microsandbox_protocol/
message.rs

1//! Message envelope and type definitions for the agent protocol.
2
3use serde::{Deserialize, Serialize, de::DeserializeOwned};
4
5use crate::error::ProtocolResult;
6
7//--------------------------------------------------------------------------------------------------
8// Constants
9//--------------------------------------------------------------------------------------------------
10
11/// Current protocol version.
12pub const PROTOCOL_VERSION: u8 = 1;
13
14/// Frame flag: this is the last message for the given correlation ID.
15///
16/// Set on terminal message types such as `ExecExited` and `FsResponse`.
17pub const FLAG_TERMINAL: u8 = 0b0000_0001;
18
19/// Frame flag: this is the first message of a new session.
20///
21/// Set on session-initiating message types such as `ExecRequest` and `FsRequest`.
22pub const FLAG_SESSION_START: u8 = 0b0000_0010;
23
24/// Frame flag: this message requests sandbox shutdown.
25///
26/// Set on `Shutdown` messages. The sandbox-process relay uses this to trigger
27/// drain escalation (SIGTERM → SIGKILL) if the guest doesn't exit voluntarily.
28pub const FLAG_SHUTDOWN: u8 = 0b0000_0100;
29
30/// Size of the frame header fields that sit between the length prefix and the
31/// CBOR payload: `[id: u32 BE][flags: u8]` = 5 bytes.
32pub const FRAME_HEADER_SIZE: usize = 5;
33
34//--------------------------------------------------------------------------------------------------
35// Types
36//--------------------------------------------------------------------------------------------------
37
38/// The message envelope sent over the wire.
39///
40/// Each message contains a version, type, correlation ID, flags, and a CBOR payload.
41///
42/// Wire format: `[len: u32 BE][id: u32 BE][flags: u8][CBOR(v, t, p)]`
43///
44/// The `id` and `flags` fields live in the binary frame header (outside CBOR)
45/// so that relay intermediaries can route frames without CBOR parsing.
46#[derive(Debug, Clone, Serialize, Deserialize)]
47pub struct Message {
48    /// Protocol version.
49    pub v: u8,
50
51    /// Message type.
52    pub t: MessageType,
53
54    /// Correlation ID used to associate requests with responses and
55    /// to identify exec sessions.
56    ///
57    /// Serialized in the binary frame header, not in CBOR.
58    #[serde(skip)]
59    pub id: u32,
60
61    /// Frame flags computed from the message type.
62    ///
63    /// Serialized in the binary frame header, not in CBOR.
64    #[serde(skip)]
65    pub flags: u8,
66
67    /// The CBOR-encoded payload bytes.
68    #[serde(with = "serde_bytes")]
69    pub p: Vec<u8>,
70}
71
72/// Identifies the type of a protocol message.
73#[derive(Debug, Clone, PartialEq, Eq, Hash)]
74pub enum MessageType {
75    /// Guest agent is ready.
76    Ready,
77
78    /// Host requests shutdown.
79    Shutdown,
80
81    /// Host relay reports that one SDK client disconnected.
82    RelayClientDisconnected,
83
84    /// Host requests command execution.
85    ExecRequest,
86
87    /// Guest confirms command started.
88    ExecStarted,
89
90    /// Host sends stdin data.
91    ExecStdin,
92
93    /// Guest reports that a prior `ExecStdin` write to the child's
94    /// stdin failed (e.g. the child closed its read end). Non-terminal:
95    /// the session continues and may still produce stdout/stderr and
96    /// an exit code.
97    ExecStdinError,
98
99    /// Guest sends stdout data.
100    ExecStdout,
101
102    /// Guest sends stderr data.
103    ExecStderr,
104
105    /// Guest reports command exit.
106    ExecExited,
107
108    /// Guest reports command failed to spawn (binary not found,
109    /// permission denied, etc.). Distinct from `ExecExited` —
110    /// `ExecFailed` means the user code never ran. Terminal.
111    ExecFailed,
112
113    /// Host requests PTY resize.
114    ExecResize,
115
116    /// Host sends signal to process.
117    ExecSignal,
118
119    /// Host requests a filesystem operation.
120    FsRequest,
121
122    /// Guest sends a terminal filesystem response.
123    FsResponse,
124
125    /// Streaming file data chunk (bidirectional).
126    FsData,
127}
128
129//--------------------------------------------------------------------------------------------------
130// Methods
131//--------------------------------------------------------------------------------------------------
132
133impl Message {
134    /// Creates a new message with the current protocol version and raw payload bytes.
