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Mohammad Waseem
Mohammad Waseem

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Overcoming Geo-Blocked Feature Testing on Linux Without Budget

#devops #linux #testing

Testing geo-restricted features presents a considerable challenge for DevOps teams, especially when working on local or budget-constrained environments. This post details a practical, cost-free approach for engineers to simulate different geographic locations on a Linux system, thereby enabling comprehensive testing of geo-blocked services and features.

Understanding the Challenge

Many online services restrict access based on specific regions, making it difficult to test features intended for various markets. Commercial VPNs and proxy services exist but often incur costs and may not be suitable for automated testing pipelines.

A Zero-Budget Solution: Leveraging DNS and IP Routing

The core of our solution involves manipulating DNS resolution and IP routing to simulate different geographic locations without external tools or paid services.

Step 1: Identify Target IP Subnets

First, gather the IP address ranges used by your target geo-location. Resources like IPGeoLocation or public databases can provide CIDR blocks for specific countries.

Step 2: Use ipset and iptables to Redirect Traffic

Linux utilities like ipset and iptables enable us to create custom routing rules that redirect traffic destined for specific IP ranges.

Create an ipset for target IPs:

sudo ipset create geo_blocked hash:net
# Example CIDR for a country, e.g., Japan
sudo ipset add geo_blocked 1.2.3.0/24
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Set up iptables rules to redirect traffic to a local proxy or drop it:

# Redirect traffic to a local proxy for testing
sudo iptables -t mangle -A OUTPUT -m set --match-set geo_blocked src -j MARK --set-mark 1

# Route marked traffic via proxy (e.g., socat or curl via SOCKS proxy)
sudo ip rule add fwmark 1 table 100
sudo ip route add local default dev lo table 100
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Step 3: Use Local Proxy or Tunnels

Configure a lightweight proxy (like socat or tinyproxy) to handle redirected requests:

# Example socat command to create a proxy
socat TCP-LISTEN:8080,fork SOCKS4A:127.0.0.1:target-server:port
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Configure your test client to route traffic through this local proxy, effectively simulating the geographic restriction.

Step 4: Automation and Repeatability

Create scripts that automate IP set updates, iptables rule application, and proxy configuration to streamline testing across different regions.

Additional Considerations

  • DNS Resolution: Supplement IP routing with DNS manipulation by overriding DNS responses for geo-sensitive domains.
  • Browser Testing: Use browser profiles or extensions to control proxy settings.
  • Verification: Regularly verify your IP mappings using services like curl ipinfo.io or whatismyip to ensure the traffic appears to originate from the desired location.

Final Thoughts

While this approach may require initial setup and validation, it provides a lightweight, cost-free method to simulate different geographies. Combining DNS modifications, IP routing, and local proxies enables reliable testing of geo-restricted features, ensuring your application can perform well globally without incurring additional expenses.

References:

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