[ovs-discuss] [ovn] TCP/UDP traffic dropped between IP addresses defined in allowed address pairs when remote security group is used

Dumitru Ceara dceara at redhat.com
Tue Dec 15 09:45:21 UTC 2020


Hi Krzysztof,

Thanks for the DBs and all the details.

I gave it a try on my local setup, using your DBs.  The behavior below
is identical on v20.06.2, branch-20.12 and current master.

# ovn-nbctl --columns addresses,port_security list logical_switch_port
81d23182-37ac-4d3d-815e-4c25d26fe154
addresses           : ["fa:16:3e:ee:19:b2 10.0.0.11"]
port_security       : ["fa:16:3e:ee:19:b2 10.0.0.11 172.16.0.0/16"]
# ovn-nbctl --columns addresses,port_security list logical_switch_port
8649293f-8ca9-48d0-a0cd-1c2587e48889
addresses           : ["fa:16:3e:bc:20:10 10.0.0.10"]
port_security       : ["fa:16:3e:bc:20:10 10.0.0.10 172.16.0.0/16"]
# ovn-nbctl acl-list pg_ed081ef3_754a_492f_80b2_fb73cd2dceed
from-lport  1002 (inport == @pg_ed081ef3_754a_492f_80b2_fb73cd2dceed &&
ip4) allow-related
from-lport  1002 (inport == @pg_ed081ef3_754a_492f_80b2_fb73cd2dceed &&
ip6) allow-related
  to-lport  1002 (outport == @pg_ed081ef3_754a_492f_80b2_fb73cd2dceed &&
ip4 && ip4.src == $pg_ed081ef3_754a_492f_80b2_fb73cd2dceed_ip4)
allow-related
  to-lport  1002 (outport == @pg_ed081ef3_754a_492f_80b2_fb73cd2dceed &&
ip4 && ip4.src == $pg_ed081ef3_754a_492f_80b2_fb73cd2dceed_ip4 && tcp)
allow-related
  to-lport  1002 (outport == @pg_ed081ef3_754a_492f_80b2_fb73cd2dceed &&
ip4 && ip4.src == 0.0.0.0/0 && icmp4) allow-related
  to-lport  1002 (outport == @pg_ed081ef3_754a_492f_80b2_fb73cd2dceed &&
ip4 && ip4.src == 0.0.0.0/0 && tcp && tcp.dst == 22) allow-related
  to-lport  1002 (outport == @pg_ed081ef3_754a_492f_80b2_fb73cd2dceed &&
ip4 && ip4.src == 0.0.0.0/0 && udp && udp.dst == 12345) allow-related
  to-lport  1002 (outport == @pg_ed081ef3_754a_492f_80b2_fb73cd2dceed &&
ip6 && ip6.src == $pg_ed081ef3_754a_492f_80b2_fb73cd2dceed_ip6)
allow-related
# ovn-sbctl list address_set pg_ed081ef3_754a_492f_80b2_fb73cd2dceed_ip4
_uuid               : e0769c02-d3a6-48e4-ab50-124785c501fd
addresses           : ["10.0.0.10", "10.0.0.11", "172.16.0.104",
"172.16.0.147", "172.17.0.136", "172.17.0.149", "172.17.0.161",
"172.17.0.6", "172.17.0.7", "172.17.0.94"]
name                : pg_ed081ef3_754a_492f_80b2_fb73cd2dceed_ip4

For TCP traffic 172.16.0.11 -> 172.16.0.10 we don't hit any of the
allow-related ACLs.  172.16.0.11 is not set as a port address on port
81d23182-37ac-4d3d-815e-4c25d26fe154 so it will not be included in the
auto-generated address_set pg_ed081ef3_754a_492f_80b2_fb73cd2dceed_ip4.

On the other hand, for TCP traffic 10.0.0.11 -> 172.16.0.10 we hit the
4th allow-related ACL:
to-lport  1002 (outport == @pg_ed081ef3_754a_492f_80b2_fb73cd2dceed &&
ip4 && ip4.src == $pg_ed081ef3_754a_492f_80b2_fb73cd2dceed_ip4 && tcp)
allow-related

ICMP traffic matches the 5th allow-related ACL which doesn't check
source IPs:
to-lport  1002 (outport == @pg_ed081ef3_754a_492f_80b2_fb73cd2dceed &&
ip4 && ip4.src == 0.0.0.0/0 && icmp4) allow-related

So, unless I'm missing something, OVN is doing what it's supposed to do
based on the current configuration.  To avoid adding a new ACL, one
option would be to add the 172.16.0.10 and 172.16.0.11 IPs to the
corresponding logical_switch_ports "addresses" column, i.e., something like:

