Layer 3 Examples
The layer 3 policy establishes the base connectivity rules regarding which endpoints can talk to each other. Layer 3 policies can be specified using the following methods:
Endpoints Based: This is used to describe the relationship if both endpoints are managed by Cilium and are thus assigned labels. The advantage of this method is that IP addresses are not encoded into the policies and the policy is completely decoupled from the addressing.
Services based: This is an intermediate form between Labels and CIDR and makes use of the services concept in the orchestration system. A good example of this is the Kubernetes concept of Service endpoints which are automatically maintained to contain all backend IP addresses of a service. This allows to avoid hardcoding IP addresses into the policy even if the destination endpoint is not controlled by Cilium.
Entities Based: Entities are used to describe remote peers which can be categorized without knowing their IP addresses. This includes connectivity to the local host serving the endpoints or all connectivity to outside of the cluster.
IP/CIDR based: This is used to describe the relationship to or from external services if the remote peer is not an endpoint. This requires to hardcode either IP addresses or subnets into the policies. This construct should be used as a last resort as it requires stable IP or subnet assignments.
DNS based: Selects remote, non-cluster, peers using DNS names converted to IPs via DNS lookups. It shares all limitations of the IP/CIDR based rules above. DNS information is acquired by routing DNS traffic via a proxy. DNS TTLs are respected.
Endpoints Based
Endpoints-based L3 policy is used to establish rules between endpoints inside the cluster managed by Cilium. Endpoints-based L3 policies are defined by using an Endpoint Selector inside a rule to select what kind of traffic can be received (on ingress), or sent (on egress). An empty Endpoint Selector allows all traffic. The examples below demonstrate this in further detail.
Note
Kubernetes: See section Namespaces for details on how the Endpoint Selector applies in a Kubernetes environment with regard to namespaces.
Ingress
An endpoint is allowed to receive traffic from another endpoint if at least one
ingress rule exists which selects the destination endpoint with the
Endpoint Selector in the endpointSelector
field. To restrict traffic upon
ingress to the selected endpoint, the rule selects the source endpoint with the
Endpoint Selector in the fromEndpoints
field.
Simple Ingress Allow
The following example illustrates how to use a simple ingress rule to allow
communication from endpoints with the label role=frontend
to endpoints with
the label role=backend
.
apiVersion: "cilium.io/v2"
kind: CiliumNetworkPolicy
metadata:
name: "l3-rule"
spec:
endpointSelector:
matchLabels:
role: backend
ingress:
- fromEndpoints:
- matchLabels:
role: frontend
[{
"labels": [{"key": "name", "value": "l3-rule"}],
"endpointSelector": {"matchLabels": {"role":"backend"}},
"ingress": [{
"fromEndpoints": [
{"matchLabels":{"role":"frontend"}}
]
}]
}]
Ingress Allow All Endpoints
An empty Endpoint Selector will select all endpoints, thus writing a rule that will allow all ingress traffic to an endpoint may be done as follows:
apiVersion: "cilium.io/v2"
kind: CiliumNetworkPolicy
metadata:
name: "allow-all-to-victim"
spec:
endpointSelector:
matchLabels:
role: victim
ingress:
- fromEndpoints:
- {}
[{
"labels": [{"key": "name", "value": "allow-all-to-victim"}],
"endpointSelector": {"matchLabels": {"role":"victim"}},
"ingress": [{
"fromEndpoints": [
{"matchLabels":{}}
]
}]
}]
Note that while the above examples allow all ingress traffic to an endpoint, this does not mean that all endpoints are allowed to send traffic to this endpoint per their policies. In other words, policy must be configured on both sides (sender and receiver).
Egress
An endpoint is allowed to send traffic to another endpoint if at least one
egress rule exists which selects the destination endpoint with the
Endpoint Selector in the endpointSelector
field. To restrict traffic upon
egress to the selected endpoint, the rule selects the destination endpoint with
the Endpoint Selector in the toEndpoints
field.
Simple Egress Allow
The following example illustrates how to use a simple egress rule to allow
communication to endpoints with the label role=backend
from endpoints with
the label role=frontend
.
apiVersion: "cilium.io/v2"
kind: CiliumNetworkPolicy
metadata:
name: "l3-egress-rule"
spec:
endpointSelector:
matchLabels:
role: frontend
egress:
- toEndpoints:
- matchLabels:
role: backend
[{
"labels": [{"key": "name", "value": "l3-egress-rule"}],
"endpointSelector": {"matchLabels": {"role":"frontend"}},
"egress": [{
"toEndpoints": [
{"matchLabels":{"role":"backend"}}
]
}]
}]
Egress Allow All Endpoints
An empty Endpoint Selector will select all egress endpoints from an endpoint
based on the CiliumNetworkPolicy namespace (default
by default). The
following rule allows all egress traffic from endpoints with the label
role=frontend
to all other endpoints in the same namespace:
apiVersion: "cilium.io/v2"
kind: CiliumNetworkPolicy
metadata:
name: "allow-all-from-frontend"
spec:
endpointSelector:
matchLabels:
role: frontend
egress:
- toEndpoints:
- {}
[{
"labels": [{"key": "name", "value": "allow-all-from-frontend"}],
"endpointSelector": {"matchLabels": {"role":"frontend"}},
"egress": [{
"toEndpoints": [
{"matchLabels":{}}
]
}]
}]
Note that while the above examples allow all egress traffic from an endpoint, the receivers of the egress traffic may have ingress rules that deny the traffic. In other words, policy must be configured on both sides (sender and receiver).
Ingress/Egress Default Deny
An endpoint can be put into the default deny mode at ingress or egress if a rule selects the endpoint and contains the respective rule section ingress or egress.
Note
Any rule selecting the endpoint will have this effect, this example illustrates how to put an endpoint into default deny mode without whitelisting other peers at the same time.
apiVersion: "cilium.io/v2"
kind: CiliumNetworkPolicy
metadata:
name: "deny-all-egress"
spec:
endpointSelector:
matchLabels:
role: restricted
egress:
- {}
[{
"labels": [{"key": "name", "value": "deny-all-egress"}],
"endpointSelector": {"matchLabels": {"role":"restricted"}},
"egress": [{}]
}]
Additional Label Requirements
It is often required to apply the principle of separation of concern when defining policies. For this reason, an additional construct exists which allows to establish base requirements for any connectivity to happen.
