northd: Respect --ecmp-symmetric-reply for single routes.

When preparing to build ECMP and static route flows, routes are sorted into unique routes (meaning they are not part of a group) or they are added to EMCP groups. Then, ECMP route flows are built out of the groups, and static route flows are built out of the unique routes. However, 'unique routes' include ones that use the --ecmp-symmetric-reply flag, meaning that they may not be added to an ECMP group, and thus ECMP symmetric reply would not be used for those flows. For example, if one route is added and traffic is started, and then later another route is added, the already flowing traffic might be rerouted since it wasn't conntracked initially. This could break symmetric reply with traffic using a different next-hop than before. This change makes it so that when the --ecmp-symmetric-reply flag is used, even for unique routes, an ECMP group is created which they are added to. Thus they are added to the ECMP route flow, rather than static. This allows ECMP groups to persist even when there is only one route. Edited documentation to support this change. Also updated incorrect actions in documentation. Fixes: 4fdca65 ("Add ECMP symmetric replies.") Reported-at: https://issues.redhat.com/browse/FDP-786 Signed-off-by: Rosemarie O'Riorden <[email protected]>
roseoriorden · Sep 20, 2024 · 5f6fa25 · 5f6fa25
1 parent 90f5a32
commit 5f6fa25
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Showing 4 changed files with 70 additions and 14 deletions.
diff --git a/northd/northd.c b/northd/northd.c
@@ -11565,21 +11565,27 @@ build_ecmp_route_flow(struct lflow_table *lflows, struct ovn_datapath *od,
 
     struct ds actions = DS_EMPTY_INITIALIZER;
     ds_put_format(&actions, "ip.ttl--; flags.loopback = 1; %s = %"PRIu16
-                  "; %s = select(", REG_ECMP_GROUP_ID, eg->id,
-                  REG_ECMP_MEMBER_ID);
+                  "; %s = ", REG_ECMP_GROUP_ID, eg->id, REG_ECMP_MEMBER_ID);
 
-    bool is_first = true;
-    LIST_FOR_EACH (er, list_node, &eg->route_list) {
-        if (is_first) {
-            is_first = false;
-        } else {
-            ds_put_cstr(&actions, ", ");
+    if (!ovs_list_is_singleton(&eg->route_list)) {
+        bool is_first = true;
+
+        ds_put_cstr(&actions, "select(");
+        LIST_FOR_EACH (er, list_node, &eg->route_list) {
+            if (is_first) {
+                is_first = false;
+            } else {
+                ds_put_cstr(&actions, ", ");
+            }
+            ds_put_format(&actions, "%"PRIu16, er->id);
         }
-        ds_put_format(&actions, "%"PRIu16, er->id);
+        ds_put_cstr(&actions, ");");
+    } else {
+        er = CONTAINER_OF(ovs_list_front(&eg->route_list),
+                          struct ecmp_route_list_node, list_node);
+        ds_put_format(&actions, "%"PRIu16"; next;", er->id);
     }
 
-    ds_put_cstr(&actions, ");");
-
     ovn_lflow_add(lflows, od, S_ROUTER_IN_IP_ROUTING, priority,
                   ds_cstr(&route_match), ds_cstr(&actions),
                   lflow_ref);
@@ -13541,6 +13547,11 @@ build_static_route_flows_for_lrouter(
                 if (group) {
                     ecmp_groups_add_route(group, route);
                 }
+            } else if (route->ecmp_symmetric_reply) {
+                /* Traffic for symmetric reply routes has to be conntracked
+                 * even if there is only one next-hop, in case another next-hop
+                 * is added later. */
+                ecmp_groups_add(&ecmp_groups, route);
             } else {
                 unique_routes_add(&unique_routes, route);
             }

diff --git a/northd/ovn-northd.8.xml b/northd/ovn-northd.8.xml
@@ -4328,7 +4328,18 @@ next;
 ip.ttl--;
 flags.loopback = 1;
 reg8[0..15] = <var>GID</var>;
-select(reg8[16..31], <var>MID1</var>, <var>MID2</var>, ...);
+reg8[16..31] = select(<var>MID1</var>, <var>MID2</var>, ...);
+        </pre>
+        <p>
+          However, when there is only one route in an ECMP group, group actions
+          will be:
+        </p>
+
+        <pre>
+ip.ttl--;
+flags.loopback = 1;
+reg8[0..15] = <var>GID</var>;
+reg8[16..31] = <var>MID1</var>);
         </pre>
       </li>
 

