnets.
+        - NLB must be internet-facing.
+        - You must tag your EIPs in AWS before using this annotation.
+        - The number of matching, unassociated EIPs must be at least the number of subnets.
+
+    !!!example
+        ```
+        service.beta.kubernetes.io/aws-load-balancer-eip-tags: k8s-cluster=my-prod-cluster,purpose=ingress-nlb
+        ```
+
 
 - <a name="private-ipv4-addresses">`service.beta.kubernetes.io/aws-load-balancer-private-ipv4-addresses`</a> specifies a list of private IPv4 addresses for an internal NLB.
 

pkg/annotations/constants.go

@@ -105,6 +105,7 @@ const (
 	SvcLBSuffixTargetGroupAttributes                     = "aws-load-balancer-target-group-attributes"
 	SvcLBSuffixSubnets                                   = "aws-load-balancer-subnets"
 	SvcLBSuffixEIPAllocations                            = "aws-load-balancer-eip-allocations"
+	SvcLBSuffixEIPTags                                   = "aws-load-balancer-eip-tags"
 	SvcLBSuffixPrivateIpv4Addresses                      = "aws-load-balancer-private-ipv4-addresses"
 	SvcLBSuffixIpv6Addresses                             = "aws-load-balancer-ipv6-addresses"
 	SvcLBSuffixALPNPolicy                                = "aws-load-balancer-alpn-policy"

pkg/aws/services/ec2.go

@@ -37,6 +37,9 @@ type EC2 interface {
 	DescribeAvailabilityZonesWithContext(ctx context.Context, input *ec2.DescribeAvailabilityZonesInput) (*ec2.DescribeAvailabilityZonesOutput, error)
 	DescribeVpcsWithContext(ctx context.Context, input *ec2.DescribeVpcsInput) (*ec2.DescribeVpcsOutput, error)
 	DescribeInstancesWithContext(ctx context.Context, input *ec2.DescribeInstancesInput) (*ec2.DescribeInstancesOutput, error)
+
+	// DescribeAddressesAsList wraps the DescribeAddresses API, aggregates results into a list.
+	DescribeAddressesAsList(ctx context.Context, input *ec2.DescribeAddressesInput) ([]types.Address, error)
 }
 
 // NewEC2 constructs new EC2 implementation.
@@ -50,6 +53,18 @@ type ec2Client struct {
 	awsClientsProvider provider.AWSClientsProvider
 }
 
+func (c *ec2Client) DescribeAddressesAsList(ctx context.Context, input *ec2.DescribeAddressesInput) ([]types.Address, error) {
+	client, err := c.awsClientsProvider.GetEC2Client(ctx, "DescribeAddresses")
+	if err != nil {
+		return nil, err
+	}
+	output, err := client.DescribeAddresses(ctx, input)
+	if err != nil {
+		return nil, err
+	}
+	return output.Addresses, nil
+}
+
 func (c *ec2Client) DescribeInstancesWithContext(ctx context.Context, input *ec2.DescribeInstancesInput) (*ec2.DescribeInstancesOutput, error) {
 	client, err := c.awsClientsProvider.GetEC2Client(ctx, "DescribeInstances")
 	if err != nil {

pkg/service/model_build_load_balancer.go

@@ -10,6 +10,8 @@ import (
 	"sort"
 	"strconv"
 
+	"github.com/aws/aws-sdk-go-v2/service/ec2"
+
 	awssdk "github.com/aws/aws-sdk-go-v2/aws"
 	ec2types "github.com/aws/aws-sdk-go-v2/service/ec2/types"
 	"github.com/pkg/errors"
@@ -335,13 +337,60 @@ func (t *defaultModelBuildTask) buildLoadBalancerTags(ctx context.Context) (map[
 func (t *defaultModelBuildTask) buildLoadBalancerSubnetMappings(_ context.Context, ipAddressType elbv2model.IPAddressType, scheme elbv2model.LoadBalancerScheme, ec2Subnets []ec2types.Subnet, enablePrefixForIpv6SourceNat elbv2model.EnablePrefixForIpv6SourceNat) ([]elbv2model.SubnetMapping, error) {
 	var eipAllocation []string
 	eipConfigured := t.annotationParser.ParseStringSliceAnnotation(annotations.SvcLBSuffixEIPAllocations, &eipAllocation, t.service.Annotations)
+	var eipTags string
+	eipTagsConfigured := t.annotationParser.ParseStringAnnotation(annotations.SvcLBSuffixEIPTags, &eipTags, t.service.Annotations)
 	if eipConfigured {
 		if scheme != elbv2model.LoadBalancerSchemeInternetFacing {
 			return nil, errors.Errorf("EIP allocations can only be set for internet facing load balancers")
 		}
 		if len(eipAllocation) != len(ec2Subnets) {
 			return nil, errors.Errorf("count of EIP allocations (%d) and subnets (%d) must match", len(eipAllocation), len(ec2Subnets))
 		}
+	} else if eipTagsConfigured {
+		if scheme != elbv2model.LoadBalancerSchemeInternetFacing {
+			return nil, errors.Errorf("EIP tags can only be set for internet facing load balancers")
+		}
+		// Parse tags string into map
+		tagMap := make(map[string]string)
+		for _, kv := range regexp.MustCompile(`,`).Split(eipTags, -1) {
+			parts := regexp.MustCompile(`=`).Split(kv, 2)
+			if len(parts) == 2 {
+				tagMap[parts[0]] = parts[1]
+			}
+		}
+		// Build EC2 filter for DescribeAddresses
+		var filters []ec2types.Filter
+		for k, v := range tagMap {
+			filters = append(filters, ec2types.Filter{
+				Name:   awssdk.String(fmt.Sprintf("tag:%s", k)),
+				Values: []string{v},
+			})
+		}
+		filters = append(filters, ec2types.Filter{
+			Name:   awssdk.String("domain"),
+			Values: []string{"vpc"},
+		})
+		addresses, err := t.ec2Client.DescribeAddressesAsList(context.Background(), &ec2.DescribeAddressesInput{
+			Filters: filters,
+		})
+		if err != nil {
+			return nil, errors.Wrap(err, "failed to describe EIPs by tags")
+		}
+		// Filter unassociated EIPs client-side
+		var unassociatedAddresses []ec2types.Address
+		for _, addr := range addresses {
+			if addr.AssociationId == nil || awssdk.ToString(addr.AssociationId) == "" {
+				unassociatedAddresses = append(unassociatedAddresses, addr)
+			}
+		}
+		if len(unassociatedAddresses) < len(ec2Subnets) {
+			return nil, errors.Errorf("not enough unassociated EIPs with specified tags; needed %d, found %d", len(ec2Subnets), len(unassociatedAddresses))
+		}
+		eipAllocation = make([]string, len(ec2Subnets))
+		for i := range ec2Subnets {
+			eipAllocation[i] = awssdk.ToString(unassociatedAddresses[i].AllocationId)
+		}
+		eipConfigured = true
 	}
 
 	var ipv4Addresses []netip.Addr