[pbs-devel] [PATCH pxar] fix `decode_entry` on special files

Dominik Csapak d.csapak at proxmox.com
Tue Dec 15 12:08:53 CET 2020


looks good AFAICT
fixes the problem with fifo/sockets

Tested-By: Dominik Csapak <d.csapak at proxmox.com>

On 12/15/20 11:37 AM, Wolfgang Bumiller wrote:
> When using the random accessor to access FIFOs or sockets,
> the ranged reader limits the data to only that entry, and
> the `decode_entry` will never see a `PAYLOAD` or
> `GOODBYE_TABLE` item to finish the entry.
> Instead, it'll reach EOF and we need to handle this.
> The accessor now tells the decoder to expect EOF as a valid
> condition for ending the entry.
> 
> Signed-off-by: Wolfgang Bumiller <w.bumiller at proxmox.com>
> ---
> 
> The included testcase previously failed with
>      "failed to decode entry for fifo0"
> 
>   src/accessor/mod.rs  |  2 +-
>   src/decoder/mod.rs   | 52 +++++++++++++++++++++++++++++++++++---------
>   tests/simple/main.rs | 46 +++++++++++++++++++++++++++++++++++++++
>   3 files changed, 89 insertions(+), 11 deletions(-)
> 
> diff --git a/src/accessor/mod.rs b/src/accessor/mod.rs
> index 0ab03a6..d02dc13 100644
> --- a/src/accessor/mod.rs
> +++ b/src/accessor/mod.rs
> @@ -229,7 +229,7 @@ async fn get_decoder<T: ReadAt>(
>       entry_range: Range<u64>,
>       path: PathBuf,
>   ) -> io::Result<DecoderImpl<SeqReadAtAdapter<T>>> {
> -    Ok(DecoderImpl::new_full(SeqReadAtAdapter::new(input, entry_range), path).await?)
> +    Ok(DecoderImpl::new_full(SeqReadAtAdapter::new(input, entry_range), path, true).await?)
>   }
>   
>   // NOTE: This performs the Decoder::read_next_item() behavior! Keep in mind when changing!
> diff --git a/src/decoder/mod.rs b/src/decoder/mod.rs
> index fcc2dd9..2a5e79a 100644
> --- a/src/decoder/mod.rs
> +++ b/src/decoder/mod.rs
> @@ -155,6 +155,10 @@ pub(crate) struct DecoderImpl<T> {
>       path_lengths: Vec<usize>,
>       state: State,
>       with_goodbye_tables: bool,
> +
> +    /// The random access code uses decoders for sub-ranges which may not end in a `PAYLOAD` for
> +    /// entries like FIFOs or sockets, so there we explicitly allow an item to terminate with EOF.
> +    eof_after_entry: bool,
>   }
>   
>   enum State {
> @@ -191,14 +195,18 @@ pub(crate) enum ItemResult {
>   
>   impl<I: SeqRead> DecoderImpl<I> {
>       pub async fn new(input: I) -> io::Result<Self> {
> -        Self::new_full(input, "/".into()).await
> +        Self::new_full(input, "/".into(), false).await
>       }
>   
>       pub(crate) fn input(&self) -> &I {
>           &self.input
>       }
>   
> -    pub(crate) async fn new_full(input: I, path: PathBuf) -> io::Result<Self> {
> +    pub(crate) async fn new_full(
> +        input: I,
> +        path: PathBuf,
> +        eof_after_entry: bool,
> +    ) -> io::Result<Self> {
>           let this = DecoderImpl {
>               input,
>               current_header: unsafe { mem::zeroed() },
> @@ -210,6 +218,7 @@ impl<I: SeqRead> DecoderImpl<I> {
>               path_lengths: Vec::new(),
>               state: State::Begin,
>               with_goodbye_tables: false,
> +            eof_after_entry,
>           };
>   
>           // this.read_next_entry().await?;
> @@ -383,7 +392,14 @@ impl<I: SeqRead> DecoderImpl<I> {
>   
>               self.current_header = unsafe { mem::zeroed() };
>   
> -            while self.read_next_item().await? != ItemResult::Entry {}
> +            loop {
> +                match self.read_next_item_or_eof().await? {
> +                    Some(ItemResult::Entry) => break,
> +                    Some(ItemResult::Attribute) => continue,
> +                    None if self.eof_after_entry => break,
> +                    None => io_bail!("unexpected EOF in entry"),
> +                }
> +            }
>   
>               if self.entry.is_dir() {
>                   self.path_lengths
> @@ -402,24 +418,40 @@ impl<I: SeqRead> DecoderImpl<I> {
>               .ok_or_else(|| io_format_err!("unexpected EOF"))
>       }
>   
> +    async fn read_next_item(&mut self) -> io::Result<ItemResult> {
> +        match self.read_next_item_or_eof().await? {
> +            Some(item) => Ok(item),
