On Tue, Nov 12, 2013 at 09:58:09PM -0800, Ben Pfaff wrote:
> On Tue, Nov 12, 2013 at 05:52:37PM -0800, Jarno Rajahalme wrote:
> >
> >
> > > On Nov 12, 2013, at 8:47 AM, Ben Pfaff <b...@nicira.com> wrote:
> > >
> > >> On Tue, Nov 12, 2013 at 04:45:51PM +0900, Simon Horman wrote:
> > ...
> > >> +enum ofp_table_config {
> > >> + OFPTC_TABLE_MISS_CONTROLLER = 0, /* Send to controller. */
> > >> + OFPTC_TABLE_MISS_CONTINUE = 1 << 0, /* Continue to the next table
> > >> in the
> > >> + pipeline (OpenFlow 1.0
> > >> behavior). */
> > >> + OFPTC_TABLE_MISS_DROP = 1 << 1, /* Drop the packet. */
> > >> + OFPTC_TABLE_MISS_MASK = 3
> > >> +};
> > >
> > > I know that at least some version of the standard writes it that way but
> > > the constants don't make any sense in that form. 0 << 0, 1 << 0, 2 <<
> > > 0, 3 << 0 are a lot more sensible.
> >
> > Why shift zero bits?
>
> Only to imply more strongly, at a glance, that these are bitwise fields
> within a larger word. I'm not sure any other bitwise fields were ever
> defined in that word, but that was the intent, at least.
OF1.4 defines more bits. Perhaps I should send a follow-up patch
to merge in the following. It didn't occur to me earlier as my patch-set
does not use the new bits.
OFPTC_EVICTION = 1 << 2, /* Authorise table to evict flows. */
OFPTC_VACANCY_EVENTS = 1 << 3, /* Enable vacancy events. */
Also, as of OF1.3 the meaning of 3 has changed, though
I don't think it is particularly important from the
point of view of the Open vSwitch implementation.
OFPTC_DEPRECATED_MASK = 3, /* Deprecated bits */
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