http2: track memory allocated by nghttp2

Provide a custom memory allocator for nghttp2, and track
memory allocated by the library with it.
This makes the used-memory-per-session estimate more
accurate, and allows us to track memory leaks either
in nghttp2 itself or, more likely, through faulty
usage on our end.
It also allows us to make the per-session memory limit
more accurate in the future; currently, we are not
handling this in an ideal way, and instead let nghttp2
allocate what it wants, even if that goes over our limit.
PR-URL: #21374
Refs: #21373
Refs: #21336
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>

Author: addaleax

src/node_http2.cc

@@ -451,6 +451,92 @@ Http2Session::Callbacks::~Callbacks() {
 nghttp2_session_callbacks_del(callbacks);
 }
 
+// Track memory allocated by nghttp2 using a custom allocator.
+classHttp2Session::MemoryAllocatorInfo {
+public:
+explicitMemoryAllocatorInfo(Http2Session* session)
+ : info({ session, H2Malloc, H2Free, H2Calloc, H2Realloc }) {}
+
+staticvoid* H2Malloc(size_t size, void* user_data) {
+returnH2Realloc(nullptr, size, user_data);
+ }
+
+staticvoid* H2Calloc(size_t nmemb, size_t size, void* user_data) {
+size_t real_size = MultiplyWithOverflowCheck(nmemb, size);
+void* mem = H2Malloc(real_size, user_data);
+if (mem != nullptr)
+memset(mem, 0, real_size);
+return mem;
+ }
+
+staticvoidH2Free(void* ptr, void* user_data) {
+if (ptr == nullptr) return; // free(null); happens quite often.
+void* result = H2Realloc(ptr, 0, user_data);
+CHECK_EQ(result, nullptr);
+ }
+
+staticvoid* H2Realloc(void* ptr, size_t size, void* user_data) {
+ Http2Session* session = static_cast<Http2Session*>(user_data);
+size_t previous_size = 0;
+char* original_ptr = nullptr;
+
+// We prepend each allocated buffer with a size_t containing the full
+// size of the allocation.
+if (size > 0) size += sizeof(size_t);
+
+if (ptr != nullptr) {
+// We are free()ing or re-allocating.
+ original_ptr = static_cast<char*>(ptr) - sizeof(size_t);
+ previous_size = *reinterpret_cast<size_t*>(original_ptr);
+// This means we called StopTracking() on this pointer before.
+if (previous_size == 0) {
+// Fall back to the standard Realloc() function.
+char* ret = UncheckedRealloc(original_ptr, size);
+if (ret != nullptr)
+ ret += sizeof(size_t);
+return ret;
+ }
+ }
+CHECK_GE(session->current_nghttp2_memory_, previous_size);
+
+// TODO(addaleax): Add the following, and handle NGHTTP2_ERR_NOMEM properly
+// everywhere:
+//
+// if (size > previous_size &&
+// !session->IsAvailableSessionMemory(size - previous_size)) {
+// return nullptr;
+//}
+
+char* mem = UncheckedRealloc(original_ptr, size);
+
+if (mem != nullptr) {
+// Adjust the memory info counter.
+ session->current_nghttp2_memory_ += size - previous_size;
+ *reinterpret_cast<size_t*>(mem) = size;
+ mem += sizeof(size_t);
+ } elseif (size == 0) {
+ session->current_nghttp2_memory_ -= previous_size;
+ }
+
+return mem;
+ }
+
+staticvoidStopTracking(Http2Session* session, void* ptr) {
+size_t* original_ptr = reinterpret_cast<size_t*>(
+static_cast<char*>(ptr) - sizeof(size_t));
+ session->current_nghttp2_memory_ -= *original_ptr;
+ *original_ptr = 0;
+ }
+
+inline nghttp2_mem* operator*() { return &info; }
+
+ nghttp2_mem info;
+};
+
+voidHttp2Session::StopTrackingRcbuf(nghttp2_rcbuf* buf) {
+MemoryAllocatorInfo::StopTracking(this, buf);
+}
+
 Http2Session::Http2Session(Environment* env,
  Local<Object> wrap,
  nghttp2_session_type type)
@@ -482,15 +568,17 @@ Http2Session::Http2Session(Environment* env,
  = callback_struct_saved[hasGetPaddingCallback ? 1 : 0].callbacks;
 
 auto fn = type == NGHTTP2_SESSION_SERVER ?
- nghttp2_session_server_new2 :
- nghttp2_session_client_new2;
+ nghttp2_session_server_new3 :
+ nghttp2_session_client_new3;
+
+ MemoryAllocatorInfo allocator_info(this);
 
