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| 1 | +// +build darwin |
| 2 | + |
| 3 | +package config |
| 4 | + |
| 5 | +import ( |
| 6 | + "bytes" |
| 7 | + "fmt" |
| 8 | + "net" |
| 9 | + "os/exec" |
| 10 | + "regexp" |
| 11 | + "strconv" |
| 12 | + "strings" |
| 13 | + |
| 14 | + "github.com/miekg/dns" |
| 15 | +) |
| 16 | + |
| 17 | +// scutilResolver represents a parsed resolver from scutil --dns output |
| 18 | +type scutilResolver struct { |
| 19 | + number int |
| 20 | + nameservers []string |
| 21 | + domain string |
| 22 | + searchDomains []string |
| 23 | + options []string |
| 24 | + ifIndex string |
| 25 | + flags string |
| 26 | +} |
| 27 | + |
| 28 | +// GetDefaultServers retrieves DNS configuration from macOS SystemConfiguration |
| 29 | +// by parsing the output of 'scutil --dns'. Falls back to /etc/resolv.conf on failure. |
| 30 | +func GetDefaultServers() ([]string, int, []string, error) { |
| 31 | + // Try scutil first |
| 32 | + resolvers, ndots, search, err := getResolversFromScutil() |
| 33 | + if err != nil { |
| 34 | + // Fallback to /etc/resolv.conf |
| 35 | + return fallbackToResolvConf() |
| 36 | + } |
| 37 | + |
| 38 | + return resolvers, ndots, search, nil |
| 39 | +} |
| 40 | + |
| 41 | +// getResolversFromScutil executes scutil --dns and parses the output |
| 42 | +func getResolversFromScutil() ([]string, int, []string, error) { |
| 43 | + // Execute scutil --dns |
| 44 | + cmd := exec.Command("scutil", "--dns") |
| 45 | + var stdout, stderr bytes.Buffer |
| 46 | + cmd.Stdout = &stdout |
| 47 | + cmd.Stderr = &stderr |
| 48 | + |
| 49 | + if err := cmd.Run(); err != nil { |
| 50 | + return nil, 0, nil, fmt.Errorf("scutil execution failed: %w", err) |
| 51 | + } |
| 52 | + |
| 53 | + output := stdout.String() |
| 54 | + if len(strings.TrimSpace(output)) == 0 { |
| 55 | + return nil, 0, nil, fmt.Errorf("scutil returned empty output") |
| 56 | + } |
| 57 | + |
| 58 | + // Parse the output |
| 59 | + resolvers, err := parseScutilOutput(output) |
| 60 | + if err != nil { |
| 61 | + return nil, 0, nil, fmt.Errorf("failed to parse scutil output: %w", err) |
| 62 | + } |
| 63 | + |
| 64 | + // Filter out mDNS resolvers |
| 65 | + validResolvers := make([]scutilResolver, 0) |
| 66 | + for _, r := range resolvers { |
| 67 | + if !isMDNS(r) && len(r.nameservers) > 0 { |
| 68 | + validResolvers = append(validResolvers, r) |
| 69 | + } |
| 70 | + } |
| 71 | + |
| 72 | + if len(validResolvers) == 0 { |
| 73 | + return nil, 0, nil, fmt.Errorf("no valid resolvers found") |
| 74 | + } |
| 75 | + |
| 76 | + // Aggregate nameservers from all valid resolvers |
| 77 | + // This allows the "internal" strategy to find domain-specific corporate DNS servers |
| 78 | + nameservers := make([]string, 0) |
| 79 | + seen := make(map[string]bool) |
| 80 | + |
| 81 | + for _, resolver := range validResolvers { |
| 82 | + for _, ns := range resolver.nameservers { |
| 83 | + ip := net.ParseIP(ns) |
| 84 | + // Skip link-local and duplicates |
| 85 | + if isUnicastLinkLocal(ip) || seen[ns] { |
| 86 | + continue |
| 87 | + } |
| 88 | + nameservers = append(nameservers, ns) |
| 89 | + seen[ns] = true |
| 90 | + } |
| 91 | + } |
| 92 | + |
| 93 | + // Aggregate search domains from all valid resolvers |
| 94 | + searchDomains := aggregateSearchDomains(validResolvers) |
| 95 | + |
| 96 | + // ndots: try to read from /etc/resolv.conf, default to 1 |
| 97 | + ndots := 1 |
| 98 | + if cfg, err := dns.ClientConfigFromFile("/etc/resolv.conf"); err == nil { |
| 99 | + ndots = cfg.Ndots |
| 100 | + } |
| 101 | + |
| 102 | + return nameservers, ndots, searchDomains, nil |
| 103 | +} |
| 104 | + |
| 105 | +// parseScutilOutput parses the output of scutil --dns |
| 106 | +func parseScutilOutput(output string) ([]scutilResolver, error) { |
| 107 | + lines := strings.Split(output, "\n") |
| 108 | + resolvers := make([]scutilResolver, 0) |
| 109 | + |
| 110 | + var current *scutilResolver |
| 111 | + resolverRe := regexp.MustCompile(`^resolver #(\d+)`) |
