[ovs-dev] [ext-244 3/4] Remove assumption that there are 64 or fewer fields.

[Ben Pfaff]

On Sat, Jul 26, 2014 at 11:11:26AM -0700, Jarno Rajahalme wrote:
> 
> On Jul 26, 2014, at 10:58 AM, Ben Pfaff <blp at nicira.com> wrote:
> 
> > On Sat, Jul 26, 2014 at 10:41:34AM -0700, Jarno Rajahalme wrote:
> >>> On Jul 26, 2014, at 10:37 AM, Ben Pfaff <blp at nicira.com> wrote:
> >>> On Sat, Jul 26, 2014 at 08:47:56AM -0700, Jarno Rajahalme wrote:
> >>>>> -    enum ofputil_protocol usable_protocols_bitwise;
> >>>>> +    uint32_t usable_protocols_bitwise;
> >>>> 
> >>>> These seem unrelated changes?
> >>> 
> >>> This is actually a sticky point.  Before this commit, meta-flow.h
> >>> includes ofp-util.h, to get "enum ofputil_protocol" for these two
> >>> members.  After this commit, ofp-util.h includes meta-flow.h, to get
> >>> struct mf_bitmap.  The circular dependency causes a problem.  The best
> >>> solution I came up with was to change the "enum ofputil_protocol"
> >>> members to uint32_t.  It's not a great solution.  Do you have a good
> >>> idea?
> >> 
> >> Can the enum be forward declared here instead?
> > 
> > Standard C doesn't have incomplete enums.  GNU C has them as an
> > extension, but they are not useful.  From the GCC manual:

[...]

> Moving the definition of the enum to a third header file could be an
> option, but I think your compromise is a good one as well, especially
> if you add a comment near the supported protocols members explaining
> the relation to the enum.

Thanks.  That is a good idea.  I updated this code to:

    /* Usable protocols.
     *
     * NXM and OXM are extensible, allowing later extensions to be sent in
     * earlier protocol versions, so this does not necessarily correspond to
     * the OpenFlow protocol version the field was introduced in.
     * Also, some field types are tranparently mapped to each other via the
     * struct flow (like vlan and dscp/tos fields), so each variant supports
     * all protocols.
     *
     * These are combinations of OFPUTIL_P_*.  (They are not declared as type
     * enum ofputil_protocol because that would give meta-flow.h and ofp-util.h
     * a circular dependency.) */
    uint32_t usable_protocols;         /* If fully/CIDR masked. */
    uint32_t usable_protocols_bitwise; /* If partially/non-CIDR masked. */