Merge branch 'for-3.10' of git://linux-nfs.org/~bfields/linux

Pull nfsd changes from J Bruce Fields:
 "Highlights include:

   - Some more DRC cleanup and performance work from Jeff Layton

   - A gss-proxy upcall from Simo Sorce: currently krb5 mounts to the
     server using credentials from Active Directory often fail due to
     limitations of the svcgssd upcall interface.  This replacement
     lifts those limitations.  The existing upcall is still supported
     for backwards compatibility.

   - More NFSv4.1 support: at this point, if a user with a current
     client who upgrades from 4.0 to 4.1 should see no regressions.  In
     theory we do everything a 4.1 server is required to do.  Patches
     for a couple minor exceptions are ready for 3.11, and with those
     and some more testing I'd like to turn 4.1 on by default in 3.11."

Fix up semantic conflict as per Stephen Rothwell and linux-next:

Commit 030d794bf498 ("SUNRPC: Use gssproxy upcall for server RPCGSS
authentication") adds two new users of "PDE(inode)->data", but we're
supposed to use "PDE_DATA(inode)" instead since commit d9dda78bad87
("procfs: new helper - PDE_DATA(inode)").

The old PDE() macro is no longer available since commit c30480b92cf4
("proc: Make the PROC_I() and PDE() macros internal to procfs")

* 'for-3.10' of git://linux-nfs.org/~bfields/linux: (60 commits)
  NFSD: SECINFO doesn't handle unsupported pseudoflavors correctly
  NFSD: Simplify GSS flavor encoding in nfsd4_do_encode_secinfo()
  nfsd: make symbol nfsd_reply_cache_shrinker static
  svcauth_gss: fix error return code in rsc_parse()
  nfsd4: don't remap EISDIR errors in rename
  svcrpc: fix gss-proxy to respect user namespaces
  SUNRPC: gssp_procedures[] can be static
  SUNRPC: define {create,destroy}_use_gss_proxy_proc_entry in !PROC case
  nfsd4: better error return to indicate SSV non-support
  nfsd: fix EXDEV checking in rename
  SUNRPC: Use gssproxy upcall for server RPCGSS authentication.
  SUNRPC: Add RPC based upcall mechanism for RPCGSS auth
  SUNRPC: conditionally return endtime from import_sec_context
  SUNRPC: allow disabling idle timeout
  SUNRPC: attempt AF_LOCAL connect on setup
  nfsd: Decode and send 64bit time values
  nfsd4: put_client_renew_locked can be static
  nfsd4: remove unused macro
  nfsd4: remove some useless code
  nfsd4: implement SEQ4_STATUS_RECALLABLE_STATE_REVOKED
  ...

2 files changed, 93 insertions, 0 deletions

diff --git a/Documentation/filesystems/nfs/00-INDEX b/Documentation/filesystems/nfs/00-INDEX
index 1716874a651e..66eb6c8c5334 100644
--- a/Documentation/filesystems/nfs/00-INDEX
+++ b/Documentation/filesystems/nfs/00-INDEX
@@ -20,3 +20,5 @@ rpc-cache.txt
         - introduction to the caching mechanisms in the sunrpc layer.
 idmapper.txt
         - information for configuring request-keys to be used by idmapper
+knfsd-rpcgss.txt
+        - Information on GSS authentication support in the NFS Server
diff --git a/Documentation/filesystems/nfs/rpc-server-gss.txt b/Documentation/filesystems/nfs/rpc-server-gss.txt
new file mode 100644
index 000000000000..716f4be8e8b3
--- /dev/null
+++ b/Documentation/filesystems/nfs/rpc-server-gss.txt
@@ -0,0 +1,91 @@
+
+rpcsec_gss support for kernel RPC servers
+=========================================
+
+This document gives references to the standards and protocols used to
+implement RPCGSS authentication in kernel RPC servers such as the NFS
+server and the NFS client's NFSv4.0 callback server.  (But note that
+NFSv4.1 and higher don't require the client to act as a server for the
+purposes of authentication.)
+
+RPCGSS is specified in a few IETF documents:
+ - RFC2203 v1: http://tools.ietf.org/rfc/rfc2203.txt
+ - RFC5403 v2: http://tools.ietf.org/rfc/rfc5403.txt
+and there is a 3rd version  being proposed:
+ - http://tools.ietf.org/id/draft-williams-rpcsecgssv3.txt
+   (At draft n. 02 at the time of writing)
+
+Background
+----------
+
+The RPCGSS Authentication method describes a way to perform GSSAPI
+Authentication for NFS.  Although GSSAPI is itself completely mechanism
+agnostic, in many cases only the KRB5 mechanism is supported by NFS
+implementations.
+
+The Linux kernel, at the moment, supports only the KRB5 mechanism, and
+depends on GSSAPI extensions that are KRB5 specific.
+
+GSSAPI is a complex library, and implementing it completely in kernel is
+unwarranted. However GSSAPI operations are fundementally separable in 2
+parts:
+- initial context establishment
+- integrity/privacy protection (signing and encrypting of individual
+  packets)
+
+The former is more complex and policy-independent, but less
+performance-sensitive.  The latter is simpler and needs to be very fast.
+
+Therefore, we perform per-packet integrity and privacy protection in the
+kernel, but leave the initial context establishment to userspace.  We
+need upcalls to request userspace to perform context establishment.
+
+NFS Server Legacy Upcall Mechanism
+----------------------------------
+
+The classic upcall mechanism uses a custom text based upcall mechanism
+to talk to a custom daemon called rpc.svcgssd that is provide by the
+nfs-utils package.
+
+This upcall mechanism has 2 limitations:
+
+A) It can handle tokens that are no bigger than 2KiB
+
+In some Kerberos deployment GSSAPI tokens can be quite big, up and
+beyond 64KiB in size due to various authorization extensions attacked to
+the Kerberos tickets, that needs to be sent through the GSS layer in
+order to perform context establishment.
+
+B) It does not properly handle creds where the user is member of more
+than a few housand groups (the current hard limit in the kernel is 65K
+groups) due to limitation on the size of the buffer that can be send
+back to the kernel (4KiB).
+
+NFS Server New RPC Upcall Mechanism
+-----------------------------------
+
+The newer upcall mechanism uses RPC over a unix socket to a daemon
+called gss-proxy, implemented by a userspace program called Gssproxy.
+
+The gss_proxy RPC protocol is currently documented here:
+
+        https://fedorahosted.org/gss-proxy/wiki/ProtocolDocumentation
+
+This upcall mechanism uses the kernel rpc client and connects to the gssproxy
+userspace program over a regular unix socket. The gssproxy protocol does not
+suffer from the size limitations of the legacy protocol.
+
+Negotiating Upcall Mechanisms
+-----------------------------
+
+To provide backward compatibility, the kernel defaults to using the
+legacy mechanism.  To switch to the new mechanism, gss-proxy must bind
+to /var/run/gssproxy.sock and then write "1" to
+/proc/net/rpc/use-gss-proxy.  If gss-proxy dies, it must repeat both
+steps.
+
+Once the upcall mechanism is chosen, it cannot be changed.  To prevent
+locking into the legacy mechanisms, the above steps must be performed
+before starting nfsd.  Whoever starts nfsd can guarantee this by reading
+from /proc/net/rpc/use-gss-proxy and checking that it contains a
+"1"--the read will block until gss-proxy has done its write to the file.