root/printing/backend/print_backend_cups.cc

DEFINITIONS

1. Init
2. blocking_
3. EnumeratePrinters
4. GetDefaultPrinterName
5. GetPrinterSemanticCapsAndDefaults
6. GetPrinterCapsAndDefaults
7. GetPrinterDriverInfo
8. IsValidPrinter
9. CreateInstance
10. GetDests
11. GetPPD

// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "printing/backend/print_backend.h"

#include "build/build_config.h"

#include <dlfcn.h>
#include <errno.h>
#include <pthread.h>

#if !defined(OS_MACOSX)
#include <gcrypt.h>
#endif

#include "base/debug/leak_annotations.h"
#include "base/file_util.h"
#include "base/lazy_instance.h"
#include "base/logging.h"
#include "base/strings/string_number_conversions.h"
#include "base/synchronization/lock.h"
#include "base/values.h"
#include "printing/backend/cups_helper.h"
#include "printing/backend/print_backend_consts.h"
#include "url/gurl.h"

#if !defined(OS_MACOSX)
GCRY_THREAD_OPTION_PTHREAD_IMPL;

namespace {

// Init GCrypt library (needed for CUPS) using pthreads.
// There exists a bug in CUPS library, where it crashed with: "ath.c:184:
// _gcry_ath_mutex_lock: Assertion `*lock == ((ath_mutex_t) 0)' failed."
// It happened when multiple threads tried printing simultaneously.
// Google search for 'gnutls thread safety' provided a solution that
// initialized gcrypt and gnutls.

// TODO(phajdan.jr): Remove this after https://bugs.g10code.com/gnupg/issue1197
// gets fixed on all Linux distros we support (i.e. when they ship libgcrypt
// with the fix).

// Initially, we linked with -lgnutls and simply called gnutls_global_init(),
// but this did not work well since we build one binary on Ubuntu Hardy and
// expect it to run on many Linux distros. (See http://crbug.com/46954)
// So instead we use dlopen() and dlsym() to dynamically load and call
// gnutls_global_init().

class GcryptInitializer {
 public:
  GcryptInitializer() {
    Init();
  }

 private:
  void Init() {
    const char* kGnuTlsFiles[] = {
      "libgnutls.so.28",
      "libgnutls.so.26",
      "libgnutls.so",
    };
    gcry_control(GCRYCTL_SET_THREAD_CBS, &gcry_threads_pthread);
    for (size_t i = 0; i < arraysize(kGnuTlsFiles); ++i) {
      void* gnutls_lib = dlopen(kGnuTlsFiles[i], RTLD_NOW);
      if (!gnutls_lib) {
        VLOG(1) << "Cannot load " << kGnuTlsFiles[i];
        continue;
      }
      const char* kGnuTlsInitFuncName = "gnutls_global_init";
      int (*pgnutls_global_init)(void) = reinterpret_cast<int(*)()>(
          dlsym(gnutls_lib, kGnuTlsInitFuncName));
      if (!pgnutls_global_init) {
        VLOG(1) << "Could not find " << kGnuTlsInitFuncName
                << " in " << kGnuTlsFiles[i];
        continue;
      }
      {
        // GnuTLS has a genuine small memory leak that is easier to annotate
        // than suppress. See http://crbug.com/176888#c7
        // TODO(earthdok): remove this once the leak is fixed.
        ANNOTATE_SCOPED_MEMORY_LEAK;
        if ((*pgnutls_global_init)() != 0)
          LOG(ERROR) << "gnutls_global_init() failed";
      }
      return;
    }
    LOG(ERROR) << "Cannot find libgnutls";
  }
};

base::LazyInstance<GcryptInitializer> g_gcrypt_initializer =
    LAZY_INSTANCE_INITIALIZER;

}  // namespace
#endif  // !defined(OS_MACOSX)

namespace printing {

static const char kCUPSPrinterInfoOpt[] = "printer-info";
static const char kCUPSPrinterStateOpt[] = "printer-state";
static const char kCUPSPrinterTypeOpt[] = "printer-type";
static const char kCUPSPrinterMakeModelOpt[] = "printer-make-and-model";

class PrintBackendCUPS : public PrintBackend {
 public:
  PrintBackendCUPS(const GURL& print_server_url,
                   http_encryption_t encryption, bool blocking);

  // PrintBackend implementation.
  virtual bool EnumeratePrinters(PrinterList* printer_list) OVERRIDE;
  virtual std::string GetDefaultPrinterName() OVERRIDE;
  virtual bool GetPrinterSemanticCapsAndDefaults(
      const std::string& printer_name,
      PrinterSemanticCapsAndDefaults* printer_info) OVERRIDE;
  virtual bool GetPrinterCapsAndDefaults(
      const std::string& printer_name,
      PrinterCapsAndDefaults* printer_info) OVERRIDE;
  virtual std::string GetPrinterDriverInfo(
      const std::string& printer_name) OVERRIDE;
  virtual bool IsValidPrinter(const std::string& printer_name) OVERRIDE;

 protected:
  virtual ~PrintBackendCUPS() {}

 private:
  // Following functions are wrappers around corresponding CUPS functions.
  // <functions>2()  are called when print server is specified, and plain
  // version in another case. There is an issue specifing CUPS_HTTP_DEFAULT
  // in the <functions>2(), it does not work in CUPS prior to 1.4.
  int GetDests(cups_dest_t** dests);
  base::FilePath GetPPD(const char* name);

