On Tue, May 21, 2024 at 9:56 PM Numan Siddique <num...@ovn.org> wrote: > > On Mon, May 20, 2024 at 1:47 AM Vasyl Saienko <vsaie...@mirantis.com> wrote: > > > > Thanks for feedback Numan. > > > > On Wed, May 15, 2024 at 12:04 AM Numan Siddique <num...@ovn.org> wrote: > > > > > On Mon, May 13, 2024 at 9:00 AM Dumitru Ceara <dce...@redhat.com> wrote: > > > > > > > > On 5/4/24 11:38, Vasyl Saienko wrote: > > > > > Hello Numan > > > > > > > > > > Thanks for review and feedback. > > > > > > > > > > On Fri, May 3, 2024 at 7:14 PM Numan Siddique <num...@ovn.org> wrote: > > > > > > > > > >> On Mon, Apr 22, 2024 at 2:54 AM Vasyl Saienko < vsaie...@mirantis.com> > > > > >> wrote: > > > > >>> > > > > >>> Reply only if target ethernet address is broadcast, if > > > > >>> address is specified explicitly do noting to let target > > > > >>> reply by itself. This technique allows to monitor target > > > > >>> aliveness with arping. > > > > >> > > > > >> Thanks for the patch. > > > > >> > > > > >> This patch does change the behavior of OVN. Having ARP responder > > > > >> flows avoids tunnelling the request packet if the destination is on a > > > > >> different compute node. > > > > >> But I don't think its a big deal. > > > > >> > > > > >> You are totally correct that the ARP responder allows limiting ARP > > > > > broadcast traffic between nodes. Normally ARP requests are sent to > > > > > broadcast ff:ff:ff:ff:ff:ff ethernet, as the protocol is designed to > > > > > identify ethernet addresses for known IP addresses. In this case since > > > > > traffic is broadcast it will be flooded among all nodes if ARP > > > responder is > > > > > not applied. At the same time the client may specify the target > > > > > ethernet address as unicast (in this case a broadcast storm will not > > > > > happen, as the destination ethernet address is unicast). > > > > > > > > > > In OpenStack we use unicast ARP requests as a way to monitor VM > > > aliveness > > > > > from remote locations to make sure there are no issues with > > > > > flows/underlying networking infra between nodes. We use ARPs due to > > > several > > > > > reasons: > > > > > 1. This protocol is mandatory and can't be disabled on the target > > > machine > > > > > (which guarantees that the target VM will always reply to ARPs if it is > > > > > alive) > > > > > 2. This protocol is not filtered by firewalls/security groups as it is > > > > > mandatory for network workability > > > > > 3. We can't use upper layers protocols such as ICMP as they will > > > require > > > > > specific firewall rules inside VMs, and we do not control VMs in cloud > > > > > cases, but still need to monitor infrastructure aliveness. > > > > > > > > > > If ARP responder replies to requests with broadcast and unicast target > > > > > ethernet address, we can't use this technique for monitoring, as even > > > if > > > > > target VM is down (not necessary that ovn port is down, the VM may > > > stuck or > > > > > be in kernel panic for example, or datapath between monitoring tool > > > and VM > > > > > is broken) the ARP responder will do reply to our request so we can't > > > > > identify if VM is really accessible or not as we will always got > > > replies > > > > > from local ARP responder. At the same time there is no need to set up > > > ARP > > > > > responder for requests with a unicast ethernet address, as they will > > > not > > > > > generate broadcast storms by design (they are unicasts). > > > > > > > > > > > > > Right, this sounds acceptable to me too. > > > > > > > > > > > > > >> 1. Accept your patch > > > > >> 2. Use the NB Global option - "ignore_lsp_down" and set it to false, > > > > >> so that