The host sealed every packet with ~3 heap allocations: aes-gcm's convenience
encrypt() allocates the ciphertext Vec, seal_for_wire allocates the seq||ct||tag
wire Vec, and seal_frame allocated a fresh Vec<Vec<u8>> per frame. At line rate
(~250k–500k pkt/s for 2.5–5 Gbps) that's the single-core allocator wall.
- SessionCrypto::seal_in_place uses AeadInPlace::encrypt_in_place_detached to
encrypt into the caller's buffer and write the detached tag at the end —
byte-identical to seal's ciphertext||tag, no allocation (unit-tested for byte
equality + decrypt).
- Session keeps a wire_pool the caller returns via reclaim_wires; seal_frame
seals each packet in place into the reused buffers (clear() keeps capacity), so
after warmup there's no per-packet ciphertext/wire allocation. paced_submit and
submit_frame reclaim the pool after sending.
End-to-end encrypted/lossless multi-frame tests stay green (validates the pool
reuse doesn't corrupt across frames). Next: write packetize directly into a
contiguous send buffer (kills the remaining shard allocs + GSO's coalescing copy).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
enricobuehler
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