_ Git - rust-lightning/blob - lightning-persister/src/util.rs

   1 use std::fs;
   2 use std::path::{Path, PathBuf};
   3
   4 #[cfg(not(target_os = "windows"))]
   5 use std::os::unix::io::AsRawFd;
   6
   7 pub(crate) trait DiskWriteable {
   8         fn write_to_file(&self, writer: &mut fs::File) -> Result<(), std::io::Error>;
   9 }
  10
  11 pub fn get_full_filepath(filepath: String, filename: String) -> String {
  12         let mut path = PathBuf::from(filepath);
  13         path.push(filename);
  14         path.to_str().unwrap().to_string()
  15 }
  16
  17 #[allow(bare_trait_objects)]
  18 pub(crate) fn write_to_file<D: DiskWriteable>(path: String, filename: String, data: &D) -> std::io::Result<()> {
  19         fs::create_dir_all(path.clone())?;
  20         // Do a crazy dance with lots of fsync()s to be overly cautious here...
  21         // We never want to end up in a state where we've lost the old data, or end up using the
  22         // old data on power loss after we've returned.
  23         // The way to atomically write a file on Unix platforms is:
  24         // open(tmpname), write(tmpfile), fsync(tmpfile), close(tmpfile), rename(), fsync(dir)
  25         let filename_with_path = get_full_filepath(path, filename);
  26         let tmp_filename = format!("{}.tmp", filename_with_path);
  27
  28         {
  29                 // Note that going by rust-lang/rust@d602a6b, on MacOS it is only safe to use
  30                 // rust stdlib 1.36 or higher.
  31                 let mut f = fs::File::create(&tmp_filename)?;
  32                 data.write_to_file(&mut f)?;
  33                 f.sync_all()?;
  34         }
  35         fs::rename(&tmp_filename, &filename_with_path)?;
  36         // Fsync the parent directory on Unix.
  37         #[cfg(not(target_os = "windows"))]
  38         {
  39                 let path = Path::new(&filename_with_path).parent().unwrap();
  40                 let dir_file = fs::OpenOptions::new().read(true).open(path)?;
  41                 unsafe { libc::fsync(dir_file.as_raw_fd()); }
  42         }
  43         Ok(())
  44 }
  45
  46 #[cfg(test)]
  47 mod tests {
  48         use super::{DiskWriteable, get_full_filepath, write_to_file};
  49         use std::fs;
  50         use std::io;
  51         use std::io::Write;
  52
  53         struct TestWriteable{}
  54         impl DiskWriteable for TestWriteable {
  55                 fn write_to_file(&self, writer: &mut fs::File) -> Result<(), io::Error> {
  56                         writer.write_all(&[42; 1])
  57                 }
  58         }
  59
  60         // Test that if the persister's path to channel data is read-only, writing
  61         // data to it fails. Windows ignores the read-only flag for folders, so this
  62         // test is Unix-only.
  63         #[cfg(not(target_os = "windows"))]
  64         #[test]
  65         fn test_readonly_dir() {
  66                 let test_writeable = TestWriteable{};
  67                 let filename = "test_readonly_dir_persister_filename".to_string();
  68                 let path = "test_readonly_dir_persister_dir";
  69                 fs::create_dir_all(path.to_string()).unwrap();
  70                 let mut perms = fs::metadata(path.to_string()).unwrap().permissions();
  71                 perms.set_readonly(true);
  72                 fs::set_permissions(path.to_string(), perms).unwrap();
  73                 match write_to_file(path.to_string(), filename, &test_writeable) {
  74                         Err(e) => assert_eq!(e.kind(), io::ErrorKind::PermissionDenied),
  75                         _ => panic!("Unexpected error message")
  76                 }
  77         }
  78
  79         // Test failure to rename in the process of atomically creating a channel
  80         // monitor's file. We induce this failure by making the `tmp` file a
  81         // directory.
  82         // Explanation: given "from" = the file being renamed, "to" = the
  83         // renamee that already exists: Windows should fail because it'll fail
  84         // whenever "to" is a directory, and Unix should fail because if "from" is a
  85         // file, then "to" is also required to be a file.
  86         #[test]
  87         fn test_rename_failure() {
  88                 let test_writeable = TestWriteable{};
  89                 let filename = "test_rename_failure_filename";
  90                 let path = "test_rename_failure_dir";
  91                 // Create the channel data file and make it a directory.
  92                 fs::create_dir_all(get_full_filepath(path.to_string(), filename.to_string())).unwrap();
  93                 match write_to_file(path.to_string(), filename.to_string(), &test_writeable) {
  94                         Err(e) => {
  95                                 #[cfg(not(target_os = "windows"))]
  96                                 assert_eq!(e.kind(), io::ErrorKind::Other);
  97                                 #[cfg(target_os = "windows")]
  98                                 assert_eq!(e.kind(), io::ErrorKind::PermissionDenied);
  99                         }
 100                         _ => panic!("Unexpected error message")
 101                 }
 102                 fs::remove_dir_all(path).unwrap();
 103         }
 104
 105         #[test]
 106         fn test_diskwriteable_failure() {
 107                 struct FailingWriteable {}
 108                 impl DiskWriteable for FailingWriteable {
 109                         fn write_to_file(&self, _writer: &mut fs::File) -> Result<(), std::io::Error> {
 110                                 Err(std::io::Error::new(std::io::ErrorKind::Other, "expected failure"))
 111                         }
 112                 }
 113
 114                 let filename = "test_diskwriteable_failure";
 115                 let path = "test_diskwriteable_failure_dir";
 116                 let test_writeable = FailingWriteable{};
 117                 match write_to_file(path.to_string(), filename.to_string(), &test_writeable) {
 118                         Err(e) => {
 119                                 assert_eq!(e.kind(), std::io::ErrorKind::Other);
 120                                 assert_eq!(e.get_ref().unwrap().to_string(), "expected failure");
 121                         },
 122                         _ => panic!("unexpected result")
 123                 }
 124                 fs::remove_dir_all(path).unwrap();
 125         }
 126
 127         // Test failure to create the temporary file in the persistence process.
 128         // We induce this failure by having the temp file already exist and be a
 129         // directory.
 130         #[test]
 131         fn test_tmp_file_creation_failure() {
 132                 let test_writeable = TestWriteable{};
 133                 let filename = "test_tmp_file_creation_failure_filename".to_string();
 134                 let path = "test_tmp_file_creation_failure_dir".to_string();
 135
 136                 // Create the tmp file and make it a directory.
 137                 let tmp_path = get_full_filepath(path.clone(), format!("{}.tmp", filename.clone()));
 138                 fs::create_dir_all(tmp_path).unwrap();
 139                 match write_to_file(path, filename, &test_writeable) {
 140                         Err(e) => {
 141                                 #[cfg(not(target_os = "windows"))]
 142                                 assert_eq!(e.kind(), io::ErrorKind::Other);
 143                                 #[cfg(target_os = "windows")]
 144                                 assert_eq!(e.kind(), io::ErrorKind::PermissionDenied);
 145                         }
 146                         _ => panic!("Unexpected error message")
 147                 }
 148         }
 149 }