Add vmod_h2 to control http rapid reset rate limits per session

bin/varnishd/http2/cache_http2.h

@@ -194,6 +194,13 @@ struct h2_sess {
 	VTAILQ_HEAD(,h2_req)		txqueue;
 
 	h2_error			error;
+
+	// rst rate limit parameters, copied from h2_* parameters
+	vtim_dur			rapid_reset;
+	int64_t				rapid_reset_limit;
+	vtim_dur			rapid_reset_period;
+
+	// rst rate limit state
 	double				rst_budget;
 	vtim_real			last_rst;
 };

bin/varnishd/http2/cache_http2_proto.c

@@ -331,20 +331,20 @@ h2_rapid_reset(struct worker *wrk, struct h2_sess *h2, struct h2_req *r2)
 	ASSERT_RXTHR(h2);
 	CHECK_OBJ_NOTNULL(r2, H2_REQ_MAGIC);
 
-	if (cache_param->h2_rapid_reset_limit == 0)
+	if (h2->rapid_reset_limit == 0)
 		return (0);
 
 	now = VTIM_real();
 	CHECK_OBJ_NOTNULL(r2->req, REQ_MAGIC);
 	AN(r2->req->t_first);
-	if (now - r2->req->t_first > cache_param->h2_rapid_reset)
+	if (now - r2->req->t_first > h2->rapid_reset)
 		return (0);
 
 	d = now - h2->last_rst;
-	h2->rst_budget += cache_param->h2_rapid_reset_limit * d /
-	    cache_param->h2_rapid_reset_period;
+	h2->rst_budget += h2->rapid_reset_limit * d /
+	    h2->rapid_reset_period;
 	h2->rst_budget = vmin_t(double, h2->rst_budget,
-	    cache_param->h2_rapid_reset_limit);
+	    h2->rapid_reset_limit);
 	h2->last_rst = now;
 
 	if (h2->rst_budget < 1.0) {

bin/varnishd/http2/cache_http2_session.c

@@ -127,7 +127,12 @@ h2_init_sess(struct sess *sp,
 	h2_local_settings(&h2->local_settings);
 	h2->remote_settings = H2_proto_settings;
 	h2->decode = decode;
-	h2->rst_budget = cache_param->h2_rapid_reset_limit;
+
+	h2->rapid_reset = cache_param->h2_rapid_reset;
+	h2->rapid_reset_limit = cache_param->h2_rapid_reset_limit;
+	h2->rapid_reset_period = cache_param->h2_rapid_reset_period;
+
+	h2->rst_budget = h2->rapid_reset_limit;
 	h2->last_rst = sp->t_open;
 	AZ(isnan(h2->last_rst));
 

include/tbl/params.h

@@ -1257,6 +1257,10 @@ PARAM_SIMPLE(
 	"HTTP2 maximum size of an uncompressed header list."
 )
 
+#define H2_RR_INFO \
+	"Changes to this parameter affect the default for new HTTP2 " \
+	"sessions. vmod_h2(3) can be used to adjust it from VCL."
+
 PARAM_SIMPLE(
 	/* name */	h2_rapid_reset,
 	/* typ */	timeout,
@@ -1268,8 +1272,8 @@ PARAM_SIMPLE(
 	"The upper threshold for how soon an http/2 RST_STREAM frame has "
 	"to be parsed after a HEADERS frame for it to be treated as "
 	"suspect and subjected to the rate limits specified by "
-	"h2_rapid_reset_limit and h2_rapid_reset_period.",
-	/* flags */	EXPERIMENTAL,
+	"h2_rapid_reset_limit and h2_rapid_reset_period.\n" H2_RR_INFO,
+	/* flags */	EXPERIMENTAL|DELAYED_EFFECT,
 )
 
 PARAM_SIMPLE(
@@ -1283,8 +1287,8 @@ PARAM_SIMPLE(
 	"HTTP2 RST Allowance.\n"
 	"Specifies the maximum number of allowed stream resets issued by\n"
 	"a client over a time period before the connection is closed.\n"
-	"Setting this parameter to 0 disables the limit.",
-	/* flags */	EXPERIMENTAL,
+	"Setting this parameter to 0 disables the limit.\n" H2_RR_INFO,
+	/* flags */	EXPERIMENTAL|DELAYED_EFFECT,
 )
 
