From: dv <dv@openbsd.org>
Date: Wed, 3 Jan 2024 22:34:39 +0000 (+0000)
Subject: vmd(8): improve error messages when out of tap devices.
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=adb7c8aaef69f767192ede5920c18bdaa15201f3;p=openbsd

vmd(8): improve error messages when out of tap devices.

The logging and the (lack of) errno don't describe the actual reason
a vm fails to start when there are not enough tap(4) special files
in /dev. Improve the log message to specify the tap file in question
and set ENOENT so vmctl(8) gets something other than an undefined
errno value to report.

ok bluhm@
---

diff --git a/usr.sbin/vmd/config.c b/usr.sbin/vmd/config.c
index 3bb246a0092..e2f3679c9e2 100644
--- a/usr.sbin/vmd/config.c
+++ b/usr.sbin/vmd/config.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: config.c,v 1.72 2023/07/13 18:31:59 dv Exp $	*/
+/*	$OpenBSD: config.c,v 1.73 2024/01/03 22:34:39 dv Exp $	*/
 
 /*
  * Copyright (c) 2015 Reyk Floeter <reyk@openbsd.org>
@@ -417,7 +417,8 @@ config_setvm(struct privsep *ps, struct vmd_vm *vm, uint32_t peerid, uid_t uid)
 			s = ifname;
 		}
 		if (tapfds[i] == -1) {
-			log_warnx("%s: can't open tap %s", __func__, s);
+			ret = errno;
+			log_warnx("%s: can't open /dev/%s", __func__, s);
 			goto fail;
 		}
 		if ((vif->vif_name = strdup(s)) == NULL) {
diff --git a/usr.sbin/vmd/vmm.c b/usr.sbin/vmd/vmm.c
index b6b138a6e3f..87d200cdebb 100644
--- a/usr.sbin/vmd/vmm.c
+++ b/usr.sbin/vmd/vmm.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: vmm.c,v 1.115 2023/09/26 01:53:54 dv Exp $	*/
+/*	$OpenBSD: vmm.c,v 1.116 2024/01/03 22:34:39 dv Exp $	*/
 
 /*
  * Copyright (c) 2015 Mike Larkin <mlarkin@openbsd.org>
@@ -586,26 +586,41 @@ terminate_vm(struct vm_terminate_params *vtp)
  * Parameters
  *  ifname: a buffer of at least IF_NAMESIZE bytes.
  *
- * Returns a file descriptor to the tap node opened, or -1 if no tap
- * devices were available.
+ * Returns a file descriptor to the tap node opened or -1 if no tap devices were
+ * available, setting errno to the open(2) error.
  */
 int
 opentap(char *ifname)
 {
-	int i, fd;
+	int err = 0, i, fd;
 	char path[PATH_MAX];
 
 	for (i = 0; i < MAX_TAP; i++) {
 		snprintf(path, PATH_MAX, "/dev/tap%d", i);
+
+		errno = 0;
 		fd = open(path, O_RDWR | O_NONBLOCK);
-		if (fd != -1) {
-			snprintf(ifname, IF_NAMESIZE, "tap%d", i);
-			return (fd);
+		if (fd != -1)
+			break;
+		err = errno;
+		if (err == EBUSY) {
+			/* Busy...try next tap. */
+			continue;
+		} else if (err == ENOENT) {
+			/* Ran out of /dev/tap* special files. */
+			break;
+		} else {
+			log_warn("%s: unexpected error", __func__);
+			break;
 		}
 	}
-	strlcpy(ifname, "tap", IF_NAMESIZE);
 
-	return (-1);
+	/* Record the last opened tap device. */
+	snprintf(ifname, IF_NAMESIZE, "tap%d", i);
+
+	if (err)
+		errno = err;
+	return (fd);
 }
 
 /*