For this purpose, the fromRequires
field can be used to establish label
requirements which serve as a foundation for any fromEndpoints
relationship. fromRequires
is a list of additional constraints which must
be met in order for the selected endpoints to be reachable. These additional
constraints do not grant access privileges by themselves, so to allow traffic
there must also be rules which match fromEndpoints
. The same applies for
egress policies, with toRequires
and toEndpoints
.
The purpose of this rule is to allow establishing base requirements such as, any
endpoint in env=prod
can only be accessed if the source endpoint also carries
the label env=prod
.
This example shows how to require every endpoint with the label env=prod
to
be only accessible if the source endpoint also has the label env=prod
.
apiVersion: "cilium.io/v2"
kind: CiliumNetworkPolicy
metadata:
name: "requires-rule"
specs:
- description: "For endpoints with env=prod, only allow if source also has label env=prod"
endpointSelector:
matchLabels:
env: prod
ingress:
- fromRequires:
- matchLabels:
env: prod
[{
"labels": [{"key": "name", "value": "requires-rule"}],
"endpointSelector": {"matchLabels": {"env":"prod"}},
"ingress": [{
"fromRequires": [
{"matchLabels":{"env":"prod"}}
]
}]
}]
This fromRequires
rule doesn’t allow anything on its own and needs to be
combined with other rules to allow traffic. For example, when combined with the
example policy below, the endpoint with label env=prod
will become
accessible from endpoints that have both labels env=prod
and
role=frontend
.
apiVersion: "cilium.io/v2"
kind: CiliumNetworkPolicy
metadata:
name: "l3-rule"
specs:
- description: "For endpoints with env=prod, allow if source also has label role=frontend"
endpointSelector:
matchLabels:
env: prod
ingress:
- fromEndpoints:
- matchLabels:
role: frontend
[{
"labels": [{"key": "name", "value": "l3-rule"}],
"endpointSelector": {"matchLabels": {"env":"prod"}},
"ingress": [{
"fromEndpoints": [
{"matchLabels":{"role":"frontend"}}
]
}]
}]
Services based
Note
Services based rules rules will only take effect on Kubernetes services without a selector.
Traffic from pods to services running in your cluster can be allowed via
toServices
statements in Egress rules. Currently Kubernetes
Services without a Selector
are supported when defined by their name and namespace or label selector.
For services backed by pods, use Endpoints Based rules on the backend pod
labels.
This example shows how to allow all endpoints with the label id=app2
to talk to all endpoints of kubernetes service myservice
in kubernetes
namespace default
.
apiVersion: "cilium.io/v2"
kind: CiliumNetworkPolicy
metadata:
name: "service-rule"
spec:
endpointSelector:
matchLabels:
id: app2
egress:
- toServices:
- k8sService:
serviceName: myservice
namespace: default
[{
"labels": [{"key": "name", "value": "service-rule"}],
"endpointSelector": {
"matchLabels": {
"id": "app2"
}
},
"egress": [
{
"toServices": [
{
"k8sService": {
"serviceName": "myservice",
"namespace": "default"
}
}
]
}
]
}]
This example shows how to allow all endpoints with the label id=app2
to talk to all endpoints of all kubernetes services without selectors which
have external:yes
set as the label.
apiVersion: "cilium.io/v2"
kind: CiliumNetworkPolicy
metadata:
name: "service-labels-rule"
spec:
endpointSelector:
matchLabels:
id: app2
egress:
- toServices:
- k8sServiceSelector:
selector:
matchLabels:
external: "yes"
[{
"labels": [{"key": "name", "value": "service-labels-rule"}],
"endpointSelector": {
"matchLabels": {
"id": "app2"
}
},
"egress": [
{
"toServices": [
{
"k8sServiceSelector": {
"selector": {
"matchLabels": {
"external": "yes"
}
}
}
}
]
}
]
}
]
Limitations
toServices
statements must not be combined with toPorts
statements in the
same rule. If a rule combines both these statements, the policy is rejected.
Entities Based
fromEntities
is used to describe the entities that can access the selected
endpoints. toEntities
is used to describe the entities that can be accessed
by the selected endpoints.
The following entities are defined:
- host
The host entity includes the local host. This also includes all containers running in host networking mode on the local host.
- remote-node
Any node in any of the connected clusters other than the local host. This also includes all containers running in host-networking mode on remote nodes. (Requires the option
enable-remote-node-identity
to be enabled)- kube-apiserver
The kube-apiserver entity represents the kube-apiserver in a Kubernetes cluster. This entity represents both deployments of the kube-apiserver: within the cluster and outside of the cluster.
- ingress
The ingress entity represents the Cilium Envoy instance that handles ingress L7 traffic. Be aware that this also applies for pod-to-pod traffic within the same cluster when using ingress endpoints (also known as hairpinning).
- cluster
Cluster is the logical group of all network endpoints inside of the local cluster. This includes all Cilium-managed endpoints of the local cluster, unmanaged endpoints in the local cluster, as well as the host, remote-node, and init identities.
- init
The init entity contains all endpoints in bootstrap phase for which the security identity has not been resolved yet. This is typically only observed in non-Kubernetes environments. See section Endpoint Lifecycle for details.
- health
The health entity represents the health endpoints, used to check cluster connectivity health. Each node managed by Cilium hosts a health endpoint. See Checking cluster connectivity health for details on health checks.
- unmanaged
The unmanaged entity represents endpoints not managed by Cilium. Unmanaged endpoints are considered part of the cluster and are included in the cluster entity.
- world
The world entity corresponds to all endpoints outside of the cluster. Allowing to world is identical to allowing to CIDR 0.0.0.0/0. An alternative to allowing from and to world is to define fine grained DNS or CIDR based policies.
- all
The all entity represents the combination of all known clusters as well world and whitelists all communication.
Access to/from local host
Allow all endpoints with the label env=dev
to access the host that is
serving the particular endpoint.
