smb3: Send netname context during negotiate protocol

See MS-SMB2 2.2.3.1.4

Allows hostname to be used by load balancers

Signed-off-by: Steve French <stfrench@microsoft.com>

2 files changed, 29 insertions, 2 deletions

diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 8e289404f6b0..34d5397a1989 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -495,6 +495,21 @@ build_encrypt_ctxt(struct smb2_encryption_neg_context *pneg_ctxt)
         pneg_ctxt->Ciphers[1] = SMB2_ENCRYPTION_AES128_CCM;
 }
 
+static unsigned int
+build_netname_ctxt(struct smb2_netname_neg_context *pneg_ctxt, char *hostname)
+{
+        struct nls_table *cp = load_nls_default();
+
+        pneg_ctxt->ContextType = SMB2_NETNAME_NEGOTIATE_CONTEXT_ID;
+
+        /* copy up to max of first 100 bytes of server name to NetName field */
+        pneg_ctxt->DataLength = cpu_to_le16(2 +
+                (2 * cifs_strtoUTF16(pneg_ctxt->NetName, hostname, 100, cp)));
+        /* context size is DataLength + minimal smb2_neg_context */
+        return DIV_ROUND_UP(le16_to_cpu(pneg_ctxt->DataLength) +
+                        sizeof(struct smb2_neg_context), 8) * 8;
+}
+
 static void
 build_posix_ctxt(struct smb2_posix_neg_context *pneg_ctxt)
 {
@@ -559,9 +574,15 @@ assemble_neg_contexts(struct smb2_negotiate_req *req,
                                 8) * 8;
                 *total_len += ctxt_len;
                 pneg_ctxt += ctxt_len;
-                req->NegotiateContextCount = cpu_to_le16(4);
+                req->NegotiateContextCount = cpu_to_le16(5);
         } else
-                req->NegotiateContextCount = cpu_to_le16(3);
+                req->NegotiateContextCount = cpu_to_le16(4);
+
+        ctxt_len = build_netname_ctxt((struct smb2_netname_neg_context *)pneg_ctxt,
+                                        server->hostname);
+        *total_len += ctxt_len;
+        pneg_ctxt += ctxt_len;
+
         build_posix_ctxt((struct smb2_posix_neg_context *)pneg_ctxt);
         *total_len += sizeof(struct smb2_posix_neg_context);
 }
diff --git a/fs/cifs/smb2pdu.h b/fs/cifs/smb2pdu.h
index e5f7e8135a39..053ec621e7b9 100644
--- a/fs/cifs/smb2pdu.h
+++ b/fs/cifs/smb2pdu.h
@@ -317,6 +317,12 @@ struct smb2_compression_capabilities_context {
  * For smb2_netname_negotiate_context_id See MS-SMB2 2.2.3.1.4.
  * Its struct simply contains NetName, an array of Unicode characters
  */
+struct smb2_netname_neg_context {
+        __le16  ContextType; /* 0x100 */
+        __le16  DataLength;
+        __le32  Reserved;
+        __le16  NetName[0]; /* hostname of target converted to UCS-2 */
+} __packed;
 
 #define POSIX_CTXT_DATA_LEN     16
 struct smb2_posix_neg_context {