[ovs-dev] [PATCH ovn v2 1/2] northd: Swap src and dst eth addresses in router egress loop.

Numan Siddique numans at ovn.org
Mon Mar 15 18:14:35 UTC 2021


On Thu, Mar 11, 2021 at 1:25 AM Mark Michelson <mmichels at redhat.com> wrote:
>
> When a hairpin scenario is detected (i.e. egressing on gateway router
> port to a NAT external address), we loop back to the ingress router
> pipeline and swap the inport and outport. This is intended to allow for
> the traffic to get DNATted. In practice, though, the ethernet
> destination has not been updated to be the distributed gateway port's
> address, and so the packet is immediately dropped.
>
> This fixes the issue by swapping source and dest eth addressses when
> doing the hairpin redirection. This way, the packet appears to be
> arriving on the gateway port, and it gets handled as expected.
>
> Reported at: https://bugzilla.redhat.com/show_bug.cgi?id=1929901
>
> Signed-off-by: Mark Michelson <mmichels at redhat.com>
> ---
>  northd/ovn-northd.c  |   1 +
>  northd/ovn_northd.dl |   1 +
>  tests/system-ovn.at  | 111 +++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 113 insertions(+)
>
> diff --git a/northd/ovn-northd.c b/northd/ovn-northd.c
> index 7b95a5c7f..cab17f07e 100644
> --- a/northd/ovn-northd.c
> +++ b/northd/ovn-northd.c
> @@ -11642,6 +11642,7 @@ build_lrouter_nat_defrag_and_lb(struct ovn_datapath *od,
>              ds_put_format(actions,
>                            "clone { ct_clear; "
>                            "inport = outport; outport = \"\"; "
> +                          "eth.dst <-> eth.src; "
>                            "flags = 0; flags.loopback = 1; ");
>              for (int j = 0; j < MFF_N_LOG_REGS; j++) {
>                  ds_put_format(actions, "reg%d = 0; ", j);
> diff --git a/northd/ovn_northd.dl b/northd/ovn_northd.dl
> index 8d0d55682..227f38157 100644
> --- a/northd/ovn_northd.dl
> +++ b/northd/ovn_northd.dl
> @@ -5923,6 +5923,7 @@ for (r in &Router(.lr = lr,
>              var actions =
>                  "clone { ct_clear; "
>                  "inport = outport; outport = \"\"; "
> +                "eth.dst <-> eth.src ;"

In v1 of this patch, Ben pointed out a typo.

