Re: [PATCH 2/2] sm-notify: Send fully-qualified and unqualified mon_names

[Jeff Layton <jlayton@redhat.com>]

On Mon, 15 Mar 2010 13:51:45 -0400
Chuck Lever <chuck.lever@oracle.com> wrote:

> During any file locking interaction between an NFS client and server,
> the client tells the server what hostname it will use as the mon_name
> argument of the SM_NOTIFY request sent by the client when it reboots.
> This is the "caller_name" argument of an NLMPROC_LOCK request.
> 
> The server, however, never tells the client what mon_name argument
> it will use when sending an SM_NOTIFY request.  In order to recognize
> the server, clients usually guess what mon_name the server might
> send, by using the server hostname provided by the user on the mount
> command line.
> 
> Frequently, the user provides an unqualified server name on the mount
> command.  The server might then call the client back with a fully
> qualified domain name, which might not match in some cases.
> 
> Solaris, and perhaps other implementations, attempt to mitigate this
> problem by sending two SM_NOTIFY requests to each peer: one with an
> unqualified mon_name argument, and one with a fully qualified mon_name.
> 
> Implement such a scheme for sm-notify.
> 
> Since my_name is almost always the fully-qualified hostname associated
> with the local system, just wiping the left-most '.' in the my_name
> argument and sending another SM_NOTIFY is nearly always sufficient.
> 
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

Looks reasonable, and we tested a similar or identical patch prior to
Connectathon and during it.

Reviewed-by: Jeff Layton <jlayton@redhat.com>

> ---
> 
>  utils/statd/sm-notify.c |   21 +++++++++++++++++----
>  1 files changed, 17 insertions(+), 4 deletions(-)
> 
> diff --git a/utils/statd/sm-notify.c b/utils/statd/sm-notify.c
> index 2d14668..437e37a 100644
> --- a/utils/statd/sm-notify.c
> +++ b/utils/statd/sm-notify.c
> @@ -634,15 +634,28 @@ recv_rpcbind_reply(struct sockaddr *sap, struct nsm_host *host, XDR *xdr)
>  }
>  
>  /*
> - * Successful NOTIFY call. Server returns void, so nothing
> - * we need to do here.
> + * Successful NOTIFY call. Server returns void.
> + *
> + * Try sending another SM_NOTIFY with an unqualified "my_name"
> + * argument.  Reuse the port number.  If "my_name" is already
> + * unqualified, we're done.
>   */
>  static void
>  recv_notify_reply(struct nsm_host *host)
>  {
> -	xlog(D_GENERAL, "Host %s notified successfully", host->name);
> +	char *dot = strchr(host->my_name, '.');
>  
> -	smn_forget_host(host);
> +	if (dot != NULL) {
> +		*dot = '\0';
> +		host->send_next = time(NULL);
> +		host->xid = 0;
> +		if (host->timeout >= NSM_MAX_TIMEOUT / 4)
> +			host->timeout = NSM_MAX_TIMEOUT / 4;
> +		insert_host(host);
> +	} else {
> +		xlog(D_GENERAL, "Host %s notified successfully", host->name);
> +		smn_forget_host(host);
> +	}
>  }
>  
>  /*
>