# ovn-nbctl lsp-set-addresses 81d23182-37ac-4d3d-815e-4c25d26fe154
"fa:16:3e:ee:19:b2 10.0.0.11 172.16.0.11"
# ovn-nbctl lsp-set-addresses 8649293f-8ca9-48d0-a0cd-1c2587e48889
"fa:16:3e:bc:20:10 10.0.0.10 172.16.0.10"
# ovn-nbctl --columns addresses,port_security list logical_switch_port
81d23182-37ac-4d3d-815e-4c25d26fe154
addresses           : ["fa:16:3e:ee:19:b2 10.0.0.11 172.16.0.11"]
port_security       : ["fa:16:3e:ee:19:b2 10.0.0.11 172.16.0.0/16"]
# ovn-nbctl --columns addresses,port_security list logical_switch_port
8649293f-8ca9-48d0-a0cd-1c2587e48889
addresses           : ["fa:16:3e:bc:20:10 10.0.0.10 172.16.0.10"]
port_security       : ["fa:16:3e:bc:20:10 10.0.0.10 172.16.0.0/16"]

Now TCP traffic between 172.16.0.11 and 172.16.0.10 is allowed:
$ ip netns exec vm2 nc -z -v -s 172.16.0.11 172.16.0.10 8000
Ncat: Version 7.50 ( https://nmap.org/ncat )
Ncat: Connected to 172.16.0.10:8000.
Ncat: 0 bytes sent, 0 bytes received in 0.02 seconds.

