[CIFS] implement upcalls for SPNEGO blob via keyctl API

Add routines to handle upcalls to userspace via keyctl for the purpose
of getting a SPNEGO blob for a particular uid and server combination.

Clean up the Makefile a bit and set it up to only compile cifs_spnego
if CONFIG_CIFS_UPCALL is set. Also change CONFIG_CIFS_UPCALL to depend
on CONFIG_KEYS rather than CONFIG_CONNECTOR.

cifs_spnego.h defines the communications between kernel and userspace
and is intended to be shared with userspace programs.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

fs/Kconfig

@@ -2007,7 +2007,7 @@ config CIFS_EXPERIMENTAL
 config CIFS_UPCALL
 	  bool "Kerberos/SPNEGO advanced session setup (EXPERIMENTAL)"
 	  depends on CIFS_EXPERIMENTAL
-	  depends on CONNECTOR
+	  depends on KEYS
 	  help
 	    Enables an upcall mechanism for CIFS which will be used to contact
 	    userspace helper utilities to provide SPNEGO packaged Kerberos

fs/cifs/Makefile

@@ -3,4 +3,9 @@
 #
 obj-$(CONFIG_CIFS) += cifs.o
 
-cifs-objs := cifsfs.o cifssmb.o cifs_debug.o connect.o dir.o file.o inode.o link.o misc.o netmisc.o smbdes.o smbencrypt.o transport.o asn1.o md4.o md5.o cifs_unicode.o nterr.o xattr.o cifsencrypt.o fcntl.o readdir.o ioctl.o sess.o export.o cifsacl.o
+cifs-y := cifsfs.o cifssmb.o cifs_debug.o connect.o dir.o file.o inode.o \
+	  link.o misc.o netmisc.o smbdes.o smbencrypt.o transport.o asn1.o \
+	  md4.o md5.o cifs_unicode.o nterr.o xattr.o cifsencrypt.o fcntl.o \
+	  readdir.o ioctl.o sess.o export.o cifsacl.o
+
+cifs-$(CONFIG_CIFS_UPCALL) += cifs_spnego.o

fs/cifs/cifsproto.h

@@ -76,6 +76,8 @@ extern void header_assemble(struct smb_hdr *, char /* command */ ,
 extern int small_smb_init_no_tc(const int smb_cmd, const int wct,
 				struct cifsSesInfo *ses,
 				void **request_buf);
+extern struct key *cifs_get_spnego_key(struct cifsSesInfo *sesInfo,
+					const char *hostname);
 extern int CIFS_SessSetup(unsigned int xid, struct cifsSesInfo *ses,
 			     const int stage,
 			     const struct nls_table *nls_cp);