fix: insufficient buf size when reading windows named pipe message #1778
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Ah, yeah. Forgot to set up formatting in the windows machine :) |
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Overall LGTM. Only things I'm wondering are:
- Can we add a test that sends several messages? E.g., generate some sequence of lengths to send, then spawn a background thread that sends messages of those lengths in those orders. Then on the main test thread, receive the messages and assert that the received lengths match.
- Can you run Tokio's test suite with these changes?
We also need @Thomasdezeeuw's ok, but with the above, I would be happy with this PR.
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The change passed Tokio's test suites, but the CI is failing on unexpected cfgs. I opened a PR to handle this, unless you have other ideas for the unexpected cfgs @Thomasdezeeuw @Darksonn |
src/sys/windows/named_pipe.rs
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| Err(e) if e.raw_os_error() == Some(ERROR_MORE_DATA as i32) => { | ||
| match me.remaining_size() { | ||
| Ok(rem) => { | ||
| buf.set_len(status.bytes_transferred() as usize); |
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I think this should be moved before the call to remaining_size as those bytes are already read.
| return; | ||
| } | ||
| Err(e) => { | ||
| io.read = State::Err(e); |
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I'm not sure about this. This makes it an unrecoverable error, but the original error is not. I feel like this is making the situation worse in case PeekNamedPipe returns an error.
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How is the original error recoverable?
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The original ERROR_MORE_DATA error is not really an error, it we actually read bytes, so it can be ignored.
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Ah ok, i thought you were referring to the err flow before the change.
Guess we can truncate it in this case
src/sys/windows/named_pipe.rs
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| let mut buf = match mem::replace(&mut io.read, State::None) { | ||
| State::None => me.get_buffer(), | ||
| State::InsufficientBufferSize(mut buf, rem) => { | ||
| buf.reserve_exact(rem); |
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This should have a limit. Otherwise we can allocate large amounts of memory.
| 0, | ||
| std::ptr::null_mut(), | ||
| std::ptr::null_mut(), | ||
| &mut remaining, |
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Is it guaranteed that ERROR_MORE_DATA is never returned for stream oriented named pipes?
Because according to the PeekNamedPipe docs (https://learn.microsoft.com/en-us/windows/win32/api/namedpipeapi/nf-namedpipeapi-peeknamedpipe) this will return 0 for streams. Which would mean we're effectively creating an infinite loop where we try to read using a buffer of length 0.
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I'd be surprised if ERROR_MORE_DATA is ever returned by stream mode named pipe.
But that's a fair point. We can just err out if PeekNamedPipe returned 0.
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In case PeekNamedPipe returns 0 we should probably just return the short-read buffer, not an error.
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That will happen only when it's stream mode, and we do not expect it to happen, no?
I think we should at least have a debug_assert in this case
Closes tokio-rs/tokio#6460
This PR allows handling
ERROR_MORE_DATAwhen the internal buffer size is less than the message in NamedPipe. WhenERROR_MORE_DATAis hit, the internal buffer will be resized according toPeekNamedPipeand the remaining message will be read through subsequent call toReadFile.Also see #1772 for more context.