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[Bug 1463911] Re: IPV6 fragmentation and mtu issue


Test methodology performed on 3.19 kernel with patch applied:

Host A: fd01:2222::1/64 direct connect to host C

ip addr add fd01:2222::1/64 dev eth0

Host B: fd01:2222::2/64 direct connect to host C

ip addr add fd01:2222::2/64 dev eth0

host C: direct connect interfaces for Hosts A & B bridged together:

brctl addbr testbr0
brctl addif testbr0 eth1
brctl addif testbr0 eth5
ip link set dev eth1 up
ip link set dev eth5 up
ip link set dev testbr0 up
ip addr add fd01:2222::99/64 dev testbr0

host A:

continuous ping6 to host C's address beyond the bridge, using size large
enough to generate fragmented IPv6 datagrams for mtu setting of 1500:

ping6 -s 4000 fd01:2222::2

host C:

load ip6tables_nat:

ip6tables -t nat -Ln

Observe on host A that ping continues uninterrupted

Inspect eth1 and eth5 interfaces on host C with tcpdump to confirm traffic passes
through the bridge

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  IPV6 fragmentation and mtu issue

Status in neutron:
Status in OpenStack Compute (nova):
Status in linux package in Ubuntu:

Bug description:
  Fragmented IPv6 packets are REJECTED by ip6tables on compute nodes.
  The traffic is goign through an intra-VM network and the packet loss
  is hurting the system.

  There is a patch for this issue:

  I would like to know is there any bug report or official release date
  for this issue ?

  This is pretty critical for my deployment.

  Thanks in advance,



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