This page explains how to use network policy logging for Google Kubernetes Engine (GKE). Kubernetes network policies specify network traffic that Pods are allowed to send and receive. Network policy logging lets you record when a connection is allowed or denied by a network policy. Network policy logging can help you troubleshoot issues with network policies.
Overview
Using network policy logging, you can:
- Verify that your network policies are working as expected.
- Understand which Pods in your cluster are communicating with the internet.
- Understand which namespaces are communicating with each other.
- Recognize a Denial of Service attack.
Network policy logs are uploaded to Cloud Logging for storage, search, analysis, and alerting if Cloud Logging is enabled. Cloud Logging is enabled by default in new clusters. See Configuring logging and monitoring for GKE for more.
Requirements
- Network policy logging is only available for clusters that use GKE Dataplane V2.
- Network policy logging requires the Google Cloud CLI 303.0.0 or higher.
- Network policy logging is not supported with Windows Server node pools.
Pricing
- There are no log generation charges for network policy logging.
- If you store your logs in Cloud Logging, standard Cloud Logging charges apply.
- Logs can be further routed to Pub/Sub, Cloud Storage, or BigQuery. Pub/Sub, Cloud Storage, or BigQuery charges may apply. For more information, see Routing and storage overview.
Configuring network policy logging
You configure network policy logging settings by editing the NetworkLogging
object in your cluster. GKE automatically creates a
NetworkLogging
object named default
in new Dataplane V2
clusters. There can only be one
NetworkLogging object per cluster and it can't be renamed.
You can configure the logging of allowed connections and the logging of denied
connections separately. You can also selectively enable logging for some network
policies. The following is an example of the NetworkLogging
specification, with settings
specified to log all allowed and denied connections:
kind: NetworkLogging
apiVersion: networking.gke.io/v1alpha1
metadata:
name: default
spec:
cluster:
allow:
log: true
delegate: false
deny:
log: true
delegate: false
Use kubectl
to edit your configuration:
kubectl edit networklogging default
NetworkLogging spec
The NetworkLogging object specification is in a YAML format. This format is described in the following table:
Field | Type | Description | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
cluster.allow | struct |
Settings for logging allowed connections.
|
|||||||||
cluster.deny |
struct |
Settings for logging denied connections.
|
Accessing network policy logs
Network policy logs are automatically uploaded to Cloud Logging. You can access logs through the Logs Explorer or with the Google Cloud CLI. You can also route logs to a sink.
Cloud Logging
Go to the Logs Explorer page in the Google Cloud console.
Click Query builder.
Use the following query to find all network policy log records:
resource.type="k8s_node" resource.labels.location="CLUSTER_LOCATION" resource.labels.cluster_name="CLUSTER_NAME" logName="projects/PROJECT_NAME/logs/policy-action"
Replace the following:
CLUSTER_LOCATION
: The Compute Engine location of the cluster.CLUSTER_NAME
: The name of your cluster.PROJECT_NAME
: The name of your Google Cloud project.
See Using the Logs Explorer to learn how to use the Logs Explorer.
You can also build a query using the Query builder. To create a query for network policy logs, select policy-action in the Log name drop-down list. If there are no available logs, policy-action does not appear in the drop-down list.
gcloud
Find all network policy log records:
gcloud logging read --project "PROJECT_NAME" 'resource.type="k8s_node"
resource.labels.location="CLUSTER_LOCATION"
resource.labels.cluster_name="CLUSTER_NAME"
logName="projects/PROJECT_NAME/logs/policy-action"'
Replace the following:
PROJECT_NAME
: The name of your Google Cloud project.CLUSTER_LOCATION
: The Compute Engine location of the cluster.CLUSTER_NAME
: The name of your cluster.
