[ovs-dev] [PATCH ovn 7/7] ovn-northd.c: Support optionally disabling neighbor learning from ARP request/NS.

Numan Siddique numans at ovn.org
Wed Jul 29 17:41:56 UTC 2020


On Thu, Jul 23, 2020 at 10:57 AM Han Zhou <hzhou at ovn.org> wrote:

> Support a new logical router option "always_learn_from_arp_request" that
> controls
> behavior when handling ARP requests or IPv4 ND-NS packets.
>
> "true" - Always learn the MAC/IP binding and add a new MAC_Binding entry
> (default behavior)
>
> "false" - If there is a MAC_binding for that IP and the MAC is different,
> or,
> if TPA of ARP request belongs to any router port on this router, then
> update/add that MAC/IP binding. Otherwise, don't update/add entries.
>
> Reported-by: Girish Moodalbail <gmoodalbail at nvidia.com>
> Reported-at:
> https://mail.openvswitch.org/pipermail/ovs-discuss/2020-May/049995.html
> Signed-off-by: Han Zhou <hzhou at ovn.org>
>

Hi Han,

I just gave a quick look. I'll review properly tomorrow.

I just have a few small comments now. I think it's good to add a few tests
in ovn-northd.at
to make sure that ovn-northd programs the flows as expected.


