Description of problem

Fail to run shim v2 with bridged network, network use cnm mode.

# pouch run  -d --runtime=kata-runtime docker.io/library/busybox:latest
Error: failed to run container de3522: {"message":"failed to create container(de35222f6e3c4288be95e8b78ddfd82ed71f5457093c9ed3bc3a0ac497330d2f) on containerd: failed to create task for container(de35222f6e3c4288be95e8b78ddfd82ed71f5457093c9ed3bc3a0ac497330d2f): exit status 1: stdout: , stderr: time=\"2019-06-12T15:47:20+08:00\" level=info msg=\"external key /proc/14245/ns/net\" \ntime=\"2019-06-12T15:47:20+08:00\" level=fatal msg=\"failed to add interface vethf6bce45 to sandbox: error renaming interface \"vethf6bce45\" to \"eth0\": file exists\" \n: unknown"}

From read libnetwork/kata code, and with help of @lifupan , finally I found the reason:

1. kata create a new netns
2. with EnterNS, kata change netns to the created one.
3. when use cnm network mode, in pre-start hook, kata will re-exec libnetwork process libnetwork-setkey, and send self pid to it. libnetwork use /proc/pid/ns/net to find the netns kata use , and set veth into the netns

v1/v2 shim use the same way to create network, v1 can successful because EnterNS changed both current thread and main thread 's netns. But use v2 shim , only changed current thread netns, main thread still use host netns, so it fails. So if we pass syscall.Gettid() to libnetwork, it will work.

Expected result

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Actual result

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