HTTP3: initial (experimental) support

USe configure --with-ngtcp2 or --with-quiche

Using either option will enable a HTTP3 build.
Co-authored-by: Alessandro Ghedini <alessandro@ghedini.me>

Closes #3500

4 files changed, 67 insertions, 0 deletions

diff --git a/docs/libcurl/curl_easy_setopt.3 b/docs/libcurl/curl_easy_setopt.3
index 1f18a3494..cb5c418fb 100644
--- a/docs/libcurl/curl_easy_setopt.3
+++ b/docs/libcurl/curl_easy_setopt.3
@@ -321,6 +321,8 @@ Enable and configure Alt-Svc: treatment. See \fICURLOPT_ALTSVC_CTRL(3)\fP
 Do an HTTP GET request. See \fICURLOPT_HTTPGET(3)\fP
 .IP CURLOPT_REQUEST_TARGET
 Set the request target. \fICURLOPT_REQUEST_TARGET(3)\fP
+.IP CURLOPT_H3
+Specify HTTP/3 behavior. \fICURLOPT_H3(3)\fP
 .IP CURLOPT_HTTP_VERSION
 HTTP version to use. \fICURLOPT_HTTP_VERSION(3)\fP
 .IP CURLOPT_HTTP09_ALLOWED
diff --git a/docs/libcurl/opts/CURLOPT_H3.3 b/docs/libcurl/opts/CURLOPT_H3.3
new file mode 100644
index 000000000..be521b6bf
--- /dev/null
+++ b/docs/libcurl/opts/CURLOPT_H3.3
@@ -0,0 +1,61 @@
+.\" **************************************************************************
+.\" *                                  _   _ ____  _
+.\" *  Project                     ___| | | |  _ \| |
+.\" *                             / __| | | | |_) | |
+.\" *                            | (__| |_| |  _ <| |___
+.\" *                             \___|\___/|_| \_\_____|
+.\" *
+.\" * Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
+.\" *
+.\" * This software is licensed as described in the file COPYING, which
+.\" * you should have received as part of this distribution. The terms
+.\" * are also available at https://curl.haxx.se/docs/copyright.html.
+.\" *
+.\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+.\" * copies of the Software, and permit persons to whom the Software is
+.\" * furnished to do so, under the terms of the COPYING file.
+.\" *
+.\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+.\" * KIND, either express or implied.
+.\" *
+.\" **************************************************************************
+.\"
+.TH CURLOPT_H3 3 "27 Nov 2018" "libcurl 7.66.0" "curl_easy_setopt options"
+.SH NAME
+CURLOPT_H3 \- specify HTTP/3 protocol behavior
+.SH SYNOPSIS
+#include <curl/curl.h>
+
+CURLcode curl_easy_setopt(CURL *handle, CURLOPT_H3, long bitmask);
+.SH EXPERIMENTAL
+Warning: this feature is early code and is marked as experimental. It can only
+be enabled by explicitly invoking configure with \fB--with-quiche\fP or
+\fB--with-ngtcp2\fP. You are advised to not ship this feature used in
+production before the experimental label is removed.
+.SH DESCRIPTION
+This function accepts a long \fIbitmask\fP with a set of flags set that
+controls the HTTP/3 behavior for this transfer.
+.IP "CURLH3_DIRECT"
+If this bit is set in \fIbitmask\fP, the host name and port number given in
+the URL will be used to connect to directly with QUIC and the port number then
+being a UDP port number.
+.SH DEFAULT
+0
+.SH PROTOCOLS
+HTTPS
+.SH EXAMPLE
+.nf
+CURL *curl = curl_easy_init();
+if(curl) {
+  CURLcode ret;
+  curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
+  curl_easy_setopt(curl, CURLOPT_H3, (long)CURLH3_DIRECT);
+  ret = curl_easy_perform(curl);
+}
+.fi
+.SH AVAILABILITY
+Added in 7.66.0
+.SH RETURN VALUE
+Returns CURLE_OK if supported, an error otherwise.
+.SH "SEE ALSO"
+.BR CURLOPT_HTTP_VERSION "(3), "
diff --git a/docs/libcurl/opts/Makefile.inc b/docs/libcurl/opts/Makefile.inc
index c8e15a5ed..5460b2a57 100644
--- a/docs/libcurl/opts/Makefile.inc
+++ b/docs/libcurl/opts/Makefile.inc
@@ -150,6 +150,7 @@ man_MANS =                                      \
   CURLOPT_FTP_USE_EPSV.3                        \
   CURLOPT_FTP_USE_PRET.3                        \
   CURLOPT_GSSAPI_DELEGATION.3                   \
+  CURLOPT_H3.3                                  \
   CURLOPT_HAPPY_EYEBALLS_TIMEOUT_MS.3           \
   CURLOPT_HAPROXYPROTOCOL.3                     \
   CURLOPT_HEADER.3                              \
diff --git a/docs/libcurl/symbols-in-versions b/docs/libcurl/symbols-in-versions
index 16fb5622c..1b452d245 100644
--- a/docs/libcurl/symbols-in-versions
+++ b/docs/libcurl/symbols-in-versions
@@ -209,6 +209,7 @@ CURLFTP_CREATE_DIR_RETRY        7.19.4
 CURLGSSAPI_DELEGATION_FLAG      7.22.0
 CURLGSSAPI_DELEGATION_NONE      7.22.0
 CURLGSSAPI_DELEGATION_POLICY_FLAG 7.22.0
+CURLH3_DIRECT                   7.66.0
 CURLHEADER_SEPARATE             7.37.0
 CURLHEADER_UNIFIED              7.37.0
 CURLINFO_ACTIVESOCKET           7.45.0
@@ -424,6 +425,7 @@ CURLOPT_FTP_USE_EPRT            7.10.5
 CURLOPT_FTP_USE_EPSV            7.9.2
 CURLOPT_FTP_USE_PRET            7.20.0
 CURLOPT_GSSAPI_DELEGATION       7.22.0
+CURLOPT_H3                      7.66.0
 CURLOPT_HAPPY_EYEBALLS_TIMEOUT_MS 7.59.0
 CURLOPT_HAPROXYPROTOCOL         7.60.0
 CURLOPT_HEADER                  7.1
@@ -925,6 +927,7 @@ CURL_VERSION_DEBUG              7.10.6
 CURL_VERSION_GSSAPI             7.38.0
 CURL_VERSION_GSSNEGOTIATE       7.10.6        7.38.0
 CURL_VERSION_HTTP2              7.33.0
+CURL_VERSION_HTTP3              7.66.0
 CURL_VERSION_HTTPS_PROXY        7.52.0
 CURL_VERSION_IDN                7.12.0
 CURL_VERSION_IPV6               7.10