http2: add range support for respondWith{File|FD}

* respondWithFD now supports optional statCheck
* respondWithFD and respondWithFile both support offset/length for
  range requests
* Fix linting nits following most recent update

Backport-PR-URL: #14813
Backport-Reviewed-By: Anna Henningsen <anna@addaleax.net>
Backport-Reviewed-By: Timothy Gu <timothygu99@gmail.com>

PR-URL: #14239
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

Author: jasnell

doc/api/http2.md

@@ -998,13 +998,17 @@ server.on('stream', (stream) => {
 });
 ```
 
-#### http2stream.respondWithFD(fd[, headers])
+#### http2stream.respondWithFD(fd[, headers[, options]])
 <!-- YAML
 added: REPLACEME
 -->
 
 * `fd` {number} A readable file descriptor
 * `headers` {[Headers Object][]}
+* `options` {Object}
+  * `statCheck` {Function}
+  * `offset` {number} The offset position at which to begin reading
+  * `length` {number} The amount of data from the fd to send
 
 Initiates a response whose data is read from the given file descriptor. No
 validation is performed on the given file descriptor. If an error occurs while
@@ -1034,6 +1038,16 @@ server.on('stream', (stream) => {
 server.on('close', () => fs.closeSync(fd));
 ```
 
+The optional `options.statCheck` function may be specified to give user code
+an opportunity to set additional content headers based on the `fs.Stat` details
+of the given fd. If the `statCheck` function is provided, the
+`http2stream.respondWithFD()` method will perform an `fs.fstat()` call to
+collect details on the provided file descriptor.
+
+The `offset` and `length` options may be used to limit the response to a
+specific range subset. This can be used, for instance, to support HTTP Range
+requests.
+
 #### http2stream.respondWithFile(path[, headers[, options]])
 <!-- YAML
 added: REPLACEME
@@ -1043,6 +1057,8 @@ added: REPLACEME
 * `headers` {[Headers Object][]}
 * `options` {Object}
   * `statCheck` {Function}
+  * `offset` {number} The offset position at which to begin reading
+  * `length` {number} The amount of data from the fd to send
 
 Sends a regular file as the response. The `path` must specify a regular file
 or an `'error'` event will be emitted on the `Http2Stream` object.
@@ -1096,6 +1112,10 @@ server.on('stream', (stream) => {
 
 The `content-length` header field will be automatically set.
 
+The `offset` and `length` options may be used to limit the response to a
+specific range subset. This can be used, for instance, to support HTTP Range
+requests.
+
 ### Class: Http2Server
 <!-- YAML
 added: REPLACEME

lib/internal/http2/compat.js

@@ -452,7 +452,7 @@ class Http2ServerResponse extends Stream {
       stream.once('finish', cb);
     }
 
-    this[kBeginSend]({endStream: true});
+    this[kBeginSend]({ endStream: true });
 
     if (stream !== undefined) {
       stream.end();

lib/internal/http2/core.js

@@ -1541,7 +1541,7 @@ function processHeaders(headers) {
   return headers;
 }
 
-function processRespondWithFD(fd, headers) {
+function processRespondWithFD(fd, headers, offset = 0, length = -1) {
   const session = this[kSession];
   const state = this[kState];
   state.headersSent = true;
@@ -1551,7 +1551,7 @@ function processRespondWithFD(fd, headers) {
 
