curl/docs/HTTP3.md

HTTP3 (and QUIC)

Resources

HTTP/3 Explained - the online free book describing the protocols involved.

quicwg.org - home of the official protocol drafts

QUIC libraries

QUIC libraries we are experimenting with:

ngtcp2

quiche

msh3 (with msquic)

Experimental

HTTP/3 and QUIC support in curl is considered EXPERIMENTAL until further notice. It needs to be enabled at build-time.

Further development and tweaking of the HTTP/3 support in curl will happen in the master branch using pull-requests, just like ordinary changes.

To fix before we remove the experimental label:

• working multiplexing and GTFO handling
• fallback or another flexible way to go (back to) h1/h2 if h3 fails
• enough test cases to verify basic HTTP/3 functionality
• no "important" bugs left on HTTP/3
• it's fine to "leave" individual backends as experimental if necessary

ngtcp2 version

Building curl with ngtcp2 involves 3 components: ngtcp2 itself, nghttp3 and a QUIC supporting TLS library. The supported TLS libraries are covered below.

For now, ngtcp2 and nghttp3 are still experimental which means their evolution bring breaking changes. Therefore, the proper version of both libraries need to be used when building curl. These are

• ngtcp2: v0.16.0
• nghttp3: v0.12.0

Build with OpenSSL

Build (patched) OpenSSL

 % git clone --depth 1 -b openssl-3.0.9+quic https://github.com/quictls/openssl
 % cd openssl
 % ./config enable-tls1_3 --prefix=<somewhere1>
 % make
 % make install

Build nghttp3

 % cd ..
 % git clone -b v0.12.0 https://github.com/ngtcp2/nghttp3
 % cd nghttp3
 % autoreconf -fi
 % ./configure --prefix=<somewhere2> --enable-lib-only
 % make
 % make install

Build ngtcp2

 % cd ..
 % git clone -b v0.16.0 https://github.com/ngtcp2/ngtcp2
 % cd ngtcp2
 % autoreconf -fi
 % ./configure PKG_CONFIG_PATH=<somewhere1>/lib/pkgconfig:<somewhere2>/lib/pkgconfig LDFLAGS="-Wl,-rpath,<somewhere1>/lib" --prefix=<somewhere3> --enable-lib-only
 % make
 % make install

Build curl

 % cd ..
 % git clone https://github.com/curl/curl
 % cd curl
 % autoreconf -fi
 % LDFLAGS="-Wl,-rpath,<somewhere1>/lib" ./configure --with-openssl=<somewhere1> --with-nghttp3=<somewhere2> --with-ngtcp2=<somewhere3>
 % make
 % make install

For OpenSSL 3.0.0 or later builds on Linux for x86_64 architecture, substitute all occurrences of "/lib" with "/lib64"

Build with GnuTLS

Build GnuTLS

 % git clone --depth 1 https://gitlab.com/gnutls/gnutls.git
 % cd gnutls
 % ./bootstrap
 % ./configure --prefix=<somewhere1>
 % make
 % make install

Build nghttp3

 % cd ..
 % git clone -b v0.12.0 https://github.com/ngtcp2/nghttp3
 % cd nghttp3
 % autoreconf -fi
 % ./configure --prefix=<somewhere2> --enable-lib-only
 % make
 % make install

Build ngtcp2

 % cd ..
 % git clone -b v0.16.0 https://github.com/ngtcp2/ngtcp2
 % cd ngtcp2
 % autoreconf -fi
 % ./configure PKG_CONFIG_PATH=<somewhere1>/lib/pkgconfig:<somewhere2>/lib/pkgconfig LDFLAGS="-Wl,-rpath,<somewhere1>/lib" --prefix=<somewhere3> --enable-lib-only --with-gnutls
 % make
 % make install

Build curl

 % cd ..
 % git clone https://github.com/curl/curl
 % cd curl
 % autoreconf -fi
 % ./configure --with-gnutls=<somewhere1> --with-nghttp3=<somewhere2> --with-ngtcp2=<somewhere3>
 % make
 % make install

Build with wolfSSL

Build wolfSSL

 % git clone https://github.com/wolfSSL/wolfssl.git
 % cd wolfssl
 % autoreconf -fi
 % ./configure --prefix=<somewhere1> --enable-quic --enable-session-ticket --enable-earlydata --enable-psk --enable-harden --enable-altcertchains
 % make
 % make install

