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@@ -0,0 +1 @@ +See README.rst diff --git a/README.rst b/README.rst new file mode 100644 index 0000000..6871a60 --- /dev/null +++ b/README.rst @@ -0,0 +1,1475 @@ +nghttp2 - HTTP/2 C Library +========================== + +This is an implementation of the Hypertext Transfer Protocol version 2 +in C. + +The framing layer of HTTP/2 is implemented as a reusable C library. +On top of that, we have implemented an HTTP/2 client, server and +proxy. We have also developed load test and benchmarking tools for +HTTP/2. + +An HPACK encoder and decoder are available as a public API. + +Development Status +------------------ + +nghttp2 was originally developed based on `RFC 7540 +<https://tools.ietf.org/html/rfc7540>`_ HTTP/2 and `RFC 7541 +<https://tools.ietf.org/html/rfc7541>`_ HPACK - Header Compression for +HTTP/2. Now we are updating our code to implement `RFC 9113 +<https://datatracker.ietf.org/doc/html/rfc9113>`_. + +The nghttp2 code base was forked from the spdylay +(https://github.com/tatsuhiro-t/spdylay) project. + +Public Test Server +------------------ + +The following endpoints are available to try out our nghttp2 +implementation. + +* https://nghttp2.org/ (TLS + ALPN/NPN and HTTP/3) + + This endpoint supports ``h2``, ``h2-16``, ``h2-14``, and + ``http/1.1`` via ALPN/NPN and requires TLSv1.2 for HTTP/2 + connection. + + It also supports HTTP/3. + +* http://nghttp2.org/ (HTTP Upgrade and HTTP/2 Direct) + + ``h2c`` and ``http/1.1``. + +Requirements +------------ + +The following package is required to build the libnghttp2 library: + +* pkg-config >= 0.20 + +To build and run the unit test programs, the following package is +required: + +* cunit >= 2.1 + +To build the documentation, you need to install: + +* sphinx (http://sphinx-doc.org/) + +If you need libnghttp2 (C library) only, then the above packages are +all you need. Use ``--enable-lib-only`` to ensure that only +libnghttp2 is built. This avoids potential build error related to +building bundled applications. + +To build and run the application programs (``nghttp``, ``nghttpd``, +``nghttpx`` and ``h2load``) in the ``src`` directory, the following packages +are required: + +* OpenSSL >= 1.0.1 +* libev >= 4.11 +* zlib >= 1.2.3 +* libc-ares >= 1.7.5 + +ALPN support requires OpenSSL >= 1.0.2 (released 22 January 2015). +LibreSSL >= 2.2.0 can be used instead of OpenSSL, but OpenSSL has more +features than LibreSSL at the time of this writing. + +To enable ``-a`` option (getting linked assets from the downloaded +resource) in ``nghttp``, the following package is required: + +* libxml2 >= 2.6.26 + +To enable systemd support in nghttpx, the following package is +required: + +* libsystemd-dev >= 209 + +The HPACK tools require the following package: + +* jansson >= 2.5 + +To build sources under the examples directory, libevent is required: + +* libevent-openssl >= 2.0.8 + +To mitigate heap fragmentation in long running server programs +(``nghttpd`` and ``nghttpx``), jemalloc is recommended: + +* jemalloc + + .. note:: + + Alpine Linux currently does not support malloc replacement + due to musl limitations. See details in issue `#762 <https://github.com/nghttp2/nghttp2/issues/762>`_. + +To enable mruby support for nghttpx, `mruby +<https://github.com/mruby/mruby>`_ is required. We need to build +mruby with C++ ABI explicitly turned on, and probably need other +mrgems, mruby is manged by git submodule under third-party/mruby +directory. Currently, mruby support for nghttpx is disabled by +default. To enable mruby support, use ``--with-mruby`` configure +option. Note that at the time of this writing, libmruby-dev and mruby +packages in Debian/Ubuntu are not usable for nghttp2, since they do +not enable C++ ABI. To build mruby, the following packages are +required: + +* ruby +* bison + +nghttpx supports `neverbleed <https://github.com/h2o/neverbleed>`_, +privilege separation engine for OpenSSL / LibreSSL. In short, it +minimizes the risk of private key leakage when serious bug like +Heartbleed is exploited. The neverbleed is disabled by default. To +enable it, use ``--with-neverbleed`` configure option. + +To enable the experimental HTTP/3 support for h2load and nghttpx, the +following libraries are required: + +* `OpenSSL with QUIC support + <https://github.com/quictls/openssl/tree/OpenSSL_1_1_1t+quic>`_; or + `BoringSSL <https://boringssl.googlesource.com/boringssl/>`_ (commit + 80a243e07ef77156af66efa7d22ac35aba44c1b3) +* `ngtcp2 <https://github.com/ngtcp2/ngtcp2>`_ >= 0.13.0 +* `nghttp3 <https://github.com/ngtcp2/nghttp3>`_ >= 0.7.0 + +Use ``--enable-http3`` configure option to enable HTTP/3 feature for +h2load and nghttpx. + +In order to build optional eBPF program to direct an incoming QUIC UDP +datagram to a correct socket for nghttpx, the following libraries are +required: + +* libbpf-dev >= 0.7.0 + +Use ``--with-libbpf`` configure option to build eBPF program. +libelf-dev is needed to build libbpf. + +For Ubuntu 20.04, you can build libbpf from `the source code +<https://github.com/libbpf/libbpf/releases/tag/v1.1.0>`_. nghttpx +requires eBPF program for reloading its configuration and hot swapping +its executable. + +Compiling libnghttp2 C source code requires a C99 compiler. gcc 4.8 +is known to be adequate. In order to compile the C++ source code, gcc +>= 6.0 or clang >= 6.0 is required. C++ source code requires C++14 +language features. + +.. note:: + + To enable mruby support in nghttpx, and use ``--with-mruby`` + configure option. + +.. note:: + + Mac OS X users may need the ``--disable-threads`` configure option to + disable multi-threading in nghttpd, nghttpx and h2load to prevent + them from crashing. A patch is welcome to make multi threading work + on Mac OS X