TFTP daemon

A modern TFTP (Trivial File Transfer Protocol) server written in C++20. Implements RFC 1350.

Features

• RFC 1350 compliant: Full support for TFTP protocol (RRQ, WRQ, DATA, ACK, ERROR)
• Transfer modes: NETASCII, OCTET, and MAIL modes
• Dual-stack networking: IPv6 with IPv4 compatibility
• Concurrent sessions: Handles multiple file transfers simultaneously using async I/O
• Adaptive timeouts: RTT-based timeout adjustment for reliable transfers
• Modern C++20: Leverages coroutines, concepts, and stdexec for async operations

Quick Start

Building

# Debug build with tests
cmake --preset debug
cmake --build build/debug

# Release build (optimized)
cmake --preset release
cmake --build build/release

Installing

Install the server to your system (default prefix: /usr/local):

# Build the release version first
cmake --preset release
cmake --build build/release

# Install (may require sudo)
sudo cmake --install build/release

This installs the tftpd executable to /usr/local/bin/ by default.

Custom Install Location

To install to a custom location, set the CMAKE_INSTALL_PREFIX:

# Configure with custom prefix
cmake --preset release -DCMAKE_INSTALL_PREFIX=/opt/tftp
cmake --build build/release

# Install to custom location
sudo cmake --install build/release

Uninstalling

To remove the installed files:

# From your build directory
cat build/release/install_manifest.txt | sudo xargs rm

Alternatively, if you no longer have the build directory:

# Manual removal (adjust paths if using custom prefix)
sudo rm /usr/local/bin/tftpd

Running

# Run on default port 69 (requires root/sudo)
sudo ./build/release/bin/tftpd

# Run on custom port
./build/release/bin/tftpd -p 6969

# Set log level
./build/release/bin/tftpd -l debug -p 6969

# Set mail directory prefix
./build/release/bin/tftpd -m /var/mail -p 6969

Command-line Options

• -h, --help - Display help message
• -p, --port=<PORT> - Port to listen on (default: 69)
• -l, --log-level=<LEVEL> - Log level: critical, error, warn, info, debug (default: info)
• -m, --mail-prefix=<PATH> - Mail directory prefix for MAIL mode transfers

Testing

# Run all tests
cmake --preset debug
cmake --build build/debug
ctest --test-dir build/debug

# Run a single test executable
./build/debug/bin/test_tftp_server

# Run specific test by name pattern
./build/debug/bin/test_tftp_server --gtest_filter=TftpServer.HandleRRQ

# Generate code coverage report
cmake --build build/debug --target coverage
# View: build/debug/coverage/index.html

Dependencies

• stdexec - NVIDIA's sender/receiver async framework
• AsyncBerkeley - Async Berkeley sockets interface
• cppnet (cloudbus-net) v0.7.5 - Networking utilities
• spdlog v1.16.0 - Fast C++ logging library
• GoogleTest v1.17.0 - Testing framework (testing only)

All dependencies are automatically fetched via CPM.cmake during build.

Architecture

Built on stdexec's sender/receiver async model:

• UDP demultiplexing: Each client connection becomes an independent session
• Session management: Sessions tracked in multimap keyed by client address
• Async file I/O: Non-blocking file operations using stdexec senders
• Adaptive retransmission: Timeout adjusts based on measured round-trip time

Protocol Support

Read Requests (RRQ)

Clients can download files from the server. Files are read in 512-byte blocks and transmitted sequentially.

Write Requests (WRQ)

Clients can upload files to the server. Data is written to a temporary file first, then atomically renamed on successful completion.

Error Handling

Comprehensive error reporting with standard TFTP error codes:

• File not found (1)
• Access violation (2)
• Disk full (3)
• Illegal operation (4)
• Unknown transfer ID (5)
• File already exists (6)
• No such user (7)

Requirements

• C++20 compiler (GCC 11+, Clang 14+)
• CMake 3.28+
• Ninja build system (recommended)

License

GPL-3.0 - See source files for full license text.

Contributing

This project uses:

• clang-format for code formatting
• clang-tidy for static analysis
• GoogleTest for unit testing
• gcov/gcovr for code coverage