Ignore DATA received after stream closed

Fixes #2304

bin/varnishd/http2/cache_http2_proto.c

@@ -636,8 +636,9 @@ h2_rx_data(struct worker *wrk, struct h2_sess *h2, struct h2_req *r2)
 	unsigned wi;
 
 	(void)wrk;
-	AN(r2);
 	ASSERT_RXTHR(h2);
+	if (r2 == NULL)
+		return (0);
 	Lck_Lock(&h2->sess->mtx);
 	AZ(h2->mailcall);
 	h2->mailcall = r2;

bin/varnishtest/tests/t02003.vtc

@@ -417,3 +417,35 @@ varnish v1 -expect MEMPOOL.req1.live == 0
 varnish v1 -expect MEMPOOL.sess0.live == 0
 varnish v1 -expect MEMPOOL.sess1.live == 0
 
+#######################################################################
+# Test DATA error conditions
+
+client c1 {
+	stream 1 {
+		txdata -data "FOOBAR"
+	} -run
+	stream 0 {
+		rxgoaway
+	} -run
+	expect_close
+} -run
+
+client c1 {
+	stream 1 {
+		txreq
+		rxresp
+		txdata -data "FOOBAR"
+	} -run
+	stream 3 {
+		txreq
+		rxresp
+	} -run
+} -run
+
+varnish v1 -vsl_catchup
+
+varnish v1 -expect MEMPOOL.req0.live == 0
+varnish v1 -expect MEMPOOL.req1.live == 0
+varnish v1 -expect MEMPOOL.sess0.live == 0
+varnish v1 -expect MEMPOOL.sess1.live == 0
+