Use ICMP/ping in policy rules
Use Calico network policy to allow and deny ICMP/ping messages.
The Internet Control Message Protocol (ICMP) provides valuable network diagnostic functions, but it can also be used maliciously. Attackers can use it to learn about your network, or for DoS attacks. Using Calico network policy, you can control where ICMP is used. For example, you can:
- Allow ICMP ping, but only for workloads, host endpoints (or both)
- Allow ICMP for pods launched by operators for diagnostic purposes, but block other uses
- Temporarily enable ICMP to diagnose a problem, then disable it after the problem is resolved
- Deny/allow ICMPv4 and/or ICMPv6
This how-to guide uses the following Calico features:
GlobalNetworkPolicy or NetworkPolicy with:
- Protocol match for ICMPv4 and ICMPv6
- icmp/NotICMP match for ICMP type and code
ICMP packet type and code
Calico network policy also lets you deny and allow ICMP traffic based on specific types and codes. For example, you can specify ICMP type 5, code 2 to match specific ICMP redirect packets.
For details, see ICMP type and code.
- Deny all ICMP, all workloads and host endpoints
- Allow ICMP ping, all workloads and host endpoints
- Allow ICMP matching protocol type and code, all Kubernetes pods
Deny all ICMP, all workloads and host endpoints
In this example, we introduce a “deny all ICMP” GlobalNetworkPolicy.
This policy selects all workloads and host endpoints. It enables a default deny for all workloads and host endpoints, in addition to the explicit ICMP deny rules specified in the policy.
If your ultimate goal is to allow some traffic, have your regular “allow” policies in place before applying a global deny-all ICMP traffic policy.
In this example, all workloads and host endpoints are blocked from sending or receiving ICMPv4 and ICMPv6 messages.
If ICMPv6 messages are not used in your deployment, it is still good practice to deny them specifically as shown below.
In any “deny-all” Calico network policy, be sure to specify a lower order (order:200) than regular policies that might allow traffic.
apiVersion: projectcalico.org/v3 kind: GlobalNetworkPolicy metadata: name: block-icmp spec: order: 200 selector: all() types: - Ingress - Egress ingress: - action: Deny protocol: ICMP - action: Deny protocol: ICMPv6 egress: - action: Deny protocol: ICMP - action: Deny protocol: ICMPv6
Allow ICMP ping, all workloads and host endpoints
In this example, workloads and host endpoints can receive ICMPv4 type 8 and ICMPv6 type 128 ping requests that come from other workloads and host endpoints.
All other traffic may be allowed by other policies. If traffic is not explicitly allowed, it will be denied by default.
The policy applies only to ingress traffic. (Egress traffic is not affected, and default deny is not enforced for egress.)
apiVersion: projectcalico.org/v3 kind: GlobalNetworkPolicy metadata: name: allow-ping-in-cluster spec: selector: all() types: - Ingress ingress: - action: Allow protocol: ICMP source: selector: all() icmp: type: 8 # Ping request - action: Allow protocol: ICMPv6 source: selector: all() icmp: type: 128 # Ping request
Allow ICMP matching protocol type and code, all Kubernetes pods
In this example, only Kubernetes pods that match the selector projectcalico.org/orchestrator == ‘kubernetes’ are allowed to receive ICMPv4 code: 1 # host unreachable messages.
apiVersion: projectcalico.org/v3 kind: GlobalNetworkPolicy metadata: name: allow-host-unreachable spec: selector: projectcalico.org/orchestrator == 'kubernetes' types: - Ingress ingress: - action: Allow protocol: ICMP icmp: type: 3 # Destination unreachable code: 1 # Host unreachable
Above and beyond
For more on the ICMP match criteria, see: