From: Numan Siddique <[email protected]>
After the commit [1], OVN doesn't reply to the unicast ARP
requests for the known IPs. This patch adds a global option
"unicast_arp_responder" and if set to true, OVN will also
respond to the unicast ARP requests. This gives the option
for deployments which were relying on the older behavior.
However the main reason to add this option is to address
another issue. Consider the below topology where logical switches
sw0 and sw1 are connected lr0. lr0 is also connected to a
public switch which is not shown here.
switch 8144b9c4-b38f-47db-a403-62283c8a5756 (sw0)
port sw0-port2
addresses: ["50:54:00:00:00:04 10.0.0.4"]
port sw0-port1
addresses: ["50:54:00:00:00:03 10.0.0.3"]
port sw0-lr0
type: router
addresses: ["00:00:00:00:ff:01"]
router-port: lr0-sw0
switch 8f53c293-9486-49ff-9e62-98ea3408ee2e (sw1)
port sw1-port2
addresses: ["40:54:00:00:00:04 20.0.0.4"]
port sw1-lr0
type: router
addresses: ["00:00:00:00:ff:02"]
router-port: lr0-sw1
port sw1-port1
addresses: ["40:54:00:00:00:03 20.0.0.3"]
ovn-nbctl lr-nat-list lr0
TYPE EXTERNAL_IP LOGICAL_IP EXTERNAL_MAC
LOGICAL_PORT
dnat_and_snat 172.168.0.110 10.0.0.3 50:54:00:00:00:03
sw0-port1
dnat_and_snat 172.168.0.120 20.0.0.3 40:54:00:00:00:04
sw1-port1
Here the logical port's mac is also used as external mac in the NATs.
ovn-northd adds the below logical flow in both the sw0 and sw1 pipeline
table=28(ls_in_l2_lkup ), priority=75 ,
match=(eth.src == {.., 50:54:00:00:00:03, 40:54:00:00:00:04, ..}
&& (arp.op == 1 || rarp.op == 3 || nd_ns)),
action=(outport = "_MC_flood_l2"; output;)
This lflow is added to broadcast the self originated GARP packets.
Most likely to broadcast the GARPs generated by ovn-controller
and where the router MAC is used as source address [2].
Seems like this flow should have been added only on the logical switches
connected to the router if the IPs are reachable from it.
When sw0-port1 sends a unicast ARP request to any IP in its subnet,
instead of tunneling the packet to the destination chassis, the packet
gets flooded in the L2 domain since the sw0-port1's mac matches this
flow.
Until we fix this logical flow properly, this patch is sufficient to
address the unicast ARP request issue. This causes a flood of
ARP packets in the geneve network.
[1] - c48ed1736a58("Do not reply on unicast arps for IPv4 targets.")
[2] - 32f5ebb06226 ("ovn-northd: Limit ARP/ND broadcast domain whenever
possible.")
Signed-off-by: Numan Siddique <[email protected]>
---
northd/en-global-config.c | 6 ++++++
northd/northd.c | 26 +++++++++++++++++---------
ovn-nb.xml | 9 +++++++++
tests/ovn-northd.at | 19 +++++++++++++++++--
4 files changed, 49 insertions(+), 11 deletions(-)
diff --git a/northd/en-global-config.c b/northd/en-global-config.c
index c103b137f6..d9b7dcb0a8 100644
--- a/northd/en-global-config.c
+++ b/northd/en-global-config.c
@@ -269,6 +269,12 @@ global_config_nb_global_handler(struct engine_node *node,
void *data)
return false;
}
+ /* Check if northd_internal_version has changed or not. */
+ if (config_out_of_sync(&nb->options, &config_data->nb_options,
+ "unicast_arp_responder", false)) {
+ return false;
+ }
+
if (check_nb_options_out_of_sync(nb, config_data, sampling_apps)) {
config_data->tracked_data.nb_options_changed = true;
}
diff --git a/northd/northd.c b/northd/northd.c
index 880ec92ac2..78a7125ce1 100644
--- a/northd/northd.c
+++ b/northd/northd.c
@@ -98,6 +98,9 @@ static bool vxlan_mode;
static bool vxlan_ic_mode;
+/* Respond to unicast ARP requests for known ips or not. */
+static bool unicast_arp_responder = false;
+
#define MAX_OVN_TAGS 4096
@@ -9515,15 +9518,16 @@ 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);
- /* Do not reply on unicast ARPs, forward them to the target
- * to have ability to monitor target liveness via unicast
- * ARP requests.