You can add further conditions to filter the results. For example:
Show logs in a certain timeframe:
timestamp>="2020-06-22T06:30:51.128Z" timestamp<="2020-06-23T06:30:51.128Z"
Show logs for denied connections:
jsonPayload.disposition="deny"
Show logs to a deployment named "redis":
jsonPayload.dest.pod_name=~"redis" jsonPayload.dest.pod_namespace="default"
Show logs for cluster-external connections:
jsonPayload.dest.instance != ""
Show logs that match a certain network policy, in this case "allow-frontend-to-db":
jsonPayload.policies.name="allow-frontend-to-db" jsonPayload.policies.namespace="default"
If you use a Standard cluster, you can also find the network policy
logs generated on each cluster node locally at
/var/log/network/policy_action.log*
. A new numbered log file is created when
the current log file reaches 10 MB. Up to five previous log files are stored.
Network policy log format
Network policy log records are in a JSON format. This format is described in the following table:
Field | Type | Description | |||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
connection | struct |
Connection information:
|
|||||||||||||||||||||
src | struct |
Endpoint information of the source:
|
|||||||||||||||||||||
dest | struct |
Endpoint information of the destination:
|
|||||||||||||||||||||
disposition | string | Disposition of the connection, which can be allow or deny . | |||||||||||||||||||||
policies | list of structs |
Matched policies for the allowed connections from the enforced Pod's view. For ingress connection, the enforced Pod is the destination Pod. For egress connection, the enforced Pod is the source Pod. Multiple policies are logged if a connection is matched by all of them. This field is only included in logs of allowed connections.
|
|||||||||||||||||||||
count | int | Used for log aggregation of denied queries. The value is always 1 for allowed connection. | |||||||||||||||||||||
node_name | string | The node that runs the Pod that generated this log message. | |||||||||||||||||||||
timestamp | string | When the connection attempt occurred. |
Definition of connection
For connection-oriented protocols like TCP, a log is created for each allowed or denied connection. For protocols like UDP and ICMP that aren't connection-oriented, packets are grouped into time-window based connections.
Policy logs for denied connections
The log records for denied connections don't include the policies
field
because the Kubernetes network policy API does not have explicit deny policies.
A connection is denied if a Pod is covered by one or more network policies, but
none of the policies allow the connection. This means that no policy is
individually responsible for a blocked connection.
Log aggregation for denied connections
It is common for a client to retry a connection that was denied. To prevent
excessive logging, repeated denied connections within a five-second window are
aggregated into a single log message using the count
field.
Subsequent denied connections are aggregated with a previous log message if the
connection's src_ip, dest_ip, dest_port, protocol,
and direction
match the
first denied connection. Note that the src_port
of subsequent connections does
not have to match because retried connections might come from a different port.
The aggregated log message includes the src_prt
of the first denied connection
at the beginning of the aggregation window.
Example log records
The following example network policy named allow-green
applied to
test-service
allows connections to test-service
from a Pod named
client-green
. Implicitly, this policy denies all other ingress traffic to
test-service
including from the Pod client-red
.
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
name: allow-green
namespace: default
annotations:
policy.network.gke.io/enable-logging: "true"
spec:
podSelector:
matchLabels:
app: test-service
ingress:
- from:
- podSelector:
matchLabels:
app: client-green
policyTypes:
- Ingress
This diagram shows the effect of the allow-green
policy on two connections to
test-service
. The allow-green
policy allows the connection from
client-green
. Because no policy allows the connection from client-red
the
connection is denied.
The log for the allowed connection from client-green
looks like this:
{
"connection":{
"src_ip":"10.84.0.252",
"dest_ip":"10.84.0.165",
"src_port":52648,
"dest_port":8080,
"protocol":"tcp",
"direction":"ingress"
},
"disposition":"allow",
"policies":[
{
"name":"allow-green",
"namespace":"default"
}
],
"src":{
"pod_name":"client-green-7b78d7c957-68mv4",
"pod_namespace":"default",
"namespace":"default",
"workload_name":"client-green-7b78d7c957",
"workload_kind":"ReplicaSet"
},
"dest":{
"pod_name":"test-service-745c798fc9-sfd9h",
"pod_namespace":"default",
"namespace":"default",
"workload_name":"test-service-745c798fc9",
"workload_kind":"ReplicaSet"
},
"count":1,
"node_name":"gke-demo-default-pool-5dad52ed-k0h1",
"timestamp":"2020-06-16T03:10:37.993712906Z"
}
The log for the denied connection from client-red
looks like this:
{
"connection":{
"src_ip":"10.84.0.180",
"dest_ip":"10.84.0.165",
"src_port":39610,
"dest_port":8080,
"protocol":"tcp",
"direction":"ingress"
},
"disposition":"deny",
"src":{
"pod_name":"client-red-5689846f5b-b5ccx",
"pod_namespace":"default",
"namespace":"default",
"workload_name":"client-red-5689846f5b",
"workload_kind":"ReplicaSet"
},
"dest":{
"pod_name":"test-service-745c798fc9-sfd9h",
"pod_namespace":"default",
"namespace":"default",
"workload_name":"test-service-745c798fc9",
"workload_kind":"ReplicaSet"
},
"count":3,
"node_name":"gke-demo-default-pool-5dad52ed-k0h1",
"timestamp":"2020-06-15T22:38:32.189649531Z"
}
Note that the denied connection log does not include the policies
field. This
is described in the preceding section,
Policy logs for denied connections.
