On Tue, Dec 13, 2016 at 11:40:10AM +0100, Jiri Benc wrote:
> On Tue, 13 Dec 2016 01:12:38 +0100 (CET), Michał Mirosław wrote:
> > @@ -850,20 +848,11 @@ static int validate_vlan_from_nlattrs(const struct
> > sw_flow_match *match,
> > return -EINVAL;
> > }
> >
> > - if (a[OVS_KEY_ATTR_VLAN])
> > - tci = nla_get_be16(a[OVS_KEY_ATTR_VLAN]);
> > -
> > - if (!(tci & htons(VLAN_TAG_PRESENT))) {
> > - if (tci) {
> > - OVS_NLERR(log, "%s TCI does not have VLAN_TAG_PRESENT
> > bit set.",
> > - (inner) ? "C-VLAN" : "VLAN");
> > - return -EINVAL;
> > - } else if (nla_len(a[OVS_KEY_ATTR_ENCAP])) {
> > - /* Corner case for truncated VLAN header. */
> > - OVS_NLERR(log, "Truncated %s header has non-zero encap
> > attribute.",
> > - (inner) ? "C-VLAN" : "VLAN");
> > - return -EINVAL;
> > - }
> > + if (!a[OVS_KEY_ATTR_VLAN] && nla_len(a[OVS_KEY_ATTR_ENCAP])) {
> > + /* Corner case for truncated VLAN header. */
> > + OVS_NLERR(log, "Truncated %s header has non-zero encap
> > attribute.",
> > + (inner) ? "C-VLAN" : "VLAN");
> > + return -EINVAL;
>
> This looks wrong. The zero value of nla_get_be16(a[OVS_KEY_ATTR_VLAN])
> together with empty a[OVS_KEY_ATTR_ENCAP] means truncated VLAN header
> and this needs to be preserved.
>
> In other words, you need to check also !nla_get_be16(a[OVS_KEY_ATTR_VLAN])
> here.
>
>
> Overall, this whole patch looks very suspicious from the very
> beginning. The xors used are strong indication that something is not
> right.
>
> And indeed, you're breaking uAPI compatibility. Previously, the
> VLAG_TAG_PRESENT bit set in OVS_KEY_ATTR_VLAN caused the flow to match
> on packets with VLAN tag present. After this patch, it causes the flow
> to match only on those packets that have a certain value of
> VLAN_CFI_MASK in their VLAN tag (I haven't bother deciphering what
> value is checked after all these xors, it's as well possible that it
> will also match on packets _without_ any VLAN header).
>
> You have to preserve the old meaning of VLAN_TAG_PRESENT in
> OVS_KEY_ATTR_VLAN. When doing flow lookups, VLAN_TAG_PRESENT must match
> on and only on packets that have VLAN tag present, irrespective of their
> VLAN_CFI_MASK.
>
> If you want to introduce support for lookups on VLAN_CFI_MASK, you'll
> have to do that by introducing a new netlink attribute.
Hmm. In that case I'll just mask the CFI bit on entry to OVS.
Otherwise it's for me like to stab in a dark at a large beast
I know nothing about.
Best Regards,
Michał Mirosław