diff --git a/tests/ovn-northd.at b/tests/ovn-northd.at
@@ -6799,20 +6799,23 @@ check ovn-nbctl lsp-set-type public-lr0 router
 check ovn-nbctl lsp-set-addresses public-lr0 router
 check ovn-nbctl lsp-set-options public-lr0 router-port=lr0-public
 
+# ECMP flows will be added even if there is only one next-hop.
 check ovn-nbctl --wait=sb --ecmp-symmetric-reply lr-route-add lr0 1.0.0.1 192.168.0.10
 
 ovn-sbctl dump-flows lr0 > lr0flows
 
 AT_CHECK([grep -w "lr_in_ip_routing" lr0flows | ovn_strip_lflows], [0], [dnl
   table=??(lr_in_ip_routing   ), priority=0    , match=(1), action=(drop;)
+  table=??(lr_in_ip_routing   ), priority=10300, match=(ct_mark.ecmp_reply_port == 1 && reg7 == 0 && ip4.dst == 1.0.0.1/32), action=(ip.ttl--; flags.loopback = 1; eth.src = 00:00:20:20:12:13; reg1 = 192.168.0.1; outport = "lr0-public"; next;)
   table=??(lr_in_ip_routing   ), priority=10550, match=(nd_rs || nd_ra), action=(drop;)
   table=??(lr_in_ip_routing   ), priority=194  , match=(inport == "lr0-public" && ip6.dst == fe80::/64), action=(ip.ttl--; reg8[[0..15]] = 0; xxreg0 = ip6.dst; xxreg1 = fe80::200:20ff:fe20:1213; eth.src = 00:00:20:20:12:13; outport = "lr0-public"; flags.loopback = 1; next;)
   table=??(lr_in_ip_routing   ), priority=74   , match=(ip4.dst == 192.168.0.0/24), action=(ip.ttl--; reg8[[0..15]] = 0; reg0 = ip4.dst; reg1 = 192.168.0.1; eth.src = 00:00:20:20:12:13; outport = "lr0-public"; flags.loopback = 1; next;)
-  table=??(lr_in_ip_routing   ), priority=97   , match=(reg7 == 0 && ip4.dst == 1.0.0.1/32), action=(ip.ttl--; reg8[[0..15]] = 0; reg0 = 192.168.0.10; reg1 = 192.168.0.1; eth.src = 00:00:20:20:12:13; outport = "lr0-public"; flags.loopback = 1; next;)
+  table=??(lr_in_ip_routing   ), priority=97   , match=(reg7 == 0 && ip4.dst == 1.0.0.1/32), action=(ip.ttl--; flags.loopback = 1; reg8[[0..15]] = 1; reg8[[16..31]] = 1; next;)
 ])
 
 AT_CHECK([grep -e "lr_in_ip_routing_ecmp" lr0flows | ovn_strip_lflows], [0], [dnl
   table=??(lr_in_ip_routing_ecmp), priority=0    , match=(1), action=(drop;)
+  table=??(lr_in_ip_routing_ecmp), priority=100  , match=(reg8[[0..15]] == 1 && reg8[[16..31]] == 1), action=(reg0 = 192.168.0.10; reg1 = 192.168.0.1; eth.src = 00:00:20:20:12:13; outport = "lr0-public"; next;)
   table=??(lr_in_ip_routing_ecmp), priority=150  , match=(reg8[[0..15]] == 0), action=(next;)
 ])
 

diff --git a/tests/system-ovn.at b/tests/system-ovn.at
@@ -6241,6 +6241,22 @@ sed -e 's/mark=[[0-9]]*/mark=<cleared>/' | sort], [0], [dnl
 tcp,orig=(src=172.16.0.1,dst=10.0.0.2,sport=<cleared>,dport=<cleared>),reply=(src=10.0.0.2,dst=172.16.0.1,sport=<cleared>,dport=<cleared>),zone=<cleared>,mark=<cleared>,labels=0x401020500000000,protoinfo=(state=<cleared>)
 ])
 
