[6.0] a1cedd380 Guard against OA_GZIPBITS streaming race

[Reza Naghibi]

commit a1cedd380481f13c3468abcb2d35630372ffc6a8
Author: Reza Naghibi <reza at naghibi.com>
Date:   Wed Feb 13 10:45:40 2019 -0500

    Guard against OA_GZIPBITS streaming race

diff --git a/bin/varnishd/cache/cache_gzip.c b/bin/varnishd/cache/cache_gzip.c
index b325e79c5..732c8db62 100644
--- a/bin/varnishd/cache/cache_gzip.c
+++ b/bin/varnishd/cache/cache_gzip.c
@@ -292,6 +292,10 @@ vdp_gunzip_init(struct req *req, void **priv)
 	ssize_t dl;
 	uint64_t u;
 
+	CHECK_OBJ_NOTNULL(req, REQ_MAGIC);
+	CHECK_OBJ_NOTNULL(req->objcore, OBJCORE_MAGIC);
+	CHECK_OBJ_ORNULL(req->objcore->boc, BOC_MAGIC);
+
 	vg = VGZ_NewGunzip(req->vsl, "U D -");
 	AN(vg);
 	if (vgz_getmbuf(vg)) {
@@ -307,6 +311,10 @@ vdp_gunzip_init(struct req *req, void **priv)
 
 	req->resp_len = -1;
 
+	/* OA_GZIPBITS is not stable yet */
+	if (req->objcore->boc)
+		return (0);
+
 	p = ObjGetAttr(req->wrk, req->objcore, OA_GZIPBITS, &dl);
 	if (p != NULL && dl == 32) {
 		u = vbe64dec(p + 24);