diff mbox series

[ovs-dev,v7,2/3] northd: enable check_pkt_larger for gw router

Message ID 9cff04487e6483cc67f572b5a30b9de84f1ed865.1627405420.git.lorenzo.bianconi@redhat.com
State Accepted
Headers show
Series Introduce check_pkt_larger for ingress traffic | expand

Checks

Context Check Description
ovsrobot/apply-robot success apply and check: success

Commit Message

Lorenzo Bianconi July 27, 2021, 5:05 p.m. UTC
As it is already done for distributed gw router scenario, introduce
check_pkt_larger logical flows for gw router use case.

Acked-by: Mark D. Gray <mark.d.gray@redhat.com>
Co-authored-by: Numan Siddique <numans@ovn.org>
Signed-off-by: Numan Siddique <numans@ovn.org>
Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
---
 northd/ovn-northd.8.xml |  24 ++++----
 northd/ovn-northd.c     |  30 +++++++---
 northd/ovn_northd.dl    |  92 ++++++++++++++++++++++++++++--
 tests/ovn-northd.at     | 121 ++++++++++++++++++++++++++++++++++++++++
 tests/ovn.at            |  47 ++++++++++++++++
 5 files changed, 288 insertions(+), 26 deletions(-)

Comments

Mark Gray July 28, 2021, 8:13 a.m. UTC | #1
On 27/07/2021 18:05, Lorenzo Bianconi wrote:
>  set and the 'REGBIT_PKT_LARGER' register bit
> + * is set, generate ICMPv4/ICMPv6 packet with type 3/2 (Destination
> + * Unreachable/Packet Too Big) and * code 

I think the '*' is not required. Maybe a maintainer can remove it on merge.
Lorenzo Bianconi July 28, 2021, 12:34 p.m. UTC | #2
> On 27/07/2021 18:05, Lorenzo Bianconi wrote:
> >  set and the 'REGBIT_PKT_LARGER' register bit
> > + * is set, generate ICMPv4/ICMPv6 packet with type 3/2 (Destination
> > + * Unreachable/Packet Too Big) and * code 
> 
> I think the '*' is not required. Maybe a maintainer can remove it on merge.
> 

I am fine to repost, just let me know :)

Regards,
Lorenzo
Mark Gray July 28, 2021, 12:43 p.m. UTC | #3
On 28/07/2021 13:34, Lorenzo Bianconi wrote:
>> On 27/07/2021 18:05, Lorenzo Bianconi wrote:
>>>  set and the 'REGBIT_PKT_LARGER' register bit
>>> + * is set, generate ICMPv4/ICMPv6 packet with type 3/2 (Destination
>>> + * Unreachable/Packet Too Big) and * code 
>>
>> I think the '*' is not required. Maybe a maintainer can remove it on merge.
>>
> 
> I am fine to repost, just let me know :)
> 
> Regards,
> Lorenzo
> 

Your call, it has my ack anyway

Acked-by: Mark D. Gray <mark.d.gray@redhat.com>
diff mbox series

Patch

diff --git a/northd/ovn-northd.8.xml b/northd/ovn-northd.8.xml
index 99a19f853..9906a1a4c 100644
--- a/northd/ovn-northd.8.xml
+++ b/northd/ovn-northd.8.xml
@@ -3673,13 +3673,13 @@  outport = <var>P</var>
     <h3>Ingress Table 15: Check packet length</h3>
 
     <p>
-      For distributed logical routers with distributed gateway port configured
-      with <code>options:gateway_mtu</code> to a valid integer value, this
-      table adds a priority-50 logical flow with the match
-      <code>ip4 &amp;&amp; outport == <var>GW_PORT</var></code> where
-      <var>GW_PORT</var> is the distributed gateway router port and applies the
-      action <code>check_pkt_larger</code> and advances the packet to the
-      next table.
+      For distributed logical routers or gateway routers with gateway
+      port configured with <code>options:gateway_mtu</code> to a valid
+      integer value, this table adds a priority-50 logical flow with
+      the match <code>outport == <var>GW_PORT</var></code> where
+      <var>GW_PORT</var> is the gateway router port and applies the
+      action <code>check_pkt_larger</code> and advances the packet to
+      the next table.
     </p>
 
     <pre>
@@ -3703,14 +3703,14 @@  REGBIT_PKT_LARGER = check_pkt_larger(<var>L</var>); next;
     <h3>Ingress Table 16: Handle larger packets</h3>
 
