[pbs-devel] [PATCH v8 pxar 14/69] format/encoder/decoder: new pxar entry type `Version`
Fabian Grünbichler
f.gruenbichler at proxmox.com
Mon Jun 3 13:25:58 CEST 2024
On May 28, 2024 11:42 am, Christian Ebner wrote:
> Introduces a new pxar format entry type `Version` and the associated
> encoder and decoder methods. The format version entry is only allowed
> once, as the first entry of the pxar archive, marked with a
> `PXAR_FORMAT_VERSION` header followed by the encoded version number.
> If not present, the default format version 1 is assumed as encoding
> format for the archive.
>
> The entry allows to early detect incompatibility with an encoded
> archive and bail or switch mode based on the encountered version.
>
> The format version entry is not backwards compatible to pxar format
> version 1.
>
> Signed-off-by: Christian Ebner <c.ebner at proxmox.com>
it seems there are still some checks missing for this, if I build
patched PBS versions with an added Version 3 but lacking decode support,
I get the expected error in a lot of places, but can for example use the
`pxar-file-download` endpoint to download files from the archive, even
though the server should choke on the archive since it's using an
unknown value in the version header/entry..
ideally they'd be added here in pxar (since who knows, the next format
break might be entirely transparent to PBS :))
> ---
> changes since version 7:
> - no changes
>
> changes since version 6:
> - no changes
>
> examples/mk-format-hashes.rs | 5 +++++
> src/accessor/mod.rs | 21 ++++++++++++++++++--
> src/decoder/mod.rs | 37 ++++++++++++++++++++++++++++++++++--
> src/encoder/mod.rs | 37 +++++++++++++++++++++++++++++++++---
> src/format/mod.rs | 11 +++++++++++
> src/lib.rs | 3 +++
> tests/simple/fs.rs | 1 +
> 7 files changed, 108 insertions(+), 7 deletions(-)
>
> diff --git a/examples/mk-format-hashes.rs b/examples/mk-format-hashes.rs
> index 35cff99..e5d69b1 100644
> --- a/examples/mk-format-hashes.rs
> +++ b/examples/mk-format-hashes.rs
> @@ -1,6 +1,11 @@
> use pxar::format::hash_filename;
>
> const CONSTANTS: &[(&str, &str, &str)] = &[
> + (
> + "Pxar format version entry, fallback to version 1 if not present",
> + "PXAR_FORMAT_VERSION",
> + "__PROXMOX_FORMAT_VERSION__",
> + ),
> (
> "Beginning of an entry (current version).",
> "PXAR_ENTRY",
> diff --git a/src/accessor/mod.rs b/src/accessor/mod.rs
> index c3a5e14..faab430 100644
> --- a/src/accessor/mod.rs
> +++ b/src/accessor/mod.rs
> @@ -299,11 +299,19 @@ impl<T: Clone + ReadAt> AccessorImpl<T> {
> PathBuf::new(),
> )
> .await?;
> - let entry = decoder
> + let mut entry = decoder
> .next()
> .await
> .ok_or_else(|| io_format_err!("unexpected EOF while decoding file entry"))??;
>
> + // Skip over possible Version and Prelude before the root entry of type Directory
> + if let EntryKind::Version(_) = entry.kind() {
> + entry = decoder
> + .next()
> + .await
> + .ok_or_else(|| io_format_err!("unexpected EOF while decoding directory entry"))??;
> + }
> +
> Ok(FileEntryImpl {
> input: self.input.clone(),
> entry,
> @@ -528,10 +536,19 @@ impl<T: Clone + ReadAt> DirectoryImpl<T> {
> file_name: Option<&Path>,
> ) -> io::Result<(Entry, DecoderImpl<SeqReadAtAdapter<T>>)> {
> let mut decoder = self.get_decoder(entry_range, file_name).await?;
> - let entry = decoder
> + let mut entry = decoder
> .next()
> .await
> .ok_or_else(|| io_format_err!("unexpected EOF while decoding directory entry"))??;
> +
> + // Skip over possible Version and Prelude before the root entry of type Directory
> + if let EntryKind::Version(_) = entry.kind() {
> + entry = decoder
> + .next()
> + .await
> + .ok_or_else(|| io_format_err!("unexpected EOF while decoding directory entry"))??;
> + }
> +
> Ok((entry, decoder))
> }
>
> diff --git a/src/decoder/mod.rs b/src/decoder/mod.rs
