Source file
src/net/dnsconfig_unix.go
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8
9 package net
10
11 import (
12 "internal/bytealg"
13 "time"
14 )
15
16
17 func dnsReadConfig(filename string) *dnsConfig {
18 conf := &dnsConfig{
19 ndots: 1,
20 timeout: 5 * time.Second,
21 attempts: 2,
22 }
23 file, err := open(filename)
24 if err != nil {
25 conf.servers = defaultNS
26 conf.search = dnsDefaultSearch()
27 conf.err = err
28 return conf
29 }
30 defer file.close()
31 if fi, err := file.file.Stat(); err == nil {
32 conf.mtime = fi.ModTime()
33 } else {
34 conf.servers = defaultNS
35 conf.search = dnsDefaultSearch()
36 conf.err = err
37 return conf
38 }
39 for line, ok := file.readLine(); ok; line, ok = file.readLine() {
40 if len(line) > 0 && (line[0] == ';' || line[0] == '#') {
41
42 continue
43 }
44 f := getFields(line)
45 if len(f) < 1 {
46 continue
47 }
48 switch f[0] {
49 case "nameserver":
50 if len(f) > 1 && len(conf.servers) < 3 {
51
52
53
54 if parseIPv4(f[1]) != nil {
55 conf.servers = append(conf.servers, JoinHostPort(f[1], "53"))
56 } else if ip, _ := parseIPv6Zone(f[1]); ip != nil {
57 conf.servers = append(conf.servers, JoinHostPort(f[1], "53"))
58 }
59 }
60
61 case "domain":
62 if len(f) > 1 {
63 conf.search = []string{ensureRooted(f[1])}
64 }
65
66 case "search":
67 conf.search = make([]string, 0, len(f)-1)
68 for i := 1; i < len(f); i++ {
69 name := ensureRooted(f[i])
70 if name == "." {
71 continue
72 }
73 conf.search = append(conf.search, name)
74 }
75
76 case "options":
77 for _, s := range f[1:] {
78 switch {
79 case hasPrefix(s, "ndots:"):
80 n, _, _ := dtoi(s[6:])
81 if n < 0 {
82 n = 0
83 } else if n > 15 {
84 n = 15
85 }
86 conf.ndots = n
87 case hasPrefix(s, "timeout:"):
88 n, _, _ := dtoi(s[8:])
89 if n < 1 {
90 n = 1
91 }
92 conf.timeout = time.Duration(n) * time.Second
93 case hasPrefix(s, "attempts:"):
94 n, _, _ := dtoi(s[9:])
95 if n < 1 {
96 n = 1
97 }
98 conf.attempts = n
99 case s == "rotate":
100 conf.rotate = true
101 case s == "single-request" || s == "single-request-reopen":
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106
107 conf.singleRequest = true
108 case s == "use-vc" || s == "usevc" || s == "tcp":
109
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113
114
115 conf.useTCP = true
116 case s == "trust-ad":
117 conf.trustAD = true
118 case s == "edns0":
119
120
121 case s == "no-reload":
122 conf.noReload = true
123 default:
124 conf.unknownOpt = true
125 }
126 }
127
128 case "lookup":
129
130
131
132 conf.lookup = f[1:]
133
134 default:
135 conf.unknownOpt = true
136 }
137 }
138 if len(conf.servers) == 0 {
139 conf.servers = defaultNS
140 }
141 if len(conf.search) == 0 {
142 conf.search = dnsDefaultSearch()
143 }
144 return conf
145 }
146
147 func dnsDefaultSearch() []string {
148 hn, err := getHostname()
149 if err != nil {
150
151 return nil
152 }
153 if i := bytealg.IndexByteString(hn, '.'); i >= 0 && i < len(hn)-1 {
154 return []string{ensureRooted(hn[i+1:])}
155 }
156 return nil
157 }
158
159 func hasPrefix(s, prefix string) bool {
160 return len(s) >= len(prefix) && s[:len(prefix)] == prefix
161 }
162
163 func ensureRooted(s string) string {
164 if len(s) > 0 && s[len(s)-1] == '.' {
165 return s
166 }
167 return s + "."
168 }
169
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