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Dario Gabriel LipicarandClaude Opus 5 421624641a feat: wrap nimbus libverifproxy as a Logos module
Adds `verified_proxy_module`, a universal C++ core module over status-im's
`libverifproxy` — the C library form of nimbus_verified_proxy. Where
`eth_rpc_module` forwards JSON-RPC to a provider and trusts the answer, this
verifies every response against the beacon-chain light client's attested
execution state, so a lying provider produces an error rather than a wrong
value.

Nobody had packaged libverifproxy with Nix before: upstream's flake builds the
verified-proxy *binary* but not the library, and a global code search for
`libverifproxy` in nix files returns nothing. Rather than write a derivation,
flake.nix re-targets upstream's own — `.override { targets = ["libverifproxy"]; }`
composes because callPackage's makeOverridable merges previously-applied args,
so their pinned Nim survives — and then fixes the three things that break:

  * installPhase installs only `-type f -executable` into $out/bin, so a .a and
    a .h yield an EMPTY $out (and installCheckPhase then runs the literal
    string "$out/bin/* --version");
  * env.NIMFLAGS is ASSIGNED, not appended, so ours have to extend it;
  * preBuild builds vendored RocksDB unconditionally although `make
    libverifproxy` never reaches that target. `nm -u` on the result confirms
    zero rocksdb references, so it is dropped rather than swapped for
    dynamicRocksDB (which on Windows would demand a *cross* RocksDB).

Three NIMFLAGS additions are load-bearing rather than tuning:

  * `-d:noSignalHandler` — library/nim.cfg omits it, so NimMain() would install
    Nim's SIGINT/SIGSEGV/SIGABRT handlers over the HOST's. Verified by dlopen'ing
    a probe and comparing sigaction before/after: the host's handler survives.
  * `--passC:-fPIC` — Nim only adds it when optGenDynLib is set, which
    --app:staticlib does not; upstream's dist script adds it for linux-arm64
    only. The archive is linked into a SHARED plugin.
  * `-d:release --debugger:off` — upstream ships debug info, which dominates
    the artifact (~99MB uncompressed in the release tarballs vs 31MB here).

The library can also take the host process down, which a plugin cannot tolerate,
so ProxyConfig whitelists the two fields that reach a Nim `quit()`: an
unrecognised `eth2Network` reaches getMetadataForNetwork's `fatal` + `quit 1`,
and any `logLevel` Nim's updateLogLevel rejects reaches setupLogging's `quit 1`.
Neither is validated upstream. Everything else (bad JSON, missing
trustedBlockRoot, malformed URL) is already caught and turned into a NULL
return, so validating it only improves the message.

ProxyRuntime owns the one thread that may touch the C ABI at all: the library
spawns none, startVerifProxy blocks through an unbounded prologue, and
setupForeignThreadGc/tearDownForeignThreadGc are bound to start/stop. Notable
consequences encoded here:

  * processVerifProxyTasks only poll()s while pendingCalls > 0, so an IDLE PROXY
    DOES NOT ADVANCE ITS LIGHT CLIENT. The heartbeat is
    proxyCall("eth_syncing","[]"), which drives beaconSync() and touches no
    execution backend. Its return value is a hardcoded `false` and useless; its
    error string is the only machine-readable sync-health signal the ABI has.
  * Drain BEFORE stopVerifProxy: it sets ctx.stop, which processVerifProxyTasks
    checks before polling, so afterwards no callback can ever fire.
  * Call slots use joint ownership (waiter + heap CallBox) rather than
    storage-module's `abandoned` flag, so a late callback after a timeout is
    safe by construction. There is no per-call cancel in the C API.
  * concurrency:"multi" spawns a QThread per call rather than using a bounded
    pool, so admission control is mandatory, not a nicety.

All ~60 eth_*/op_* entry points can route through one FFI path, because
proxyCall is a string `case` over the same procs the typed C exports call.
This commit lands 8 representative methods covering every wire type; the rest
are mechanical.

Verified on aarch64-darwin: the archive links into a .dylib; NimMain initialises
under dlopen; a bad config returns NULL rather than quitting; the plugin builds
at 15MB with the archive absorbed (hence `include: []`); and 28/28 unit tests
pass against a mocked C library that — unlike mock_libstorage — queues
completions and drains them only from the pump, so the cross-thread design is
actually exercised.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
2026-08-20 22:54:33 -03:00

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C++

#include <logos_test.h>
LOGOS_TEST_MAIN()