     <p>
-      For distributed logical routers with distributed gateway port configured
-      with <code>options:gateway_mtu</code> to a valid integer value, this
-      table adds the following priority-50 logical flow for each
+      For distributed logical routers or gateway routers with gateway port
+      configured with <code>options:gateway_mtu</code> to a valid integer
+      value, this table adds the following priority-50 logical flow for each
       logical router port with the match <code>inport == <var>LRP</var>
       &amp;&amp; outport == <var>GW_PORT</var> &amp;&amp;
       REGBIT_PKT_LARGER</code>, where <var>LRP</var> is the logical
-      router port and <var>GW_PORT</var> is the distributed gateway router
-      port and applies the following action for ipv4 and ipv6 respectively:
+      router port and <var>GW_PORT</var> is the gateway router port and applies
+      the following action for ipv4 and ipv6 respectively:
     </p>
 
     <pre>
diff --git a/northd/ovn-northd.c b/northd/ovn-northd.c
index 18f6f90ce..20f8d7b73 100644
--- a/northd/ovn-northd.c
+++ b/northd/ovn-northd.c
@@ -11038,17 +11038,29 @@  build_check_pkt_len_flows_for_lrouter(
         struct ds *match, struct ds *actions,
         struct shash *meter_groups)
 {
-    if (od->nbr) {
+    if (!od->nbr) {
+        return;
+    }
 
-        /* Packets are allowed by default. */
-        ovn_lflow_add(lflows, od, S_ROUTER_IN_CHK_PKT_LEN, 0, "1",
-                      "next;");
-        ovn_lflow_add(lflows, od, S_ROUTER_IN_LARGER_PKTS, 0, "1",
-                      "next;");
+    /* Packets are allowed by default. */
+    ovn_lflow_add(lflows, od, S_ROUTER_IN_CHK_PKT_LEN, 0, "1",
+                  "next;");
+    ovn_lflow_add(lflows, od, S_ROUTER_IN_LARGER_PKTS, 0, "1",
+                  "next;");
 
-        if (od->l3dgw_port && od->l3redirect_port) {
-            build_check_pkt_len_flows_for_lrp(od->l3dgw_port, lflows,
-                                              ports, meter_groups,
+    if (od->l3dgw_port && od->l3redirect_port) {
+        /* gw router port */
+        build_check_pkt_len_flows_for_lrp(od->l3dgw_port, lflows,
+                                          ports, meter_groups, match, actions);
+    } else if (smap_get(&od->nbr->options, "chassis")) {
+        for (size_t i = 0; i < od->nbr->n_ports; i++) {
+            /* gw router */
+            struct ovn_port *rp = ovn_port_find(ports,
+                                                od->nbr->ports[i]->name);
+            if (!rp) {
+                continue;
+            }
+            build_check_pkt_len_flows_for_lrp(rp, lflows, ports, meter_groups,
                                               match, actions);
         }
     }
diff --git a/northd/ovn_northd.dl b/northd/ovn_northd.dl
index 7bfaae992..d1f7dbbed 100644
--- a/northd/ovn_northd.dl
+++ b/northd/ovn_northd.dl
@@ -7504,17 +7504,30 @@  for (&Router(._uuid = lr_uuid))
 
 /* Local router ingress table CHK_PKT_LEN: Check packet length.
  *
- * Any IPv4 packet with outport set to the distributed gateway
+ * For distributed routers with gateway ports.
+ * Any IPv4 or IPv6 packet with outport set to the distributed gateway
  * router port, check the packet length and store the result in the
  * 'REGBIT_PKT_LARGER' register bit.
  *
  * Local router ingress table LARGER_PKTS: Handle larger packets.
  *
- * Any IPv4 packet with outport set to the distributed gateway
+ * Any IPv4 or IPv6 packet with outport set to the distributed gateway
  * router port and the 'REGBIT_PKT_LARGER' register bit is set,
- * generate ICMPv4 packet with type 3 (Destination Unreachable) and
- * code 4 (Fragmentation needed).
- * */
+ * generate an ICMPv4/ICMPv6 packet with type 3/2 (Destination
+ * Unreachable/Packet Too Big) and code 4/0 (Fragmentation needed).
+ *
+ * For Gateway routers.
+ * Any IPv4 or IPv6 packet with outport set to the router port which has
+ * the option 'gateway_mtu' set, check the packet length and store
+ * the result in the 'REGBIT_PKT_LARGER' register bit.
+ *
+ * Local router ingress table LARGER_PKTS: Handle larger packets.
+ *
+ * Any IPv4 or IPv6 packet with outport set to the router port which has
+ * the option 'gateway_mtu' set and the 'REGBIT_PKT_LARGER' register bit
+ * is set, generate ICMPv4/ICMPv6 packet with type 3/2 (Destination
+ * Unreachable/Packet Too Big) and * code 4/0 (Fragmentation needed).
+ */
 Flow(.logical_datapath = lr_uuid,
      .stage            = s_ROUTER_IN_CHK_PKT_LEN(),
      .priority         = 0,
@@ -7602,6 +7615,75 @@  MeteredFlow(.logical_datapath = lr_uuid,
     rp.lrp != l3dgw_port,
     Some{var first_ipv6} = rp.networks.ipv6_addrs.nth(0).
 
