I'm not sure how this fares on the clever/too clever scale, but this whole function could be written as a single statement:

    return dlna_src->server_info != NULL
        && dlna_src->server_info->content_features != NULL
        && dlna_src->server_info->time_seek_response_receive
        && dlna_src->server_info->content_features->op_time_seek_supported;