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Query IMDS over IPv6 if no IPv4 interface address #2453

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merged 1 commit into from
Oct 1, 2022
Merged

Query IMDS over IPv6 if no IPv4 interface address #2453

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33 changes: 30 additions & 3 deletions pkg/aws/cloud.go
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Original file line number Diff line number Diff line change
@@ -1,12 +1,15 @@
package aws

import (
"net"
"os"
"strings"

"github.com/aws/aws-sdk-go/aws"
"github.com/aws/aws-sdk-go/aws/endpoints"
"github.com/aws/aws-sdk-go/aws/session"
"github.com/pkg/errors"
"github.com/prometheus/client_golang/prometheus"
"os"
epresolver "sigs.k8s.io/aws-load-balancer-controller/pkg/aws/endpoints"
"sigs.k8s.io/aws-load-balancer-controller/pkg/aws/metrics"
"sigs.k8s.io/aws-load-balancer-controller/pkg/aws/services"
Expand Down Expand Up @@ -44,9 +47,28 @@ type Cloud interface {

// NewCloud constructs new Cloud implementation.
func NewCloud(cfg CloudConfig, metricsRegisterer prometheus.Registerer) (Cloud, error) {
hasIPv4 := true
addrs, err := net.InterfaceAddrs()
if err == nil {
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in case of error, why not return right away?
Are there situations where the net.InterfaceAddrs() return error, but we still want to continue processing?

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The idea was to avoid any negative effects in existing cases. So if the process doesn't have permission to enumerate the interfaces, it would assume IPv4.

hasIPv4 = false
for _, addr := range addrs {
str := addr.String()
if !strings.HasPrefix(str, "127.") && !strings.Contains(str, ":") {
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i think this check is a bit hacky.
maybe just upgrade the sdk and let users specify AWS_EC2_METADATA_SERVICE_ENDPOINT_MODE env variable via helm chart?

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Why should users have to specify AWS_EC2_METADATA_SERVICE_ENDPOINT_MODE at all?

hasIPv4 = true
break
}
}
}

endpointsResolver := epresolver.NewResolver(cfg.AWSEndpoints)
metadataCFG := aws.NewConfig().WithEndpointResolver(endpointsResolver)
metadataSess := session.Must(session.NewSession(metadataCFG))
opts := session.Options{}
opts.Config.MergeIn(metadataCFG)
if !hasIPv4 {
opts.EC2IMDSEndpointMode = endpoints.EC2IMDSEndpointModeStateIPv6
}

metadataSess := session.Must(session.NewSessionWithOptions(opts))
metadata := services.NewEC2Metadata(metadataSess)
if len(cfg.VpcID) == 0 {
vpcId, err := metadata.VpcID()
Expand All @@ -72,7 +94,12 @@ func NewCloud(cfg CloudConfig, metricsRegisterer prometheus.Registerer) (Cloud,
cfg.Region = region
}
awsCFG := aws.NewConfig().WithRegion(cfg.Region).WithSTSRegionalEndpoint(endpoints.RegionalSTSEndpoint).WithMaxRetries(cfg.MaxRetries).WithEndpointResolver(endpointsResolver)
sess := session.Must(session.NewSession(awsCFG))
opts = session.Options{}
opts.Config.MergeIn(awsCFG)
if !hasIPv4 {
opts.EC2IMDSEndpointMode = endpoints.EC2IMDSEndpointModeStateIPv6
}
sess := session.Must(session.NewSessionWithOptions(opts))
injectUserAgent(&sess.Handlers)

if cfg.ThrottleConfig != nil {
Expand Down