+/* Gateway routers. */
+Flow(.logical_datapath = lr_uuid,
+     .stage            = s_ROUTER_IN_CHK_PKT_LEN(),
+     .priority         = 50,
+     .__match          = "outport == ${gw_mtu_rp.json_name}",
+     .actions          = "${rEGBIT_PKT_LARGER()} = check_pkt_larger(${mtu}); "
+                         "next;",
+     .external_ids     = stage_hint(gw_mtu_rp.lrp._uuid)) :-
+    r in &Router(._uuid = lr_uuid),
+    r.is_gateway,
+    gw_mtu_rp in &RouterPort(.router = r),
+    var gw_mtu = gw_mtu_rp.lrp.options.get_int_def("gateway_mtu", 0),
+    gw_mtu > 0,
+    var mtu = gw_mtu + vLAN_ETH_HEADER_LEN().
+Flow(.logical_datapath = lr_uuid,
+     .stage            = s_ROUTER_IN_LARGER_PKTS(),
+     .priority         = 50,
+     .__match          = "inport == ${rp.json_name} && outport == ${gw_mtu_rp.json_name} && "
+                         "ip4 && ${rEGBIT_PKT_LARGER()}",
+     .actions          = "icmp4_error {"
+                         "${rEGBIT_EGRESS_LOOPBACK()} = 1; "
+                         "eth.dst = ${rp.networks.ea}; "
+                         "ip4.dst = ip4.src; "
+                         "ip4.src = ${first_ipv4.addr}; "
+                         "ip.ttl = 255; "
+                         "icmp4.type = 3; /* Destination Unreachable. */ "
+                         "icmp4.code = 4; /* Frag Needed and DF was Set. */ "
+                         /* Set icmp4.frag_mtu to gw_mtu */
+                         "icmp4.frag_mtu = ${gw_mtu}; "
+                         "next(pipeline=ingress, table=0); "
+                         "};",
+     .external_ids     = stage_hint(rp.lrp._uuid)) :-
+    r in &Router(._uuid = lr_uuid),
+    r.is_gateway,
+    gw_mtu_rp in &RouterPort(.router = r),
+    var gw_mtu = gw_mtu_rp.lrp.options.get_int_def("gateway_mtu", 0),
+    gw_mtu > 0,
+    var mtu = gw_mtu + vLAN_ETH_HEADER_LEN(),
+    rp in &RouterPort(.router = r),
+    rp.lrp != gw_mtu_rp.lrp,
+    Some{var first_ipv4} = rp.networks.ipv4_addrs.nth(0).
+Flow(.logical_datapath = lr_uuid,
+     .stage            = s_ROUTER_IN_LARGER_PKTS(),
+     .priority         = 50,
+     .__match          = "inport == ${rp.json_name} && outport == ${gw_mtu_rp.json_name} && "
+                         "ip6 && ${rEGBIT_PKT_LARGER()}",
+     .actions          = "icmp6_error {"
+                         "${rEGBIT_EGRESS_LOOPBACK()} = 1; "
+                         "eth.dst = ${rp.networks.ea}; "
+                         "ip6.dst = ip6.src; "
+                         "ip6.src = ${first_ipv6.addr}; "
+                         "ip.ttl = 255; "
+                         "icmp6.type = 2; /* Packet Too Big. */ "
+                         "icmp6.code = 0; "
+                         /* Set icmp6.frag_mtu to gw_mtu */
+                         "icmp6.frag_mtu = ${gw_mtu}; "
+                         "next(pipeline=ingress, table=0); "
+                         "};",
+     .external_ids     = stage_hint(rp.lrp._uuid)) :-
+    r in &Router(._uuid = lr_uuid),
+    r.is_gateway,
+    gw_mtu_rp in &RouterPort(.router = r),
+    var gw_mtu = gw_mtu_rp.lrp.options.get_int_def("gateway_mtu", 0),
+    gw_mtu > 0,
+    var mtu = gw_mtu + vLAN_ETH_HEADER_LEN(),
+    rp in &RouterPort(.router = r),
+    rp.lrp != gw_mtu_rp.lrp,
+    Some{var first_ipv6} = rp.networks.ipv6_addrs.nth(0).
+
 /* Logical router ingress table GW_REDIRECT: Gateway redirect.
  *
  * For traffic with outport equal to the l3dgw_port
diff --git a/tests/ovn-northd.at b/tests/ovn-northd.at
index 94405349e..56d8be7cc 100644
--- a/tests/ovn-northd.at
+++ b/tests/ovn-northd.at
@@ -4815,3 +4815,124 @@  AT_CHECK([ovn-sbctl --columns=tags list logical_flow | grep lsp0 -c], [0], [dnl
 
