=== BUILD (on guest, as root) ===
$ cc -o trigger trigger.c -lpthread
BUILD_EXIT=0
$ ls -l trigger
-rwxr-xr-x  1 root  wheel  10440 Jul  1 07:13 trigger

(No warnings, no errors.  trigger.c is self-contained: it opens the raw
 disk, builds an AF_UNIX socketpair, issues DIOCRECLUSTER to attach one
 end to the kernel DMSG iocom, and writes the forged CREATE/DELETE wire
 messages to the other end.  -lpthread is for the drain helper thread
 that keeps the kernel writer from blocking on reply backpressure.)

=== ENVIRONMENT ===
DragonFly dfbsd 6.5-DEVELOPMENT DragonFly v6.5.0.1712.g89e6a-DEVELOPMENT #1: Mon Jun 29 14:18:01 UTC 2026     root@ephemeral-5c2002c44b6c:/usr/obj/usr/src/sys/X86_64_GENERIC  x86_64
cc 8.3 [DragonFly] Release/2019-02-22

kdmsg.debug: 1
LWKT thread stack = UPAGES*PAGE_SIZE = 4*4096 = 16384 bytes (no guard page)
Disk device used: /dev/vbd0  (root:operator crw-r----- ; needs root to open)
HAMMER2 root fs on vbd0s1d (hammer2 has its OWN iocom; the disk d_iocom
 is separate and is what DIOCRECLUSTER attaches to).