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Instance lookup by IP and hostname via private IP addresses on attach…
…ed NIC (#54) * Merges Attribute and Tag filters for defining matchers for non-tag values * Adds an --attribute flag to session calls
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Nate Catelli
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Sep 24, 2021
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,73 @@ | ||
| package resolver | ||
|
|
||
| import ( | ||
| "fmt" | ||
| "net" | ||
|
|
||
| "github.com/aws/aws-sdk-go/service/ec2" | ||
| "github.com/aws/aws-sdk-go/service/ec2/ec2iface" | ||
| ) | ||
|
|
||
| // Provides a interface for resolving an instance to a single ec2 instance. | ||
| type InstanceResolver interface { | ||
| ResolveToInstanceId(client ec2iface.EC2API) ([]string, error) | ||
| } | ||
|
|
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| /// HostnameResolver attempts to resolve a fqdn or IP to a corresponding instance ID. | ||
| type HostnameResolver struct { | ||
| addrs []string | ||
| } | ||
|
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| func NewHostnameResolver(addrs []string) *HostnameResolver { | ||
| return &HostnameResolver{ | ||
| addrs: addrs, | ||
| } | ||
| } | ||
|
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| func (hr *HostnameResolver) ResolveToInstanceId(client ec2iface.EC2API) (output []string, err error) { | ||
| ips := make([]*string, 1) | ||
| for _, addr := range hr.addrs { | ||
| ip, err := resolveToFirst(addr) | ||
| if err != nil { | ||
| return nil, fmt.Errorf("unable to resolve hostname to %v to ip", hr.addrs) | ||
| } | ||
|
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| ipString := ip.String() | ||
| ips = append(ips, &ipString) | ||
|
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| } | ||
|
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| ipFilter := &ec2.Filter{} | ||
| ipFilter.SetName("addresses.private-ip-address").SetValues(ips) | ||
|
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| dniInput := &ec2.DescribeNetworkInterfacesInput{} | ||
| dniInput.SetFilters([]*ec2.Filter{ipFilter}) | ||
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| describeNetworkInterfacesPager := func(page *ec2.DescribeNetworkInterfacesOutput, lastPage bool) bool { | ||
| for _, nic := range page.NetworkInterfaces { | ||
| output = append(output, *nic.Attachment.InstanceId) | ||
| } | ||
|
|
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| // If it's not the last page, continue | ||
| return !lastPage | ||
| } | ||
|
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| // Fetch all the instances described | ||
| if err = client.DescribeNetworkInterfacesPages(dniInput, describeNetworkInterfacesPager); err != nil { | ||
| return nil, fmt.Errorf("could not describe network interfaces\n%v", err) | ||
| } | ||
|
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| return output, nil | ||
| } | ||
|
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| func resolveToFirst(addr string) (net.IP, error) { | ||
| if ip := net.ParseIP(addr); ip != nil { | ||
| return ip, nil | ||
| } else if ips, err := net.LookupIP(addr); err == nil { | ||
| if len(ips[0]) > 0 { | ||
| return ips[0], nil | ||
| } | ||
| } | ||
|
|
||
| return nil, fmt.Errorf("no IP address found for %s", addr) | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,73 @@ | ||
| package resolver | ||
|
|
||
| import ( | ||
| "io/ioutil" | ||
| "net" | ||
| "testing" | ||
|
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| "github.com/aws/aws-sdk-go/service/ec2" | ||
| "github.com/aws/aws-sdk-go/service/ec2/ec2iface" | ||
| "github.com/sirupsen/logrus" | ||
| "github.com/stretchr/testify/assert" | ||
| ) | ||
|
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| type mockedEC2 struct { | ||
| ec2iface.EC2API | ||
| DescribeNetworkInterfacesOutput []*ec2.DescribeNetworkInterfacesOutput | ||
| } | ||
|
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| func (c *mockedEC2) DescribeNetworkInterfacesPages(input *ec2.DescribeNetworkInterfacesInput, fn func(*ec2.DescribeNetworkInterfacesOutput, bool) bool) error { | ||
| totalPages := len(c.DescribeNetworkInterfacesOutput) | ||
| for i, output := range c.DescribeNetworkInterfacesOutput { | ||
| isLastPage := (i == (totalPages - 1)) | ||
| if breakLoop := fn(output, isLastPage); breakLoop { | ||
| break | ||
| } | ||
| } | ||
| return nil | ||
| } | ||
|
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||
| var ( | ||
| exampleInstanceId = "i-1234567890abcdef0" | ||
| examplePrivateIpAddress = "127.0.0.1" | ||
| singleResponseDescribeNetworkInterfacesOutput = ec2.DescribeNetworkInterfacesOutput{ | ||
| NetworkInterfaces: []*ec2.NetworkInterface{ | ||
| { | ||
| Attachment: &ec2.NetworkInterfaceAttachment{ | ||
| InstanceId: &exampleInstanceId, | ||
| }, | ||
| PrivateIpAddress: &examplePrivateIpAddress, | ||
| }, | ||
| }, | ||
| NextToken: nil, | ||
| } | ||
| ) | ||
|
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| func TestHostnameResolver(t *testing.T) { | ||
| assert := assert.New(t) | ||
|
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| logger := logrus.New() | ||
| logger.SetOutput(ioutil.Discard) | ||
|
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| t.Run("test passed ip causes a short circuit", func(t *testing.T) { | ||
| validIp, err := resolveToFirst(examplePrivateIpAddress) | ||
| assert.Nil(err) | ||
| assert.NotNil(validIp) | ||
| assert.EqualValues(validIp, net.ParseIP(examplePrivateIpAddress)) | ||
| }) | ||
|
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| t.Run("test passed passed hostname resolves to an IP", func(t *testing.T) { | ||
| validIp, err := resolveToFirst("example.com") | ||
| assert.Nil(err) | ||
| assert.NotNil(validIp) | ||
| }) | ||
|
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| t.Run("test mock resolver returns a valid instance id", func(t *testing.T) { | ||
| mockClient := &mockedEC2{DescribeNetworkInterfacesOutput: []*ec2.DescribeNetworkInterfacesOutput{&singleResponseDescribeNetworkInterfacesOutput}} | ||
| testResolver := NewHostnameResolver([]string{examplePrivateIpAddress}) | ||
|
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| resp, err := testResolver.ResolveToInstanceId(mockClient) | ||
| assert.Nil(err) | ||
| assert.EqualValues(resp, []string{exampleInstanceId}) | ||
| }) | ||
| } |
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