The forwarding database (fdb) of Linux VXLAN links are restricted to
entries with destination VXLAN tunnel endpoint (VTEP) address of a
single address family. Which address family is permitted is set when the
link is created and cannot be modified. The overlay network driver
creates VXLAN links such that the kernel only allows fdb entries to be
created with IPv4 destination VTEP addresses. If the Swarm is configured
with IPv6 advertise addresses, creating fdb entries for remote peers
fails with EAFNOSUPPORT (address family not supported by protocol).
Make overlay networks functional over IPv6 transport by configuring the
VXLAN links for IPv6 VTEPs if the local node's advertise address is an
IPv6 address. Make encrypted overlay networks secure over IPv6 transport
by applying the iptables rules to the ip6tables when appropriate.
Signed-off-by: Cory Snider <csnider@mirantis.com>
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