curl: Keep pointer to the CURLState in CURLSocket

A follow-up patch will make curl_multi_do() and curl_multi_read() take a
CURLSocket instead of the CURLState.  They still need the latter,
though, so add a pointer to it to the former.

Cc: qemu-stable@nongnu.org
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Message-id: 20190910124136.10565-2-mreitz@redhat.com
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>

block/curl.c

@@ -80,6 +80,7 @@ static CURLMcode __curl_multi_socket_action(CURLM *multi_handle,
 #define CURL_BLOCK_OPT_TIMEOUT_DEFAULT 5
 
 struct BDRVCURLState;
+struct CURLState;
 
 static bool libcurl_initialized;
 
@@ -97,6 +98,7 @@ typedef struct CURLAIOCB {
 
 typedef struct CURLSocket {
     int fd;
+    struct CURLState *state;
     QLIST_ENTRY(CURLSocket) next;
 } CURLSocket;
 
@@ -180,6 +182,7 @@ static int curl_sock_cb(CURL *curl, curl_socket_t fd, int action,
     if (!socket) {
         socket = g_new0(CURLSocket, 1);
         socket->fd = fd;
+        socket->state = state;
         QLIST_INSERT_HEAD(&state->sockets, socket, next);
     }
     socket = NULL;