platform. + +.. note:: + + To compile the associated applications (nghttp, nghttpd, nghttpx + and h2load), you must use the ``--enable-app`` configure option and + ensure that the specified requirements above are met. Normally, + configure script checks required dependencies to build these + applications, and enable ``--enable-app`` automatically, so you + don't have to use it explicitly. But if you found that + applications were not built, then using ``--enable-app`` may find + that cause, such as the missing dependency. + +.. note:: + + In order to detect third party libraries, pkg-config is used + (however we don't use pkg-config for some libraries (e.g., libev)). + By default, pkg-config searches ``*.pc`` file in the standard + locations (e.g., /usr/lib/pkgconfig). If it is necessary to use + ``*.pc`` file in the custom location, specify paths to + ``PKG_CONFIG_PATH`` environment variable, and pass it to configure + script, like so: + + .. code-block:: text + + $ ./configure PKG_CONFIG_PATH=/path/to/pkgconfig + + For pkg-config managed libraries, ``*_CFLAG`` and ``*_LIBS`` + environment variables are defined (e.g., ``OPENSSL_CFLAGS``, + ``OPENSSL_LIBS``). Specifying non-empty string to these variables + completely overrides pkg-config. In other words, if they are + specified, pkg-config is not used for detection, and user is + responsible to specify the correct values to these variables. For + complete list of these variables, run ``./configure -h``. + +If you are using Ubuntu 22.04 LTS, run the following to install the +required packages: + +.. code-block:: text + + sudo apt-get install g++ clang make binutils autoconf automake \ + autotools-dev libtool pkg-config \ + zlib1g-dev libcunit1-dev libssl-dev libxml2-dev libev-dev \ + libevent-dev libjansson-dev \ + libc-ares-dev libjemalloc-dev libsystemd-dev \ + ruby-dev bison libelf-dev + +Building nghttp2 from release tar archive +----------------------------------------- + +The nghttp2 project regularly releases tar archives which includes +nghttp2 source code, and generated build files. They can be +downloaded from `Releases +<https://github.com/nghttp2/nghttp2/releases>`_ page. + +Building nghttp2 from git requires autotools development packages. +Building from tar archives does not require them, and thus it is much +easier. The usual build step is as follows: + +.. code-block:: text + + $ tar xf nghttp2-X.Y.Z.tar.bz2 + $ cd nghttp2-X.Y.Z + $ ./configure + $ make + +Building from git +----------------- + +Building from git is easy, but please be sure that at least autoconf 2.68 is +used: + +.. code-block:: text + + $ git submodule update --init + $ autoreconf -i + $ automake + $ autoconf + $ ./configure + $ make + +Notes for building on Windows (MSVC) +------------------------------------ + +The easiest way to build native Windows nghttp2 dll is use `cmake +<https://cmake.org/>`_. The free version of `Visual C++ Build Tools +<http://landinghub.visualstudio.com/visual-cpp-build-tools>`_ works +fine. + +1. Install cmake for windows +2. Open "Visual C++ ... Native Build Tool Command Prompt", and inside + nghttp2 directly, run ``cmake``. +3. Then run ``cmake --build`` to build library. +4. nghttp2.dll, nghttp2.lib, nghttp2.exp are placed under lib directory. + +Note that the above steps most likely produce nghttp2 library only. +No bundled applications are compiled. + +Notes for building on Windows (Mingw/Cygwin) +-------------------------------------------- + +Under Mingw environment, you can only compile the library, it's +``libnghttp2-X.dll`` and ``libnghttp2.a``. + +If you want to compile the applications(``h2load``, ``nghttp``, +``nghttpx``, ``nghttpd``), you need to use the Cygwin environment. + +Under Cygwin environment, to compile the applications you need to +compile and install the libev first. + +Secondly, you need to undefine the macro ``__STRICT_ANSI__``, if you +not, the functions ``fdopen``, ``fileno`` and ``strptime`` will not +available. + +the sample command like this: + +.. code-block:: text + + $ export CFLAGS="-U__STRICT_ANSI__ -I$libev_PREFIX/include -L$libev_PREFIX/lib" + $ export CXXFLAGS=$CFLAGS + $ ./configure + $ make + +If you want to compile the applications under ``examples/``, you need +to remove or rename the ``event.h`` from libev's installation, because +it conflicts with libevent's installation. + +Notes for installation on Linux systems +-------------------------------------------- +After installing nghttp2 tool suite with ``make install`` one might experience a similar error: + +.. code-block:: text + + nghttpx: error while loading shared libraries: libnghttp2.so.14: cannot open shared object file: No such file or directory + +This means that the tool is unable to locate the ``libnghttp2.so`` shared library. + +To update the shared library cache run ``sudo ldconfig``. + +Building the documentation +-------------------------- + +.. note:: + + Documentation is still incomplete. + +To build the documentation, run: + +.. code-block:: text + + $ make html + +The documents will be generated under ``doc/manual/html/``. + +The generated documents will not be installed with ``make install``. + +The online documentation is available at +https://nghttp2.org/documentation/ + +Build HTTP/3 enabled h2load and nghttpx +--------------------------------------- + +To build h2load and nghttpx with HTTP/3 feature enabled, run the +configure script with ``--enable-http3``. + +For nghttpx to reload configurations and swapping its executable while +gracefully terminating old worker processes, eBPF is required. Run +the configure script with ``--enable-http3 --with-libbpf`` to build +eBPF program. The QUIC keying material must be set with +``--frontend-quic-secret-file`` in order to keep the existing +connections alive