Subject: Re: [PATCH] NFS use kernel DNS resolver
From: Trond Myklebust <Trond.Myklebust@netapp.com>
To: Bryan Schumaker <bjschuma@netapp.com>, David Howells <dhowells@redhat.com>
Cc: linux-nfs@vger.kernel.org
In-Reply-To: <4C59D1A3.5030406@netapp.com>
References: <4C59D1A3.5030406@netapp.com>
Content-Type: text/plain; charset="UTF-8"
Date: Wed, 04 Aug 2010 21:09:56 -0400
Message-ID: <1280970596.2865.28.camel@heimdal.trondhjem.org>
Sender: linux-nfs-owner@vger.kernel.org
MIME-Version: 1.0

On Wed, 2010-08-04 at 16:46 -0400, Bryan Schumaker wrote:
> Use the kernel DNS resolver to translate hostnames to IP addresses.
> Create a new config option to choose between the legacy DNS resolver and the
> new resolver.
> 
> Signed-off-by: Bryan Schumaker <bjschuma@netapp.com>
---


This looks good to me, and it makes sense to share as much code with
CIFS and AFS as we can, now that the objections I had to the original
implementation have been resolved.

David, can you carry this as part of your 'generic DNS resolver'
patchset?

Cheers
  Trond

> diff --git a/fs/nfs/Kconfig b/fs/nfs/Kconfig
> index a43d07e..b1209ac 100644
> --- a/fs/nfs/Kconfig
> +++ b/fs/nfs/Kconfig
> @@ -100,3 +100,19 @@ config NFS_FSCACHE
>  	help
>  	  Say Y here if you want NFS data to be cached locally on disc through
>  	  the general filesystem cache manager
> +
> +config NFS_USE_LEGACY_DNS
> +	bool "Use the legacy NFS DNS resolver"
> +	depends on NFS_FS
> +	help
> +	  The kernel now provides a method for translating a host name into an
> +	  IP address.  Select Y here if you would rather use your own DNS
> +	  resolver script.
> +
> +	  If unsure, say N
> +
> +config NFS_USE_KERNEL_DNS
> +	bool
> +	depends on NFS_FS && !NFS_USE_LEGACY_DNS
> +	select DNS_RESOLVER
> +	default y
> diff --git a/fs/nfs/Makefile b/fs/nfs/Makefile
> index da7fda6..ec8989c 100644
> --- a/fs/nfs/Makefile
> +++ b/fs/nfs/Makefile
> @@ -7,7 +7,7 @@ obj-$(CONFIG_NFS_FS) += nfs.o
>  nfs-y 			:= client.o dir.o file.o getroot.o inode.o super.o nfs2xdr.o \
>  			   direct.o pagelist.o proc.o read.o symlink.o unlink.o \
>  			   write.o namespace.o mount_clnt.o \
> -			   dns_resolve.o cache_lib.o
> +			   dns_resolve.o
>  nfs-$(CONFIG_ROOT_NFS)	+= nfsroot.o
>  nfs-$(CONFIG_NFS_V3)	+= nfs3proc.o nfs3xdr.o
>  nfs-$(CONFIG_NFS_V3_ACL)	+= nfs3acl.o
> @@ -15,5 +15,6 @@ nfs-$(CONFIG_NFS_V4)	+= nfs4proc.o nfs4xdr.o nfs4state.o nfs4renewd.o \
>  			   delegation.o idmap.o \
>  			   callback.o callback_xdr.o callback_proc.o \
>  			   nfs4namespace.o
> +nfs-$(CONFIG_NFS_LEGACY_DNS) += cache_lib.o
>  nfs-$(CONFIG_SYSCTL) += sysctl.o
>  nfs-$(CONFIG_NFS_FSCACHE) += fscache.o fscache-index.o
> diff --git a/fs/nfs/dns_resolve.c b/fs/nfs/dns_resolve.c
> index 76fd235..a67e2a4 100644
> --- a/fs/nfs/dns_resolve.c
> +++ b/fs/nfs/dns_resolve.c
> @@ -6,6 +6,28 @@
>   * Resolves DNS hostnames into valid ip addresses
>   */
> 
> +#ifdef CONFIG_NFS_USE_KERNEL_DNS
> +
> +#include <linux/sunrpc/clnt.h>
> +#include <linux/dns_resolver.h>
> +
> +ssize_t nfs_dns_resolve_name(char *name, size_t namelen,
> +		struct sockaddr *sa, size_t salen)
> +{
> +	ssize_t ret;
> +	char *ip_addr = NULL;
> +	int ip_len;
> +
> +	ip_len = dns_query(NULL, name, namelen, NULL, &ip_addr, NULL);
> +	if (ip_len > 0)
> +		ret = rpc_pton(ip_addr, ip_len, sa, salen);
> +	else
> +		ret = -ESRCH;
> +	kfree(ip_addr);
> +	return ret;
> +}
> +#else
> +
>  #include <linux/hash.h>
>  #include <linux/string.h>
>  #include <linux/kmod.h>
> @@ -346,3 +368,4 @@ void nfs_dns_resolver_destroy(void)
>  	nfs_cache_unregister(&nfs_dns_resolve);
>  }
> 
> +#endif
> diff --git a/fs/nfs/dns_resolve.h b/fs/nfs/dns_resolve.h
> index a3f0938..fe5c3b3 100644
> --- a/fs/nfs/dns_resolve.h
> +++ b/fs/nfs/dns_resolve.h
> @@ -6,8 +6,21 @@
> 
>  #define NFS_DNS_HOSTNAME_MAXLEN	(128)
> 
> +
> +#ifdef CONFIG_NFS_USE_KERNEL_DNS
> +static inline int nfs_dns_resolver_init(void)
> +{
> +	return 0;
> +}
> +
> +static inline void nfs_dns_resolver_destroy(void)
> +{
> +}
> +#else
>  extern int nfs_dns_resolver_init(void);
>  extern void nfs_dns_resolver_destroy(void);
> +#endif
> +
>  extern ssize_t nfs_dns_resolve_name(char *name, size_t namelen,
>  		struct sockaddr *sa, size_t salen);
> --
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