[master] 730e185 clarifying comments

[Nils Goroll]

commit 730e185aa1d808a9c3f9fccece6747158ba84d13
Author: Nils Goroll <nils.goroll at uplex.de>
Date:   Wed May 20 12:18:00 2015 +0200

    clarifying comments

diff --git a/bin/varnishd/cache/cache_rfc2616.c b/bin/varnishd/cache/cache_rfc2616.c
index d3ea762..df58054 100644
--- a/bin/varnishd/cache/cache_rfc2616.c
+++ b/bin/varnishd/cache/cache_rfc2616.c
@@ -113,7 +113,13 @@ RFC2616_Ttl(struct busyobj *bo, double now)
 		break;
 	case 302: /* Moved Temporarily */
 	case 307: /* Temporary Redirect */
-		expp->ttl = -1.;
+		/*
+		 * https://tools.ietf.org/html/rfc7231#section-6.1
+		 *
+		 * Do not apply the default ttl, only set a ttl if Cache-Control
+		 * or Expires are present. Uncacheable otherwise.
+		 */
+		expp->ttl = -1.;	/* fall through */
 	case 200: /* OK */
 	case 203: /* Non-Authoritative Information */
 	case 204: /* No Content */