Add Pre-warm TLS Tunnel

.gitignore

@@ -116,6 +116,7 @@ proxy/http/remap/test_PluginDso
 proxy/http/remap/test_PluginFactory
 proxy/http/remap/test_RemapPluginInfo
 proxy/http/test_proxy_http
+proxy/http/test_PreWarm
 proxy/http/remap/test_*
 proxy/http2/test_libhttp2
 proxy/http2/test_Http2DependencyTree

doc/admin-guide/files/records.config.en.rst

@@ -3949,6 +3949,30 @@ SNI Routing
    Frequency of checking the activity of SNI Routing Tunnel. Set to ``0`` to disable monitoring of the activity of the SNI tunnels.
    The feature is disabled by default.
 
+.. ts:cv:: CONFIG proxy.config.tunnel.prewarm INT 0
+
+   Enable :ref:`pre-warming-tls-tunnel`. The feature is disabled by default.
+
+.. ts:cv:: CONFIG proxy.config.tunnel.prewarm.max_stats_size INT 100
+
+   Max size of :ref:`dynamic stats for Pre-warming TLS Tunnel <pre-warming-tls-tunnel-stats>`.
+
+.. ts:cv:: CONFIG proxy.config.tunnel.prewarm.algorithm INT 2
+
+   Version of pre-warming algorithm.
+
+   ===== ======================================================================
+   Value Description
+   ===== ======================================================================
+   ``1`` Periodical pre-warming only
+   ``2`` Event based pre-warming + Periodical pre-warming
+   ===== ======================================================================
+
+.. ts:cv:: CONFIG proxy.config.tunnel.prewarm.event_period INT 1000
+   :units: milliseconds
+
+   Frequency of periodical pre-warming in milli-seconds.
+
 OCSP Stapling Configuration
 ===========================
 

doc/admin-guide/files/sni.yaml.en.rst

@@ -159,6 +159,27 @@ tunnel_alpn               Inbound   List of ALPN Protocol Ids for Partial Blind
                                     This only works with ``partial_blind_route``.
 ========================= ========= ========================================================================================
 
+Pre-warming TLS Tunnel
+----------------------
+
+=============================== ========================================================================================
+Key                             Meaning
+=============================== ========================================================================================
+tunnel_prewarm                  Override :ts:cv:`proxy.config.tunnel.prewarm` in records.config.
+
+tunnel_prewarm_srv              Enable SRV record lookup on pre-warming. Default is ``false``.
+
+tunnel_prewarm_rate             Rate of how many connections to pre-warm. Default is ``1.0``.
+
+tunnel_prewarm_min              Minimum number of pre-warming queue size (per thread). Default is ``0``.
+
+tunnel_prewarm_max              Maximum number of pre-warming queue size (per thread). Default is ``-1`` (unlimited).
+
+tunnel_prewarm_connect_timeout  Timeout for TCP/TLS handshake (in seconds).
+
+tunnel_prewarm_inactive_timeout Inactive timeout for connections in the pool (in seconds).
+=============================== ========================================================================================
+
 Client verification, via ``verify_client``, corresponds to setting
 :ts:cv:`proxy.config.ssl.client.certification_level` for this connection as noted below.
 

