csnet

csnet is a C application programming library for communicating over a SCION network. More information about SCION can be found here. csnet exposes a BSD-socket-like API to send and receive SCION packets. csnet provides similar functionalities to snet (Go), PAN (Go), JPAN (Java) and scion-rs (Rust).

Feature Summary:

• Linux, MacOS and ESP32 support
• UDP over SCION
• SCMP (ICMP for SCION)
• Explicit SCION path selection
• Path selection policies
• Automatic DNS-based end-host bootstrapping
• SCION ping tool

To get started with csnet follow the building and installation instructions below and afterward continue with the Getting Started Guide.

Requirements

Building and installing the library and examples requires CMake 3.22 or newer (download here).

All the requirements for building the library and examples are fetched automatically with CMake and installed in the workspace build directory, ensuring the rest of the system remains unaffected.

Running the examples (in ./examples) additionally requires the following:

• a running local SCION Network (see Local SCION Network Setup for setup instructions)
• some examples have additional requirements, consult the README for more information

Building the documentation (in ./docs) requires:

• doxygen (download here)
• graphviz (download here)

Building and Installation

Set up the CMake build directory in ./build-release with

cmake -DCMAKE_BUILD_TYPE=Release -DBUILD_LIB=ON -DBUILD_CMD=ON -DBUILD_EXAMPLES=ON -DBUILD_TESTS=OFF -DBUILD_DOCS=OFF -B build-release

The following options exist:

• BUILD_LIB: build the library in ./lib
• BUILD_CMD: build the command line tools in ./cmd
• BUILD_EXAMPLES: build the examples in ./examples.
• BUILD_TESTS: build the tests in ./tests. May also build the command line tools in ./cmd that are required by the tests even if DBUILD_CMD is OFF.
• BUILD_DOCS: build the docs which are output to ./docs/api.

Build everything with

cmake --build build-release

To install the library execute:

 cmake --install build-release --prefix "your installation directory"

Depending on the installation directory you might need to run the command with sudo.

The installation will produce the static libraries lib/libscion.a, lib/libnghttp2.a, lib/libz.a, lib/libprotobuf.a, lib/libcurl.a, the header file include/scion/scion.h, and the command-line tool bin/ping in your installation directory. When using the library make sure to link against all the static libraries produced by the installation.

Local SCION Network Setup

Requirements:

• Linux, MacOS or WSL
• Go 1.23 or newer (download here)

To set up a local SCION Network execute the setup script in scripts/setup-network.sh. After successfully installing it, the network can be started with sudo scripts/run-testnet.sh. Press Ctrl+C to shut down the test network.

ESP32

EPS32 specific instructions can be found here.

Library Development

Requirements

Required tools:

• protobuf and protobuf-c: Protobuf to C compiler required to generate code from .proto files to talk to a control server.
• (optionally) clang-format: Code formatter we use.

Building in Debug Mode

To build the library in debug mode set up a CMake build directory with

cmake -DCMAKE_BUILD_TYPE=Debug -DBUILD_LIB=ON -DBUILD_CMD=ON -DBUILD_EXAMPLES=ON -DBUILD_TESTS=ON -DBUILD_DOCS=ON -B build-debug

and then to build everything run

cmake --build build-debug

You can also build a specific target with the following command

cmake --build cmake-build-debug --target TARGET

where TARGET is a valid CMake target defined in the project. Examples are:

• doxygen for the documentation
• scion for the library
• ping for the ping command line tool
• udp_example for the udp.c example
• server_example for the server.c example
• etc.

Running the Tests Locally

Before running the tests locally, ensure the following requirements are met:

1. The local SCION network has been installed as explained here.
2. You have built all targets.
3. There is no local SCION network running at the moment.

To execute all the tests run:

sudo ctest --extra-verbose --output-on-failure --test-dir build-debug

To execute only the unit tests run:

sudo ctest --extra-verbose --output-on-failure -L unit --test-dir build-debug

To execute only the e2e tests run:

sudo ctest --extra-verbose --output-on-failure -L e2e --test-dir build-debug

Info: The local SCION network will automatically start before the end-to-end tests run and shut down after they complete.

Releasing a New Version

A new release of the library can be created here.

Code Quality

To automatically format the code install clang-format and run

find . -iname "*.h" -o -iname "*.c"  | xargs clang-format -i

Entire files and directories are ignored by adding them to .clang-format-ignore