[PATCH][SMB3.1.1] Send new netname negotiate context

[Steve French <smfrench@gmail.com>]

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Add new SMB3.1.1 netname negotiate context (only sent in request, no
response context to parse).  See MS-SMB2 2.2.3.1.4

-- 
Thanks,

Steve

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From d5e9271bcc7edc233628e43e523d7826c82eb316 Mon Sep 17 00:00:00 2001
From: Steve French <stfrench@microsoft.com>
Date: Tue, 25 Jun 2019 04:39:51 -0500
Subject: [PATCH] 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>
---
 fs/cifs/smb2pdu.c | 25 +++++++++++++++++++++++--
 fs/cifs/smb2pdu.h |  6 ++++++
 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 23524fe947de..6428574963df 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 {
-- 
2.20.1