Re: [RFC PATCH] NFS: allow deprecation of NFS UDP protocol

[Steve Dickson <SteveD@RedHat.com>]

On 11/8/19 4:32 PM, Olga Kornievskaia wrote:
> From: Olga Kornievskaia <kolga@netapp.com>
> 
> Add a kernel config CONFIG_NFS_DISABLE_UDP_SUPPORT to disallow NFS
> UDP mounts.
> 
> I took the same approach as Chuck's deprecation of DES enc types
> to start with default to still allow but I think the ultimate
> goal is to disable
> 
> Question: how do we have folks trying this unless we set it to false?
Exactly... Why not do the opposite? Off by default... instead of
having to set the variable to turn UDP off?

steved.
 
> 
> Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
> ---
>  fs/nfs/Kconfig  | 10 ++++++++++
>  fs/nfs/client.c |  4 ++++
>  fs/nfs/super.c  |  8 ++++++++
>  3 files changed, 22 insertions(+)
> 
> diff --git a/fs/nfs/Kconfig b/fs/nfs/Kconfig
> index 295a7a2..6320113 100644
> --- a/fs/nfs/Kconfig
> +++ b/fs/nfs/Kconfig
> @@ -196,3 +196,13 @@ config NFS_DEBUG
>  	depends on NFS_FS && SUNRPC_DEBUG
>  	select CRC32
>  	default y
> +
> +config NFS_DISABLE_UDP_SUPPORT
> +	bool "NFS: Disable NFS UDP protocol support"
> +	depends on NFS_FS
> +	default n
> +	help
> +	  Choose Y here to disable the use of NFS over UDP. NFS over UDP
> +	  on modern networks (1Gb+) can lead to data corruption caused by
> +	  fragmentation during high loads.
> +	  The default is N because many deployments still use UDP.
> diff --git a/fs/nfs/client.c b/fs/nfs/client.c
> index 02110a3..24ca314 100644
> --- a/fs/nfs/client.c
> +++ b/fs/nfs/client.c
> @@ -474,6 +474,7 @@ void nfs_init_timeout_values(struct rpc_timeout *to, int proto,
>  			to->to_maxval = to->to_initval;
>  		to->to_exponential = 0;
>  		break;
> +#ifdef CONFIG_NFS_DISABLE_UDP_SUPPORT
>  	case XPRT_TRANSPORT_UDP:
>  		if (retrans == NFS_UNSPEC_RETRANS)
>  			to->to_retries = NFS_DEF_UDP_RETRANS;
> @@ -484,6 +485,7 @@ void nfs_init_timeout_values(struct rpc_timeout *to, int proto,
>  		to->to_maxval = NFS_MAX_UDP_TIMEOUT;
>  		to->to_exponential = 1;
>  		break;
> +#endif
>  	default:
>  		BUG();
>  	}
> @@ -580,8 +582,10 @@ static int nfs_start_lockd(struct nfs_server *server)
>  		default:
>  			nlm_init.protocol = IPPROTO_TCP;
>  			break;
> +#ifdef CONFIG_NFS_DISABLE_UDP_SUPPORT
>  		case XPRT_TRANSPORT_UDP:
>  			nlm_init.protocol = IPPROTO_UDP;
> +#endif
>  	}
>  
>  	host = nlmclnt_init(&nlm_init);
> diff --git a/fs/nfs/super.c b/fs/nfs/super.c
> index a84df7d6..21e59da 100644
> --- a/fs/nfs/super.c
> +++ b/fs/nfs/super.c
> @@ -1011,7 +1011,9 @@ static void nfs_set_port(struct sockaddr *sap, int *port,
>  static void nfs_validate_transport_protocol(struct nfs_parsed_mount_data *mnt)
>  {
>  	switch (mnt->nfs_server.protocol) {
> +#ifdef CONFIG_NFS_DISABLE_UDP_SUPPORT
>  	case XPRT_TRANSPORT_UDP:
> +#endif
>  	case XPRT_TRANSPORT_TCP:
>  	case XPRT_TRANSPORT_RDMA:
>  		break;
> @@ -1033,8 +1035,10 @@ static void nfs_set_mount_transport_protocol(struct nfs_parsed_mount_data *mnt)
>  			return;
>  	switch (mnt->nfs_server.protocol) {
>  	case XPRT_TRANSPORT_UDP:
> +#ifdef CONFIG_NFS_DISABLE_UDP_SUPPORT
>  		mnt->mount_server.protocol = XPRT_TRANSPORT_UDP;
>  		break;
> +#endif
>  	case XPRT_TRANSPORT_TCP:
>  	case XPRT_TRANSPORT_RDMA:
>  		mnt->mount_server.protocol = XPRT_TRANSPORT_TCP;
> @@ -2204,6 +2208,10 @@ static int nfs_validate_text_mount_data(void *options,
>  #endif /* CONFIG_NFS_V4 */
>  	} else {
>  		nfs_set_mount_transport_protocol(args);
> +#ifdef CONFIG_NFS_DISABLE_UDP_SUPPORT
> +		if (args->nfs_server.protocol == XPRT_TRANSPORT_UDP)
> +			goto out_invalid_transport_udp;
> +#endif
>  		if (args->nfs_server.protocol == XPRT_TRANSPORT_RDMA)
>  			port = NFS_RDMA_PORT;
>  	}
>