   const handle = session[kHandle];
   const ret =
-    handle.submitFile(this[kID], fd, headers);
+    handle.submitFile(this[kID], fd, headers, offset, length);
   let err;
   switch (ret) {
     case NGHTTP2_ERR_NOMEM:
@@ -1575,26 +1575,71 @@ function doSendFD(session, options, fd, headers, err, stat) {
     process.nextTick(() => this.emit('error', err));
     return;
   }
+
+  const statOptions = {
+    offset: options.offset !== undefined ? options.offset : 0,
+    length: options.length !== undefined ? options.length : -1
+  };
+
+  if (typeof options.statCheck === 'function' &&
+      options.statCheck.call(this, stat, headers, statOptions) === false) {
+    return;
+  }
+
+  const headersList = mapToHeaders(headers,
+                                   assertValidPseudoHeaderResponse);
+  if (!Array.isArray(headersList)) {
+    process.nextTick(() => this.emit('error', headersList));
+  }
+
+  processRespondWithFD.call(this, fd, headersList,
+                            statOptions.offset,
+                            statOptions.length);
+}
+
+function doSendFileFD(session, options, fd, headers, err, stat) {
+  if (this.destroyed || session.destroyed) {
+    abort(this);
+    return;
+  }
+  if (err) {
+    process.nextTick(() => this.emit('error', err));
+    return;
+  }
   if (!stat.isFile()) {
     err = new errors.Error('ERR_HTTP2_SEND_FILE');
     process.nextTick(() => this.emit('error', err));
     return;
   }
 
+  const statOptions = {
+    offset: options.offset !== undefined ? options.offset : 0,
+    length: options.length !== undefined ? options.length : -1
+  };
+
   // Set the content-length by default
-  headers[HTTP2_HEADER_CONTENT_LENGTH] = stat.size;
   if (typeof options.statCheck === 'function' &&
       options.statCheck.call(this, stat, headers) === false) {
     return;
   }
 
+  statOptions.length =
+    statOptions.length < 0 ? stat.size - (+statOptions.offset) :
+                             Math.min(stat.size - (+statOptions.offset),
+                                      statOptions.length);
+
+  if (headers[HTTP2_HEADER_CONTENT_LENGTH] === undefined)
+    headers[HTTP2_HEADER_CONTENT_LENGTH] = statOptions.length;
+
   const headersList = mapToHeaders(headers,
                                    assertValidPseudoHeaderResponse);
   if (!Array.isArray(headersList)) {
-    throw headersList;
+    process.nextTick(() => this.emit('error', headersList));
   }
 
-  processRespondWithFD.call(this, fd, headersList);
+  processRespondWithFD.call(this, fd, headersList,
+                            options.offset,
+                            options.length);
 }
 
 function afterOpen(session, options, headers, err, fd) {
@@ -1609,7 +1654,7 @@ function afterOpen(session, options, headers, err, fd) {
   }
   state.fd = fd;
 
-  fs.fstat(fd, doSendFD.bind(this, session, options, fd, headers));
+  fs.fstat(fd, doSendFileFD.bind(this, session, options, fd, headers));
 }
 
 
@@ -1786,12 +1831,12 @@ class ServerHttp2Stream extends Http2Stream {
   }
 
   // Initiate a response using an open FD. Note that there are fewer
-  // protections with this approach. For one, the fd is not validated.
-  // In respondWithFile, the file is checked to make sure it is a
+  // protections with this approach. For one, the fd is not validated by
+  // default. In respondWithFile, the file is checked to make sure it is a
   // regular file, here the fd is passed directly. If the underlying
   // mechanism is not able to read from the fd, then the stream will be
   // reset with an error code.
-  respondWithFD(fd, headers) {
+  respondWithFD(fd, headers, options) {
     const session = this[kSession];
     if (this.destroyed)
       throw new errors.Error('ERR_HTTP2_INVALID_STREAM');
@@ -1803,6 +1848,26 @@ class ServerHttp2Stream extends Http2Stream {
     if (state.headersSent)
       throw new errors.Error('ERR_HTTP2_HEADERS_SENT');
 
