On Thu, May 23, 2024 at 1:51 PM Vasyl Saienko <[email protected]> wrote: > > Thanks for feedback, > > I'm not an ipv6 expert, I did some research. There is no ARP in ipv6, it's replaced with Neighbor Discovery. The ARP resolution is done via Neighbor Solicitation and Neighbour Advertisement messages. > Neighbor Solicitation is an analog of ARP request and is sent to either > > solicited-node multicast address 33:33:ff:XX:XX:XX where XX:XX:XX is the last 3 bytes of the target ipv6 address > or target node address > > So in our case we can update the flows to match only the solicited-node multicast address 33:33:ff:XX:XX:XX as follows. From > > 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=(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; };) > > to > > table=??(ls_in_arp_rsp ), priority=100 , match=(nd_ns && eth.dst == {33:33:ff:00:00:10, 33:33:ff:ff:00:10} && 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=(nd_ns && eth.dst == {33:33:ff:00:00:10, 33:33:ff:ff:00:10} && 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; };) > > Will this be okay? Maybe we can do this in a separate patch? > I am not an IPv6 expert either. I even forgot that IPv6 NS uses multicast instead of broadcast MAC address, and was assuming we could simply append the eth.dst == ff:ff:ff:ff:ff:ff to the IPv6 NS responder flows, which is obviously wrong. Please ignore my feedback for the current patch and we can address IPv6 in a separate patch if it is required.
Thanks, Han > On Wed, May 22, 2024 at 12:16 AM Han Zhou <[email protected]> wrote: >> >> >> >> On Tue, May 21, 2024 at 9:56 PM Numan Siddique <[email protected]> wrote: >> > >> > On Mon, May 20, 2024 at 1:47 AM Vasyl Saienko <[email protected]> wrote: >> > > >> > > Thanks for feedback Numan. >> > > >> > > On Wed, May 15, 2024 at 12:04 AM Numan Siddique <[email protected]> wrote: >> > > >> > > > On Mon, May 13, 2024 at 9:00 AM Dumitru Ceara <[email protected]> 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 <[email protected]> wrote: >> > > > > > >> > > > > >> On Mon, Apr 22, 2024 at 2:54 AM Vasyl Saienko < [email protected]> >> > > > > >> 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 <[email protected]> >> > > > > >>> --- >> > > > > >>> 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 >> > > > > >>> [email protected] >> > > > > >>> https://mail.openvswitch.org/mailman/listinfo/ovs-dev >> > > > > >>> >> > > > > >> >> > > > > > >> > > > > > >> > > > > >> > > > > _______________________________________________ >> > > > > dev mailing list >> > > > > [email protected] >> > > > > https://mail.openvswitch.org/mailman/listinfo/ovs-dev >> > > > >> > > >> > > >> > > -- >> > > <https://www.mirantis.com/> >> > > Vasyl Saienko >> > > >> > > Principal DevOps Engineer >> > > [email protected] <[email protected]> >> > > +(380) 66 072 07 17 <++1+(650)+564+7038> >> > > _______________________________________________ >> > > dev mailing list >> > > [email protected] >> > > https://mail.openvswitch.org/mailman/listinfo/ovs-dev >> > _______________________________________________ >> > dev mailing list >> > [email protected] >> > https://mail.openvswitch.org/mailman/listinfo/ovs-dev > > > > -- > > Vasyl Saienko > > Principal DevOps Engineer > > [email protected] > +(380) 66 072 07 17 > _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
