Hi Dumitru,
On Fri, 2024-12-06 at 10:01 +0100, Dumitru Ceara wrote:
> On 8/23/24 2:58 PM, Martin Kalcok via discuss wrote:
> > Hello OVN enthusiasts o/
> > I noticed that when periodic IPv6 Router Advertisements are enabled
> > on LRP [0], they wont get forwarded to the external networks. I’m
> > just wondering if it’s intentional, or a bug. I have following
> > simple setup:
>
> Hi Martin,
>
> I think this bug report fell through the cracks but MJ brought it up
> again during yesterday's IRC meeting. Thanks for that, MJ!
>
> >
> > alice | | ovn-host
> > | |
> > eth1 -------- eth1 -- SW-EXT --- R1
> > | |
> >
> > * alice is external host connected via physical network
> > * ovn-host runs OVN+OVS services
> > * SW-EXT is LS
> > * R1 is LR with interface plugged to SW-EXT
> >
> > Below are (what I think) relevant details:
> >
> > # ovs-vsctl show
> > 7c17d701-cc3d-4804-8094-5f92e090daa8
> > Bridge br-ext
> > Port br-ext
> > Interface br-ext
> > type: internal
> > Port patch-ext-patch-to-br-int
> > Interface patch-ext-patch-to-br-int
> > type: patch
> > options: {peer=patch-br-int-to-ext-patch}
> > Port eth1
> > Interface eth1
> > Bridge br-int
> > fail_mode: secure
> > datapath_type: system
> > Port br-int
> > Interface br-int
> > type: internal
> > Port patch-br-int-to-ext-patch
> > Interface patch-br-int-to-ext-patch
> > type: patch
> > options: {peer=patch-ext-patch-to-br-int}
> > ovs_version: “3.4.0"
> >
> > # ovn-nbctl show
> > switch aaa80b25-8168-4944-bcb9-aede4d3f4c94 (SW-EXT)
> > port lsp-ext
> > type: router
> > router-port: lrp-ext
> > port ext-patch
> > type: localnet
> > addresses: ["unknown"]
> > router d75c995e-4d9b-4bd1-af18-9cd24c248f44 (R1)
> > port lrp-ext
> > mac: "00:00:02:00:00:01"
> > ipv6-lla: "fe80::200:2ff:fe00:1"
> > networks: ["10.42.234.1/24", "fd12:3456:789a:1::/64”]
> >
> > # ipv6_ra options on “lrp-ext” in NB
> > ipv6_ra_configs : {address_mode=slaac, max_interval=“4",
> > min_interval=“3", send_periodic="true”}
> >
> > # the same options correctly translated to SB options in
> > “port_binding” table
> > options : {ipv6_ra_address_mode=slaac,
> > ipv6_ra_max_interval="4", ipv6_ra_min_interval="3”,
> > ipv6_ra_prefixes="fd12:3456:789a:1::/64", ipv6_ra_prf=MEDIUM,
> > ipv6_ra_send_periodic="true”,
> > ipv6_ra_src_addr="fe80::200:2ff:fe00:1",
> > ipv6_ra_src_eth="00:00:02:00:00:01", l3gateway-chassis=movn1,
> > peer=lsp-ext}
> >
> > I can see that the packets are generated by controller:
> >
> > Aug 23 10:00:17 movn1 ovn-controller[19122]:
> > ovs|00161|vconn(ovn_pinctrl0)|DBG|unix:/var/snap/microovn/common/ru
> > n/switch//br-int.mgmt: sent (Success): OFPT_PACKET_OUT (OF1.5)
> > (xid=0x3de): in_port=CONTROLLER actions=set_field:0x2-
> > >metadata,set_field:0x1->reg14,set_field:0x10/0x10-
> > >reg10,resubmit(CONTROLLER,8) data_len=110 Aug 23 10:00:17 movn1
> > ovn-controller[19122]:
> > icmp6,vlan_tci=0x0000,dl_src=00:00:02:00:00:01,dl_dst=33:33:00:00:0
> > 0:01,ipv6_src=fe80::200:2ff:fe00:1,ipv6_dst=ff02::1,ipv6_label=0x00
> > 000,nw_tos=0,nw_ecn=0,nw_ttl=255,nw_frag=no,icmp_type=134,icmp_code
> > =0 icmp6_csum:893b
> >
> > However listening on “eth1” either on “alice” or on “ovn-host”, the
> > RAs never show up. Note that if I plug another LSP into SW-EXT,
> > those RAs show up on an interface bound to that LSP.
> > I did a little bit of digging and found that these RA packets are
> > dropped by a rule that’s supposed to prevent leaking of “local
> > only” traffic through localnet ports [1].
>
> I think this was intentional (CC Ihar) to cover the case when a
> distributed OVN router (without any gateway ports) has periodic RA
> enabled and is connected to the fabric via a localnet switch.
Thanks for providing more context. I originally missed the explanation
in the commit that introduced this change [2].
>
> > The reason why I think this is unintentional is that solicited RAs
> > in reply to NS requests from “alice” are answered to the external
> > network without any issues.
> >
>
> This part is indeed problematic. Ihar, what do you think, should we
> block solicited RAs too? Can we make it so only one chassis sends
> them out?
>
> > What would be the best approach to fixing this?
> >
>
> Martin, MJ, if I understand correctly, the router port where you're
> trying to enable periodic RAs is a gateway port (so it will be bound
> to
> exactly on chassis). Maybe a way forward is to change the behavior
> introduced in [1] and only enforce it if the router is not a gateway
> router and if the router port originating the RA is not a gateway
> port.
>
> Would that work?
Yes, this sounds good to me. Our specific use-case is indeed to make
this work primarily for GW routers. However, would it be possible to
also exempt Distributed Gateway Ports? Those also reside only on one
chassis at a time.
>
> > Thanks for any insights,
> > Martin.
> >
> > [0] https://man7.org/linux/man-pages/man5/ovn-nb.5.html (search for
> > “send_periodic”)
> > [1]
> > https://github.com/ovn-org/ovn/blob/32fb58665f93ef033e5a0e748a4f5ee1ed10e03b/controller/physical.c#L1859-L1867
>
> Regards,
> Dumitru
>
Martin.
[2]
https://github.com/ovn-org/ovn/commit/14c6dac51dc87747707ffe678e777277ca776d84
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