Thanks,
Dumitru


On 12/14/20 4:43 PM, Krzysztof Klimonda wrote:
> Hi Numan,
> 
> https://signal.klimonda.com/ovnnb.db-broken.txt - this is the "initial" state where TCP is not being established (but ping works)
> https://signal.klimonda.com/ovnnb.db-working.txt - this is after I create a separate IP-based rule to allow TCP traffic
> 
> In both examples, security group in question is ed081ef3-754a-492f-80b2-fb73cd2dceed which is mapped to pg_ed081ef3_754a_492f_80b2_fb73cd2dceed port group.
> 
> In the second ovnnb.db (ovnnb.db-working.txt), there is an extra ACL fb464efc-f63b-494b-b59b-6c2860dcecba added from CLI via:
> 
> `openstack security group rule create --ingress --protocol tcp --remote-ip 172.16.0.0/24 default`
> 
> -- Krzysztof Klimonda kklimonda at syntaxhighlighted.com On Mon, Dec 14,
> 2020, at 14:14, Numan Siddique wrote:
>> On Mon, Dec 14, 2020 at 4:01 PM Krzysztof Klimonda
>> <kklimonda at syntaxhighlighted.com> wrote:
>>> Hi,
>>>
>>> After upgrading to OVN 20.12.0 snapshot d8bc0377c I've noticed a problem in communication between VMs that use allowed address pairs and remote group id in security groups. I believe it has worked properly with OVN 20.06.2 release (although I have no way of verifying it right now).
>>>
>> Thanks for reporting the issue.
>>
>> Is it possible for you to share the OVN NB DB somewhere ?
>>
>> It would be easier to reproduce the issue with the DB.
>>
>> Thanks
>> Numan
>>
>>> Given the following scenario:
>>>
>>> - 2 VMs with IP addresses: vm-a with IP addresses 10.0.0.10 and 172.16.0.10 and vm-b with IP addresses 10.0.0.11 and 172.16.0.11 where 10.0.0.0/8 addresses are set on ports, and 172.16.0.0/16 addresses are set in allowed-address for on ports
>>> - There is single security group attached to both ports allowing for ingress tcp traffic coming from the same security group (remote-group)
>>> - There is a TCP service listening on 10.0.0.10 on port 8000
>>>
>>> When I try accessing service from vm-b using 10.0.0.10 address, ovn forwards traffic properly. However, when I try accessing same service via 172.16.0.10 traffic is dropped.
>>>
>>> When I trace packets between VMs using ovn-trace, for first scenario the last step is:
>>>
>>> ----8<----8<----
>>> ct_next(ct_state=est|trk /* default (use --ct to customize) */)
>>> ---------------------------------------------------------------
>>>  4. ls_out_acl_hint (ovn-northd.c:5292): !ct.new && ct.est && !ct.rpl && ct_label.blocked == 0, priority 4, uuid ab5a233e
>>>     reg0[8] = 1;
>>>     reg0[10] = 1;
>>>     next;
>>>  5. ls_out_acl (ovn-northd.c:5498): reg0[8] == 1 && (outport == @pg_ed081ef3_754a_492f_80b2_fb73cd2dceed && ip4 && ip4.src == $pg_ed081ef3_754a_492f_80b2_fb73cd2dceed_ip4 && tcp), priority 2002, uuid d92706d4
>>>     next;
>>>  9. ls_out_port_sec_ip (ovn-northd.c:4525): outport == "864929" && eth.dst == fa:16:3e:bc:20:10 && ip4.dst == {255.255.255.255, 224.0.0.0/4, 10.0.0.10, 172.16.0.0/16}, priority 90, uuid ff3390b1
>>>     next;
>>> 10. ls_out_port_sec_l2 (ovn-northd.c:4929): outport == "864929" && eth.dst == {fa:16:3e:bc:20:10}, priority 50, uuid af91c05c
>>>     output;
>>>     /* output to "864929", type "" */
>>> ----8<----8<----
>>>
>>> However, when I use 172.16.0.0/24 addresses, the last step changes to:
>>>
>>> ----8<----8<----
>>> ct_next(ct_state=est|trk /* default (use --ct to customize) */)
>>> ---------------------------------------------------------------
>>>  4. ls_out_acl_hint (ovn-northd.c:5292): !ct.new && ct.est && !ct.rpl && ct_label.blocked == 0, priority 4, uuid ab5a233e
>>>     reg0[8] = 1;
>>>     reg0[10] = 1;
>>>     next;
>>>  5. ls_out_acl (ovn-northd.c:5553): reg0[10] == 1 && (outport == @neutron_pg_drop && ip), priority 2001, uuid e36c0840
>>>     ct_commit { ct_label.blocked = 1; };
>>> ----8<----8<----
>>>
>>> Further notes:
>>>
>>> - ICMP traffic between 172.16.0.0/24 addresses is forwarded correctly, with last step of ovn-trace being:
>>>
>>> ----8<----8<----
>>> ct_next(ct_state=est|trk /* default (use --ct to customize) */)
>>> ---------------------------------------------------------------
>>>  4. ls_out_acl_hint (ovn-northd.c:5292): !ct.new && ct.est && !ct.rpl && ct_label.blocked == 0, priority 4, uuid ab5a233e
>>>     reg0[8] = 1;
>>>     reg0[10] = 1;
>>>     next;
>>>  5. ls_out_acl (ovn-northd.c:5498): reg0[8] == 1 && (outport == @pg_ed081ef3_754a_492f_80b2_fb73cd2dceed && ip4 && ip4.src == 0.0.0.0/0 && icmp4), priority 2002, uuid cd1705d8
>>>     next;
>>>  9. ls_out_port_sec_ip (ovn-northd.c:4525): outport == "864929" && eth.dst == fa:16:3e:bc:20:10 && ip4.dst == {255.255.255.255, 224.0.0.0/4, 10.0.0.10, 172.16.0.0/16}, priority 90, uuid ff3390b1
>>>     next;
>>> 10. ls_out_port_sec_l2 (ovn-northd.c:4929): outport == "864929" && eth.dst == {fa:16:3e:bc:20:10}, priority 50, uuid af91c05c
>>>     output;
>>>     /* output to "864929", type "" */
>>> ----8<----8<----
>>>
>>> - If I replace security group rule, changing remote group to remote ip, traffic is forwarded correctly and last step in ovn-trace is:
>>>
>>> ----8<----8<----
>>> ct_next(ct_state=est|trk /* default (use --ct to customize) */)
>>> ---------------------------------------------------------------
>>>  4. ls_out_acl_hint (ovn-northd.c:5292): !ct.new && ct.est && !ct.rpl && ct_label.blocked == 0, priority 4, uuid ab5a233e
>>>     reg0[8] = 1;
>>>     reg0[10] = 1;
>>>     next;
>>>  5. ls_out_acl (ovn-northd.c:5498): reg0[8] == 1 && (outport == @pg_ed081ef3_754a_492f_80b2_fb73cd2dceed && ip4 && ip4.src == 172.16.0.0/24 && tcp), priority 2002, uuid a0871ca2
>>>     next;
>>>  9. ls_out_port_sec_ip (ovn-northd.c:4525): outport == "864929" && eth.dst == fa:16:3e:bc:20:10 && ip4.dst == {255.255.255.255, 224.0.0.0/4, 10.0.0.10, 172.16.0.0/16}, priority 90, uuid ff3390b1
>>>     next;
>>> 10. ls_out_port_sec_l2 (ovn-northd.c:4929): outport == "864929" && eth.dst == {fa:16:3e:bc:20:10}, priority 50, uuid af91c05c
>>>     output;
>>>     /* output to "864929", type "" */
>>> ----8<----8<----
>>>
>>> --
>>>   Krzysztof Klimonda
>>>   kklimonda at syntaxhighlighted.com
>>> _______________________________________________
>>> discuss mailing list
>>> discuss at openvswitch.org
>>> https://mail.openvswitch.org/mailman/listinfo/ovs-discuss
>>>
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