+    assertIsObject(options, 'options');
+    options = Object.assign(Object.create(null), options);
+
+    if (options.offset !== undefined && typeof options.offset !== 'number')
+      throw new errors.TypeError('ERR_INVALID_OPT_VALUE',
+                                 'offset',
+                                 options.offset);
+
+    if (options.length !== undefined && typeof options.length !== 'number')
+      throw new errors.TypeError('ERR_INVALID_OPT_VALUE',
+                                 'length',
+                                options.length);
+
+    if (options.statCheck !== undefined &&
+        typeof options.statCheck !== 'function') {
+      throw new errors.TypeError('ERR_INVALID_OPT_VALUE',
+                                 'statCheck',
+                                 options.statCheck);
+    }
+
     if (typeof fd !== 'number')
       throw new errors.TypeError('ERR_INVALID_ARG_TYPE',
                                  'fd', 'number');
@@ -1816,13 +1881,20 @@ class ServerHttp2Stream extends Http2Stream {
       throw new errors.Error('ERR_HTTP2_PAYLOAD_FORBIDDEN', statusCode);
     }
 
+    if (options.statCheck !== undefined) {
+      fs.fstat(fd, doSendFD.bind(this, session, options, fd, headers));
+      return;
+    }
+
     const headersList = mapToHeaders(headers,
                                      assertValidPseudoHeaderResponse);
     if (!Array.isArray(headersList)) {
-      throw headersList;
+      process.nextTick(() => this.emit('error', headersList));
     }
 
-    processRespondWithFD.call(this, fd, headersList);
+    processRespondWithFD.call(this, fd, headersList,
+                              options.offset,
+                              options.length);
   }
 
   // Initiate a file response on this Http2Stream. The path is passed to
@@ -1847,6 +1919,16 @@ class ServerHttp2Stream extends Http2Stream {
     assertIsObject(options, 'options');
     options = Object.assign(Object.create(null), options);
 
+    if (options.offset !== undefined && typeof options.offset !== 'number')
+      throw new errors.TypeError('ERR_INVALID_OPT_VALUE',
+                                 'offset',
+                                 options.offset);
+
+    if (options.length !== undefined && typeof options.length !== 'number')
+      throw new errors.TypeError('ERR_INVALID_OPT_VALUE',
+                                 'length',
+                                options.length);
+
     if (options.statCheck !== undefined &&
         typeof options.statCheck !== 'function') {
       throw new errors.TypeError('ERR_INVALID_OPT_VALUE',

src/node_http2.cc

@@ -604,7 +604,9 @@ void Http2Session::SubmitResponse(const FunctionCallbackInfo<Value>& args) {
 void Http2Session::SubmitFile(const FunctionCallbackInfo<Value>& args) {
   CHECK(args[0]->IsNumber());  // Stream ID
   CHECK(args[1]->IsNumber());  // File Descriptor
-  CHECK(args[2]->IsArray());  // Headers
+  CHECK(args[2]->IsArray());   // Headers
+  CHECK(args[3]->IsNumber());  // Offset
+  CHECK(args[4]->IsNumber());  // Length
 
   Http2Session* session;
   Nghttp2Stream* stream;
@@ -618,6 +620,11 @@ void Http2Session::SubmitFile(const FunctionCallbackInfo<Value>& args) {
   int fd = args[1]->Int32Value(context).ToChecked();
   Local<Array> headers = args[2].As<Array>();
 
+  int64_t offset = args[3]->IntegerValue(context).ToChecked();
+  int64_t length = args[4]->IntegerValue(context).ToChecked();
+
+  CHECK_GE(offset, 0);
+
   DEBUG_HTTP2("Http2Session: submitting file %d for stream %d: headers: %d, "
               "end-stream: %d\n", fd, id, headers->Length());
 
@@ -627,7 +634,8 @@ void Http2Session::SubmitFile(const FunctionCallbackInfo<Value>& args) {
 
   Headers list(isolate, context, headers);
 
-  args.GetReturnValue().Set(stream->SubmitFile(fd, *list, list.length()));
+  args.GetReturnValue().Set(stream->SubmitFile(fd, *list, list.length(),
+                                               offset, length));
 }
 
 void Http2Session::SendHeaders(const FunctionCallbackInfo<Value>& args) {

src/node_http2_core-inl.h

@@ -429,7 +429,10 @@ inline int Nghttp2Stream::SubmitResponse(nghttp2_nv* nva,
 }
 