Note
Kubernetes will automatically allow all communication from the
local host of all local endpoints. You can run the agent with the
option --allow-localhost=policy
to disable this behavior which
will give you control over this via policy.
apiVersion: "cilium.io/v2"
kind: CiliumNetworkPolicy
metadata:
name: "dev-to-host"
spec:
endpointSelector:
matchLabels:
env: dev
egress:
- toEntities:
- host
[{
"labels": [{"key": "name", "value": "dev-to-host"}],
"endpointSelector": {"matchLabels": {"env":"dev"}},
"egress": [{
"toEntities": ["host"]
}]
}]
Access to/from all nodes in the cluster
Allow all endpoints with the label env=dev
to receive traffic from any host
in the cluster that Cilium is running on.
apiVersion: "cilium.io/v2"
kind: CiliumNetworkPolicy
metadata:
name: "to-dev-from-nodes-in-cluster"
spec:
endpointSelector:
matchLabels:
env: dev
ingress:
- fromEntities:
- host
- remote-node
[{
"labels": [{"key": "name", "value": "to-dev-from-nodes-in-cluster"}],
"endpointSelector": {"matchLabels": {"env":"dev"}},
"ingress": [{
"fromEntities": [
"host",
"remote-node"
]
}]
}]
Access to/from outside cluster
This example shows how to enable access from outside of the cluster to all
endpoints that have the label role=public
.
apiVersion: "cilium.io/v2"
kind: CiliumNetworkPolicy
metadata:
name: "from-world-to-role-public"
spec:
endpointSelector:
matchLabels:
role: public
ingress:
- fromEntities:
- world
[{
"labels": [{"key": "name", "value":"from-world-to-role-public"}],
"endpointSelector": {"matchLabels": {"role":"public"}},
"ingress": [{
"fromEntities": ["world"]
}]
}]
IP/CIDR based
CIDR policies are used to define policies to and from endpoints which are not managed by Cilium and thus do not have labels associated with them. These are typically external services, VMs or metal machines running in particular subnets. CIDR policy can also be used to limit access to external services, for example to limit external access to a particular IP range. CIDR policies can be applied at ingress or egress.
CIDR rules apply if Cilium cannot map the source or destination to an identity derived from endpoint labels, ie the Special Identities. For example, CIDR rules will apply to traffic where one side of the connection is:
A network endpoint outside the cluster
The host network namespace where the pod is running.
Within the cluster prefix but the IP’s networking is not provided by Cilium.
Conversely, CIDR rules do not apply to traffic where both sides of the connection are either managed by Cilium or use an IP belonging to a node in the cluster (including host networking pods). This traffic may be allowed using labels, services or entities -based policies as described above.
Ingress
- fromCIDR
List of source prefixes/CIDRs that are allowed to talk to all endpoints selected by the
endpointSelector
.- fromCIDRSet
List of source prefixes/CIDRs that are allowed to talk to all endpoints selected by the
endpointSelector
, along with an optional list of prefixes/CIDRs per source prefix/CIDR that are subnets of the source prefix/CIDR from which communication is not allowed.
Egress
- toCIDR
List of destination prefixes/CIDRs that endpoints selected by
endpointSelector
are allowed to talk to. Note that endpoints which are selected by afromEndpoints
are automatically allowed to reply back to the respective destination endpoints.- toCIDRSet
List of destination prefixes/CIDRs that are allowed to talk to all endpoints selected by the
endpointSelector
, along with an optional list of prefixes/CIDRs per source prefix/CIDR that are subnets of the destination prefix/CIDR to which communication is not allowed.
Allow to external CIDR block
This example shows how to allow all endpoints with the label app=myService
to talk to the external IP 20.1.1.1
, as well as the CIDR prefix 10.0.0.0/8
,
but not CIDR prefix 10.96.0.0/12
apiVersion: "cilium.io/v2"
kind: CiliumNetworkPolicy
metadata:
name: "cidr-rule"
spec:
endpointSelector:
matchLabels:
app: myService
egress:
- toCIDR:
- 20.1.1.1/32
- toCIDRSet:
- cidr: 10.0.0.0/8
except:
- 10.96.0.0/12
[{
"labels": [{"key": "name", "value": "cidr-rule"}],
"endpointSelector": {"matchLabels":{"app":"myService"}},
"egress": [{
"toCIDR": [
"20.1.1.1/32"
]
}, {
"toCIDRSet": [{
"cidr": "10.0.0.0/8",
"except": [
"10.96.0.0/12"
]}
]
}]
}]
DNS based
DNS policies are used to define Layer 3 policies to endpoints that are not managed by Cilium, but have DNS queryable domain names. The IP addresses provided in DNS responses are allowed by Cilium in a similar manner to IPs in CIDR based policies. They are an alternative when the remote IPs may change or are not know a priori, or when DNS is more convenient. To enforce policy on DNS requests themselves, see Layer 7 Examples.
Note
In order to associate domain names with IP addresses, Cilium intercepts
DNS responses per-Endpoint using a DNS Proxy. This requires Cilium
to be configured with --enable-l7-proxy=true
and an L7 policy allowing
DNS requests. For more details, see Obtaining DNS Data for use by toFQDNs.
An L3 CIDR based rule is generated for every toFQDNs
rule and applies to the same endpoints. The IP information is selected for
insertion by matchName
or matchPattern
rules, and is collected from all
DNS responses seen by Cilium on the node. Multiple selectors may be included in
a single egress rule.
Note
The DNS Proxy is provided in each Cilium agent. As a result, DNS requests targeted by policies depend on the availability of the Cilium agent pod. This includes DNS policies as well as Layer 7 Protocol Visibility annotations.
toFQDNs
egress rules cannot contain any other L3 rules, such as
toEndpoints
(under Endpoints Based) and toCIDRs
(under CIDR Based).
They may contain L4/L7 rules, such as toPorts
(see Layer 4 Examples)
with, optionally, HTTP
and Kafka
sections (see Layer 7 Examples).
Note
DNS based rules are intended for external connections and behave similarly to CIDR based rules. See Services based and Endpoints based for cluster-internal traffic.
