Add development environment setup with Docker and VS Code Dev Containers

.devcontainer/devcontainer.json

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+{
+    "name": "Yggdrasil Go Development",
+    "dockerFile": "../contrib/docker/devcontainer/Dockerfile",
+    "context": "..",
+    // Set up port forwarding for development
+    "forwardPorts": [
+        9000,
+        9001,
+        9002,
+        9003
+    ],
+    // Configure Docker run options for TUN device access
+    "runArgs": [
+        "--privileged",
+        "--cap-add=NET_ADMIN",
+        "--device=/dev/net/tun"
+    ],
+    // Configure VS Code settings and extensions
+    "customizations": {
+        "vscode": {
+            "settings": {
+                "go.toolsManagement.checkForUpdates": "local",
+                "go.useLanguageServer": true,
+                "go.gopath": "/go",
+                "go.goroot": "/usr/local/go",
+                "go.lintTool": "golangci-lint",
+                "go.lintFlags": [
+                    "--fast"
+                ],
+                "terminal.integrated.defaultProfile.linux": "zsh",
+                "editor.formatOnSave": true,
+                "go.formatTool": "goimports",
+                "go.buildOnSave": "package"
+            },
+            "extensions": [
+                "golang.Go"
+            ]
+        }
+    },
+    // Environment variables for Go module caching
+    "containerEnv": {
+        "GOCACHE": "/home/vscode/.cache/go-build",
+        "GOMODCACHE": "/home/vscode/.cache/go-mod"
+    },
+    // Post create command to set up the environment
+    "postCreateCommand": "mkdir -p /home/vscode/.cache/go-build /home/vscode/.cache/go-mod && cd /workspace && go mod download && go mod tidy",
+    // Keep the container running
+    "overrideCommand": false,
+    // Use non-root user
+    "remoteUser": "vscode",
+    // Configure container user
+    "containerUser": "vscode",
+    "updateRemoteUserUID": true,
+    // Features to install
+    "features": {
+        "ghcr.io/devcontainers/features/git:1": {},
+        "ghcr.io/devcontainers/features/github-cli:1": {}
+    }
+}

contrib/docker/devcontainer/Dockerfile

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+# Development Dockerfile for VS Code Dev Containers
+FROM golang:1.24-bullseye
+
+# Install only essential system packages
+RUN apt-get update && apt-get install -y \
+    git \
+    ca-certificates \
+    sudo \
+    zsh \
+    && apt-get clean \
+    && rm -rf /var/lib/apt/lists/*
+
+# Install Oh My Zsh for better terminal experience
+RUN sh -c "$(curl -fsSL https://raw.github.com/ohmyzsh/ohmyzsh/master/tools/install.sh)" --unattended
+
+# Install essential Go development tools only
+RUN go install golang.org/x/tools/gopls@latest \
+    && go install github.com/go-delve/delve/cmd/dlv@latest \
+    && go install golang.org/x/tools/cmd/goimports@latest \
+    && go install github.com/golangci/golangci-lint/cmd/golangci-lint@latest
+
+# Create a non-root user for development
+ARG USERNAME=vscode
+ARG USER_UID=1000
+ARG USER_GID=$USER_UID
+
+# Create user and group with proper permissions
+RUN groupadd --gid $USER_GID $USERNAME \
+    && useradd --uid $USER_UID --gid $USER_GID -m $USERNAME -s /bin/zsh \
+    && echo $USERNAME ALL=\(root\) NOPASSWD:ALL > /etc/sudoers.d/$USERNAME \
+    && chmod 0440 /etc/sudoers.d/$USERNAME
+
+# Fix Go module cache permissions
+RUN chown -R $USERNAME:$USERNAME /go/pkg/mod || true \
+    && chmod -R 755 /go/pkg/mod || true
+
+# Create default yggdrasil conf directory
+RUN mkdir -p /etc/yggdrasil \
+    && chown -R $USERNAME:$USERNAME /etc/yggdrasil
+
+# Set up the workspace with proper ownership
+WORKDIR /workspace
+RUN chown $USERNAME:$USERNAME /workspace
+
+# Copy go module files to enable dependency caching
+COPY go.mod go.sum ./
+RUN go mod download && chown -R $USERNAME:$USERNAME /workspace
+
+# Set up shell environment for vscode user
+USER $USERNAME
+ENV SHELL=/bin/zsh
+RUN echo 'export PATH=$PATH:$(go env GOPATH)/bin' >> ~/.zshrc \
+    && echo 'export GO111MODULE=on' >> ~/.zshrc \
+    && mkdir -p ~/.cache
+
+# Expose common ports that might be used by Yggdrasil
+EXPOSE 9001 9002 9003
+
+# Keep container running for dev containers
+CMD ["sleep", "infinity"] 

