gtsocial-umbx

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clientconfig.go (3365B)

      1 package dns
      2 
      3 import (
      4 	"bufio"
      5 	"io"
      6 	"os"
      7 	"strconv"
      8 	"strings"
      9 )
     10 
     11 // ClientConfig wraps the contents of the /etc/resolv.conf file.
     12 type ClientConfig struct {
     13 	Servers  []string // servers to use
     14 	Search   []string // suffixes to append to local name
     15 	Port     string   // what port to use
     16 	Ndots    int      // number of dots in name to trigger absolute lookup
     17 	Timeout  int      // seconds before giving up on packet
     18 	Attempts int      // lost packets before giving up on server, not used in the package dns
     19 }
     20 
     21 // ClientConfigFromFile parses a resolv.conf(5) like file and returns
     22 // a *ClientConfig.
     23 func ClientConfigFromFile(resolvconf string) (*ClientConfig, error) {
     24 	file, err := os.Open(resolvconf)
     25 	if err != nil {
     26 		return nil, err
     27 	}
     28 	defer file.Close()
     29 	return ClientConfigFromReader(file)
     30 }
     31 
     32 // ClientConfigFromReader works like ClientConfigFromFile but takes an io.Reader as argument
     33 func ClientConfigFromReader(resolvconf io.Reader) (*ClientConfig, error) {
     34 	c := new(ClientConfig)
     35 	scanner := bufio.NewScanner(resolvconf)
     36 	c.Servers = make([]string, 0)
     37 	c.Search = make([]string, 0)
     38 	c.Port = "53"
     39 	c.Ndots = 1
     40 	c.Timeout = 5
     41 	c.Attempts = 2
     42 
     43 	for scanner.Scan() {
     44 		if err := scanner.Err(); err != nil {
     45 			return nil, err
     46 		}
     47 		line := scanner.Text()
     48 		f := strings.Fields(line)
     49 		if len(f) < 1 {
     50 			continue
     51 		}
     52 		switch f[0] {
     53 		case "nameserver": // add one name server
     54 			if len(f) > 1 {
     55 				// One more check: make sure server name is
     56 				// just an IP address.  Otherwise we need DNS
     57 				// to look it up.
     58 				name := f[1]
     59 				c.Servers = append(c.Servers, name)
     60 			}
     61 
     62 		case "domain": // set search path to just this domain
     63 			if len(f) > 1 {
     64 				c.Search = make([]string, 1)
     65 				c.Search[0] = f[1]
     66 			} else {
     67 				c.Search = make([]string, 0)
     68 			}
     69 
     70 		case "search": // set search path to given servers
     71 			c.Search = cloneSlice(f[1:])
     72 
     73 		case "options": // magic options
     74 			for _, s := range f[1:] {
     75 				switch {
     76 				case len(s) >= 6 && s[:6] == "ndots:":
     77 					n, _ := strconv.Atoi(s[6:])
     78 					if n < 0 {
     79 						n = 0
     80 					} else if n > 15 {
     81 						n = 15
     82 					}
     83 					c.Ndots = n
     84 				case len(s) >= 8 && s[:8] == "timeout:":
     85 					n, _ := strconv.Atoi(s[8:])
     86 					if n < 1 {
     87 						n = 1
     88 					}
     89 					c.Timeout = n
     90 				case len(s) >= 9 && s[:9] == "attempts:":
     91 					n, _ := strconv.Atoi(s[9:])
     92 					if n < 1 {
     93 						n = 1
     94 					}
     95 					c.Attempts = n
     96 				case s == "rotate":
     97 					/* not imp */
     98 				}
     99 			}
    100 		}
    101 	}
    102 	return c, nil
    103 }
    104 
    105 // NameList returns all of the names that should be queried based on the
    106 // config. It is based off of go's net/dns name building, but it does not
    107 // check the length of the resulting names.
    108 func (c *ClientConfig) NameList(name string) []string {
    109 	// if this domain is already fully qualified, no append needed.
    110 	if IsFqdn(name) {
    111 		return []string{name}
    112 	}
    113 
    114 	// Check to see if the name has more labels than Ndots. Do this before making
    115 	// the domain fully qualified.
    116 	hasNdots := CountLabel(name) > c.Ndots
    117 	// Make the domain fully qualified.
    118 	name = Fqdn(name)
    119 
    120 	// Make a list of names based off search.
    121 	names := []string{}
    122 
    123 	// If name has enough dots, try that first.
    124 	if hasNdots {
    125 		names = append(names, name)
    126 	}
    127 	for _, s := range c.Search {
    128 		names = append(names, Fqdn(name+s))
    129 	}
    130 	// If we didn't have enough dots, try after suffixes.
    131 	if !hasNdots {
    132 		names = append(names, name)
    133 	}
    134 	return names
    135 }