Bug report

Background

Some command line arguments are SliceSlice type, e.g. the log driver option (--log-driver).

There are 3 (or more?) methods to configure these parameters:

1. via configmap (the default way)
2. via environment variable
3. via command line

Cilium-agent will dump the effective configurations at start, like the following:

level=info msg="Skipped reading configuration file" reason="Config File \"ciliumd\" Not Found in \"[/home/xxx]\"" subsys=daemon
level=info msg="  --access-log=''" subsys=daemon
level=info msg="  --agent-labels=''" subsys=daemon
level=info msg="  --allow-icmp-frag-needed='true'" subsys=daemon
level=info msg="  --allow-localhost='auto'" subsys=daemon
level=info msg="  --annotate-k8s-node='true'" subsys=daemon
level=info msg="  --auto-create-cilium-node-resource='true'" subsys=daemon
level=info msg="  --auto-direct-node-routes='false'" subsys=daemon
level=info msg="  --blacklist-conflicting-routes='true'" subsys=daemon
level=info msg="  --bpf-compile-debug='false'" subsys=daemon
...

Problem

When using the 3rd way, namely, via command line interface, the specified driver will always be empty in dumped message:

$ ./daemon/cilium-agent --kvstore=etcd --log-driver=syslog 2>&1 | grep log-driver
level=info msg="  --log-driver=''" subsys=daemon

The first 2 ways (configmap and env) are OK:

$ cat configmap/log-driver
syslog
$ ./daemon/cilium-agent --kvstore=etcd --config-dir=./configmap 2>&1 | grep log-driver
level=info msg="  --log-driver='syslog'" subsys=daemon

$ CILIUM_LOG_DRIVER=syslog ./daemon/cilium-agent --kvstore=etcd 2>&1 | grep log-driver
level=info msg="  --log-driver='syslog'" subsys=daemon

Other StringSlice CLI arguments also suffer from this.

The good new is that Cilium works correctly regardless of this, in other words, it's just a display problem.

General Information

• Cilium version: 1.7.4
• Kernel version: 4.14/4.19

Dig inside

Look into the code, the empty values are dumped from this line:
https://github.com/cilium/cilium/blob/v1.7.4/pkg/option/config.go#L873

	for _, k := range keys {
		entry.Infof("  --%s='%s'", k, viper.GetString(k))
	}

viper.GetString("log-driver") will return an empty string. As a quick test, i found
viper.GetStringSlice("log-driver") will return the correct value for these keys.

Further digging, the above GetString call stack actually encounted error in https://github.com/cilium/cilium/blob/v1.7.4/vendor/github.com/spf13/cast/caste.go#L799,
but the error message was silently disgarded, just returned an empty string in https://github.com/cilium/cilium/blob/v1.7.4/vendor/github.com/spf13/cast/cast.go#L157:

func ToStringSlice(i interface{}) []string {
	v, _ := ToStringSliceE(i)
	return v
}

With some searches, it seems related to this issue in viper/cobra.