contrib/docker/devcontainer/Makefile

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+# Development container management
+
+.PHONY: dev-build dev-run dev-shell dev-stop dev-clean
+
+# Build development container
+dev-build:
+	docker build -f Dockerfile -t yggdrasil-dev .
+
+# Run development container with volume mounts
+dev-run:
+	docker run -it --rm \
+		--name yggdrasil-dev \
+		-v $(PWD):/workspace \
+		-v ~/.gitconfig:/home/vscode/.gitconfig:ro \
+		-p 9001:9001 \
+		-p 9002:9002 \
+		-p 9003:9003 \
+		--privileged \
+		--cap-add=NET_ADMIN \
+		yggdrasil-dev
+
+# Get shell access to running container
+dev-shell:
+	docker exec -it yggdrasil-dev /bin/zsh
+
+# Stop development container
+dev-stop:
+	docker stop yggdrasil-dev || true
+
+# Clean development artifacts
+dev-clean:
+	docker rmi yggdrasil-dev || true
+	docker system prune -f
+
+# Build and run in one command
+dev: dev-build dev-run 

contrib/docker/devcontainer/README.md

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+# Development Environment Setup
+
+This document describes how to set up a development environment for Yggdrasil using Docker and VS Code Dev Containers.
+
+## Prerequisites
+
+- Docker installed and running
+- VS Code with the "Dev Containers" extension installed
+- Git configured with your user information
+
+## Option 1: VS Code Dev Containers (Recommended)
+
+1. Open this project in VS Code
+2. When prompted, click "Reopen in Container" or:
+   - Press `Ctrl+Shift+P` (or `Cmd+Shift+P` on macOS)
+   - Type "Dev Containers: Reopen in Container"
+   - Select the option
+
+VS Code will automatically build the development container and set up the environment with:
+- Go 1.23 with all necessary tools
+- Language server (gopls)
+- Linting (golangci-lint)
+- Debugging support (delve)
+- Git integration
+- Zsh shell with Oh My Zsh
+
+## Option 2: Manual Docker Container
+
+If you prefer to use Docker directly:
+
+### Using Makefile commands:
+
+```bash
+# Build and run the development container
+make -f Makefile dev
+
+# Or build and run separately
+make -f Makefile dev-build
+make -f Makefile dev-run
+
+# Get shell access to running container
+make -f Makefile dev-shell
+
+# Stop the container
+make -f Makefile dev-stop
+
+# Clean up
+make -f Makefile dev-clean
+```
+
+### Using Docker directly:
+
+```bash
+# Build the development image
+docker build -f Dockerfile -t yggdrasil-dev .
+
+# Run the container
+docker run -it --rm \
+  --name yggdrasil-dev \
+  -v $(pwd):/workspace \
+  -v ~/.gitconfig:/home/vscode/.gitconfig:ro \
+  -p 9000:9000 \
+  -p 9001:9001 \
+  -p 9002:9002 \
+  -p 9003:9003 \
+  --privileged \
+  --cap-add=NET_ADMIN \
+  --device=/dev/net/tun \
+  yggdrasil-dev
+```
+
+## Development Features
+
+The development environment includes:
+
+- **Go Tools**: gopls, delve debugger, goimports, golangci-lint, staticcheck
+- **Editor Support**: Syntax highlighting, auto-completion, debugging
+- **Testing**: Go test runner and coverage tools
+- **Networking**: Privileged access for network interface testing
+- **Port Forwarding**: Ports 9000-9003 exposed for Yggdrasil services
+
+## Building and Testing
+
+Inside the container:
+
+```bash
+# Build the project
+./build
+
+# Run tests
+go test ./...
+
+# Generate configuration
+./yggdrasil -genconf > yggdrasil.conf
+
+# Run with configuration
+./yggdrasil -useconf yggdrasil.conf
+```
+
+## Tips
+
+1. Your local Git configuration is mounted into the container
+2. The workspace directory (`/workspace`) is mapped to your local project directory
+3. All changes made to source files are persistent on your host machine
+4. The container runs as a non-root user (`vscode`) for security
+5. Network capabilities are enabled for testing network-related features
+
+## Troubleshooting
+
+- If the container fails to start, ensure Docker has enough resources allocated
+- For network-related issues, verify that the container has the necessary privileges
+- If Go tools are missing, rebuild the container: `make -f Makefile dev-clean dev-build`