elsloo opened a new pull request, #9534:
URL: https://github.com/apache/trafficserver/pull/9534
- Initial attempt to backport the fix (#9527) for the duplicate header bug
on revalidations to 9.2.x.
- Inner loop's auto `spot2` iterator contains a member variable, `_block`
that references the memory address of the response headers, not the cached
headers
- Method called on the `cached_headers` object uses a memory address, not
a named header, and leads to all response headers being deleted from the
duplicate header forward
- Once response headers are deleted, the first duplicate header is written
to the cached headers as a new and *additional* field which leads to
duplication in the cached object's headers, then the current iteration ends
- The iterator of the outer loop then attempts to increment forward one
step via the overridden `++` operator on `spot`, and due to header slot checks
via `MIMEField::is_live()` within `MIMEHdrImpl::iterator::step()`, `_slot` is
incremented to `limit` and iteration of the outer loop halts, because all
response headers from that point forward were deleted in the prior iteration
- This change moves away from the address-based approach to delete the
header and instead uses the header name
- Using the header name instead of relying on header alignment also fixes
a secondary issue that could arise if response header ordering does not match
the cached object's header ordering
- Using the header name is slightly less efficient due to having to call
`find_header`, however, this is necessary to ensure the cached headers are
correctly removed before the response headers are merged into the cached object
- Using a slightly less efficient approach that occurs only on successful
revalidations that also contain duplicate headers should be acceptable given
the tradeoff is allowing duplication if response header ordering differs from
the cached object
- Due to the existing logic, if a cached header is *not* in the response, it
will remain in the cached object's headers
Thanks to Masakazu and Leif for providing the unit test and helping with the
fix, respectively.
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: [email protected]
For queries about this service, please contact Infrastructure at:
[email protected]