ovn-northd will install the ARP responder flows only if the > > > > >> logical port is up. > > > > >> > > > > > This option will not allow catching a situation when there is an issue > > > in > > > > > datapath between monitoring software and VM located on another node, > > > for > > > > > example issues with flows or some underlying networking problems. > > > > > > > > > > Have you considered this approach for your use case ? > > > > >> 3. Add another global option - "disable_arp_responder" which when set > > > > >> to true, ovn-northd will not install ARP responder flows. > > > > >> > > > > >> Disabling ARP responder for ports completely will allow broadcast > > > storms > > > > > for ARP requests. Which we would like to avoid, but enable the > > > possibility > > > > > to monitor infrastructure aliveness. > > > > > > > > > > > > > > >> Given that OpenStack neutron ml2ovs uses ARP responder flows only for > > > > >> broad cast my preference would be (1). > > > > >> > > > > >> I'd like to know other's opinion on this. > > > > >> > > > > > > > > I'd accept the patch too so I'd go for (1). > > > > > > > > Regards, > > > > Dumitru > > > > > > > > >> Thanks > > > > >> Numan > > > > >> > > > > >>> > > > > >>> Closes #239 > > > > >>> > > > > >>> Signed-off-by: Vasyl Saienko <vsaie...@mirantis.com> > > > > >>> --- > > > > >>> northd/northd.c | 11 +++++++++-- > > > > >>> tests/ovn-northd.at | 4 ++-- > > > > >>> 2 files changed, 11 insertions(+), 4 deletions(-) > > > > >>> > > > > >>> diff --git a/northd/northd.c b/northd/northd.c > > > > >>> index 37f443e70..e80e1885d 100644 > > > > >>> --- a/northd/northd.c > > > > >>> +++ b/northd/northd.c > > > > >>> @@ -8832,8 +8832,15 @@ > > > build_lswitch_arp_nd_responder_known_ips(struct > > > > >> ovn_port *op, > > > > >>> for (size_t i = 0; i < op->n_lsp_addrs; i++) { > > > > >>> for (size_t j = 0; j < op->lsp_addrs[i].n_ipv4_addrs; > > > j++) { > > > > >>> ds_clear(match); > > > > >>> - ds_put_format(match, "arp.tpa == %s && arp.op == 1", > > > > >>> - op->lsp_addrs[i].ipv4_addrs[j].addr_s); > > > > >>> + /* NOTE(vsaienko): Do not reply on unicast ARPs, > > > forward > > > > >>> + * them to the target to have ability to monitor > > > target > > > > >>> + * aliveness via ARPs. > > > > >>> + */ > > > > >>> + ds_put_format(match, > > > > >>> + "arp.tpa == %s && " > > > > >>> + "arp.op == 1 && " > > > > >>> + "eth.dst == ff:ff:ff:ff:ff:ff", > > > > >>> + op->lsp_addrs[i].ipv4_addrs[j].addr_s); > > > > >>> ds_clear(actions); > > > > >>> ds_put_format(actions, > > > > >>> "eth.dst = eth.src; " > > > > >>> diff --git a/tests/ovn-northd.at b/tests/ovn-northd.at > > > > >>> index be006fb32..4162196f4 100644 > > > > >>> --- a/tests/ovn-northd.at > > > > >>> +++ b/tests/ovn-northd.at > > > > >>> @@ -9283,9 +9283,9 @@ AT_CAPTURE_FILE([S1flows]) > > > > >>> > > > > >>> AT_CHECK([grep -e "ls_in_arp_rsp" S1flows | ovn_strip_lflows], [0], > > > [dnl > > > > >>> table=??(ls_in_arp_rsp ), priority=0 , match=(1), > > > > >> action=(next;) > > > > >>> - table=??(ls_in_arp_rsp ), priority=100 , match=(arp.tpa == > > > > >> 192.168.0.10 && arp.op == 1 && inport == "S1-vm1"), action=(next;) > > > > >>> + table=??(ls_in_arp_rsp ), priority=100 , match=(arp.tpa == > > > > >> 192.168.0.10 && arp.op == 1 && eth.dst == ff:ff:ff:ff:ff:ff && inport > > > == > > > > >> "S1-vm1"), action=(next;) > > > > >>> table=??(ls_in_arp_rsp ), priority=100 , match=(nd_ns && > > > > >> ip6.dst == {fd00::10, ff02::1:ff00:10} && nd.target == fd00::10 && > > > inport > > > > >> == "S1-vm1"), action=(next;) > > > > >>> - table=??