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From a424fefb0a638eb6d32756b5a0c471efc63e5384 Mon Sep 17 00:00:00 2001
From: Vlad Krasnov
Date: Sat, 9 Jan 2016 06:53:14 -0800
Subject: [PATCH] - Add TLS Dynamic Record Resizing
What we do now:
We use a static record size of 4K. This gives a good balance of latency and
throughput.
Optimize latency:
By initialy sending small (1 TCP segment) sized records, we are able to avoid
HoL blocking of the first byte. This means TTFB is sometime lower by a whole
RTT.
Optimizing throughput:
By sending increasingly larger records later in the connection, when HoL is not
a problem, we reduce the overhead of TLS record (29 bytes per record with
GCM/CHACHA-POLY).
Logic:
Start each connection with small records (1369 byte default, change with
ssl_dyn_rec_size_lo). After a given number of records (40, change with
ssl_dyn_rec_threshold) start sending larger records (4229, ssl_dyn_rec_size_hi).
Eventually after the same number of records, start sending the largest records
(ssl_buffer_size).
In case the connection idles for a given amount of time (1s,
ssl_dyn_rec_timeout), the process repeats itself (i.e. begin sending small
records again).
---
src/event/ngx_event_openssl.c | 39 +++++++++++++++++
src/event/ngx_event_openssl.h | 15 ++++++-
src/http/modules/ngx_http_ssl_module.c | 76 ++++++++++++++++++++++++++++++++++
src/http/modules/ngx_http_ssl_module.h | 6 +++
4 files changed, 135 insertions(+), 1 deletion(-)
diff --git a/src/event/ngx_event_openssl.c b/src/event/ngx_event_openssl.c
index 57dfc6c..4a0d41a 100644
--- a/src/event/ngx_event_openssl.c
+++ b/src/event/ngx_event_openssl.c
@@ -1037,6 +1037,7 @@ ngx_ssl_create_connection(ngx_ssl_t *ssl, ngx_connection_t *c, ngx_uint_t flags)
sc->buffer = ((flags & NGX_SSL_BUFFER) != 0);
sc->buffer_size = ssl->buffer_size;
+ sc->dyn_rec = ssl->dyn_rec;
sc->session_ctx = ssl->ctx;
@@ -1575,6 +1576,41 @@ ngx_ssl_send_chain(ngx_connection_t *c, ngx_chain_t *in, off_t limit)
for ( ;; ) {
+ /* Dynamic record resizing:
+ We want the initial records to fit into one TCP segment
+ so we don't get TCP HoL blocking due to TCP Slow Start.
+ A connection always starts with small records, but after
+ a given amount of records sent, we make the records larger
+ to reduce header overhead.
+ After a connection has idled for a given timeout, begin
+ the process from the start. The actual parameters are
+ configurable. If dyn_rec_timeout is 0, we assume dyn_rec is off. */
+
+ if (c->ssl->dyn_rec.timeout > 0 ) {
+
+ if (ngx_current_msec - c->ssl->dyn_rec_last_write >
+ c->ssl->dyn_rec.timeout)
+ {
+ buf->end = buf->start + c->ssl->dyn_rec.size_lo;
+ c->ssl->dyn_rec_records_sent = 0;
+
+ } else {
+ if (c->ssl->dyn_rec_records_sent >
