Do media checks on getting next block encryption status (#74)

* Do media check before getting NBES and allow getting status without media
* Supress error from BLANK CHECK sense when querying next block encryption status

src/main.cpp

@@ -200,7 +200,7 @@ static void print_device_status(std::ostream& os, const scsi::page_des& opt, boo
 }
 
 static void showDriveStatus(const std::string& tapeDrive, bool detail) {
-  alignas(4) scsi::page_buffer buffer;
+  alignas(4) scsi::page_buffer buffer {};
   scsi::get_des(tapeDrive, buffer, sizeof(buffer));
   auto& opt {reinterpret_cast<const scsi::page_des&>(buffer)};
 
@@ -281,7 +281,7 @@ static void print_volume_status(std::ostream& os, const scsi::page_nbes& opt)
 }
 
 static void showVolumeStatus(const std::string& tapeDrive) {
-  alignas(4) scsi::page_buffer buffer;
+  alignas(4) scsi::page_buffer buffer {};
   scsi::get_nbes(tapeDrive, buffer, sizeof(buffer));
   auto& opt {reinterpret_cast<const scsi::page_nbes&>(buffer)};
 
@@ -420,8 +420,19 @@ int main(int argc, const char **argv) {
         inquiryDrive(tapeDrive);
       }
       showDriveStatus(tapeDrive, detail);
-      if (detail) {
-        showVolumeStatus(tapeDrive);
+      if (detail && scsi::is_device_ready(tapeDrive)) {
+        try {
+          showVolumeStatus(tapeDrive);
+        } catch (const scsi::scsi_error& err) {
+          // #71: ignore BLANK CHECK sense key that some drives may return
+          // during media access check in getting NBES
+          auto sense_key {
+            err.get_sense().flags & scsi::sense_data::flags_sense_key_mask
+          };
+          if (sense_key != scsi::sense_data::blank_check) {
+            throw;
+          }
+        }
       }
       exit(EXIT_SUCCESS);
     } catch (const scsi::scsi_error& err) {
@@ -495,7 +506,7 @@ int main(int argc, const char **argv) {
                                     key, key_name, rdmc, ckod)};
     scsi::write_sde(tapeDrive, sde_buffer.get());
 
-    alignas(4) scsi::page_buffer buffer;
+    alignas(4) scsi::page_buffer buffer {};
     scsi::get_des(tapeDrive, buffer, sizeof(buffer));
     auto& opt {reinterpret_cast<const scsi::page_des&>(buffer)};
 

src/scsiencrypt.cpp

@@ -83,7 +83,7 @@ static void scsi_execute(const std::string& device, const std::uint8_t *cmd_p,
                          std::size_t dxfer_len, scsi_direction direction)
 {
 #if defined(OS_LINUX)
-  unique_fd fd {open(device.c_str(), O_RDONLY)};
+  unique_fd fd {open(device.c_str(), O_RDONLY | O_NDELAY)};
   if (!fd) {
     std::ostringstream oss;
     oss << "Cannot open device " << device;
@@ -146,6 +146,19 @@ static void scsi_execute(const std::string& device, const std::uint8_t *cmd_p,
 
 namespace scsi {
 
+bool is_device_ready(const std::string& device)
+{
+  const std::uint8_t test_unit_ready_cmd[6] {};
+
+  try {
+    scsi_execute(device, test_unit_ready_cmd, sizeof(test_unit_ready_cmd),
+                 nullptr, 0u, scsi_direction::from_device);
+    return true;
+  } catch (const scsi::scsi_error& err) {
+    return false;
+  }
+}
+
 void get_des(const std::string& device, std::uint8_t *buffer, std::size_t length)
 {
   const std::uint8_t spin_des_command[] {
@@ -266,31 +279,31 @@ void write_sde(const std::string& device, const std::uint8_t *sde_buffer)
 void print_sense_data(std::ostream& os, const sense_data& sd) {
   os << std::left << std::setw(25) << "Sense Code: ";
 
-  auto sense_key {static_cast<unsigned int>(sd.flags & sense_data::flags_sense_key_mask)};
+  auto sense_key {sd.flags & sense_data::flags_sense_key_mask};
 
   switch (sense_key) {
-  case 0u:
+  case sense_data::no_sense:
     os << "No specific error";
     break;
-  case 2u:
+  case sense_data::not_ready:
     os << "Device not ready";
     break;
-  case 3u:
+  case sense_data::medium_error:
     os << "Medium Error";
     break;
-  case 4u:
+  case sense_data::hardware_error:
     os << "Hardware Error";
     break;
-  case 5u:
+  case sense_data::illegal_request:
     os << "Illegal Request";
     break;
-  case 6u:
+  case sense_data::unit_attention:
     os << "Unit Attention";
     break;
-  case 7u:
+  case sense_data::data_protect:
     os << "Data protect";
     break;
-  case 8u:
+  case sense_data::blank_check:
     os << "Blank tape";
     break;
   }

src/scsiencrypt.h

@@ -285,6 +285,17 @@ struct __attribute__((packed)) sense_data {
   std::uint8_t field_replaceable_unit_code;
   std::uint8_t sense_key_specific[3];
   std::uint8_t additional_sense_bytes[];
+
+  static constexpr std::byte no_sense {0u};
+  static constexpr std::byte recovered_error {1u};
+  static constexpr std::byte not_ready {2u};
+  static constexpr std::byte medium_error {3u};
+  static constexpr std::byte hardware_error {4u};
+  static constexpr std::byte illegal_request {5u};
+  static constexpr std::byte unit_attention {6u};
+  static constexpr std::byte data_protect {7u};
+  static constexpr std::byte blank_check {8u};
+
   static constexpr auto maximum_size {252u}; // per SPC-5
 };
 static_assert(sizeof(sense_data) == 18u);
@@ -321,6 +332,9 @@ std::vector<const kad *> read_page_kads(const Page& page)
   return v;
 }
 
+// Check if a tape is loaded
+bool is_device_ready(const std::string& device);
+// Get SCSI inquiry data from device
 inquiry_data get_inquiry(const std::string& device);
 // Get data encryption status page
 void get_des(const std::string& device, std::uint8_t *buffer, std::size_t length);