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Network lost after killing and restarting a container

Hello!

I recently observed a problem while running a docker container on a Debian host in VirtualBox:
After starting and stopping a container several times no network connection is possible anymore. I had to restart docker service to get back online.

Docker Version installed:

$ docker -v
Docker version 18.09.6, build 481bc77

The problem is reproduceable with the lightweight busybox image. For instance running the container and killing it after a few seconds, network is still there:

$ docker run  -it --rm busybox ping -c 10 8.8.4.4
PING 8.8.4.4 (8.8.4.4) 56(84) bytes of data.
64 bytes from 8.8.4.4: icmp_seq=1 ttl=53 time=20.2 ms
64 bytes from 8.8.4.4: icmp_seq=2 ttl=53 time=19.5 ms
^C
--- 8.8.4.4 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 3ms
rtt min/avg/max/mdev = 19.516/19.852/20.188/0.336 ms

I ran this sequence of start and abort (or “docker kill …”) several times (2…6 tries) and suddenly I received no answer:

$ docker run  -it --rm busybox ping -c 10 8.8.4.4
PING 8.8.4.4 (8.8.4.4): 56 data bytes

--- 8.8.4.4 ping statistics ---
10 packets transmitted, 0 packets received, 100% packet loss

On the contrary running “ping …” in the debian host always(!!!) works fine, no problems:

$ ping -c 10 8.8.4.4
PING 8.8.4.4 (8.8.4.4) 56(84) bytes of data.
64 bytes from 8.8.4.4: icmp_seq=1 ttl=53 time=55.6 ms
64 bytes from 8.8.4.4: icmp_seq=2 ttl=53 time=63.5 ms
...
64 bytes from 8.8.4.4: icmp_seq=10 ttl=53 time=20.3 ms

--- 8.8.4.4 ping statistics ---
10 packets transmitted, 10 received, 0% packet loss, time 39ms
rtt min/avg/max/mdev = 19.374/31.042/63.483/17.131 ms

To fix the problem, I need to restart docker service:

$ sudo service docker restart

After that, network in busybox container works properly again. Until I start the sequence above…

Does anybody know what I need to check? I’d like to have a stable network connection even if I kill a container and start it again.

Thanks in advance.