Look at Content-Encoding to determine gzip status for esi subrequests

to handle correctly use of the "gunzip" filter at esi_level > 0

Fixes #3529

bin/varnishd/cache/cache_esi_deliver.c

@@ -844,7 +844,8 @@ static const struct vdp ved_ved = {
 static void v_matchproto_(vtr_deliver_f)
 ved_deliver(struct req *req, struct boc *boc, int wantbody)
 {
-	int i;
+	int i = 0;
+	const char *p;
 	struct ecx *ecx;
 	struct ved_foo foo[1];
 
@@ -860,7 +861,11 @@ ved_deliver(struct req *req, struct boc *boc, int wantbody)
 	if (boc == NULL && ObjGetLen(req->wrk, req->objcore) == 0)
 		return;
 
-	i = ObjCheckFlag(req->wrk, req->objcore, OF_GZIPED);
+	if (http_GetHdr(req->resp, H_Content_Encoding, &p))
+		i = !strcasecmp(p, "gzip");
+	if (i)
+		i = ObjCheckFlag(req->wrk, req->objcore, OF_GZIPED);
+
 	if (ecx->isgzip && i && !(req->res_mode & RES_ESI)) {
 		/* A gzip'ed include which is not ESI processed */
 

bin/varnishtest/tests/e00026.vtc

@@ -25,13 +25,30 @@ server s1 {
 	expect req.http.accept-encoding == gzip
 	txresp -gzipbody {<esi:include src="/foo"/>}
 
+	rxreq
+	expect req.url == "/5"
+	expect req.http.accept-encoding == gzip
+	txresp -gzipbody {<esi:include src="/bar"/>}
+
+	rxreq
+	expect req.url == "/bar"
+	txresp -bodylen 500
 } -start
 
 varnish v1 -vcl+backend {
 	sub vcl_backend_response {
-		if (bereq.url != "/foo") {
+		if (bereq.url ~ "^/.$") {
 			set beresp.do_esi = true;
+		} else
+		if (bereq.url ~ "/bar") {
+			set beresp.do_gzip = true;
+		}
+	}
+	sub vcl_deliver {
+		if (req.esi_level > 0 && req.http.r3529) {
+			unset req.http.Accept-Encoding;
 		}
+		set resp.http.filters = resp.filters;
 	}
 } -start
 
@@ -74,6 +91,12 @@ client c1 {
 	expect resp.status == 200
 	expect resp.bodylen == 13
 
+	txreq -url /5 -hdr "Accept-Encoding: gzip" -hdr "r3529: 1"
+	rxresp
+	expect resp.http.content-encoding == gzip
+	gunzip
+	expect resp.status == 200
+	expect resp.bodylen == 500
 }
 
 client c1 -run