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Re: [tor-bugs] #27319 [Core Tor/Tor]: remove buf_get_oldest_chunk_timestamp()
#27319: remove buf_get_oldest_chunk_timestamp()
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Reporter: cypherpunks3 | Owner: (none)
Type: defect | Status: new
Priority: Medium | Milestone: Tor: unspecified
Component: Core Tor/Tor | Version:
Severity: Normal | Resolution:
Keywords: datatypes, buffers, oom | Actual Points:
Parent ID: #23878 | Points:
Reviewer: | Sponsor:
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Comment (by cypherpunks3):
Replying to [comment:2 nickm]:
> we need to track the age of the data in the buffer, to implement the
defense for this: https://www.nrl.navy.mil/itd/chacs/sites/edit-
www.nrl.navy.mil.itd.chacs/files/pdfs/13-1231-3743.pdf
>
Thanks for the additional context.
Could we
- replace the per-chunk timestamp with a timestamp stored in `struct
connection_t`, which is updated with the last point in time that `outbuf`
had been empty? Move age-calculation logic there.
- Or if not that, keep a uint32_t field per chunk, but have it be an
opaque tag kept at zero normally, but callers that care about timestamps
like connection.c can call `buf_tag_new_chunks(buf_t, uint32_t)` after
writing to the buffer, assigning that uint32_t to any chunk that currently
has a tag of zero (ie, any newly created chunks). Then OOM can call
`buf_get_head_tag()` to retrieve the number and calculate its age.
Technically, `buf_get_oldest_chunk_timestamp()` is a misnomer anyway,
since it calculates the age from the timestamp and returns its age in
seconds, not the timestamp.
--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/27319#comment:3>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
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