 AT_CLEANUP
 ])
+
+OVN_FOR_EACH_NORTHD([
+AT_SETUP([ovn -- gateway mtu check pkt larger flows])
+ovn_start
+
+check ovn-sbctl chassis-add ch1 geneve 127.0.0.1
+
+check ovn-nbctl ls-add sw0
+check ovn-nbctl ls-add sw1
+
+# Create a logical router and attach both logical switches
+check ovn-nbctl lr-add lr0
+check ovn-nbctl lrp-add lr0 lr0-sw0 00:00:00:00:ff:01 10.0.0.1/24
+check ovn-nbctl lsp-add sw0 sw0-lr0
+check ovn-nbctl lsp-set-type sw0-lr0 router
+check ovn-nbctl lsp-set-addresses sw0-lr0 00:00:00:00:ff:01
+check ovn-nbctl lsp-set-options sw0-lr0 router-port=lr0-sw0
+
+check ovn-nbctl lrp-add lr0 lr0-sw1 00:00:00:00:ff:02 20.0.0.1/24
+check ovn-nbctl lsp-add sw1 sw1-lr0
+check ovn-nbctl lsp-set-type sw1-lr0 router
+check ovn-nbctl lsp-set-addresses sw1-lr0 00:00:00:00:ff:02
+check ovn-nbctl lsp-set-options sw1-lr0 router-port=lr0-sw1
+
+check ovn-nbctl ls-add public
+check ovn-nbctl lrp-add lr0 lr0-public 00:00:20:20:12:13 172.168.0.100/24
+check ovn-nbctl lsp-add public public-lr0
+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
+
+check ovn-nbctl --wait=sb lrp-set-gateway-chassis lr0-public ch1
+
+ovn-sbctl dump-flows lr0 > lr0flows
+AT_CAPTURE_FILE([sw0flows])
+
+AT_CHECK([grep -e "chk_pkt_len" -e "lr_in_larger_pkts" lr0flows | sort], [0], [dnl
+  table=15(lr_in_chk_pkt_len  ), priority=0    , match=(1), action=(next;)
+  table=16(lr_in_larger_pkts  ), priority=0    , match=(1), action=(next;)
+])
+
+check ovn-nbctl --wait=sb set logical_router_port lr0-public options:gateway_mtu=1500
+
+ovn-sbctl dump-flows lr0 > lr0flows
+AT_CAPTURE_FILE([sw0flows])
+
+AT_CHECK([grep -e "chk_pkt_len" -e "lr_in_larger_pkts" lr0flows | sort], [0], [dnl
+  table=15(lr_in_chk_pkt_len  ), priority=0    , match=(1), action=(next;)
+  table=15(lr_in_chk_pkt_len  ), priority=50   , match=(outport == "lr0-public"), action=(reg9[[1]] = check_pkt_larger(1518); next;)
+  table=16(lr_in_larger_pkts  ), priority=0    , match=(1), action=(next;)
+  table=16(lr_in_larger_pkts  ), priority=50   , match=(inport == "lr0-sw0" && outport == "lr0-public" && ip4 && reg9[[1]]), action=(icmp4_error {reg9[[0]] = 1; eth.dst = 00:00:00:00:ff:01; ip4.dst = ip4.src; ip4.src = 10.0.0.1; ip.ttl = 255; icmp4.type = 3; /* Destination Unreachable. */ icmp4.code = 4; /* Frag Needed and DF was Set. */ icmp4.frag_mtu = 1500; next(pipeline=ingress, table=0); };)
+  table=16(lr_in_larger_pkts  ), priority=50   , match=(inport == "lr0-sw0" && outport == "lr0-public" && ip6 && reg9[[1]]), action=(icmp6_error {reg9[[0]] = 1; eth.dst = 00:00:00:00:ff:01; ip6.dst = ip6.src; ip6.src = fe80::200:ff:fe00:ff01; ip.ttl = 255; icmp6.type = 2; /* Packet Too Big. */ icmp6.code = 0; icmp6.frag_mtu = 1500; next(pipeline=ingress, table=0); };)
+  table=16(lr_in_larger_pkts  ), priority=50   , match=(inport == "lr0-sw1" && outport == "lr0-public" && ip4 && reg9[[1]]), action=(icmp4_error {reg9[[0]] = 1; eth.dst = 00:00:00:00:ff:02; ip4.dst = ip4.src; ip4.src = 20.0.0.1; ip.ttl = 255; icmp4.type = 3; /* Destination Unreachable. */ icmp4.code = 4; /* Frag Needed and DF was Set. */ icmp4.frag_mtu = 1500; next(pipeline=ingress, table=0); };)
