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

### Before you contribute

Before we can use your code, you must sign the
[Google Individual Contributor License Agreement][gcla] (CLA), which you can do
online. The CLA is necessary mainly because you own the copyright to your
changes, even after your contribution becomes part of our codebase, so we need
your permission to use and distribute your code. We also need to be sure of
various other things—for instance that you'll tell us if you know that your
code infringes on other people's patents. You don't have to sign the CLA until
after you've submitted your code for review and a member has approved it, but
you must do it before we can put your code into our codebase. Before you start
working on a larger contribution, you should get in touch with us first through
the issue tracker with your idea so that we can help out and possibly guide you.
Coordinating up front makes it much easier to avoid frustration later on.

### Coding Guidelines
All code should conform to the [Go style guidelines][gostyle].

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/...`

`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" (this will result in a non-cgo
        binary). Use `//pkg/unet` instead.
    * `@org_golang_x_sys//unix:go_default_library` (Go import `golang.org/x/sys/unix`).
    * Generated Go protobuf packages.
    * `@com_github_golang_protobuf//proto:go_default_library` (Go import `github.com/golang/protobuf/proto`).
    * `@com_github_golang_protobuf//ptypes:go_default_library` (Go import `github.com/golang/protobuf/ptypes`).

  * `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

All changes must be submitted via [Gerrit](https://gvisor-review.googlesource.com).

All submissions, including submissions by project members, require review.
Please see these [instructions](https://gvisor-review.googlesource.com/Documentation/).

### 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]
(https://cla.developers.google.com/about/google-corporate).

[gcla]: https://cla.developers.google.com/about/google-individual
[gostyle]: https://github.com/golang/go/wiki/CodeReviewComments