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Country-Aware DNS over HTTPS for Optimized CDN Routing

This Cloudflare Worker script provides a DNS over HTTPS (DoH) service with intelligent ECS (EDNS Client Subnet) handling for improved CDN performance.

中文介绍

How it works:

  1. ECS Extraction: The worker extracts two sets of ECS options from URL:

    • Client IP: The actual IP address of the client making the request.
    • Alternative IP: Typically, the external IP address of a VPN connection.

  2. Dual DNS Resolution: The worker performs two DNS resolutions for each request, one using the client IP and one using the alternative IP.

  3. Intelligent Response Selection: The worker compares the IP addresses returned in both DNS responses:

    • Same Country Match: If the IP address returned using the client IP is located in the same country as the client, that response is chosen. This prioritizes local CDN nodes for optimal performance.
    • Alternative IP Response: If the client IP response doesn't match the client's country, the response obtained using the alternative IP is chosen. This ensures content delivery even when using a VPN or experiencing routing issues.

Benefits:

  • Improved CDN Performance: By intelligently selecting the best DNS response based on client location, the worker ensures requests are routed to the most optimal CDN nodes.
  • Enhanced Privacy: Utilizing DoH encrypts DNS queries, preventing eavesdropping and manipulation.
  • Seamless VPN Integration: The worker's dual resolution approach ensures uninterrupted content delivery even when using a VPN.

Deployment:

This worker is designed for deployment on the Cloudflare Workers platform. Here are the steps to deploy:

  1. Install dependencies:

    npm install

  2. （Optional）Login to Wrangler:

    npx wrangler login

  3. Download, create, and import the GeoIP database:

    You need to set following env vars before run the import script:

    export MAXMIND_ACCOUNT_ID=
export MAXMIND_LICENSE_KEY=
export CLOUDFLARE_ACCOUNT_ID=
export CLOUDFLARE_API_TOKEN=

    Note: The following permissions for cloudflare token are needed to run the script, you can visit here to create a new token:

    Account/Worker Scripts/Edit
Account/D1/Edit

    Then, run the script:

    ./import-geoip.sh

    The script will do the following tasks

    • Download the GeoLite2 Country database from MaxMind and extract it to the ./tmp directory.
    • Create a D1 database on Cloudflare and import the downloaded database into the D1 database.

  4. Configure wrangler.toml:

    mv tmp/wrangler.toml .

  5. Deploy:

    npm run deploy

DoH URL Example:

Replace doh.subdomain.workers.dev with your domain name after deploying the script to cloudflare workers.

https://doh.subdomain.workers.dev/client-ip/223.5.5.5/client-country/CN/alternative-ip/8.8.8.8/dns-query

Contributing:

Contributions are welcome! Please feel free to open issues or submit pull requests.