1 files changed, 38 insertions, 6 deletions

diff --git a/fs/cifs/README b/fs/cifs/README
index 2bd6fe556f88..bd2343d4c6a6 100644
--- a/fs/cifs/README
+++ b/fs/cifs/README
@@ -542,10 +542,20 @@ SecurityFlags		Flags which control security negotiation and
                         hashing mechanisms (as "must use") on the other hand 
                         does not make much sense. Default flags are 
                                 0x07007 
-                        (NTLM, NTLMv2 and packet signing allowed).  Maximum 
+                        (NTLM, NTLMv2 and packet signing allowed).  The maximum 
                         allowable flags if you want to allow mounts to servers
                         using weaker password hashes is 0x37037 (lanman,
-                        plaintext, ntlm, ntlmv2, signing allowed):
+                        plaintext, ntlm, ntlmv2, signing allowed).  Some
+                        SecurityFlags require the corresponding menuconfig
+                        options to be enabled (lanman and plaintext require
+                        CONFIG_CIFS_WEAK_PW_HASH for example).  Enabling
+                        plaintext authentication currently requires also
+                        enabling lanman authentication in the security flags
+                        because the cifs module only supports sending
+                        laintext passwords using the older lanman dialect
+                        form of the session setup SMB.  (e.g. for authentication
+                        using plain text passwords, set the SecurityFlags
+                        to 0x30030):
  
                         may use packet signing                          0x00001
                         must use packet signing                         0x01001
@@ -642,8 +652,30 @@ The statistics for the number of total SMBs and oplock breaks are different in
 that they represent all for that share, not just those for which the server
 returned success.
         
-Also note that "cat /proc/fs/cifs/DebugData" will display information about 
+Also note that "cat /proc/fs/cifs/DebugData" will display information about
 the active sessions and the shares that are mounted.
-Enabling Kerberos (extended security) works when CONFIG_CIFS_EXPERIMENTAL is
-on but requires a user space helper (from the Samba project). NTLM and NTLMv2 and
-LANMAN support do not require this helper.
+
+Enabling Kerberos (extended security) works but requires version 1.2 or later
+of the helper program cifs.upcall to be present and to be configured in the
+/etc/request-key.conf file.  The cifs.upcall helper program is from the Samba
+project(http://www.samba.org). NTLM and NTLMv2 and LANMAN support do not
+require this helper. Note that NTLMv2 security (which does not require the
+cifs.upcall helper program), instead of using Kerberos, is sufficient for
+some use cases.
+
+Enabling DFS support (used to access shares transparently in an MS-DFS
+global name space) requires that CONFIG_CIFS_EXPERIMENTAL be enabled.  In
+addition, DFS support for target shares which are specified as UNC
+names which begin with host names (rather than IP addresses) requires
+a user space helper (such as cifs.upcall) to be present in order to
+translate host names to ip address, and the user space helper must also
+be configured in the file /etc/request-key.conf
+
+To use cifs Kerberos and DFS support, the Linux keyutils package should be
+installed and something like the following lines should be added to the
+/etc/request-key.conf file:
+
+create cifs.spnego * * /usr/local/sbin/cifs.upcall %k
+create dns_resolver * * /usr/local/sbin/cifs.upcall %k
+
+