> index 19b1b5c..43c83ae 100644
> --- a/src/decoder/mod.rs
> +++ b/src/decoder/mod.rs
> @@ -18,7 +18,7 @@ use std::task::{Context, Poll};
>
> use endian_trait::Endian;
>
> -use crate::format::{self, Header};
> +use crate::format::{self, FormatVersion, Header};
> use crate::util::{self, io_err_other};
> use crate::{Entry, EntryKind, Metadata, PxarVariant};
>
> @@ -169,10 +169,14 @@ pub(crate) struct DecoderImpl<T> {
> /// 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,
> + /// The format version as determined by the format version header
> + version: format::FormatVersion,
> }
>
> +#[derive(Clone, PartialEq)]
> enum State {
> Begin,
> + Root,
> Default,
> InPayload {
> offset: u64,
> @@ -245,6 +249,7 @@ impl<I: SeqRead> DecoderImpl<I> {
> with_goodbye_tables: false,
> payload_consumed,
> eof_after_entry,
> + version: FormatVersion::default(),
> })
> }
>
> @@ -257,7 +262,19 @@ impl<I: SeqRead> DecoderImpl<I> {
> loop {
> match self.state {
> State::Eof => return Ok(None),
> - State::Begin => return self.read_next_entry().await.map(Some),
> + State::Begin => {
> + let entry = self.read_next_entry().await.map(Some);
> + if let Ok(Some(ref entry)) = entry {
> + if let EntryKind::Version(version) = entry.kind() {
> + self.version = version.clone();
> + self.state = State::Root;
> + }
> + }
> + return entry;
> + }
> + State::Root => {
> + return self.read_next_entry().await.map(Some);
> + }
> State::Default => {
> // we completely finished an entry, so now we're going "up" in the directory
> // hierarchy and parse the next PXAR_FILENAME or the PXAR_GOODBYE:
> @@ -388,6 +405,7 @@ impl<I: SeqRead> DecoderImpl<I> {
> }
>
> async fn read_next_entry_or_eof(&mut self) -> io::Result<Option<Entry>> {
> + let previous_state = self.state.clone();
> self.state = State::Default;
> self.entry.clear_data();
>
> @@ -407,6 +425,14 @@ impl<I: SeqRead> DecoderImpl<I> {
> self.entry.metadata = Metadata::default();
> self.entry.kind = EntryKind::Hardlink(self.read_hardlink().await?);
>
> + Ok(Some(self.entry.take()))
> + } else if header.htype == format::PXAR_FORMAT_VERSION {
> + if previous_state != State::Begin {
> + io_bail!("Got format version entry at unexpected position");
> + }
> + self.current_header = header;
> + self.entry.kind = EntryKind::Version(self.read_format_version().await?);
> +
> Ok(Some(self.entry.take()))
> } else if header.htype == format::PXAR_ENTRY || header.htype == format::PXAR_ENTRY_V1 {
> if header.htype == format::PXAR_ENTRY {
> @@ -766,6 +792,13 @@ impl<I: SeqRead> DecoderImpl<I> {
> self.current_header.check_header_size()?;
> seq_read_entry(self.input.archive_mut()).await
> }
> +
> + async fn read_format_version(&mut self) -> io::Result<format::FormatVersion> {
> + match seq_read_entry(self.input.archive_mut()).await? {
> + 2u64 => Ok(format::FormatVersion::Version2),
> + version => io_bail!("unexpected pxar format version {version}"),
nit/follow-up: I'd maybe strip the pxar here and in the other format
related bail messages? no other errors here include it, and I think it's
pretty much always implied by the context?
also see below
> + }
> + }
> }
>
> /// Reader for file contents inside a pxar archive.
> diff --git a/src/encoder/mod.rs b/src/encoder/mod.rs
> index b579e18..4bed040 100644
> --- a/src/encoder/mod.rs
> +++ b/src/encoder/mod.rs
> @@ -17,7 +17,7 @@ use endian_trait::Endian;
>
> use crate::binary_tree_array;
> use crate::decoder::{self, SeqRead};
> -use crate::format::{self, GoodbyeItem, PayloadRef};
> +use crate::format::{self, FormatVersion, GoodbyeItem, PayloadRef};
> use crate::{Metadata, PxarVariant};
>
> pub mod aio;
> @@ -326,6 +326,8 @@ pub(crate) struct EncoderImpl<'a, T: SeqWrite + 'a> {
> /// Since only the "current" entry can be actively writing files, we share the file copy
> /// buffer.
