cni: fix regression in falling back to DNS owned by dockerd
#20189
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In #20007 we fixed a bug where the DNS configuration set by CNI plugins was not threaded through to the task configuration. This resulted in a regression where a DNS override set by `dockerd` was not respected for `bridge` mode networking. Our existing handling of CNI DNS incorrectly assumed that the DNS field would be empty, when in fact it contains a single empty DNS struct. Handle this case correctly by checking whether the DNS struct we get back from CNI has any nameservers, and ignore it if it doesn't. Expand test coverage of this case. Fixes: #20174
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| // Use the first DNS results. | ||
| // Use the first DNS results, if non-empty |
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Maybe not the best place for this, but it may be useful to have a place listing the multitude of possibilities for DNS config sources 😅
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Yeah agreed... we're missing a DNS section of our Networking docs. That'd be a good place to describe how all that works. Once I've made some more progress on tproxy DNS I'll see about whipping that up.
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In #20007 we fixed a bug where the DNS configuration set by CNI plugins was not threaded through to the task configuration. This resulted in a regression where a DNS override set by `dockerd` was not respected for `bridge` mode networking. Our existing handling of CNI DNS incorrectly assumed that the DNS field would be empty, when in fact it contains a single empty DNS struct. Handle this case correctly by checking whether the DNS struct we get back from CNI has any nameservers, and ignore it if it doesn't. Expand test coverage of this case. Fixes: #20174
tgross
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In #20007 we fixed a bug where the DNS configuration set by CNI plugins was not threaded through to the task configuration. This resulted in a regression where a DNS override set by `dockerd` was not respected for `bridge` mode networking. Our existing handling of CNI DNS incorrectly assumed that the DNS field would be empty, when in fact it contains a single empty DNS struct. Handle this case correctly by checking whether the DNS struct we get back from CNI has any nameservers, and ignore it if it doesn't. Expand test coverage of this case. Fixes: #20174
philrenaud
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In #20007 we fixed a bug where the DNS configuration set by CNI plugins was not threaded through to the task configuration. This resulted in a regression where a DNS override set by `dockerd` was not respected for `bridge` mode networking. Our existing handling of CNI DNS incorrectly assumed that the DNS field would be empty, when in fact it contains a single empty DNS struct. Handle this case correctly by checking whether the DNS struct we get back from CNI has any nameservers, and ignore it if it doesn't. Expand test coverage of this case. Fixes: #20174
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In #20007 we fixed a bug where the DNS configuration set by CNI plugins was not threaded through to the task configuration. This resulted in a regression where a DNS override set by
dockerdwas not respected forbridgemode networking. Our existing handling of CNI DNS incorrectly assumed that the DNS field would be empty, when in fact it contains a single empty DNS struct.Handle this case correctly by checking whether the DNS struct we get back from CNI has any nameservers, and ignore it if it doesn't. Expand test coverage of this case.
Fixes: #20174
In addition to the unit tests here, I verified this works with the Docker DNS override. Using the default values for
dockerdand this patch, I get the following in a Nomad job usingmode="bridge"networking:And after setting an override of
--dns=8.8.8.8in mydocker.serviceunit, I get the following for the same job: