Linux – Docker will only bind forwarded ports to IPv6 interfaces

ipv4ipv6linuxnetworkingUbuntu

Is there a way I can tell docker to only bind forwarded ports to IPv4 interfaces?

I have a machine running on Digital Ocean with IPv6 disabled:

# echo '1' > /proc/sys/net/ipv6/conf/lo/disable_ipv6  
# echo '1' > /proc/sys/net/ipv6/conf/lo/disable_ipv6  
# echo '1' > /proc/sys/net/ipv6/conf/all/disable_ipv6  
# echo '1' > /proc/sys/net/ipv6/conf/default/disable_ipv6
# /etc/init.d/networking restart

ifconfig reports there are no IPv6-enabled interfaces:

# ifconfig
docker0   Link encap:Ethernet  HWaddr 00:00:00:00:00:00  
          inet addr:172.17.42.1  Bcast:0.0.0.0  Mask:255.255.0.0
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:1372 errors:0 dropped:0 overruns:0 frame:0
          TX packets:7221 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:88091 (88.0 KB)  TX bytes:10655750 (10.6 MB)

eth0      Link encap:Ethernet  HWaddr 04:01:08:c1:b1:01  
          inet addr:198.XXX.XXX.XXX  Bcast:198.199.90.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:97602 errors:0 dropped:4 overruns:0 frame:0
          TX packets:15362 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:141867997 (141.8 MB)  TX bytes:1376970 (1.3 MB)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

lxcbr0    Link encap:Ethernet  HWaddr 9e:51:04:ed:13:d4  
          inet addr:10.0.3.1  Bcast:10.0.3.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

When I launch a new docker container and ask it to port forward 8000 to 8000 in the container it does so only on IPv6 interfaces. Is there a way to make it only bind to IPv4 interfaces?

# docker run -p 8000:8000 -i -t colinsurprenant/ubuntu-raring-amd64 /bin/bash

# lsof -OnP | grep LISTEN
sshd      1275             root    3u     IPv4 ... TCP *:22 (LISTEN)
sshd      1275             root    4u     IPv6 ... TCP *:22 (LISTEN)
dnsmasq   2975      lxc-dnsmasq    7u     IPv4 ... TCP 10.0.3.1:53 (LISTEN)
docker    9629             root    7u     IPv6 ... TCP *:8000 (LISTEN)
docker    9629 9630        root    7u     IPv6 ... TCP *:8000 (LISTEN)
docker    9629 9631        root    7u     IPv6 ... TCP *:8000 (LISTEN)
docker    9629 9632        root    7u     IPv6 ... TCP *:8000 (LISTEN)
docker    9629 9633        root    7u     IPv6 ... TCP *:8000 (LISTEN)
docker    9629 9634        root    7u     IPv6 ... TCP *:8000 (LISTEN)
docker    9629 9698        root    7u     IPv6 ... TCP *:8000 (LISTEN)

Best Answer

I ran through the same issue:

Edit /etc/modprobe.d/blacklist.conf with:

blacklist ipv6

And /etc/default/grub with:

GRUB_CMDLINE_LINUX_DEFAULT="ipv6.disable=1 console=ttyS0"

Then update-grub and reboot.