server: support for read-only serial clients

Author: gjcolombo

bin/propolis-server/src/lib/serial/history_buffer.rs

@@ -53,10 +53,12 @@ impl TryFrom<&api::InstanceSerialConsoleStreamRequest> for SerialHistoryOffset {
             api::InstanceSerialConsoleStreamRequest {
                 from_start: Some(offset),
                 most_recent: None,
+                ..
             } => Ok(SerialHistoryOffset::FromStart(*offset as usize)),
             api::InstanceSerialConsoleStreamRequest {
                 from_start: None,
                 most_recent: Some(offset),
+                ..
             } => Ok(SerialHistoryOffset::MostRecent(*offset as usize)),
             _ => Err(()),
         }

bin/propolis-server/src/lib/server.rs

@@ -425,6 +425,7 @@ async fn instance_serial(
     let ctx = rqctx.context();
     let vm = ctx.vm.active_vm().await.ok_or_else(not_created_error)?;
     let serial = vm.objects().lock_shared().await.com1().clone();
+    let query = query.into_inner();
 
     // Use the default buffering paramters for the websocket configuration
     //
@@ -440,7 +441,7 @@ async fn instance_serial(
     )
     .await;
 
-    let byte_offset = SerialHistoryOffset::try_from(&query.into_inner()).ok();
+    let byte_offset = SerialHistoryOffset::try_from(&query).ok();
     if let Some(mut byte_offset) = byte_offset {
         loop {
             let (data, offset) = serial.history_vec(byte_offset, None)?;
@@ -459,7 +460,14 @@ async fn instance_serial(
     serial_mgr
         .as_ref()
         .ok_or("Instance has no serial console manager")?
-        .connect(ws_stream, crate::serial::ClientKind::ReadWrite)
+        .connect(
+            ws_stream,
+            if query.writable {
+                crate::serial::ClientKind::ReadWrite
+            } else {
+                crate::serial::ClientKind::ReadOnly
+            },
+        )
         .await;
 
     Ok(())

crates/propolis-api-types/src/lib.rs

@@ -325,6 +325,11 @@ pub struct InstanceSerialConsoleStreamRequest {
     /// recently buffered data retrieved from the instance. (See note on `from_start` about mutual
     /// exclusivity)
     pub most_recent: Option<u64>,
+    /// True if the connection should allow writing. If this option is set, any
+    /// existing writer to the serial console will be disconnected when this
+    /// client connects.
+    #[serde(default)]
+    pub writable: bool,
 }
 
 /// Control message(s) sent through the websocket to serial console clients.

openapi/propolis-server.json

@@ -265,6 +265,14 @@
               "format": "uint64",
               "minimum": 0
             }
+          },
+          {
+            "in": "query",
+            "name": "writable",
+            "description": "True if the connection should allow writing. If this option is set, any existing writer to the serial console will be disconnected when this client connects.",
+            "schema": {
+              "type": "boolean"
+            }
           }
         ],
         "responses": {