+  table=16(lr_in_larger_pkts  ), priority=50   , match=(inport == "lr0-sw1" && outport == "lr0-public" && ip6 && reg9[[1]]), action=(icmp6_error {reg9[[0]] = 1; eth.dst = 00:00:00:00:ff:02; ip6.dst = ip6.src; ip6.src = fe80::200:ff:fe00:ff02; ip.ttl = 255; icmp6.type = 2; /* Packet Too Big. */ icmp6.code = 0; icmp6.frag_mtu = 1500; next(pipeline=ingress, table=0); };)
+])
+
+# Clear the gateway-chassis for lr0-public
+check ovn-nbctl --wait=sb clear logical_router_port lr0-public gateway_chassis
+
+ovn-sbctl dump-flows lr0 > lr0flows
+AT_CAPTURE_FILE([sw0flows])
+
+AT_CHECK([grep -e "chk_pkt_len" -e "lr_in_larger_pkts" lr0flows | sort], [0], [dnl
+  table=15(lr_in_chk_pkt_len  ), priority=0    , match=(1), action=(next;)
+  table=16(lr_in_larger_pkts  ), priority=0    , match=(1), action=(next;)
+])
+
+# Make lr0 as a gateway router.
+check ovn-nbctl --wait=sb set logical_router lr0 options:chassis=ch1
+
+ovn-sbctl dump-flows lr0 > lr0flows
+AT_CAPTURE_FILE([sw0flows])
+
+AT_CHECK([grep -e "chk_pkt_len" -e "lr_in_larger_pkts" lr0flows | sort], [0], [dnl
+  table=15(lr_in_chk_pkt_len  ), priority=0    , match=(1), action=(next;)
+  table=15(lr_in_chk_pkt_len  ), priority=50   , match=(outport == "lr0-public"), action=(reg9[[1]] = check_pkt_larger(1518); next;)
+  table=16(lr_in_larger_pkts  ), priority=0    , match=(1), action=(next;)
+  table=16(lr_in_larger_pkts  ), priority=50   , match=(inport == "lr0-sw0" && outport == "lr0-public" && ip4 && reg9[[1]]), action=(icmp4_error {reg9[[0]] = 1; eth.dst = 00:00:00:00:ff:01; ip4.dst = ip4.src; ip4.src = 10.0.0.1; ip.ttl = 255; icmp4.type = 3; /* Destination Unreachable. */ icmp4.code = 4; /* Frag Needed and DF was Set. */ icmp4.frag_mtu = 1500; next(pipeline=ingress, table=0); };)
+  table=16(lr_in_larger_pkts  ), priority=50   , match=(inport == "lr0-sw0" && outport == "lr0-public" && ip6 && reg9[[1]]), action=(icmp6_error {reg9[[0]] = 1; eth.dst = 00:00:00:00:ff:01; ip6.dst = ip6.src; ip6.src = fe80::200:ff:fe00:ff01; ip.ttl = 255; icmp6.type = 2; /* Packet Too Big. */ icmp6.code = 0; icmp6.frag_mtu = 1500; next(pipeline=ingress, table=0); };)
+  table=16(lr_in_larger_pkts  ), priority=50   , match=(inport == "lr0-sw1" && outport == "lr0-public" && ip4 && reg9[[1]]), action=(icmp4_error {reg9[[0]] = 1; eth.dst = 00:00:00:00:ff:02; ip4.dst = ip4.src; ip4.src = 20.0.0.1; ip.ttl = 255; icmp4.type = 3; /* Destination Unreachable. */ icmp4.code = 4; /* Frag Needed and DF was Set. */ icmp4.frag_mtu = 1500; next(pipeline=ingress, table=0); };)
+  table=16(lr_in_larger_pkts  ), priority=50   , match=(inport == "lr0-sw1" && outport == "lr0-public" && ip6 && reg9[[1]]), action=(icmp6_error {reg9[[0]] = 1; eth.dst = 00:00:00:00:ff:02; ip6.dst = ip6.src; ip6.src = fe80::200:ff:fe00:ff02; ip.ttl = 255; icmp6.type = 2; /* Packet Too Big. */ icmp6.code = 0; icmp6.frag_mtu = 1500; next(pipeline=ingress, table=0); };)
+])
+
+# Set gateway_mtu option on lr0-sw0