135    pub fn new(t: MessageType, id: u32, p: Vec<u8>) -> Self {
136        let flags = t.flags();
137        Self {
138            v: PROTOCOL_VERSION,
139            t,
140            id,
141            flags,
142            p,
143        }
144    }
145
146    /// Creates a new message by serializing the given payload to CBOR.
147    pub fn with_payload<T: Serialize>(
148        t: MessageType,
149        id: u32,
150        payload: &T,
151    ) -> ProtocolResult<Self> {
152        let mut p = Vec::new();
153        ciborium::into_writer(payload, &mut p)?;
154        let flags = t.flags();
155        Ok(Self {
156            v: PROTOCOL_VERSION,
157            t,
158            id,
159            flags,
160            p,
161        })
162    }
163
164    /// Deserializes the payload bytes into the given type.
165    pub fn payload<T: DeserializeOwned>(&self) -> ProtocolResult<T> {
166        Ok(ciborium::from_reader(&self.p[..])?)
167    }
168}
169
170impl MessageType {
171    /// Computes the frame flags byte for this message type.
172    pub fn flags(&self) -> u8 {
173        match self {
174            Self::ExecExited | Self::ExecFailed | Self::FsResponse => FLAG_TERMINAL,
175            Self::ExecRequest | Self::FsRequest => FLAG_SESSION_START,
176            Self::Shutdown => FLAG_SHUTDOWN,
177            _ => 0,
178        }
179    }
180
181    /// Returns the wire string representation.
182    pub fn as_str(&self) -> &'static str {
183        match self {
184            Self::Ready => "core.ready",
185            Self::Shutdown => "core.shutdown",
186            Self::RelayClientDisconnected => "core.relay.client.disconnected",
187            Self::ExecRequest => "core.exec.request",
188            Self::ExecStarted => "core.exec.started",
189            Self::ExecStdin => "core.exec.stdin",
190            Self::ExecStdinError => "core.exec.stdin.error",
191            Self::ExecStdout => "core.exec.stdout",
192            Self::ExecStderr => "core.exec.stderr",
193            Self::ExecExited => "core.exec.exited",
194            Self::ExecFailed => "core.exec.failed",
195            Self::ExecResize => "core.exec.resize",
196            Self::ExecSignal => "core.exec.signal",
197            Self::FsRequest => "core.fs.request",
198            Self::FsResponse => "core.fs.response",
199            Self::FsData => "core.fs.data",
200        }
201    }
202
203    /// Parses a wire string into a message type.
204    pub fn from_wire_str(s: &str) -> Option<Self> {
205        match s {
206            "core.ready" => Some(Self::Ready),
207            "core.shutdown" => Some(Self::Shutdown),
208            "core.relay.client.disconnected" => Some(Self::RelayClientDisconnected),
209            "core.exec.request" => Some(Self::ExecRequest),
210            "core.exec.started" => Some(Self::ExecStarted),
211            "core.exec.stdin" => Some(Self::ExecStdin),
212            "core.exec.stdin.error" => Some(Self::ExecStdinError),
213            "core.exec.stdout" => Some(Self::ExecStdout),
214            "core.exec.stderr" => Some(Self::ExecStderr),
215            "core.exec.exited" => Some(Self::ExecExited),
216            "core.exec.failed" => Some(Self::ExecFailed),
217            "core.exec.resize" => Some(Self::ExecResize),
218            "core.exec.signal" => Some(Self::ExecSignal),
219            "core.fs.request" => Some(Self::FsRequest),
220            "core.fs.response" => Some(Self::FsResponse),
221            "core.fs.data" => Some(Self::FsData),
222            _ => None,
223        }
224    }
225}
226
227//--------------------------------------------------------------------------------------------------
228// Trait Implementations
229//--------------------------------------------------------------------------------------------------
230
231impl Serialize for MessageType {
232    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
233    where
234        S: serde::Serializer,
235    {
236        serializer.serialize_str(self.as_str())
237    }
238}
239
240impl<'de> Deserialize<'de> for MessageType {
241    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
242    where
243        D: serde::Deserializer<'de>,
244    {
245        let s = String::deserialize(deserializer)?;
246        Self::from_wire_str(&s)
247            .ok_or_else(|| serde::de::Error::custom(format!("unknown message type: {s}")))
248    }
249}
250
