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Signed-off-by: Rob Murray <rob.murray@docker.com>
Signed-off-by: Rob Murray <rob.murray@docker.com>
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After enabling IP forwarding in the kernel, for nftables only, don't set the forwarding policy to "drop". It's the user's responsibility to secure their host when they run Docker with nftables. Signed-off-by: Rob Murray <rob.murray@docker.com>
Signed-off-by: Rob Murray <rob.murray@docker.com>
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Next new plan ... #50646 |
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- What I did
When Docker is using iptables and it enables IP forwarding, unless daemon option
--ip-forward-no-dropis true, it sets the iptables filter-FORWARD policy to DROP.When running with nftables - don't do that, just turn the host into a router. Docs will need an update to say it's the user's responsibility to update their firewall rules to block unwanted forwarding between non-Docker network interfaces.
Log a warning about that when enabling forwarding.
Log a warning when migrating from iptables to nftables when the iptables policy is DROP, because it'll drop packets that have been accepted by nftables rules (so, for example, published ports won't work).
- How I did it
The first two commits are tidy-up - only nftabler needs an iptables cleaner, and only the iptabler (now) needs a method to set the filter-FORWARD policy. So, use those types directly in the bridge driver when needed.
The third commit drops the policy-setting from nftables and updates tests.
The final commit adds a warning about the iptables policy on migration to nftables.
- How to verify it
Start Docker with IP forwarding disabled and --firewall-backend=iptables - check the filter-FORWARD policies are DROP.
Start Docker again with --firewall-backend=nftables, check logs for a warning about the iptables policy.
Disable IP forwarding, restart with nftables, check for a warning about the firewall rules.
And, updated tests.
- Human readable description for the release notes
- nftables: Docker will enable IP forwarding on the host, but it's the user's responsibility to modify the host's firewall rules to block forwarding between non-Docker interfaces if necessary.