commit c344e21f23c6605caa257abbf46fd333b7015928
Author: Tomas Korbar <tkorbar@redhat.com>
Date:   Wed Oct 18 20:42:21 2023 +0200

    vcl_vrt: Skip VCL execution if the client is gone
    
    Upstream PR #4006

diff --git a/bin/varnishd/VSC_main.vsc b/bin/varnishd/VSC_main.vsc
index b237f86..88a659f 100644
--- a/bin/varnishd/VSC_main.vsc
+++ b/bin/varnishd/VSC_main.vsc
@@ -324,6 +324,15 @@
 	Number of times an HTTP/2 stream was refused because the queue was
 	too long already. See also parameter thread_queue_limit.
 
+.. varnish_vsc:: req_reset
+	:group: wrk
+	:oneliner:	Requests reset
+
+	Number of times a client left before the VCL processing of its
+	requests completed. For HTTP/2 sessions, either the stream was
+	reset by an RST_STREAM frame from the client, or a stream or
+	connection error occurred.
+
 .. varnish_vsc:: n_object
 	:type:	gauge
 	:group: wrk
diff --git a/bin/varnishd/cache/cache_transport.h b/bin/varnishd/cache/cache_transport.h
index 5da5e35..8546411 100644
--- a/bin/varnishd/cache/cache_transport.h
+++ b/bin/varnishd/cache/cache_transport.h
@@ -42,6 +42,7 @@ typedef void vtr_sess_panic_f (struct vsb *, const struct sess *);
 typedef void vtr_req_panic_f (struct vsb *, const struct req *);
 typedef void vtr_req_fail_f (struct req *, enum sess_close);
 typedef void vtr_reembark_f (struct worker *, struct req *);
+typedef int vtr_poll_f (struct req *);
 typedef int vtr_minimal_response_f (struct req *, uint16_t status);
 
 struct transport {
@@ -62,6 +63,7 @@ struct transport {
 	vtr_sess_panic_f		*sess_panic;
 	vtr_req_panic_f			*req_panic;
 	vtr_reembark_f			*reembark;
+	vtr_poll_f			*poll;
 	vtr_minimal_response_f		*minimal_response;
 
 	VTAILQ_ENTRY(transport)		list;
diff --git a/bin/varnishd/cache/cache_vcl_vrt.c b/bin/varnishd/cache/cache_vcl_vrt.c
index 5f3bfee..e35ae59 100644
--- a/bin/varnishd/cache/cache_vcl_vrt.c
+++ b/bin/varnishd/cache/cache_vcl_vrt.c
@@ -37,8 +37,10 @@
 #include "cache_varnishd.h"
 
 #include "vcl.h"
+#include "vtim.h"
 
 #include "cache_director.h"
+#include "cache_transport.h"
 #include "cache_vcl.h"
 
 /*--------------------------------------------------------------------*/
@@ -338,6 +340,35 @@ VRT_rel_vcl(VRT_CTX, struct vclref **refp)
  * The workspace argument is where random VCL stuff gets space from.
  */
 
+static int
+req_poll(struct worker *wrk, struct req *req)
+{
+
+	CHECK_OBJ_NOTNULL(req->top, REQ_MAGIC);
+	CHECK_OBJ_NOTNULL(req->top->transport, TRANSPORT_MAGIC);
+
+	/* NB: Since a fail transition leads to vcl_synth, the request may be
+	 * short-circuited twice.
+	 */
+	if (req->req_reset) {
+		wrk->handling = VCL_RET_FAIL;
+		return (-1);
+	}
+
+	if (!FEATURE(FEATURE_VCL_REQ_RESET))
+		return (0);
+	if (req->top->transport->poll == NULL)
+		return (0);
+	if (req->top->transport->poll(req->top) >= 0)
+		return (0);
+
+	VSLb_ts_req(req, "Reset", W_TIM_real(wrk));
+	wrk->stats->req_reset++;
+	wrk->handling = VCL_RET_FAIL;
+	req->req_reset = 1;
+	return (-1);
+}
+
 static void
 vcl_call_method(struct worker *wrk, struct req *req, struct busyobj *bo,
     void *specific, unsigned method, vcl_func_f *func)
@@ -351,6 +382,8 @@ vcl_call_method(struct worker *wrk, struct req *req, struct busyobj *bo,
 		CHECK_OBJ_NOTNULL(req, REQ_MAGIC);
 		CHECK_OBJ_NOTNULL(req->sp, SESS_MAGIC);
 		CHECK_OBJ_NOTNULL(req->vcl, VCL_MAGIC);
+		if (req_poll(wrk, req))
+			return;
 		VCL_Req2Ctx(&ctx, req);
 	}
 	if (bo != NULL) {
diff --git a/bin/varnishd/http2/cache_http2_session.c b/bin/varnishd/http2/cache_http2_session.c
index 720b009..1584740 100644
--- a/bin/varnishd/http2/cache_http2_session.c
+++ b/bin/varnishd/http2/cache_http2_session.c
@@ -440,6 +440,16 @@ h2_new_session(struct worker *wrk, void *arg)
 	h2_del_sess(wrk, h2, SC_RX_JUNK);
 }
 
