# Contributing

Want to contribute? Great! First, read this page.

### Contributor License Agreement

Contributions to this project must be accompanied by a Contributor License
Agreement. You (or your employer) retain the copyright to your contribution;
this simply gives us permission to use and redistribute your contributions as
part of the project. Head over to <https://cla.developers.google.com/> to see
your current agreements on file or to sign a new one.

You generally only need to submit a CLA once, so if you've already submitted one
(even if it was for a different project), you probably don't need to do it
again.

### Using GOPATH

Some editors may require the code to be structured in a `GOPATH` directory tree.
In this case, you may use the `:gopath` target to generate a directory tree with
symlinks to the original source files.

```
bazel build :gopath
```

You can then set the `GOPATH` in your editor to `bazel-bin/gopath`.

If you use this mechanism, keep in mind that the generated tree is not the
canonical source. You will still need to build and test with `bazel`. New files
will need to be added to the appropriate `BUILD` files, and the `:gopath` target
will need to be re-run to generate appropriate symlinks in the `GOPATH`
directory tree.

Dependencies can be added by using `go get`. In order to keep the `WORKSPACE`
file in sync, run `bazel run //:gazelle -- update-repos -from_file=go.mod` in
place of `go mod`.

### Coding Guidelines

All code should comply with the [style guide](g3doc/style.md). Note that code
may be automatically formatted per the guidelines when merged.

As a secure runtime, we need to maintain the safety of all of code included in
gVisor. The following rules help mitigate issues.

Definitions for the rules below:

`core`:

*   `//pkg/sentry/...`
*   Transitive dependencies in `//pkg/...`, etc.

`runsc`:

*   `//runsc/...`

Rules:

*   No cgo in `core` or `runsc`. The final binary must be a statically-linked
    pure Go binary.

*   Any files importing "unsafe" must have a name ending in `_unsafe.go`.

*   `core` may only depend on the following packages:

    *   Itself.
    *   Go standard library.
        *   Except (transitively) package "net", which would result in a cgo
            binary. Use `//pkg/unet` instead.
    *   `@org_golang_x_sys//unix:go_default_library` (Go import
        `golang.org/x/sys/unix`).
    *   `@org_golang_x_time//rate:go_default_library` (Go import
        `golang.org/x/time/rate`).
    *   `@com_github_google_btree//:go_default_library"` (Go import
        `github.com/google/btree`).
    *   Generated Go protobuf packages.
    *   `@org_golang_google_protobuf//proto:go_default_library` (Go import
        `google.golang.org/protobuf`).

*   `runsc` may only depend on the following packages:

    *   All packages allowed for `core`.
    *   `@com_github_google_subcommands//:go_default_library` (Go import
        `github.com/google/subcommands`).
    *   `@com_github_opencontainers_runtime_spec//specs_go:go_default_library`
        (Go import `github.com/opencontainers/runtime-spec/specs_go`).

### Code reviews

Before sending code reviews, run `bazel test ...` to ensure tests are passing.

Code changes are accepted via [pull request][github].

When approved, the change will be submitted by a team member and automatically
merged into the repository.

### Presubmit checks

Accessing check logs may require membership in the
[gvisor-dev mailing list][gvisor-dev-list], which is public.

### Bug IDs

Some TODOs and NOTEs sprinkled throughout the code have associated IDs of the
form `b/1234`. These correspond to bugs in our internal bug tracker. Eventually
these bugs will be moved to the GitHub Issues, but until then they can simply be
ignored.

### Build and test with Docker

Running `make dev` is a convenient way to build and install `runsc` as a Docker
runtime. The output of this command will show the runtimes installed.

You may use `make refresh` to refresh the binary after any changes. For example:

```bash
make dev
docker run --rm --runtime=my-branch --rm hello-world
make refresh
```

### The small print

Contributions made by corporations are covered by a different agreement than the
one above, the
[Software Grant and Corporate Contributor License Agreement][gccla].

[gcla]: https://cla.developers.google.com/about/google-individual
[gccla]: https://cla.developers.google.com/about/google-corporate
[github]: https://github.com/google/gvisor/compare
[gvisor-dev-list]: https://groups.google.com/forum/#!forum/gvisor-dev