Hi all, As this thread is getting big I'm summarizing the issue I see so far:
* When a dnat_and_snat entry is added to a logical router (or port gets bound to a chassis), ovn-controller will send GARPs to announce the MAC address of the FIP(s) (either the gw port or of the actual FIP MAC address if distributed) only through localnet ports [0]. * This means that gateway ports bound to that same chassis and connected to the public switch won't get the GARPs, so they won't update their MAC_Binding entries causing unreachability. In the diagram of this thread, LR0 won't get the GARP sent by ovn-controller if both gateway ports are bound to the same chassis. I tried out sending GARPs from the external network using master branch and MAC_Binding entries get updated. However, in order to cover missing cases, I think it would make sense to send the GARPs not only to localnet ports but to all ports of those logical switches that have a localnet port. What do you think? [0] https://github.com/openvswitch/ovs/blob/master/ovn/controller/pinctrl.c#L2073 [0] https://github.com/openvswitch/ovs/blob/master/ovn/controller/pinctrl.c#L2073On Fri, Nov 23, 2018 at 5:28 PM Daniel Alvarez Sanchez <dalva...@redhat.com> wrote: > > On Wed, Nov 21, 2018 at 9:04 PM Han Zhou <zhou...@gmail.com> wrote: > > > > > > > > On Tue, Nov 20, 2018 at 5:21 AM Mark Michelson <mmich...@redhat.com> wrote: > > > > > > Hi Daniel, > > > > > > I agree with Numan that this seems like a good approach to take. > > > > > > On 11/16/2018 12:41 PM, Daniel Alvarez Sanchez wrote: > > > > > > > > On Sat, Nov 10, 2018 at 12:21 AM Ben Pfaff <b...@ovn.org > > > > <mailto:b...@ovn.org>> wrote: > > > > > > > > > > On Mon, Oct 29, 2018 at 05:21:13PM +0530, Numan Siddique wrote: > > > > > > On Mon, Oct 29, 2018 at 5:00 PM Daniel Alvarez Sanchez > > > > <dalva...@redhat.com <mailto:dalva...@redhat.com>> > > > > > > wrote: > > > > > > > > > > > > > Hi, > > > > > > > > > > > > > > After digging further. The problem seems to be reduced to > > > > reusing an > > > > > > > old gateway IP address for a dnat_and_snat entry. > > > > > > > When a gateway port is bound to a chassis, its entry will show > > > > up in > > > > > > > the MAC_Binding table (at least when that Logical Switch is > > > > connected > > > > > > > to more than one Logical Router). After deleting the Logical > > > > Router > > > > > > > and all its ports, this entry will remain there. If a new Logical > > > > > > > Router is created and a Floating IP (dnat_and_snat) is assigned > > > > to a > > > > > > > VM with the old gw IP address, it will become unreachable. > > > > > > > > > > > > > > A workaround now from networking-ovn (OpenStack integration) is > > > > to > > > > > > > delete MAC_Binding entries for that IP address upon a FIP > > > > creation. I > > > > > > > think that this however should be done from OVN, what do you > > > > folks > > > > > > > think? > > > > > > > > > > > > > > > > > > > > Agree. Since the MAC_Binding table row is created by > > > > ovn-controller, it > > > > > > should > > > > > > be handled properly within OVN. > > > > > > > > > > I see that this has been sitting here for a while. The solution > > > > seems > > > > > reasonable to me. Are either of you working on it? > > > > > > > > I started working on it. I came up with a solution (see patch below) > > > > which works but I wanted to give you a bit more of context and get your > > > > feedback: > > > > > > > > > > > > ^ localnet > > > > | > > > > +---+---+ > > > > | | > > > > +------+ pub +------+ > > > > | | | | > > > > | +-------+ | > > > > | 172.24.4.0/24 <http://172.24.4.0/24> | > > > > | | > > > > 172.24.4.220 | | 172.24.4.221 > > > > +---+---+ +---+---+ > > > > | | | | > > > > | LR0 | | LR1 | > > > > | | | | > > > > +---+---+ +---+---+ > > > > 10.0.0.254 | | 20.0.0.254 > > > > | | > > > > +---+---+ +---+---+ > > > > | | | | > > > > 10.0.0.0/24 <http://10.0.0.0/24> | SW0 | | SW1 | > > > > 20.0.0.0/24 <http://20.0.0.0/24> > > > > | | | | > > > > +---+---+ +---+---+ > > > > | | > > > > | | > > > > +---+---+ +---+---+ > > > > | | | | > > > > | VM0 | | VM1 | > > > > | | | | > > > > +-------+ +-------+ > > > > 10.0.0.10 20.0.0.10 > > > > 172.24.4.100 172.24.4.200 > > > > > > > > > > > > When I ping VM1 floating IP from the external network, a new entry for > > > > 172.24.4.221 in the LR0 datapath appears in the MAC_Binding table: > > > > > > > > _uuid : 85e30e87-3c59-423e-8681-ec4cfd9205f9 > > > > datapath : ac5984b9-0fea-485f-84d4-031bdeced29b > > > > ip : "172.24.4.221" > > > > logical_port : "lrp02" > > > > mac : "00:00:02:01:02:04" > > > > > > > > > > > > Now, if LR1 gets removed and the old gateway IP (172.24.4.221) is reused > > > > for VM2 FIP with different MAC and new gateway IP is created (for > > > > example 172.24.4.222 00:00:02:01:02:99), VM2 FIP becomes unreachable > > > > from VM1 until the old MAC_Binding entry gets deleted as pinging > > > > 172.24.4.221 will use the wrong address ("00:00:02:01:02:04"). > > > > > > > > With the patch below, removing LR1 results in deleting all MAC_Binding > > > > entries for every datapath where '172.24.4.221' appears in the 'ip' > > > > column so the problem goes away. > > > > > > > > Another solution would be implementing some kind of 'aging' for > > > > MAC_Binding entries but perhaps it's more complex. > > > > Looking forward for your comments :) > > > > > > > > > > > > diff --git a/ovn/northd/ovn-northd.c