Re: [PATCH][smbinfo cifsutils]

[Steve French <smfrench@gmail.com>]

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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

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From da08b29a8278f49edffdd4ebe2132b74786dda6d Mon Sep 17 00:00:00 2001
From: Steve French <stfrench@microsoft.com>
Date: Fri, 29 Mar 2019 03:05:55 -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>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
---
 smbinfo.c | 87 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 87 insertions(+)

diff --git a/smbinfo.c b/smbinfo.c
index 33fca95..7cffb84 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 +968,89 @@ 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)
+
+#define MIN_SNAPSHOT_ARRAY_SIZE 16 /* See MS-SMB2 section 3.3.5.15.1 */
+
+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 */
+
+	buf = malloc(snap_inf.snapshot_array_size + MIN_SNAPSHOT_ARRAY_SIZE);
+
+	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;
+
+	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 +1101,8 @@ 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