netdev - Re: [PATCH 3/5 net-next] cnic: Randomize initial TCP port for iSCSI connections

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Date:	Fri, 10 Jun 2011 06:39:27 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Stephen Hemminger <shemminger@...tta.com>
Cc:	Michael Chan <mchan@...adcom.com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Eddie Wai <eddie.wai@...adcom.com>
Subject: Re: [PATCH 3/5 net-next] cnic: Randomize initial TCP port for
 iSCSI connections

Le jeudi 09 juin 2011 à 21:01 -0700, Stephen Hemminger a écrit :
> On Thu, 9 Jun 2011 18:08:00 -0700
> "Michael Chan" <mchan@...adcom.com> wrote:
> 
> > 
> > On Thu, 2011-06-09 at 08:27 -0700, Stephen Hemminger wrote:
> > > On Wed, 8 Jun 2011 22:29:34 -0700
> > > "Michael Chan" <mchan@...adcom.com> wrote:
> > > 
> > > >  static int cnic_cm_alloc_mem(struct cnic_dev *dev)
> > > >  {
> > > >  	struct cnic_local *cp = dev->cnic_priv;
> > > > +	u32 port_id;
> > > >  
> > > >  	cp->csk_tbl = kzalloc(sizeof(struct cnic_sock) * MAX_CM_SK_TBL_SZ,
> > > >  			      GFP_KERNEL);
> > > >  	if (!cp->csk_tbl)
> > > >  		return -ENOMEM;
> > > >  
> > > > +	get_random_bytes(&port_id, sizeof(port_id));
> > > 
> > > I think random32() or it's alias net_random() would be sufficient
> > > for your needs here.
> > > 
> > 
> > random32() is pseudo random so we can get the same number after reboot,
> > right?  One scenario is that we may be booting from an iSCSI target, but
> > due to some failure, the user may be rebooting multiple times rapidly.
> > We want to use a different port during each boot.
> 
> random32 is seeded off get_random_bytes at boot.

cnic_cm_alloc_mem() is apparently called one time per boot, it seems OK
to call get_random_bytes() in this case ?



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