Validate resolv.conf for presence of nameserver entries

Co-authored-by: Brad Davidson <brad@oatmail.org>
Signed-off-by: linxin <linxin@geedgenetworks.com>

pkg/agent/config/config.go

@@ -316,19 +316,22 @@ func isValidResolvConf(resolvConfFile string) bool {
 
  nameserver := regexp.MustCompile(`^nameserver\s+([^\s]*)`)
  scanner := bufio.NewScanner(file)
+ foundNameserver := false
  for scanner.Scan() {
  ipMatch := nameserver.FindStringSubmatch(scanner.Text())
  if len(ipMatch) == 2 {
  ip := net.ParseIP(ipMatch[1])
  if ip == nil || !ip.IsGlobalUnicast() {
  return false
+ } else {
+ foundNameserver = true
  }
  }
  }
  if err := scanner.Err(); err != nil {
  return false
  }
- return true
+ return foundNameserver
 }
 
 func locateOrGenerateResolvConf(envInfo *cmds.Agent) string {