diff mbox series

[smbinfo,cifsutils]

Message ID CAH2r5mvQ+KmoBgoxT51SRMpCXZ4OFwg+B1x_SD3DFkcrUcdZQQ@mail.gmail.com (mailing list archive)
State New, archived
Headers show
Series [smbinfo,cifsutils] | expand

Commit Message

Steve French March 28, 2019, 10:05 a.m. UTC 
Patch to smbinfo tool (in cifs-utils) to allow listing previous
versions (snapshots) of an SMB3 mounted share.  Note that cifs.ko has
a mount option "snapshot=" which can be used to mount the previous
version of a share.

Sample output:

$ ./smbinfo list-snapshots /mnt/file
Number of snapshots: 5 Number of snapshots returned: 5
Snapshot list:
1) @GMT-2019.03.27-20.52.19
2) @GMT-2019.03.27-20.50.20
3) @GMT-2019.03.16-22.25.54
4) @GMT-2019.03.16-22.22.28
5) @GMT-2018.10.12-08.30.11

Comments

ronnie sahlberg March 28, 2019, 10:24 a.m. UTC | #1 
Rewieved-by me.

As this is a pretty useful addition we can add an update to the
manpage as a followup.

On Thu, Mar 28, 2019 at 8:05 PM Steve French <smfrench@gmail.com> wrote:
>
> Patch to smbinfo tool (in cifs-utils) to allow listing previous
> versions (snapshots) of an SMB3 mounted share.  Note that cifs.ko has
> a mount option "snapshot=" which can be used to mount the previous
> version of a share.
>
> Sample output:
>
> $ ./smbinfo list-snapshots /mnt/file
> Number of snapshots: 5 Number of snapshots returned: 5
> Snapshot list:
> 1) @GMT-2019.03.27-20.52.19
> 2) @GMT-2019.03.27-20.50.20
> 3) @GMT-2019.03.16-22.25.54
> 4) @GMT-2019.03.16-22.22.28
> 5) @GMT-2018.10.12-08.30.11
>
>
> --
> Thanks,
>
> Steve
David Disseldorp March 28, 2019, 4:02 p.m. UTC | #2 
On Thu, 28 Mar 2019 05:05:35 -0500, Steve French wrote:

> +	/* Now that we know the size, query the list from the server */
> +
> +	/* Make sure the buf size is big enough even to handle unexpected server behavior */
> +	buf = malloc(snap_inf.snapshot_array_size + 300);

The buffer length calculations seem pretty arbitrary here, wouldn't it
make sense to use something like the following (with a maximum limit)?
sizeof(struct smb_snapshot_array) +
	(snap_inf.number_of_snapshots * GMT_TOKEN_LEN)

Cheers, David
Steve French March 29, 2019, 8:14 a.m. UTC | #3 
As requested I changed the buffer size malloced to be more obvious -
in this case to match exactly what is returned from the first call (ie
snapshot length + the sizeof the snapshot info structure which
precedes the snapshot list, ie 16 bytes).  The snapshot array size is
12 bytes, but rounding it to 8 byte boundary causes the minimum to be
16 bytes.

On Thu, Mar 28, 2019 at 11:02 AM David Disseldorp <ddiss@suse.de> wrote:
>
> On Thu, 28 Mar 2019 05:05:35 -0500, Steve French wrote:
>
> > +     /* Now that we know the size, query the list from the server */
> > +
> > +     /* Make sure the buf size is big enough even to handle unexpected server behavior */
> > +     buf = malloc(snap_inf.snapshot_array_size + 300);
>
> The buffer length calculations seem pretty arbitrary here, wouldn't it
> make sense to use something like the following (with a maximum limit)?
> sizeof(struct smb_snapshot_array) +
>         (snap_inf.number_of_snapshots * GMT_TOKEN_LEN)
>
> Cheers, David
Steve French March 29, 2019, 6:44 p.m. UTC | #4 
Added man page update for this new smbinfo parm