IPs to be allowed are selected via:
toFQDNs.matchName
Inserts IPs of domains that match
matchName
exactly. Multiple distinct names may be included in separatematchName
entries and IPs for domains that match anymatchName
will be inserted.toFQDNs.matchPattern
Inserts IPs of domains that match the pattern in
matchPattern
, accounting for wildcards. Patterns are composed of literal characters that are allowed in domain names: a-z, 0-9,.
and-
.*
is allowed as a wildcard with a number of convenience behaviors:*
within a domain allows 0 or more valid DNS characters, except for the.
separator.*.cilium.io
will matchsub.cilium.io
but notcilium.io
orsub.sub.cilium.io
.part*ial.com
will matchpartial.com
andpart-extra-ial.com
.*
alone matches all names, and inserts all cached DNS IPs into this rule.
The example below allows all DNS traffic on port 53 to the DNS service and
intercepts it via the DNS Proxy. If using a non-standard DNS port for
a DNS application behind a Kubernetes service, the port must match the backend
port. When the application makes a request for my-remote-service.com, Cilium
learns the IP address and will allow traffic due to the match on the name under
the toFQDNs.matchName
rule.
Example
apiVersion: "cilium.io/v2"
kind: CiliumNetworkPolicy
metadata:
name: "to-fqdn"
spec:
endpointSelector:
matchLabels:
app: test-app
egress:
- toEndpoints:
- matchLabels:
"k8s:io.kubernetes.pod.namespace": kube-system
"k8s:k8s-app": kube-dns
toPorts:
- ports:
- port: "53"
protocol: ANY
rules:
dns:
- matchPattern: "*"
- toFQDNs:
- matchName: "my-remote-service.com"
[
{
"endpointSelector": {
"matchLabels": {
"app": "test-app"
}
},
"egress": [
{
"toEndpoints": [
{
"matchLabels": {
"app-type": "dns"
}
}
],
"toPorts": [
{
"ports": [
{
"port": "53",
"protocol": "ANY"
}
],
"rules": {
"dns": [
{ "matchPattern": "*" }
]
}
}
]
},
{
"toFQDNs": [
{
"matchName": "my-remote-service.com"
}
]
}
]
}
]
Managing Short-Lived Connections & Maximum IPs per FQDN/endpoint
Many short-lived connections can grow the number of IPs mapping to an FQDN
quickly. In order to limit the number of IP addresses that map a particular
FQDN, each FQDN has a per-endpoint max capacity of IPs that will be retained
(default: 50). Once this limit is exceeded, the oldest IP entries are
automatically expired from the cache. This capacity can be changed using the
--tofqdns-endpoint-max-ip-per-hostname
option.
As with long-lived connections above, live connections are not expired until they terminate. It is safe to mix long- and short-lived connections from the same Pod. IPs above the limit described above will only be removed if unused by a connection.
Layer 4 Examples
Limit ingress/egress ports
Layer 4 policy can be specified in addition to layer 3 policies or independently. It restricts the ability of an endpoint to emit and/or receive packets on a particular port using a particular protocol. If no layer 4 policy is specified for an endpoint, the endpoint is allowed to send and receive on all layer 4 ports and protocols including ICMP. If any layer 4 policy is specified, then ICMP will be blocked unless it’s related to a connection that is otherwise allowed by the policy. Layer 4 policies apply to ports after service port mapping has been applied.
Layer 4 policy can be specified at both ingress and egress using the
toPorts
field. The toPorts
field takes a PortProtocol
structure
which is defined as follows:
// PortProtocol specifies an L4 port with an optional transport protocol
type PortProtocol struct {
// Port is an L4 port number. For now the string will be strictly
// parsed as a single uint16. In the future, this field may support
// ranges in the form "1024-2048"
Port string `json:"port"`
// Protocol is the L4 protocol. If omitted or empty, any protocol
// matches. Accepted values: "TCP", "UDP", ""/"ANY"
//
// Matching on ICMP is not supported.
//
// +optional
Protocol string `json:"protocol,omitempty"`
}
Example (L4)
The following rule limits all endpoints with the label app=myService
to
only be able to emit packets using TCP on port 80, to any layer 3 destination:
apiVersion: "cilium.io/v2"
kind: CiliumNetworkPolicy
metadata:
name: "l4-rule"
spec:
endpointSelector:
matchLabels:
app: myService
egress:
- toPorts:
- ports:
- port: "80"
protocol: TCP
[{
"labels": [{"key": "name", "value": "l4-rule"}],
"endpointSelector": {"matchLabels":{"app":"myService"}},
"egress": [{
"toPorts": [
{"ports":[ {"port": "80", "protocol": "TCP"}]}
]
}]
}]
Labels-dependent Layer 4 rule
This example enables all endpoints with the label role=frontend
to
communicate with all endpoints with the label role=backend
, but they must
communicate using TCP on port 80. Endpoints with other labels will not be
able to communicate with the endpoints with the label role=backend
, and
endpoints with the label role=frontend
will not be able to communicate with
role=backend
on ports other than 80.
apiVersion: "cilium.io/v2"
kind: CiliumNetworkPolicy
metadata:
name: "l4-rule"
spec:
endpointSelector:
matchLabels:
role: backend
ingress:
- fromEndpoints:
- matchLabels:
role: frontend
toPorts:
- ports:
- port: "80"
protocol: TCP
[{
"labels": [{"key": "name", "value": "l4-rule"}],
"endpointSelector": {"matchLabels":{"role":"backend"}},
"ingress": [{
"fromEndpoints": [
{"matchLabels":{"role":"frontend"}}
],
"toPorts": [
{"ports":[ {"port": "80", "protocol": "TCP"}]}
]
}]
}]
CIDR-dependent Layer 4 Rule
This example enables all endpoints with the label role=crawler
to
communicate with all remote destinations inside the CIDR 192.0.2.0/24
, but
they must communicate using TCP on port 80. The policy does not allow Endpoints
without the label role=crawler
to communicate with destinations in the CIDR
192.0.2.0/24
. Furthermore, endpoints with the label role=crawler
will
not be able to communicate with destinations in the CIDR 192.0.2.0/24
on
ports other than port 80.
