When we get a bogus reply from a backend, for instance with too many

headers, we need to purge all traces of it, before we construct our
503 response, otherwise we risk failing to set important headers,
such as "Connection: close".

Fixes #416
(again)

bin/varnishd/cache/cache_fetch.c

@@ -137,6 +137,22 @@ vbf_stp_startfetch(struct worker *wrk, struct busyobj *bo)
 	return (F_STP_FETCHHDR);
 }
 
+/*--------------------------------------------------------------------
+ */
+
+static void
+make_it_503(struct busyobj *bo)
+{
+
+	HTTP_Setup(bo->beresp, bo->ws, bo->vsl, HTTP_Beresp);
+	bo->err_code = 503;
+	http_SetH(bo->beresp, HTTP_HDR_PROTO, "HTTP/1.1");
+	http_SetResp(bo->beresp,
+	    "HTTP/1.1", 503, "Backend fetch failed");
+	http_SetHeader(bo->beresp, "Content-Length: 0");
+	http_SetHeader(bo->beresp, "Connection: close");
+}
+
 /*--------------------------------------------------------------------
  */
 
@@ -175,12 +191,7 @@ vbf_stp_fetchhdr(struct worker *wrk, struct busyobj *bo)
 
 	if (i) {
 		AZ(bo->vbc);
-		bo->err_code = 503;
-		http_SetH(bo->beresp, HTTP_HDR_PROTO, "HTTP/1.1");
-		http_SetResp(bo->beresp,
-		    "HTTP/1.1", 503, "Backend fetch failed");
-		http_SetHeader(bo->beresp, "Content-Length: 0");
-		http_SetHeader(bo->beresp, "Connection: close");
+		make_it_503(bo);
 	} else {
 		AN(bo->vbc);
 	}