+check ovn-nbctl --wait=sb set logical_router_port lr0-sw0 options:gateway_mtu=1400
+
+ovn-sbctl dump-flows lr0 > lr0flows
+AT_CAPTURE_FILE([sw0flows])
+
+AT_CHECK([grep -e "chk_pkt_len" -e "lr_in_larger_pkts" lr0flows | sort], [0], [dnl
+  table=15(lr_in_chk_pkt_len  ), priority=0    , match=(1), action=(next;)
+  table=15(lr_in_chk_pkt_len  ), priority=50   , match=(outport == "lr0-public"), action=(reg9[[1]] = check_pkt_larger(1518); next;)
+  table=15(lr_in_chk_pkt_len  ), priority=50   , match=(outport == "lr0-sw0"), action=(reg9[[1]] = check_pkt_larger(1418); next;)
+  table=16(lr_in_larger_pkts  ), priority=0    , match=(1), action=(next;)
+  table=16(lr_in_larger_pkts  ), priority=50   , match=(inport == "lr0-public" && outport == "lr0-sw0" && ip4 && reg9[[1]]), action=(icmp4_error {reg9[[0]] = 1; eth.dst = 00:00:20:20:12:13; ip4.dst = ip4.src; ip4.src = 172.168.0.100; ip.ttl = 255; icmp4.type = 3; /* Destination Unreachable. */ icmp4.code = 4; /* Frag Needed and DF was Set. */ icmp4.frag_mtu = 1400; next(pipeline=ingress, table=0); };)
+  table=16(lr_in_larger_pkts  ), priority=50   , match=(inport == "lr0-public" && outport == "lr0-sw0" && ip6 && reg9[[1]]), action=(icmp6_error {reg9[[0]] = 1; eth.dst = 00:00:20:20:12:13; ip6.dst = ip6.src; ip6.src = fe80::200:20ff:fe20:1213; ip.ttl = 255; icmp6.type = 2; /* Packet Too Big. */ icmp6.code = 0; icmp6.frag_mtu = 1400; next(pipeline=ingress, table=0); };)
+  table=16(lr_in_larger_pkts  ), priority=50   , match=(inport == "lr0-sw0" && outport == "lr0-public" && ip4 && reg9[[1]]), action=(icmp4_error {reg9[[0]] = 1; eth.dst = 00:00:00:00:ff:01; ip4.dst = ip4.src; ip4.src = 10.0.0.1; ip.ttl = 255; icmp4.type = 3; /* Destination Unreachable. */ icmp4.code = 4; /* Frag Needed and DF was Set. */ icmp4.frag_mtu = 1500; next(pipeline=ingress, table=0); };)
+  table=16(lr_in_larger_pkts  ), priority=50   , match=(inport == "lr0-sw0" && outport == "lr0-public" && ip6 && reg9[[1]]), action=(icmp6_error {reg9[[0]] = 1; eth.dst = 00:00:00:00:ff:01; ip6.dst = ip6.src; ip6.src = fe80::200:ff:fe00:ff01; ip.ttl = 255; icmp6.type = 2; /* Packet Too Big. */ icmp6.code = 0; icmp6.frag_mtu = 1500; next(pipeline=ingress, table=0); };)
+  table=16(lr_in_larger_pkts  ), priority=50   , match=(inport == "lr0-sw1" && outport == "lr0-public" && ip4 && reg9[[1]]), action=(icmp4_error {reg9[[0]] = 1; eth.dst = 00:00:00:00:ff:02; ip4.dst = ip4.src; ip4.src = 20.0.0.1; ip.ttl = 255; icmp4.type = 3; /* Destination Unreachable. */ icmp4.code = 4; /* Frag Needed and DF was Set. */ icmp4.frag_mtu = 1500; next(pipeline=ingress, table=0); };)
+  table=16(lr_in_larger_pkts  ), priority=50   , match=(inport == "lr0-sw1" && outport == "lr0-public" && ip6 && reg9[[1]]), action=(icmp6_error {reg9[[0]] = 1; eth.dst = 00:00:00:00:ff:02; ip6.dst = ip6.src; ip6.src = fe80::200:ff:fe00:ff02; ip.ttl = 255; icmp6.type = 2; /* Packet Too Big. */ icmp6.code = 0; icmp6.frag_mtu = 1500; next(pipeline=ingress, table=0); };)