doc/admin-guide/layer-4-routing.en.rst

@@ -129,3 +129,51 @@ tunneled connection like this, the only transaction hooks that will be triggered
 :c:macro:`TS_HTTP_TXN_START_HOOK` and :c:macro:`TS_HTTP_TXN_CLOSE_HOOK`. In addition, because |TS|
 does not terminate (and therefore does not decrypt) the connection, it cannot be cached or served from
 cache.
+
+.. _pre-warming-tls-tunnel:
+
+Pre-warming TLS Tunnel
+======================
+
+Pre-warming TLS Tunnel reduces the latency of TLS connections (``forward_route`` and ``partial_blind_route`` type SNI
+Routing). When this feature is enabled, each ET_NET thread makes TLS connections pool per routing type, SNI, and ALPN.
+
+.. figure:: ../uml/images/l4-pre-warming-overview.svg
+   :align: center
+
+Stats for connection pools are registered dynamically on start up. Details in :ref:`pre-warming-tls-tunnel-stats`.
+
+Examples
+--------
+
+.. code:: yaml
+
+   sni:
+   - fqdn: foo.com
+     http2: off
+     partial_blind_route: bar.com
+     client_sni_policy: server_name
+     tunnel_prewarm: true
+     tunnel_prewarm_connect_timeout: 10
+     tunnel_prewarm_inactive_timeout: 150
+     tunnel_prewarm_max: 100
+     tunnel_prewarm_min: 10
+     tunnel_alpn:
+       - h2
+
+.. code::
+
+  proxy.process.tunnel.prewarm.bar.com:443.tls.current_init 0
+  proxy.process.tunnel.prewarm.bar.com:443.tls.current_open 10
+  proxy.process.tunnel.prewarm.bar.com:443.tls.total_hit 0
+  proxy.process.tunnel.prewarm.bar.com:443.tls.total_miss 0
+  proxy.process.tunnel.prewarm.bar.com:443.tls.total_handshake_time 1106250000
+  proxy.process.tunnel.prewarm.bar.com:443.tls.total_handshake_count 10
+  proxy.process.tunnel.prewarm.bar.com:443.tls.total_retry 0
+  proxy.process.tunnel.prewarm.bar.com:443.tls.http2.current_init 0
+  proxy.process.tunnel.prewarm.bar.com:443.tls.http2.current_open 10
+  proxy.process.tunnel.prewarm.bar.com:443.tls.http2.total_hit 0
+  proxy.process.tunnel.prewarm.bar.com:443.tls.http2.total_miss 0
+  proxy.process.tunnel.prewarm.bar.com:443.tls.http2.total_handshake_time 1142368000
+  proxy.process.tunnel.prewarm.bar.com:443.tls.http2.total_handshake_count 10
+  proxy.process.tunnel.prewarm.bar.com:443.tls.http2.total_retry 0

doc/admin-guide/monitoring/statistics/core/ssl.en.rst

@@ -237,3 +237,45 @@ SSL/TLS
    :type: gauge
 
    A gauge of current active SNI Routing Tunnels.
+
+.. _pre-warming-tls-tunnel-stats:
+
+Pre-warming TLS Tunnel
+----------------------
+
+Stats for Pre-warming TLS Tunnel is registered dynamically. The ``POOL`` in below represents combination of ``<Hostname of destination>.<Type of Tunnel>.<ALPN Name (if there)>``.
+
+.. ts:stat:: global proxy.process.tunnel.prewarm.POOL.current_init integer
+   :type: gauge
+
+   Represents the current number of initializing connections in the pool.
+
+.. ts:stat:: global proxy.process.tunnel.prewarm.POOL.current_open integer
+   :type: gauge
+
+   Represents the current number of established connections in the pool.
+
+.. ts:stat:: global proxy.process.tunnel.prewarm.POOL.total_hit integer
+   :type: counter
+
+   Represents the total number of pre-warmed connection is used.
+
+.. ts:stat:: global proxy.process.tunnel.prewarm.POOL.total_miss integer
+   :type: counter
+
+   Represents the total number of pre-warmed connection is not used.
+
+.. ts:stat:: global proxy.process.tunnel.prewarm.POOL.total_handshake_time integer
+   :type: counter
+
+   Represents the total number of handshake duration of pre-warming.
+
+.. ts:stat:: global proxy.process.tunnel.prewarm.POOL.total_handshake_count integer
+   :type: counter
+
+   Represents the total number of handshake time of pre-warming.
+
+.. ts:stat:: global proxy.process.tunnel.prewarm.POOL.total_retry integer
+   :type: counter
+
+   Represents the total number of pre-warming retry.

