我正在尝试使用 kops 在 AWS 上安装 k8s。k8s 集群无法上线是因为 kube-dns 服务不断崩溃。日志：
I0111 19:21:30.189260 1 logs.go:41] skydns: ready for queries on cluster.local. for tcp://0.0.0.0:10053 [rcache 0]
I0111 19:21:30.189278 1 logs.go:41] skydns: ready for queries on cluster.local. for udp://0.0.0.0:10053 [rcache 0]
I0111 19:21:30.689342 1 dns.go:174] Waiting for services and endpoints to be initialized from apiserver...
...
E0111 19:22:00.189691 1 reflector.go:199] k8s.io/dns/vendor/k8s.io/client-go/tools/cache/reflector.go:94: Failed to list *v1.Endpoints: Get https://100.64.0.1:443/api/v1/endpoints?resourceVersion=0: dial tcp 100.64.0.1:443: i/o timeout
E0111 19:22:00.190016 1 reflector.go:199] k8s.io/dns/vendor/k8s.io/client-go/tools/cache/reflector.go:94: Failed to list *v1.Service: Get https://100.64.0.1:443/api/v1/services?resourceVersion=0: dial tcp 100.64.0.1:443: i/o timeout
所有用户 kube-system pod 都处于良好状态。主服务器上的 api-server 日志没有列出任何错误。问题可能是什么？