Traffic Policy

warning

Traffic Policy is currently in preview. Breaking changes may occur at any time with no notice, including changes to the structure of policy documents, the behaviors of policies, and the pricing of this feature.

Overview

This module enables you to assign a policy to your endpoints by defining a set of rules for the on_tcp_connect traffic management phase. These rules allow you to influence and control traffic to your upstream service.

Traffic Policy rules are composed of expressions that filter the traffic on which they are applicable and actions that should take effect.

Example Usage

Agent CLI

ngrok tcp 22 --traffic-policy-file /path/to/policy.yml

policy.yml

on_tcp_connect:
  - name: "LimitToKnownIPs"
    expressions:
      - "conn.client_ip != '8.8.8.8'"
      - "conn.client_ip != '9.9.9.9'"
    actions:
      - type: deny

Agent Config

tunnels:
  example:
    proto: tcp
    addr: 22
    traffic_policy:
      on_tcp_connect:
        - name: DenyTrafficOutsideUS
          expressions:
            - "conn.geo.country_code != 'US'"
          actions:
            - type: deny
        - name: "LogRequestsFromKnownIP"
          expressions:
            - "conn.client_ip == '110.0.0.1'"
          actions:
            - type: log
              config:
                metadata:
                  event: "known-ip",
                  data: "110.0.0.1"

SSH

info

Traffic Policy is not configurable via SSH

Go

import (
  "context"
  "net"

  "golang.ngrok.com/ngrok"
  "golang.ngrok.com/ngrok/config"
)

func ngrokListener(ctx context.Context) (net.Listener, error) {
  return ngrok.Listen(ctx,
    config.TCPEndpoint(
      config.WithTrafficPolicy(getPolicyFromFile()),
    ),
    ngrok.WithAuthtokenFromEnv(),
  )
}

func getPolicyFromFile() string {
	b, _ := os.ReadFile("./policy.yaml")
	return string(b)
}

info

Traffic Policies can be defined in json or yaml!

policy.json

{
	"on_tcp_connect": [
		{
			"name": "DenyTrafficOutsideUS",
			"expressions": ["conn.Geo.CountryCode != 'US'"],
			"actions": [
				{
					"type": "deny"
				}
			]
		},
		{
			"name": "LogRequestsFromKnownIP",
			"expressions": ["conn.ClientIP == '110.0.0.1"],
			"actions": [
				{
					"type": "log",
					"config": {
						"metadata": {
							"event": "known-ip",
							"data": "110.0.0.1"
						}
					}
				}
			]
		}
	]
}

policy.yaml

---
on_tcp_connect:
  - name: DenyTrafficOutsideUS
    expressions:
      - conn.Geo.CountryCode != 'US'
    actions:
      - type: deny
  - name: LogRequestsFromKnownIP
    expressions:
      - conn.ClientIP == '110.0.0.1
    actions:
      - type: log
        config:
          metadata:
            event: known-ip
            data: 110.0.0.1

Go Package Docs:

• https://pkg.go.dev/golang.ngrok.com/ngrok/config#WithTrafficPolicy

Javascript

const ngrok = require("@ngrok/ngrok");
const fs = require("fs");

(async function () {
	const listener = await ngrok.forward({
		addr: 8080,
		proto: "tcp",
		authtoken_from_env: true,
		traffic_policy: fs.readFileSync("/path/to/policy.json", "utf8"),
	});

	console.log(`Ingress established at: ${listener.url()}`);
})();

info

Traffic Policies can be defined in json or yaml!

policy.json

{
	"on_tcp_connect": [
		{
			"name": "DenyTrafficOutsideUS",
			"expressions": ["conn.Geo.CountryCode != 'US'"],
			"actions": [
				{
					"type": "deny"
				}
			]
		},
		{
			"name": "LogRequestsFromKnownIP",
			"expressions": ["conn.ClientIP == '110.0.0.1"],
			"actions": [
				{
					"type": "log",
					"config": {
						"metadata": {
							"event": "known-ip",
							"data": "110.0.0.1"
						}
					}
				}
			]
		}
	]
}

policy.yaml

---
on_tcp_connect:
  - name: DenyTrafficOutsideUS
    expressions:
      - conn.Geo.CountryCode != 'US'
    actions:
      - type: deny
  - name: LogRequestsFromKnownIP
    expressions:
      - conn.ClientIP == '110.0.0.1
    actions:
      - type: log
        config:
          metadata:
            event: known-ip
            data: 110.0.0.1

