chunkloris: hypercorn (http/3)
on this page
part of the chunkloris per-chunk amplification survey. this page is the per-server record for hypercorn (HTTP/3) under http/3 data frames over quic.
at a glance
- server: hypercorn (HTTP/3)
0.17.3 + aioquic 1.3.0 - runtime: python-3.12
- ecosystem: python
- concurrency model: event-loop
- parser: aioquic HTTP/3 H3Connection + Hypercorn ASGI delivery
- delivery granularity:
per-frame - chunk-limit helper: none exposed by the framework
- verdict: per-frame — the parser/dispatcher boundary delivers one event per protocol frame (h2 / h3 DATA frame, or ws data frame). cpu cost under paced mode b is measurable per frame.
- scaling exponent (mode a): 0.98 (wall time vs N, log-log slope across common cells)
- scaling exponent (mode b): 1.01
measurements
all cells run on a 1-vcpu docker container. cpu cost is derived from the target container’s cgroup v2 cpu.stat usage_usec delta around each cell.
| mode | N | wall (s) | server cpu % | µs / frame | basis | ok |
|---|---|---|---|---|---|---|
A-h3-bridge | 50,000 | 0.143 | 119.3 | 3.412 | server-cpu-cgroup | ✓ |
A-h3-bridge | 100,000 | 0.280 | 110.3 | 3.086 | server-cpu-cgroup | ✓ |
A-h3-bridge | 250,000 | 0.691 | 102.6 | 2.834 | server-cpu-cgroup | ✓ |
B-h3-paced-100us | 50,000 | 6.973 | 54.6 | 76.171 | server-cpu-cgroup | ✓ |
B-h3-paced-100us | 100,000 | 13.975 | 52.0 | 72.686 | server-cpu-cgroup | ✓ |
B-h3-paced-100us | 250,000 | 35.174 | 47.3 | 66.569 | server-cpu-cgroup | ✓ |
parser path — source citations
what this means
the parser/dispatcher path on this server delivers one event per protocol frame (a http/3 data frames over quic DATA frame or ws frame), so an attacker who sends a request body as N one-byte frames consumes roughly N × (mode-b µs/frame) of server cpu on a single core.
what to do today
- HTTP/3 quic stream / connection flow control is byte-level; it does not bound DATA frame count.
- consider a per-stream DATA-frame credit at the h3 dispatcher before delivering payload to the application.
reproducer
the full reproducer for this server is in the paper repo. the docker container pins hypercorn (HTTP/3) 0.17.3 + aioquic 1.3.0 and constrains the test container to a single cpu (--cpus=1). the prober script implements mode a (bridge-coalesced) and mode b (paced 100 µs) per the methodology section.
see the draft pdf for the full per-framework discussion.