+ c->ssl->dyn_rec.threshold * 2)
+ {
+ buf->end = buf->start + c->ssl->buffer_size;
+
+ } else if (c->ssl->dyn_rec_records_sent >
+ c->ssl->dyn_rec.threshold)
+ {
+ buf->end = buf->start + c->ssl->dyn_rec.size_hi;
+
+ } else {
+ buf->end = buf->start + c->ssl->dyn_rec.size_lo;
+ }
+ }
+ }
+
while (in && buf->last < buf->end && send < limit) {
if (in->buf->last_buf || in->buf->flush) {
flush = 1;
@@ -1676,6 +1712,9 @@ ngx_ssl_write(ngx_connection_t *c, u_char *data, size_t size)
if (n > 0) {
+ c->ssl->dyn_rec_records_sent++;
+ c->ssl->dyn_rec_last_write = ngx_current_msec;
+
if (c->ssl->saved_read_handler) {
c->read->handler = c->ssl->saved_read_handler;
diff --git a/src/event/ngx_event_openssl.h b/src/event/ngx_event_openssl.h
index c86be2a..4a45934 100644
--- a/src/event/ngx_event_openssl.h
+++ b/src/event/ngx_event_openssl.h
@@ -38,9 +38,18 @@
typedef struct {
+ ngx_msec_t timeout;
+ ngx_uint_t threshold;
+ size_t size_lo;
+ size_t size_hi;
+} ngx_ssl_dyn_rec_t;
+
+
+typedef struct {
SSL_CTX *ctx;
ngx_log_t *log;
size_t buffer_size;
+ ngx_ssl_dyn_rec_t dyn_rec;
} ngx_ssl_t;
@@ -63,6 +72,10 @@ typedef struct {
unsigned no_wait_shutdown:1;
unsigned no_send_shutdown:1;
unsigned handshake_buffer_set:1;
+
+ ngx_ssl_dyn_rec_t dyn_rec;
+ ngx_msec_t dyn_rec_last_write;
+ ngx_uint_t dyn_rec_records_sent;
} ngx_ssl_connection_t;
@@ -72,7 +85,7 @@ typedef struct {
#define NGX_SSL_DFLT_BUILTIN_SCACHE -5
-#define NGX_SSL_MAX_SESSION_SIZE 4096
+#define NGX_SSL_MAX_SESSION_SIZE 16384
typedef struct ngx_ssl_sess_id_s ngx_ssl_sess_id_t;
diff --git a/src/http/modules/ngx_http_ssl_module.c b/src/http/modules/ngx_http_ssl_module.c
index 7b051ea..e2941af 100644
--- a/src/http/modules/ngx_http_ssl_module.c
+++ b/src/http/modules/ngx_http_ssl_module.c
@@ -233,6 +233,41 @@ static ngx_command_t ngx_http_ssl_commands[] = {
offsetof(ngx_http_ssl_srv_conf_t, stapling_verify),
NULL },
+ { ngx_string("ssl_dyn_rec_enable"),
+ NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_CONF_FLAG,
+ ngx_conf_set_flag_slot,
+ NGX_HTTP_SRV_CONF_OFFSET,
+ offsetof(ngx_http_ssl_srv_conf_t, dyn_rec_enable),
+ NULL },
+
+ { ngx_string("ssl_dyn_rec_timeout"),
+ NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_CONF_FLAG,
+ ngx_conf_set_msec_slot,
+ NGX_HTTP_SRV_CONF_OFFSET,
+ offsetof(ngx_http_ssl_srv_conf_t, dyn_rec_timeout),
+ NULL },
+
+ { ngx_string("ssl_dyn_rec_size_lo"),
+ NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_CONF_FLAG,
+ ngx_conf_set_size_slot,
+ NGX_HTTP_SRV_CONF_OFFSET,
+ offsetof(ngx_http_ssl_srv_conf_t, dyn_rec_size_lo),
+ NULL },
+
+ { ngx_string("ssl_dyn_rec_size_hi"),
+ NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_CONF_FLAG,
+ ngx_conf_set_size_slot,
+ NGX_HTTP_SRV_CONF_OFFSET,
