devd: Add vm_guest variable

Fetch vm_guest on startup in case we're running under a hypervisor.

Co-authored-by: eugen@
PR: 287873
Sponsored by:		Netflix

sbin/devd/devd.cc

@@ -153,6 +153,8 @@ static volatile sig_atomic_t romeo_must_die = 0;
 
 static const char *configfile = CF;
 
+static	char	vm_guest[80];
+
 static void devdlog(int priority, const char* message, ...)
 	__printflike(2, 3);
 static void event_loop(void);
@@ -867,6 +869,8 @@ process_event(char *buffer)
 	cfg.set_variable("timestamp", timestr);
 	free(timestr);
 
+	cfg.set_variable("vm_guest", vm_guest);
+
 	// Match doesn't have a device, and the format is a little
 	// different, so handle it separately.
 	switch (type) {
@@ -1322,6 +1326,7 @@ int
 main(int argc, char **argv)
 {
 	int ch;
+	size_t len;
 
 	check_devd_enabled();
 	while ((ch = getopt(argc, argv, "df:l:nq")) != -1) {
@@ -1346,6 +1351,13 @@ main(int argc, char **argv)
 		}
 	}
 
+	len = sizeof(vm_guest);
+	if (sysctlbyname("kern.vm_guest", vm_guest, &len, NULL, 0) < 0) {
+		devdlog(LOG_ERR,
+		    "sysctlnametomib(kern.vm_guest) failed: %d\n",
+		    errno);
+	}
+
 	cfg.parse();
 	if (!no_daemon && daemonize_quick) {
 		cfg.open_pidfile();