Building Custom CoreDNS Solutions for Enterprise Infrastructure

Introduction

CoreDNS has revolutionized DNS services with its plugin-based architecture and cloud-native design. However, enterprise environments often require specialized configurations that go beyond standard deployments. In this post, I'll walk through implementing a custom CoreDNS solution designed specifically for wireless infrastructure, focusing on Private PGW (Packet Gateway) environments.

The Challenge

When working with telecommunications infrastructure, particularly in wireless networks, DNS services need to be more than just domain name resolution. They require:

• Prometheus metrics integration for comprehensive monitoring
• Service discovery capabilities for dynamic network topologies
• High availability and low latency for real-time communications
• Integration with internal services like Consul for service mesh architectures

Why Custom Build Over Standard Deployment?

While CoreDNS offers extensive plugin support, our wireless infrastructure presented unique requirements:

# Standard CoreDNS might not easily integrate with:
- Internal Prometheus metrics collection
- Private network service discovery
- Telecom-specific monitoring requirements
- Corporate registry and security policies

The solution was to create a custom Docker image based on CoreDNS 1.11.1 that could be tailored to our specific needs while maintaining the stability and performance of the upstream project.

Implementation Architecture

Base Image Selection

FROM coredns/coredns:1.11.1
EXPOSE 11915/tcp

Why CoreDNS 1.11.1? - Proven stability in production environments - Comprehensive plugin ecosystem - Active community support - Security updates and patches

Build System Design

The build system was designed for both development agility and production reliability:

SERVICE_NAME:=$(shell cat meta-dev.yml | grep service: -m1 | cut -d ':' -f2 | xargs)
VERSION := $(shell cat VERSION)
IMAGE := registry.internal..com/jenkins/$(SERVICE_NAME):${VERSION} build:
 docker build --cache-from ${IMAGE}:red \
 --build-arg BUILDKIT_INLINE_CACHE=1 \
 -t ${IMAGE} .

Key Design Principles: 1. Dynamic Configuration: Service names and versions extracted from YAML files 2. Build Optimization: Docker layer caching for faster builds 3. Registry Integration: Internal registry for security and compliance 4. Version Management: Semantic versioning aligned with CoreDNS releases

Configuration Management Strategy

Environment Separation

# meta-dev.yml - Development Configuration
names:
 service: project
 github: project
 bugsnag: project build:
 promote_to_dev:
 mode: always
 branch_pattern: "main|master|deploy-dev/.*" project:
 squad: core.wireless.squad
 primary_maintainer: jagannath
 secondary_maintainer: sergii

This configuration approach provides: - Clear ownership and responsibility assignment - Automated promotion based on branch patterns - Environment-specific service configurations - Integration points for monitoring and error tracking

Version Management

# VERSION file contains: 1.11.1
# Aligned with CoreDNS upstream for compatibility

Integration with Prometheus Metrics

One of the key requirements was exposing detailed DNS metrics for monitoring. The custom build enables:

# Potential CoreDNS configuration for metrics
.:53 {
 prometheus :11915
 forward . 8.8.8.8
 log
 errors
}

Benefits: - Real-time DNS query monitoring - Performance metrics collection - Integration with existing monitoring stack - Custom wireless-specific metrics

Service Discovery Integration

For wireless infrastructure, DNS services need to integrate with service discovery:

# Consul integration possibilities
consul {
 endpoint consul.service.consul:8500
}

Use Cases: - Dynamic service registration for PGW components - Health check integration - Load balancer backend updates - Network topology awareness

CI/CD Pipeline Integration

The Jenkins pipeline integration ensures reliable deployments:

@Library("github.com/team-/infra-ci-pipelines@latest") _
dockerImage {
 // Automated build, test, and deployment
}

Pipeline Features: - Automated builds on code changes - Integration with internal CI/CD infrastructure - Security scanning and compliance checks - Multi-environment deployment support

Security Considerations

Working with telecommunications infrastructure requires strict security:

1. Internal Registry: All images stored in corporate registry
2. Network Isolation: DNS service runs in isolated network segments
3. Access Control: Limited exposure with specific port configurations
4. Audit Trail: Complete build and deployment logging

Performance Optimization

Docker Build Optimization

# Build cache utilization
--cache-from ${IMAGE}:red --build-arg BUILDKIT_INLINE_CACHE=1

Resource Management

• Lightweight base image for minimal attack surface
• Optimized for DNS query latency
• Memory-efficient configuration
• CPU usage monitoring through Prometheus

Lessons Learned

1. Start with Stable Versions: Using CoreDNS 1.11.1 provided a reliable foundation
2. Automate Everything: Build, test, and deployment automation saves time and reduces errors
3. Configuration Management: YAML-based configuration provides flexibility and maintainability
4. Monitoring is Crucial: Prometheus integration was essential for operational visibility
5. Security First: Internal registries and network isolation are non-negotiable

Future Enhancements

The current implementation provides a solid foundation for future enhancements:

1. Advanced Metrics: Custom wireless-specific metrics
2. Health Checks: Kubernetes-native health check endpoints
3. Configuration Hot-Reload: Dynamic configuration updates without restarts
4. Multi-Region Support: Geographic distribution for global wireless networks
5. Enhanced Security: mTLS integration for service-to-service communication

Conclusion

Building custom CoreDNS solutions requires balancing standard practices with specific infrastructure requirements. By focusing on:

• Stable foundation (CoreDNS 1.11.1)
• Automated workflows (CI/CD integration)
• Comprehensive monitoring (Prometheus metrics)
• Security best practices (internal registries)
• Flexible configuration (YAML-based management)

We created a DNS service that meets the demanding requirements of wireless telecommunications infrastructure while maintaining the reliability and performance expected in production environments.

The key to success was not just the technical implementation, but also the operational considerations: proper documentation, clear ownership, automated testing, and comprehensive monitoring. These elements together create a maintainable and scalable DNS service that can evolve with changing infrastructure requirements.

About the Author: Jagannath S is a software engineer specializing in telecommunications infrastructure and wireless network services. Connect with me to discuss CoreDNS implementations, wireless infrastructure, or DNS service optimization.