1 files changed, 85 insertions, 2 deletions

diff --git a/fs/cifs/sess.c b/fs/cifs/sess.c
index b234407a3007..5c68b4282be9 100644
--- a/fs/cifs/sess.c
+++ b/fs/cifs/sess.c
@@ -34,15 +34,99 @@
 extern void SMBNTencrypt(unsigned char *passwd, unsigned char *c8,
 			 unsigned char *p24);
 
+/* Checks if this is the first smb session to be reconnected after
+   the socket has been reestablished (so we know whether to use vc 0).
+   Called while holding the cifs_tcp_ses_lock, so do not block */
+static bool is_first_ses_reconnect(struct cifsSesInfo *ses)
+{
+	struct list_head *tmp;
+	struct cifsSesInfo *tmp_ses;
+
+	list_for_each(tmp, &ses->server->smb_ses_list) {
+		tmp_ses = list_entry(tmp, struct cifsSesInfo,
+				     smb_ses_list);
+		if (tmp_ses->need_reconnect == false)
+			return false;
+	}
+	/* could not find a session that was already connected,
+	   this must be the first one we are reconnecting */
+	return true;
+}
+
+/*
+ *	vc number 0 is treated specially by some servers, and should be the
+ *      first one we request.  After that we can use vcnumbers up to maxvcs,
+ *	one for each smb session (some Windows versions set maxvcs incorrectly
+ *	so maxvc=1 can be ignored).  If we have too many vcs, we can reuse
+ *	any vc but zero (some servers reset the connection on vcnum zero)
+ *
+ */
+static __le16 get_next_vcnum(struct cifsSesInfo *ses)
+{
+	__u16 vcnum = 0;
+	struct list_head *tmp;
+	struct cifsSesInfo *tmp_ses;
+	__u16 max_vcs = ses->server->max_vcs;
+	__u16 i;
+	int free_vc_found = 0;
+
+	/* Quoting the MS-SMB specification: "Windows-based SMB servers set this
+	field to one but do not enforce this limit, which allows an SMB client
+	to establish more virtual circuits than allowed by this value ... but
+	other server implementations can enforce this limit." */
+	if (max_vcs < 2)
+		max_vcs = 0xFFFF;
+
+	write_lock(&cifs_tcp_ses_lock);
+	if ((ses->need_reconnect) && is_first_ses_reconnect(ses))
+			goto get_vc_num_exit;  /* vcnum will be zero */
+	for (i = ses->server->srv_count - 1; i < max_vcs; i++) {
+		if (i == 0) /* this is the only connection, use vc 0 */
+			break;
+
+		free_vc_found = 1;
+
+		list_for_each(tmp, &ses->server->smb_ses_list) {
+			tmp_ses = list_entry(tmp, struct cifsSesInfo,
+					     smb_ses_list);
+			if (tmp_ses->vcnum == i) {
+				free_vc_found = 0;
+				break; /* found duplicate, try next vcnum */
+			}
+		}
+		if (free_vc_found)
+			break; /* we found a vcnumber that will work - use it */
+	}
+
+	if (i == 0)
+		vcnum = 0; /* for most common case, ie if one smb session, use
+			      vc zero.  Also for case when no free vcnum, zero
+			      is safest to send (some clients only send zero) */
+	else if (free_vc_found == 0)
+		vcnum = 1;  /* we can not reuse vc=0 safely, since some servers
+				reset all uids on that, but 1 is ok. */
+	else
+		vcnum = i;
+	ses->vcnum = vcnum;
+get_vc_num_exit:
+	write_unlock(&cifs_tcp_ses_lock);
+
+	return le16_to_cpu(vcnum);
+}
+
 static __u32 cifs_ssetup_hdr(struct cifsSesInfo *ses, SESSION_SETUP_ANDX *pSMB)
 {
 	__u32 capabilities = 0;
 
 	/* init fields common to all four types of SessSetup */
-	/* note that header is initialized to zero in header_assemble */
+	/* Note that offsets for first seven fields in req struct are same  */
+	/*	in CIFS Specs so does not matter which of 3 forms of struct */
+	/*	that we use in next few lines                               */
+	/* Note that header is initialized to zero in header_assemble */
 	pSMB->req.AndXCommand = 0xFF;
 	pSMB->req.MaxBufferSize = cpu_to_le16(ses->server->maxBuf);
 	pSMB->req.MaxMpxCount = cpu_to_le16(ses->server->maxReq);
+	pSMB->req.VcNumber = get_next_vcnum(ses);
 
 	/* Now no need to set SMBFLG_CASELESS or obsolete CANONICAL PATH */
 
@@ -71,7 +155,6 @@ static __u32 cifs_ssetup_hdr(struct cifsSesInfo *ses, SESSION_SETUP_ANDX *pSMB)
 	if (ses->capabilities & CAP_UNIX)
 		capabilities |= CAP_UNIX;
 
-	/* BB check whether to init vcnum BB */
 	return capabilities;
 }