[PATCH v2 3/6] CIFS: implement get_dfs_refer for SMB2+

[Aurelien Aptel <aaptel-IBi9RG/b67k@public.gmane.org>]

Signed-off-by: Aurelien Aptel <aaptel-IBi9RG/b67k@public.gmane.org>
---
 fs/cifs/smb2ops.c | 72 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 fs/cifs/smb2pdu.h |  8 +++++++
 2 files changed, 80 insertions(+)

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index a44b4db..2563fe8 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -1097,6 +1097,78 @@ smb2_new_lease_key(struct cifs_fid *fid)
 	generate_random_uuid(fid->lease_key);
 }
 
+static int
+smb2_get_dfs_refer(const unsigned int xid, struct cifs_ses *ses,
+		   const char *search_name,
+		   struct dfs_info3_param **target_nodes,
+		   unsigned int *num_of_nodes,
+		   const struct nls_table *nls_codepage, int remap)
+{
+	int rc = -EINVAL;
+	__le16 *utf16_path = NULL;
+	int utf16_path_len = 0;
+	struct cifs_tcon *tcon;
+	struct fsctl_get_dfs_referral_req *dfs_req = NULL;
+	struct get_dfs_referral_rsp *dfs_rsp = NULL;
+	u32 dfs_req_size = 0, dfs_rsp_size = 0;
+
+	cifs_dbg(FYI, "smb2_get_dfs_refer path <%s>\n", search_name);
+
+	/*
+	 * Use any tcon from the current session. Here, the first one.
+	 */
+	tcon = list_first_entry(&ses->tcon_list, struct cifs_tcon, tcon_list);
+	if (!tcon)
+		goto out;
+
+	utf16_path = cifs_strndup_to_utf16(search_name, PATH_MAX,
+					   &utf16_path_len,
+					   nls_codepage, remap);
+	if (!utf16_path) {
+		rc = -ENOMEM;
+		goto out;
+	}
+
+	dfs_req_size = sizeof(*dfs_req) + utf16_path_len;
+	dfs_req = kzalloc(dfs_req_size, GFP_KERNEL);
+	if (!dfs_req) {
+		rc = -ENOMEM;
+		goto out;
+	}
+
+	/* Highest DFS referral version understood */
+	dfs_req->MaxReferralLevel = cpu_to_le16(DFS_VERSION);
+
+	/* Path to resolve in an UTF-16 null-terminated string */
+	memcpy(dfs_req->RequestFileName, utf16_path, utf16_path_len);
+
+	do {
+		rc = SMB2_ioctl(xid, tcon, NO_FILE_ID, NO_FILE_ID,
+				FSCTL_DFS_GET_REFERRALS, true /* is_fsctl */,
+				(char *)dfs_req, dfs_req_size,
+				(char **)&dfs_rsp, &dfs_rsp_size);
+	} while (rc == -EAGAIN);
+
+	if (rc) {
+		cifs_dbg(VFS, "ioctl error in smb2_get_dfs_refer rc=%d\n", rc);
+		goto out;
+	}
+
+	rc = parse_dfs_referrals(dfs_rsp, dfs_rsp_size,
+				 num_of_nodes, target_nodes,
+				 nls_codepage, remap, search_name,
+				 true /* is_unicode */);
+	if (rc) {
+		cifs_dbg(VFS, "parse error in smb2_get_dfs_refer rc=%d\n", rc);
+		goto out;
+	}
+
+ out:
+	kfree(utf16_path);
+	kfree(dfs_req);
+	kfree(dfs_rsp);
+	return rc;
+}
 #define SMB2_SYMLINK_STRUCT_SIZE \
 	(sizeof(struct smb2_err_rsp) - 1 + sizeof(struct smb2_symlink_err_rsp))
 
diff --git a/fs/cifs/smb2pdu.h b/fs/cifs/smb2pdu.h
index c03b252..18700fd 100644
--- a/fs/cifs/smb2pdu.h
+++ b/fs/cifs/smb2pdu.h
@@ -695,6 +695,14 @@ struct fsctl_get_integrity_information_rsp {
 /* Integrity flags for above */
 #define FSCTL_INTEGRITY_FLAG_CHECKSUM_ENFORCEMENT_OFF	0x00000001
 
+/* See MS-DFSC 2.2.2 */
+struct fsctl_get_dfs_referral_req {
+	__le16 MaxReferralLevel;
+	__u8 RequestFileName[];
+} __packed;
+
+/* DFS response is struct get_dfs_refer_rsp */
+
 /* See MS-SMB2 2.2.31.3 */
 struct network_resiliency_req {
 	__le32 Timeout;
-- 
2.10.2