251//--------------------------------------------------------------------------------------------------
252// Tests
253//--------------------------------------------------------------------------------------------------
254
255#[cfg(test)]
256mod tests {
257    use super::*;
258
259    #[test]
260    fn test_message_type_roundtrip() {
261        let types = [
262            (MessageType::Ready, "core.ready"),
263            (MessageType::Shutdown, "core.shutdown"),
264            (MessageType::ExecRequest, "core.exec.request"),
265            (MessageType::ExecStarted, "core.exec.started"),
266            (MessageType::ExecStdin, "core.exec.stdin"),
267            (MessageType::ExecStdinError, "core.exec.stdin.error"),
268            (MessageType::ExecStdout, "core.exec.stdout"),
269            (MessageType::ExecStderr, "core.exec.stderr"),
270            (MessageType::ExecExited, "core.exec.exited"),
271            (MessageType::ExecFailed, "core.exec.failed"),
272            (MessageType::ExecResize, "core.exec.resize"),
273            (MessageType::ExecSignal, "core.exec.signal"),
274            (MessageType::FsRequest, "core.fs.request"),
275            (MessageType::FsResponse, "core.fs.response"),
276            (MessageType::FsData, "core.fs.data"),
277        ];
278
279        for (mt, expected_str) in &types {
280            assert_eq!(mt.as_str(), *expected_str);
281            assert_eq!(MessageType::from_wire_str(expected_str).unwrap(), *mt);
282        }
283    }
284
285    #[test]
286    fn test_message_type_serde_roundtrip() {
287        let types = [
288            MessageType::Ready,
289            MessageType::Shutdown,
290            MessageType::ExecRequest,
291            MessageType::ExecStarted,
292            MessageType::ExecStdin,
293            MessageType::ExecStdinError,
294            MessageType::ExecStdout,
295            MessageType::ExecStderr,
296            MessageType::ExecExited,
297            MessageType::ExecFailed,
298            MessageType::ExecResize,
299            MessageType::ExecSignal,
300            MessageType::FsRequest,
301            MessageType::FsResponse,
302            MessageType::FsData,
303        ];
304
305        for mt in &types {
306            let mut buf = Vec::new();
307            ciborium::into_writer(mt, &mut buf).unwrap();
308            let decoded: MessageType = ciborium::from_reader(&buf[..]).unwrap();
309            assert_eq!(&decoded, mt);
310        }
311    }
312
313    #[test]
314    fn test_unknown_message_type() {
315        assert!(MessageType::from_wire_str("core.unknown").is_none());
316    }
317
318    #[test]
319    fn test_message_with_payload_roundtrip() {
320        use crate::exec::ExecExited;
321
322        let msg =
323            Message::with_payload(MessageType::ExecExited, 7, &ExecExited { code: 42 }).unwrap();
324
325        assert_eq!(msg.t, MessageType::ExecExited);
326        assert_eq!(msg.id, 7);
327        assert_eq!(msg.flags, FLAG_TERMINAL);
328
329        let payload: ExecExited = msg.payload().unwrap();
330        assert_eq!(payload.code, 42);
331    }
332
333    #[test]
334    fn test_message_type_flags() {
335        assert_eq!(MessageType::ExecExited.flags(), FLAG_TERMINAL);
336        assert_eq!(MessageType::ExecFailed.flags(), FLAG_TERMINAL);
337        assert_eq!(MessageType::FsResponse.flags(), FLAG_TERMINAL);
338        assert_eq!(MessageType::ExecRequest.flags(), FLAG_SESSION_START);
339        assert_eq!(MessageType::FsRequest.flags(), FLAG_SESSION_START);
340        assert_eq!(MessageType::Ready.flags(), 0);
341        assert_eq!(MessageType::Shutdown.flags(), FLAG_SHUTDOWN);
342        assert_eq!(MessageType::ExecStarted.flags(), 0);
343        assert_eq!(MessageType::ExecStdin.flags(), 0);
344        assert_eq!(MessageType::ExecStdout.flags(), 0);
345        assert_eq!(MessageType::ExecStderr.flags(), 0);
346        assert_eq!(MessageType::ExecResize.flags(), 0);
347        assert_eq!(MessageType::ExecSignal.flags(), 0);
348        assert_eq!(MessageType::FsData.flags(), 0);
349    }
350
351    #[test]
352    fn test_message_new_computes_flags() {
353        let msg = Message::new(MessageType::ExecRequest, 1, Vec::new());
354        assert_eq!(msg.flags, FLAG_SESSION_START);
355
356        let msg = Message::new(MessageType::ExecStdout, 1, Vec::new());
357        assert_eq!(msg.flags, 0);
358    }
359}
microsandbox_protocol/message.rs

microsandbox_protocol/
message.rs
