Implemented sharing datasets via SMB using libshare

Add the initial support for the 'smbshare' option using the
existing libshare infrastructure.  Because this implementation
relies on usershares samba version 3.0.23 is required.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #493

lib/libshare/smb.h

@@ -0,0 +1,49 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+
+/*
+ * Copyright (c) 2011 Turbo Fredriksson <turbo@bayour.com>.
+ */
+
+/*
+ * The maximum SMB share name seems to be 254 characters, though good
+ * references are hard to find.
+ */
+
+#define SMB_NAME_MAX 255
+#define SMB_COMMENT_MAX 255
+
+#define SHARE_DIR "/var/lib/samba/usershares"
+#define NET_CMD_PATH "/usr/bin/net"
+#define NET_CMD_ARG_HOST "127.0.0.1"
+
+typedef struct smb_share_s {
+	char name[SMB_NAME_MAX];	/* Share name */
+	char path[PATH_MAX];		/* Share path */
+	char comment[SMB_COMMENT_MAX];	/* Share's comment */
+	boolean_t guest_ok;		/* 'y' or 'n' */
+
+	struct smb_share_s *next;
+} smb_share_t;
+
+smb_share_t *smb_shares;
+
+void libshare_smb_init(void);