Error creating vxlan interface: file exists

Previous related threads:

• https://github.com/docker/libnetwork/issues/562
• https://github.com/docker/libnetwork/issues/751
• https://github.com/docker/libnetwork/issues/945
• https://github.com/moby/moby/issues/21482
• https://github.com/moby/moby/issues/28559

Comment at the current tail-end of #945 recommends opening a new ticket. I couldn't find one opened by the original poster, so here we go.

I've been using swarm for the past couple of months, and frequently hit upon this problem. I have a modest swarm (~8-9 nodes) all running Ubuntu 16.04, now with Docker 17.05-ce on. There is not a great amount of container churn, but I do use a stack yaml file to deploy ~20 services across ~20 encrypted overlay networks.

I tend to find that after a couple of stack deploy / stack rm cycles, my containers get killed at startup with the "Error creating vxlan: file exists" error. This prevents the containers coming up on a host and forces them to attempt to relocate, which may / may not work.

I have noted in the above issues that the problems are, several times over, thought to have been rectified, but yet always creep back in for various users.

To rectify the issue, I have tried rebooting the node, restarting iptables, removing the stack and re-creating, all of which work to varying degrees but are most definitely workarounds and not solutions.

I cannot think how I can attempt to reproduce this error, but if anyone wants to suggest ways to debug, I am at your service.

No files or tests are named. Start by reviewing related issues #562, #751, #945, moby/moby #21482 and #28559, then investigate repeated stack deploy/rm cycles with encrypted overlay networks on Ubuntu 16.04. Done means identifying why VXLAN creation reports “file exists” and preventing the resulting container startup failure.