The denied connection log includes a count
field for
aggregating denied connections.
Troubleshooting issues with network policy logs
Check for error events in the
NetworkLogging
object:kubectl describe networklogging default
If the logging configuration is invalid, the configuration won't take effect and an error will be reported in the events section:
Name: default Namespace: Labels: addonmanager.kubernetes.io/mode=EnsureExists Annotations: API Version: networking.gke.io/v1alpha1 Kind: NetworkLogging Metadata: Creation Timestamp: 2020-06-20T05:54:08Z Generation: 8 Resource Version: 187864 Self Link: /apis/networking.gke.io/v1alpha1/networkloggings/default UID: 0f1ddd6e-4193-4295-9172-baa6a52aa6e6 Spec: Cluster: Allow: Delegate: true Log: false Deny: Delegate: false Log: false Events: Type Reason Age From Message ---- ------ ---- ---- ------- Warning InvalidNetworkLogging 16s (x3 over 11h) network-logging-controller, gke-anthos-default-pool-cee49209-0t09 cluster allow log action is invalid: delegate cannot be true when log is false Warning InvalidNetworkLogging 16s (x3 over 11h) network-logging-controller, gke-anthos-default-pool-cee49209-80fx cluster allow log action is invalid: delegate cannot be true when log is false
To limit CPU utilization spent on logging, a node can log up to 500 connections per second before it starts dropping logs. The network policies on the node are still being enforced. You can see if there are dropped policy logs by checking if any error counters are incrementing:
kubectl exec ANETD_POD_NAME -n kube-system -- curl -s http://localhost:9990/metrics |grep policy_logging
Replace
ANETD_POD_NAME
with the name of an anetd Pod. Check each node. anetd is the networking controller for Dataplane V2.
Logs with no name appear for Pods with default deny policies
Liveness, readiness, and startup probes require that the Pod accept Ingress connections made by the probes from kubelet. To ensure that these probes function correctly, GKE automatically permits probe traffic to the selected Pod as configured for the Pod regardless of any network policies applied to the Pod. You cannot change this behavior.
Logs for probe connections are similar to the following:
{
"connection":{
"src_ip":"10.88.1.1",
"dest_ip":"10.88.1.4",
"src_port":35848,
"dest_port":15021,
"protocol":"tcp",
"direction":"ingress"
},
"disposition":"allow",
"src":{
"instance":"10.88.1.1"
},
"dest":{
"pod_name":"testpod-745c798fc9-sfd9h",
"pod_namespace":"default",
"namespace":"default",
"workload_name":"testpod-745c798fc9",
"workload_kind":"ReplicaSet"
},
"count":1,
"policies": [
{
"name":""
}
],
"node_name":"gke-demo-default-pool-5dad52ed-k0h1",
"timestamp":"2021-04-01T12:42:32.1898720941Z"
}
The log has the following characteristics:
- The value of
policies.name
is empty because there is no associated network policy to permit the connection. - The value of
connection.src_ip
does not correspond to any Pods or nodes.
What's next
- Learn how to view and analyze logs with Cloud Logging.
- Implement common approaches to restrict traffic using network policies.
- Learn how to view workload connectivity with GKE Dataplane V2.