The above noted error message started showing up in the controller's errors log due to a bug which involved an unintentional overwriting of a part of the packet buffer (memory) which is shared between the kernel and the Air Monitor (AM) process on the AP.
AM is a part of the SAPD process and analyzes WiFi packets by reading these from the shared buffer space. The overwriting of the shared buffer essentially causes random data to be read by AM/SAPD.
AM/SAPD derives the length of the packet to be processed from this data.
If the length read is 0, it prints error messages as below in the system and errors.log file.
sapd | AM: received frame of size 0 from driver
If the length is so large that it oversteps the boundaries of the shared buffer, the SAPD process crashes.
Traffic bursts can increase the rate of memory overwrites, and therefore the probability of a crash.
NOTES:
- The above explained bug got introduced in Aruba OS version 3.3.2.6, and it has been fixed in Aruba OS version 3.3.2.9 and later builds.
- It is highly recommended that you upgrade your controller to Aruba OS version 3.3.2.10 or higher.