+# Now remove one ECMP route and check that traffic is still being conntracked.
+check ovn-nbctl --policy="src-ip" lr-route-del R1 10.0.0.0/24 20.0.0.3
+check ovn-nbctl --wait=hv sync
+AT_CHECK([ovs-appctl dpctl/flush-conntrack])
+NETNS_DAEMONIZE([bob1], [nc -l -k 8081], [bob2.pid])
+NS_CHECK_EXEC([alice1], [nc -z 172.16.0.1 8081], [0])
+NS_CHECK_EXEC([alice1], [ping -q -c 3 -i 0.3 -w 2 172.16.0.1 | FORMAT_PING], \
+[0], [dnl
+3 packets transmitted, 3 received, 0% packet loss, time 0ms
+])
+AT_CHECK([ovs-appctl dpctl/dump-conntrack | grep 0x401020500000000 | FORMAT_CT(172.16.0.1) | \
+sed -e 's/zone=[[0-9]]*/zone=<cleared>/' |
+sed -e 's/mark=[[0-9]]*/mark=<cleared>/' | sort], [0], [dnl
+tcp,orig=(src=172.16.0.1,dst=10.0.0.2,sport=<cleared>,dport=<cleared>),reply=(src=10.0.0.2,dst=172.16.0.1,sport=<cleared>,dport=<cleared>),zone=<cleared>,mark=<cleared>,labels=0x401020500000000,protoinfo=(state=<cleared>)
+])
+
 OVS_APP_EXIT_AND_WAIT([ovn-controller])
 
 as ovn-sb
@@ -6255,7 +6271,6 @@ OVS_APP_EXIT_AND_WAIT([ovn-northd])
 as
 OVS_TRAFFIC_VSWITCHD_STOP(["/failed to query port patch-.*/d
 /connection dropped.*/d"])
-
 AT_CLEANUP
 ])
 
@@ -6457,6 +6472,22 @@ sed -e 's/mark=[[0-9]]*/mark=<cleared>/' | sort], [0], [dnl
 tcp,orig=(src=fd07::1,dst=fd01::2,sport=<cleared>,dport=<cleared>),reply=(src=fd01::2,dst=fd07::1,sport=<cleared>,dport=<cleared>),zone=<cleared>,mark=<cleared>,labels=0x1001020400000000,protoinfo=(state=<cleared>)
 ])
 
+# Now remove one ECMP route and check that traffic is still being conntracked.
+check ovn-nbctl --policy="src-ip" lr-route-del R1 fd01::/126 fd02::3
+check ovn-nbctl --wait=hv sync
+AT_CHECK([ovs-appctl dpctl/flush-conntrack])
+NETNS_DAEMONIZE([bob1], [nc -6 -l -k 8081], [bob2.pid])
+NS_CHECK_EXEC([alice1], [nc -6 -z fd07::1 8081], [0])
+NS_CHECK_EXEC([alice1], [ping -q -c 3 -i 0.3 -w 2 fd07::1 | FORMAT_PING], \
+[0], [dnl
+3 packets transmitted, 3 received, 0% packet loss, time 0ms
+])
+AT_CHECK([ovs-appctl dpctl/dump-conntrack | grep 0x1001020400000000 | FORMAT_CT(fd07::1) | \
+sed -e 's/zone=[[0-9]]*/zone=<cleared>/' |
+sed -e 's/mark=[[0-9]]*/mark=<cleared>/' | sort], [0], [dnl
+tcp,orig=(src=fd07::1,dst=fd01::2,sport=<cleared>,dport=<cleared>),reply=(src=fd01::2,dst=fd07::1,sport=<cleared>,dport=<cleared>),zone=<cleared>,mark=<cleared>,labels=0x1001020400000000,protoinfo=(state=<cleared>)
+])
+
 OVS_APP_EXIT_AND_WAIT([ovn-controller])
 
 as ovn-sb