system_api: Add TestHostsConnectivity D-Bus constants to system_api 1/7

Add D-Bus API constants that will be used by the TestHostsConnectivity
implementation in subsequent CLs.

Constants added:
- kTestHostsConnectivity: D-Bus method name
- Option keys: proxy, timeout, max_errors
- Proxy values: direct, direct://, system

Initially, it was expected to merge this connectivity diagnostics series
into debugd, but feedback that can be found at [1] trigger this change.

[1]
https://chromium-review.googlesource.com/c/chromiumos/platform2/+/7233159/comment/6e0c8553_f522ea6a/

BUG=b:463098734
TEST=emerge-atlas chromeos-base/system_api

Change-Id: I4ee6bdadc7f0f97917bbeed69bfb753e54e194d6
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform2/+/7527030
Commit-Queue: Maksim Sisov <msisov@igalia.com>
Reviewed-by: Andreea Costinas <acostinas@google.com>
Reviewed-by: Hugo Benichi <hugobenichi@google.com>
Tested-by: Maksim Sisov <msisov@igalia.com>
NOKEYCHECK=True
GitOrigin-RevId: ad26337ea35940ff433edc73a6c66ae2dc259a7a
1 file changed
tree: 4ef113d548aa61701d8a1adcfbf0b186eb3736b5
  1. constants/
  2. dbus/
  3. mojo/
  4. non_standard_ipc/
  5. proto/
  6. src/
  7. switches/
  8. .gitignore
  9. BUILD.gn
  10. build.rs
  11. Cargo.toml
  12. DIR_METADATA
  13. LICENSE
  14. OWNERS
  15. README.md
  16. system_api.pc
README.md

This directory (platform2/system_api) contains constants and definitions like D-Bus service names that are shared between Chromium and Chromium OS.

This directory is only for things like headers and .proto files. No implementation should be added.

When writting a .proto file make sure to use:

option optimize_for = LITE_RUNTIME;

This will force usage of a lite protobuf instead of a full/heavy weight protobuf. The browser only links against the light version, so you will get cryptic link errors about missing parts of Message if you define a protobuf here and then try to use it in Chrome. Currently CrOS links against the full protobuffer library, but that might change in the future.

When declaring a protobuf, avoid use of required unless it is exactly what you mean. “Required is Forever” and very rarely should actually be used. Consult Protocol Buffer Basics: C++ for a detailed of this issue.