Merge commit from fork

Instead of casting lease ID to uint32, fix the TTL() function
to use etcd time-to-live API for determining TTL. Add configurable
min-lease-ttl and max-lease-ttl options to prevent extreme TTL
values. By default, lease records now go through bounds checking
with 30s to 1d as the min/max.

Added unit tests for validation and docs.

Signed-off-by: Ville Vesilehto <ville@vesilehto.fi>

plugin/etcd/setup.go

@@ -2,7 +2,11 @@ package etcd
 
 import (
 	"crypto/tls"
+	"errors"
 	"path/filepath"
+	"strconv"
+	"strings"
+	"time"
 
 	"github.com/coredns/caddy"
 	"github.com/coredns/coredns/core/dnsserver"
@@ -33,7 +37,11 @@ func setup(c *caddy.Controller) error {
 
 func etcdParse(c *caddy.Controller) (*Etcd, error) {
 	config := dnsserver.GetConfig(c)
-	etc := Etcd{PathPrefix: "skydns"}
+	etc := Etcd{
+		PathPrefix:  "skydns",
+		MinLeaseTTL: defaultLeaseMinTTL,
+		MaxLeaseTTL: defaultLeaseMaxTTL,
+	}
 	var (
 		tlsConfig *tls.Config
 		err       error
@@ -88,6 +96,24 @@ func etcdParse(c *caddy.Controller) (*Etcd, error) {
 					return &Etcd{}, c.Errf("credentials requires 2 arguments, username and password")
 				}
 				username, password = args[0], args[1]
+			case "min-lease-ttl":
+				if !c.NextArg() {
+					return &Etcd{}, c.ArgErr()
+				}
+				minLeaseTTL, err := parseTTL(c.Val())
+				if err != nil {
+					return &Etcd{}, c.Errf("invalid min-lease-ttl value: %v", err)
+				}
+				etc.MinLeaseTTL = minLeaseTTL
+			case "max-lease-ttl":
+				if !c.NextArg() {
+					return &Etcd{}, c.ArgErr()
+				}
+				maxLeaseTTL, err := parseTTL(c.Val())
+				if err != nil {
+					return &Etcd{}, c.Errf("invalid max-lease-ttl value: %v", err)
+				}
+				etc.MaxLeaseTTL = maxLeaseTTL
 			default:
 				if c.Val() != "}" {
 					return &Etcd{}, c.Errf("unknown property '%s'", c.Val())
@@ -124,3 +150,35 @@ func newEtcdClient(endpoints []string, cc *tls.Config, username, password string
 }
 
 const defaultEndpoint = "http://localhost:2379"
+
+// parseTTL parses a TTL value with flexible time units using Go's standard duration parsing.
+// Supports formats like: "30", "30s", "5m", "1h", "90s", "2h30m", etc.
+func parseTTL(s string) (uint32, error) {
+	s = strings.TrimSpace(s)
+	if s == "" {
+		return 0, nil
+	}
+
+	// Handle plain numbers (assume seconds)
+	if _, err := strconv.ParseUint(s, 10, 64); err == nil {
+		// If it's just a number, append "s" for seconds
+		s += "s"
+	}
+
+	// Use Go's standard time.ParseDuration for robust parsing
+	duration, err := time.ParseDuration(s)
+	if err != nil {
+		return 0, errors.New("invalid TTL format, use format like '30', '30s', '5m', '1h', or '2h30m'")
+	}
+
+	// Convert to seconds and check bounds
+	seconds := duration.Seconds()
+	if seconds < 0 {
+		return 0, errors.New("TTL must be non-negative")
+	}
+	if seconds > 4294967295 { // uint32 max value
+		return 0, errors.New("TTL too large, maximum is 4294967295 seconds")
+	}
+
+	return uint32(seconds), nil
+}