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kvm: solve certain routing issues by using the same default bridge as CNI #3905
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When the kvm stage1 and the coreos stage1 are used on the same machine with a flannel CNI configuration (and likely other configurations) without a specified bridge name, different bridges will be constructed by each stage1 for the same subnet -- cni0 and kvm-cni0 -- causing traffic intended for the later-constructed bridge to be lost, as it is routed to the earlier-constructed bridge. The normal workaround is to specify a bridge name in the CNI configuration, but this fix avoids the issue altogether by making sure that cni0 is used in all cases.
jellonek
approved these changes
Feb 19, 2018
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/cc @squeed |
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LGTM! |
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When the kvm stage1 and the coreos stage1 are used on the same machine with a
flannel CNI configuration (and likely other configurations) without a specified
bridge name, different bridges will be constructed by each stage1 for the same
subnet -- cni0 and kvm-cni0 -- causing traffic intended for the
later-constructed bridge to be lost, as it is routed to the earlier-constructed
bridge.
The normal workaround is to specify a bridge name in the CNI configuration, but
this fix avoids the issue altogether by making sure that cni0 is used in all
cases.
I can't find any records of a specific motivation for using kvm-cni0 instead of cni0, so it's possible that I'm missing the original reason behind it, but it seems like an arbitrarily-made decision from the original development of CNI support in the kvm stage1.