> +            None => io_bail!("unexpected EOF"),
> +        }
> +    }
> +
> +    // NOTE: The random accessor will decode FIFOs and Sockets in a decoder instance with a ranged
> +    // reader so there is no PAYLOAD or GOODBYE TABLE to "end" an entry.
> +    //
>       // NOTE: This behavior method is also recreated in the accessor's `get_decoder_at_filename`
>       // function! Keep in mind when changing!
> -    async fn read_next_item(&mut self) -> io::Result<ItemResult> {
> -        self.read_next_header().await?;
> -        self.read_current_item().await
> +    async fn read_next_item_or_eof(&mut self) -> io::Result<Option<ItemResult>> {
> +        match self.read_next_header_or_eof().await? {
> +            Some(()) => self.read_current_item().await.map(Some),
> +            None => Ok(None),
> +        }
>       }
>   
> -    async fn read_next_header(&mut self) -> io::Result<()> {
> +    async fn read_next_header_or_eof(&mut self) -> io::Result<Option<()>> {
>           let dest = unsafe {
>               std::slice::from_raw_parts_mut(
>                   &mut self.current_header as *mut Header as *mut u8,
>                   size_of_val(&self.current_header),
>               )
>           };
> -        seq_read_exact(&mut self.input, dest).await?;
> -        self.current_header.check_header_size()?;
>   
> -        Ok(())
> +        match seq_read_exact_or_eof(&mut self.input, dest).await? {
> +            Some(()) => {
> +                self.current_header.check_header_size()?;
> +                Ok(Some(()))
> +            }
> +            None => Ok(None),
> +        }
>       }
>   
>       /// Read the next item, the header is already loaded.
> diff --git a/tests/simple/main.rs b/tests/simple/main.rs
> index c73ca10..f15a0f5 100644
> --- a/tests/simple/main.rs
> +++ b/tests/simple/main.rs
> @@ -42,6 +42,9 @@ fn test1() {
>   
>       assert!(!file.is_empty(), "encoder did not write any data");
>   
> +    // may be useful for testing...
> +    // std::fs::write("myarchive.pxar", &file).expect("failed to write out test archive");
> +
>       let mut input = &file[..];
>       let mut decoder = decoder::Decoder::from_std(&mut input).expect("failed to create decoder");
>       let decoded_fs =
> @@ -53,6 +56,7 @@ fn test1() {
>           .expect("failed to create random access reader for encoded archive");
>   
>       check_bunzip2(&accessor);
> +    check_run_special_files(&accessor);
>   }
>   
>   fn check_bunzip2(accessor: &accessor::Accessor<&[u8]>) {
> @@ -85,3 +89,45 @@ fn check_bunzip2(accessor: &accessor::Accessor<&[u8]>) {
>   
>       assert_eq!(content, "This is the bzip2 executable");
>   }
> +
> +fn check_run_special_files(accessor: &accessor::Accessor<&[u8]>) {
> +    let rundir = accessor
> +        .open_root()
> +        .expect("failed to open root of encoded archive")
> +        .lookup("run")
> +        .expect("failed to open /run in encoded archive")
> +        .expect("missing /run in encoded archive")
> +        .enter_directory()
> +        .expect("expected /run to be a directory in the test archive");
> +
> +    assert_eq!(rundir.entry_count(), 2, "expected 2 entries in /run");
> +
> +    let mut rd = rundir.read_dir();
> +    let fifo0 = rd
> +        .next()
> +        .expect("expected 'fifo0' entry in rundir")
> +        .expect("failed to get first (fifo0) entry in test archive /run directory");
> +    assert_eq!(
> +        fifo0.file_name(),
> +        Path::new("fifo0"),
> +        "expected first file in /run to be fifo0"
> +    );
> +
> +    let _entry = fifo0
> +        .decode_entry()
> +        .expect("failed to decode entry for fifo0");
> +
> +    let sock0 = rd
> +        .next()
> +        .expect("expected 'sock0' entry in rundir")
> +        .expect("failed to get second (sock0) entry in test archive /run directory");
> +    assert_eq!(
> +        sock0.file_name(),
> +        Path::new("sock0"),
> +        "expected second file in /run to be sock0"
> +    );
> +
> +    let _entry = sock0
> +        .decode_entry()
> +        .expect("failed to decode entry for sock0");
> +}
> 





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