 PARAM_SIMPLE(
@@ -1295,8 +1299,8 @@ PARAM_SIMPLE(
 	/* def */	"60.000",
 	/* units */	"seconds",
 	/* descr */
-	"HTTP2 sliding window duration for h2_rapid_reset_limit.",
-	/* flags */	EXPERIMENTAL|WIZARD,
+	"HTTP2 sliding window duration for h2_rapid_reset_limit.\n" H2_RR_INFO,
+	/* flags */	EXPERIMENTAL|DELAYED_EFFECT|WIZARD,
 )
 
 /*--------------------------------------------------------------------

vmod/Makefile.am

@@ -28,6 +28,7 @@ vmod_vcc_files =
 vmod_debug_vcc =
 
 include $(srcdir)/automake_boilerplate_blob.am
+include $(srcdir)/automake_boilerplate_h2.am
 include $(srcdir)/automake_boilerplate_cookie.am
 include $(srcdir)/automake_boilerplate_debug.am
 include $(srcdir)/automake_boilerplate_directors.am

vmod/automake_boilerplate_h2.am

@@ -0,0 +1,42 @@
+# Generated by vmodtool.py --boilerplate.
+
+vmod_h2_vcc ?= $(srcdir)/vmod_h2.vcc
+
+vmod_vcc_files += $(vmod_h2_vcc)
+
+vmod_LTLIBRARIES += libvmod_h2.la
+
+libvmod_h2_la_SOURCES = \
+	vmod_h2.c
+
+libvmod_h2_la_CFLAGS =
+
+vmodtoolargs_h2 ?= --strict --boilerplate -o vcc_h2_if
+vmod_h2_symbols_regex ?= Vmod_h2_Data
+
+libvmod_h2_la_LDFLAGS = \
+	-export-symbols-regex $(vmod_h2_symbols_regex) \
+	$(AM_LDFLAGS) \
+	$(VMOD_LDFLAGS)
+
+nodist_libvmod_h2_la_SOURCES = vcc_h2_if.c vcc_h2_if.h
+
+EXTRA_libvmod_h2_la_DEPENDENCIES = $(nodist_libvmod_h2_la_SOURCES)
+
+EXTRA_DIST += automake_boilerplate_h2.am
+
+$(libvmod_h2_la_OBJECTS): vcc_h2_if.h
+
+vcc_h2_if.h vmod_h2.rst vmod_h2.man.rst: vcc_h2_if.c
+
+# A doc-change will not update mtime on the .h and .c files, so a
+# touch(1) is necessary to signal that vmodtool was in fact run.
+vcc_h2_if.c: $(VMODTOOL) $(srcdir)/vmod_h2.vcc
+	@PYTHON@ $(VMODTOOL) $(vmodtoolargs_h2) $(srcdir)/vmod_h2.vcc
+	touch vcc_h2_if.c
+
+clean-local: clean-vmod-h2
+
+clean-vmod-h2:
+	rm -f $(nodist_libvmod_h2_la_SOURCES)
+	rm -f vmod_h2.rst vmod_h2.man.rst