With that typo fixed - Acked-by: Numan Siddique <numans at ovn.org>

Thanks
Numan



>                  "flags = 0; flags.loopback = 1; " ++
>                  regs.join("") ++
>                  "${rEGBIT_EGRESS_LOOPBACK()} = 1; "
> diff --git a/tests/system-ovn.at b/tests/system-ovn.at
> index 4885303d1..36b469c30 100644
> --- a/tests/system-ovn.at
> +++ b/tests/system-ovn.at
> @@ -5903,3 +5903,114 @@ OVS_TRAFFIC_VSWITCHD_STOP(["/.*error receiving.*/d
>  /.*terminating with signal 15.*/d"])
>  AT_CLEANUP
>  ])
> +
> +OVN_FOR_EACH_NORTHD([
> +AT_SETUP(ovn -- DNAT LR hairpin IPv4)
> +AT_KEYWORDS(hairpin)
> +
> +ovn_start
> +
> +OVS_TRAFFIC_VSWITCHD_START()
> +ADD_BR([br-int])
> +
> +# Set external-ids in br-int needed for ovn-controller
> +ovs-vsctl \
> +        -- set Open_vSwitch . external-ids:system-id=hv1 \
> +        -- set Open_vSwitch . external-ids:ovn-remote=unix:$ovs_base/ovn-sb/ovn-sb.sock \
> +        -- set Open_vSwitch . external-ids:ovn-encap-type=geneve \
> +        -- set Open_vSwitch . external-ids:ovn-encap-ip=169.0.0.1 \
> +        -- set bridge br-int fail-mode=secure other-config:disable-in-band=true
> +
> +start_daemon ovn-controller
> +
> +# Logical network:
> +# Two VMs
> +#   * VM1 with IP address 192.168.100.5
> +#   * VM2 with IP address 192.168.100.6
> +# The VMs connect to logical switch ls1.
> +#
> +# An external router with IP address 172.18.1.2. We simulate this with a network namespace.
> +# There will be no traffic going here in this test.
> +# The external router connects to logical switch ls-pub
> +#
> +# One logical router (lr1) connects to ls1 and ls-pub. The router port connected to ls-pub is
> +# a gateway port.
> +#   * The subnet connected to ls1 is 192.168.100.0/24. The Router IP address is 192.168.100.1
> +#   * The subnet connected to ls-pub is 172.18.1.0/24. The Router IP address is 172.168.1.1
> +# lr1 has the following attributes:
> +#   * It has a "default" static route that sends traffic out the gateway router port.
> +#   * It has a DNAT rule that translates 172.18.2.10 to 192.168.100.6 (VM2)
> +#
> +# In this test, we want to ensure that a ping from VM1 to IP address 172.18.2.10 reaches VM2.
> +
> +ovn-nbctl ls-add ls1
> +ovn-nbctl lsp-add ls1 vm1 -- lsp-set-addresses vm1 "00:00:00:00:00:05 192.168.100.5"
> +ovn-nbctl lsp-add ls1 vm2 -- lsp-set-addresses vm2 "00:00:00:00:00:06 192.168.100.6"
> +
> +ovn-nbctl ls-add ls-pub
> +ovn-nbctl lsp-add ls-pub ext-router -- lsp-set-addresses ext-router "00:00:00:00:01:02 172.18.1.2"
> +
> +ovn-nbctl lr-add lr1
> +ovn-nbctl lrp-add lr1 lr1-ls1 00:00:00:00:00:01 192.168.100.1/24
> +ovn-nbctl lsp-add ls1 ls1-lr1                      \
> +    -- lsp-set-type ls1-lr1 router                 \
> +    -- lsp-set-addresses ls1-lr1 00:00:00:00:00:01 \
> +    -- lsp-set-options ls1-lr1 router-port=lr1-ls1
> +
> +ovn-nbctl lrp-add lr1 lr1-ls-pub 00:00:00:00:01:01 172.18.1.1/24
> +ovn-nbctl lrp-set-gateway-chassis lr1-ls-pub hv1
> +ovn-nbctl lsp-add ls-pub ls-pub-lr1                      \
> +    -- lsp-set-type ls-pub-lr1 router                    \
> +    -- lsp-set-addresses ls-pub-lr1 00:00:00:00:01:01    \
> +    -- lsp-set-options ls-pub-lr1 router-port=lr1-ls-pub
> +
> +ovn-nbctl lr-nat-add lr1 snat 172.18.1.1 192.168.100.0/24
> +ovn-nbctl lr-nat-add lr1 dnat_and_snat 172.18.2.10 192.168.100.6
> +ovn-nbctl lr-route-add lr1 0.0.0.0/0 172.18.1.2
> +
> +#ls1_uuid=$(fetch_column Port_Binding datapath logical_port=vm1)
> +#ovn-sbctl create MAC_Binding ip=172.18.2.10 datapath=$ls1_uuid logical_port=vm2 mac="00:00:00:00:00:06"
> +
> +OVN_POPULATE_ARP
> +ovn-nbctl --wait=hv sync
> +
> +ADD_NAMESPACES(vm1)
> +ADD_VETH(vm1, vm1, br-int, "192.168.100.5/24", "00:00:00:00:00:05", \
> +         "192.168.100.1")
> +
> +ADD_NAMESPACES(vm2)
> +ADD_VETH(vm2, vm2, br-int, "192.168.100.6/24", "00:00:00:00:00:06", \
> +         "192.168.100.1")
> +
> +ADD_NAMESPACES(ext-router)
> +ADD_VETH(ext-router, ext-router, br-int, "172.18.1.2/24", "00:00:00:00:01:02", \
> +         "172.18.1.1")
> +
> +# Let's take a quick look at the logical flows
> +ovn-sbctl lflow-list
> +
> +# Let's check what ovn-trace says...
> +ovn-trace ls1 'inport == "vm1" && eth.src == 00:00:00:00:00:05 && ip4.src == 192.168.100.5 && eth.dst == 00:00:00:00:00:01 && ip4.dst == 172.18.2.10 && ip.ttl == 32'
> +
> +# A ping from vm1 should hairpin in lr1 and successfully DNAT to vm2
> +NS_CHECK_EXEC([vm1], [ping -q -c 3 -i 0.3 -w 2 172.18.2.10 | FORMAT_PING], \
> +[0], [dnl
> +3 packets transmitted, 3 received, 0% packet loss, time 0ms
> +])
> +kill $(pidof ovn-controller)
> +
> +as ovn-sb
> +OVS_APP_EXIT_AND_WAIT([ovsdb-server])
> +
> +as ovn-nb
> +OVS_APP_EXIT_AND_WAIT([ovsdb-server])
> +
> +as northd
> +OVS_APP_EXIT_AND_WAIT([NORTHD_TYPE])
> +
> +as
> +OVS_TRAFFIC_VSWITCHD_STOP(["/.*error receiving.*/d
> +/.*terminating with signal 15.*/d"])
> +
> +AT_CLEANUP
> +])
> --
> 2.29.2
>
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