TS-3535: Experimental Support of Stream Priority Feature in HTTP/2

.gitignore

@@ -87,6 +87,8 @@ iocore/eventsystem/test_Event
 proxy/config/records.config.default
 proxy/config/storage.config.default
 proxy/http2/test_Huffmancode
+proxy/http2/test_Http2DependencyTree
+proxy/http2/test_Http2PriorityQueue
 
 plugins/header_rewrite/header_rewrite_test
 plugins/experimental/esi/*_test

mgmt/RecordsConfig.cc

@@ -1975,6 +1975,8 @@ static const RecordElement RecordsConfig[] =
   //############
   {RECT_CONFIG, "proxy.config.http2.enabled", RECD_INT, "0", RECU_RESTART_TM, RR_NULL, RECC_INT, "[0-1]", RECA_NULL}
   ,
+  {RECT_CONFIG, "proxy.config.http2.stream_priority_enabled", RECD_INT, "0", RECU_RESTART_TM, RR_NULL, RECC_INT, "[0-1]", RECA_NULL}
+  ,
   {RECT_CONFIG, "proxy.config.http2.max_concurrent_streams_in", RECD_INT, "100", RECU_DYNAMIC, RR_NULL, RECC_STR, "^[0-9]+$", RECA_NULL}
   ,
   {RECT_CONFIG, "proxy.config.http2.initial_window_size_in", RECD_INT, "1048576", RECU_DYNAMIC, RR_NULL, RECC_STR, "^[0-9]+$", RECA_NULL}

proxy/FetchSM.h

@@ -129,6 +129,11 @@ class FetchSM : public Continuation
     is_internal_request = val;
   }
 
+  VIO* get_read_vio()
+  {
+    return read_vio;
+  }
+
 private:
   int InvokePlugin(int event, void *data);
   void InvokePluginExt(int error_event = 0);

proxy/http2/HTTP2.cc

@@ -316,15 +316,19 @@ http2_parse_headers_parameter(IOVec iov, Http2HeadersParameter &params)
 }
 
 bool
-http2_parse_priority_parameter(IOVec iov, Http2Priority &params)
+http2_parse_priority_parameter(IOVec iov, Http2Priority &priority)
 {
   byte_pointer ptr(iov.iov_base);
   byte_addressable_value<uint32_t> dependency;
 
   memcpy_and_advance(dependency.bytes, ptr);
-  memcpy_and_advance(params.weight, ptr);
 
-  params.stream_dependency = ntohl(dependency.value);
+  priority.exclusive_flag = dependency.bytes[0] & 0x80;
+
+  dependency.bytes[0] &= 0x7f; // Clear the highest bit for exclusive flag
+  priority.stream_dependency = ntohl(dependency.value);
+
+  memcpy_and_advance(priority.weight, ptr);
 
   return true;
 }
@@ -727,6 +731,7 @@ http2_decode_header_blocks(HTTPHdr *hdr, const uint8_t *buf_start, const uint8_t
 }
 
 // Initialize this subsystem with librecords configs (for now)
+bool Http2::stream_priority_enabled = 0;
 uint32_t Http2::max_concurrent_streams = 100;
 uint32_t Http2::initial_window_size = 1048576;
 uint32_t Http2::max_frame_size = 16384;
@@ -740,6 +745,7 @@ uint32_t Http2::active_timeout_in = 0;
 void
 Http2::init()
 {
+  REC_EstablishStaticConfigBool(stream_priority_enabled, "proxy.config.http2.stream_priority_enabled");
   REC_EstablishStaticConfigInt32U(max_concurrent_streams, "proxy.config.http2.max_concurrent_streams_in");
   REC_EstablishStaticConfigInt32U(initial_window_size, "proxy.config.http2.initial_window_size_in");
   REC_EstablishStaticConfigInt32U(max_frame_size, "proxy.config.http2.max_frame_size");

proxy/http2/HTTP2.h

@@ -60,6 +60,10 @@ const uint32_t HTTP2_MAX_FRAME_SIZE = 16384;
 const uint32_t HTTP2_HEADER_TABLE_SIZE = 4096;
 const uint32_t HTTP2_MAX_HEADER_LIST_SIZE = UINT_MAX;
 
+// [RFC 7540] 5.3.5 Default Priorities
+const uint32_t HTTP2_PRIORITY_DEFAULT_STREAM_DEPENDENCY = 0;
+const uint8_t HTTP2_PRIORITY_DEFAULT_WEIGHT = 15;
+
 // Statistics
 enum {
   HTTP2_STAT_CURRENT_CLIENT_SESSION_COUNT,  // Current # of active HTTP2
@@ -247,10 +251,14 @@ struct Http2SettingsParameter {
 
 // [RFC 7540] 6.3 PRIORITY Format
 struct Http2Priority {
-  Http2Priority() : stream_dependency(0), weight(15) {}
+  Http2Priority()
+    : exclusive_flag(false), weight(HTTP2_PRIORITY_DEFAULT_WEIGHT), stream_dependency(HTTP2_PRIORITY_DEFAULT_STREAM_DEPENDENCY)
+  {
+  }
 
-  uint32_t stream_dependency;
+  bool exclusive_flag;
   uint8_t weight;
+  uint32_t stream_dependency;
 };
 
 // [RFC 7540] 6.2 HEADERS Format
@@ -342,6 +350,7 @@ int64_t http2_write_header_fragment(HTTPHdr *, MIMEFieldIter &, uint8_t *, uint6
 class Http2
 {
 public:
+  static bool stream_priority_enabled;
   static uint32_t max_concurrent_streams;
   static uint32_t initial_window_size;
   static uint32_t max_frame_size;