system_update_committer/
fidl.rs

1// Copyright 2020 The Fuchsia Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5use anyhow::{Context, Error};
6use fidl_fuchsia_update as fupdate;
7use futures::prelude::*;
8use std::sync::Arc;
9use zx::HandleBased as _;
10
11pub struct FuchsiaUpdateFidlServer {
12    p_external: zx::EventPair,
13    wait_for_status_check: future::Shared<futures::future::BoxFuture<'static, Result<(), String>>>,
14    idle_timeout: zx::MonotonicDuration,
15}
16
17impl FuchsiaUpdateFidlServer {
18    pub fn new(
19        p_external: zx::EventPair,
20        wait_for_status_check: impl std::future::Future<Output = Result<(), String>> + Send + 'static,
21        idle_timeout: zx::MonotonicDuration,
22    ) -> Self {
23        Self {
24            p_external,
25            wait_for_status_check: wait_for_status_check.boxed().shared(),
26            idle_timeout,
27        }
28    }
29
30    /// Handle a fuchsia.update/CommitStatusProvider request stream.
31    pub async fn handle_commit_status_provider_stream(
32        self: Arc<Self>,
33        stream: fupdate::CommitStatusProviderRequestStream,
34    ) -> Result<(), Error> {
35        let (stream, unbind_if_stalled) = detect_stall::until_stalled(stream, self.idle_timeout);
36        let mut stream = std::pin::pin!(stream);
37        while let Some(request) =
38            stream.try_next().await.context("while receiving CommitStatusProvider request")?
39        {
40            let () = Self::handle_request(self.clone(), request).await?;
41        }
42
43        if let Ok(Some(server_end)) = unbind_if_stalled.await {
44            fuchsia_component::client::connect_channel_to_protocol_at::<
45                fupdate::CommitStatusProviderMarker,
46            >(server_end, "/escrow")
47            .context("escrowing stream")?;
48        }
49
50        Ok(())
51    }
52
53    async fn handle_request(
54        self: Arc<Self>,
55        req: fupdate::CommitStatusProviderRequest,
56    ) -> Result<(), Error> {
57        // The server should only unblock when either of these conditions are met:
58        // * The current configuration was already committed on boot and p_external already has
59        //   `USER_0` asserted.
60        // * The current configuration was pending on boot (p_external may or may not have `USER_0`
61        //   asserted depending on how quickly the system is committed).
62        //
63        // The common case is that the current configuration is committed on boot, so this
64        // arrangement avoids the race condition where a client (e.g. an update checker) queries
65        // the commit status right after boot, sees that `USER_0` is not yet asserted (because the
66        // system-update-committer itself is still obtaining the status from the paver) and then
67        // postpones its work (e.g. an update check), when it would have been able to continue if
68        // it had queried the commit status a couple seconds later (many clients check the
69        // instantaneous state of `USER_0` instead of waiting for it to be asserted so that they
70        // can report failure and retry later instead of blocking indefinitely).
71        //
72        // If there is an error with `put_metadata_in_happy_state`, the FIDL server will hang here
73        // indefinitely. This is acceptable because we'll Soon™ reboot on error.
74        let () = self
75            .wait_for_status_check
76            .clone()
77            .await
78            .map_err(|e| anyhow::anyhow!("while unblocking fidl server: {e}"))?;
79        let fupdate::CommitStatusProviderRequest::IsCurrentSystemCommitted { responder } = req;
80        responder
81            .send(
82                self.p_external
83                    .duplicate_handle(zx::Rights::BASIC)
84                    .context("while duplicating p_external")?,
85            )
86            .context("while sending IsCurrentSystemCommitted response")
87    }
88}
system_update_committer/fidl.rs

system_update_committer/
fidl.rs
