Re: [PATCH 30/32] NFS: Add a dns resolver for use with NFSv4 referrals and migration

J. Bruce Fields
2009-08-21T20:47:04Z

On Wed, Aug 19, 2009 at 07:51:56PM -0400, Trond Myklebust wrote:
> On Wed, 2009-08-19 at 19:38 -0400, Trond Myklebust wrote:
> > The NFSv4 and NFSv4.1 protocols both allow for the redirection of a client
> > from one server to another in order to support filesystem migration and
> > replication. For full protocol support, we need to add the ability to
> > convert a DNS host name into an IP address that we can feed to the RPC
> > client.
> >
> > We'll reuse the sunrpc cache, now that it has been converted to work with
> > rpc_pipefs.
>
> Should I merge this too?

It's cute. If it's expected that more people may want to write
nfs_cache_getent scripts, maybe it would be useful to them. But then,
it's not that hard for them just to call the script by hand.

I guess I probably wouldn't....

--b.

>
> From: Trond Myklebust <Trond.Myklebust@netapp.com>
> Subject: NFS: Testcase for the DNS resolver
>
> Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
> ---
>
> fs/nfs/Kconfig | 11 ++++++++++
> fs/nfs/Makefile | 4 +++
> fs/nfs/cache_testcases.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++
> fs/nfs/dns_resolve.c | 1 +
> 4 files changed, 69 insertions(+), 0 deletions(-)
> create mode 100644 fs/nfs/cache_testcases.c
>
>
> diff --git a/fs/nfs/Kconfig b/fs/nfs/Kconfig
> index 2a77bc2..13fc471 100644
> --- a/fs/nfs/Kconfig
> +++ b/fs/nfs/Kconfig
> @@ -101,3 +101,14 @@ 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_CACHETEST
> + tristate "Test the NFS client DNS cache upcalls"
> + depends on NFS_FS
> + default N
> + help
> + Choose M if you want to build a module that can be used to test
> + the NFS client DNS cache upcall mechanism.
> +
> + Most people will want to say N
> +
> diff --git a/fs/nfs/Makefile b/fs/nfs/Makefile
> index da7fda6..4fe5ac2 100644
> --- a/fs/nfs/Makefile
> +++ b/fs/nfs/Makefile
> @@ -17,3 +17,7 @@ nfs-$(CONFIG_NFS_V4) += nfs4proc.o nfs4xdr.o nfs4state.o nfs4renewd.o \
> nfs4namespace.o
> nfs-$(CONFIG_SYSCTL) += sysctl.o
> nfs-$(CONFIG_NFS_FSCACHE) += fscache.o fscache-index.o
> +
> +obj-$(CONFIG_NFS_CACHETEST) += nfs_cachetest.o
> +nfs_cachetest-objs := cache_testcases.o
> +
> diff --git a/fs/nfs/cache_testcases.c b/fs/nfs/cache_testcases.c
> new file mode 100644
> index 0000000..2d8810a
> --- /dev/null
> +++ b/fs/nfs/cache_testcases.c
> @@ -0,0 +1,53 @@
> +/*
> + * linux/fs/nfs/cache_testcases.c
> + *
> + * Testcases for the NFS client cache upcalls
> + *
> + * Copyright (c) 2009 Trond Myklebust <Trond.Myklebust@netapp.com>
> + */
> +
> +#include <linux/module.h>
> +#include <linux/moduleparam.h>
> +#include <linux/sunrpc/clnt.h>
> +
> +#include "dns_resolve.h"
> +
> +static char hostname[NFS_DNS_HOSTNAME_MAXLEN] = "";
> +module_param_string(hostname, hostname, sizeof(hostname), 0600);
> +MODULE_PARM_DESC(hostname, "DNS hostname to look up");
> +
> +static int nfs_lookup_hostname(char *name)
> +{
> + struct sockaddr_storage sa;
> + ssize_t salen;
> +
> + if (!name || *name == '\0')
> + goto out;
> + salen = nfs_dns_resolve_name(name, strlen(name),
> + (struct sockaddr *)&sa, sizeof(sa));
> + if (salen > 0) {
> + char buf[INET6_ADDRSTRLEN+IPV6_SCOPE_ID_LEN+1];
> +
> + rpc_ntop((struct sockaddr *)&sa, buf, sizeof(buf));
> + printk(KERN_NOTICE "%15s ", buf);
> + } else
> + printk(KERN_NOTICE "%15zd ", salen);
> + printk("%15s\n", name);
> +out:
> + return 0;
> +}
> +
> +static int nfs_dnstest_init(void)
> +{
> + return nfs_lookup_hostname(hostname);
> +}
> +
> +static void nfs_dnstest_exit(void)
> +{
> +}
> +
> +MODULE_AUTHOR("Trond Myklebust <Trond.Myklebust@netapp.com>");
> +MODULE_LICENSE("GPL");
> +
> +module_init(nfs_dnstest_init)
> +module_exit(nfs_dnstest_exit)
> diff --git a/fs/nfs/dns_resolve.c b/fs/nfs/dns_resolve.c
> index f4d54ba..572d453 100644
> --- a/fs/nfs/dns_resolve.c
> +++ b/fs/nfs/dns_resolve.c
> @@ -322,6 +322,7 @@ ssize_t nfs_dns_resolve_name(char *name, size_t namelen,
> ret = -ESRCH;
> return ret;
> }
> +EXPORT_SYMBOL_GPL(nfs_dns_resolve_name);
>
> int nfs_dns_resolver_init(void)
> {
>
> --
> Trond Myklebust
> Linux NFS client maintainer
>
> NetApp
> Trond.Myklebust@netapp.com
> www.netapp.com
> --
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