currently only ipv4 socket is open. if container is pure ipv6, there is no way to connect:
```
root@kube-node-6:~# nsenter -t 20122 -n ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: ip6tnl0@NONE: <NOARP> mtu 1452 qdisc noop state DOWN group default qlen 1000
link/tunnel6 :: brd ::
4: eth0@if246: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default
link/ether c2:a9:a6:c7:38:59 brd ff:ff:ff:ff:ff:ff link-netnsid 0
inet6 fde4💯0:6::5c3/64 scope global
valid_lft forever preferred_lft forever
inet6 fe80::c0a9:a6ff:fec7:3859/64 scope link
valid_lft forever preferred_lft forever
root@kube-node-6:~# nsenter -t 20122 -n netstat -lnp
Active Internet connections (only servers)
```
```
root@kube-node-6:~# nsenter -t 20122 -n netstat -lnp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN 20286/nginx: master
udp 0 0 0.0.0.0:161 0.0.0.0:* 20288/snmpd
Active UNIX domain sockets (only servers)
```