On Thu, Mar 07, 2013 at 09:00:49PM -0600, Saul St. John wrote: > I was trying to bit-twiddle ARP packets with NXAST_REG_MOVE actions, > when I found that NXM_OF_ARP_OP fields aren't writable. nicira-ext.h > doesn't explicitly call out unacceptable destinations, although > NXM_OF_ARP_OP isn't included on the list of acceptable dst. I am curious: > > 1) Is there a reason for not allowing this field as the target of > mangling actions?
I don't know a good one. I guess that no one has implemented it, and that is probably because there has been little demand for it. (I don't remember previous requests.) > 2) The load/set_field syntax in the ovs-ofctl manpage doesn't describe > unacceptable targets at all, although it also has them. (See below.) > Shouldn't it? It doesn't mention the acceptable ones either. I agree that there is considerable room for improvement. > 3) I don't have a OF1.2-speaking controller at-hand to test this, but it > looks like the OFPAT_SET_FIELD action calls the same implementation as > the NXM actions. Does OVS enforce the same restrictions on this action? Yes. > If so, is that correct behavior? (I can't tell from the spec if a switch > implementation supporting set_field needs to support setting all fields > it supports matching (except those excluded in A.2.5).) I doubt that a switch implementation is required to support set_field for all the fields it supports. It does not make much sense to change some fields; for example, changing the Ethertype is ordinarily going to, at most, cause confusion. _______________________________________________ discuss mailing list discuss@openvswitch.org http://openvswitch.org/mailman/listinfo/discuss