  GURL print_server_url_;
  http_encryption_t cups_encryption_;
  bool blocking_;
};

PrintBackendCUPS::PrintBackendCUPS(const GURL& print_server_url,
                                   http_encryption_t encryption,
                                   bool blocking)
    : print_server_url_(print_server_url),
      cups_encryption_(encryption),
      blocking_(blocking) {
}

bool PrintBackendCUPS::EnumeratePrinters(PrinterList* printer_list) {
  DCHECK(printer_list);
  printer_list->clear();

  cups_dest_t* destinations = NULL;
  int num_dests = GetDests(&destinations);
  if ((num_dests == 0) && (cupsLastError() > IPP_OK_EVENTS_COMPLETE)) {
    VLOG(1) << "CUPS: Error getting printers from CUPS server"
            << ", server: " << print_server_url_
            << ", error: " << static_cast<int>(cupsLastError());
    return false;
  }

  for (int printer_index = 0; printer_index < num_dests; ++printer_index) {
    const cups_dest_t& printer = destinations[printer_index];

    // CUPS can have 'printers' that are actually scanners. (not MFC)
    // At least on Mac. Check for scanners and skip them.
    const char* type_str = cupsGetOption(kCUPSPrinterTypeOpt,
        printer.num_options, printer.options);
    if (type_str != NULL) {
      int type;
      if (base::StringToInt(type_str, &type) && (type & CUPS_PRINTER_SCANNER))
        continue;
    }

    PrinterBasicInfo printer_info;
    printer_info.printer_name = printer.name;
    printer_info.is_default = printer.is_default;

    const char* info = cupsGetOption(kCUPSPrinterInfoOpt,
        printer.num_options, printer.options);
    if (info != NULL)
      printer_info.printer_description = info;

    const char* state = cupsGetOption(kCUPSPrinterStateOpt,
        printer.num_options, printer.options);
    if (state != NULL)
      base::StringToInt(state, &printer_info.printer_status);

    const char* drv_info = cupsGetOption(kCUPSPrinterMakeModelOpt,
                                         printer.num_options,
                                         printer.options);
    if (drv_info)
      printer_info.options[kDriverInfoTagName] = *drv_info;

    // Store printer options.
    for (int opt_index = 0; opt_index < printer.num_options; ++opt_index) {
      printer_info.options[printer.options[opt_index].name] =
          printer.options[opt_index].value;
    }

    printer_list->push_back(printer_info);
  }

  cupsFreeDests(num_dests, destinations);

  VLOG(1) << "CUPS: Enumerated printers"
          << ", server: " << print_server_url_
          << ", # of printers: " << printer_list->size();
  return true;
}

std::string PrintBackendCUPS::GetDefaultPrinterName() {
  // Not using cupsGetDefault() because it lies about the default printer.
  cups_dest_t* dests;
  int num_dests = GetDests(&dests);
  cups_dest_t* dest = cupsGetDest(NULL, NULL, num_dests, dests);
  std::string name = dest ? std::string(dest->name) : std::string();
  cupsFreeDests(num_dests, dests);
  return name;
}

bool PrintBackendCUPS::GetPrinterSemanticCapsAndDefaults(
    const std::string& printer_name,
    PrinterSemanticCapsAndDefaults* printer_info) {
  PrinterCapsAndDefaults info;
  if (!GetPrinterCapsAndDefaults(printer_name, &info) )
    return false;

  return ParsePpdCapabilities(
      printer_name, info.printer_capabilities, printer_info);
}

bool PrintBackendCUPS::GetPrinterCapsAndDefaults(
    const std::string& printer_name,
    PrinterCapsAndDefaults* printer_info) {
  DCHECK(printer_info);

  VLOG(1) << "CUPS: Getting caps and defaults"
          << ", printer name: " << printer_name;

  base::FilePath ppd_path(GetPPD(printer_name.c_str()));
  // In some cases CUPS failed to get ppd file.
  if (ppd_path.empty()) {
    LOG(ERROR) << "CUPS: Failed to get PPD"
               << ", printer name: " << printer_name;
    return false;
  }

  std::string content;
  bool res = base::ReadFileToString(ppd_path, &content);

  base::DeleteFile(ppd_path, false);

  if (res) {
    printer_info->printer_capabilities.swap(content);
    printer_info->caps_mime_type = "application/pagemaker";
    // In CUPS, printer defaults is a part of PPD file. Nothing to upload here.
    printer_info->printer_defaults.clear();
    printer_info->defaults_mime_type.clear();
  }

