Opp Repl Opp Env Integration

opp_env integration

opp_env is the OMNeT++ version-manager: it can stand up a clean (omnetpp, inet, simu5g, ...) stack on demand. opp_repl integrates by routing build and run commands through opp_env run.

Upstream reference (covered in multiple docs):

• https://github.com/omnetpp/opp_repl/blob/main/doc/omnetpp_projects.md#opp_env-integration
• https://github.com/omnetpp/opp_repl/blob/main/doc/simulation_projects.md#opp_env-integration

Opting in

Add opp_env_workspace and opp_env_project to the .opp file. BOTH the OmnetppProject and each dependent SimulationProject should point at the same opp_env workspace:

# OmnetppProject
OmnetppProject(
    name="omnetpp-6.3.0-opp_env",
    root_folder=".",
    opp_env_workspace="/home/user/opp_env",
    opp_env_project="omnetpp-6.3.0",
)

# Matching SimulationProject
SimulationProject(
    name="inet-4.6.0-opp_env",
    root_folder=".",
    omnetpp_project="omnetpp-6.3.0-opp_env",
    opp_env_workspace="/home/user/opp_env",
    opp_env_project="inet-4.6.0",
    library_folder="src",
    bin_folder="bin",
    build_types=["dynamic library"],
    dynamic_libraries=["INET"],
    ned_folders=["src", "examples", "showcases", "tutorials"],
    ini_file_folders=["examples"],
)

Templates for both files ship with opp-repl-opp-files (templates/opp_env.opp, templates/opp_env_sim.opp).

Under the hood

When a project has opp_env_workspace set, opp_repl automatically chooses the opp_env simulation runner. Every build and run goes through:

opp_env -l WARN run <opp_env_project> \
        -w <opp_env_workspace> \
        -c "<shell_cmd>"

The environment (PATH, LD_LIBRARY_PATH, __omnetpp_root_dir) is set up by opp_env just for the duration of that subprocess.

When to use opp_env routing

• You need to run old versions of INET / OMNeT++ alongside current ones without manual env juggling.
• You want reproducible-by-construction CI pipelines (opp_env fetches exact source trees on demand).
• You're sharing .opp files across machines with different OMNeT++ installs.

Pitfalls

• The first build triggers opp_env to download + install the project. It can take minutes; be patient and make sure the network is open.
• Mixing opp_env and non-opp_env projects in the same workspace works, but makes sure each SimulationProject references the matching OmnetppProject. Cross-linking an opp_env INET to a non-opp_env OMNeT++ leads to subtle PATH mismatches.
• opp_env is a separate tool with its own versioning; pip install opp_env or follow its README.

See also

• opp-repl-opp-files — descriptor templates for opp_env projects.
• opp-repl-overlay-builds — alternative way to test multiple versions side-by-side.
• opp-repl-running-simulations — runner selection logic.