Re: [Patch 3/3] net: reserve ports for applications using fixed portnumbers

[Cong Wang]

Tetsuo Handa wrote:
> Hello.
>
> Amerigo Wang wrote:
> > Index: linux-2.6/drivers/infiniband/core/cma.c
> > ===================================================================
> > --- linux-2.6.orig/drivers/infiniband/core/cma.c
> > +++ linux-2.6/drivers/infiniband/core/cma.c
> > @@ -1980,6 +1980,8 @@ retry:
> >  	/* FIXME: add proper port randomization per like inet_csk_get_port */
> >  	do {
> >  		ret = idr_get_new_above(ps, bind_list, next_port, &port);
> > +		if (inet_is_reserved_local_port(port))
> > +			ret = -EAGAIN;
>
> You should not overwrite ret with -EAGAIN when idr_get_new_above() returned
> -ENOSPC. I don't know about idr, thus I don't know whether
>
> 		if (!ret && inet_is_reserved_local_port(port))
> 			ret = -EAGAIN;
>
> is correct or not.

Hmm, good catch! I think it is correct.



> >  	} while ((ret == -EAGAIN) && idr_pre_get(ps, GFP_KERNEL));
> >  
> >  	if (ret)
> > @@ -2996,10 +2998,13 @@ static int __init cma_init(void)
> >  {
> >  	int ret, low, high, remaining;
> >  
> > -	get_random_bytes(&next_port, sizeof next_port);
> >  	inet_get_local_port_range(&low, &high);
> > +again:
> > +	get_random_bytes(&next_port, sizeof next_port);
> >  	remaining = (high - low) + 1;
> >  	next_port = ((unsigned int) next_port % remaining) + low;
> > +	if (inet_is_reserved_local_port(next_port))
> > +		goto again;
> >  
>
> You should not unconditionally "goto again;".
> If all ports were reserved, it will loop forever (CPU stalls).

Yeah, how about:

	int tries = 10;
	...
again:
	...
	if (inet_is_reserved_local_port(next_port)) {
		if (tries--)
			goto again;
		else
			return -EBUSY;
	}

?


> >  	cma_wq = create_singlethread_workqueue("rdma_cm");
> >  	if (!cma_wq)
>
>
> > Index: linux-2.6/net/sctp/socket.c
> > ===================================================================
> > --- linux-2.6.orig/net/sctp/socket.c
> > +++ linux-2.6/net/sctp/socket.c
> > @@ -5436,6 +5436,8 @@ static long sctp_get_port_local(struct s
> >  			rover++;
> >  			if ((rover < low) || (rover > high))
> >  				rover = low;
> > +			if (inet_is_reserved_local_port(rover))
> > +				continue;
>
> This one needs to be
>
> 			if (inet_is_reserved_local_port(rover))
> 				goto next_nolock;
>
> >  			index = sctp_phashfn(rover);
> >  			head = &sctp_port_hashtable[index];
> >  			sctp_spin_lock(&head->lock);
>
>  next:
> 			sctp_spin_unlock(&head->lock);
> +next_nolock:
> 		} while (--remaining > 0);
>
> otherwise, it will loop forever if all ports were reserved.

Sorry, doesn't 'continue' jump to exactly where 'next_nolock' is??
Or I am missing something?


Thanks for your review!

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