Network communication failed when running Docker swarm inside a Sysbox system container

Hi

Given the test suite, it's possible to launch swarm services in a docker swarm inside a sysbox system container but services on the same networks can't communicate with each other:

I initialize a swarm cluster with the help of this test file:

Then I created a network and two services:

docker exec $mgr sh -c "docker network create --attachable=true -d overlay innet"
docker exec $mgr sh -c "docker service create --replicas 1 --network innet --name firstservice alpine ping docker.com"
docker exec $mgr sh -c "docker service create --replicas 1 --network innet --name secondservice alpine ping docker.com"

Then I connect to the firstservice replica and try to ping secondservice:

ping: bad address 'secondservice'

In manager's log:

time="2021-03-30T19:19:01.030773398Z" level=info msg="shim containerd-shim started" address=/containerd-shim/27a7d45d81c1bb86758304c6f770bc730fa970d03cc47daa673f7626a409deae.sock debug=false pid=11675
time="2021-03-30T19:19:01Z" level=warning msg="file does not exist: /proc/sys/net/ipv6/conf/all/disable_ipv6 : stat /proc/sys/net/ipv6/conf/all/disable_ipv6: no such file or directory Has IPv6 been disabled in this node's kernel?"
time="2021-03-30T19:19:05.966424391Z" level=info msg="NetworkDB stats d288bd289303(248d2ba3518c) - netID:8mnt6217s6bfua4qb9fk2keaj leaving:false netPeers:2 entries:4 Queue qLen:0 netMsg/s:0"
time="2021-03-30T19:19:05.966560293Z" level=info msg="NetworkDB stats d288bd289303(248d2ba3518c) - netID:uau5lrwi4lxmf52tycwtist4r leaving:false netPeers:2 entries:8 Queue qLen:0 netMsg/s:0"
time="2021-03-30T19:19:08.268646522Z" level=info msg="Container 510866142c71261d7dc4eea060c0a50e61b58afc34c28225452ded40d6c1f64e failed to exit within 10 seconds of signal 15 - using the force"
time="2021-03-30T19:19:08.431420306Z" level=info msg="shim reaped" id=510866142c71261d7dc4eea060c0a50e61b58afc34c28225452ded40d6c1f64e
time="2021-03-30T19:19:08.441486528Z" level=info msg="ignoring event" module=libcontainerd namespace=moby topic=/tasks/delete type="*events.TaskDelete"
time="2021-03-30T19:19:08.442291287Z" level=warning msg="rmServiceBinding 0c932c01ce0b750e93491916c6494b28b7762560a111299c691229492a5e8711 possible transient state ok:false entries:0 set:false "
time="2021-03-30T19:19:08Z" level=error msg="set up rule failed, [-t mangle -D INPUT -d 10.0.1.2/32 -j MARK --set-mark 256]:  (iptables failed: iptables --wait -t mangle -D INPUT -d 10.0.1.2/32 -j MARK --set-mark 256: iptables: No chain/target/match by that name.\n (exit status 1))"
time="2021-03-30T19:19:08.558023941Z" level=error msg="Failed to delete firewall mark rule in sbox lb_uau5 (lb-inne): reexec failed: exit status 8"
time="2021-03-30T19:19:08.558253463Z" level=error msg="Failed add IP alias 10.0.1.2 to network uau5lrwi4lxmf52tycwtist4r LB endpoint interface eth0: cannot assign requested address"

Start with tests/dind/swarm.bats and reproduce the Docker Swarm setup described in the issue, including the attachable overlay network and two services. Inspect the manager logs and the relevant networking behavior around service-name resolution and firewall rules. Done means services on the same overlay network can communicate by service name inside a Sysbox system container.