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[Joseph Salisbury <joseph.salisbury@xxxxxxxxxxxxx>]

** Changed in: linux (Ubuntu)
       Status: In Progress => Fix Released

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https://bugs.launchpad.net/bugs/1634545

Title:
  ipv6: connected routes are missing after a down/up cycle on the
  loopback

Status in linux package in Ubuntu:
  Fix Released
Status in linux source package in Trusty:
  Fix Released
Status in linux source package in Vivid:
  Fix Released
Status in linux source package in Xenial:
  Fix Released
Status in linux source package in Yakkety:
  Fix Released

Bug description:
  This upstream patch is missing:
  http://git.kernel.org/cgit/linux/kernel/git/davem/net.git/commit/?id=a220445f9f4382c36a53d8ef3e08165fa27f7e2c

  ipv6: correctly add local routes when lo goes up

  The goal of the patch is to fix this scenario:
   ip link add dummy1 type dummy
   ip link set dummy1 up
   ip link set lo down ; ip link set lo up

  After that sequence, the local route to the link layer address of dummy1 is
  not there anymore.

  When the loopback is set down, all local routes are deleted by
  addrconf_ifdown()/rt6_ifdown(). At this time, the rt6_info entry still
  exists, because the corresponding idev has a reference on it. After the rcu
  grace period, dst_rcu_free() is called, and thus ___dst_free(), which will
  set obsolete to DST_OBSOLETE_DEAD.

  In this case, init_loopback() is called before dst_rcu_free(), thus
  obsolete is still sets to something <= 0. So, the function doesn't add the
  route again. To avoid that race, let's check the rt6 refcnt instead.

  Fixes: 25fb6ca4ed9c ("net IPv6 : Fix broken IPv6 routing table after loopback down-up")
  Fixes: a881ae1f625c ("ipv6: don't call addrconf_dst_alloc again when enable lo")
  Fixes: 33d99113b110 ("ipv6: reallocate addrconf router for ipv6 address when lo device up")
  Reported-by: Francesco Santoro <francesco.santoro@xxxxxxxxx>
  Reported-by: Samuel Gauthier <samuel.gauthier@xxxxxxxxx>
  CC: Balakumaran Kannan <Balakumaran.Kannan@xxxxxxxxxxx>
  CC: Maruthi Thotad <Maruthi.Thotad@xxxxxxxxxxx>
  CC: Sabrina Dubroca <sd@xxxxxxxxxxxxxxx>
  CC: Hannes Frederic Sowa <hannes@xxxxxxxxxxxxxxxxxxx>
  CC: Weilong Chen <chenweilong@xxxxxxxxxx>
  CC: Gao feng <gaofeng@xxxxxxxxxxxxxx>
  Signed-off-by: Nicolas Dichtel <nicolas.dichtel@xxxxxxxxx>
  Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>

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