b/ovn/northd/ovn-northd.c > > > > index 58bef7d..a86733e 100644 > > > > --- a/ovn/northd/ovn-northd.c > > > > +++ b/ovn/northd/ovn-northd.c > > > > @@ -2324,6 +2324,18 @@ cleanup_mac_bindings(struct northd_context *ctx, > > > > struct hmap *ports) > > > > } > > > > } > > > > > > > > +static void > > > > +delete_mac_binding_by_ip(struct northd_context *ctx, const char *ip) > > > > +{ > > > > + const struct sbrec_mac_binding *b, *n; > > > > + SBREC_MAC_BINDING_FOR_EACH_SAFE (b, n, ctx->ovnsb_idl) { > > > > + if (strstr(ip, b->ip)) { > > > > + sbrec_mac_binding_delete(b); > > > > + } > > > > + } > > > > +} > > > > + > > > > + > > > > /* Updates the southbound Port_Binding table so that it contains the > > > > logical > > > > * switch ports specified by the northbound database. > > > > * > > > > @@ -2383,6 +2395,15 @@ build_ports(struct northd_context *ctx, > > > > /* Delete southbound records without northbound matches. */ > > > > LIST_FOR_EACH_SAFE(op, next, list, &sb_only) { > > > > ovs_list_remove(&op->list); > > > > + > > > > + /* Delete all MAC_Binding entries which match the IP addresses > > > > of the > > > > + * deleted logical router port (ie. port with a peer). */ > > > > + const char *peer = smap_get(&op->sb->options, "peer"); > > > > + if (peer) { > > > > + for (int i = 0; i < op->sb->n_mac; i++) { > > > > + delete_mac_binding_by_ip(ctx, op->sb->mac[i]); > > > > + } > > > > + } > > > > sbrec_port_binding_delete(op->sb); > > > > ovn_port_destroy(ports, op); > > > > } > > > > > > > > Hi, > > > > Sorry that I didn't notice this discussion until now. I encountered similar > > problems before. It was not in floating IP scenario, but for external IPs - > > ports on the same networks but not aware by OVN. When IP relocates from one > > MAC to another, the previous mac-binding entry will not get updated and > > therefore the re-located IP is unreachable. > > > > This happens for external router IPs on the localnet network behind the > > gateways (which hosts the 172.24.4.221 port in Daniel's example). It also > > happens for nested workloads that run inside a VM - the VM port is known by > > OVN, but the internal workloads (e.g. containers) runs on same subnets but > > relies on mac-binding to communicate. > > > > For both of my use cases, the problem has been solved by this patch > > (merged): > > https://github.com/openvswitch/ovs/commit/b068454082f5d76727ffde34542ff19fed20e178 > > > > The idea is, mac-binding entry should be updated when the IP is announced > > in a new location by GARP/ARP request/ARP response. So I think the best way > > to solve the problem for floating IP is similar. We just need to generate > > GARP when a new FIP is attached. I was under the impression that OVN > > already supports GARP when a new NAT entry is added. But if the problem is > > still there it means something is wrong there (or the GARP feature is not > > there yet for the NAT case), and I need to check the code. > > I think we're only sending the GARPs only for distributed floating IPs > (nat_addresses field in the Port_Binding table) [0]. > Anyways even with that, I'm not quite sure if the MAC_Binding table > would get updated as I think that first time I hit this issue it was > on a DVR environment (ie. distributed FIPs, dnat_and_snat entries with > a logical_port and external_mac). > > [0] > https://github.com/openvswitch/ovs/blob/master/ovn/controller/pinctrl.c#L2497 > > > > For the patch proposed in this discussion, I think there are two problems. > > > > Firstly, I think it doesn't solve the problem completely. It only deletes > > mac-binding when a logical router port is deleted. However, in any of the > > above use cases (including FIP), IP relocation can happen without deleting > > the router port. Or did I misunderstood anything here? > > > > Secondly, northd just reconciles between current state and desired state > > for SB - it is declarative. We should avoid relying on the northd cleanup > > logic to trigger important operations. I think the design principle of > > northd should be making sure the desired state is reached, but not care > > about how is it reached. For example, it can be reached by deleting extra > > records one by one, but it is also correct if it deletes everything and > > recreate the desired entries - this is just an example, it may be > > inefficient, but it may be reasonable in some scenarios. Adding logic in > > northd that relies on *how* the desired state is computed would make it > > unreliable and hard to maintain. I think it would also create challenges > > for the DDlog implementation. > > > > For the mac-binding aging mechanism mentioned by Daniel, I agree. It is > > required for fault scenarios when SB is temporarily down. Since we rely on > > SB DB to store the ARP cache/Neighbor table for the virtual routers, if ARP > > updates happens when the DB is down, changes are lost. However, the aging > > mechanism seems tricky when scale is considered. Only the idle entries > > should be timed out, but it is costly to update states whenever a > > mac-binding entry is hit. I haven't thought about any clever way to achieve > > it without sacrificing scalability. Any thoughts here? A workaround to the > > problem is to resend GARP periodically (e.g. every 1 min). > > > > Thanks, > > Han _______________________________________________ discuss mailing list disc...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-discuss
