Configure transparent proxying
In order to automatically intercept traffic from and to a service through a kuma-dp
data plane proxy instance, Kuma utilizes a transparent proxying using iptables
.
Transparent proxying helps with a smoother rollout of a Service Mesh to a current deployment by preserving existing service naming and as the result - avoid changes to the application code.
Kubernetes
On Kubernetes kuma-dp
leverages transparent proxying automatically via iptables
installed with kuma-init
container or CNI.
All incoming and outgoing traffic is automatically intercepted by kuma-dp
without having to change the application code.
Kuma integrates with a service naming provided by Kubernetes DNS as well as providing its own Kuma DNS for multi-zone service naming.
Universal
On Universal kuma-dp
leverages the data plane proxy specification associated to it for receiving incoming requests on a pre-defined port.
In order to enable transparent-proxy the Zone Control Plane must exist on a seperate server. Running the Zone Control Plane with Postgres does not function with transparent-proxy on the same machine.
There are several advantages for using transparent proxying in universal mode:
- Simpler Dataplane resource, as the
outbound
section becomes obsolete and can be skipped. - Universal service naming with
.mesh
DNS domain instead of explicit outbound likehttps://localhost:10001
. - Support for hostnames of your choice using VirtualOutbounds that lets you preserve existing service naming.
- Better service manageability (security, tracing).
Setting up the service host
Prerequisites:
kuma-dp
,envoy
, andcoredns
must run on the worker node – that is, the node that runs your service mesh workload.coredns
must be in the PATH so thatkuma-dp
can access it.- You can also set the location with the
--dns-coredns-path
flag tokuma-dp
.
- You can also set the location with the
Kuma comes with kumactl
executable which can help us to prepare the host. Due to the wide variety of Linux setup options, these steps may vary and may need to be adjusted for the specifics of the particular deployment.
The host that will run the kuma-dp
process in transparent proxying mode needs to be prepared with the following steps executed as root
:
-
Create a new dedicated user on the machine.
useradd -u 5678 -U kuma-dp
-
Redirect all the relevant inbound, outbound and DNS traffic to the Kuma data plane proxy (if you’re running any other services on that machine you need to adjust the comma separated lists of
--exclude-inbound-ports
and--exclude-outbound-ports
accordingly).kumactl install transparent-proxy \ --kuma-dp-user kuma-dp \ --redirect-dns \ --exclude-inbound-ports 22
Please note that this command will change the host’s iptables
rules.
The command excludes port 22
, so you can SSH to the machine without kuma-dp
running.
The changes won’t persist over restarts. You need to either add this command to your start scripts or use firewalld.
Data plane proxy resource
In transparent proxying mode, the Dataplane
resource should omit the networking.outbound
section and use networking.transparentProxying
section instead.
type: Dataplane
mesh: default
name: {{ name }}
networking:
address: {{ address }}
inbound:
- port: {{ port }}
tags:
kuma.io/service: demo-client
transparentProxying:
redirectPortInbound: 15006
redirectPortOutbound: 15001
The ports illustrated above are the default ones that kumactl install transparent-proxy
will set. These can be changed using the relevant flags to that command.
Invoking the Kuma data plane
It is important that the kuma-dp
process runs with the same system user that was passed to kumactl install transparent-proxy --kuma-dp-user
.
The service itself should run with any other user than kuma-dp
. Otherwise, it won’t be able to leverage transparent proxying.
When systemd is used, this can be done with an entry User=kuma-dp
in the [Service]
section of the service file.
When starting kuma-dp
with a script or some other automation instead, we can use runuser
with the aforementioned yaml resource as follows:
runuser -u kuma-dp -- \
/usr/bin/kuma-dp run \
--cp-address=https://<IP or hostname of CP>:5678 \
--dataplane-token-file=/kuma/token-demo \
--dataplane-file=/kuma/dpyaml-demo \
--dataplane-var name=dp-demo \
--dataplane-var address=<IP of VM> \
--dataplane-var port=<Port of the service> \
--binary-path /usr/local/bin/envoy
You can now reach the service on the same IP and port as before installing transparent proxy, but now the traffic goes through Envoy. At the same time, you can now connect to services using Kuma DNS.
firewalld support
If you run firewalld
to manage firewalls and wrap iptables, add the --store-firewalld
flag to kumactl install transparent-proxy
. This persists the relevant rules across host restarts. The changes are stored in /etc/firewalld/direct.xml
. There is no uninstall command for this feature.
Upgrades
Before upgrading to the next version of Kuma, it’s best to clean existing iptables
rules and only then replace the kumactl
binary.