On Fri, Mar 29, 2019 at 3:14 AM Steve French <smfrench@gmail.com> wrote:
>
> As requested I changed the buffer size malloced to be more obvious -
> in this case to match exactly what is returned from the first call (ie
> snapshot length + the sizeof the snapshot info structure which
> precedes the snapshot list, ie 16 bytes).  The snapshot array size is
> 12 bytes, but rounding it to 8 byte boundary causes the minimum to be
> 16 bytes.
>
> On Thu, Mar 28, 2019 at 11:02 AM David Disseldorp <ddiss@suse.de> wrote:
> >
> > On Thu, 28 Mar 2019 05:05:35 -0500, Steve French wrote:
> >
> > > +     /* Now that we know the size, query the list from the server */
> > > +
> > > +     /* Make sure the buf size is big enough even to handle unexpected server behavior */
> > > +     buf = malloc(snap_inf.snapshot_array_size + 300);
> >
> > The buffer length calculations seem pretty arbitrary here, wouldn't it
> > make sense to use something like the following (with a maximum limit)?
> > sizeof(struct smb_snapshot_array) +
> >         (snap_inf.number_of_snapshots * GMT_TOKEN_LEN)
> >
> > Cheers, David
>
>
>
> --
> Thanks,
>
> Steve
Pavel Shilovsky March 29, 2019, 7:05 p.m. UTC | #5 
Looks good, thanks.
--
Best regards,
Pavel Shilovsky

пт, 29 мар. 2019 г. в 11:44, Steve French <smfrench@gmail.com>:
>
> Added man page update for this new smbinfo parm
>
>
> On Fri, Mar 29, 2019 at 3:14 AM Steve French <smfrench@gmail.com> wrote:
> >
> > As requested I changed the buffer size malloced to be more obvious -
> > in this case to match exactly what is returned from the first call (ie
> > snapshot length + the sizeof the snapshot info structure which
> > precedes the snapshot list, ie 16 bytes).  The snapshot array size is
> > 12 bytes, but rounding it to 8 byte boundary causes the minimum to be
> > 16 bytes.
> >
> > On Thu, Mar 28, 2019 at 11:02 AM David Disseldorp <ddiss@suse.de> wrote:
> > >
> > > On Thu, 28 Mar 2019 05:05:35 -0500, Steve French wrote:
> > >
> > > > +     /* Now that we know the size, query the list from the server */
> > > > +
> > > > +     /* Make sure the buf size is big enough even to handle unexpected server behavior */
> > > > +     buf = malloc(snap_inf.snapshot_array_size + 300);
> > >
> > > The buffer length calculations seem pretty arbitrary here, wouldn't it
> > > make sense to use something like the following (with a maximum limit)?
> > > sizeof(struct smb_snapshot_array) +
> > >         (snap_inf.number_of_snapshots * GMT_TOKEN_LEN)
> > >
> > > Cheers, David
> >
> >
> >
> > --
> > Thanks,
> >
> > Steve
>
>
>
> --
> Thanks,
>
> Steve
diff mbox series

Patch

From dd4650114a9b31f210f359327735dcffdc8139d9 Mon Sep 17 00:00:00 2001
From: Steve French <stfrench@microsoft.com>
Date: Thu, 28 Mar 2019 04:58:19 -0500
Subject: [PATCH] smbinfo: Add ability to query snapshots (previous versions)

Allow listing SMB3 snapshots (previous versions of shares)

Signed-off-by: Steve French <stfrench@microsoft.com>
---
 smbinfo.c | 86 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 86 insertions(+)

diff --git a/smbinfo.c b/smbinfo.c
index 33fca95..8f6566a 100644
--- a/smbinfo.c
+++ b/smbinfo.c
@@ -89,6 +89,8 @@  usage(char *name)
 		"      Prints the security descriptor for a cifs file.\n"
 		"  quota:\n"
 		"      Prints the quota for a cifs file.\n"
+		"  list-snapshots:\n"
+		"      List the previous versions of the volume that backs this file.\n"
 		"  fsctl-getobjid:\n"
 		"      Prints the objectid of the file and GUID of the underlying volume.\n",
 		name);
@@ -966,6 +968,88 @@  quota(int f)
 	free(qi);
 }
 
