maskit opened a new pull request, #13338:
URL: https://github.com/apache/trafficserver/pull/13338
## Summary
Reduces per-connection memory work in the `jax_fingerprint` plugin and makes
the set of compiled-in fingerprint methods a configure-time choice.
- **ContextMap** is now an inline fixed-size table of `(method-name,
JAxContext*)` pairs, replacing the `std::unordered_map<std::string,
JAxContext*>` used previously. Lookup is a short linear scan; the bucket array
and node allocations that the map performed on every TLS connection are gone.
- **`set_fingerprint`** takes `std::string_view`, dropping the temporary
`std::string` that was materialised at every call site purely to bind a `const
std::string &` parameter.
- **`ENABLE_JAX_METHODS`** is a new CMake cache variable (default
`"ja3;ja4;ja4h"`) that drives, from a single list:
- which method subdirectories contribute sources to the plugin and to
`test_jax`,
- which `ENABLE_JAX_METHOD_<NAME>` preprocessor defines are set, and
- the value of `JAX_FINGERPRINT_MAX_METHODS` (the inline context-table
size, derived from the list length).
Build slim: `cmake -B build -DENABLE_JAX_METHODS="ja4"`. Empty list or
unknown directory name causes a `FATAL_ERROR` at configure time.
- **`plugin.cc`** dispatcher is now a `constexpr` table of `Method const *`
entries, each gated by the per-method `ENABLE_JAX_METHOD_*` macro. The
dispatcher and the method `#include`s are the only place in the plugin that
names concrete methods; `method.h` stays method-agnostic.
- **`README`** in the plugin directory documents the per-method file layout,
the build-time switches, and the file-naming rules the CMake glob relies on
(including the `tls_client_hello_summary.cc` historical carve-out and how to
handle similar cases going forward).
## Test plan
- [x] `cmake --build my-b-bssl -t jax_fingerprint` — default
(`ja3;ja4;ja4h`) builds cleanly.
- [x] `cmake --build my-b-bssl -t test_jax` and run `test_jax` — 67
assertions across 5 Catch2 test cases pass.
- [x] `cmake --build my-b-bssl -t format` — clang-format / cmake-format
clean.
- [x] AuTest `jax_fingerprint*` passes against the installed plugin.
- [x] Slim build: `cmake -B my-b-bssl -DENABLE_JAX_METHODS="ja4"` — only
`ja4/*.cc` compiled into the plugin.
- [x] Negative configure paths: `-DENABLE_JAX_METHODS=""` and
`-DENABLE_JAX_METHODS="ja99"` both fail at configure time with the intended
messages.
## Notes for reviewers
- `ContextMap` keys are `std::string_view`s that alias `Method::name` (which
is itself a `string_view` pointing at a string literal). The slot table stays
valid as long as the `Method` struct does, i.e. for the lifetime of the process.
- The plugin's other lookup against a heterogeneous-lookup hash (the SNI
server-name set in `plugin.cc`) is unchanged. The
`__cpp_lib_generic_unordered_lookup` `#ifdef` there is still needed and is
unrelated to ContextMap.
- `JAX_FINGERPRINT_MAX_METHODS` is not a separate user knob; CMake derives
it from the length of `ENABLE_JAX_METHODS`. The `#ifndef ... #define ... 8` in
`context_map.h` is a fallback so the header is valid when compiled standalone
(e.g. IDE indexing). A `static_assert` in `context_map.h` enforces a minimum of
1, and `set()` `TSReleaseAssert`s on overflow.
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