> file_copy_buffer: Arc<Mutex<Vec<u8>>>,
> + /// Pxar format version to encode
> + version: format::FormatVersion,
> }
>
> impl<'a, T: SeqWrite + 'a> Drop for EncoderImpl<'a, T> {
> @@ -350,11 +352,14 @@ impl<'a, T: SeqWrite + 'a> EncoderImpl<'a, T> {
> }
>
> let mut state = EncoderState::default();
> - if let Some(payload_output) = output.payload_mut() {
> + let version = if let Some(payload_output) = output.payload_mut() {
> let header = format::Header::with_content_size(format::PXAR_PAYLOAD_START_MARKER, 0);
> header.check_header_size()?;
> seq_write_struct(payload_output, header, &mut state.payload_write_position).await?;
> - }
> + format::FormatVersion::Version2
> + } else {
> + format::FormatVersion::Version1
> + };
>
> let mut this = Self {
> output,
> @@ -363,8 +368,10 @@ impl<'a, T: SeqWrite + 'a> EncoderImpl<'a, T> {
> file_copy_buffer: Arc::new(Mutex::new(unsafe {
> crate::util::vec_new_uninitialized(1024 * 1024)
> })),
> + version,
> };
>
> + this.encode_format_version().await?;
> this.encode_metadata(metadata).await?;
> let state = this.state_mut()?;
> state.files_offset = state.position();
> @@ -547,6 +554,10 @@ impl<'a, T: SeqWrite + 'a> EncoderImpl<'a, T> {
> file_size: u64,
> payload_offset: PayloadOffset,
> ) -> io::Result<LinkOffset> {
> + if self.version == FormatVersion::Version1 {
> + io_bail!("payload references not supported pxar format version 1");
> + }
> +
> if self.output.payload().is_none() {
> io_bail!("unable to add payload reference");
> }
> @@ -762,6 +773,26 @@ impl<'a, T: SeqWrite + 'a> EncoderImpl<'a, T> {
> Ok(())
> }
>
> + async fn encode_format_version(&mut self) -> io::Result<()> {
> + let version_bytes = match self.version {
> + format::FormatVersion::Version1 => return Ok(()),
> + format::FormatVersion::Version2 => 2u64.to_le_bytes(),
nit: the representation here and on the read side is still pretty far
from eachother, it might be nice to move them next to eachother into a
pair of serialize/deserialize..
> + };
> +
> + let (mut output, state) = self.output_state()?;
> + if state.write_position != 0 {
> + io_bail!("pxar format version must be encoded at the beginning of an archive");
> + }
> +
> + seq_write_pxar_entry(
> + output.archive_mut(),
> + format::PXAR_FORMAT_VERSION,
> + &version_bytes,
> + &mut state.write_position,
> + )
> + .await
> + }
> +
> async fn encode_metadata(&mut self, metadata: &Metadata) -> io::Result<()> {
> let (mut output, state) = self.output_state()?;
> seq_write_pxar_struct_entry(
> diff --git a/src/format/mod.rs b/src/format/mod.rs
> index 6519bfc..9b66fe2 100644
> --- a/src/format/mod.rs
> +++ b/src/format/mod.rs
> @@ -6,6 +6,7 @@
> //! item data.
> //!
> //! An archive contains items in the following order:
> +//! * `FORMAT_VERSION` -- (optional for v1), version of encoding format
> //! * `ENTRY` -- containing general stat() data and related bits
> //! * `XATTR` -- one extended attribute
> //! * ... -- more of these when there are multiple defined
> @@ -80,6 +81,8 @@ pub mod mode {
> }
>
> // Generated by `cargo run --example mk-format-hashes`
> +/// Pxar format version entry, fallback to version 1 if not present
> +pub const PXAR_FORMAT_VERSION: u64 = 0x730f6c75df16a40d;
> /// Beginning of an entry (current version).
> pub const PXAR_ENTRY: u64 = 0xd5956474e588acef;
> /// Previous version of the entry struct
> @@ -186,6 +189,7 @@ impl Header {
> impl Display for Header {
> fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
> let readable = match self.htype {
> + PXAR_FORMAT_VERSION => "FORMAT_VERSION",
> PXAR_FILENAME => "FILENAME",
> PXAR_SYMLINK => "SYMLINK",
> PXAR_HARDLINK => "HARDLINK",
> @@ -551,6 +555,13 @@ impl From<&std::fs::Metadata> for Stat {
> }
> }
>
> +#[derive(Clone, Debug, Default, PartialEq)]
> +pub enum FormatVersion {
> + #[default]
> + Version1,
> + Version2,
> +}
> +
> #[derive(Clone, Debug)]
> pub struct Filename {
> pub name: Vec<u8>,
> diff --git a/src/lib.rs b/src/lib.rs
> index bafdfe4..7e5b48f 100644
> --- a/src/lib.rs
> +++ b/src/lib.rs
> @@ -342,6 +342,9 @@ impl Acl {
> /// Identifies whether the entry is a file, symlink, directory, etc.
> #[derive(Clone, Debug)]
> pub enum EntryKind {
> + /// Pxar file format version
> + Version(format::FormatVersion),
> +
> /// Symbolic links.
> Symlink(format::Symlink),
>
> diff --git a/tests/simple/fs.rs b/tests/simple/fs.rs
> index 4284805..8a8c607 100644
> --- a/tests/simple/fs.rs
> +++ b/tests/simple/fs.rs
> @@ -229,6 +229,7 @@ impl Entry {
> })?))
> };
> match item.kind() {
> + PxarEntryKind::Version(_) => continue,
> PxarEntryKind::GoodbyeTable => break,
> PxarEntryKind::File { size, .. } => {
> let mut data = Vec::new();
> --
> 2.39.2
>
>
>
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