1 files changed, 96 insertions, 0 deletions
diff --git a/src/net/dnsconfig_unix.go b/src/net/dnsconfig_unix.go
new file mode 100644
index 000000000..66ab7c4dd
--- /dev/null
+++ b/src/net/dnsconfig_unix.go
@@ -0,0 +1,96 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd linux netbsd openbsd solaris
+
+// Read system DNS config from /etc/resolv.conf
+
+package net
+
+type dnsConfig struct {
+	servers  []string // servers to use
+	search   []string // suffixes to append to local name
+	ndots    int      // number of dots in name to trigger absolute lookup
+	timeout  int      // seconds before giving up on packet
+	attempts int      // lost packets before giving up on server
+	rotate   bool     // round robin among servers
+}
+
+// See resolv.conf(5) on a Linux machine.
+// TODO(rsc): Supposed to call uname() and chop the beginning
+// of the host name to get the default search domain.
+func dnsReadConfig(filename string) (*dnsConfig, error) {
+	file, err := open(filename)
+	if err != nil {
+		return nil, &DNSConfigError{err}
+	}
+	defer file.close()
+	conf := &dnsConfig{
+		ndots:    1,
+		timeout:  5,
+		attempts: 2,
+	}
+	for line, ok := file.readLine(); ok; line, ok = file.readLine() {
+		f := getFields(line)
+		if len(f) < 1 {
+			continue
+		}
+		switch f[0] {
+		case "nameserver": // add one name server
+			if len(f) > 1 && len(conf.servers) < 3 { // small, but the standard limit
+				// One more check: make sure server name is
+				// just an IP address.  Otherwise we need DNS
+				// to look it up.
+				if parseIPv4(f[1]) != nil {
+					conf.servers = append(conf.servers, f[1])
+				} else if ip, _ := parseIPv6(f[1], true); ip != nil {
+					conf.servers = append(conf.servers, f[1])
+				}
+			}
+
+		case "domain": // set search path to just this domain
+			if len(f) > 1 {
+				conf.search = []string{f[1]}
+			}
+
+		case "search": // set search path to given servers
+			conf.search = make([]string, len(f)-1)
+			for i := 0; i < len(conf.search); i++ {
+				conf.search[i] = f[i+1]
+			}
+
+		case "options": // magic options
+			for i := 1; i < len(f); i++ {
+				s := f[i]
+				switch {
+				case hasPrefix(s, "ndots:"):
+					n, _, _ := dtoi(s, 6)
+					if n < 1 {
+						n = 1
+					}
+					conf.ndots = n
+				case hasPrefix(s, "timeout:"):
+					n, _, _ := dtoi(s, 8)
+					if n < 1 {
+						n = 1
+					}
+					conf.timeout = n
+				case hasPrefix(s, "attempts:"):
+					n, _, _ := dtoi(s, 9)
+					if n < 1 {
+						n = 1
+					}
+					conf.attempts = n
+				case s == "rotate":
+					conf.rotate = true
+				}
+			}
+		}
+	}
+	return conf, nil
+}
+
+func hasPrefix(s, prefix string) bool {
+	return len(s) >= len(prefix) && s[:len(prefix)] == prefix
+}