netdev - Re: [PATCH net-next 0/5] SCTP updates

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Date:	Thu, 10 Jul 2014 06:57:28 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	Daniel Borkmann <dborkman@...hat.com>
Cc:	David Laight <David.Laight@...LAB.COM>,
	Vlad Yasevich <vyasevich@...il.com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"geirola@...il.com" <geirola@...il.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-sctp@...r.kernel.org" <linux-sctp@...r.kernel.org>
Subject: Re: [PATCH net-next 0/5] SCTP updates

On Thu, Jul 10, 2014 at 11:37:19AM +0200, Daniel Borkmann wrote:
> On 07/10/2014 11:02 AM, David Laight wrote:
> >From: Neil Horman
> >...
> >>>No there is not direct overlap between the two.  However, as Michael pointed out,
> >>>there is a new option to control SCTP_RCVINFO.  So would could add a deprecation
> >>>warning to the over SCTP_EVENTS option and carry SCTP_SNDRCVINFO with it.
> >>>Once SCTP_EVENTS goes away so can SCTP_SNDRCVINFO.
> >>>
> >>Ok, so we should still consider deprecation warnings then.  Daniel, what about
> >>ratelimited warnings with pids included then?
> >
> >Can you defer any deprecation warnings for a few kernel versions?
> >This gives time for applications to be recoded.
> 
> I am fine either way, adding the warning a bit later seems fine, too.
> 
> Right now, even in-kernel users like dlm would hit it if we include
> it immediately.
> 
> Otherwise, I'll just add something like the below ...
> 
This works for me, I don't see any reason to wait, and its a pretty easy
changeover for most applications to make.

Thanks David.
Neil

> diff --git a/net/sctp/socket.c b/net/sctp/socket.c
> index d95a50c..6a0e5a4 100644
> --- a/net/sctp/socket.c
> +++ b/net/sctp/socket.c
> @@ -2205,8 +2205,13 @@ static int sctp_setsockopt_events(struct sock *sk, char __user *optval,
>  	if (copy_from_user(&sctp_sk(sk)->subscribe, optval, optlen))
>  		return -EFAULT;
> 
> -	/*
> -	 * At the time when a user app subscribes to SCTP_SENDER_DRY_EVENT,
> +	if (sctp_sk(sk)->subscribe.sctp_data_io_event)
> +		pr_warn_ratelimited(DEPRECATED "%s (pid %d) "
> +				    "Requested SCTP_SNDRCVINFO event.\n"
> +				    "Use SCTP_RCVINFO through SCTP_RECVRCVINFO option instead.\n",
> +				    current->comm, task_pid_nr(current));
> +
> +	/* At the time when a user app subscribes to SCTP_SENDER_DRY_EVENT,
>  	 * if there is no data to be sent or retransmit, the stack will
>  	 * immediately send up this notification.
>  	 */
> 
> >Including argv[0] (even just the exec-time value) is much more use than the pid.
> >
> >Actually this is 'right PITA' for an application.
> >A program binary that needs to work with old and new kernels will have to
> >try the new option, and if it fails fall back to the old one, and then
> >conditionally create/inspect the cmsg data.
> >I can't actually imagine anyone bothering!
> >
> >Our sctp code is actually in a kernel module, so we can look at the kernel
> >version when (part of) the driver is compiled on the target system.
> >
> >	David
> >
> >
> >
> 
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