http2_hpack: Enforce http_req_hdr_len limit

Refs #3709

bin/varnishd/http2/cache_http2_hpack.c

@@ -161,7 +161,7 @@ h2h_addhdr(struct http *hp, struct h2h_decode *d)
 	disallow_empty = 0;
 	has_dup = 0;
 
-	if (Tlen(hdr) > UINT_MAX) {	/* XXX: cache_param max header size */
+	if (Tlen(hdr) > cache_param->http_req_hdr_len) {
 		VSLb(hp->vsl, SLT_BogoHeader, "Header too large: %.20s", hdr.b);
 		return (H2SE_ENHANCE_YOUR_CALM);
 	}

bin/varnishtest/tests/r03709.vtc

+varnishtest "h2 req limits"
+
+varnish v1 -cliok "param.set feature +http2"
+varnish v1 -cliok "param.set http_req_hdr_len 40b"
+varnish v1 -vcl {
+	backend be none;
+} -start
+
+logexpect l1 -v v1 -g raw -q BogoHeader {
+	expect 0 1001 BogoHeader "Header too large: :path"
+} -start
+
+client c1 {
+	stream next {
+		txreq -url ${string,repeat,4,/123456789}
+		rxrst
+		expect rst.err == ENHANCE_YOUR_CALM
+	} -run
+} -run
+
+logexpect l1 -wait