Define ENOAUTHSERVICE to indicate "Authentication service unavailable"

As the kernel has or will have filesystems (and possibly other services) that
want to obtain authentication tokens and/or encryption data on demand (via
GSSAPI for example), it would seem useful to provide an additional error code
to indicate a problem with the lookup, rather than overloading some other error
code.

We already have EKEYREJECTED, EKEYREVOKED and EKEYEXPIRED to indicate problems
with a token that we already have, but what if the authentication server just
isn't available?

Define ENOAUTHSERVICE to indicate "Authentication service unavailable".  This
can be used to indicate, for example, that an attempt was made by request_key()
to retrieve a key, but the authentication server (e.g. a KDC) it is supposed to
contact didn't answer or that it couldn't determine the location of a suitable
server.

One way this can be used is that the user of a network filesystem could get a
TGT from the KDC and stash it in their session keyring, then the filesystem can
attempt to automatically get a ticket for accessing the filesystem - but if the
server is uncontactable then the ticket can be negatively instantiated with
KEYCTL_REJECT, giving the error to be handed to future requests as
ENOAUTHSERVICE and a small timeout so that the key will expire from the cache
and allow a retry after a short while to prevent thrashing.

I envision that this error would primarily be generated by a kernel upcall for
the kernel to then pass back to the original userspace caller.  The kernel
itself might not actually pay any attention to it, except as a hint as to
whether to retry.

Signed-off-by: David Howells <redacted>
Acked-by: Jeff Layton <redacted>
Acked-by: Steven Whitehouse <redacted>
Acked-by: Steve Dickson <redacted>
Liked-by: Simo Sorce [off-list ref]
---

 arch/alpha/include/asm/errno.h  |    2 ++
 arch/mips/include/asm/errno.h   |    1 +
 arch/parisc/include/asm/errno.h |    1 +
 arch/sparc/include/asm/errno.h  |    1 +

3 more lines

diff --git a/arch/alpha/include/asm/errno.h b/arch/alpha/include/asm/errno.h
index e5f29ca..dce5fc9 100644
--- a/arch/alpha/include/asm/errno.h
+++ b/arch/alpha/include/asm/errno.h

@@ -124,4 +124,6 @@
 
 #define EHWPOISON	139	/* Memory page has hardware error */
 
+#define	ENOAUTHSERVICE	140	/* Authentication service not available */
+
 #endif

diff --git a/arch/mips/include/asm/errno.h b/arch/mips/include/asm/errno.h
index 6dcd358..67c46bd 100644
--- a/arch/mips/include/asm/errno.h
+++ b/arch/mips/include/asm/errno.h

@@ -122,6 +122,7 @@
 #define	ERFKILL		167	/* Operation not possible due to RF-kill */
 
 #define EHWPOISON	168	/* Memory page has hardware error */
+#define	ENOAUTHSERVICE	169	/* Authentication service not available */
 
 #define EDQUOT		1133	/* Quota exceeded */
 

diff --git a/arch/parisc/include/asm/errno.h b/arch/parisc/include/asm/errno.h
index 135ad60..3a6ffcd 100644
--- a/arch/parisc/include/asm/errno.h
+++ b/arch/parisc/include/asm/errno.h

@@ -123,5 +123,6 @@
 #define	ERFKILL		256	/* Operation not possible due to RF-kill */
 
 #define EHWPOISON	257	/* Memory page has hardware error */
+#define	ENOAUTHSERVICE	258	/* Authentication service not available */
 
 #endif

diff --git a/arch/sparc/include/asm/errno.h b/arch/sparc/include/asm/errno.h
index c351aba..94a878f 100644
--- a/arch/sparc/include/asm/errno.h
+++ b/arch/sparc/include/asm/errno.h

@@ -113,5 +113,6 @@
 #define	ERFKILL		134	/* Operation not possible due to RF-kill */
 
 #define EHWPOISON	135	/* Memory page has hardware error */
+#define	ENOAUTHSERVICE	136	/* Authentication service not available */
 
 #endif

diff --git a/include/asm-generic/errno.h b/include/asm-generic/errno.h
index a1331ce..5e2b296 100644
--- a/include/asm-generic/errno.h
+++ b/include/asm-generic/errno.h

@@ -109,5 +109,6 @@
 #define ERFKILL		132	/* Operation not possible due to RF-kill */
 
 #define EHWPOISON	133	/* Memory page has hardware error */
+#define	ENOAUTHSERVICE	134	/* Authentication service not available */
 
 #endif

Now that the kernel has filesystems (and possibly other services) that want to
look up internet addresses corresponding to arbitrary hostnames retrieved from
the server, it would seem useful to provide a couple of error codes to indicate
problems with the look up, rather than overloading some other error code.