 // This should fail only if the system is out of memory, which
 // is going to cause lots of other problems anyway, or if any
 // of the options are out of acceptable range, which we should
 // be catching before it gets this far. Either way, crash if this
 // fails.
-CHECK_EQ(fn(&session_, callbacks, this, *opts), 0);
+CHECK_EQ(fn(&session_, callbacks, this, *opts, *allocator_info), 0);
 
  outgoing_storage_.reserve(4096);
  outgoing_buffers_.reserve(32);
@@ -502,6 +590,7 @@ Http2Session::~Http2Session() {
 for (constauto& stream : streams_)
  stream.second->session_ = nullptr;
 nghttp2_session_del(session_);
+CHECK_EQ(current_nghttp2_memory_, 0);
 }
 
 std::string Http2Session::diagnostic_name() const {
@@ -1150,9 +1239,9 @@ void Http2Session::HandleHeadersFrame(const nghttp2_frame* frame) {
  nghttp2_header item = headers[n++];
 // The header name and value are passed as external one-byte strings
  name_str =
- ExternalHeader::New<true>(env(), item.name).ToLocalChecked();
+ ExternalHeader::New<true>(this, item.name).ToLocalChecked();
  value_str =
- ExternalHeader::New<false>(env(), item.value).ToLocalChecked();
+ ExternalHeader::New<false>(this, item.value).ToLocalChecked();
  argv[j * 2] = name_str;
  argv[j * 2 + 1] = value_str;
  j++;

src/node_http2.h

@@ -721,6 +721,7 @@ class Http2Session : public AsyncWrap, public StreamListener {
 
 classHttp2Ping;
 classHttp2Settings;
+classMemoryAllocatorInfo;
 
 voidEmitStatistics();
 
@@ -849,13 +850,15 @@ class Http2Session : public AsyncWrap, public StreamListener {
  current_session_memory_ -= amount;
  }
 
-// Returns the current session memory including the current size of both
-// the inflate and deflate hpack headers, the current outbound storage
-// queue, and pending writes.
+// Tell our custom memory allocator that this rcbuf is independent of
+// this session now, and may outlive it.
+voidStopTrackingRcbuf(nghttp2_rcbuf* buf);
+
+// Returns the current session memory including memory allocated by nghttp2,
+// the current outbound storage queue, and pending writes.
 uint64_tGetCurrentSessionMemory() {
 uint64_t total = current_session_memory_ + sizeof(Http2Session);
- total += nghttp2_session_get_hd_deflate_dynamic_table_size(session_);
- total += nghttp2_session_get_hd_inflate_dynamic_table_size(session_);
+ total += current_nghttp2_memory_;
  total += outgoing_storage_.size();
 return total;
  }
@@ -987,6 +990,8 @@ class Http2Session : public AsyncWrap, public StreamListener {
 // The maximum amount of memory allocated for this session
 uint64_t max_session_memory_ = DEFAULT_MAX_SESSION_MEMORY;
 uint64_t current_session_memory_ = 0;
+// The amount of memory allocated by nghttp2 internals
+uint64_t current_nghttp2_memory_ = 0;
 
 // The collection of active Http2Streams associated with this session
  std::unordered_map<int32_t, Http2Stream*> streams_;
@@ -1178,7 +1183,8 @@ class ExternalHeader :
  }
 
 template <bool may_internalize>
-static MaybeLocal<String> New(Environment* env, nghttp2_rcbuf* buf) {
+static MaybeLocal<String> New(Http2Session* session, nghttp2_rcbuf* buf) {
+ Environment* env = session->env();
 if (nghttp2_rcbuf_is_static(buf)) {
 auto& static_str_map = env->isolate_data()->http2_static_strs;
  v8::Eternal<v8::String>& eternal = static_str_map[buf];
@@ -1205,6 +1211,7 @@ class ExternalHeader :
 returnGetInternalizedString(env, vec);
  }
 
+ session->StopTrackingRcbuf(buf);
  ExternalHeader* h_str = newExternalHeader(buf);
  MaybeLocal<String> str = String::NewExternalOneByte(env->isolate(), h_str);
 if (str.IsEmpty())

src/util-inl.h

@@ -320,8 +320,9 @@ bool StringEqualNoCaseN(const char* a, const char* b, size_t length) {
 returntrue;
 }
 
-inlinesize_tMultiplyWithOverflowCheck(size_t a, size_t b) {
-size_t ret = a * b;
+template <typename T>
+inline T MultiplyWithOverflowCheck(T a, T b) {
+auto ret = a * b;
 if (a != 0)
 CHECK_EQ(b, ret / a);
 

src/util.h

@@ -67,6 +67,9 @@ inline char* Calloc(size_t n);
 inlinechar* UncheckedMalloc(size_t n);
 inlinechar* UncheckedCalloc(size_t n);
 
+template <typename T>
+inline T MultiplyWithOverflowCheck(T a, T b);
+
 // Used by the allocation functions when allocation fails.
 // Thin wrapper around v8::Isolate::LowMemoryNotification() that checks
 // whether V8 is initialized.