Thanks
Numan

---
>  northd/ovn-northd.8.xml | 109
> ++++++++++++++++++++++++++++++++++++++++--------
>  northd/ovn-northd.c     |  96 +++++++++++++++++++++++++++++++++++-------
>  ovn-nb.xml              |  27 ++++++++++++
>  tests/ovn.at            |  18 ++++++++
>  4 files changed, 217 insertions(+), 33 deletions(-)
>
> diff --git a/northd/ovn-northd.8.xml b/northd/ovn-northd.8.xml
> index 9f2c70f..30936ab 100644
> --- a/northd/ovn-northd.8.xml
> +++ b/northd/ovn-northd.8.xml
> @@ -1537,58 +1537,126 @@ output;
>          <p>
>            For each router port <var>P</var> that owns IP address
> <var>A</var>,
>            which belongs to subnet <var>S</var> with prefix length
> <var>L</var>,
> -          a priority-100 flow is added which matches
> -          <code>inport == <var>P</var> &&
> -          arp.spa == <var>S</var>/<var>L</var> && arp.op ==
> 1</code>
> -          (ARP request) with the
> -          following actions:
> +          if the option <code>always_learn_from_arp_request</code> is
> +          <code>true</code> for this router, a priority-100 flow is added
> which
> +          matches <code>inport == <var>P</var> && arp.spa ==
> +          <var>S</var>/<var>L</var> && arp.op == 1</code> (ARP
> request)
> +          with the following actions:
> +        </p>
> +
> +        <pre>
> +reg9[2] = lookup_arp(inport, arp.spa, arp.sha);
> +next;
> +        </pre>
> +
> +        <p>
> +          If the option <code>always_learn_from_arp_request</code> is
> +          <code>false</code>, the following two flows are added.
> +        </p>
> +
> +        <p>
> +          A priority-110 flow is added which matches <code>inport ==
> +          <var>P</var> && arp.spa == <var>S</var>/<var>L</var>
> +          && arp.tpa == <var>A</var> && arp.op == 1</code>
> +          (ARP request) with the following actions:
>          </p>
>
>          <pre>
>  reg9[2] = lookup_arp(inport, arp.spa, arp.sha);
> +reg9[3] = 1;
> +next;
> +        </pre>
> +
> +        <p>
> +          A priority-100 flow is added which matches <code>inport ==
> +          <var>P</var> && arp.spa == <var>S</var>/<var>L</var>
> +          && arp.op == 1</code> (ARP request) with the following
> +          actions:
> +        </p>
> +
> +        <pre>
> +reg9[2] = lookup_arp(inport, arp.spa, arp.sha);
> +reg9[3] = lookup_arp_ip(inport, arp.spa);
>  next;
>          </pre>
>
>          <p>
>            If the logical router port <var>P</var> is a distributed gateway
>            router port, additional match
> -          <code>is_chassis_resident(cr-<var>P</var>)</code> is added so
> that
> -          the resident gateway chassis handles the neighbor lookup.
> +          <code>is_chassis_resident(cr-<var>P</var>)</code> is added for
> all
> +          these flows.
>          </p>
>        </li>
>
>        <li>
>          <p>
>            A priority-100 flow which matches on ARP reply packets and
> applies
> -          the actions:
> +          the actions if the option
> <code>always_learn_from_arp_request</code>
> +          is <code>true</code>:
>          </p>
>
>          <pre>
>  reg9[2] = lookup_arp(inport, arp.spa, arp.sha);
>  next;
>          </pre>
> +
> +        <p>
> +          If the option <code>always_learn_from_arp_request</code>
> +          is <code>false</code>, the above actions will be:
> +        </p>
> +
> +        <pre>
> +reg9[2] = lookup_arp(inport, arp.spa, arp.sha);
> +reg9[3] = 1;
> +next;
> +        </pre>
> +
>        </li>
>
>        <li>
>          <p>
>            A priority-100 flow which matches on IPv6 Neighbor Discovery
> -          advertisement packet and applies the actions:
> +          advertisement packet and applies the actions if the option
> +          <code>always_learn_from_arp_request</code> is <code>true</code>:
>          </p>
>
>          <pre>
>  reg9[2] = lookup_nd(inport, nd.target, nd.tll);
>  next;
>          </pre>
> +
> +        <p>
> +          If the option <code>always_learn_from_arp_request</code>
> +          is <code>false</code>, the above actions will be:
> +        </p>
> +
> +        <pre>
> +reg9[2] = lookup_nd(inport, nd.target, nd.tll);
> +reg9[3] = 1;
> +next;
> +        </pre>
>        </li>
>
>        <li>
>          <p>
>            A priority-100 flow which matches on IPv6 Neighbor Discovery
> -          solicitation packet and applies the actions:
> +          solicitation packet and applies the actions if the option
> +          <code>always_learn_from_arp_request</code> is <code>true</code>:
> +        </p>
> +
> +        <pre>
> +reg9[2] = lookup_nd(inport, ip6.src, nd.sll);
> +next;
> +        </pre>
> +
> +        <p>
> +          If the option <code>always_learn_from_arp_request</code>
> +          is <code>false</code>, the above actions will be:
>          </p>
>
>          <pre>
>  reg9[2] = lookup_nd(inport, ip6.src, nd.sll);
> +reg9[3] = lookup_nd_ip(inport, ip6.src);
>  next;
>          </pre>
>        </li>
> @@ -1604,21 +1672,28 @@ next;
>
>      <p>
>        This table adds flows to learn the mac bindings from the ARP and
> -      IPv6 Neighbor Solicitation/Advertisement packets if ARP/ND lookup
> -      failed in the previous table.
> +      IPv6 Neighbor Solicitation/Advertisement packets if it is needed
> +      according to the lookup results from the previous stage.
>      </p>
>
>      <p>
>        reg9[2] will be <code>1</code> if the
> <code>lookup_arp/lookup_nd</code>
> -      in the previous table was successful, or if there was no need to do
> the
> -      lookup.
> +      in the previous table was successful or skipped, meaning no need
> +      to learn mac binding from the packet.
> +    </p>
> +
> +    <p>
> +      reg9[3] will be <code>1</code> if the