- */
- 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_put_format(match, "arp.tpa == %s && arp.op == 1",
+ op->lsp_addrs[i].ipv4_addrs[j].addr_s);
+
+ if (!unicast_arp_responder) {
+ /* Do not reply on unicast ARPs, forward them to the target
+ * to have ability to monitor target liveness via unicast
+ * ARP requests.
+ */
+ ds_put_cstr(match, " && eth.dst == ff:ff:ff:ff:ff:ff");
+ }
ds_clear(actions);
ds_put_format(actions,
"eth.dst = eth.src; "
@@ -18980,6 +18984,10 @@ ovnnb_db_run(struct northd_input *input_data,
use_common_zone = smap_get_bool(input_data->nb_options, "use_common_zone",
false);
+ unicast_arp_responder = smap_get_bool(input_data->nb_options,
+ "unicast_arp_responder",
+ false);
+
vxlan_mode = is_vxlan_mode(input_data->nb_options,
input_data->sbrec_chassis_table);
diff --git a/ovn-nb.xml b/ovn-nb.xml
index bf1f1628bd..7f8021667c 100644
--- a/ovn-nb.xml
+++ b/ovn-nb.xml
@@ -429,6 +429,15 @@
</p>
</column>
+ <column name="options" key="unicast_arp_responder" type='{"type":
"boolean"}'>
+ <p>
+ <code>ovn-northd</code> adds ARP responder flows for known IPs for
+ broadcast ARP request packets. If this option is set, it will also
+ respond to unicast ARP requests. By default this option is set to
+ <code>false</code>.
+ </p>
+ </column>
+
<group title="Options for configuring interconnection route
advertisement">
<p>
These options control how routes are advertised between OVN
diff --git a/tests/ovn-northd.at b/tests/ovn-northd.at
index e3a65e7a44..f0322a311c 100644
--- a/tests/ovn-northd.at
+++ b/tests/ovn-northd.at
@@ -9869,7 +9869,7 @@ AT_CLEANUP
])
OVN_FOR_EACH_NORTHD_NO_HV([
-AT_SETUP([check options:disable_arp_nd_rsp for LSP])
+AT_SETUP([ARP responder flows])
ovn_start NORTHD_TYPE
check ovn-nbctl ls-add S1
check ovn-nbctl --wait=sb lsp-add S1 S1-vm1
@@ -9886,7 +9886,22 @@ AT_CHECK([grep -e "ls_in_arp_rsp" S1flows |
ovn_strip_lflows], [0], [dnl
table=??(ls_in_arp_rsp ), priority=50 , match=(nd_ns_mcast && ip6.dst
== 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; };)
])
-#Set the disable_arp_nd_rsp option and verify the flow
+check ovn-nbctl set NB_Global . options:unicast_arp_responder=true
+check ovn-nbctl --wait=sb sync
+
+ovn-sbctl dump-flows S1 > S1flows
+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=(nd_ns_mcast && ip6.dst
== 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=(nd_ns_mcast && ip6.dst
== 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; };)
+])
+
+
+# Set the disable_arp_nd_rsp option and verify the flow
check ovn-nbctl --wait=sb set logical_switch_port S1-vm1
options:disable_arp_nd_rsp=true
ovn-sbctl dump-flows S1 > S1flows
--
2.49.0
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