bhyve/snapshot: drop mkdir when creating the unix domain socket

Add /var/run/bhyve/ to BSD.var.dist so we don't have to call mkdir when
creating the unix domain socket for a given bhyve vm.

The path to the unix domain socket for a bhyve vm will now be
/var/run/bhyve/vmname instead of /var/run/bhyve/checkpoint/vmname

Move BHYVE_RUN_DIR from snapshot.c to snapshot.h so it can be shared
to bhyvectl(8).

Reviewed by: jhb
Differential Revision: https://reviews.freebsd.org/D28783

etc/mtree/BSD.var.dist

@@ -74,6 +74,8 @@
     preserve
     ..
     run
+        bhyve
+        ..
         dhclient
         ..
         ppp             gname=network mode=0770

share/man/man7/hier.7

@@ -28,7 +28,7 @@
 .\"	@(#)hier.7	8.1 (Berkeley) 6/5/93
 .\" $FreeBSD$
 .\"
-.Dd January 9, 2021
+.Dd February 22, 2021
 .Dt HIER 7
 .Os
 .Sh NAME
@@ -832,6 +832,8 @@ system information files describing various info about
 system since it was booted
 .Pp
 .Bl -tag -width Fl -compact
+.It Pa bhyve/
+bhyve vm unix domain sockets
 .It Pa ppp/
 writable by the
 .Dq network

usr.sbin/bhyve/snapshot.c

@@ -115,8 +115,6 @@ static sig_t old_winch_handler;
 #define	SNAPSHOT_CHUNK	(4 * MB)
 #define	PROG_BUF_SZ	(8192)
 
-#define	BHYVE_RUN_DIR "/var/run/bhyve"
-#define	CHECKPOINT_RUN_DIR BHYVE_RUN_DIR "/checkpoint"
 #define	MAX_VMNAME 100
 
 #define	MAX_MSG_SIZE 1024
@@ -1505,26 +1503,6 @@ checkpoint_thread(void *param)
 	return (NULL);
 }
 
-/*
- * Create directory tree to store runtime specific information:
- * i.e. UNIX sockets for IPC with bhyvectl.
- */
-static int
-make_checkpoint_dir(void)
-{
-	int err;
-
-	err = mkdir(BHYVE_RUN_DIR, 0755);
-	if (err < 0 && errno != EEXIST)
-		return (err);
-
-	err = mkdir(CHECKPOINT_RUN_DIR, 0755);
-	if (err < 0 && errno != EEXIST)
-		return (err);
-
-	return 0;
-}
-
 /*
  * Create the listening socket for IPC with bhyvectl
  */
@@ -1556,12 +1534,6 @@ init_checkpoint_thread(struct vmctx *ctx)
 		goto fail;
 	}
 
-	err = make_checkpoint_dir();
-	if (err < 0) {
-		perror("Failed to create checkpoint runtime directory");
-		goto fail;
-	}
-
 	addr.sun_family = AF_UNIX;
 
 	err = vm_get_name(ctx, vmname_buf, MAX_VMNAME - 1);
@@ -1570,8 +1542,8 @@ init_checkpoint_thread(struct vmctx *ctx)
 		goto fail;
 	}
 
-	snprintf(addr.sun_path, sizeof(addr.sun_path), "%s/%s",
-		 CHECKPOINT_RUN_DIR, vmname_buf);
+	snprintf(addr.sun_path, sizeof(addr.sun_path), "%s%s",
+		 BHYVE_RUN_DIR, vmname_buf);
 	addr.sun_len = SUN_LEN(&addr);
 	unlink(addr.sun_path);
 

usr.sbin/bhyve/snapshot.h

@@ -42,6 +42,7 @@
 #include <libxo/xo.h>
 #include <ucl.h>
 
+#define BHYVE_RUN_DIR "/var/run/bhyve/"
 #define MAX_SNAPSHOT_VMNAME 100
 
 struct vmctx;

usr.sbin/bhyvectl/bhyvectl.c

@@ -74,7 +74,6 @@ __FBSDID("$FreeBSD$");
 #define	NO_ARG		no_argument
 #define	OPT_ARG		optional_argument
 
-#define CHECKPOINT_RUN_DIR "/var/run/bhyve/checkpoint"
 #define MAX_VMNAME 100
 
 static const char *progname;
@@ -1708,7 +1707,7 @@ send_checkpoint_op_req(struct vmctx *ctx, struct checkpoint_op *op)
 		goto done;
 	}
 
-	snprintf(addr.sun_path, sizeof(addr.sun_path), "%s/%s", CHECKPOINT_RUN_DIR, vmname_buf);
+	snprintf(addr.sun_path, sizeof(addr.sun_path), "%s%s", BHYVE_RUN_DIR, vmname_buf);
 
 	if (connect(socket_fd, (struct sockaddr *)&addr,
 			sizeof(struct sockaddr_un)) != 0) {