> +      <code>lookup_arp_ip/lookup_nd_ip</code> in the previous table was
> +      successful or skipped, meaning it is ok to learn mac binding from
> +      the packet (if reg9[2] is 0).
>      </p>
>
>      <ul>
>        <li>
> -        A priority-100 flow with the match
> -        <code>reg9[2] == 1</code> and advances the packet
> -        to the next table as there is no need to learn the neighbor.
> +        A priority-100 flow with the match <code>reg9[2] == 1 || reg9[3]
> ==
> +        0</code> and advances the packet to the next table as there is no
> need
> +        to learn the neighbor.
>        </li>
>
>        <li>
> diff --git a/northd/ovn-northd.c b/northd/ovn-northd.c
> index 425f522..b5e7c08 100644
> --- a/northd/ovn-northd.c
> +++ b/northd/ovn-northd.c
> @@ -221,6 +221,7 @@ enum ovn_stage {
>  /* Register to store the result of check_pkt_larger action. */
>  #define REGBIT_PKT_LARGER        "reg9[1]"
>  #define REGBIT_LOOKUP_NEIGHBOR_RESULT "reg9[2]"
> +#define REGBIT_LOOKUP_NEIGHBOR_IP_RESULT "reg9[3]"
>
>  /* Register to store the eth address associated to a router port for
> packets
>   * received in S_ROUTER_IN_ADMISSION.
> @@ -8242,36 +8243,62 @@ build_lrouter_flows(struct hmap *datapaths, struct
> hmap *ports,
>           * For ARP packets, table LOOKUP_NEIGHBOR does a lookup for the
>           * (arp.spa, arp.sha) in the mac binding table using the
> 'lookup_arp'
>           * action and stores the result in REGBIT_LOOKUP_NEIGHBOR_RESULT
> bit.
> +         * If "always_learn_from_arp_request" is set to false, it will
> also
> +         * lookup for the (arp.spa) in the mac binding table using the
> +         * "lookup_arp_ip" action for ARP request packets, and stores the
> +         * result in REGBIT_LOOKUP_NEIGHBOR_IP_RESULT bit; or set that bit
> +         * to "1" directly for ARP response packets.
>           *
>           * For IPv6 ND NA packets, table LOOKUP_NEIGHBOR does a lookup
>           * for the (nd.target, nd.tll) in the mac binding table using the
>           * 'lookup_nd' action and stores the result in
> -         * REGBIT_LOOKUP_NEIGHBOR_RESULT bit.
> +         * REGBIT_LOOKUP_NEIGHBOR_RESULT bit. If
> +         * "always_learn_from_arp_request" is set to false,
> +         * REGBIT_LOOKUP_NEIGHBOR_IP_RESULT bit is set.
>           *
>           * For IPv6 ND NS packets, table LOOKUP_NEIGHBOR does a lookup
>           * for the (ip6.src, nd.sll) in the mac binding table using the
>           * 'lookup_nd' action and stores the result in
> -         * REGBIT_LOOKUP_NEIGHBOR_RESULT bit.
> +         * REGBIT_LOOKUP_NEIGHBOR_RESULT bit. If
> +         * "always_learn_from_arp_request" is set to false, it will also
> lookup
> +         * for the (ip6.src) in the mac binding table using the
> "lookup_nd_ip"
> +         * action and stores the result in
> REGBIT_LOOKUP_NEIGHBOR_IP_RESULT
> +         * bit.
>           *
>           * Table LEARN_NEIGHBOR learns the mac-binding using the action
> -         * - 'put_arp/put_nd' only if REGBIT_LOOKUP_NEIGHBOR_RESULT bit
> -         * is not set.
> +         * - 'put_arp/put_nd'. Learning mac-binding is skipped if
> +         *   REGBIT_LOOKUP_NEIGHBOR_RESULT bit is set or
> +         *   REGBIT_LOOKUP_NEIGHBOR_IP_RESULT is not set.
>           *
>           * */
>
>          /* Flows for LOOKUP_NEIGHBOR. */
> +        bool learn_from_arp_request = smap_get_bool(&od->nbr->options,
> +            "always_learn_from_arp_request", true);
> +        ds_clear(&actions);
> +        ds_put_format(&actions, REGBIT_LOOKUP_NEIGHBOR_RESULT
> +                      " = lookup_arp(inport, arp.spa, arp.sha); %snext;",
> +                      learn_from_arp_request ? "" :
> +                      REGBIT_LOOKUP_NEIGHBOR_IP_RESULT" = 1; ");
>          ovn_lflow_add(lflows, od, S_ROUTER_IN_LOOKUP_NEIGHBOR, 100,
> -                      "arp.op == 2",
> -                      REGBIT_LOOKUP_NEIGHBOR_RESULT" = "
> -                      "lookup_arp(inport, arp.spa, arp.sha); next;");
> +                      "arp.op == 2", ds_cstr(&actions));
>
> +        ds_clear(&actions);
> +        ds_put_format(&actions, REGBIT_LOOKUP_NEIGHBOR_RESULT
> +                      " = lookup_nd(inport, nd.target, nd.tll); %snext;",
> +                      learn_from_arp_request ? "" :
> +                      REGBIT_LOOKUP_NEIGHBOR_IP_RESULT" = 1; ");
>          ovn_lflow_add(lflows, od, S_ROUTER_IN_LOOKUP_NEIGHBOR, 100,
> "nd_na",
> -                      REGBIT_LOOKUP_NEIGHBOR_RESULT" = "
> -                      "lookup_nd(inport, nd.target, nd.tll); next;");
> +                      ds_cstr(&actions));
>
> +        ds_clear(&actions);
> +        ds_put_format(&actions, REGBIT_LOOKUP_NEIGHBOR_RESULT
> +                      " = lookup_nd(inport, ip6.src, nd.sll); %snext;",
> +                      learn_from_arp_request ? "" :
> +                      REGBIT_LOOKUP_NEIGHBOR_IP_RESULT
> +                      " = lookup_nd_ip(inport, ip6.src); ");
>          ovn_lflow_add(lflows, od, S_ROUTER_IN_LOOKUP_NEIGHBOR, 100,
> "nd_ns",
> -                      REGBIT_LOOKUP_NEIGHBOR_RESULT" = "
> -                      "lookup_nd(inport, ip6.src, nd.sll); next;");
> +                      ds_cstr(&actions));
>
>          /* For other packet types, we can skip neighbor learning.
>           * So set REGBIT_LOOKUP_NEIGHBOR_RESULT to 1. */
> @@ -8280,8 +8307,12 @@ build_lrouter_flows(struct hmap *datapaths, struct
> hmap *ports,
>
>          /* Flows for LEARN_NEIGHBOR. */
>          /* Skip Neighbor learning if not required. */
> +        ds_clear(&match);
> +        ds_put_format(&match, REGBIT_LOOKUP_NEIGHBOR_RESULT" == 1%s",
> +                      learn_from_arp_request ? "" :
