fix(transport/ecn): start after handshake and path validation

[mxinden]

Fixes #2490.

Only start ECN marking and thus ECN-Path validation when:

• Connection handshake is confirmed.
• AND, for any secondary path, path is validated (e.g. via PATH_RESPONSE).

---

Draft for now. Opening up early to prevent duplicate work.

[github-actions]

Failed Interop Tests

QUIC Interop Runner, client vs. server, differences relative to 182afed.

neqo-latest as client

• neqo-latest vs. go-x-net: BP BA
• neqo-latest vs. haproxy: ⚠️DC C20 M 3 B U L1 L2 C1 C2 BP BA
• neqo-latest vs. kwik: L1 C1
• neqo-latest vs. lsquic: ⚠️H E L1 C1
• neqo-latest vs. msquic: R Z A L1 C1
• neqo-latest vs. mvfst: A L1 C1 ⚠️BA
• neqo-latest vs. neqo: A
• neqo-latest vs. neqo-latest: A
• neqo-latest vs. nginx: ⚠️H DC LR C20 M S R Z 3 B U A L1 L2 C1 C2 6 BP BA
• neqo-latest vs. ngtcp2: ⚠️E CM
• neqo-latest vs. picoquic: ⚠️E A ⚠️L1
• neqo-latest vs. quic-go: A
• neqo-latest vs. quiche: 🚀L1 C1 BP BA
• neqo-latest vs. s2n-quic: ⚠️E BA CM
• neqo-latest vs. tquic: S BP BA
• neqo-latest vs. xquic: A

neqo-latest as server

• aioquic vs. neqo-latest: CM
• go-x-net vs. neqo-latest: CM
• kwik vs. neqo-latest: 🚀C1 BP BA CM
• lsquic vs. neqo-latest: 🚀L1 CM
• msquic vs. neqo-latest: Z U CM
• mvfst vs. neqo-latest: Z A L1 C1 CM
• neqo vs. neqo-latest: A
• openssl vs. neqo-latest: LR M A CM
• quic-go vs. neqo-latest: CM
• quiche vs. neqo-latest: CM
• quinn vs. neqo-latest: ⚠️L1 C1 V2 CM
• s2n-quic vs. neqo-latest: ⚠️E CM
• tquic vs. neqo-latest: CM
• xquic vs. neqo-latest: M CM

All results

Succeeded Interop Tests

QUIC Interop Runner, client vs. server

neqo-latest as client

• neqo-latest vs. aioquic: H DC LR C20 M S R Z 3 B U A L1 L2 C1 C2 6 V2 BP BA
• neqo-latest vs. go-x-net: H DC LR M B U A L2 C2 6
• neqo-latest vs. haproxy: H ⚠️DC LR ⚠️C20 M S R Z ⚠️3 B U A ⚠️L1 L2 C1 C2 6 V2
• neqo-latest vs. kwik: H DC LR C20 M S R Z 3 B U A L2 C2 6 V2 BP BA
• neqo-latest vs. linuxquic: H DC LR C20 M S R Z 3 B U E A 🚀L1 L2 C1 C2 6 V2 BP BA CM
• neqo-latest vs. lsquic: ⚠️H DC LR C20 M S R Z 3 B U ⚠️E A L2 C2 6 V2 BP BA
• neqo-latest vs. msquic: H DC LR C20 M S B U L2 C2 6 V2 BP BA
• neqo-latest vs. mvfst: H DC LR M R Z 3 B U L2 C2 6 BP ⚠️BA
• neqo-latest vs. neqo: H DC LR C20 M S R Z 3 B U E L1 L2 C1 C2 6 V2 BP BA CM
• neqo-latest vs. neqo-latest: H DC LR C20 M S R Z 3 B U E L1 L2 C1 C2 6 V2 BP BA CM
• neqo-latest vs. ngtcp2: H DC LR C20 M S R Z 3 B U ⚠️E A L1 L2 C1 C2 6 V2 BP BA
• neqo-latest vs. picoquic: H DC LR C20 M S R Z 3 B U ⚠️E L1 L2 C1 C2 6 V2 BP BA
• neqo-latest vs. quic-go: H DC LR C20 M S R Z 3 B U L1 L2 C1 C2 6 BP BA
• neqo-latest vs. quiche: H DC LR C20 M S R Z 3 B U A 🚀L1 L2 🚀C1 C2 6
• neqo-latest vs. quinn: H DC LR C20 M S R Z 3 B U E A L1 L2 C1 C2 6 BP BA
• neqo-latest vs. s2n-quic: H DC LR C20 M S R 3 B U ⚠️E A L1 L2 C1 C2 6 BP
• neqo-latest vs. tquic: H DC LR C20 M R Z 3 B U A L1 L2 C1 C2 6
• neqo-latest vs. xquic: H DC LR C20 M R Z 3 B U L1 L2 C1 C2 6 BP BA