apiVersion: "cilium.io/v2"
kind: CiliumNetworkPolicy
metadata:
name: "cidr-l4-rule"
spec:
endpointSelector:
matchLabels:
role: crawler
egress:
- toCIDR:
- 192.0.2.0/24
toPorts:
- ports:
- port: "80"
protocol: TCP
[{
"labels": [{"key": "name", "value": "cidr-l4-rule"}],
"endpointSelector": {"matchLabels":{"role":"crawler"}},
"egress": [{
"toCIDR": [
"192.0.2.0/24"
],
"toPorts": [
{"ports":[ {"port": "80", "protocol": "TCP"}]}
]
}]
}]
Limit ICMP/ICMPv6 types
ICMP policy can be specified in addition to layer 3 policies or independently. It restricts the ability of an endpoint to emit and/or receive packets on a particular ICMP/ICMPv6 type (currently ICMP/ICMPv6 code is not supported). If any ICMP policy is specified, layer 4 and ICMP communication will be blocked unless it’s related to a connection that is otherwise allowed by the policy.
ICMP policy can be specified at both ingress and egress using the
icmps
field. The icmps
field takes a ICMPField
structure
which is defined as follows:
// ICMPField is a ICMP field.
type ICMPField struct {
// Family is a IP address version.
// Currently, we support `IPv4` and `IPv6`.
// `IPv4` is set as default.
//
// +default=IPv4
// +optional
Family string `json:"family,omitempty"`
// Type is a ICMP-type.
// It should be 0-255 (8bit).
Type uint8 `json:"type"`
}
Example (ICMP/ICMPv6)
The following rule limits all endpoints with the label app=myService
to
only be able to emit packets using ICMP with type 8 and ICMPv6 with type 128,
to any layer 3 destination:
apiVersion: "cilium.io/v2"
kind: CiliumNetworkPolicy
metadata:
name: "icmp-rule"
spec:
endpointSelector:
matchLabels:
app: myService
egress:
- icmps:
- fields:
- type: 8
family: IPv4
- type: 128
family: IPv6
[{
"labels": [{"key": "name", "value": "icmp-rule"}],
"endpointSelector": {"matchLabels":{"app":"myService"}},
"egress": [{
"icmps": [
{"fields":[ {"type": 8, "family": "IPv4"}]},
{"fields":[ {"type": 128, "family": "IPv6"}]}
]
}]
}]
Layer 7 Examples
Layer 7 policy rules are embedded into Layer 4 Examples rules and can be specified
for ingress and egress. L7Rules
structure is a base type containing an
enumeration of protocol specific fields.
// L7Rules is a union of port level rule types. Mixing of different port
// level rule types is disallowed, so exactly one of the following must be set.
// If none are specified, then no additional port level rules are applied.
type L7Rules struct {
// HTTP specific rules.
//
// +optional
HTTP []PortRuleHTTP `json:"http,omitempty"`
// Kafka-specific rules.
//
// +optional
Kafka []PortRuleKafka `json:"kafka,omitempty"`
// DNS-specific rules.
//
// +optional
DNS []PortRuleDNS `json:"dns,omitempty"`
}
The structure is implemented as a union, i.e. only one member field can be used
per port. If multiple toPorts
rules with identical PortProtocol
select
an overlapping list of endpoints, then the layer 7 rules are combined together
if they are of the same type. If the type differs, the policy is rejected.
Each member consists of a list of application protocol rules. A layer 7 request is permitted if at least one of the rules matches. If no rules are specified, then all traffic is permitted.
If a layer 4 rule is specified in the policy, and a similar layer 4 rule with layer 7 rules is also specified, then the layer 7 portions of the latter rule will have no effect.
Note
Unlike layer 3 and layer 4 policies, violation of layer 7 rules does not result in packet drops. Instead, if possible, an application protocol specific access denied message is crafted and returned, e.g. an HTTP 403 access denied is sent back for HTTP requests which violate the policy, or a DNS REFUSED response for DNS requests.
Note
There is currently a max limit of 40 ports with layer 7 policies per endpoint. This might change in the future when support for ranges is added.
Note
Layer 7 rules are not currently supported in Host Policies, i.e., policies that use Node Selector.
Note
Layer 7 policies –and pod annotations– result in traffic being proxied through an Envoy instance provided in each Cilium agent pod. As a result, L7 traffic targeted by policies depend on the availability of the Cilium agent pod. This includes L7 policies as well as Layer 7 Protocol Visibility annotations.
HTTP
The following fields can be matched on:
- Path
Path is an extended POSIX regex matched against the path of a request. Currently it can contain characters disallowed from the conventional “path” part of a URL as defined by RFC 3986. Paths must begin with a
/
. If omitted or empty, all paths are all allowed.- Method
Method is an extended POSIX regex matched against the method of a request, e.g.
GET
,POST
,PUT
,PATCH
,DELETE
, … If omitted or empty, all methods are allowed.- Host
Host is an extended POSIX regex matched against the host header of a request, e.g.
foo.com
. If omitted or empty, the value of the host header is ignored.- Headers
Headers is a list of HTTP headers which must be present in the request. If omitted or empty, requests are allowed regardless of headers present.
Allow GET /public
The following example allows GET
requests to the URL /public
from the
endpoints with the labels env=prod
to endpoints with the labels
app=service
, but requests to any other URL, or using another method, will
be rejected. Requests on ports other than port 80 will be dropped.
apiVersion: "cilium.io/v2"
kind: CiliumNetworkPolicy
metadata:
name: "rule1"
spec:
description: "Allow HTTP GET /public from env=prod to app=service"
endpointSelector:
matchLabels:
app: service
ingress:
- fromEndpoints:
- matchLabels:
env: prod
toPorts:
- ports:
- port: "80"
protocol: TCP
rules:
http:
- method: "GET"
path: "/public"
[{
"labels": [{"key": "name", "value": "rule1"}],
"endpointSelector": {"matchLabels": {"app": "service"}},
"ingress": [{
"fromEndpoints": [
{"matchLabels": {"env": "prod"}}
]},{
"toPorts": [{
"ports": [
{"port": "80", "protocol": "TCP"}
],
"rules": {
"http": [
{
"method": "GET",
"path": "/public"
}
]
}
}]
}]
}]
All GET /path1 and PUT /path2 when header set
The following example limits all endpoints which carry the labels
app=myService
to only be able to receive packets on port 80 using TCP.