+static int v_matchproto_(vtr_poll_f)
+h2_poll(struct req *req)
+{
+	struct h2_req *r2;
+
+	CHECK_OBJ_NOTNULL(req, REQ_MAGIC);
+	CAST_OBJ_NOTNULL(r2, req->transport_priv, H2_REQ_MAGIC);
+	return (r2->error ? -1 : 1);
+}
+
 struct transport H2_transport = {
 	.name =			"H2",
 	.magic =		TRANSPORT_MAGIC,
@@ -449,4 +459,5 @@ struct transport H2_transport = {
 	.req_body =		h2_req_body,
 	.req_fail =		h2_req_fail,
 	.sess_panic =		h2_sess_panic,
+	.poll =			h2_poll,
 };
diff --git a/bin/varnishd/mgt/mgt_param_bits.c b/bin/varnishd/mgt/mgt_param_bits.c
index 263d8a3..788d8f0 100644
--- a/bin/varnishd/mgt/mgt_param_bits.c
+++ b/bin/varnishd/mgt/mgt_param_bits.c
@@ -219,7 +219,12 @@ tweak_feature(struct vsb *vsb, const struct parspec *par, const char *arg)
 	(void)par;
 
 	if (arg != NULL && arg != JSON_FMT) {
-		if (!strcmp(arg, "none")) {
+		if (!strcmp(arg, "default")) {
+			AZ(bit_tweak(vsb, mgt_param.feature_bits,
+				FEATURE_Reserved,
+				"+vcl_req_reset",
+				feature_tags, "feature bit", "+"));
+		}else if (!strcmp(arg, "none")) {
 			memset(mgt_param.feature_bits,
 			    0, sizeof mgt_param.feature_bits);
 		} else {
@@ -271,6 +276,6 @@ struct parspec VSL_parspec[] = {
 #define FEATURE_BIT(U, l, d, ld) "\n\t" #l "\t" d
 #include "tbl/feature_bits.h"
 #undef FEATURE_BIT
-		, 0, "none", "" },
+		, 0, "default", "" },
 	{ NULL, NULL, NULL }
 };
diff --git a/doc/sphinx/reference/vsl.rst b/doc/sphinx/reference/vsl.rst
index 4d01f5b..b529562 100644
--- a/doc/sphinx/reference/vsl.rst
+++ b/doc/sphinx/reference/vsl.rst
@@ -71,6 +71,11 @@ Resp
 Restart
 	Client request is being restarted.
 
+Reset
+        The client closed its connection, reset its stream or caused
+        a stream error that forced Varnish to reset the stream. Request
+        processing is interrupted and considered failed.
+
 Pipe handling timestamps
 ~~~~~~~~~~~~~~~~~~~~~~~~
 
diff --git a/include/tbl/feature_bits.h b/include/tbl/feature_bits.h
index 23f1b01..844ecfa 100644
--- a/include/tbl/feature_bits.h
+++ b/include/tbl/feature_bits.h
@@ -83,6 +83,12 @@ FEATURE_BIT(HTTP_DATE_POSTEL,	http_date_postel,
     "like Date:, Last-Modified:, Expires: etc."
 )
 
+FEATURE_BIT(VCL_REQ_RESET,			vcl_req_reset,
+    "Stop processing client VCL once the client is gone.",
+    "Stop processing client VCL once the client is gone. "
+    "When this happens MAIN.req_reset is incremented."
+)
+
 #undef FEATURE_BIT
 
 /*lint -restore */
diff --git a/include/tbl/req_flags.h b/include/tbl/req_flags.h
index 2c0dbe8..3d3f05f 100644
--- a/include/tbl/req_flags.h
+++ b/include/tbl/req_flags.h
@@ -39,6 +39,7 @@ REQ_FLAG(is_hitpass,		1, 0, "")
 REQ_FLAG(waitinglist,		0, 0, "")
 REQ_FLAG(want100cont,		0, 0, "")
 REQ_FLAG(late100cont,		0, 0, "")
+REQ_FLAG(req_reset,		0, 0, "")
 #undef REQ_FLAG
 
 /*lint -restore */