Aaron Conole <[email protected]> writes: > Dumitru Ceara <[email protected]> writes: > >> On 4/26/21 2:19 PM, Eelco Chaudron wrote: >>> Currently, conntrack in the kernel has an undocumented feature referred >>> to as all-zero IP address NULL SNAT. Basically, when a source port >>> collision is detected during the commit, the source port will be >>> translated to an ephemeral port. If there is no collision, no SNAT is >>> performed. >>> >>> This patchset documents this behavior and adds a self-test to verify >>> it's not changing. >>> >>> Signed-off-by: Eelco Chaudron <[email protected]> >>> --- >>> v3: Renamed NULL SNAT to all-zero IP SNAT. >>> v2: Fixed NULL SNAT to only work in the -rpl state to be inline with >>> OpenShift-SDN's behavior. >> >> Hi Eelco, >> >> Would it be possible to add this capability to the list of kernel >> Datapath.capabilities ovsdb column? [0] >> >> Given that the patch to add userspace datapath support for all-zero IP >> SNAT is not accepted yet [1], and even if it does it will likely not be >> backported to LTS because it's a feature, this would make it easier for >> OVN (for example ovn-controller) to determine at runtime if it should >> use all-zero IP SNAT or not. > > I think it would be rather difficult to add this to the userspace patch > being proposed. > > Actually, if we want something where datapath can detect whether such > feature is supported, there isn't a good test. For instance, normally > we would attempt to insert a flow that has the characteristics we desire > and look for a failure to insert. In the case of all-zero SNAT, > both datapaths can "accept" it, so it becomes difficult. >
I was wondering the same, a successful insertion doesn't ensure the correctness and so the support of this feature. > Also, the netlink datapath under linux has had this support since it was > introduced, so we're really just documenting it here. It can still be > used in older releases. OTOH, userspace doesn't have such support. > Both datapaths will accept flows with SNAT set to 0, as far as I can > tell. This means there's not an easy way to distinguish them. > > Maybe we need a change to this patchset to reject such flows from the > netdev datapath, and then we can modify [1] to remove such limitation. > Then it can be detected by the datapath capabilities that already exist. > > Maybe I missed something, or misunderstood something. > > Thoughts? > Considering that linux supports all-zero snat since day one, the assumption seems solid enough to me for it. I have no details about it, but what about Windows dp? >> [0] >> https://github.com/openvswitch/ovs/commit/27501802d09f782b8133031c1eae3394ae5ce147 >> >> [1] https://patchwork.ozlabs.org/project/openvswitch/list/?series=241223 >> >> Thanks, >> Dumitru _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
