docker problem on ubuntu 14.04

$ service docker restart
stop: Unknown instance: 
docker start/running, process 22604

$ service docker status
docker start/running, process 22992

$ service docker status
docker start/running, process 23093

$ docker ps
2014/11/12 09:56:11 Get http:///var/run/docker.sock/v1.15/containers/json: read unix /var/run/docker.sock: connection reset by peer

$ service docker stop
docker stop/waiting

$ docker -d
2014/11/12 09:57:12 docker daemon: 1.3.1 4e9bbfa; execdriver: native; graphdriver: 
[df63e949] +job serveapi(unix:///var/run/docker.sock)
[info] Listening for HTTP on unix (/var/run/docker.sock)
[df63e949] +job init_networkdriver()
Unable to enable network bridge NAT: iptables failed: iptables --wait -I POSTROUTING -t nat -s 172.17.42.1/16 ! -o docker0 -j MASQUERADE: iptables v1.4.21: can't initialize iptables table `nat': Table does not exist (do you need to insmod?)
Perhaps iptables or your kernel needs to be upgraded.
 (exit status 3)
[df63e949] -job init_networkdriver() = ERR (1)
2014/11/12 09:57:13  (exit status 3)

$ iptables -t nat -F
iptables v1.4.21: can't initialize iptables table `nat': Table does not exist (do you need to insmod?)
Perhaps iptables or your kernel needs to be upgraded.

/var/log/syslog
Nov 12 09:56:03 csystems kernel: [56122.269577] init: docker main process (22604) terminated with status 1
Nov 12 09:56:03 csystems kernel: [56122.269585] init: docker main process ended, respawning
Nov 12 09:56:03 csystems kernel: [56122.834056] init: docker main process (22651) terminated with status 1
Nov 12 09:56:03 csystems kernel: [56122.834063] init: docker main process ended, respawning

https://github.com/docker/docker/issues/866?source=c
> Missing the 'nat' table is a symptom of missing kernel modules.

task: rebuild iptables kernel modules since I have a custom kernel

https://github.com/docker/docker/issues/866?source=c#issuecomment-43093182
> I was missing IP_NF_TARGET_MASQUERADE in my kernel config.

$ make menuconfig
Location:
-> Networking support (NET [=y])
   -> Networking options
      -> Network packet filtering framework (Netfilter) (NETFILTER [=y])
         -> IP: Netfilter Configuration
            -> IP tables support (required for filtering/masq/NAT) (IP_NF_IPTABLES [=m])
               -> iptables NAT support (IP_NF_NAT [=n])                                                                                                

iptables NAT support
- MASQUERADE target support
- NETMAP target support
- REDIRECT target support