etcdserver/server_access_control.go
func (ac *AccessController) IsHostWhitelisted(host string) bool {
	ac.hostWhitelistMu.RLock()
	defer ac.hostWhitelistMu.RUnlock()
	if len(ac.HostWhitelist) == 0 { // allow all
		return true
	}
	_, ok := ac.HostWhitelist["*"]
	if ok {
		return true
	}
	_, ok = ac.HostWhitelist[host]
	return ok
}
func (ac *AccessController) IsHostWhitelisted(host string) bool {
	ac.hostWhitelistMu.RLock()
	defer ac.hostWhitelistMu.RUnlock()
	if len(ac.HostWhitelist) == 0 { // allow all
		return true
	}
	_, ok := ac.HostWhitelist["*"]
	if ok {
		return true
	}
	_, ok = ac.HostWhitelist[host]
	return ok
}
// IsHostWhitelisted returns true if the host is whitelisted.
// If whitelist is empty, allow all.