[6.0] bec48849f h2: Ensure highest_stream is consistent also on Upgrade: h2c

[Dridi Boukelmoune]

commit bec48849fba4146aa707d2f3d59089ba24944f21
Author: Dag Haavi Finstad <daghf at varnish-software.com>
Date:   Thu Apr 25 14:36:57 2024 +0200

    h2: Ensure highest_stream is consistent also on Upgrade: h2c
    
    Conflicts:
            bin/varnishd/http2/cache_http2_session.c

diff --git a/bin/varnishd/http2/cache_http2_session.c b/bin/varnishd/http2/cache_http2_session.c
index 2cfba41ef..c6a742ffa 100644
--- a/bin/varnishd/http2/cache_http2_session.c
+++ b/bin/varnishd/http2/cache_http2_session.c
@@ -289,6 +289,8 @@ h2_ou_session(struct worker *wrk, struct h2_sess *h2,
 
 	/* Start req thread */
 	r2 = h2_new_req(wrk, h2, 1, req);
+	AZ(h2->highest_stream);
+	h2->highest_stream = r2->stream;
 	req->transport = &H2_transport;
 	req->req_step = R_STP_TRANSPORT;
 	req->task.func = h2_do_req;
diff --git a/bin/varnishtest/tests/t02001.vtc b/bin/varnishtest/tests/t02001.vtc
index 1da6fb3b5..0e02e82be 100644
--- a/bin/varnishtest/tests/t02001.vtc
+++ b/bin/varnishtest/tests/t02001.vtc
@@ -1,6 +1,6 @@
 varnishtest	"H1->H2 Upgrade"
 
-barrier b1 cond 2
+barrier b1 cond 2 -cyclic
 
 server s1 {
 	rxreq
@@ -37,6 +37,11 @@ server s1 {
 	expect req.http.host == foo.bar
 	barrier b1 sync
 	txresp -status 402 -bodylen 11
+
+	rxreq
+	expect req.url == /upgrade3
+	barrier b1 sync
+	txresp -status 200
 } -start
 
 varnish v1 -vsl_catchup
@@ -156,3 +161,37 @@ 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
+
+# Upgrade: h2c followed by activity on the newly opened stream
+client c1 {
+	send "GET /upgrade3 HTTP/1.1\r\n"
+	send "Host: foo.bar\r\n"
+	send "Upgrade: h2c\r\n"
+	send "HTTP2-Settings: AAMAAABkAAQAAP__\r\n"
+	send "\r\n"
+	rxresp
+	expect resp.status == 101
+	expect resp.http.upgrade == h2c
+	expect resp.http.connection == Upgrade
+	txpri
+	stream 0 {
+		rxsettings
+		txsettings
+		txsettings -ack
+		rxsettings
+		expect settings.ack == true
+	} -run
+	barrier b1 sync
+	stream 1 {
+		txwinup -size 256
+		rxresp
+		expect resp.status == 200
+	} -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