during reload. + +The detailed steps to build HTTP/3 enabled h2load and nghttpx follow. + +Build custom OpenSSL: + +.. code-block:: text + + $ git clone --depth 1 -b OpenSSL_1_1_1t+quic https://github.com/quictls/openssl + $ cd openssl + $ ./config --prefix=$PWD/build --openssldir=/etc/ssl + $ make -j$(nproc) + $ make install_sw + $ cd .. + +Build nghttp3: + +.. code-block:: text + + $ git clone --depth 1 -b v0.8.0 https://github.com/ngtcp2/nghttp3 + $ cd nghttp3 + $ autoreconf -i + $ ./configure --prefix=$PWD/build --enable-lib-only + $ make -j$(nproc) + $ make install + $ cd .. + +Build ngtcp2: + +.. code-block:: text + + $ git clone --depth 1 -b v0.13.1 https://github.com/ngtcp2/ngtcp2 + $ cd ngtcp2 + $ autoreconf -i + $ ./configure --prefix=$PWD/build --enable-lib-only \ + PKG_CONFIG_PATH="$PWD/../openssl/build/lib/pkgconfig" + $ make -j$(nproc) + $ make install + $ cd .. + +If your Linux distribution does not have libbpf-dev >= 0.7.0, build +from source: + +.. code-block:: text + + $ git clone --depth 1 -b v1.1.0 https://github.com/libbpf/libbpf + $ cd libbpf + $ PREFIX=$PWD/build make -C src install + $ cd .. + +Build nghttp2: + +.. code-block:: text + + $ git clone https://github.com/nghttp2/nghttp2 + $ cd nghttp2 + $ git submodule update --init + $ autoreconf -i + $ ./configure --with-mruby --with-neverbleed --enable-http3 --with-libbpf \ + CC=clang-14 CXX=clang++-14 \ + PKG_CONFIG_PATH="$PWD/../openssl/build/lib/pkgconfig:$PWD/../nghttp3/build/lib/pkgconfig:$PWD/../ngtcp2/build/lib/pkgconfig:$PWD/../libbpf/build/lib64/pkgconfig" \ + LDFLAGS="$LDFLAGS -Wl,-rpath,$PWD/../openssl/build/lib -Wl,-rpath,$PWD/../libbpf/build/lib64" + $ make -j$(nproc) + +The eBPF program ``reuseport_kern.o`` should be found under bpf +directory. Pass ``--quic-bpf-program-file=bpf/reuseport_kern.o`` +option to nghttpx to load it. See also `HTTP/3 section in nghttpx - +HTTP/2 proxy - HOW-TO +<https://nghttp2.org/documentation/nghttpx-howto.html#http-3>`_. + +Unit tests +---------- + +Unit tests are done by simply running ``make check``. + +Integration tests +----------------- + +We have the integration tests for the nghttpx proxy server. The tests are +written in the `Go programming language <http://golang.org/>`_ and uses +its testing framework. We depend on the following libraries: + +* golang.org/x/net/http2 +* golang.org/x/net/websocket +* https://github.com/tatsuhiro-t/go-nghttp2 + +Go modules will download these dependencies automatically. + +To run the tests, run the following command under +``integration-tests`` directory: + +.. code-block:: text + + $ make it + +Inside the tests, we use port 3009 to run the test subject server. + +Migration from v0.7.15 or earlier +--------------------------------- + +nghttp2 v1.0.0 introduced several backward incompatible changes. In +this section, we describe these changes and how to migrate to v1.0.0. + +ALPN protocol ID is now ``h2`` and ``h2c`` +++++++++++++++++++++++++++++++++++++++++++ + +Previously we announced ``h2-14`` and ``h2c-14``. v1.0.0 implements +final protocol version, and we changed ALPN ID to ``h2`` and ``h2c``. +The macros ``NGHTTP2_PROTO_VERSION_ID``, +``NGHTTP2_PROTO_VERSION_ID_LEN``, +``NGHTTP2_CLEARTEXT_PROTO_VERSION_ID``, and +``NGHTTP2_CLEARTEXT_PROTO_VERSION_ID_LEN`` have been updated to +reflect this change. + +Basically, existing applications do not have to do anything, just +recompiling is enough for this change. + +Use word "client magic" where we use "client connection preface" +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ + +We use "client connection preface" to mean first 24 bytes of client +connection preface. This is technically not correct, since client +connection preface is composed of 24 bytes client magic byte string +followed by SETTINGS frame. For clarification, we call "client magic" +for this 24 bytes byte string and updated API. + +* ``NGHTTP2_CLIENT_CONNECTION_PREFACE`` was replaced with + ``NGHTTP2_CLIENT_MAGIC``. +* ``NGHTTP2_CLIENT_CONNECTION_PREFACE_LEN`` was replaced with + ``NGHTTP2_CLIENT_MAGIC_LEN``. +* ``NGHTTP2_BAD_PREFACE`` was renamed as ``NGHTTP2_BAD_CLIENT_MAGIC`` + +The already deprecated ``NGHTTP2_CLIENT_CONNECTION_HEADER`` and +``NGHTTP2_CLIENT_CONNECTION_HEADER_LEN`` were removed. + +If application uses these macros, just replace old ones with new ones. +Since v1.0.0, client magic is sent by library (see next subsection), +so client application may just remove these macro use. + +Client magic is sent by library ++++++++++++++++++++++++++++++++ + +Previously nghttp2 library did not send client magic, which is first +24 bytes byte string of client connection preface, and client +applications have to send it by themselves. Since v1.0.0, client +magic is sent by library via first call of ``nghttp2_session_send()`` +or ``nghttp2_session_mem_send()``. + +The client applications which send client magic must remove the +relevant code. + +Remove HTTP Alternative Services (Alt-Svc) related code ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ + +Alt-Svc specification is not finalized yet. To make our API stable, +we have decided to remove all Alt-Svc related API from nghttp2. + +* ``NGHTTP2_EXT_ALTSVC`` was removed. +* ``nghttp2_ext_altsvc`` was removed. + +We have already removed the functionality of Alt-Svc in v0.7 series +and they have been essentially noop. The application using these +macro and struct, remove those lines. + +Use nghttp2_error in nghttp2_on_invalid_frame_recv_callback ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ + +Previously ``nghttp2_on_invalid_frame_recv_cb_called`` took the +``error_code``, defined in ``nghttp2_error_code``, as parameter. But +they are not detailed enough to debug. Therefore, we decided to use +more detailed ``nghttp2_error`` values