linux-kernel - [PATCH 2/2] Define ENONAMESERVICE and ENAMEUNKNOWN to indicate name service errors

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Message-ID: <20120322133545.23390.4182.stgit@warthog.procyon.org.uk>
Date:	Thu, 22 Mar 2012 13:35:45 +0000
From:	David Howells <dhowells@...hat.com>
To:	torvalds@...ux-foundation.com
Cc:	linux-nfs@...r.kernel.org, linux-cifs@...r.kernel.org,
	linux-api@...r.kernel.org, linux-kernel@...r.kernel.org,
	libc-alpha@...rceware.org, David Howells <dhowells@...hat.com>,
	Jeff Layton <jlayton@...hat.com>,
	Steven Whitehouse <swhiteho@...hat.com>,
	Steve Dickson <steved@...hat.com>
Subject: [PATCH 2/2] Define ENONAMESERVICE and ENAMEUNKNOWN to indicate name
 service errors

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@...hat.com>
Acked-by: Jeff Layton <jlayton@...hat.com>
Acked-by: Steven Whitehouse <swhiteho@...hat.com>
Acked-by: Steve Dickson <steved@...hat.com>
---

 arch/alpha/include/asm/errno.h  |    2 ++
 arch/mips/include/asm/errno.h   |    2 ++
 arch/parisc/include/asm/errno.h |    2 ++
 arch/sparc/include/asm/errno.h  |    2 ++
 include/asm-generic/errno.h     |    2 ++
 5 files changed, 10 insertions(+), 0 deletions(-)

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

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