feat(balloon): add logging for malformed balloon-stats tag

Added warn logging to the decode of BalloonStats if unknown tag is
introduced. Additionally, updated integration test of BalloonStats to
fail if this warn occurs.

Signed-off-by: Aaron Lo <[email protected]>

Author: 22aronl

src/vmm/src/devices/virtio/balloon/device.rs

@@ -5,7 +5,7 @@ use std::ops::Deref;
 use std::sync::Arc;
 use std::time::Duration;
 
-use log::{error, info, warn};
+use log::{debug, error, info, warn};
 use serde::{Deserialize, Serialize};
 use utils::time::TimerFd;
 use vmm_sys_util::eventfd::EventFd;
@@ -226,9 +226,7 @@ impl BalloonStats {
             VIRTIO_BALLOON_S_DIRECT_SCAN => self.direct_scan = val,
             VIRTIO_BALLOON_S_ASYNC_RECLAIM => self.async_reclaim = val,
             VIRTIO_BALLOON_S_DIRECT_RECLAIM => self.direct_reclaim = val,
-            _ => {
-                return Err(BalloonError::MalformedPayload);
-            }
+            tag => debug!("balloon: unknown stats update tag: {tag}"),
         }
 
         Ok(())

tests/integration_tests/functional/test_balloon.py

@@ -320,6 +320,9 @@ def test_stats(uvm_plain_any):
     # Get another reading of the stats after the polling interval has passed.
     deflated_stats = test_microvm.api.balloon_stats.get().json()
 
+    # Ensure that stats don't have unknown balloon stats fields
+    assert "balloon: unknown stats update tag:" not in test_microvm.log_data
+
     # Ensure the stats reflect deflating the balloon.
     assert inflated_stats["free_memory"] < deflated_stats["free_memory"]
     assert inflated_stats["available_memory"] < deflated_stats["available_memory"]
@@ -372,6 +375,9 @@ def test_stats_update(uvm_plain_any):
     final_stats = test_microvm.api.balloon_stats.get().json()
     assert next_stats["available_memory"] != final_stats["available_memory"]
 
+    # Ensure that stats don't have unknown balloon stats fields
+    assert "balloon: unknown stats update tag:" not in test_microvm.log_data
+
 
 def test_balloon_snapshot(uvm_plain_any, microvm_factory):
     """