While communicating on this port, the only API endpoints allowed will be GET
/path1
, and PUT /path2
with the HTTP header X-My-Header
set to
true
:
apiVersion: "cilium.io/v2"
kind: CiliumNetworkPolicy
metadata:
name: "l7-rule"
spec:
endpointSelector:
matchLabels:
app: myService
ingress:
- toPorts:
- ports:
- port: '80'
protocol: TCP
rules:
http:
- method: GET
path: "/path1$"
- method: PUT
path: "/path2$"
headers:
- 'X-My-Header: true'
[{
"labels": [{"key": "name", "value": "l7-rule"}],
"endpointSelector": {"matchLabels":{"app":"myService"}},
"ingress": [{
"toPorts": [{
"ports": [
{"port": "80", "protocol": "TCP"}
],
"rules": {
"http": [
{
"method": "GET",
"path": "/path1$"
},{
"method": "PUT",
"path": "/path2$",
"headers": ["X-My-Header: true"]
}
]
}
}]
}]
}]
Kafka (beta)
Note
This is a beta feature. Please provide feedback and file a GitHub issue if you experience any problems.
PortRuleKafka is a list of Kafka protocol constraints. All fields are optional, if all fields are empty or missing, the rule will match all Kafka messages. There are two ways to specify the Kafka rules. We can choose to specify a high-level “produce” or “consume” role to a topic or choose to specify more low-level Kafka protocol specific apiKeys. Writing rules based on Kafka roles is easier and covers most common use cases, however if more granularity is needed then users can alternatively write rules using specific apiKeys.
The following fields can be matched on:
- Role
Role is a case-insensitive string which describes a group of API keys necessary to perform certain higher-level Kafka operations such as “produce” or “consume”. A Role automatically expands into all APIKeys required to perform the specified higher-level operation. The following roles are supported:
“produce”: Allow producing to the topics specified in the rule.
“consume”: Allow consuming from the topics specified in the rule.
This field is incompatible with the APIKey field, i.e APIKey and Role cannot both be specified in the same rule. If omitted or empty, and if APIKey is not specified, then all keys are allowed.
- APIKey
APIKey is a case-insensitive string matched against the key of a request, for example “produce”, “fetch”, “createtopic”, “deletetopic”. For a more extensive list, see the Kafka protocol reference. This field is incompatible with the Role field.
- APIVersion
APIVersion is the version matched against the api version of the Kafka message. If set, it must be a string representing a positive integer. If omitted or empty, all versions are allowed.
- ClientID
ClientID is the client identifier as provided in the request.
From Kafka protocol documentation: This is a user supplied identifier for the client application. The user can use any identifier they like and it will be used when logging errors, monitoring aggregates, etc. For example, one might want to monitor not just the requests per second overall, but the number coming from each client application (each of which could reside on multiple servers). This id acts as a logical grouping across all requests from a particular client.
If omitted or empty, all client identifiers are allowed.
- Topic
Topic is the topic name contained in the message. If a Kafka request contains multiple topics, then all topics in the message must be allowed by the policy or the message will be rejected.
This constraint is ignored if the matched request message type does not contain any topic. The maximum length of the Topic is 249 characters, which must be either
a-z
,A-Z
,0-9
,-
,.
or_
.If omitted or empty, all topics are allowed.
Allow producing to topic empire-announce using Role
apiVersion: "cilium.io/v2"
kind: CiliumNetworkPolicy
metadata:
name: "rule1"
spec:
description: "enable empire-hq to produce to empire-announce and deathstar-plans"
endpointSelector:
matchLabels:
app: kafka
ingress:
- fromEndpoints:
- matchLabels:
app: empire-hq
toPorts:
- ports:
- port: "9092"
protocol: TCP
rules:
kafka:
- role: "produce"
topic: "deathstar-plans"
- role: "produce"
topic: "empire-announce"
[{
"labels": [{"key": "name", "value": "rule1"}],
"endpointSelector": {"matchLabels": {"app": "kafka"}},
"ingress": [{
"fromEndpoints": [
{"matchLabels": {"app": "empire-hq"}}
],
"toPorts": [{
"ports": [
{"port": "9092", "protocol": "TCP"}
],
"rules": {
"kafka": [
{"role": "produce","topic": "deathstar-plans"},
{"role": "produce", "topic": "empire-announce"}
]
}
}]
}]
}]
Allow producing to topic empire-announce using apiKeys
apiVersion: "cilium.io/v2"
kind: CiliumNetworkPolicy
metadata:
name: "rule1"
spec:
description: "enable empire-hq to produce to empire-announce and deathstar-plans"
endpointSelector:
matchLabels:
app: kafka
ingress:
- fromEndpoints:
- matchLabels:
app: empire-hq
toPorts:
- ports:
- port: "9092"
protocol: TCP
rules:
kafka:
- apiKey: "apiversions"
- apiKey: "metadata"
- apiKey: "produce"
topic: "deathstar-plans"
- apiKey: "produce"
topic: "empire-announce"
[{
"labels": [{"key": "name", "value": "rule1"}],
"endpointSelector": {"matchLabels": {"app": "kafka"}},
"ingress": [{
"fromEndpoints": [
{"matchLabels": {"app": "empire-hq"}}
],
"toPorts": [{
"ports": [
{"port": "9092", "protocol": "TCP"}
],
"rules": {
"kafka": [
{"apiKey": "apiversions"},
{"apiKey": "metadata"},
{"apiKey": "produce", "topic": "deathstar-plans"},
{"apiKey": "produce", "topic": "empire-announce"}
]
}
}]
}]
}]
DNS Policy and IP Discovery
Policy may be applied to DNS traffic, allowing or disallowing specific DNS
query names or patterns of names (other DNS fields, such as query type, are not
considered). This policy is effected via a DNS proxy, which is also used to
collect IPs used to populate L3 DNS based toFQDNs
rules.
