improved docs

README.md

@@ -2,6 +2,34 @@
 
 This repository is an unofficial Linux implementation of Google Nearby, forked from the official Nearby codebase. It focuses on Linux platform support for Nearby Connections, Nearby Sharing, and Nearby Presence.
 
+Status: This is still a work in progress, and there are known bugs and issues that need to be sorted out.
+
+Motivation: Google has multiple Linux implementation PRs open, but they have not been merged into the official repo. I am tired of begging maintainers, so I am maintaining this Linux-focused fork.
+
+If you spot bugs, help identifying them is appreciated. Filing issues is always welcome. If you want to contribute, please start a discussion about the guidance you need.
+
+Bazel is a terrible build system when it does not work and a pretty good one when it does. There is no in-between. The source code is unwieldy and it took me months to understand what everything does and where things go. It does not help that this is how I decided I am going to learn C++. Blessed be my naive soul.
+
+## Testing status
+
+I have tested with various setups:
+
+- Android walkie-talkie example app detects and connects over Bluetooth Classic and Wi-Fi LAN and can share data. Medium upgrade is untested or unclear.
+- Linux to Linux sharing is tested extensively so I can control the advertising and discovery environment.
+- I do not have access to the Android implementation details.
+- If you enable Quick Share visibility to Everyone on Android and run `sharing/linux` in advertising mode, it appears as a target in the Quick Share menu (promising, but not a full end-to-end validation).
+
+What is tested:
+
+- Linux to Linux sharing: advertising, discovery, and data work over Wi-Fi Direct, Wi-Fi Hotspot, Wi-Fi LAN, and Bluetooth Classic.
+- BLE advertising and discovery work, but without a data medium.
+- GATT advertising and discovery work.
+- Android to Linux Nearby Connections work for the same mediums as Linux to Linux above (Bluetooth Classic, Wi-Fi LAN, Wi-Fi Hotspot, Wi-Fi Direct).
+
+What is not tested or unknown:
+
+- Android to Linux Nearby Sharing with Quick Share end-to-end.
+
 This is not an officially supported Google product.
 
 ## What is included
@@ -48,10 +76,10 @@ The Linux platform implementation provides abstraction layers over local network
 
 | Mediums           | Advertising            | Scanning               | Data                   |
 | :---------------- | :--------------------: | :--------------------: | :--------------------: |
-| Bluetooth Classic |                        |                        | <ul><li>[x] </li></ul> |
+| Bluetooth Classic | <ul><li>[x] </li></ul> | <ul><li>[x] </li></ul> | <ul><li>[x] </li></ul> |
-| BLE (Fast)        | <ul><li>[x] </li></ul> | <ul><li>[x] </li></ul> |                        |
+| BLE (Fast)        |                        | <ul><li>[x] </li></ul> |                        |
 | BLE (GATT)        | <ul><li>[x] </li></ul> | <ul><li>[x] </li></ul> |                        |
-| BLE (Extended)    |                        |                        |                        |
+| BLE (Extended)    | <ul><li>[x] </li></ul> | <ul><li>[x] </li></ul> |                        |
 | BLE (L2CAP)       |                        |                        |                        |
 | Wi-Fi LAN         | <ul><li>[x] </li></ul> | <ul><li>[x] </li></ul> | <ul><li>[x] </li></ul> |
 | Wi-Fi Hotspot     |                        |                        | <ul><li>[x] </li></ul> |
@@ -62,6 +90,8 @@ The Linux platform implementation provides abstraction layers over local network
 | USB               |                        |                        |                        |
 | AWDL              |                        |                        |                        |
 
+Note: BLE fast advertising is not supported on Linux because Android uses separate LE random/resolvable MAC addresses per advertisement, and Linux does not currently support that. The Linux implementation uses BLE Extended advertising instead.
+
 ## Example applications
 
 - Nearby Sharing service example: `sharing/linux`