On Fri, Oct 11, 2013 at 12:51:35PM -0700, Jarno Rajahalme wrote:
>
> On Oct 11, 2013, at 9:02 AM, Ben Pfaff <b...@nicira.com> wrote:
>
> > On Wed, Oct 09, 2013 at 01:47:50PM -0700, Jarno Rajahalme wrote:
> >> Use the offset of the last member in struct flow instead of the
> >> struct size to help catch changes in the declaration.
> >>
> >> Add flow_random_hash_fields() used for testing in places where
> >> struct flow was used without zero initialization before.
> >>
> >> With these changes we do not need to keep updating explicit padding
> >> in struct flow as fields are added or deleted.
> >>
> >> Signed-off-by: Jarno Rajahalme <jrajaha...@nicira.com>
> >
> > ...
> >
> >> @@ -603,7 +604,11 @@ flow_wildcards_init_catchall(struct flow_wildcards
> >> *wc)
> >> }
> >>
> >> /* Initializes 'wc' as an exact-match set of wildcards; that is, 'wc' does
> >> not
> >> - * wildcard any bits or fields. */
> >> + * wildcard any bits or fields.
> >> + * Note that also bits that are always zeroes (padding, extra bits in
> >> fields
> >> + * like IPv6 flow label), and fields that are mutually exclusive (e.g.,
> >> IPv4
> >> + * and IPv6 addresses) are included.
> >> + */
> >> void
> >> flow_wildcards_init_exact(struct flow_wildcards *wc)
> >> {
> >
> > I don't like this semantic of initializing pads to 0xff very much. But
> > I see that flow_wildcards_init_exact() has only one caller worth
> > considering, which is this code in rule_dpif_lookup_in_table():
> >
> > } else if (frag && ofproto->up.frag_handling == OFPC_FRAG_DROP) {
> > cls_rule = &ofproto->drop_frags_rule->up.cr;
> > if (wc) {
> > flow_wildcards_init_exact(wc);
> > }
> > } else {
> >
> > I don't understand why we need to use flow_wildcards_init_exact() when
> > dropping fragments. If we didn't use it, then we could probably drop
> > the function entirely. Do you have any idea why we use it here?
> > (Justin?)
>
> Maybe that's just to be on the safe side? If the policy of the
> ofproto is to drop all frags, then maybe one mega-flow for that
> effect would be enough? It seems that instead of forcing an exact
> match, looking at the in_port and nw_frag would be sufficient?
Justin confirmed off-list that he doesn't think this is necessary
here.
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