Add HTTP/3 documentation

README.rst

@@ -159,6 +159,11 @@ required:
 
 * libbpf-dev >= 0.4.0
 
+For Ubuntu 20.04, you can build libbpf from `the source code
+<https://github.com/libbpf/libbpf/releases/tag/v0.4.0>`_.  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
@@ -897,6 +902,17 @@ like so:
 
     $ h2load --npn-list h3 https://127.0.0.1:4433
 
+HTTP/3
+------
+
+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.
+
 HPACK tools
 -----------
 

doc/sources/h2load-howto.rst

@@ -131,3 +131,12 @@ specify ``unix:`` followed by the path to UNIX domain socket.  For
 example, if UNIX domain socket is ``/tmp/nghttpx.sock``, use
 ``--base-uri=unix:/tmp/nghttpx.sock``.  h2load uses scheme, host and
 port in the first URI in command-line or input file.
+
+HTTP/3
+------
+
+h2load supports HTTP/3 if it is built with HTTP/3 enabled.  HTTP/3
+support is experimental.
+
+In order to send HTTP/3 request, specify ``h3`` to
+:option:`--npn-list`.

doc/sources/nghttpx-howto.rst

@@ -509,6 +509,37 @@ Bootstrapping WebSockets with HTTP/2 for both frontend and backend
 connections.  This feature is enabled by default and no configuration
 is required.
 
+HTTP/3
+------
+
+nghttpx supports HTTP/3 if it is built with HTTP/3 support enabled.
+HTTP/3 support is experimental.
+
+In order to listen UDP port to receive HTTP/3 traffic,
+:option:`--frontend` option must have ``quic`` parameter:
+
+.. code-block:: text
+
+   frontend=*,443;quic
+
+The above example makes nghttpx receive HTTP/3 traffic on UDP
+port 443.
+
+nghttpx does not support HTTP/3 on backend connection.
+
+Hot swapping (SIGUSR2) or configuration reload (SIGHUP) require eBPF
+program.  Without eBPF, old worker processes keep getting HTTP/3
+traffic and do not work as intended.
+
+In order announce that HTTP/3 endpoint is available, you should
+specify alt-svc header field.  For example, the following options send
+alt-svc header field in HTTP/1.1 and HTTP/2 response:
+
+.. code-block:: text
+
+   altsvc=h3,443,,,ma=3600
+   http2-altsvc=h3,443,,,ma=3600
+
 Migration from nghttpx v1.18.x or earlier
 -----------------------------------------