+  table=16(lr_in_larger_pkts  ), priority=50   , match=(inport == "lr0-sw1" && outport == "lr0-sw0" && ip4 && reg9[[1]]), action=(icmp4_error {reg9[[0]] = 1; eth.dst = 00:00:00:00:ff:02; ip4.dst = ip4.src; ip4.src = 20.0.0.1; ip.ttl = 255; icmp4.type = 3; /* Destination Unreachable. */ icmp4.code = 4; /* Frag Needed and DF was Set. */ icmp4.frag_mtu = 1400; next(pipeline=ingress, table=0); };)
+  table=16(lr_in_larger_pkts  ), priority=50   , match=(inport == "lr0-sw1" && outport == "lr0-sw0" && ip6 && reg9[[1]]), action=(icmp6_error {reg9[[0]] = 1; eth.dst = 00:00:00:00:ff:02; ip6.dst = ip6.src; ip6.src = fe80::200:ff:fe00:ff02; ip.ttl = 255; icmp6.type = 2; /* Packet Too Big. */ icmp6.code = 0; icmp6.frag_mtu = 1400; next(pipeline=ingress, table=0); };)
+])
+
+# Clear gateway_mtu option on lr0-public
+check ovn-nbctl --wait=sb clear logical_router_port lr0-public options
+ovn-sbctl dump-flows lr0 > lr0flows
+AT_CAPTURE_FILE([sw0flows])
+
+AT_CHECK([grep -e "chk_pkt_len" -e "lr_in_larger_pkts" lr0flows | sort], [0], [dnl
+  table=15(lr_in_chk_pkt_len  ), priority=0    , match=(1), action=(next;)
+  table=15(lr_in_chk_pkt_len  ), priority=50   , match=(outport == "lr0-sw0"), action=(reg9[[1]] = check_pkt_larger(1418); next;)
+  table=16(lr_in_larger_pkts  ), priority=0    , match=(1), action=(next;)
+  table=16(lr_in_larger_pkts  ), priority=50   , match=(inport == "lr0-public" && outport == "lr0-sw0" && ip4 && reg9[[1]]), action=(icmp4_error {reg9[[0]] = 1; eth.dst = 00:00:20:20:12:13; ip4.dst = ip4.src; ip4.src = 172.168.0.100; ip.ttl = 255; icmp4.type = 3; /* Destination Unreachable. */ icmp4.code = 4; /* Frag Needed and DF was Set. */ icmp4.frag_mtu = 1400; next(pipeline=ingress, table=0); };)
+  table=16(lr_in_larger_pkts  ), priority=50   , match=(inport == "lr0-public" && outport == "lr0-sw0" && ip6 && reg9[[1]]), action=(icmp6_error {reg9[[0]] = 1; eth.dst = 00:00:20:20:12:13; ip6.dst = ip6.src; ip6.src = fe80::200:20ff:fe20:1213; ip.ttl = 255; icmp6.type = 2; /* Packet Too Big. */ icmp6.code = 0; icmp6.frag_mtu = 1400; next(pipeline=ingress, table=0); };)
+  table=16(lr_in_larger_pkts  ), priority=50   , match=(inport == "lr0-sw1" && outport == "lr0-sw0" && ip4 && reg9[[1]]), action=(icmp4_error {reg9[[0]] = 1; eth.dst = 00:00:00:00:ff:02; ip4.dst = ip4.src; ip4.src = 20.0.0.1; ip.ttl = 255; icmp4.type = 3; /* Destination Unreachable. */ icmp4.code = 4; /* Frag Needed and DF was Set. */ icmp4.frag_mtu = 1400; next(pipeline=ingress, table=0); };)
+  table=16(lr_in_larger_pkts  ), priority=50   , match=(inport == "lr0-sw1" && outport == "lr0-sw0" && ip6 && reg9[[1]]), action=(icmp6_error {reg9[[0]] = 1; eth.dst = 00:00:00:00:ff:02; ip6.dst = ip6.src; ip6.src = fe80::200:ff:fe00:ff02; ip.ttl = 255; icmp6.type = 2; /* Packet Too Big. */ icmp6.code = 0; icmp6.frag_mtu = 1400; next(pipeline=ingress, table=0); };)
+])
+
+AT_CLEANUP
+])
diff --git a/tests/ovn.at b/tests/ovn.at
index 13d860f10..6af62aab0 100644
--- a/tests/ovn.at
+++ b/tests/ovn.at
@@ -16733,6 +16733,53 @@  for mtu in 100 500 118; do
     test_ip6_packet_larger $mtu
 done
 