doc/uml/l4-pre-warming-overview.uml

@@ -0,0 +1,32 @@
+' Licensed under the Apache License, Version 2.0 (the "License");
+' you may not use this file except in compliance with the License.
+' You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+' Unless required by  applicable law or agreed to in writing, software distributed under the License is distributed
+' on an \"AS IS\" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+' See the License for the specific language governing permissions and limitations under the License.
+
+@startuml
+'title Pre-warm TLS Tunnel
+skinparam sequenceMessageAlign direction
+skinparam ParticipantPadding 75
+'skinparam monochrome reverse
+skinparam backgroundColor #white
+hide footbox
+
+participant client
+participant proxy
+participant origin_server
+
+group pre-warm connection pool
+  proxy -> origin_server : open connection
+  proxy -> origin_server : open connection
+  proxy -> origin_server : open connection
+  ...
+end
+...
+group pool size > 0
+  client -> proxy : open connection
+  hnote over proxy #white: use pre-warmed connection from pool
+  rnote over client, origin_server #lightgreen: TLS Partial Blind Tunnel
+end
+@enduml

iocore/eventsystem/I_EThread.h

@@ -43,6 +43,8 @@ struct DiskHandler;
 struct EventIO;
 
 class ServerSessionPool;
+class PreWarmQueue;
+
 class Event;
 class Continuation;
 
@@ -349,6 +351,7 @@ class EThread : public Thread
   Event *start_event = nullptr;
 
   ServerSessionPool *server_session_pool = nullptr;
+  PreWarmQueue *prewarm_queue            = nullptr;
 
   /** Default handler used until it is overridden.
 

iocore/eventsystem/I_Thread.h

@@ -135,6 +135,7 @@ class Thread
   ProxyAllocator ioDataAllocator;
   ProxyAllocator ioAllocator;
   ProxyAllocator ioBlockAllocator;
+  ProxyAllocator preWarmSMAllocator;
   // From InkAPI (plugins wrappers)
   ProxyAllocator apiHookAllocator;
   ProxyAllocator INKContAllocator;

iocore/net/P_SNIActionPerformer.h

@@ -98,8 +98,9 @@ class ControlH2 : public ActionItem
 class TunnelDestination : public ActionItem
 {
 public:
-  TunnelDestination(const std::string_view &dest, SNIRoutingType type, const std::vector<int> &alpn)
-    : destination(dest), type(type), alpn_ids(alpn)
+  TunnelDestination(const std::string_view &dest, SNIRoutingType type, YamlSNIConfig::TunnelPreWarm prewarm,
+                    const std::vector<int> &alpn)
+    : destination(dest), type(type), tunnel_prewarm(prewarm), alpn_ids(alpn)
   {
     need_fix = (destination.find_first_of('$') != std::string::npos);
   }
@@ -115,10 +116,10 @@ class TunnelDestination : public ActionItem
       // If needed, we will try to amend the tunnel destination.
       if (ctx._fqdn_wildcard_captured_groups && need_fix) {
         const auto &fixed_dst = replace_match_groups(destination, *ctx._fqdn_wildcard_captured_groups);
-        ssl_netvc->set_tunnel_destination(fixed_dst, type);
+        ssl_netvc->set_tunnel_destination(fixed_dst, type, tunnel_prewarm);
         Debug("ssl_sni", "Destination now is [%s], configured [%s], fqdn [%s]", fixed_dst.c_str(), destination.c_str(), servername);
       } else {
-        ssl_netvc->set_tunnel_destination(destination, type);
+        ssl_netvc->set_tunnel_destination(destination, type, tunnel_prewarm);
         Debug("ssl_sni", "Destination now is [%s], fqdn [%s]", destination.c_str(), servername);
       }
 
