plugin/hosts provide more configuration flexibility (#2535)

* plugin/hosts provide more configuration flexibility

This patch adds few features to the host plugin
 * no-reverse (both as first argument on the plugin line and inline)
   disable the automatic generation of reserve entries for hosts
 * ttl <duration> (inline only atm)
   allows to change the default ttl (default 5 minutes)
 * reload <duration> (inline only atm)
   allows to change the reloading interval (default 5s)

* plugin/hosts remove superfluous parameters to parse

plugin/hosts/setup.go

@@ -3,6 +3,7 @@ package hosts
 import (
 	"os"
 	"path/filepath"
+	"strconv"
 	"strings"
 	"time"
 
@@ -22,28 +23,37 @@ func init() {
 	})
 }
 
+func periodicHostsUpdate(h *Hosts) chan bool {
+	parseChan := make(chan bool)
+
+	if h.options.reload == durationOf0s {
+		return parseChan
+	}
+
+	go func() {
+		ticker := time.NewTicker(h.options.reload)
+		for {
+			select {
+			case <-parseChan:
+				return
+			case <-ticker.C:
+				h.readHosts()
+			}
+		}
+	}()
+	return parseChan
+}
+
 func setup(c *caddy.Controller) error {
 	h, err := hostsParse(c)
 	if err != nil {
 		return plugin.Error("hosts", err)
 	}
 
-	parseChan := make(chan bool)
+	parseChan := periodicHostsUpdate(&h)
 
 	c.OnStartup(func() error {
 		h.readHosts()
-
-		go func() {
-			ticker := time.NewTicker(5 * time.Second)
-			for {
-				select {
-				case <-parseChan:
-					return
-				case <-ticker.C:
-					h.readHosts()
-				}
-			}
-		}()
 		return nil
 	})
 
@@ -61,15 +71,18 @@ func setup(c *caddy.Controller) error {
 }
 
 func hostsParse(c *caddy.Controller) (Hosts, error) {
-	var h = Hosts{
+	config := dnsserver.GetConfig(c)
+
+	options := newOptions()
+
+	h := Hosts{
 		Hostsfile: &Hostsfile{
-			path: "/etc/hosts",
-			hmap: newHostsMap(),
+			path:    "/etc/hosts",
+			hmap:    newHostsMap(),
+			options: options,
 		},
 	}
 
-	config := dnsserver.GetConfig(c)
-
 	inline := []string{}
 	i := 0
 	for c.Next() {
@@ -79,6 +92,7 @@ func hostsParse(c *caddy.Controller) (Hosts, error) {
 		i++
 
 		args := c.RemainingArgs()
+
 		if len(args) >= 1 {
 			h.path = args[0]
 			args = args[1:]
@@ -114,6 +128,34 @@ func hostsParse(c *caddy.Controller) (Hosts, error) {
 			switch c.Val() {
 			case "fallthrough":
 				h.Fall.SetZonesFromArgs(c.RemainingArgs())
+			case "no_reverse":
+				options.autoReverse = false
+			case "ttl":
+				remaining := c.RemainingArgs()
+				if len(remaining) < 1 {
+					return h, c.Errf("ttl needs a time in second")
+				}
+				ttl, err := strconv.Atoi(remaining[0])
+				if err != nil {
+					return h, c.Errf("ttl needs a number of second")
+				}
+				if ttl <= 0 || ttl > 65535 {
+					return h, c.Errf("ttl provided is invalid")
+				}
+				options.ttl = uint32(ttl)
+			case "reload":
+				remaining := c.RemainingArgs()
+				if len(remaining) != 1 {
+					return h, c.Errf("reload needs a duration (zero seconds to disable)")
+				}
+				reload, err := time.ParseDuration(remaining[0])
+				if err != nil {
+					return h, c.Errf("invalid duration for reload '%s'", remaining[0])
+				}
+				if reload < durationOf0s {
+					return h, c.Errf("invalid negative duration for reload '%s'", remaining[0])
+				}
+				options.reload = reload
 			default:
 				if len(h.Fall.Zones) == 0 {
 					line := strings.Join(append([]string{c.Val()}, c.RemainingArgs()...), " ")