vendor/github.com/miekg/dns/clientconfig.go

   1 package dns
   2
   3 import (
   4         "bufio"
   5         "os"
   6         "strconv"
   7         "strings"
   8 )
   9
  10 // ClientConfig wraps the contents of the /etc/resolv.conf file.
  11 type ClientConfig struct {
  12         Servers  []string // servers to use
  13         Search   []string // suffixes to append to local name
  14         Port     string   // what port to use
  15         Ndots    int      // number of dots in name to trigger absolute lookup
  16         Timeout  int      // seconds before giving up on packet
  17         Attempts int      // lost packets before giving up on server, not used in the package dns
  18 }
  19
  20 // ClientConfigFromFile parses a resolv.conf(5) like file and returns
  21 // a *ClientConfig.
  22 func ClientConfigFromFile(resolvconf string) (*ClientConfig, error) {
  23         file, err := os.Open(resolvconf)
  24         if err != nil {
  25                 return nil, err
  26         }
  27         defer file.Close()
  28         c := new(ClientConfig)
  29         scanner := bufio.NewScanner(file)
  30         c.Servers = make([]string, 0)
  31         c.Search = make([]string, 0)
  32         c.Port = "53"
  33         c.Ndots = 1
  34         c.Timeout = 5
  35         c.Attempts = 2
  36
  37         for scanner.Scan() {
  38                 if err := scanner.Err(); err != nil {
  39                         return nil, err
  40                 }
  41                 line := scanner.Text()
  42                 f := strings.Fields(line)
  43                 if len(f) < 1 {
  44                         continue
  45                 }
  46                 switch f[0] {
  47                 case "nameserver": // add one name server
  48                         if len(f) > 1 {
  49                                 // One more check: make sure server name is
  50                                 // just an IP address.  Otherwise we need DNS
  51                                 // to look it up.
  52                                 name := f[1]
  53                                 c.Servers = append(c.Servers, name)
  54                         }
  55
  56                 case "domain": // set search path to just this domain
  57                         if len(f) > 1 {
  58                                 c.Search = make([]string, 1)
  59                                 c.Search[0] = f[1]
  60                         } else {
  61                                 c.Search = make([]string, 0)
  62                         }
  63
  64                 case "search": // set search path to given servers
  65                         c.Search = make([]string, len(f)-1)
  66                         for i := 0; i < len(c.Search); i++ {
  67                                 c.Search[i] = f[i+1]
  68                         }
  69
  70                 case "options": // magic options
  71                         for i := 1; i < len(f); i++ {
  72                                 s := f[i]
  73                                 switch {
  74                                 case len(s) >= 6 && s[:6] == "ndots:":
  75                                         n, _ := strconv.Atoi(s[6:])
  76                                         if n < 1 {
  77                                                 n = 1
  78                                         }
  79                                         c.Ndots = n
  80                                 case len(s) >= 8 && s[:8] == "timeout:":
  81                                         n, _ := strconv.Atoi(s[8:])
  82                                         if n < 1 {
  83                                                 n = 1
  84                                         }
  85                                         c.Timeout = n
  86                                 case len(s) >= 8 && s[:9] == "attempts:":
  87                                         n, _ := strconv.Atoi(s[9:])
  88                                         if n < 1 {
  89                                                 n = 1
  90                                         }
  91                                         c.Attempts = n
  92                                 case s == "rotate":
  93                                         /* not imp */
  94                                 }
  95                         }
  96                 }
  97         }
  98         return c, nil
  99 }