Fix panic when parsing resolv.conf

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

@@ -2,6 +2,7 @@ package dns
 
 import (
 	"bufio"
+	"io"
 	"os"
 	"strconv"
 	"strings"
@@ -25,8 +26,13 @@ func ClientConfigFromFile(resolvconf string) (*ClientConfig, error) {
 		return nil, err
 	}
 	defer file.Close()
+	return ClientConfigFromReader(file)
+}
+
+// ClientConfigFromReader works like ClientConfigFromFile but takes an io.Reader as argument
+func ClientConfigFromReader(resolvconf io.Reader) (*ClientConfig, error) {
 	c := new(ClientConfig)
-	scanner := bufio.NewScanner(file)
+	scanner := bufio.NewScanner(resolvconf)
 	c.Servers = make([]string, 0)
 	c.Search = make([]string, 0)
 	c.Port = "53"
@@ -73,8 +79,10 @@ func ClientConfigFromFile(resolvconf string) (*ClientConfig, error) {
 				switch {
 				case len(s) >= 6 && s[:6] == "ndots:":
 					n, _ := strconv.Atoi(s[6:])
-					if n < 1 {
-						n = 1
+					if n < 0 {
+						n = 0
+					} else if n > 15 {
+						n = 15
 					}
 					c.Ndots = n
 				case len(s) >= 8 && s[:8] == "timeout:":
@@ -83,7 +91,7 @@ func ClientConfigFromFile(resolvconf string) (*ClientConfig, error) {
 						n = 1
 					}
 					c.Timeout = n
-				case len(s) >= 8 && s[:9] == "attempts:":
+				case len(s) >= 9 && s[:9] == "attempts:":
 					n, _ := strconv.Atoi(s[9:])
 					if n < 1 {
 						n = 1
@@ -97,3 +105,35 @@ func ClientConfigFromFile(resolvconf string) (*ClientConfig, error) {
 	}
 	return c, nil
 }
+
+// NameList returns all of the names that should be queried based on the
+// config. It is based off of go's net/dns name building, but it does not
+// check the length of the resulting names.
+func (c *ClientConfig) NameList(name string) []string {
+	// if this domain is already fully qualified, no append needed.
+	if IsFqdn(name) {
+		return []string{name}
+	}
+
+	// Check to see if the name has more labels than Ndots. Do this before making
+	// the domain fully qualified.
+	hasNdots := CountLabel(name) > c.Ndots
+	// Make the domain fully qualified.
+	name = Fqdn(name)
+
+	// Make a list of names based off search.
+	names := []string{}
+
+	// If name has enough dots, try that first.
+	if hasNdots {
+		names = append(names, name)
+	}
+	for _, s := range c.Search {
+		names = append(names, Fqdn(name+s))
+	}
+	// If we didn't have enough dots, try after suffixes.
+	if !hasNdots {
+		names = append(names, name)
+	}
+	return names
+}