You can clean the rules either by restarting the host or by running following commands
Executing these commands will remove all iptables
rules, including those created by Kuma and any other applications or services.
iptables --table nat --flush
iptables --table raw --flush
ip6tables --table nat --flush
ip6tables --table raw --flush
iptables --table nat --delete-chain
iptables --table raw --delete-chain
ip6tables --table nat --delete-chain
ip6tables --table raw --delete-chain
In the future release, kumactl
will ship with uninstall
command.
Configuration
Intercepted traffic
By default, all the traffic is intercepted by Envoy. You can exclude which ports are intercepted by Envoy with the following annotations placed on the Pod
apiVersion: apps/v1
kind: Deployment
metadata:
name: example-app
namespace: kuma-example
spec:
...
template:
metadata:
...
annotations:
# all incoming connections on ports 1234 won't be intercepted by Envoy
traffic.kuma.io/exclude-inbound-ports: "1234"
# all outgoing connections on ports 5678, 8900 won't be intercepted by Envoy
traffic.kuma.io/exclude-outbound-ports: "5678,8900"
spec:
containers:
...
You can also control this value on whole Kuma deployment with the following Kuma CP configuration
KUMA_RUNTIME_KUBERNETES_SIDECAR_TRAFFIC_EXCLUDE_INBOUND_PORTS=1234
KUMA_RUNTIME_KUBERNETES_SIDECAR_TRAFFIC_EXCLUDE_OUTBOUND_PORTS=5678,8900
Reachable Services
By default, every data plane proxy in the mesh follows every other data plane proxy. This may lead to performance problems in larger deployments of the mesh. It is highly recommended to define a list of services that your service connects to.
apiVersion: apps/v1
kind: Deployment
metadata:
name: example-app
namespace: kuma-example
spec:
...
template:
metadata:
...
annotations:
# a comma separated list of kuma.io/service values
kuma.io/transparent-proxying-reachable-services: "redis_kuma-demo_svc_6379,elastic_kuma-demo_svc_9200"
spec:
containers:
...
Reachable Backends
This works only when MeshService is enabled.
Reachable Backends provides similar functionality to reachable services, but it applies to MeshService, MeshExternalService, and MeshMultiZoneService.
By default, every data plane proxy in the mesh tracks every other data plane proxy. Configuring reachableBackends can improve performance and reduce resource utilization.
Unlike reachable services, the model for providing data in Reachable Backends is more structured.
Model
- refs: A list of all resources your application wants to track and communicate with.
- kind: The type of resource. Possible values include:
- MeshService
- MeshExternalService
- MeshMultiZoneService
- name: The name of the resource.
- namespace: (Kubernetes only) The namespace where the resource is located. When this is defined, the name is required. Only on kubernetes.
- labels: A list of labels to match on the resources (either
labels
orname
can be defined). - port: (Optional) The port of the service you want to communicate with. Works with
MeshService
andMeshMultiZoneService
- kind: The type of resource. Possible values include:
apiVersion: apps/v1
kind: Deployment
metadata:
...
spec:
...
template:
metadata:
kuma.io/reachable-backends: |
refs:
- kind: MeshService
name: redis
namespace: kuma-demo
port: 8080
- kind: MeshMulitZoneService
labels:
kuma.io/display-name: test-server
- kind: MeshExternalService
name: mes-http
namespace: kuma-system
Examples
demo-app
communicates only with redis
on port 6379
apiVersion: apps/v1
kind: Deployment
metadata:
name: demo-app
namespace: kuma-demo
spec:
...
template:
metadata:
...
annotations:
kuma.io/reachable-backends: |
refs:
- kind: MeshService
name: redis
namespace: kuma-demo
port: 6379
spec:
containers:
...
demo-app
doesn’t need to communicate with any service
apiVersion: apps/v1
kind: Deployment
metadata:
name: demo-app
namespace: kuma-demo
spec:
...
template:
metadata:
...
annotations:
kuma.io/reachable-backends: ""
spec:
containers:
...
demo-app
wants to communicate with all MeshServices in kuma-demo
namespace
apiVersion: apps/v1
kind: Deployment
metadata:
name: demo-app
namespace: kuma-demo
spec:
...
template:
metadata:
...
annotations:
kuma.io/reachable-backends: |
refs:
- kind: MeshService
labels:
k8s.kuma.io/namespace: kuma-demo
spec:
containers:
...
Transparent Proxy with eBPF (experimental)
Starting from Kuma 2.0 you can set up transparent proxy to use eBPF instead of iptables.
To use Transparent Proxy with eBPF your environment has to use Kernel >= 5.7
and have cgroup2
available
kumactl install control-plane \
--set "experimental.ebpf.enabled=true" | kubectl apply -f-