[SRU][Xenial][PATCH 0/7] Fixes for LP#1715812

Daniel Axtens daniel.axtens at canonical.com
Fri Sep 8 07:01:35 UTC 2017


(This is the Xenial patchset. Some patches required minor backporting.)

[SRU Justification]

[Impact]
A host can lose access to another host whose MAC address changes if
they have active connections to other hosts that share a route. The
ARP cache does not time out as expected - instead the old MAC address
is continuously reconfirmed.

[Fix]
Apply series [1], which changes the algorithm for neighbour confirmation.
That is, from upstream:
51ce8bd4d17a net: pending_confirm is not used anymore
0dec879f636f net: use dst_confirm_neigh for UDP, RAW, ICMP, L2TP
63fca65d0863 net: add confirm_neigh method to dst_ops
c3a2e8370534 tcp: replace dst_confirm with sk_dst_confirm
c86a773c7802 sctp: add dst_pending_confirm flag
4ff0620354f2 net: add dst_pending_confirm flag to skbuff
9b8805a32559 sock: add sk_dst_pending_confirm flag

[Test case]
Create 3 real or virtual systems, all hooked up to a switch.
One system needs an active-backup bond with fail_over_mac=1 num_grat_arp=0.

Put all the systems in the same subnet, e.g. 192.168.200.0/24

Call the system with the bond A, and the other two systems B and C.

On B, run in 3 shells:
 - netperf -t TCP_RR to C
 - ping -f A
 - watch 'ip -s neigh show 192.168.200.0/24'

On A, cause the bond to fail over.

Observe that:

 - without the patches, B intermittently fails to notice the change in
   A's MAC address. This presents as the ping failing and not
   recovering, and the arp table showing the old mac address never
   timing out and never being replace with a new mac address.

 - with the patches, the arp cache times out and B sends another mac
   probe and detects A's new address.

It helps to use taskset to put ping and netperf on the same CPU, or use single-CPU vms.

See [2] for more details.

[References]
[2] Original report: https://www.mail-archive.com/netdev@vger.kernel.org/msg138762.html
[1]: https://www.spinics.net/lists/linux-rdma/msg45907.html

Julian Anastasov (7):
  sock: add sk_dst_pending_confirm flag
  net: add dst_pending_confirm flag to skbuff
  sctp: add dst_pending_confirm flag
  tcp: replace dst_confirm with sk_dst_confirm
  net: add confirm_neigh method to dst_ops
  net: use dst_confirm_neigh for UDP, RAW, ICMP, L2TP
  net: pending_confirm is not used anymore

 drivers/net/vrf.c          |  5 ++++-
 include/linux/skbuff.h     | 12 ++++++++++++
 include/net/arp.h          | 16 ++++++++++++++++
 include/net/dst.h          | 21 +++++++++------------
 include/net/dst_ops.h      |  2 ++
 include/net/ndisc.h        | 17 +++++++++++++++++
 include/net/sctp/sctp.h    |  6 ++----
 include/net/sctp/structs.h |  4 ++++
 include/net/sock.h         | 25 +++++++++++++++++++++++++
 net/core/dst.c             |  1 -
 net/core/sock.c            |  2 ++
 net/ipv4/ip_output.c       | 11 ++++++++++-
 net/ipv4/ping.c            |  3 ++-
 net/ipv4/raw.c             |  6 +++++-
 net/ipv4/route.c           | 19 +++++++++++++++++++
 net/ipv4/tcp_input.c       | 12 +++---------
 net/ipv4/tcp_metrics.c     |  7 ++-----
 net/ipv4/tcp_output.c      |  2 ++
 net/ipv4/udp.c             |  3 ++-
 net/ipv6/ip6_output.c      |  7 +++++++
 net/ipv6/raw.c             |  6 +++++-
 net/ipv6/route.c           | 43 ++++++++++++++++++++++++++++++-------------
 net/ipv6/udp.c             |  3 ++-
 net/l2tp/l2tp_ip6.c        |  3 ++-
 net/sctp/associola.c       |  3 +--
 net/sctp/output.c          | 10 +++++++++-
 net/sctp/outqueue.c        |  2 +-
 net/sctp/sm_make_chunk.c   |  6 ++----
 net/sctp/sm_sideeffect.c   |  2 +-
 net/sctp/socket.c          |  4 ++--
 net/sctp/transport.c       | 16 +++++++++++++++-
 net/xfrm/xfrm_policy.c     | 19 +++++++++++++++++++
 32 files changed, 234 insertions(+), 64 deletions(-)

-- 
2.11.0





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