> +                      " || "REGBIT_LOOKUP_NEIGHBOR_IP_RESULT" == 0");
>          ovn_lflow_add(lflows, od, S_ROUTER_IN_LEARN_NEIGHBOR, 100,
> -                      REGBIT_LOOKUP_NEIGHBOR_RESULT" == 1", "next;");
> +                      ds_cstr(&match), "next;");
>
>          ovn_lflow_add(lflows, od, S_ROUTER_IN_LEARN_NEIGHBOR, 90,
>                        "arp", "put_arp(inport, arp.spa, arp.sha); next;");
> @@ -8298,8 +8329,37 @@ build_lrouter_flows(struct hmap *datapaths, struct
> hmap *ports,
>              continue;
>          }
>
> +        bool learn_from_arp_request = smap_get_bool(&op->od->nbr->options,
> +            "always_learn_from_arp_request", true);
> +
>          /* Check if we need to learn mac-binding from ARP requests. */
>          for (int i = 0; i < op->lrp_networks.n_ipv4_addrs; i++) {
> +            if (!learn_from_arp_request) {
> +                /* ARP request to this address should always get learned,
> +                 * so add a priority-110 flow to set
> +                 * REGBIT_LOOKUP_NEIGHBOR_IP_RESULT to 1. */
> +                ds_clear(&match);
> +                ds_put_format(&match,
> +                              "inport == %s && arp.spa == %s/%u && "
> +                              "arp.tpa == %s && arp.op == 1",
> +                              op->json_key,
> +                              op->lrp_networks.ipv4_addrs[i].network_s,
> +                              op->lrp_networks.ipv4_addrs[i].plen,
> +                              op->lrp_networks.ipv4_addrs[i].addr_s);
> +                if (op->od->l3dgw_port && op == op->od->l3dgw_port
> +                    && op->od->l3redirect_port) {
> +                    ds_put_format(&match, " && is_chassis_resident(%s)",
> +                                  op->od->l3redirect_port->json_key);
> +                }
> +                const char *actions_s = REGBIT_LOOKUP_NEIGHBOR_RESULT
> +                                  " = lookup_arp(inport, arp.spa,
> arp.sha); "
> +                                  REGBIT_LOOKUP_NEIGHBOR_IP_RESULT" = 1;"
> +                                  " next;";
> +                ovn_lflow_add_with_hint(lflows, op->od,
> +                                        S_ROUTER_IN_LOOKUP_NEIGHBOR, 110,
> +                                        ds_cstr(&match), actions_s,
> +                                        &op->nbrp->header_);
> +            }
>              ds_clear(&match);
>              ds_put_format(&match,
>                            "inport == %s && arp.spa == %s/%u && arp.op ==
> 1",
> @@ -8311,12 +8371,16 @@ build_lrouter_flows(struct hmap *datapaths, struct
> hmap *ports,
>                  ds_put_format(&match, " && is_chassis_resident(%s)",
>                                op->od->l3redirect_port->json_key);
>              }
> +            ds_clear(&actions);
> +            ds_put_format(&actions, REGBIT_LOOKUP_NEIGHBOR_RESULT
> +                          " = lookup_arp(inport, arp.spa, arp.sha);
> %snext;",
> +                          learn_from_arp_request ? "" :
> +                          REGBIT_LOOKUP_NEIGHBOR_IP_RESULT
> +                          " = lookup_arp_ip(inport, arp.spa); ");
>              ovn_lflow_add_with_hint(lflows, op->od,
>                                      S_ROUTER_IN_LOOKUP_NEIGHBOR, 100,
> -                                    ds_cstr(&match),
> -                                    REGBIT_LOOKUP_NEIGHBOR_RESULT" = "
> -                                    "lookup_arp(inport, arp.spa,
> arp.sha); "
> -                                    "next;", &op->nbrp->header_);
> +                                    ds_cstr(&match), ds_cstr(&actions),
> +                                    &op->nbrp->header_);
>          }
>      }
>
> diff --git a/ovn-nb.xml b/ovn-nb.xml
> index e8450aa..415d30a 100644
> --- a/ovn-nb.xml
> +++ b/ovn-nb.xml
> @@ -1859,6 +1859,33 @@
>            send traffic between each other.
>          </p>
>        </column>
> +      <column name="options" key="always_learn_from_arp_request"
> type='{"type": "boolean"}'>
> +        <p>
> +          This option controls the behavior when handling IPv4 ARP
> requests or
> +          IPv6 ND-NS packets - whether a dynamic neighbor (MAC binding)
> entry
> +          is added/updated.
> +        </p>
> +
> +        <p>
> +          <code>true</code> - Always learn the MAC-IP binding, and
> add/update
> +          the MAC binding entry.
> +        </p>
> +
> +        <p>
> +          <code>false</code> - If there is a MAC binding for that IP and
> the
> +          MAC is different, or, if TPA of ARP request belongs to any
> router
> +          port on this router, then update/add that MAC-IP binding.
> Otherwise,
> +          don't update/add entries.
> +        </p>
> +
> +        <p>
> +          It is <code>true</code> by default.  It is recommended to set to
> +          <code>false</code> when a large number of logical routers are
> +          connected to the same logical switch but most of them never
> need to
> +          send traffic between each other, to reduce the size of the MAC
> +          binding table.
> +        </p>
> +      </column>
>      </group>
>
>      <group title="Common Columns">
> diff --git a/tests/ovn.at b/tests/ovn.at
> index 67fb754..fc811b4 100644
> --- a/tests/ovn.at
> +++ b/tests/ovn.at
> @@ -4031,6 +4031,18 @@ ip_to_hex() {
>  sha=f00000000011
>  spa=`ip_to_hex 192 168 1 100`
>  tpa=$spa
> +
> +# When always_learn_from_arp_request=false, the new mac-binding will not
> be learned
> +# through GARP request.
> +ovn-nbctl --wait=hv set logical_router lr0
> options:always_learn_from_arp_request=false
> +
> +test_arp 11 $sha $spa $tpa
> +sleep 1
>

