This re-applies commit b39d02b with additional iptables rules to solve the issue with containers routing back into themselves.
The previous issue with this attempt was that the DNAT rule would send traffic back into the container it came from. When this happens you have 2 issues.
1) reverse path filtering. The container is going to see the traffic coming in from the outside and it's going to have a source address of itself. So reverse path filtering will kick in and drop the packet.
2) direct return mismatch. Assuming you turned reverse path filtering off, when the packet comes back in, it's goign to have a source address of itself, thus when the reply traffic is sent, it's going to have a source address of itself. But the original packet was sent to the host IP address, so the traffic will be dropped because it's coming from an address which the original traffic was not sent to (and likely with an incorrect port as well).
The solution to this is to masquerade the traffic when it gets routed back into the origin container. However for this to work you need to enable hairpin mode on the bridge port, otherwise the kernel will just drop the traffic.
The hairpin mode set is part of libcontainer, while the MASQ change is part of docker.
This reverts commit 63c303eecd.
Docker-DCO-1.1-Signed-off-by: Patrick Hemmer <patrick.hemmer@gmail.com> (github: phemmer)
If iptables version is < 1.4.11, try to delete the rule vs. checking if it exists. Fixes#6831.
Docker-DCO-1.1-Signed-off-by: Jessica Frazelle <jfrazelle@users.noreply.github.com> (github: jfrazelle)
Hairpin NAT is currently done by passing through the docker server. If
two containers on the same box try to access each other through exposed
ports and using the host IP the current iptables rules will not match the
DNAT and thus the traffic goes to 'docker -d'
This change drops the restriction that DNAT traffic must not originate
from docker0. It should be safe to drop this restriction because the
DOCKER chain is already gated by jumps that check for the destination
address to be a local address.
Docker-DCO-1.1-Signed-off-by: Darren Shepherd <darren.s.shepherd@gmail.com> (github: ibuildthecloud)
Allow publicly mapped ports to be made public beyond the host. This is
needed for distros like Fedora and RHEL which have a reject all rule at
the end of their FORWARD table.
Docker-DCO-1.1-Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> (github: jpoimboe)
