From: Dave Voutila <dv@sisu.io>
Subject: fix vmctl {reload,reset} hanging on socket receive
To: tech@openbsd.org
Date: Mon, 22 Sep 2025 11:43:26 -0400

As reported on tech@ [1], `vmctl {reload,reset}` currently hangs waiting
for an imsg reply from vmd's control process. Tracked this down to a bug
I introduced recently when reworking imsg handling.

In my changes, I removed IMSG_NONE as it appeared unused since it
explicitly didn't appear in the code. Apparently 0 was being used
instead to convey the same meaning. :(

This retores the IMSG_NONE value and cleans it up to be more explicit to
avoid this facepalm in the future. I guess touching proc.{c,h} never
goes without some suffering.

If testing, this requires rebuilding vmctl(8), too, as it shares headers
from vmd(8).

ok?

-dv


[1] https://marc.info/?l=openbsd-misc&m=175846285608823&w=2

diff refs/heads/master refs/heads/vmd-vmctl-reload
commit - adfd21e9d9de44ec58cb6572dda9c677e59b7964
commit + 7ff5713e159aefb00396e9ec18f2eb2252351fd0
blob - 581739abf59d3d1bf0d9e026817c955fc17e6fe8
blob + 45d39356bb9d0bc9ce2a6f026f7b1fcbdb712711
--- usr.sbin/vmd/proc.h
+++ usr.sbin/vmd/proc.h
@@ -26,6 +26,7 @@
 #define _PROC_H

 enum {
+	IMSG_NONE = 0,
 	IMSG_CTL_OK,
 	IMSG_CTL_FAIL,
 	IMSG_CTL_VERBOSE,
blob - 6132f15735b54204e3743df3bd16827a62bc74b6
blob + 627d0f3f3adbfda62025c08aa6b4ddd580dfcae0
--- usr.sbin/vmd/vmd.c
+++ usr.sbin/vmd/vmd.c
@@ -91,7 +91,7 @@ int
 vmd_dispatch_control(int fd, struct privsep_proc *p, struct imsg *imsg)
 {
 	struct privsep			*ps = p->p_ps;
-	int				 res = 0, cmd = 0, verbose;
+	int				 res = 0, cmd = IMSG_NONE, verbose;
 	unsigned int			 v = 0, flags;
 	struct vmop_create_params	 vmc;
 	struct vmop_id			 vid;
@@ -251,14 +251,13 @@ vmd_dispatch_control(int fd, struct privsep_proc *p, s
 		control_reset(&ps->ps_csock);
 		TAILQ_FOREACH(rcs, &ps->ps_rcsocks, cs_entry)
 			control_reset(rcs);
-		cmd = 0;
 		break;
 	default:
 		return (-1);
 	}

 	switch (cmd) {
-	case 0:
+	case IMSG_NONE:
 		break;
 	case IMSG_VMDOP_START_VM_RESPONSE:
 	case IMSG_VMDOP_TERMINATE_VM_RESPONSE:
blob - 8a33e351745a63401ebff65e6d301766d1f883da
blob + 08b51df37960de8964cfb2903af8a835da0b39cc
--- usr.sbin/vmd/vmm.c
+++ usr.sbin/vmd/vmm.c
@@ -95,7 +95,7 @@ int
 vmm_dispatch_parent(int fd, struct privsep_proc *p, struct imsg *imsg)
 {
 	struct privsep		*ps = p->p_ps;
-	int			 res = 0, cmd = 0, verbose;
+	int			 res = 0, cmd = IMSG_NONE, verbose;
 	struct vmd_vm		*vm = NULL;
 	struct vm_terminate_params vtp;
 	struct vmop_id		 vid;