Javascript SDK Docs:

• https://ngrok.github.io/ngrok-javascript/classes/TcpListenerBuilder.html#trafficPolicy

Python

with open('/path/to/policy.json') as f:
        policy = json.load(f)
        listener = await session.http_endpoint().traffic_policy(policy).listen()

info

Traffic Policies can be defined in json or yaml!

policy.json

{
	"on_tcp_connect": [
		{
			"name": "DenyTrafficOutsideUS",
			"expressions": ["conn.Geo.CountryCode != 'US'"],
			"actions": [
				{
					"type": "deny"
				}
			]
		},
		{
			"name": "LogRequestsFromKnownIP",
			"expressions": ["conn.ClientIP == '110.0.0.1"],
			"actions": [
				{
					"type": "log",
					"config": {
						"metadata": {
							"event": "known-ip",
							"data": "110.0.0.1"
						}
					}
				}
			]
		}
	]
}

policy.yaml

---
on_tcp_connect:
  - name: DenyTrafficOutsideUS
    expressions:
      - conn.Geo.CountryCode != 'US'
    actions:
      - type: deny
  - name: LogRequestsFromKnownIP
    expressions:
      - conn.ClientIP == '110.0.0.1
    actions:
      - type: log
        config:
          metadata:
            event: known-ip
            data: 110.0.0.1

Python SDK Docs:

• https://ngrok.github.io/ngrok-python/http_listener_builder.html#ngrok.HttpListenerBuilder.traffic_policy

Rust

info

Traffic Policy is coming soon via rust-sdk

Kubernetes Controller

---
apiVersion: ingress.k8s.ngrok.com/v1alpha1
kind: TCPEdge
metadata:
  name: test-edge
spec:
  hostports:
    - 7.tcp.ngrok.io:27866
  backend:
    labels:
      app: tcpedgetest
  policy:
    inbound:
      - name: "LimitToKnownIPs"
        expressions:
          - "conn.client_ip != '8.8.8.8'"
          - "conn.client_ip != '9.9.9.9'"
        actions:
          - type: deny

---
apiVersion: ingress.k8s.ngrok.com/v1alpha1
kind: Tunnel
metadata:
  name: test-tunnel
spec:
  backend:
    protocol: TCP
  forwardsTo: kubernetes.default.svc:443
  labels:
    app: tcpedgetest

Behavior

Policy rules are evaluated sequentially in the order they are configured with on_tcp_connect rules taking effect before the upstream server is reached. Whether or not the configured actions are performed is determined at runtime by the expressions.

Expression Evaluation

Traffic Policy expressions are written using the Common Expression Language (CEL). Traffic Policy expressions must evaluate to true in order for policy actions to take effect. There is no behavioral difference between adding multiple expressions to a single policy rule and having one single expression with multiple statements logically conjoined together (i.e. ["1 == 1 && 2 == 2"] is the same s ["1 == 1", "2 == 2"]).

If no expressions are specified on a traffic policy rule, its actions will always take effect.

Action Execution

If the expressions of a traffic policy rule evaluate to true, the policy's actions will be executed. If multiple actions are defined on a traffic policy rule, the actions will execute sequentially.

See actions for all available actions.

Reference

Configuration

Parameter	Description
name	Traffic Policy rules can optionally be given a name for convenience.
expressions	A list of CEL expressions that filter which traffic a policy rule will apply to.
actions	A list of actions that will execute sequentially if the associated policy rule's expressions all match on the traffic.
type	The type of action.
config	The configuration details of how an action should execute. Each action has its own configuration structure.

Edges

Traffic Policy is a TCP Edge module.

The Traffic Policy module can be configured vai the ngrok dashboard or API.

• Traffic Policy Edge Module API Resource