+ offsetof(ngx_http_ssl_srv_conf_t, dyn_rec_size_hi),
+ NULL },
+
+ { ngx_string("ssl_dyn_rec_threshold"),
+ NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_CONF_FLAG,
+ ngx_conf_set_num_slot,
+ NGX_HTTP_SRV_CONF_OFFSET,
+ offsetof(ngx_http_ssl_srv_conf_t, dyn_rec_threshold),
+ NULL },
+
ngx_null_command
};
@@ -532,6 +567,11 @@ ngx_http_ssl_create_srv_conf(ngx_conf_t *cf)
sscf->session_ticket_keys = NGX_CONF_UNSET_PTR;
sscf->stapling = NGX_CONF_UNSET;
sscf->stapling_verify = NGX_CONF_UNSET;
+ sscf->dyn_rec_enable = NGX_CONF_UNSET;
+ sscf->dyn_rec_timeout = NGX_CONF_UNSET_MSEC;
+ sscf->dyn_rec_size_lo = NGX_CONF_UNSET_SIZE;
+ sscf->dyn_rec_size_hi = NGX_CONF_UNSET_SIZE;
+ sscf->dyn_rec_threshold = NGX_CONF_UNSET_UINT;
return sscf;
}
@@ -596,6 +636,20 @@ ngx_http_ssl_merge_srv_conf(ngx_conf_t *cf, void *parent, void *child)
ngx_conf_merge_str_value(conf->stapling_responder,
prev->stapling_responder, "");
+ ngx_conf_merge_value(conf->dyn_rec_enable, prev->dyn_rec_enable, 0);
+ ngx_conf_merge_msec_value(conf->dyn_rec_timeout, prev->dyn_rec_timeout,
+ 1000);
+ /* Default sizes for the dynamic record sizes are defined to fit maximal
+ TLS + IPv6 overhead in a single TCP segment for lo and 3 segments for hi:
+ 1369 = 1500 - 40 (IP) - 20 (TCP) - 10 (Time) - 61 (Max TLS overhead) */
+ ngx_conf_merge_size_value(conf->dyn_rec_size_lo, prev->dyn_rec_size_lo,
+ 1369);
+ /* 4229 = (1500 - 40 - 20 - 10) * 3 - 61 */
+ ngx_conf_merge_size_value(conf->dyn_rec_size_hi, prev->dyn_rec_size_hi,
+ 4229);
+ ngx_conf_merge_uint_value(conf->dyn_rec_threshold, prev->dyn_rec_threshold,
+ 40);
+
conf->ssl.log = cf->log;
if (conf->enable) {
@@ -773,6 +827,28 @@ ngx_http_ssl_merge_srv_conf(ngx_conf_t *cf, void *parent, void *child)
}
+ if (conf->dyn_rec_enable) {
+ conf->ssl.dyn_rec.timeout = conf->dyn_rec_timeout;
+ conf->ssl.dyn_rec.threshold = conf->dyn_rec_threshold;
+
+ if (conf->buffer_size > conf->dyn_rec_size_lo) {
+ conf->ssl.dyn_rec.size_lo = conf->dyn_rec_size_lo;
+
+ } else {
+ conf->ssl.dyn_rec.size_lo = conf->buffer_size;
+ }
+
+ if (conf->buffer_size > conf->dyn_rec_size_hi) {
+ conf->ssl.dyn_rec.size_hi = conf->dyn_rec_size_hi;
+
+ } else {
+ conf->ssl.dyn_rec.size_hi = conf->buffer_size;
+ }
+
+ } else {
+ conf->ssl.dyn_rec.timeout = 0;
+ }
+
return NGX_CONF_OK;
}
diff --git a/src/http/modules/ngx_http_ssl_module.h b/src/http/modules/ngx_http_ssl_module.h
index 8e69e9e..05967d4 100644
--- a/src/http/modules/ngx_http_ssl_module.h
+++ b/src/http/modules/ngx_http_ssl_module.h
@@ -56,6 +56,12 @@ typedef struct {
u_char *file;
ngx_uint_t line;
+
+ ngx_flag_t dyn_rec_enable;
+ ngx_msec_t dyn_rec_timeout;
+ size_t dyn_rec_size_lo;
+ size_t dyn_rec_size_hi;
+ ngx_uint_t dyn_rec_threshold;
} ngx_http_ssl_srv_conf_t;
--
2.7.4 (Apple Git-66)