| 112 | + nameserverRe := regexp.MustCompile(`^\s+nameserver\[\d+\]\s*:\s*(.+)`) |
| 113 | + domainRe := regexp.MustCompile(`^\s+domain\s*:\s*(.+)`) |
| 114 | + searchDomainRe := regexp.MustCompile(`^\s+search domain\[\d+\]\s*:\s*(.+)`) |
| 115 | + optionsRe := regexp.MustCompile(`^\s+options\s*:\s*(.+)`) |
| 116 | + |
| 117 | + for _, line := range lines { |
| 118 | + // Check for resolver start |
| 119 | + if matches := resolverRe.FindStringSubmatch(line); matches != nil { |
| 120 | + if current != nil { |
| 121 | + resolvers = append(resolvers, *current) |
| 122 | + } |
| 123 | + num, _ := strconv.Atoi(matches[1]) |
| 124 | + current = &scutilResolver{ |
| 125 | + number: num, |
| 126 | + nameservers: make([]string, 0), |
| 127 | + searchDomains: make([]string, 0), |
| 128 | + options: make([]string, 0), |
| 129 | + } |
| 130 | + continue |
| 131 | + } |
| 132 | + |
| 133 | + if current == nil { |
| 134 | + continue |
| 135 | + } |
| 136 | + |
| 137 | + // Parse nameserver |
| 138 | + if matches := nameserverRe.FindStringSubmatch(line); matches != nil { |
| 139 | + current.nameservers = append(current.nameservers, strings.TrimSpace(matches[1])) |
| 140 | + continue |
| 141 | + } |
| 142 | + |
| 143 | + // Parse domain |
| 144 | + if matches := domainRe.FindStringSubmatch(line); matches != nil { |
| 145 | + current.domain = strings.TrimSpace(matches[1]) |
| 146 | + continue |
| 147 | + } |
| 148 | + |
| 149 | + // Parse search domain |
| 150 | + if matches := searchDomainRe.FindStringSubmatch(line); matches != nil { |
| 151 | + current.searchDomains = append(current.searchDomains, strings.TrimSpace(matches[1])) |
| 152 | + continue |
| 153 | + } |
| 154 | + |
| 155 | + // Parse options |
| 156 | + if matches := optionsRe.FindStringSubmatch(line); matches != nil { |
| 157 | + opts := strings.Fields(strings.TrimSpace(matches[1])) |
| 158 | + current.options = append(current.options, opts...) |
| 159 | + continue |
| 160 | + } |
| 161 | + } |
| 162 | + |
| 163 | + // Don't forget the last resolver |
| 164 | + if current != nil { |
| 165 | + resolvers = append(resolvers, *current) |
| 166 | + } |
| 167 | + |
| 168 | + return resolvers, nil |
| 169 | +} |
| 170 | + |
| 171 | +// isMDNS checks if a resolver is for mDNS (.local) |
| 172 | +func isMDNS(r scutilResolver) bool { |
| 173 | + for _, opt := range r.options { |
| 174 | + if opt == "mdns" { |
| 175 | + return true |
| 176 | + } |
| 177 | + } |
| 178 | + return false |
| 179 | +} |
| 180 | + |
| 181 | +// aggregateSearchDomains collects search domains from all resolvers |
| 182 | +func aggregateSearchDomains(resolvers []scutilResolver) []string { |
| 183 | + seen := make(map[string]bool) |
| 184 | + result := make([]string, 0) |
| 185 | + |
| 186 | + for _, r := range resolvers { |
| 187 | + // Add domain if present |
| 188 | + if r.domain != "" && !seen[r.domain] { |
| 189 | + result = append(result, r.domain) |
| 190 | + seen[r.domain] = true |
| 191 | + } |
| 192 | + |
| 193 | + // Add search domains |
| 194 | + for _, sd := range r.searchDomains { |
| 195 | + if !seen[sd] { |
| 196 | + result = append(result, sd) |
| 197 | + seen[sd] = true |
| 198 | + } |
| 199 | + } |
| 200 | + } |
| 201 | + |
| 202 | + return result |
| 203 | +} |
| 204 | + |
| 205 | +// fallbackToResolvConf falls back to the traditional /etc/resolv.conf |
| 206 | +func fallbackToResolvConf() ([]string, int, []string, error) { |
| 207 | + cfg, err := dns.ClientConfigFromFile("/etc/resolv.conf") |
| 208 | + if err != nil { |
| 209 | + return nil, 0, nil, err |
| 210 | + } |
| 211 | + |
| 212 | + servers := make([]string, 0) |
| 213 | + for _, server := range cfg.Servers { |
| 214 | + ip := net.ParseIP(server) |
| 215 | + if isUnicastLinkLocal(ip) { |
| 216 | + continue |
| 217 | + } |
| 218 | + servers = append(servers, server) |
| 219 | + } |
| 220 | + |
| 221 | + return servers, cfg.Ndots, cfg.Search, nil |
| 222 | +} |
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