Instead of sleep, I think it's good to run "ovn-nbctl --wait-hv sync"



> +AT_CHECK([ovn-sbctl find mac_binding ip="192.168.1.100"], [0], [])
> +
> +# When always_learn_from_arp_request=true, the new mac-binding will be
> learned.
> +ovn-nbctl --wait=hv set logical_router lr0
> options:always_learn_from_arp_request=true
> +
>  test_arp 11 $sha $spa $tpa
>  OVS_WAIT_UNTIL([test `ovn-sbctl find mac_binding ip="192.168.1.100" | wc
> -l` -gt 0])
>  ovn-nbctl --wait=hv sync
> @@ -4045,6 +4057,12 @@ test_ip 21 $smac $dmac $sip $dip 11
>
>  # lp12 send GARP request to announce ownership of 192.168.1.100.
>
> +# Even when always_learn_from_arp_request=false, the existing mac-binding
> should be
> +# updated through GARP request.
> +ovn-nbctl --wait=hv set logical_router lr0
> options:always_learn_from_arp_request=false
> +ovn-sbctl lflow-list
> +as hv2 ovs-ofctl dump-flows br-int
> +
>  sha=f00000000012
>  test_arp 12 $sha $spa $tpa
>  OVS_WAIT_UNTIL([ovn-sbctl find mac_binding ip="192.168.1.100" | grep
> f0:00:00:00:00:12])
> --
> 2.1.0
>
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