From 45b6cd3852949e74ea4a26e5d5e9c0eee97c3b27 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Pavel=20Filipensk=C3=BD?= <pfilipensky@samba.org>
Date: Tue, 7 Apr 2026 16:28:05 +0200
Subject: [PATCH] smbdotconf: Add "automount fs types" to smb.conf
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This adds a new global parameter "automount fs types" that allows
administrators to configure additional filesystem types that should
trigger automounting, beyond the always-supported autofs filesystem.

To enable 'samba unaware FS' automounting, add:

    automount fs types = 0x12345678

This allows e.g. ZFS snapshots in <dataset root>/.zfs/snapshot to be
mounted. To find out the magic number that is not listed
in /usr/include/linux/magic.h, run:

    stat -f -c '0x%t' /path/to/mountpoint

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15991

Signed-off-by: Pavel Filipenský <pfilipensky@samba.org>
Reviewed-by: Samuel Cabrero <scabrero@samba.org>

Autobuild-User(master): Pavel Filipensky <pfilipensky@samba.org>
Autobuild-Date(master): Mon Apr 20 19:57:42 UTC 2026 on atb-devel-224
---
 docs-xml/smbdotconf/misc/automountfstypes.xml | 24 ++++++++++++++
 source3/smbd/open.c                           | 31 +++++++++++++++++++
 2 files changed, 55 insertions(+)
 create mode 100644 docs-xml/smbdotconf/misc/automountfstypes.xml

diff --git a/docs-xml/smbdotconf/misc/automountfstypes.xml b/docs-xml/smbdotconf/misc/automountfstypes.xml
new file mode 100644
index 00000000000..4c5bc510520
--- /dev/null
+++ b/docs-xml/smbdotconf/misc/automountfstypes.xml
@@ -0,0 +1,24 @@
+<samba:parameter name="automount fs types"
+                 context="G"
+                 type="cmdlist"
+                 xmlns:samba="http://www.samba.org/samba/DTD/samba-doc">
+<description>
+	<para>This parameter specifies a list of additional filesystem magic numbers
+	that should trigger automounting when accessed.</para>
+
+	<para>The values should be specified as hexadecimal numbers (with or without
+	0x prefix), separated by spaces or commas.</para>
+
+	<para>Note: This parameter is only available on Linux systems.</para>
+
+	<para>To find the filesystem magic number for a mounted filesystem,
+	consult /usr/include/linux/magic.h or call:
+	<command>stat -f -c '0x%t' /path/to/mountpoint</command></para>
+
+	<para>Note: autofs (0x187) is always checked and does not need to be included
+	in this list.</para>
+</description>
+
+<value type="default"></value>
+<value type="example">0xA0B0C0D0 0x12345678</value>
+</samba:parameter>
diff --git a/source3/smbd/open.c b/source3/smbd/open.c
index 8a52cbd6850..c8c2a520aa4 100644
--- a/source3/smbd/open.c
+++ b/source3/smbd/open.c
@@ -42,6 +42,7 @@
 #include "locking/leases_db.h"
 #include "librpc/gen_ndr/ndr_leases_db.h"
 #include "lib/util/time_basic.h"
+#include "lib/util/smb_strtox.h"
 #include "source3/smbd/dir.h"
 
 #if defined(HAVE_LINUX_MAGIC_H)
@@ -877,6 +878,8 @@ static bool fsp_is_automount_mountpoint(struct files_struct *fsp, int old_fd)
 #if defined(HAVE_FSTATFS) && defined(HAVE_LINUX_MAGIC_H)
 	struct statfs sbuf = {};
 	int ret;
+	const char **fs_types_list = NULL;
+	int i;
 
 	if (!S_ISDIR(fsp->fsp_name->st.st_ex_mode)) {
 		return false;
@@ -890,6 +893,34 @@ static bool fsp_is_automount_mountpoint(struct files_struct *fsp, int old_fd)
 	if (sbuf.f_type == AUTOFS_SUPER_MAGIC) {
 		return true;
 	}
+
+	/* Check for additional filesystem types from configuration */
+	fs_types_list = lp_automount_fs_types();
+	if (fs_types_list == NULL) {
+		return false;
+	}
+
+	for (i = 0; fs_types_list[i] != NULL; i++) {
+		unsigned long long fs_type_val;
+		int error = 0;
+
+		fs_type_val = smb_strtoull(fs_types_list[i],
+					   NULL,
+					   0,
+					   &error,
+					   SMB_STR_FULL_STR_CONV);
+		if (error != 0) {
+			DBG_WARNING(
+				"Invalid value in 'automount fs types': %s\n",
+				fs_types_list[i]);
+			continue;
+		}
+
+		if (sbuf.f_type == fs_type_val) {
+			return true;
+		}
+	}
+
 	return false;
 #else
 	return false;
-- 
2.47.3