vmod/tests/h2_b00000.vtc

@@ -0,0 +1,90 @@
+varnishtest "VMOD h2 basics"
+
+varnish v1 -arg "-p feature=+http2" -vcl {
+	import h2;
+
+	backend proforma none;
+
+	sub vcl_recv {
+		return(synth(200));
+	}
+
+	sub vcl_synth {
+		set resp.http.http2-is = h2.is();
+		set resp.body = "";
+		return (deliver);
+	}
+} -start
+
+client c1 {
+	txreq
+	rxresp
+	expect resp.status == 200
+	expect resp.http.http2-is == false
+} -start
+
+client c2 {
+	stream 7 {
+		txreq
+		rxresp
+		expect resp.status == 200
+		expect resp.http.http2-is == true
+	} -run
+} -start
+
+client c1 -wait
+client c2 -wait
+
+# coverage
+varnish v1 -vcl {
+	import h2;
+
+	backend proforma none;
+
+	sub vcl_recv {
+		return(synth(200));
+	}
+
+	sub vcl_synth {
+		set resp.http.rapid-reset-o = h2.rapid_reset(10ms);
+		set resp.http.rapid-reset-n = h2.rapid_reset();
+		set resp.http.rapid-reset-limit-o = h2.rapid_reset_limit(100);
+		set resp.http.rapid-reset-limit-n = h2.rapid_reset_limit();
+		set resp.http.rapid-reset-period-o = h2.rapid_reset_period(10s);
+		set resp.http.rapid-reset-period-n = h2.rapid_reset_period();
+		set resp.http.rapid-reset-budget = h2.rapid_reset_budget();
+		set resp.body = "";
+		return (deliver);
+	}
+}
+
+client c1 {
+	txreq
+	rxresp
+	expect resp.status == 200
+	expect resp.http.rapid-reset-o == -1.000
+	expect resp.http.rapid-reset-n == -1.000
+	expect resp.http.rapid-reset-limit-o == -1
+	expect resp.http.rapid-reset-limit-n == -1
+	expect resp.http.rapid-reset-period-o == -1.000
+	expect resp.http.rapid-reset-period-n == -1.000
+	expect resp.http.rapid-reset-budget == -1.000
+} -start
+
+client c2 {
+	stream 7 {
+		txreq
+		rxresp
+		expect resp.status == 200
+		expect resp.http.rapid-reset-o == 1.000
+		expect resp.http.rapid-reset-n == 0.010
+		expect resp.http.rapid-reset-limit-o == 0
+		expect resp.http.rapid-reset-limit-n == 100
+		expect resp.http.rapid-reset-period-o == 60.000
+		expect resp.http.rapid-reset-period-n == 10.000
+		expect resp.http.rapid-reset-budget == 100.000
+	} -run
+} -start
+
+client c1 -wait
+client c2 -wait

vmod/vmod_h2.c

@@ -0,0 +1,100 @@
+/*-
+ * Copyright 2023 UPLEX - Nils Goroll Systemoptimierung
+ * All rights reserved.
+ *
+ * Author: Nils Goroll <nils.goroll@uplex.de>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED.  IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "config.h"
+
+#include "cache/cache_varnishd.h"
+
+#include "vcc_h2_if.h"
+
+#include "cache/cache_transport.h"
+#include "http2/cache_http2.h"
+
+static struct h2_sess *
+h2get(VRT_CTX)
+{
+	struct h2_sess *h2;
+	uintptr_t *up;
+
+	CHECK_OBJ_NOTNULL(ctx, VRT_CTX_MAGIC);
+	CHECK_OBJ_NOTNULL(ctx->req, REQ_MAGIC); // $Restrict client
+	if (ctx->req->transport != &HTTP2_transport)
+		return (NULL);
+	AZ(SES_Get_proto_priv(ctx->req->sp, &up));
+	CAST_OBJ_NOTNULL(h2, (void *)*up, H2_SESS_MAGIC);
+	return (h2);
+}
+VCL_BOOL
+vmod_is(VRT_CTX)
+{
+	struct h2_sess *h2 = h2get(ctx);
+
+	return (h2 != NULL);
+}
+
+#define GETSET(type, name, argname) \
+type							\
+vmod_ ## name(VRT_CTX, struct VARGS(name) *args)	\
+{							\
+	struct h2_sess *h2 = h2get(ctx);		\
+	type r;						\
+							\
+	if (h2 == NULL)					\
+		return (-1);				\
+							\
+	if (! args->valid_ ## argname)			\
+		return (h2->name);			\
+	if (h2->name == args->argname)			\
+		return (h2->name);			\
+							\
+	Lck_Lock(&h2->sess->mtx);			\
+	r = h2->name;					\
+	if (h2->name != args->argname) {		\
+		h2->name = args->argname;		\
+		h2->rst_budget = h2->rapid_reset_limit;	\
+		h2->last_rst = ctx->now;		\
+	}						\
+	Lck_Unlock(&h2->sess->mtx);			\
+	return (r);					\
+}
+
+GETSET(VCL_DURATION, rapid_reset, threshold)
+GETSET(VCL_INT, rapid_reset_limit, number)
+GETSET(VCL_DURATION, rapid_reset_period, duration)
+
+VCL_REAL
+vmod_rapid_reset_budget(VRT_CTX)
+{
+	struct h2_sess *h2 = h2get(ctx);
+
+	if (h2 == NULL)
+		return (-1);
+
+	return (h2->rst_budget);
+}