netdev - Re: [RFC PATCH v1 2/3] net: add VEPA, VEB bridge mode

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Date:	Tue, 5 Jun 2012 08:41:40 +0530
From:	Krishna Kumar2 <krkumar2@...ibm.com>
To:	John Fastabend <john.r.fastabend@...el.com>
Cc:	bhutchings@...arflare.com, buytenh@...tstofly.org,
	eilong@...adcom.com, eric.w.multanen@...el.com,
	gregory.v.rose@...el.com, hadi@...erus.ca,
	jeffrey.t.kirsher@...el.com, mst@...hat.com,
	netdev@...r.kernel.org, shemminger@...tta.com, sri@...ibm.com
Subject: Re: [RFC PATCH v1 2/3] net: add VEPA, VEB bridge mode

John Fastabend <john.r.fastabend@...el.com> wrote on 06/04/2012 10:08:04
PM:

> > I think you should do something like:
> >
> >         if ((flags == BRIDGE_FLAGS_MASTER) && ...)
> >                 ...
> >
> > Also you could use BRIDGE_FLAGS_MASTER=1, SELF=2, and use
> > "if (flags & BRIDGE_FLAGS_MASTER)" for consistency?
>
> OK this is likely a good thing otherwise user space is a
> bit tedious when managing FDB and bridge modes. We do still
> need the !flags case to support existing applications though,
> (we must maintain existing semantics)
>
> if (!flags || (flags & BRIDGE_FLAGS_MASTER) && ...)
>    ...
> else (flags & BRIDGE_FLAGS_SELF)
>    ...

Yes, looks good.

> > It is possible to return a reporting error even though
> > the operation succeeded. Maybe something that could be
> > done here to indicate that the operation succeeded, or
> > is that a TODO?
> >
>
> The problem is if rtnl_bridge_notify fails due to memory
> constraints or otherwise. In this case the set has already
> completed successfully as you note so we should not return
> any error. This should fix it if I understand your concern
> correctly.
>
>    if (!err)
>       rtnl_bridge_notify(dev, flags);
>    return err;

Yes. I guess user will not hang waiting for a response as it
will pass NLM_F_ACK, which allows netlink_rcv_skb to call
netlink_ack.

Thanks,
- KK

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