Build nghttp3

 % cd ..
 % git clone -b v0.12.0 https://github.com/ngtcp2/nghttp3
 % cd nghttp3
 % autoreconf -fi
 % ./configure --prefix=<somewhere2> --enable-lib-only
 % make
 % make install

Build ngtcp2

 % cd ..
 % git clone -b v0.16.0 https://github.com/ngtcp2/ngtcp2
 % cd ngtcp2
 % autoreconf -fi
 % ./configure PKG_CONFIG_PATH=<somewhere1>/lib/pkgconfig:<somewhere2>/lib/pkgconfig LDFLAGS="-Wl,-rpath,<somewhere1>/lib" --prefix=<somewhere3> --enable-lib-only --with-wolfssl
 % make
 % make install

Build curl

 % cd ..
 % git clone https://github.com/curl/curl
 % cd curl
 % autoreconf -fi
 % ./configure --with-wolfssl=<somewhere1> --with-nghttp3=<somewhere2> --with-ngtcp2=<somewhere3>
 % make
 % make install

quiche version

Since the quiche build manages its dependencies, curl can be built against the latest version. You are probably able to build against their main branch, but in case of problems, we recommend their latest release tag.

build

Build quiche and BoringSSL:

 % git clone --recursive https://github.com/cloudflare/quiche
 % cd quiche
 % cargo build --package quiche --release --features ffi,pkg-config-meta,qlog
 % mkdir quiche/deps/boringssl/src/lib
 % ln -vnf $(find target/release -name libcrypto.a -o -name libssl.a) quiche/deps/boringssl/src/lib/

Build curl:

 % cd ..
 % git clone https://github.com/curl/curl
 % cd curl
 % autoreconf -fi
 % ./configure LDFLAGS="-Wl,-rpath,$PWD/../quiche/target/release" --with-openssl=$PWD/../quiche/quiche/deps/boringssl/src --with-quiche=$PWD/../quiche/target/release
 % make
 % make install

If make install results in Permission denied error, you will need to prepend it with sudo.

msh3 (msquic) version

Build Linux (with quictls fork of OpenSSL)

Build msh3:

 % git clone -b v0.6.0 --depth 1 --recursive https://github.com/nibanks/msh3
 % cd msh3 && mkdir build && cd build
 % cmake -G 'Unix Makefiles' -DCMAKE_BUILD_TYPE=RelWithDebInfo ..
 % cmake --build .
 % cmake --install .

Build curl:

 % git clone https://github.com/curl/curl
 % cd curl
 % autoreconf -fi
 % ./configure LDFLAGS="-Wl,-rpath,/usr/local/lib" --with-msh3=/usr/local --with-openssl
 % make
 % make install

Run from /usr/local/bin/curl.

Build Windows

Build msh3:

 % git clone -b v0.6.0 --depth 1 --recursive https://github.com/nibanks/msh3
 % cd msh3 && mkdir build && cd build
 % cmake -G 'Visual Studio 17 2022' -DCMAKE_BUILD_TYPE=RelWithDebInfo ..
 % cmake --build . --config Release
 % cmake --install . --config Release

Note - On Windows, Schannel will be used for TLS support by default. If you with to use (the quictls fork of) OpenSSL, specify the -DQUIC_TLS=openssl option to the generate command above. Also note that OpenSSL brings with it an additional set of build dependencies not specified here.

Build curl (in Visual Studio Command prompt):

 % git clone https://github.com/curl/curl
 % cd curl/winbuild
 % nmake /f Makefile.vc mode=dll WITH_MSH3=dll MSH3_PATH="C:/Program Files/msh3" MACHINE=x64

Note - If you encounter a build error with tool_hugehelp.c being missing, rename tool_hugehelp.c.cvs in the same directory to tool_hugehelp.c and then run nmake again.

