The router that ran out of memory without leaking buffers
A Linksys MX4200 bled 12-16 MB of RAM per minute and it looked exactly like an ath11k buffer leak. It wasn't. The receive rings never grew. The bug was page-frag lifetime mixing: a bounded set of buffers pinning an expanding pile of physical pages. Here is how I found the bytes, why my first traces lied, and the source fix that stopped it.