url: add option CURLOPT_SUPPRESS_CONNECT_HEADERS

- Add new option CURLOPT_SUPPRESS_CONNECT_HEADERS to allow suppressing
  proxy CONNECT response headers from the user callback functions
  CURLOPT_HEADERFUNCTION and CURLOPT_WRITEFUNCTION.

- Add new tool option --suppress-connect-headers to expose
  CURLOPT_SUPPRESS_CONNECT_HEADERS and allow suppressing proxy CONNECT
  response headers from --dump-header and --include.

Assisted-by: Jay Satiro
Assisted-by: CarloCannas@users.noreply.github.com
Closes https://github.com/curl/curl/pull/783

3 files changed, 14 insertions, 10 deletions

diff --git a/lib/http_proxy.c b/lib/http_proxy.c
index a67328647..f09304a26 100644
--- a/lib/http_proxy.c
+++ b/lib/http_proxy.c
@@ -316,8 +316,6 @@ CURLcode Curl_proxyCONNECT(struct connectdata *conn,
       perline = 0;
 
       while(nread < BUFSIZE && keepon && !error) {
-        int writetype;
-
         if(Curl_pgrsUpdate(conn))
           return CURLE_ABORTED_BY_CALLBACK;
 
@@ -419,19 +417,20 @@ CURLcode Curl_proxyCONNECT(struct connectdata *conn,
           Curl_debug(data, CURLINFO_HEADER_IN,
                      line_start, (size_t)perline, conn);
 
-        /* send the header to the callback */
-        writetype = CLIENTWRITE_HEADER;
-        if(data->set.include_header)
-          writetype |= CLIENTWRITE_BODY;
+        if(!data->set.suppress_connect_headers) {
+          /* send the header to the callback */
+          int writetype = CLIENTWRITE_HEADER;
+          if(data->set.include_header)
+            writetype |= CLIENTWRITE_BODY;
 
-        result = Curl_client_write(conn, writetype, line_start, perline);
+          result = Curl_client_write(conn, writetype, line_start, perline);
+          if(result)
+            return result;
+        }
 
         data->info.header_size += (long)perline;
         data->req.headerbytecount += (long)perline;
 
-        if(result)
-          return result;
-
         /* Newlines are CRLF, so the CR is ignored as the line isn't
            really terminated until the LF comes. Treat a following CR
            as end-of-headers as well.*/
diff --git a/lib/url.c b/lib/url.c
index f9c324269..c306b5776 100644
--- a/lib/url.c
+++ b/lib/url.c
@@ -2894,6 +2894,9 @@ CURLcode Curl_setopt(struct Curl_easy *data, CURLoption option,
   case CURLOPT_CONNECT_TO:
     data->set.connect_to = va_arg(param, struct curl_slist *);
     break;
+  case CURLOPT_SUPPRESS_CONNECT_HEADERS:
+    data->set.suppress_connect_headers = (0 != va_arg(param, long))?TRUE:FALSE;
+    break;
   default:
     /* unknown tag and its companion, just ignore: */
     result = CURLE_UNKNOWN_OPTION;
diff --git a/lib/urldata.h b/lib/urldata.h
index 7402332d1..2dd7938e0 100644
--- a/lib/urldata.h
+++ b/lib/urldata.h
@@ -1756,6 +1756,8 @@ struct UserDefined {
   bool pipewait;        /* wait for pipe/multiplex status before starting a
                            new connection */
   long expect_100_timeout; /* in milliseconds */
+  bool suppress_connect_headers;  /* suppress proxy CONNECT response headers
+                                     from user callbacks */
 
   struct Curl_easy *stream_depends_on;
   bool stream_depends_e; /* set or don't set the Exclusive bit */