[master] cafeb6c12 h2: Add a rate limit facility for h/2 RST handling
Dag Haavi Finstad
daghf at varnish-software.com
Tue Oct 17 13:59:06 UTC 2023
commit cafeb6c12248740d461ba2b37fb295aab8cb968f
Author: Dag Haavi Finstad <daghf at varnish-software.com>
Date: Thu Oct 12 10:50:55 2023 +0200
h2: Add a rate limit facility for h/2 RST handling
This adds parameters h2_rst_allowance and h2_rst_allowance_period,
which govern the rate of which we allow clients to reset h/2 streams.
If the limit is exceeded the connection is closed.
Mitigates: #3996
diff --git a/bin/varnishd/http2/cache_http2.h b/bin/varnishd/http2/cache_http2.h
index eb6e8f6a9..9457c99f2 100644
--- a/bin/varnishd/http2/cache_http2.h
+++ b/bin/varnishd/http2/cache_http2.h
@@ -193,6 +193,8 @@ struct h2_sess {
VTAILQ_HEAD(,h2_req) txqueue;
h2_error error;
+ double rst_budget;
+ vtim_real last_rst;
};
#define ASSERT_RXTHR(h2) do {assert(h2->rxthr == pthread_self());} while(0)
diff --git a/bin/varnishd/http2/cache_http2_proto.c b/bin/varnishd/http2/cache_http2_proto.c
index c62a8c429..272082498 100644
--- a/bin/varnishd/http2/cache_http2_proto.c
+++ b/bin/varnishd/http2/cache_http2_proto.c
@@ -320,9 +320,41 @@ h2_rx_push_promise(struct worker *wrk, struct h2_sess *h2, struct h2_req *r2)
/**********************************************************************
*/
+static h2_error
+h2_rapid_reset(struct worker *wrk, struct h2_sess *h2, struct h2_req *r2)
+{
+ vtim_real now;
+ vtim_dur d;
+
+ CHECK_OBJ_NOTNULL(wrk, WORKER_MAGIC);
+ ASSERT_RXTHR(h2);
+ CHECK_OBJ_NOTNULL(r2, H2_REQ_MAGIC);
+
+ if (cache_param->h2_rapid_reset_limit == 0)
+ return (0);
+
+ now = VTIM_real();
+ d = now - h2->last_rst;
+ h2->rst_budget += cache_param->h2_rapid_reset_limit * d /
+ cache_param->h2_rapid_reset_period;
+ h2->rst_budget = vmin_t(double, h2->rst_budget,
+ cache_param->h2_rapid_reset_limit);
+ h2->last_rst = now;
+
+ if (h2->rst_budget < 1.0) {
+ Lck_Lock(&h2->sess->mtx);
+ VSLb(h2->vsl, SLT_Error, "H2: Hit RST limit. Closing session.");
+ Lck_Unlock(&h2->sess->mtx);
+ return (H2CE_ENHANCE_YOUR_CALM);
+ }
+ h2->rst_budget -= 1.0;
+ return (0);
+}
+
static h2_error v_matchproto_(h2_rxframe_f)
h2_rx_rst_stream(struct worker *wrk, struct h2_sess *h2, struct h2_req *r2)
{
+ h2_error h2e;
CHECK_OBJ_NOTNULL(wrk, WORKER_MAGIC);
ASSERT_RXTHR(h2);
@@ -332,8 +364,9 @@ h2_rx_rst_stream(struct worker *wrk, struct h2_sess *h2, struct h2_req *r2)
return (H2CE_FRAME_SIZE_ERROR);
if (r2 == NULL)
return (0);
+ h2e = h2_rapid_reset(wrk, h2, r2);
h2_kill_req(wrk, h2, r2, h2_streamerror(vbe32dec(h2->rxf_data)));
- return (0);
+ return (h2e);
}
/**********************************************************************
diff --git a/bin/varnishd/http2/cache_http2_session.c b/bin/varnishd/http2/cache_http2_session.c
index e3e3c116c..672b40d64 100644
--- a/bin/varnishd/http2/cache_http2_session.c
+++ b/bin/varnishd/http2/cache_http2_session.c
@@ -127,6 +127,9 @@ 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->last_rst = sp->t_open;
+ AZ(isnan(h2->last_rst));
AZ(VHT_Init(h2->dectbl, h2->local_settings.header_table_size));
diff --git a/bin/varnishtest/tests/r03996.vtc b/bin/varnishtest/tests/r03996.vtc
new file mode 100644
index 000000000..5864c837f
--- /dev/null
+++ b/bin/varnishtest/tests/r03996.vtc
@@ -0,0 +1,49 @@
+varnishtest "h2 rapid reset"
+
+barrier b1 sock 5
+
+server s1 {
+ rxreq
+ txresp
+} -start
+
+varnish v1 -cliok "param.set feature +http2"
+varnish v1 -cliok "param.set debug +syncvsl"
+varnish v1 -cliok "param.set h2_rapid_reset_limit 3"
+
+varnish v1 -vcl+backend {
+ import vtc;
+
+ sub vcl_recv {
+ vtc.barrier_sync("${b1_sock}");
+ }
+
+} -start
+
+client c1 {
+ stream 0 {
+ rxgoaway
+ expect goaway.err == ENHANCE_YOUR_CALM
+ } -start
+
+ stream 1 {
+ txreq
+ txrst
+ } -run
+ stream 3 {
+ txreq
+ txrst
+ } -run
+ stream 5 {
+ txreq
+ txrst
+ } -run
+ stream 7 {
+ txreq
+ txrst
+ } -run
+
+ barrier b1 sync
+ stream 0 -wait
+} -run
+
diff --git a/include/tbl/params.h b/include/tbl/params.h
index cb7b7f5aa..cbea1bc31 100644
--- a/include/tbl/params.h
+++ b/include/tbl/params.h
@@ -1257,6 +1257,34 @@ PARAM_SIMPLE(
"HTTP2 maximum size of an uncompressed header list."
)
+PARAM_SIMPLE(
+ /* name */ h2_rapid_reset_limit,
+ /* typ */ uint,
+ /* min */ "0",
+ /* max */ NULL,
+ /* def */ "0",
+ /* units */ NULL,
+ /* descr */
+ "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,
+)
+
+PARAM_SIMPLE(
+ /* name */ h2_rapid_reset_period,
+ /* typ */ timeout,
+ /* min */ "1.000",
+ /* max */ NULL,
+ /* def */ "60.000",
+ /* units */ "seconds",
+ /* descr */
+ "HTTP2 sliding window duration for h2_rapid_reset_limit.",
+ /* flags */ EXPERIMENTAL|WIZARD,
+)
+
+
/*--------------------------------------------------------------------
* Memory pool parameters
*/
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