[NETVIRT-1471]  ipv6 stateful mode subnet need to be added to the router for pinging across VMs Created: 24/Oct/18  Updated: 30/Oct/18  Resolved: 30/Oct/18

Status: Resolved
Project: netvirt
Component/s: ipv6service
Affects Version/s: None
Fix Version/s: Neon

Type: Bug Priority: High
Reporter: RajaRajan Manickam Assignee: Karthikeyan Krishnan
Resolution: Won't Do Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified


 Description   

1. TROUBLE DESCRIPTION
1.1. Trouble summary
To ping6 across VMs , ipv6 stateful mode subnet need to be added to the router or else ping6 will fail
since MAC addreess getting resolved only adding  to the router. Looks like design need to be change
 ostinato@ostinato:~$ ifconfig
ens3      Link encap:Ethernet  HWaddr fa:16:3e:fa:22:9c  
          inet addr:10.10.10.8  Bcast:10.10.10.255  Mask:255.255.255.0
          inet6 addr: 2001:db8:aaaa::f/128 Scope:Global
          inet6 addr: fe80::f816:3eff:fefa:229c/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:9000  Metric:1
          RX packets:13341 errors:0 dropped:0 overruns:0 frame:0
          TX packets:13350 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:1169148 (1.1 MB)  TX bytes:1169279 (1.1 MB)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:160 errors:0 dropped:0 overruns:0 frame:0
          TX packets:160 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1
          RX bytes:11840 (11.8 KB)  TX bytes:11840 (11.8 KB)

ostinato@ostinato:~$ ping6 2001:db8:aaaa::a
PING 2001:db8:aaaa::a(2001:db8:aaaa::a) 56 data bytes
64 bytes from 2001:db8:aaaa::a: icmp_seq=1 ttl=64 time=0.411 ms
64 bytes from 2001:db8:aaaa::a: icmp_seq=2 ttl=64 time=0.280 ms
^C

1.3. Frequency of fault
Seen multiple times

1.4. Workaround and Recovery
Need to add to the router

1.5. System impact

ipv6 stateful mode is not working as expected

1.6. Known problem within the OpenStack community?
NA

2. Configuration data
2.1. HW Configuration details
EBS, HP or DELL:
Number of subracks:
Number of blades:
EMC (Yes or No):
Switches used (X670V, X770 or BD):

2.2. SW Configuration details
CEE-  CEE8RC2
CSC - 19.1.1.0-269
CSS -2.8.2.css5.R2C

 Comments   
Comment by Sridhar Gaddam [ 26/Oct/18 ]

rajamk, in the above logs the VM IPv6 address is shown as "2001:db8:aaaa::f/128"
May i know how you created the IPv6 Subnet? Also, if you do not associate a router to the subnet there will not be any Router Advertisements sent over the network. So, please share the detailed steps.

Comment by Karthikeyan Krishnan [ 26/Oct/18 ]

Have tested the IPv6 L2 data traffic with DHCPv6 state-full address mode and below are the our observations/findings.

  •  After booted the dual stack VMs (Host OS: Ubuntu 16.04.3  LTS), explicitly initiated the DHCPv6 request(solicit) on the VM console using the command "dhclient -6 <eth0>"
  •  After the dhcpv6 client request, VMs are got the IPv6 GUA addresses via openstack q-dhcp service(Advertise/Request/Reply).

We are observing IPv6 default route information is not configured by DHCPv6 process. It is taken care of IPv6 GUA address assignment only. Please find attached pcap file for booted VM.

Manually added "default route" information on the booted VMs from the same subnet, after that L2 data traffic is working fine.

Conclusion:

  •    DHCPv6 State-full mode: IPAM only handled by DHCPv6 server. Adding default route information to the client is done by via "router advertisement" packet.
  •    DHCPv6 State-less Mode: Other configurations like DNS Domain Suffix, etc is handled by DHCPv6 server. Both IPAM and default route configuration to the client is done by via "router advertisement" packet.
  •    SLAAC Mode: IPAM and default route configuration to the client is done by via "router advertisement" packet.

In all of the supported IPv6 address mode router advertisement is mandatory to work properly L2 traffic.

Comment by Karthikeyan Krishnan [ 30/Oct/18 ]
  •    DHCPv6 State-full mode: IPAM only handled by DHCPv6 server. Adding default route information to the client is done by via "router advertisement" packet.
  •    DHCPv6 State-less Mode: Other configurations like DNS Domain Suffix, etc is handled by DHCPv6 server. Both IPAM and default route configuration to the client is done by via "router advertisement" packet.
  •    SLAAC Mode: IPAM and default route configuration to the client is done by via "router advertisement" packet.

In all of the supported IPv6 address mode router advertisement is mandatory to work properly L2 traffic.

 

i.e: DHCP for IPv4 = functionality DHCPv6 + RA (via router).

 

Hence closing this bug now.

Comment by Sridhar Gaddam [ 30/Oct/18 ]

Yes in IPv6 use-cases, the RA plays an important role and VMs learn the default route via the RA.

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