http: add support to read and store the referrer header

- add CURLINFO_REFERER libcurl option
- add --write-out '%{referer}' command-line option
- extend --xattr command-line option to fill user.xdg.referrer.url extended
  attribute with the referrer (if there was any)

Closes #6591

6 files changed, 13 insertions, 3 deletions

diff --git a/docs/cmdline-opts/write-out.d b/docs/cmdline-opts/write-out.d
index be8f75ad5..0579cae69 100644
--- a/docs/cmdline-opts/write-out.d
+++ b/docs/cmdline-opts/write-out.d
@@ -93,6 +93,9 @@ When an HTTP request was made without --location to follow redirects (or when
 --max-redir is met), this variable will show the actual URL a redirect
 \fIwould\fP have gone to. (Added in 7.18.2)
 .TP
+.B referer
+The Referer: header, if there was any. (Added in 7.76.0)
+.TP
 .B remote_ip
 The remote IP address of the most recently done connection - can be either
 IPv4 or IPv6 (Added in 7.29.0)
diff --git a/docs/examples/Makefile.inc b/docs/examples/Makefile.inc
index defaad6d6..84a2bdac6 100644
--- a/docs/examples/Makefile.inc
+++ b/docs/examples/Makefile.inc
@@ -43,6 +43,7 @@ check_PROGRAMS = \
   getinfo \
   getinmemory \
   getredirect \
+  getreferrer \
   http-post \
   http2-download \
   http2-pushinmemory \
diff --git a/docs/libcurl/curl_easy_getinfo.3 b/docs/libcurl/curl_easy_getinfo.3
index d3dfcf26b..845e303e3 100644
--- a/docs/libcurl/curl_easy_getinfo.3
+++ b/docs/libcurl/curl_easy_getinfo.3
@@ -5,7 +5,7 @@
 .\" *                            | (__| |_| |  _ <| |___
 .\" *                             \___|\___/|_| \_\_____|
 .\" *
-.\" * Copyright (C) 1998 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
+.\" * Copyright (C) 1998 - 2021, 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
@@ -50,6 +50,9 @@ See \fICURLINFO_EFFECTIVE_URL(3)\fP
 .IP CURLINFO_RESPONSE_CODE
 Last received response code.
 See \fICURLINFO_RESPONSE_CODE(3)\fP
+.IP CURLINFO_REFERER
+Referrer header.
+See \fICURLINFO_REFERER(3)\fP
 .IP CURLINFO_HTTP_CONNECTCODE
 Last proxy CONNECT response code.
 See \fICURLINFO_HTTP_CONNECTCODE(3)\fP
diff --git a/docs/libcurl/opts/CURLOPT_REFERER.3 b/docs/libcurl/opts/CURLOPT_REFERER.3
index c3a0ed781..ce3ed173c 100644
--- a/docs/libcurl/opts/CURLOPT_REFERER.3
+++ b/docs/libcurl/opts/CURLOPT_REFERER.3
@@ -5,7 +5,7 @@
 .\" *                            | (__| |_| |  _ <| |___
 .\" *                             \___|\___/|_| \_\_____|
 .\" *
-.\" * Copyright (C) 1998 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
+.\" * Copyright (C) 1998 - 2021, 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
@@ -58,3 +58,4 @@ Returns CURLE_OK if HTTP support is enabled, CURLE_UNKNOWN_OPTION if not, or
 CURLE_OUT_OF_MEMORY if there was insufficient heap space.
 .SH "SEE ALSO"
 .BR CURLOPT_USERAGENT "(3), " CURLOPT_HTTPHEADER "(3), "
+.BR CURLINFO_REFERER "(3), "
diff --git a/docs/libcurl/opts/Makefile.inc b/docs/libcurl/opts/Makefile.inc
index 5cec7cb4e..69e241862 100644
--- a/docs/libcurl/opts/Makefile.inc
+++ b/docs/libcurl/opts/Makefile.inc
@@ -5,7 +5,7 @@
 #                            | (__| |_| |  _ <| |___
 #                             \___|\___/|_| \_\_____|
 #
-# Copyright (C) 1998 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
+# Copyright (C) 1998 - 2021, 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
@@ -64,6 +64,7 @@ man_MANS =                                      \
   CURLINFO_REDIRECT_TIME.3                      \
   CURLINFO_REDIRECT_TIME_T.3                    \
   CURLINFO_REDIRECT_URL.3                       \
+  CURLINFO_REFERER.3                            \
   CURLINFO_REQUEST_SIZE.3                       \
   CURLINFO_RESPONSE_CODE.3                      \
   CURLINFO_RETRY_AFTER.3                        \
diff --git a/docs/libcurl/symbols-in-versions b/docs/libcurl/symbols-in-versions
index 7da5c4cfa..5ff3a3503 100644
--- a/docs/libcurl/symbols-in-versions
+++ b/docs/libcurl/symbols-in-versions
@@ -271,6 +271,7 @@ CURLINFO_REDIRECT_COUNT         7.9.7
 CURLINFO_REDIRECT_TIME          7.9.7
 CURLINFO_REDIRECT_TIME_T        7.61.0
 CURLINFO_REDIRECT_URL           7.18.2
+CURLINFO_REFERER                7.76.0
 CURLINFO_REQUEST_SIZE           7.4.1
 CURLINFO_RESPONSE_CODE          7.10.8
 CURLINFO_RETRY_AFTER            7.66.0