scion-hev3

Happy Eyeballs v3 for SCION: a racing client library, CLI, and demo server that connect over native SCION and plain IPv6/IPv4 in parallel and use whichever wins. The companion IETF draft work that makes SCION endpoints discoverable through DNS lives in netsys-lab/draft-scion-svcb.

Built for the SCION testbed at the IETF 126 hackathon (ietf-scion-testbed).

Contents

• pkg/hev3/ — the racer: resolves a name (HTTPS/SVCB scion=/ scion-policy= SvcParams, A/AAAA, ipv4hint/ipv6hint), builds candidates, races SCION (QUIC/h3 via snet) against IP legs with HEv3-style staggering, live DNS merge and latency-adaptive staggering, returns the winning connection.
• cmd/hev3 — CLI: hev3 https://web.scion/ fetches over whichever transport wins and can dump the race timeline (--json, --rr-type https|svcb|both, -pfc for preferred-family count per interleave round, --scion-grace as an optional demo knob: hold IP legs while SCION looks up paths).
• cmd/hev3-server — demo target: serves h3/h2 on plain-IP listeners and native SCION (dispatcherless snet/squic) on a separate bind address.

The companion Internet-Drafts — The scion SVCB Service Parameter (the scion 65280 and scion-policy 65281 SvcParamKeys: wire formats, fail-open rules, test vectors) and SCION-Aware Happy Eyeballs (the client algorithm this library implements: asynchronous path expansion, three-family sorting, adaptive staggering, the optional Expansion Delay) — are maintained in netsys-lab/draft-scion-svcb.

Build & test

make build   # bin/hev3, bin/hev3-server
make test
make deb     # dist/scion-hev3_<version>_amd64.deb

The full DNS→race→fetch integration test needs a checkout of the testbed repo (zone files, demo CA, SCION-patched CoreDNS build script):

TESTBED_ROOT=/path/to/ietf-scion-testbed bash integration/devbox_test.sh

Notes

• SCION support relies on the lschulz/scion fork (snet/squic) and a forked miekg/dns (branch scion) with typed scion/scion-policy SvcParamKeys (see go.mod).
• The TLS material the demo server presents (and the CA the CLI trusts at /etc/hev3/ca.pem) is throwaway, committed-on-purpose testbed key material — never trust it outside a testbed.