+ovn-nbctl lsp-del sw0-lr0
+
+ovn-nbctl lr-del lr0
+ovn-nbctl create Logical_Router name=lr1 options:chassis="hv1"
+ovn-nbctl lrp-add lr1 lr1-sw0 00:00:00:00:ff:01 10.0.0.1/24 1000::1/64
+ovn-nbctl lsp-add sw0 sw0-lr1
+ovn-nbctl lsp-set-type sw0-lr1 router
+ovn-nbctl lsp-set-addresses sw0-lr1 router
+ovn-nbctl lsp-set-options sw0-lr1 router-port=lr1-sw0
+
+ovn-nbctl lrp-add lr1 lr1-public 00:00:20:20:12:13 172.168.0.100/24 2000::1/64
+ovn-nbctl lsp-del public-lr0
+ovn-nbctl lsp-add public public-lr1
+ovn-nbctl lsp-set-type public-lr1 router
+ovn-nbctl lsp-set-addresses public-lr1 router
+ovn-nbctl lsp-set-options public-lr1 router-port=lr1-public
+
+ovn-nbctl lr-nat-add lr1 snat 172.168.0.100 10.0.0.0/24
+ovn-nbctl lr-nat-add lr1 snat 2000::1 1000::/64
+
+dp_uuid=$(ovn-sbctl find datapath_binding | grep sw0 -B2 | grep _uuid | \
+awk '{print $3}')
+ovn-sbctl create MAC_Binding ip=172.168.0.3 datapath=$dp_uuid \
+logical_port=lr1-public mac="00\:00\:00\:12\:af\:11"
+
+# Try different gateway mtus and send a 142-byte packet (corresponding
+# to a 124-byte MTU).  If the MTU is less than 124, ovn-controller
+# should send icmp host not reachable with pmtu set to $mtu.
+for mtu in 100 500 118; do
+    AS_BOX([testing gw mtu $mtu])
+    check ovn-nbctl --wait=hv set logical_router_port lr1-public options:gateway_mtu=$mtu
+    ovn-sbctl dump-flows > sbflows-gw-$mtu
+    AT_CAPTURE_FILE([sbflows-gw-$mtu])
+
+    OVS_WAIT_FOR_OUTPUT([
+        as hv1 ovs-ofctl dump-flows br-int > br-int-gw-flows-$mtu
+        AT_CAPTURE_FILE([br-int-gw-flows-$mtu])
+        grep "check_pkt_larger($(expr $mtu + 18))" br-int-gw-flows-$mtu | wc -l], [0], [1
+])
+
+    AS_BOX([testing gw mtu $mtu - IPv4])
+    test_ip_packet_larger $mtu
+
+    AS_BOX([testing gw mtu $mtu - IPv6])
+    test_ip6_packet_larger $mtu
+done
+
 OVN_CLEANUP([hv1])
 AT_CLEANUP
 ])