test: cover large Client/ServerHello packets - #3299
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Adds a bach simulation of the handshake latency regression that appears when post-quantum key exchange (s2n-tls policy 20250721) makes the first flight too large for a PTO probe to carry and the initial MTU is set to ~9kb. Measured in simulated time at a 1ms RTT on a 1500-byte path, with base_mtu 1450 and initial_mtu 8940 on both endpoints: * classical ClientHello - 10ms * ML-KEM ClientHello - 191ms * ML-KEM ClientHello, initial_mtu = base_mtu - 9ms w/o client buffering * ML-KEM ClientHello, initial_mtu = base_mtu - 5ms w/ client buffering This is essentially adding a test case demonstrating the fixes in aws#3295 and aws#3296 work.
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Description of changes:
Adds a bach simulation of the handshake latency regression that appears when post-quantum key exchange (s2n-tls policy 20250721) makes the first flight too large for a PTO probe to carry and the initial MTU is set to ~9kb.
Measured in simulated time at a 1ms RTT on a 1500-byte path, with base_mtu 1450 and initial_mtu 8940 on both endpoints:
This is essentially adding a test case demonstrating the fixes in #3295 and #3296 work. We don't integrate this into s2n-quic-dc directly -- maybe we should also do that, but this was easier.
By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.