Note
While Layer 7 DNS policy can be applied without any other Layer 3 rules, the presence of a Layer 7 rule (with its Layer 3 and 4 components) will block other traffic.
DNS policy may be applied via:
matchName
Allows queries for domains that match
matchName
exactly. Multiple distinct names may be included in separatematchName
entries and queries for domains that match anymatchName
will be allowed.matchPattern
Allows queries for domains that match the pattern in
matchPattern
, accounting for wildcards. Patterns are composed of literal characters that that are allowed in domain names: a-z, 0-9,.
and-
.*
is allowed as a wildcard with a number of convenience behaviors:*
within a domain allows 0 or more valid DNS characters, except for the.
separator.*.cilium.io
will matchsub.cilium.io
but notcilium.io
.part*ial.com
will matchpartial.com
andpart-extra-ial.com
.*
alone matches all names, and inserts all IPs in DNS responses into the cilium-agent DNS cache.
In this example, L7 DNS policy allows queries for cilium.io
, any subdomains
of cilium.io
, and any subdomains of api.cilium.io
. No other DNS queries
will be allowed.
The separate L3 toFQDNs
egress rule allows connections to any IPs returned
in DNS queries for cilium.io
, sub.cilium.io
, service1.api.cilium.io
and any matches of special*service.api.cilium.io
, such as
special-region1-service.api.cilium.io
but not
region1-service.api.cilium.io
. DNS queries to anothersub.cilium.io
are
allowed but connections to the returned IPs are not, as there is no L3
toFQDNs
rule selecting them. L4 and L7 policy may also be applied (see
DNS based), restricting connections to TCP port 80 in this case.
apiVersion: cilium.io/v2
kind: CiliumNetworkPolicy
metadata:
name: "tofqdn-dns-visibility"
spec:
endpointSelector:
matchLabels:
any:org: alliance
egress:
- toEndpoints:
- matchLabels:
"k8s:io.kubernetes.pod.namespace": kube-system
"k8s:k8s-app": kube-dns
toPorts:
- ports:
- port: "53"
protocol: ANY
rules:
dns:
- matchName: "cilium.io"
- matchPattern: "*.cilium.io"
- matchPattern: "*.api.cilium.io"
- toFQDNs:
- matchName: "cilium.io"
- matchName: "sub.cilium.io"
- matchName: "service1.api.cilium.io"
- matchPattern: "special*service.api.cilium.io"
toPorts:
- ports:
- port: "80"
protocol: TCP
[
{
"endpointSelector": {
"matchLabels": {
"app": "test-app"
}
},
"egress": [
{
"toEndpoints": [
{
"matchLabels": {
"app-type": "dns"
}
}
],
"toPorts": [
{
"ports": [
{
"port": "53",
"protocol": "ANY"
}
],
"rules": {
"dns": [
{ "matchName": "cilium.io" },
{ "matchPattern": "*.cilium.io" },
{ "matchPattern": "*.api.cilium.io" }
]
}
}
]
},
{
"toFQDNs": [
{ "matchName": "cilium.io" },
{ "matchName": "sub.cilium.io" },
{ "matchName": "service1.api.cilium.io" },
{ "matchPattern": "special*service.api.cilium.io" }
]
}
]
}
]
Note
When applying DNS policy in kubernetes, queries for
service.namespace.svc.cluster.local. must be explicitly allowed
with matchPattern: *.*.svc.cluster.local.
.
Similarly, queries that rely on the DNS search list to complete the
FQDN must be allowed in their entirety. e.g. A query for
servicename
that succeeds with
servicename.namespace.svc.cluster.local.
must have the latter
allowed with matchName
or matchPattern
. See Alpine/musl deployments and DNS Refused.
Obtaining DNS Data for use by toFQDNs
IPs are obtained via intercepting DNS requests with a proxy or DNS polling, and
matching names are inserted irrespective of how the data is obtained. These IPs
can be selected with toFQDN
rules. DNS responses are cached within Cilium
agent respecting TTL.
DNS Proxy
A DNS Proxy intercepts egress DNS traffic and records IPs seen in the responses. This interception is, itself, a separate policy rule governing the DNS requests, and must be specified separately. For details on how to enforce policy on DNS requests and configuring the DNS proxy, see Layer 7 Examples.
Only IPs in intercepted DNS responses to an application will be allowed in the Cilium policy rules. For a given domain name, IPs from responses to all pods managed by a Cilium instance are allowed by policy (respecting TTLs). This ensures that allowed IPs are consistent with those returned to applications. The DNS Proxy is the only method to allow IPs from responses allowed by wildcard L7 DNS
matchPattern
rules for use intoFQDNs
rules.The following example obtains DNS data by interception without blocking any DNS requests. It allows L3 connections to
cilium.io
,sub.cilium.io
and any subdomains ofsub.cilium.io
.
apiVersion: cilium.io/v2
kind: CiliumNetworkPolicy
metadata:
name: "tofqdn-dns-visibility"
spec:
endpointSelector:
matchLabels:
any:org: alliance
egress:
- toEndpoints:
- matchLabels:
"k8s:io.kubernetes.pod.namespace": kube-system
"k8s:k8s-app": kube-dns
toPorts:
- ports:
- port: "53"
protocol: ANY
rules:
dns:
- matchPattern: "*"
- toFQDNs:
- matchName: "cilium.io"
- matchName: "sub.cilium.io"
- matchPattern: "*.sub.cilium.io"
[
{
"endpointSelector": {
"matchLabels": {
"app": "test-app"
}
},
"egress": [
{
"toEndpoints": [
{
"matchLabels": {
"app-type": "dns"
}
}
],
"toPorts": [
{
"ports": [
{
"port": "53",
"protocol": "ANY"
}
],
"rules": {
"dns": [
{ "matchPattern": "*" }
]
}
}
]
},
{
"toFQDNs": [
{ "matchName": "cilium.io" },
{ "matchName": "sub.cilium.io" },
{ "matchPattern": "*.sub.cilium.io" }
]
}
]
}
]
Alpine/musl deployments and DNS Refused
Some common container images treat the DNS Refused
response when the DNS
Proxy rejects a query as a more general failure. This stops traversal of the
search list defined in /etc/resolv.conf
. It is common for pods to search by
appending .svc.cluster.local.
to DNS queries. When this occurs, a lookup
for cilium.io
may first be attempted as
cilium.io.namespace.svc.cluster.local.
and rejected by the proxy. Instead
of continuing and eventually attempting cilium.io.
alone, the Pod treats
the DNS lookup is treated as failed.
