# Transparent Proxying

In order to interecept traffic from and to a service through a kuma-dp data plane proxy instance, Kuma utilizes a variety of patterns.

  • On Kubernetes kuma-dp leverages transparent proxying automatically via iptables or CNI, for all incoming and outgoing traffic that is automatically intercepted by kuma-dp without having to change the application code.
  • On Universal kuma-dp leverages the data plane proxy specification associated to it for receiving incoming requests on a pre-defined port, while it can leverage both transparent proxying and explicit outbound entries in the same data plane proxy specification for all outgoing traffic.

There are several advantages for using transparent proxying in universal mode:

  • Simpler Dataplane resource, as the outbound section becomes obsolete and can be skipped.
  • Uiversal service naming using .mesh DNS domain.
  • Better service manageability (security, tracing).

# Preparing the Kuma Control plane

The Kuma control plane exposes a DNS service which handles the name resolution in the .mesh DNS zone. By default it listens on port UDP/5653. For this setup we need it to listen on port UDP/53, therefore make sure that this environment variable is set before running kuma-cp: KUMA_DNS_SERVER_PORT=53.

The IP address of the host that runs Kuma Control plane will be used in the next section. Make sure to have it once, kuma-cp is started.

# Setting up the service host

The host that will run the kuma-dp process in transparent proxying mode needs to be prepared with the following steps:

  1. Create a new dedicated user on the machine.
  2. Redirect all the relevant inbound and outbound traffic to the Kuma data plane proxy.
  3. Point the DNS resolving for .mesh to the kuma-cp embedded DNS server.

Kuma comes with kumactl executable which can help us preparing 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. However, the common steps would be to execute the following commands as root:

# create a dedicated user called kuma-dp-user
$ useradd -U kuma-dp

# use kumactl
$ kumactl install transparent-proxy \
          --kuma-dp-user kuma-dp-user \
          --kuma-cp-ip <kuma-cp IP>
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Where kuma-dp-user is the name of the dedicated user that will be used to run the kuma-dp process and <kuma-cp IP> is the IP address of the Kuma control plane (kuma-cp).

Please note that this command will change both the host iptables rules as well as modify /etc/resolv.conf, while keeping a backup copy of the original file.

The command has several other options which allow to change the default inbound and outbound redirect ports, add ports for exclusion and also disable the iptables or resolve.conf modification steps. The command's help has enumerated and documented the available options.

The default settings will exclude the SSH port 22 from the redirection, thus allowing the remote access to the host to be preserved. If the host is set up to use other remote management mechanisms, use --exclude-inbound-ports to provide a comma separated list of the TCP ports that will be excluded from the redirection.

The changes will persist over restarts, so this command is needed only once. Reverting back to the original state of the host can be done by issuing kumactl uninstall transparent-proxy.

# Data plane proxy resource

In transparent proxying mode, the Dataplane resource that will be should ommit the networking.outbound section and use networking.transparentProxyingsection instead.

type: Dataplane
mesh: default
name: {{ name }}
networking:
  address: {{ address }}
  inbound:
  - port: {{ port }}
    tags:
      kuma.io/service: demo-client
  transparentProxying:
    redirectPortInbound: 15006
    redirectPortOutbound: 15001
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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.

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://172.19.0.2:5678 \
    --dataplane-token-file=/kuma/token-demo \
    --dataplane-file=/kuma/dpyaml-demo \
    --dataplane-var name=dp-demo \
    --dataplane-var address=172.19.0.4 \
    --dataplane-var port=80  \
    --binary-path /usr/local/bin/envoy
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Last Updated: 1/7/2021, 7:29:32 PM