lib: pass in 'struct Curl_easy *' to most functions

... in most cases instead of 'struct connectdata *' but in some cases in
addition to.

- We mostly operate on transfers and not connections.

- We need the transfer handle to log, store data and more. Everything in
  libcurl is driven by a transfer (the CURL * in the public API).

- This work clarifies and separates the transfers from the connections
  better.

- We should avoid "conn->data". Since individual connections can be used
  by many transfers when multiplexing, making sure that conn->data
  points to the current and correct transfer at all times is difficult
  and has been notoriously error-prone over the years. The goal is to
  ultimately remove the conn->data pointer for this reason.

Closes #6425

1 files changed, 17 insertions, 7 deletions

diff --git a/lib/easy.c b/lib/easy.c
index 04e59144b..3b72ce7a4 100644
--- a/lib/easy.c
+++ b/lib/easy.c
@@ -1072,7 +1072,7 @@ CURLcode curl_easy_pause(struct Curl_easy *data, int action)
         /* even if one function returns error, this loops through and frees
            all buffers */
         if(!result)
-          result = Curl_client_write(conn, writebuf[i].type,
+          result = Curl_client_write(data, writebuf[i].type,
                                      Curl_dyn_ptr(&writebuf[i].b),
                                      Curl_dyn_len(&writebuf[i].b));
         Curl_dyn_free(&writebuf[i].b);
@@ -1156,8 +1156,13 @@ CURLcode curl_easy_recv(struct Curl_easy *data, void *buffer, size_t buflen,
   if(result)
     return result;
 
+  if(!data->conn)
+    /* on first invoke, the transfer has been detached from the connection and
+       needs to be reattached */
+    Curl_attach_connnection(data, c);
+
   *n = 0;
-  result = Curl_read(c, sfd, buffer, buflen, &n1);
+  result = Curl_read(data, sfd, buffer, buflen, &n1);
 
   if(result)
     return result;
@@ -1186,8 +1191,13 @@ CURLcode curl_easy_send(struct Curl_easy *data, const void *buffer,
   if(result)
     return result;
 
+  if(!data->conn)
+    /* on first invoke, the transfer has been detached from the connection and
+       needs to be reattached */
+    Curl_attach_connnection(data, c);
+
   *n = 0;
-  result = Curl_write(c, sfd, buffer, buflen, &n1);
+  result = Curl_write(data, sfd, buffer, buflen, &n1);
 
   if(n1 == -1)
     return CURLE_SEND_ERROR;
@@ -1206,16 +1216,16 @@ CURLcode curl_easy_send(struct Curl_easy *data, const void *buffer,
  *
  * Returns always 0.
  */
-static int conn_upkeep(struct connectdata *conn,
+static int conn_upkeep(struct Curl_easy *data,
+                       struct connectdata *conn,
                        void *param)
 {
   /* Param is unused. */
   (void)param;
 
-  if(conn->handler->connection_check) {
+  if(conn->handler->connection_check)
     /* Do a protocol-specific keepalive check on the connection. */
-    conn->handler->connection_check(conn, CONNCHECK_KEEPALIVE);
-  }
+    conn->handler->connection_check(data, conn, CONNCHECK_KEEPALIVE);
 
   return 0; /* continue iteration */
 }