This can be mitigated with the --tofqdns-dns-reject-response-code
option.
The default is refused
but nameError
can be selected, causing the proxy
to return a NXDomain response to refused queries.
A more pod-specific solution is to configure ndots
appropriately for each
Pod, via dnsConfig
, so that the search list is not used for DNS lookups
that do not need it. See the Kubernetes documentation
for instructions.
Deny Policies
Deny policies, available and enabled by default since Cilium 1.9, allows to explicitly restrict certain traffic to and from a Pod.
Deny policies take precedence over allow policies, regardless of whether they are a Cilium Network Policy, a Clusterwide Cilium Network Policy or even a Kubernetes Network Policy.
Similarly to “allow” policies, Pods will enter default-deny mode as soon a single policy selects it.
If multiple allow and deny policies are applied to the same pod, the following table represents the expected enforcement for that Pod:
Set of Ingress Policies Deployed to Server Pod |
||||||
Allow Policies |
Layer 7 (HTTP) |
✓ |
✓ |
✓ |
✓ |
|
Layer 4 (80/TCP) |
✓ |
✓ |
✓ |
✓ |
||
Layer 4 (81/TCP) |
✓ |
✓ |
✓ |
✓ |
||
Layer 3 (Pod: Client) |
✓ |
✓ |
✓ |
✓ |
||
Deny Policies |
Layer 4 (80/TCP) |
✓ |
✓ |
✓ |
||
Layer 3 (Pod: Client) |
✓ |
✓ |
||||
Result for Traffic Connections (Allowed / Denied) |
||||||
Client → Server |
curl server:81 |
Allowed |
Allowed |
Denied |
Denied |
Denied |
curl server:80 |
Allowed |
Denied |
Denied |
Denied |
Denied |
|
ping server |
Allowed |
Allowed |
Denied |
Denied |
Denied |
If we pick the second column in the above table, the bottom section shows the forwarding behaviour for a policy that selects curl or ping traffic between the client and server:
Curl to port 81 is allowed because there is an allow policy on port 81, and no deny policy on that port;
Curl to port 80 is denied because there is a deny policy on that port;
Ping to the server is allowed because there is a Layer 3 allow policy and no deny.
The following policy will deny ingress from “world” on all namespaces on all Pods managed by Cilium. Existing inter-cluster policies will still be allowed as this policy is allowing traffic from everywhere except from “world”.
apiVersion: "cilium.io/v2"
kind: CiliumClusterwideNetworkPolicy
metadata:
name: "external-lockdown"
spec:
endpointSelector: {}
ingressDeny:
- fromEntities:
- "world"
ingress:
- fromEntities:
- "all"
Deny policies do not support: policy enforcement at L7, i.e., specifically
denying an URL and toFQDNs
, i.e., specifically denying traffic to a specific
domain name.
Previous limitations and known issues
For Cilium versions prior to 1.14 deny-policies for peers outside the cluster sometimes did not work because of GitHub issue 15198. Make sure that you are using version 1.14 or later if you are relying on deny policies to manage external traffic to your cluster.
Host Policies
Host policies take the form of a CiliumClusterwideNetworkPolicy with a Node Selector instead of an Endpoint Selector. Host policies can have layer 3 and layer 4 rules on both ingress and egress. They cannot have layer 7 rules.
Host policies apply to all the nodes selected by their Node Selector. In each selected node, they apply only to the host namespace, including host-networking pods. They therefore don’t apply to communications between non-host-networking pods and locations outside of the cluster.
Installation of Host Policies requires the addition of the following helm
flags when installing Cilium:
--set devices='{interface}'
whereinterface
refers to the network device Cilium is configured on such aseth0
. Omitting this option leads Cilium to auto-detect what interface the host firewall applies to.--set hostFirewall.enabled=true
The following policy will allow ingress traffic for any node with the label
type=ingress-worker
on TCP ports 22, 6443 (kube-apiserver), 2379 (etcd) and 4240
(health checks), as well as UDP port 8472 (VXLAN).
Replace the port:
value with ports used in your environment.
apiVersion: "cilium.io/v2"
kind: CiliumClusterwideNetworkPolicy
metadata:
name: "lock-down-ingress-worker-node"
spec:
description: "Allow a minimum set of required ports on ingress of worker nodes"
nodeSelector:
matchLabels:
type: ingress-worker
ingress:
- fromEntities:
- remote-node
- health
- toPorts:
- ports:
- port: "6443"
protocol: TCP
- port: "22"
protocol: TCP
- port: "2379"
protocol: TCP
- port: "4240"
protocol: TCP
- port: "8472"
protocol: UDP
- port: "REMOVE_ME_AFTER_DOUBLE_CHECKING_PORTS"
protocol: TCP
Troubleshooting Host Policies
If you’re having troubles with Host Policies please ensure the helm
options
listed above were applied during installation. To verify that your policy has
been applied, you can run kubectl get CiliumClusterwideNetworkPolicy -o yaml
to validate the policy was accepted.
If policies don’t seem to be applied to your nodes, verify the nodeSelector
is labeled correctly in your environment. In the example configuration, you can
run kubectl get nodes -o wide|grep type=ingress-worker
to verify labels
match the policy.
You can verify the policy was applied by running kubectl exec -n $CILIUM_NAMESPACE cilium-xxxx -- cilium policy get
for the Cilium agent pod. Verify that the host is selected by the policy using
cilium endpoint list
and look for the endpoint with reserved:host
as the
label and ensure that policy is enabled in the selected direction. Ensure the
traffic is arriving on the device visible on the NodePort
field of the
cilium status list
output. Use cilium monitor
with --related-to
and
the endpoint ID of the reserved:host
endpoint to view traffic.