instead. + +The application using this callback should update the callback +signature. If it treats ``error_code`` as HTTP/2 error code, update +the code so that it is treated as ``nghttp2_error``. + +Receive client magic by default ++++++++++++++++++++++++++++++++ + +Previously nghttp2 did not process client magic (24 bytes byte +string). To make it deal with it, we had to use +``nghttp2_option_set_recv_client_preface()``. Since v1.0.0, nghttp2 +processes client magic by default and +``nghttp2_option_set_recv_client_preface()`` was removed. + +Some application may want to disable this behaviour, so we added +``nghttp2_option_set_no_recv_client_magic()`` to achieve this. + +The application using ``nghttp2_option_set_recv_client_preface()`` +with nonzero value, just remove it. + +The application using ``nghttp2_option_set_recv_client_preface()`` +with zero value or not using it must use +``nghttp2_option_set_no_recv_client_magic()`` with nonzero value. + +Client, Server and Proxy programs +--------------------------------- + +The ``src`` directory contains the HTTP/2 client, server and proxy programs. + +nghttp - client ++++++++++++++++ + +``nghttp`` is a HTTP/2 client. It can connect to the HTTP/2 server +with prior knowledge, HTTP Upgrade and NPN/ALPN TLS extension. + +It has verbose output mode for framing information. Here is sample +output from ``nghttp`` client: + +.. code-block:: text + + $ nghttp -nv https://nghttp2.org + [ 0.190] Connected + The negotiated protocol: h2 + [ 0.212] recv SETTINGS frame <length=12, flags=0x00, stream_id=0> + (niv=2) + [SETTINGS_MAX_CONCURRENT_STREAMS(0x03):100] + [SETTINGS_INITIAL_WINDOW_SIZE(0x04):65535] + [ 0.212] send SETTINGS frame <length=12, flags=0x00, stream_id=0> + (niv=2) + [SETTINGS_MAX_CONCURRENT_STREAMS(0x03):100] + [SETTINGS_INITIAL_WINDOW_SIZE(0x04):65535] + [ 0.212] send SETTINGS frame <length=0, flags=0x01, stream_id=0> + ; ACK + (niv=0) + [ 0.212] send PRIORITY frame <length=5, flags=0x00, stream_id=3> + (dep_stream_id=0, weight=201, exclusive=0) + [ 0.212] send PRIORITY frame <length=5, flags=0x00, stream_id=5> + (dep_stream_id=0, weight=101, exclusive=0) + [ 0.212] send PRIORITY frame <length=5, flags=0x00, stream_id=7> + (dep_stream_id=0, weight=1, exclusive=0) + [ 0.212] send PRIORITY frame <length=5, flags=0x00, stream_id=9> + (dep_stream_id=7, weight=1, exclusive=0) + [ 0.212] send PRIORITY frame <length=5, flags=0x00, stream_id=11> + (dep_stream_id=3, weight=1, exclusive=0) + [ 0.212] send HEADERS frame <length=39, flags=0x25, stream_id=13> + ; END_STREAM | END_HEADERS | PRIORITY + (padlen=0, dep_stream_id=11, weight=16, exclusive=0) + ; Open new stream + :method: GET + :path: / + :scheme: https + :authority: nghttp2.org + accept: */* + accept-encoding: gzip, deflate + user-agent: nghttp2/1.0.1-DEV + [ 0.221] recv SETTINGS frame <length=0, flags=0x01, stream_id=0> + ; ACK + (niv=0) + [ 0.221] recv (stream_id=13) :method: GET + [ 0.221] recv (stream_id=13) :scheme: https + [ 0.221] recv (stream_id=13) :path: /stylesheets/screen.css + [ 0.221] recv (stream_id=13) :authority: nghttp2.org + [ 0.221] recv (stream_id=13) accept-encoding: gzip, deflate + [ 0.222] recv (stream_id=13) user-agent: nghttp2/1.0.1-DEV + [ 0.222] recv PUSH_PROMISE frame <length=50, flags=0x04, stream_id=13> + ; END_HEADERS + (padlen=0, promised_stream_id=2) + [ 0.222] recv (stream_id=13) :status: 200 + [ 0.222] recv (stream_id=13) date: Thu, 21 May 2015 16:38:14 GMT + [ 0.222] recv (stream_id=13) content-type: text/html + [ 0.222] recv (stream_id=13) last-modified: Fri, 15 May 2015 15:38:06 GMT + [ 0.222] recv (stream_id=13) etag: W/"555612de-19f6" + [ 0.222] recv (stream_id=13) link: </stylesheets/screen.css>; rel=preload; as=stylesheet + [ 0.222] recv (stream_id=13) content-encoding: gzip + [ 0.222] recv (stream_id=13) server: nghttpx nghttp2/1.0.1-DEV + [ 0.222] recv (stream_id=13) via: 1.1 nghttpx + [ 0.222] recv (stream_id=13) strict-transport-security: max-age=31536000 + [ 0.222] recv HEADERS frame <length=166, flags=0x04, stream_id=13> + ; END_HEADERS + (padlen=0) + ; First response header + [ 0.222] recv DATA frame <length=2601, flags=0x01, stream_id=13> + ; END_STREAM + [ 0.222] recv (stream_id=2) :status: 200 + [ 0.222] recv (stream_id=2) date: Thu, 21 May 2015 16:38:14 GMT + [ 0.222] recv (stream_id=2) content-type: text/css + [ 0.222] recv (stream_id=2) last-modified: Fri, 15 May 2015 15:38:06 GMT + [ 0.222] recv (stream_id=2) etag: W/"555612de-9845" + [ 0.222] recv (stream_id=2) content-encoding: gzip + [ 0.222] recv (stream_id=2) server: nghttpx nghttp2/1.0.1-DEV + [ 0.222] recv (stream_id=2) via: 1.1 nghttpx + [ 0.222] recv (stream_id=2) strict-transport-security: max-age=31536000 + [ 0.222] recv HEADERS frame <length=32, flags=0x04, stream_id=2> + ; END_HEADERS + (padlen=0) + ; First push response header + [ 0.228] recv DATA frame <length=8715, flags=0x01, stream_id=2> + ; END_STREAM + [ 0.228] send GOAWAY frame <length=8, flags=0x00, stream_id=0> + (last_stream_id=2, error_code=NO_ERROR(0x00), opaque_data(0)=[]) + +The HTTP Upgrade is performed like so: + +.. code-block:: text + + $ nghttp -nvu http://nghttp2.org + [ 0.011] Connected + [ 0.011] HTTP Upgrade request + GET / HTTP/1.1 + Host: nghttp2.org + Connection: Upgrade, HTTP2-Settings + Upgrade: h2c + HTTP2-Settings: AAMAAABkAAQAAP__ + Accept: */* + User-Agent: nghttp2/1.0.1-DEV + + + [ 0.018] HTTP Upgrade response + HTTP/1.1 101 Switching Protocols + Connection: Upgrade + Upgrade: h2c + + + [ 0.018] HTTP Upgrade success + [ 0.018] recv SETTINGS frame <length=12, flags=0x00, stream_id=0> + (niv=2) + [SETTINGS_MAX_CONCURRENT_STREAMS(0x03):100] + [SETTINGS_INITIAL_WINDOW_SIZE(0x04):65535] + [ 0.018] send SETTINGS frame <length=12, flags=0x00, stream_id=0> + (niv=2) + [SETTINGS_MAX_CONCURRENT_STREAMS(0x03):100] + [SETTINGS_INITIAL_WINDOW_SIZE(0x04):65535] + [ 0.018] send SETTINGS frame <length=0, flags=0x01, stream_id=0> + ; ACK + (niv=0) + [ 0.018] send PRIORITY frame <length=5, flags=0x00, stream_id=3> + (dep_stream_id=0, weight=201, exclusive=0) + [ 0.018] send PRIORITY frame <length=5, flags=0x00, stream_id=5> + (dep_stream_id=0, weight=101, exclusive=0) + [ 0.018] send PRIORITY frame <length=5, flags=0x00, stream_id=7> + (dep_stream_id=0, weight=1, exclusive=0) + [ 0.018] send PRIORITY frame <length=5, flags=0x00, stream_id=9> + (dep_stream_id=7, weight=1, exclusive=0) + [ 0.018] send PRIORITY frame <length=5, flags=0x00, stream_id=11> + (dep_stream_id=3, weight=1, exclusive=0) + [ 0.018] send PRIORITY frame <length=5, flags=0x00, stream_id=1> + (dep_stream_id=11, weight=16, exclusive=0) + [ 0.019] recv (stream_id=1) :method: GET + [ 0.019] recv (stream_id=1) :scheme: http + [ 0.019] recv (stream_id=1) :path: /stylesheets/screen.css + [ 0.019] recv (stream_id=1) host: nghttp2.org + [ 0.019] recv (stream_id=1) user-agent: nghttp2/1.0.1-DEV + [ 0.019] recv PUSH_PROMISE frame <length=49, flags=0x04, stream_id=1> + ; END_HEADERS + (padlen=0, promised_stream_id=2) + [ 0.019] recv (stream_id=1) :status: 200 + [ 0.019] recv (stream_id=1) date: Thu, 21 May 2015 16:39:16 GMT + [ 0.019] recv (stream_id=1) content-type: text/html + [ 0.019] recv (stream_id=1) content-length: 6646 + [ 0.019] recv (stream_id=1) last-modified: Fri, 15 May 2015 15:38:06 GMT + [ 0.019] recv (stream_id=1) etag: "555612de-19f6" + [ 0.019] recv (stream_id=1) link: </stylesheets/screen.css>; rel=preload; as=stylesheet + [ 0.019] recv (stream_id=1) accept-ranges: bytes + [ 0.019] recv (stream_id=1) server: nghttpx nghttp2/1.0.1-DEV + [ 0.019] recv (stream_id=1) via: 1.1 nghttpx + [ 0.019] recv HEADERS frame <length=157, flags=0x04, stream_id=1> + ; END_HEADERS + (padlen=0) + ; First response header + [ 0.019] recv DATA frame <length=6646, flags=0x01, stream_id=1> + ; END_STREAM + [ 0.019] recv (stream_id=2) :status: 200 + [ 0.019] recv (stream_id=2) date: Thu, 21 May 2015 16:39:16 GMT + [ 0.019] recv (stream_id=2) content-type: text/css + [ 0.019] recv (stream_id=2) content-length: 38981 + [ 0.019] recv (stream_id=2) last-modified: Fri, 15 May 2015 15:38:06 GMT + [ 0.019] recv (stream_id=2) etag: "555612de-9845" + [ 0.019] recv (stream_id=2) accept-ranges: bytes + [ 0.019] recv (stream_id=2) server: nghttpx nghttp2/1.0.1-DEV + [ 0.019] recv (stream_id=2) via: 1.1 nghttpx + [ 0.019] recv HEADERS frame <length=36, flags=0x04, stream_id=2> + ; END_HEADERS + (padlen=0) + ; First push response header + [ 0.026] recv DATA frame <length=16384, flags=0x00, stream_id=2> + [ 0.027] recv DATA frame <length=7952, flags=0x00, stream_id=2> + [ 0.027] send WINDOW_UPDATE frame <length=4, flags=0x00, stream_id=0> + (window_size_increment=33343) + [ 0.032] send WINDOW_UPDATE frame <length=4, flags=0x00, stream_id=2> + (window_size_increment=33707) + [ 0.032] recv DATA frame <length=14645, flags=0x01, stream_id=2> + ; END_STREAM + [ 0.032] recv SETTINGS frame <length=0, flags=0x01, stream_id=0> + ; ACK + (niv=0) + [ 0.032] send GOAWAY frame <length=8, flags=0x00, stream_id=0> + (last_stream_id=2, error_code=NO_ERROR(0x00), opaque_data(0)=[]) + +Using the ``-s`` option, ``nghttp`` prints out some timing information for +requests, sorted by completion time: + +.. code-block:: text + + $ nghttp -nas https://nghttp2.org/ + ***** Statistics ***** + + Request timing: + responseEnd: the time when last byte of response was received + relative to connectEnd + requestStart: the time just before first byte of request was sent + relative to connectEnd. If '*' is shown, this was + pushed by server. + process: responseEnd - requestStart + code: HTTP status code + size: number of bytes received as response body without + inflation. + URI: request URI + + see http://www.w3.org/TR/resource-timing/#processing-model + + sorted by 'complete' + + id responseEnd requestStart process code size request path + 13 +37.19ms +280us 36.91ms 200 2K / + 2 +72.65ms * +36.38ms 36.26ms 200 8K /stylesheets/screen.css + 17 +77.43ms +38.67ms 38.75ms 200 3K /javascripts/octopress.js + 15 +78.12ms +38.66ms 39.46ms 200 3K /javascripts/modernizr-2.0.js + +Using the ``-r`` option, ``nghttp`` writes more detailed timing data to +the given file in HAR format. + +nghttpd - server +++++++++++++++++ + +``nghttpd`` is a multi-threaded static web server. + +By default, it uses SSL/TLS connection. Use ``--no-tls`` option to +disable it. + +``nghttpd`` only accepts HTTP/2 connections via NPN/ALPN or direct +HTTP/2 connections. No HTTP Upgrade is supported. + +The ``-p`` option allows users to configure server push. + +Just like ``nghttp``, it has a verbose output mode for framing +information. Here is sample output from ``nghttpd``: + +.. code-block:: text + + $ nghttpd --no-tls -v 8080 + IPv4: listen 0.0.0.0:8080 + IPv6: listen :::8080 + [id=1] [ 1.521] send SETTINGS frame <length=6, flags=0x00, stream_id=0> + (niv=1) + [SETTINGS_MAX_CONCURRENT_STREAMS(0x03):100] + [id=1] [ 1.521] recv SETTINGS frame <length=12, flags=0x00, stream_id=0> + (niv=2) + [SETTINGS_MAX_CONCURRENT_STREAMS(0x03):100] + [SETTINGS_INITIAL_WINDOW_SIZE(0x04):65535] + [id=1] [ 1.521] recv SETTINGS frame <length=0, flags=0x01, stream_id=0> + ; ACK + (niv=0) + [id=1] [ 1.521] recv PRIORITY frame <length=5, flags=0x00, stream_id=3> + (dep_stream_id=0, weight=201, exclusive=0) + [id=1] [ 1.521] recv PRIORITY frame <length=5, flags=0x00, stream_id=5> + (dep_stream_id=0, weight=101, exclusive=0) + [id=1] [ 1.521] recv PRIORITY frame <length=5, flags=0x00, stream_id=7> + (dep_stream_id=0, weight=1, exclusive=0) + [id=1] [ 1.521] recv PRIORITY frame <length=5, flags=0x00, stream_id=9> + (dep_stream_id=7, weight=1, exclusive=0) + [id=1] [ 1.521] recv PRIORITY frame <length=5, flags=0x00, stream_id=11> + (dep_stream_id=3, weight=1, exclusive=0) + [id=1] [ 1.521] recv (stream_id=13) :method: GET + [id=1] [ 1.521] recv (stream_id=13) :path: / + [id=1] [ 1.521] recv (stream_id=13) :scheme: http + [id=1] [ 1.521] recv (stream_id=13) :authority: localhost:8080 + [id=1] [ 1.521] recv (stream_id=13) accept: */* + [id=1] [ 1.521] recv (stream_id=13) accept-encoding: gzip, deflate + [id=1] [ 1.521] recv (stream_id=13) user-agent: nghttp2/1.0.0-DEV + [id=1] [ 1.521] recv HEADERS frame <length=41, flags=0x25, stream_id=13> + ; END_STREAM | END_HEADERS | PRIORITY + (padlen=0, dep_stream_id=11, weight=16, exclusive=0) + ; Open new stream + [id=1] [ 1.521] send SETTINGS frame <length=0, flags=0x01, stream_id=0> + ; ACK + (niv=0) + [id=1] [ 1.521] send HEADERS frame <length=86, flags=0x04, stream_id=13> + ; END_HEADERS + (padlen=0) + ; First response header + :status: 200 + server: nghttpd nghttp2/1.0.0-DEV + content-length: 10 + cache-control: max-age=3600 + date: Fri, 15 May 2015 14:49:04 GMT + last-modified: Tue, 30 Sep 2014 12:40:52 GMT + [id=1] [ 1.522] send DATA frame <length=10, flags=0x01, stream_id=13> + ; END_STREAM + [id=1] [ 1.522] stream_id=13 closed + [id=1] [ 1.522] recv GOAWAY frame <length=8, flags=0x00, stream_id=0> + (last_stream_id=0, error_code=NO_ERROR(0x00), opaque_data(0)=[]) + [id=1] [ 1.522] closed + +nghttpx - proxy ++++++++++++++++ + +``nghttpx`` is a multi-threaded reverse proxy for HTTP/3, HTTP/2, and +HTTP/1.1, and powers http://nghttp2.org and supports HTTP/2 server +push. + +We reworked ``nghttpx`` command-line interface, and as a result, there +are several incompatibles from 1.8.0 or earlier. This is necessary to +extend its capability, and secure the further feature enhancements in +the future release. Please read `Migration from nghttpx v1.8.0 or +earlier +<https://nghttp2.org/documentation/nghttpx-howto.html#migration-from-nghttpx-v1-8-0-or-earlier>`_ +to know how to migrate from earlier releases. + +``nghttpx`` implements `important performance-oriented features +<https://istlsfastyet.com/#server-performance>`_ in TLS, such as +session IDs, session tickets (with automatic key rotation), OCSP +stapling, dynamic record sizing, ALPN/NPN, forward secrecy and HTTP/2. +``nghttpx`` also offers the functionality to share session cache and +ticket keys among multiple ``nghttpx`` instances via memcached. + +``nghttpx`` has 2 operation modes: + +================== ======================== ================ ============= +Mode option Frontend Backend Note +================== ======================== ================ ============= +default mode HTTP/3, HTTP/2, HTTP/1.1 HTTP/1.1, HTTP/2 Reverse proxy +``--http2-proxy`` HTTP/3, HTTP/2, HTTP/1.1 HTTP/1.1, HTTP/2 Forward proxy +================== ======================== ================ ============= + +The interesting mode at the moment is the default mode. It works like +a reverse proxy and listens for HTTP/3, HTTP/2, and HTTP/1.1 and can +be deployed as a SSL/TLS terminator for existing web server. + +In all modes, the frontend connections are encrypted by SSL/TLS by +default. To disable encryption, use the ``no-tls`` keyword in +``--frontend`` option. If encryption is disabled, incoming HTTP/1.1 +connections can be upgraded to HTTP/2 through HTTP Upgrade. On the +other hard, backend connections are not encrypted by default. To +encrypt backend connections, use ``tls`` keyword in ``--backend`` +option. + +``nghttpx`` supports a configuration file. See the ``--conf`` option and +sample configuration file ``nghttpx.conf.sample``. + +In the default mode, ``nghttpx`` works as reverse proxy to the backend +server: + +.. code-block:: text + + Client <-- (HTTP/3, HTTP/2, HTTP/1.1) --> nghttpx <-- (HTTP/1.1, HTTP/2) --> Web Server + [reverse proxy] + +With the ``--http2-proxy`` option, it works as forward proxy, and it +is so called secure HTTP/2 proxy: + +.. code-block:: text + + Client <-- (HTTP/3, HTTP/2, HTTP/1.1) --> nghttpx <-- (HTTP/1.1) --> Proxy + [secure proxy] (e.g., Squid, ATS) + +The ``Client`` in the above example needs to be configured to use +``nghttpx`` as secure proxy. + +At the time of this writing, both Chrome and Firefox support secure +HTTP/2 proxy. One way to configure Chrome to use a secure proxy is to +create a proxy.pac script like this: + +.. code-block:: javascript + + function FindProxyForURL(url, host) { + return "HTTPS SERVERADDR:PORT"; + } + +``SERVERADDR`` and ``PORT`` is the hostname/address and port of the +machine nghttpx is running on. Please note that Chrome requires a valid +certificate for secure proxy. + +Then run Chrome with the following arguments: + +.. code-block:: text + + $ google-chrome --proxy-pac-url=file:///path/to/proxy.pac --use-npn + +The backend HTTP/2 connections can be tunneled through an HTTP proxy. +The proxy is specified using ``--backend-http-proxy-uri``. The +following figure illustrates how nghttpx talks to the outside HTTP/2 +proxy through an HTTP proxy: + +.. code-block:: text + + Client <-- (HTTP/3, HTTP/2, HTTP/1.1) --> nghttpx <-- (HTTP/2) -- + + --===================---> HTTP/2 Proxy + (HTTP proxy tunnel) (e.g., nghttpx -s) + +Benchmarking tool +----------------- + +The ``h2load`` program is a benchmarking tool for HTTP/3, HTTP/2, and +HTTP/1.1. The UI of ``h2load`` is heavily inspired by ``weighttp`` +(https://github.com/lighttpd/weighttp). The typical usage is as +follows: + +.. code-block:: text + + $ h2load -n100000 -c100 -m100 https://localhost:8443/ + starting benchmark... + spawning thread #0: 100 concurrent clients, 100000 total requests + Protocol: TLSv1.2 + Cipher: ECDHE-RSA-AES128-GCM-SHA256 + Server Temp Key: ECDH P-256 256 bits + progress: 