@@ -202,7 +203,8 @@ class TunnelDestination : public ActionItem
   }
 
   std::string destination;
-  SNIRoutingType type = SNIRoutingType::NONE;
+  SNIRoutingType type                         = SNIRoutingType::NONE;
+  YamlSNIConfig::TunnelPreWarm tunnel_prewarm = YamlSNIConfig::TunnelPreWarm::UNSET;
   const std::vector<int> &alpn_ids;
   bool need_fix;
 };

iocore/net/P_SSLNetVConnection.h

@@ -298,11 +298,13 @@ class SSLNetVConnection : public UnixNetVConnection,
   bool decrypt_tunnel() const;
   bool upstream_tls() const;
   SNIRoutingType tunnel_type() const;
+  YamlSNIConfig::TunnelPreWarm tunnel_prewarm() const;
 
   void
-  set_tunnel_destination(const std::string_view &destination, SNIRoutingType type)
+  set_tunnel_destination(const std::string_view &destination, SNIRoutingType type, YamlSNIConfig::TunnelPreWarm prewarm)
   {
-    _tunnel_type = type;
+    _tunnel_type    = type;
+    _tunnel_prewarm = prewarm;
 
     auto pos = destination.find(":");
     if (nullptr != tunnel_host) {
@@ -484,10 +486,13 @@ class SSLNetVConnection : public UnixNetVConnection,
     HANDSHAKE_HOOKS_DONE
   } sslHandshakeHookState = HANDSHAKE_HOOKS_PRE;
 
-  int64_t redoWriteSize       = 0;
-  char *tunnel_host           = nullptr;
-  in_port_t tunnel_port       = 0;
-  SNIRoutingType _tunnel_type = SNIRoutingType::NONE;
+  int64_t redoWriteSize = 0;
+
+  char *tunnel_host                            = nullptr;
+  in_port_t tunnel_port                        = 0;
+  SNIRoutingType _tunnel_type                  = SNIRoutingType::NONE;
+  YamlSNIConfig::TunnelPreWarm _tunnel_prewarm = YamlSNIConfig::TunnelPreWarm::UNSET;
+
   X509_STORE_CTX *verify_cert = nullptr;
 
   // Null-terminated string, or nullptr if there is no SNI server name.
@@ -521,6 +526,12 @@ SSLNetVConnection::tunnel_type() const
   return _tunnel_type;
 }
 
+inline YamlSNIConfig::TunnelPreWarm
+SSLNetVConnection::tunnel_prewarm() const
+{
+  return _tunnel_prewarm;
+}
+
 /**
    Returns true if this vc was configured for forward_route or partial_blind_route
  */

iocore/net/SSLSNIConfig.cc

@@ -30,6 +30,9 @@
  ****************************************************************************/
 
 #include "P_SSLSNI.h"
+
+#include "PreWarmManager.h"
+
 #include "tscore/Diags.h"
 #include "tscore/SimpleTokenizer.h"
 #include "tscore/ink_memory.h"
@@ -77,7 +80,8 @@ SNIConfigParams::loadSNIConfig()
       ai->actions.push_back(std::make_unique<TLSValidProtocols>(item.protocol_mask));
     }
     if (item.tunnel_destination.length() > 0) {
-      ai->actions.push_back(std::make_unique<TunnelDestination>(item.tunnel_destination, item.tunnel_type, item.tunnel_alpn));
+      ai->actions.push_back(
+        std::make_unique<TunnelDestination>(item.tunnel_destination, item.tunnel_type, item.tunnel_prewarm, item.tunnel_alpn));
     }
     if (!item.client_sni_policy.empty()) {
       ai->actions.push_back(std::make_unique<OutboundSNIPolicy>(item.client_sni_policy));
@@ -200,6 +204,8 @@ SNIConfig::reconfigure()
 
   params->Initialize();
   configid = configProcessor.set(configid, params);
+
+  prewarmManager.reconfigure();
 }
 
 SNIConfigParams *