+
+struct smb_snapshot_array {
+	int32_t	number_of_snapshots;
+	int32_t	number_of_snapshots_returned;
+	int32_t	snapshot_array_size;
+	char snapshot_data[0];
+};
+
+
+static void print_snapshots(struct smb_snapshot_array *psnap)
+{
+	int current_snapshot_entry = 0;
+
+	printf("Number of snapshots: %d Number of snapshots returned: %d\n",
+		psnap->number_of_snapshots,
+		psnap->number_of_snapshots_returned);
+	printf("Snapshot list:");
+
+	for (int i = 0; i < psnap->snapshot_array_size; i++) {
+		if (psnap->snapshot_data[i] == '@') {
+			current_snapshot_entry++;
+			printf("\n%d) ", current_snapshot_entry);
+		}
+		printf("%c", psnap->snapshot_data[i]);
+	}
+	printf("\n");
+}
+
+#define CIFS_ENUMERATE_SNAPSHOTS _IOR(CIFS_IOCTL_MAGIC, 6, struct smb_snapshot_array)
+
+static void
+list_snapshots(int f)
+{
+
+	struct smb_snapshot_array snap_inf;
+	struct smb_snapshot_array *buf;
+
+	/*
+	 * When first field in structure we pass in here is zero, cifs.ko can
+	 * recognize that this is the first query and that it must set the SMB3
+	 * FSCTL response buffer size (in the request) to exactly 16 bytes
+	 * (which is required by some servers to process the initial query)
+	 */
+	snap_inf.number_of_snapshots = 0;
+	snap_inf.number_of_snapshots_returned = 0;
+	snap_inf.snapshot_array_size = sizeof(struct smb_snapshot_array);
+
+	/* Query the number of snapshots so we know how much to allocate */
+	if (ioctl(f, CIFS_ENUMERATE_SNAPSHOTS, &snap_inf) < 0) {
+		fprintf(stderr, "Querying snapshots failed with %s\n", strerror(errno));
+		exit(1);
+	}
+
+	if (snap_inf.number_of_snapshots == 0)
+		return;
+
+	/* Now that we know the size, query the list from the server */
+
+	/* Make sure the buf size is big enough even to handle unexpected server behavior */
+	buf = malloc(snap_inf.snapshot_array_size + 300);
+
+	if (buf == NULL) {
+		printf("Failed, out of memory.\n");
+		exit(1);
+	}
+	/*
+	 * first parm is non-zero which allows cifs.ko to recognize that this is
+	 * the second query (it has to set response buf size larger)
+	 */
+	buf->number_of_snapshots = snap_inf.number_of_snapshots;
+
+	buf->snapshot_array_size = snap_inf.snapshot_array_size + 200;
+
+	if (ioctl(f, CIFS_ENUMERATE_SNAPSHOTS, buf) < 0) {
+		fprintf(stderr, "Querying snapshots failed with %s\n", strerror(errno));
+		exit(1);
+	}
+
+	print_snapshots(buf);
+	free(buf);
+}
+
 int main(int argc, char *argv[])
 {
 	int c;
@@ -1016,6 +1100,8 @@  int main(int argc, char *argv[])
 		secdesc(f);
 	else if (!strcmp(argv[optind], "quota"))
 		quota(f);
+	else if (!strcmp(argv[optind], "list-snapshots"))
+		list_snapshots(f);
 	else if (!strcmp(argv[1], "fsctl-getobjid"))
 		fsctlgetobjid(f);
 	else {
-- 
2.17.1