 // Initiate a response that contains data read from a file descriptor.
-inline int Nghttp2Stream::SubmitFile(int fd, nghttp2_nv* nva, size_t len) {
+inline int Nghttp2Stream::SubmitFile(int fd,
+                                     nghttp2_nv* nva, size_t len,
+                                     int64_t offset,
+                                     int64_t length) {
   CHECK_GT(len, 0);
   CHECK_GT(fd, 0);
   DEBUG_HTTP2("Nghttp2Stream %d: submitting file\n", id_);
@@ -438,6 +441,9 @@ inline int Nghttp2Stream::SubmitFile(int fd, nghttp2_nv* nva, size_t len) {
   prov.source.fd = fd;
   prov.read_callback = Nghttp2Session::OnStreamReadFD;
 
+  if (offset > 0) fd_offset_ = offset;
+  if (length > -1) fd_length_ = length;
+
   return nghttp2_submit_response(session_->session(), id_,
                                  nva, len, &prov);
 }

src/node_http2_core.cc

@@ -180,28 +180,36 @@ ssize_t Nghttp2Session::OnStreamReadFD(nghttp2_session* session,
 
   int fd = source->fd;
   int64_t offset = stream->fd_offset_;
-  ssize_t numchars;
+  ssize_t numchars = 0;
+
+  if (stream->fd_length_ >= 0 &&
+      stream->fd_length_ < static_cast<int64_t>(length))
+    length = stream->fd_length_;
 
   uv_buf_t data;
   data.base = reinterpret_cast<char*>(buf);
   data.len = length;
 
   uv_fs_t read_req;
-  numchars = uv_fs_read(handle->loop_,
-                        &read_req,
-                        fd, &data, 1,
-                        offset, nullptr);
-  uv_fs_req_cleanup(&read_req);
+
+  if (length > 0) {
+    numchars = uv_fs_read(handle->loop_,
+                          &read_req,
+                          fd, &data, 1,
+                          offset, nullptr);
+    uv_fs_req_cleanup(&read_req);
+  }
 
   // Close the stream with an error if reading fails
   if (numchars < 0)
     return NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE;
 
   // Update the read offset for the next read
   stream->fd_offset_ += numchars;
+  stream->fd_length_ -= numchars;
 
   // if numchars < length, assume that we are done.
-  if (static_cast<size_t>(numchars) < length) {
+  if (static_cast<size_t>(numchars) < length || length <= 0) {
     DEBUG_HTTP2("Nghttp2Session %d: no more data for stream %d\n",
                 handle->session_type_, id);
     *flags |= NGHTTP2_DATA_FLAG_EOF;

src/node_http2_core.h

@@ -310,7 +310,10 @@ class Nghttp2Stream {
                             bool emptyPayload = false);
 
   // Send data read from a file descriptor as the response on this stream.
-  inline int SubmitFile(int fd, nghttp2_nv* nva, size_t len);
+  inline int SubmitFile(int fd,
+                        nghttp2_nv* nva, size_t len,
+                        int64_t offset,
+                        int64_t length);
 
   // Submit informational headers for this stream
   inline int SubmitInfo(nghttp2_nv* nva, size_t len);
@@ -420,7 +423,8 @@ class Nghttp2Stream {
   nghttp2_stream_write_queue* queue_tail_ = nullptr;
   unsigned int queue_head_index_ = 0;
   size_t queue_head_offset_ = 0;
-  size_t fd_offset_ = 0;
+  int64_t fd_offset_ = 0;
+  int64_t fd_length_ = -1;
 
   // The Current Headers block... As headers are received for this stream,
   // they are temporarily stored here until the OnFrameReceived is called