Run in the C:/Program Files/msh3/lib directory, copy curl.exe to that directory, or copy msquic.dll and msh3.dll from that directory to the curl.exe directory. For example:

 % C:\Program Files\msh3\lib> F:\curl\builds\libcurl-vc-x64-release-dll-ipv6-sspi-schannel-msh3\bin\curl.exe --http3 https://www.google.com

--http3

Use only HTTP/3:

curl --http3-only https://nghttp2.org:4433/

Use HTTP/3 with fallback to HTTP/2 or HTTP/1.1 (see "HTTPS eyeballing" below):

curl --http3 https://nghttp2.org:4433/

Upgrade via Alt-Svc:

curl --alt-svc altsvc.cache https://quic.aiortc.org/

See this list of public HTTP/3 servers

HTTPS eyeballing

With option --http3 curl will attempt earlier HTTP versions as well should the connect attempt via HTTP/3 not succeed "fast enough". This strategy is similar to IPv4/6 happy eyeballing where the alternate address family is used in parallel after a short delay.

The IPv4/6 eyeballing has a default of 200ms and you may override that via --happy-eyeballs-timeout-ms value. Since HTTP/3 is still relatively new, we decided to use this timeout also for the HTTP eyeballing - with a slight twist.

The happy-eyeballs-timeout-ms value is the hard timeout, meaning after that time expired, a TLS connection is opened in addition to negotiate HTTP/2 or HTTP/1.1. At half of that value - currently - is the soft timeout. The soft timeout fires, when there has been no data at all seen from the server on the HTTP/3 connection.

So, without you specifying anything, the hard timeout is 200ms and the soft is 100ms:

• Ideally, the whole QUIC handshake happens and curl has an HTTP/3 connection in less than 100ms.
• When QUIC is not supported (or UDP does not work for this network path), no reply is seen and the HTTP/2 TLS+TCP connection starts 100ms later.
• In the worst case, UDP replies start before 100ms, but drag on. This will start the TLS+TCP connection after 200ms.
• When the QUIC handshake fails, the TLS+TCP connection is attempted right away. For example, when the QUIC server presents the wrong certificate.

The whole transfer only fails, when both QUIC and TLS+TCP fail to handshake or time out.

Note that all this happens in addition to IP version happy eyeballing. If the name resolution for the server gives more than one IP address, curl will try all those until one succeeds - just as with all other protocols. And if those IP addresses contain both IPv6 and IPv4, those attempts will happen, delayed, in parallel (the actual eyeballing).

Known Bugs

Check out the list of known HTTP3 bugs.

HTTP/3 Test server

This is not advice on how to run anything in production. This is for development and experimenting.

Prerequisite(s)

An existing local HTTP/1.1 server that hosts files. Preferably also a few huge ones. You can easily create huge local files like truncate -s=8G 8GB - they are huge but do not occupy that much space on disk since they are just big holes.

In a Debian setup you can install apache2. It runs on port 80 and has a document root in /var/www/html. Download the 8GB file from apache with curl localhost/8GB -o dev/null

In this description we setup and run an HTTP/3 reverse-proxy in front of the HTTP/1 server.

Setup

You can select either or both of these server solutions.

nghttpx

Get, build and install quictls, nghttp3 and ngtcp2 as described above.

Get, build and install nghttp2:

git clone https://github.com/nghttp2/nghttp2.git
cd nghttp2
autoreconf -fi
PKG_CONFIG_PATH=$PKG_CONFIG_PATH:/home/daniel/build-quictls/lib/pkgconfig:/home/daniel/build-nghttp3/lib/pkgconfig:/home/daniel/build-ngtcp2/lib/pkgconfig  LDFLAGS=-L/home/daniel/build-quictls/lib CFLAGS=-I/home/daniel/build-quictls/include ./configure --enable-maintainer-mode --prefix=/home/daniel/build-nghttp2 --disable-shared --enable-app --enable-http3 --without-jemalloc --without-libxml2 --without-systemd
make && make install

Run the local h3 server on port 9443, make it proxy all traffic through to HTTP/1 on localhost port 80. For local toying, we can just use the test cert that exists in curl's test dir.

CERT=$CURLSRC/tests/stunnel.pem
$HOME/bin/nghttpx $CERT $CERT --backend=localhost,80 \
  --frontend="localhost,9443;quic"

Caddy

Install Caddy. For easiest use, the binary should be either in your PATH or your current directory.

Create a Caddyfile with the following content:

localhost:7443 {
	respond "Hello, world! You're using {http.request.proto}"
}

Then run Caddy:

./caddy start

Making requests to https://localhost:7443 should tell you which protocol is being used.

You can change the hard-coded response to something more useful by replacing respond with reverse_proxy or file_server, for example: reverse_proxy localhost:80