OpenSSL: Use SSL_pending() to determine if we want a select() before SSL_read()

In order to obey the timeout in idevice_connection_receive_timeout(), we are
using select() via socket_check_fd(). However, the SSL bio might have buffered
more bytes than actually requested upon a call to SSL_read(), so in the next
call to idevice_connection_receive_timeout() a select() would not find the fd
being ready to read, and make it fail with an error, after the specified
timeout is reached.
With the help of SSL_pending() we can now skip calling select() so that
SSL_read() will directly be called again.

1 files changed, 16 insertions, 11 deletions

diff --git a/src/idevice.c b/src/idevice.c
index 02d34cc..794af8b 100644
--- a/src/idevice.c
+++ b/src/idevice.c
@@ -453,19 +453,24 @@ LIBIMOBILEDEVICE_API idevice_error_t idevice_connection_receive_timeout(idevice_
 
         if (connection->ssl_data) {
                 uint32_t received = 0;
+                int do_select = 1;
 
                 while (received < len) {
-
-                        int conn_error = socket_check_fd((int)(long)connection->data, FDM_READ, timeout);
-                        idevice_error_t error = socket_recv_to_idevice_error(conn_error, len, received);
-
-                        switch (error) {
-                                case IDEVICE_E_SUCCESS:
-                                        break;
-                                case IDEVICE_E_UNKNOWN_ERROR:
-                                        debug_info("ERROR: socket_check_fd returned %d (%s)", conn_error, strerror(-conn_error));
-                                default:
-                                        return error;
+#ifdef HAVE_OPENSSL
+                        do_select = (SSL_pending(connection->ssl_data->session) == 0);
+#endif
+                        if (do_select) {
+                                int conn_error = socket_check_fd((int)(long)connection->data, FDM_READ, timeout);
+                                idevice_error_t error = socket_recv_to_idevice_error(conn_error, len, received);
+
+                                switch (error) {
+                                        case IDEVICE_E_SUCCESS:
+                                                break;
+                                        case IDEVICE_E_UNKNOWN_ERROR:
+                                                debug_info("ERROR: socket_check_fd returned %d (%s)", conn_error, strerror(-conn_error));
+                                        default:
+                                                return error;
+                                }
                         }
 
 #ifdef HAVE_OPENSSL