Lands the transport/swarm orchestration layer (the iroh engine attaches
later, behind a flag). The seam is fully exercised today with the origin
HTTP path; with no swarm providers registered the behaviour is byte-for-byte
identical to before.
- swarm/mod.rs: BlobProvider trait + fetch_content_addressed() — tries each
provider in order, VERIFIES peer-sourced bytes against the content digest
before accepting (untrusted seeds can't inject tampered bytes), falls back
to the origin closure if none serve. Returns Swarm|Origin.
- Cargo: iroh-swarm feature (off by default; heavy QUIC dep tree attaches
here). providers() is empty until enabled → every fetch hits origin.
- update.rs: components with a BLAKE3 digest route through the seam, using
the existing resumable HTTP downloader as the origin fallback; a swarm hit
is re-checked against the mandatory SHA-256 manifest gate (re-fetch from
origin on any disagreement). Components without blake3 take the original
path untouched.
44/44 swarm/update/content_hash/blobs tests pass (incl. swarm hit/miss,
tampered-bytes-rejected→origin, fall-through ordering).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2523c9e3dd