neqo-latest as server

• aioquic vs. neqo-latest: H DC LR C20 M S R Z 3 B A L1 L2 C1 C2 6 V2 BP BA
• chrome vs. neqo-latest: 3
• go-x-net vs. neqo-latest: H DC LR M B U A L2 C2 6 BP BA
• kwik vs. neqo-latest: H DC LR C20 M S R Z 3 B U A L1 L2 🚀C1 C2 6 V2
• linuxquic vs. neqo-latest: H DC LR C20 M S R Z 3 B U E A L1 L2 C1 C2 6 V2 BP BA CM
• lsquic vs. neqo-latest: H DC LR M S R 3 B E A 🚀L1 L2 C1 C2 6 V2 BP BA
• msquic vs. neqo-latest: H DC LR C20 M S R B A L1 L2 C1 C2 6 V2 BP BA
• mvfst vs. neqo-latest: H DC LR M 3 B L2 C2 6 BP BA
• neqo vs. neqo-latest: H DC LR C20 M S R Z 3 B U E L1 L2 C1 C2 6 V2 BP BA CM
• ngtcp2 vs. neqo-latest: H DC LR C20 M S R Z 3 B U E A L1 L2 C1 C2 6 V2 BP BA CM
• openssl vs. neqo-latest: H DC C20 S R 3 B L2 C2 6 BP BA
• picoquic vs. neqo-latest: H DC LR C20 M S R Z 3 B U E A L1 L2 C1 C2 6 V2 BP BA CM
• quic-go vs. neqo-latest: H DC LR C20 M S R Z 3 B U A L1 L2 C1 C2 6 BP BA
• quiche vs. neqo-latest: H DC LR M S R Z 3 B A L1 L2 C1 C2 6 BP BA
• quinn vs. neqo-latest: H DC LR C20 M S R Z 3 B U E A ⚠️L1 L2 ⚠️C1 C2 6 BP BA
• s2n-quic vs. neqo-latest: H DC LR M S R 3 B ⚠️E A L1 L2 C1 C2 6 BP BA
• tquic vs. neqo-latest: H DC LR M S R Z 3 B A L1 L2 C1 C2 6 BP BA
• xquic vs. neqo-latest: H DC LR C20 S R Z 3 B U A L1 L2 C1 C2 6 BP BA

Unsupported Interop Tests

QUIC Interop Runner, client vs. server

neqo-latest as client

• neqo-latest vs. aioquic: E CM
• neqo-latest vs. go-x-net: C20 S R Z 3 E L1 C1 V2 CM
• neqo-latest vs. haproxy: E CM
• neqo-latest vs. kwik: E CM
• neqo-latest vs. lsquic: CM
• neqo-latest vs. msquic: 3 E CM
• neqo-latest vs. mvfst: C20 S E V2 CM
• neqo-latest vs. nginx: E V2 CM
• neqo-latest vs. picoquic: CM
• neqo-latest vs. quic-go: E V2 CM
• neqo-latest vs. quiche: E V2 CM
• neqo-latest vs. quinn: V2 CM
• neqo-latest vs. s2n-quic: Z V2
• neqo-latest vs. tquic: E V2 CM
• neqo-latest vs. xquic: S E V2 CM

neqo-latest as server

• aioquic vs. neqo-latest: U E
• chrome vs. neqo-latest: H DC LR C20 M S R Z B U E A L1 L2 C1 C2 6 V2 BP BA CM
• go-x-net vs. neqo-latest: C20 S R Z 3 E L1 C1 V2
• kwik vs. neqo-latest: E
• lsquic vs. neqo-latest: C20 Z U
• msquic vs. neqo-latest: 3 E
• mvfst vs. neqo-latest: C20 S R U E V2
• openssl vs. neqo-latest: Z U E L1 C1 V2
• quic-go vs. neqo-latest: E V2
• quiche vs. neqo-latest: C20 U E V2
• s2n-quic vs. neqo-latest: C20 Z U V2
• tquic vs. neqo-latest: C20 U E V2
• xquic vs. neqo-latest: E V2