  return res;
}

std::string PrintBackendCUPS::GetPrinterDriverInfo(
    const std::string& printer_name) {
  cups_dest_t* destinations = NULL;
  int num_dests = GetDests(&destinations);
  std::string result;
  for (int printer_index = 0; printer_index < num_dests; ++printer_index) {
    const cups_dest_t& printer = destinations[printer_index];
    if (printer_name == printer.name) {
      const char* info = cupsGetOption(kCUPSPrinterMakeModelOpt,
                                       printer.num_options,
                                       printer.options);
      if (info)
        result = *info;
    }
  }

  cupsFreeDests(num_dests, destinations);
  return result;
}

bool PrintBackendCUPS::IsValidPrinter(const std::string& printer_name) {
  // This is not very efficient way to get specific printer info. CUPS 1.4
  // supports cupsGetNamedDest() function. However, CUPS 1.4 is not available
  // everywhere (for example, it supported from Mac OS 10.6 only).
  PrinterList printer_list;
  EnumeratePrinters(&printer_list);

  PrinterList::iterator it;
  for (it = printer_list.begin(); it != printer_list.end(); ++it)
    if (it->printer_name == printer_name)
      return true;
  return false;
}

scoped_refptr<PrintBackend> PrintBackend::CreateInstance(
    const base::DictionaryValue* print_backend_settings) {
#if !defined(OS_MACOSX)
  // Initialize gcrypt library.
  g_gcrypt_initializer.Get();
#endif

  std::string print_server_url_str, cups_blocking;
  int encryption = HTTP_ENCRYPT_NEVER;
  if (print_backend_settings) {
    print_backend_settings->GetString(kCUPSPrintServerURL,
                                      &print_server_url_str);

    print_backend_settings->GetString(kCUPSBlocking,
                                      &cups_blocking);

    print_backend_settings->GetInteger(kCUPSEncryption, &encryption);
  }
  GURL print_server_url(print_server_url_str.c_str());
  return new PrintBackendCUPS(print_server_url,
                              static_cast<http_encryption_t>(encryption),
                              cups_blocking == kValueTrue);
}

int PrintBackendCUPS::GetDests(cups_dest_t** dests) {
  if (print_server_url_.is_empty()) {  // Use default (local) print server.
    return cupsGetDests(dests);
  } else {
    HttpConnectionCUPS http(print_server_url_, cups_encryption_);
    http.SetBlocking(blocking_);
    return cupsGetDests2(http.http(), dests);
  }
}

base::FilePath PrintBackendCUPS::GetPPD(const char* name) {
  // cupsGetPPD returns a filename stored in a static buffer in CUPS.
  // Protect this code with lock.
  CR_DEFINE_STATIC_LOCAL(base::Lock, ppd_lock, ());
  base::AutoLock ppd_autolock(ppd_lock);
  base::FilePath ppd_path;
  const char* ppd_file_path = NULL;
  if (print_server_url_.is_empty()) {  // Use default (local) print server.
    ppd_file_path = cupsGetPPD(name);
    if (ppd_file_path)
      ppd_path = base::FilePath(ppd_file_path);
  } else {
    // cupsGetPPD2 gets stuck sometimes in an infinite time due to network
    // configuration/issues. To prevent that, use non-blocking http connection
    // here.
    // Note: After looking at CUPS sources, it looks like non-blocking
    // connection will timeout after 10 seconds of no data period. And it will
    // return the same way as if data was completely and sucessfully downloaded.
    HttpConnectionCUPS http(print_server_url_, cups_encryption_);
    http.SetBlocking(blocking_);
    ppd_file_path = cupsGetPPD2(http.http(), name);
    // Check if the get full PPD, since non-blocking call may simply return
    // normally after timeout expired.
    if (ppd_file_path) {
      // There is no reliable way right now to detect full and complete PPD
      // get downloaded. If we reach http timeout, it may simply return
      // downloaded part as a full response. It might be good enough to check
      // http->data_remaining or http->_data_remaining, unfortunately http_t
      // is an internal structure and fields are not exposed in CUPS headers.
      // httpGetLength or httpGetLength2 returning the full content size.
      // Comparing file size against that content length might be unreliable
      // since some http reponses are encoded and content_length > file size.
      // Let's just check for the obvious CUPS and http errors here.
      ppd_path = base::FilePath(ppd_file_path);
      ipp_status_t error_code = cupsLastError();
      int http_error = httpError(http.http());
      if (error_code > IPP_OK_EVENTS_COMPLETE || http_error != 0) {
        LOG(ERROR) << "Error downloading PPD file"
                   << ", name: " << name
                   << ", CUPS error: " << static_cast<int>(error_code)
                   << ", HTTP error: " << http_error;
        base::DeleteFile(ppd_path, false);
        ppd_path.clear();
      }
    }
  }
  return ppd_path;
}

}  // namespace printing