[ovs-discuss] OVS drops icmpv6 packets for actions:NORMAL

[Gregory Rose]

On 10/16/2019 3:18 PM, Ben Pfaff wrote:
> On Tue, Oct 15, 2019 at 04:11:16PM -0700, Gregory Rose wrote:
>> On 10/15/2019 3:18 PM, PATEL Harsh wrote:
>>> Hey Ben,
>>> Thanks for your response. I am using Linux 4.1.52 os. And can you please
>>> tell me what happens when this Normal flows drops packet I mean which
>>> part is responsible for this failure. Because for some traffics like
>>> ipv4 unicast and ipv6 unicast this flow works. Just for icmpv6 it drops
>>> the packet.
>>>
>> Could be your kernel - I'd try a newer one.
> Do you have a reason to believe that?  How OVS translates flows isn't
> too kernel version dependent.

I have seen a lot of kernel bugs (maybe we should call them unintended 
side effects) in ICMPV6 handling.  It's just
a suggestion to see if it makes a difference.  Depending on how other 
rules on the system are set up the ICMPv6
packets might get dropped in the kernel.

I noted that you are not having the same issue when you try branch 2.8.2 
so I'm wondering if there's
a kernel issue or perhaps other system rules (IP tables?) that are 
interfering.

Thanks,

- Greg

>
>>> ------------------------------------------------------------------------
>>> *From:* Ben Pfaff <blp at ovn.org>
>>> *Sent:* Tuesday, October 15, 2019 1:30 PM
>>> *To:* PATEL Harsh <harsh.patel at sagemcom.com>
>>> *Cc:* ovs-discuss at openvswitch.org <ovs-discuss at openvswitch.org>
>>> *Subject:* Re: [ovs-discuss] OVS drops icmpv6 packets for actions:NORMAL
>>> On Tue, Oct 15, 2019 at 07:22:11PM +0000, PATEL Harsh wrote:
>>>> Hi,
>>>> I have been using openvswitch version 2.8.2. And I haven't added any
>>>> flows to forward traffic. Just the default one that is as followed.
>>> With
>>>> this flow seems like my bridge BR_LAN drops incoming icmpv6 traffice
>>>> from LAN client. There is also detailed flow as follows in that it says
>>>> datapath actions: drop. I don't know why this is happening can you
>>>> please help me with that?
>>>>
>>>>     ovs-ofctl dump-flows BR_LAN
>>>>     cookie=0x0, duration=7210.426s, table=0, n_packets=117886,
>>>> n_bytes=85217235, priority=0 actions=NORMAL
>>>>
>>>>
>>>> Detailed flow for LAN client:
>>>>
>>>> ovs-appctl ofproto/trace BR_LAN dl_src=00:00:00:04:eb:d0,dl_dst=
>>>> 33:33:00:00:00:fb,dl_type=0x86dd
>>>> Flow:
>>>> ipv6,in_port=ANY,vlan_tci=0x0000,dl_src=00:00:00:04:eb:d0,dl_dst=33:33:00:00:00:fb,ipv6_src=::,ipv6_dst=::,ipv6_label=0x00000,nw_proto=0,nw_tos=0,nw_ecn=0,nw_ttl=0
>>>>
>>>> bridge("BR_LAN")
>>>> ----------------
>>>>     0. priority 0
>>>>        NORMAL
>>>>
>>>> Final flow: unchanged
>>>> Megaflow:
>>>> recirc_id=0,eth,ipv6,in_port=ANY,vlan_tci=0x0000/0x1fff,dl_src=00:00:00:04:eb:d0,dl_dst=33:33:00:00:00:fb,ipv6_dst=::,nw_proto=0,nw_frag=no
>>>> Datapath actions: drop
>>> With recent OVS, I'm not seeing this problem:
>>>
>>>      [bpfaff at sigfpe tutorial]$ ovs-vsctl add-br BR_LAN
>>>      [bpfaff at sigfpe tutorial]$ ovs-vsctl add-port BR_LAN p0
>>>      [bpfaff at sigfpe tutorial]$ ovs-vsctl add-port BR_LAN p1
>>>      [bpfaff at sigfpe tutorial]$ ovs-vsctl add-port BR_LAN p2
>>>      [bpfaff at sigfpe tutorial]$ ovs-appctl ofproto/trace BR_LAN
>>> dl_src=00:00:00:04:eb:d0,dl_dst=33:33:00:00:00:fb,dl_type=0x86dd
>>>      Flow: ipv6,in_port=ANY,vlan_tci=0x0000,dl_src=00:00:00:04:eb:d0,dl_dst=33:33:00:00:00:fb,ipv6_src=::,ipv6_dst=::,ipv6_label=0x00000,nw_proto=0,nw_tos=0,nw_ecn=0,nw_ttl=0
>>>
>>>      bridge("BR_LAN")
>>>      ----------------
>>>       0. priority 0
>>>          NORMAL
>>>           -> no learned MAC for destination, flooding
>>>
>>>      Final flow: unchanged
>>>      Megaflow: recirc_id=0,eth,ipv6,in_port=ANY,dl_src=00:00:00:04:eb:d0,dl_dst=33:33:00:00:00:fb,nw_frag=no
>>>      Datapath actions: 1,2,3,4
>>>      [bpfaff at sigfpe tutorial]$
>>>
>>> I also don't see the problem when I go back to the latest 2.8.x.
>>>
>>> I wonder what's different about your setup.
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