(ls_in_arp_rsp ), priority=50 , match=(arp.tpa == > > > > >> 192.168.0.10 && arp.op == 1), action=(eth.dst = eth.src; eth.src = > > > > >> 50:54:00:00:00:10; arp.op = 2; /* ARP reply */ arp.tha = arp.sha; > > > arp.sha = > > > > >> 50:54:00:00:00:10; arp.tpa = arp.spa; arp.spa = 192.168.0.10; outport > > > = > > > > >> inport; flags.loopback = 1; output;) > > > > >>> + table=??(ls_in_arp_rsp ), priority=50 , match=(arp.tpa == > > > > >> 192.168.0.10 && arp.op == 1 && eth.dst == ff:ff:ff:ff:ff:ff), > > > > >> action=(eth.dst = eth.src; eth.src = 50:54:00:00:00:10; arp.op = 2; > > > /* ARP > > > > >> reply */ arp.tha = arp.sha; arp.sha = 50:54:00:00:00:10; arp.tpa = > > > arp.spa; > > > > >> arp.spa = 192.168.0.10; outport = inport; flags.loopback = 1; output;) > > > > >>> table=??(ls_in_arp_rsp ), priority=50 , match=(nd_ns && > > > > >> ip6.dst == {fd00::10, ff02::1:ff00:10} && nd.target == fd00::10), > > > > >> action=(nd_na { eth.src = 50:54:00:00:00:10; ip6.src = fd00::10; > > > nd.target > > > > >> = fd00::10; nd.tll = 50:54:00:00:00:10; outport = inport; > > > flags.loopback = > > > > >> 1; output; };) > > > > > > I took a look at this patch. There's one problem with this patch. If > > > you see the test case changes, this patch now > > > replaces the below logical flow > > > > > > table=??(ls_in_arp_rsp ), priority=100 , match=(arp.tpa == > > > 192.168.0.10 && arp.op == 1 && inport == "S1-vm1"), action=(next;) > > > > > > with > > > > > > table=??(ls_in_arp_rsp ), priority=100 , match=(arp.tpa == > > > 192.168.0.10 && arp.op == 1 && eth.dst == ff:ff:ff:ff:ff:ff && inport > > > == "S1-vm1"), action=(next;) > > > > > > This is wrong. If there is an ARP request packet entering from a > > > router port to the switch, we were advancing this packet to the next > > > stage. > > > But now, we only advance if it's a broadcast pkt. Please correct this. > > > > > > This does not look wrong, the router is yet another client that uses ARP > > to map IP address to MAC address. > > If the MAC address is known, the router will not send ARP to the target at > > all, in other cases it will send it to broadcast where > > we will reply from the ARP responder. > > Yes. You're right.
The patch looks correct to me, but shall we add the same for IPv6 (just a few lines below this in the same function)? Thanks, Han > > Thanks > Numan > > > > > > > > > > Also please update the logical flow documentation in ovn-northd.8.xml > > > for the "ls_in_arp_rsp" stage. I think its also worth mentioning this > > > change in the > > > NEWS file. > > > > > > Will update in next revision. > > > > > > > Thanks > > > Numan > > > > > > > > > > > > > > > > > > > >>> ]) > > > > >>> > > > > >>> -- > > > > >>> 2.40.1 > > > > >>> > > > > >>> _______________________________________________ > > > > >>> dev mailing list > > > > >>> d...@openvswitch.org > > > > >>> https://mail.openvswitch.org/mailman/listinfo/ovs-dev > > > > >>> > > > > >> > > > > > > > > > > > > > > > > > > _______________________________________________ > > > > dev mailing list > > > > d...@openvswitch.org > > > > https://mail.openvswitch.org/mailman/listinfo/ovs-dev > > > > > > > > > -- > > <https://www.mirantis.com/> > > Vasyl Saienko > > > > Principal DevOps Engineer > > vsaie...@mirantis.com <dstoltenb...@mirantis.com> > > +(380) 66 072 07 17 <++1+(650)+564+7038> > > _______________________________________________ > > dev mailing list > > d...@openvswitch.org > > https://mail.openvswitch.org/mailman/listinfo/ovs-dev > _______________________________________________ > dev mailing list > d...@openvswitch.org > https://mail.openvswitch.org/mailman/listinfo/ovs-dev _______________________________________________ dev mailing list d...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-dev