10% done + progress: 20% done + progress: 30% done + progress: 40% done + progress: 50% done + progress: 60% done + progress: 70% done + progress: 80% done + progress: 90% done + progress: 100% done + + finished in 771.26ms, 129658 req/s, 4.71MB/s + requests: 100000 total, 100000 started, 100000 done, 100000 succeeded, 0 failed, 0 errored + status codes: 100000 2xx, 0 3xx, 0 4xx, 0 5xx + traffic: 3812300 bytes total, 1009900 bytes headers, 1000000 bytes data + min max mean sd +/- sd + time for request: 25.12ms 124.55ms 51.07ms 15.36ms 84.87% + time for connect: 208.94ms 254.67ms 241.38ms 7.95ms 63.00% + time to 1st byte: 209.11ms 254.80ms 241.51ms 7.94ms 63.00% + +The above example issued total 100,000 requests, using 100 concurrent +clients (in other words, 100 HTTP/2 sessions), and a maximum of 100 streams +per client. With the ``-t`` option, ``h2load`` will use multiple native +threads to avoid saturating a single core on client side. + +.. warning:: + + **Don't use this tool against publicly available servers.** That is + considered a DOS attack. Please only use it against your private + servers. + +If the experimental HTTP/3 is enabled, h2load can send requests to +HTTP/3 server. To do this, specify ``h3`` to ``--npn-list`` option +like so: + +.. code-block:: text + + $ h2load --npn-list h3 https://127.0.0.1:4433 + +HPACK tools +----------- + +The ``src`` directory contains the HPACK tools. The ``deflatehd`` program is a +command-line header compression tool. The ``inflatehd`` program is a +command-line header decompression tool. Both tools read input from +stdin and write output to stdout. Errors are written to stderr. +They take JSON as input and output. We (mostly) use the same JSON data +format described at https://github.com/http2jp/hpack-test-case. + +deflatehd - header compressor ++++++++++++++++++++++++++++++ + +The ``deflatehd`` program reads JSON data or HTTP/1-style header fields from +stdin and outputs compressed header block in JSON. + +For the JSON input, the root JSON object must include a ``cases`` key. +Its value has to include the sequence of input header set. They share +the same compression context and are processed in the order they +appear. Each item in the sequence is a JSON object and it must +include a ``headers`` key. Its value is an array of JSON objects, +which includes exactly one name/value pair. + +Example: + +.. code-block:: json + + { + "cases": + [ + { + "headers": [ + { ":method": "GET" }, + { ":path": "/" } + ] + }, + { + "headers": [ + { ":method": "POST" }, + { ":path": "/" } + ] + } + ] + } + + +With the ``-t`` option, the program can accept more familiar HTTP/1 style +header field blocks. Each header set is delimited by an empty line: + +Example: + +.. code-block:: text + + :method: GET + :scheme: https + :path: / + + :method: POST + user-agent: nghttp2 + +The output is in JSON object. It should include a ``cases`` key and its +value is an array of JSON objects, which has at least the following keys: + +seq + The index of header set in the input. + +input_length + The sum of the length of the name/value pairs in the input. + +output_length + The length of the compressed header block. + +percentage_of_original_size + ``output_length`` / ``input_length`` * 100 + +wire + The compressed header block as a hex string. + +headers + The input header set. + +header_table_size + The header table size adjusted before deflating the header set. + +Examples: + +.. code-block:: json + + { + "cases": + [ + { + "seq": 0, + "input_length": 66, + "output_length": 20, + "percentage_of_original_size": 30.303030303030305, + "wire": "01881f3468e5891afcbf83868a3d856659c62e3f", + "headers": [ + { + ":authority": "example.org" + }, + { + ":method": "GET" + }, + { + ":path": "/" + }, + { + ":scheme": "https" + }, + { + "user-agent": "nghttp2" + } + ], + "header_table_size": 4096 + } + , + { + "seq": 1, + "input_length": 74, + "output_length": 10, + "percentage_of_original_size": 13.513513513513514, + "wire": "88448504252dd5918485", + "headers": [ + { + ":authority": "example.org" + }, + { + ":method": "POST" + }, + { + ":path": "/account" + }, + { + ":scheme": "https" + }, + { + "user-agent": "nghttp2" + } + ], + "header_table_size": 4096 + } + ] + } + + +The output can be used as the input for ``inflatehd`` and +``deflatehd``. + +With the ``-d`` option, the extra ``header_table`` key is added and its +associated value includes the state of dynamic header table after the +corresponding header set was processed. The value includes at least +the following keys: + +entries + The entry in the header table. If ``referenced`` is ``true``, it + is in the reference set. The ``size`` includes the overhead (32 + bytes). The ``index`` corresponds to the index of header table. + The ``name`` is the header field name and the ``value`` is the + header field value. + +size + The sum of the spaces entries occupied, this includes the + entry overhead. + +max_size + The maximum header table size. + +deflate_size + The sum of the spaces entries occupied within + ``max_deflate_size``. + +max_deflate_size + The maximum header table size the encoder uses. This can be smaller + than ``max_size``. In this case, the encoder only uses up to first + ``max_deflate_size`` buffer. Since the header table size is still + ``max_size``, the encoder has to keep track of entries outside the + ``max_deflate_size`` but inside the ``max_size`` and make sure + that they are no longer referenced. + +Example: + +.. code-block:: json + + { + "cases": + [ + { + "seq": 0, + "input_length": 66, + "output_length": 20, + "percentage_of_original_size": 30.303030303030305, + "wire": "01881f3468e5891afcbf83868a3d856659c62e3f", + "headers": [ + { + ":authority": "example.org" + }, + { + ":method": "GET" + }, + { + ":path": "/" + }, + { + ":scheme": "https" + }, + { + "user-agent": "nghttp2" + } + ], + "header_table_size": 4096, + "header_table": { + "entries": [ + { + "index": 1, + "name": "user-agent", + "value": "nghttp2", + "referenced": true, + "size": 49 + }, + { + "index": 2, + "name": ":scheme", + "value": "https", + "referenced": true, + "size": 44 + }, + { + "index": 3, + "name": ":path", + "value": "/", + "referenced": true, + "size": 38 + }, + { + "index": 4, + "name": ":method", + "value": "GET", + "referenced": true, + "size": 42 + }, + { + "index": 5, + "name": ":authority", + "value": "example.org", + "referenced": true, + "size": 53 + } + ], + "size": 226, + "max_size": 4096, + "deflate_size": 226, + "max_deflate_size": 4096 + } + } + , + { + "seq": 1, + "input_length": 74, + "output_length": 10, + "percentage_of_original_size": 13.513513513513514, + "wire": "88448504252dd5918485", + "headers": [ + { + ":authority": "example.org" + }, + { + ":method": "POST" + }, + { + ":path": "/account" + }, + { + ":scheme": "https" + }, + { + "user-agent": "nghttp2" + } + ], + "header_table_size": 4096, + "header_table": { + "entries": [ + { + "index": 1, + "name": ":method", + "value": "POST", + "referenced": true, + "size": 43 + }, + { + "index": 2, + "name": "user-agent", + "value": "nghttp2", + "referenced": true, + "size": 49 + }, + { + "index": 3, + "name": ":scheme", + "value": "https", + "referenced": true, + "size": 44 + }, + { + "index": 4, + "name": ":path", + "value": "/", + "referenced": false, + "size": 38 + }, + { + "index": 5, + "name": ":method", + "value": "GET", + "referenced": false, + "size": 42 + }, + { + "index": 6, + "name": ":authority", + "value": "example.org", + "referenced": true, + "size": 53 + } + ], + "size": 269, + "max_size": 4096, + "deflate_size": 269, + "max_deflate_size": 4096 + } + } + ] + } + +inflatehd - header decompressor ++++++++++++++++++++++++++++++++ + +The ``inflatehd`` program reads JSON data from stdin and outputs decompressed +name/value pairs in JSON. + +The root JSON object must include the ``cases`` key. Its value has to +include the sequence of compressed header blocks. They share the same +compression context and are processed in the order they appear. Each +item in the sequence is a JSON object and it must have at least a +``wire`` key. Its value is a compressed header block as a hex string. + +Example: + +.. code-block:: json + + { + "cases": + [ + { "wire": "8285" }, + { "wire": "8583" } + ] + } + +The output is a JSON object. It should include a ``cases`` key and its +value is an array of JSON objects, which has at least following keys: + +seq + The index of the header set in the input. + +headers + A JSON array that includes decompressed name/value pairs. + +wire + The compressed header block as a hex string. + +header_table_size + The header table size adjusted before inflating compressed header + block. + +Example: + +.. code-block:: json + + { + "cases": + [ + { + "seq": 0, + "wire": "01881f3468e5891afcbf83868a3d856659c62e3f", + "headers": [ + { + ":authority": "example.org" + }, + { + ":method": "GET" + }, + { + ":path": "/" + }, + { + ":scheme": "https" + }, + { + "user-agent": "nghttp2" + } + ], + "header_table_size": 4096 + } + , + { + "seq": 1, + "wire": "88448504252dd5918485", + "headers": [ + { + ":method": "POST" + }, + { + ":path": "/account" + }, + { + "user-agent": "nghttp2" + }, + { + ":scheme": "https" + }, + { + ":authority": "example.org" + } + ], + "header_table_size": 4096 + } + ] + } + +The output can be used as the input for ``deflatehd`` and +``inflatehd``. + +With the ``-d`` option, the extra ``header_table`` key is added and its +associated value includes the state of the dynamic header table after the +corresponding header set was processed. The format is the same as +``deflatehd``. + +Contribution +------------ + +[This text was composed based on 1.2. License section of curl/libcurl +project.] + +When contributing with code, you agree to put your changes and new +code under the same license nghttp2 is already using unless stated and +agreed otherwise. + +When changing existing source code, do not alter the copyright of +the original file(s). The copyright will still be owned by the +original creator(s) or those who have been assigned copyright by the +original author(s). + +By submitting a patch to the nghttp2 project, you (or your employer, as +the case may be) agree to assign the copyright of your submission to us. +.. the above really needs to be reworded to pass legal muster. +We will credit you for your +changes as far as possible, to give credit but also to keep a trace +back to who made what changes. Please always provide us with your +full real name when contributing! + +See `Contribution Guidelines +<https://nghttp2.org/documentation/contribute.html>`_ for more +details. + +Reporting vulnerability +----------------------- + +If you find a vulnerability in our software, please send the email to +"tatsuhiro.t at gmail dot com" about its details instead of submitting +issues on github issue page. It is a standard practice not to +disclose vulnerability information publicly until a fixed version is +released, or mitigation is worked out. + +In the future, we may setup a dedicated mail address for this purpose. + +Release schedule +---------------- + +In general, we follow `Semantic Versioning <http://semver.org/>`_. We +release MINOR version update every month, and usually we ship it +around 25th day of every month. + +We may release PATCH releases between the regular releases, mainly for +severe security bug fixes. + +We have no plan to break API compatibility changes involving soname +bump, so MAJOR version will stay 1 for the foreseeable future. + +License +------- + +The MIT License |