Define ENONAMESERVICE to indicate "Network name service unavailable".  This can
be used to indicate, for example, that an attempt was made by dns_query() to
make a query, but the name server (e.g. a DNS server) it is supposed to contact
didn't answer or that it couldn't determine the location of a suitable server.

Define ENAMEUNKNOWN to indicate "Network name unknown".  This can be used to
indicate, for example, that an attempt was made by dns_query() to make a query,
but the name server (e.g. a DNS server) replied indicating that it had no
matching records.

The DNS query upcall program can report these to keyctl_reject() so that cached
failed queries will respond with these errors until they expire.

I envision that these errors would primarily be generated by a kernel upcall
for the kernel to then pass back to the original userspace caller.  The kernel
itself might not actually pay any attention to them, except as hints as to
whether to retry.

I have combined the NXDOMAIN and NODATA resolver errors into ENAMEUNKNOWN.  I'm
not sure whether it's worth separating them out.  I don't see the kernel really
needing to know the difference - if any optimised handling of NODATA is to be
done (say falling back from one DNS record type to another), I would expect
that to be done in the upcall rather than in the kernel.

However, it may be worth it from the point of view of reporting to the user.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Jeff Layton <redacted>
Acked-by: Steven Whitehouse <redacted>
Acked-by: Steve Dickson <redacted>
---

 arch/alpha/include/asm/errno.h  |    2 ++
 arch/mips/include/asm/errno.h   |    2 ++
 arch/parisc/include/asm/errno.h |    2 ++

4 more lines

diff --git a/arch/alpha/include/asm/errno.h b/arch/alpha/include/asm/errno.h
index dce5fc9..a4fc77e 100644
--- a/arch/alpha/include/asm/errno.h
+++ b/arch/alpha/include/asm/errno.h

@@ -125,5 +125,7 @@
 #define EHWPOISON	139	/* Memory page has hardware error */
 
 #define	ENOAUTHSERVICE	140	/* Authentication service not available */
+#define	ENONAMESERVICE	141	/* Network name service unavailable */
+#define	ENAMEUNKNOWN	142	/* Network name unknown */
 
 #endif

diff --git a/arch/mips/include/asm/errno.h b/arch/mips/include/asm/errno.h
index 67c46bd..ac95669 100644
--- a/arch/mips/include/asm/errno.h
+++ b/arch/mips/include/asm/errno.h

@@ -123,6 +123,8 @@
 
 #define EHWPOISON	168	/* Memory page has hardware error */
 #define	ENOAUTHSERVICE	169	/* Authentication service not available */
+#define	ENONAMESERVICE	170	/* Network name service unavailable */
+#define	ENAMEUNKNOWN	171	/* Network name unknown */
 
 #define EDQUOT		1133	/* Quota exceeded */
 

diff --git a/arch/parisc/include/asm/errno.h b/arch/parisc/include/asm/errno.h
index 3a6ffcd..753cc5c 100644
--- a/arch/parisc/include/asm/errno.h
+++ b/arch/parisc/include/asm/errno.h

@@ -124,5 +124,7 @@
 
 #define EHWPOISON	257	/* Memory page has hardware error */
 #define	ENOAUTHSERVICE	258	/* Authentication service not available */
+#define	ENONAMESERVICE	259	/* Network name service unavailable */
+#define	ENAMEUNKNOWN	260	/* Network name unknown */
 
 #endif

diff --git a/arch/sparc/include/asm/errno.h b/arch/sparc/include/asm/errno.h
index 94a878f..01c9769 100644
--- a/arch/sparc/include/asm/errno.h
+++ b/arch/sparc/include/asm/errno.h

@@ -114,5 +114,7 @@
 
 #define EHWPOISON	135	/* Memory page has hardware error */
 #define	ENOAUTHSERVICE	136	/* Authentication service not available */
+#define	ENONAMESERVICE	137	/* Network name service unavailable */
+#define	ENAMEUNKNOWN	138	/* Network name unknown */
 
 #endif

diff --git a/include/asm-generic/errno.h b/include/asm-generic/errno.h
index 5e2b296..5d012c1 100644
--- a/include/asm-generic/errno.h
+++ b/include/asm-generic/errno.h

@@ -110,5 +110,7 @@
 
 #define EHWPOISON	133	/* Memory page has hardware error */
 #define	ENOAUTHSERVICE	134	/* Authentication service not available */
+#define	ENONAMESERVICE	135	/* Network name service unavailable */
+#define	ENAMEUNKNOWN	136	/* Network name unknown */
 
 #endif