Support outgoing zone transfers

These can be enabled by adding "transfer out" to the Corefile. Without
it no AXFR is allowed.

For now only AXFR and no IXFR. No TSIG and no ACLs.

core/setup/file.go

@@ -32,7 +32,6 @@ func fileParse(c *Controller) (file.Zones, error) {
 
 			origin := c.ServerBlockHosts[c.ServerBlockHostIndex]
 			if c.NextArg() {
-				c.Next()
 				origin = c.Val()
 			}
 			// normalize this origin
@@ -42,12 +41,31 @@ func fileParse(c *Controller) (file.Zones, error) {
 			if err != nil {
 				return file.Zones{}, err
 			}
-
 			zone, err := file.Parse(reader, origin, fileName)
 			if err == nil {
 				z[origin] = zone
 			}
 			names = append(names, origin)
+			if c.NextBlock() {
+				what := c.Val()
+				if !c.NextArg() {
+					return file.Zones{}, c.ArgErr()
+				}
+				value := c.Val()
+				var err error
+				switch what {
+				case "transfer":
+					if value == "out" {
+						z[origin].Transfer.Out = true
+					}
+					if value == "in" {
+						z[origin].Transfer.In = true
+					}
+				}
+				if err != nil {
+					return file.Zones{}, err
+				}
+			}
 		}
 	}
 	return file.Zones{Z: z, Names: names}, nil