libbrillo: Add SafeFD::Error::kDoesNotExist.

BUG=chromium:977388
TEST=FEATURES=test emerge-${BOARD} libbrillo

Change-Id: Idbff7a7c1bf8f30134b00c0bb6bc762de72635d6
Reviewed-on: https://chromium-review.googlesource.com/1726746
Tested-by: Allen Webb <allenwebb@google.com>
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Jorge Lucangeli Obes <jorgelo@chromium.org>
Reviewed-by: Mattias Nissler <mnissler@chromium.org>
Cr-Mirrored-From: https://chromium.googlesource.com/chromiumos/platform2
Cr-Mirrored-Commit: f4214a5032b781973bae3ed8519bb93dd6106dfc

3 files changed, 26 insertions, 2 deletions

diff --git a/brillo/files/safe_fd.cc b/brillo/files/safe_fd.cc
index 1b4596f..3823387 100644
--- a/brillo/files/safe_fd.cc
+++ b/brillo/files/safe_fd.cc
@@ -48,6 +48,10 @@ SafeFD::SafeFDResult OpenPathComponentInternal(int parent_fd,
     // symlink. It fails with ENXIO when |path| is a FIFO and |flags| is for
     // writing because of the O_NONBLOCK flag added above.
     switch (errno) {
+      case ENOENT:
+        // Do not write to the log because opening a non-existent file is a
+        // frequent occurrence.
+        return MakeErrorResult(SafeFD::Error::kDoesNotExist);
       case ELOOP:
         // PLOG prints something along the lines of the symlink depth being too
         // great which is is misleading so LOG is used instead.
diff --git a/brillo/files/safe_fd.h b/brillo/files/safe_fd.h
index cb4b46d..cb3612c 100644
--- a/brillo/files/safe_fd.h
+++ b/brillo/files/safe_fd.h
@@ -52,7 +52,8 @@ class SafeFD {
     kNoError = 0,
     kBadArgument,
     kNotInitialized,  // Invalid operation on a SafeFD that was not initialized.
-    kIOError,         // (e.g. called OpenExistingFile on a non-existent file)
+    kIOError,         // Check errno for specific cause.
+    kDoesNotExist,    // The specified path does not exist.
     kSymlinkDetected,
     kWrongType,  // (e.g. got a directory and expected a file)
     kWrongUID,
diff --git a/brillo/files/safe_fd_test.cc b/brillo/files/safe_fd_test.cc
index 878a937..60406fa 100644
--- a/brillo/files/safe_fd_test.cc
+++ b/brillo/files/safe_fd_test.cc
@@ -27,6 +27,7 @@ std::string to_string(brillo::SafeFD::Error err) {
     TO_STRING_HELPER(kBadArgument)
     TO_STRING_HELPER(kNotInitialized)
     TO_STRING_HELPER(kIOError)
+    TO_STRING_HELPER(kDoesNotExist)
     TO_STRING_HELPER(kSymlinkDetected)
     TO_STRING_HELPER(kWrongType)
     TO_STRING_HELPER(kWrongUID)
@@ -331,7 +332,16 @@ TEST_F(SafeFDTest, OpenExistingFile_NotInitialized) {
   ASSERT_FALSE(file.first.is_valid());
 }
 
+TEST_F(SafeFDTest, OpenExistingFile_DoesNotExist) {
+  SafeFD::SafeFDResult file = root_.OpenExistingFile(file_path_);
+  EXPECT_STR_EQ(file.second, SafeFD::Error::kDoesNotExist);
+  ASSERT_FALSE(file.first.is_valid());
+}
+
 TEST_F(SafeFDTest, OpenExistingFile_IOError) {
+  ASSERT_TRUE(WriteFile(""));
+  EXPECT_EQ(chmod(file_path_.value().c_str(), 0000), 0) << strerror(errno);
+
   SafeFD::SafeFDResult file = root_.OpenExistingFile(file_path_);
   EXPECT_STR_EQ(file.second, SafeFD::Error::kIOError);
   ASSERT_FALSE(file.first.is_valid());
@@ -366,8 +376,17 @@ TEST_F(SafeFDTest, OpenExistingDir_NotInitialized) {
   ASSERT_FALSE(dir.first.is_valid());
 }
 
+TEST_F(SafeFDTest, OpenExistingDir_DoesNotExist) {
+  SafeFD::SafeFDResult dir = root_.OpenExistingDir(sub_dir_path_);
+  EXPECT_STR_EQ(dir.second, SafeFD::Error::kDoesNotExist);
+  ASSERT_FALSE(dir.first.is_valid());
+}
+
 TEST_F(SafeFDTest, OpenExistingDir_IOError) {
-  SafeFD::SafeFDResult dir = root_.OpenExistingDir(file_path_);
+  ASSERT_TRUE(WriteFile(""));
+  EXPECT_EQ(chmod(sub_dir_path_.value().c_str(), 0000), 0) << strerror(errno);
+
+  SafeFD::SafeFDResult dir = root_.OpenExistingDir(sub_dir_path_);
   EXPECT_STR_EQ(dir.second, SafeFD::Error::kIOError);
   ASSERT_FALSE(dir.first.is_valid());
 }