str0m transport patch

Source: crates.io str0m 0.23.1, upstream revision 120401c9affd97fd4246d9e7faf0ad4ca099c1bc from algesten/str0m. This copy uses the MIT option; LICENSE-MIT.txt preserves the upstream notice. Cargo.toml.orig is the published original manifest; transport.patch records changes to published source and the normalized manifest.

The firmware selects this copy through its workspace Cargo patch. It adds RtcConfig::set_sctp_receive_limits and reexports SctpReceiveLimits from channel. The policy configures ordinary client/server associations and SNAP, and the same message size is advertised in SDP. Direct SNAP callers construct matching SctpInitData::with_receive_limits before generating their INIT token. The default behavior is unchanged when no policy is supplied.

SCTP transmit queues retain owned Bytes until DTLS accepts them, including backpressure retries. This transfers packet ownership without a payload copy; DTLS still borrows the packet for one synchronous call. Packet order, retransmission and authentication behavior are unchanged. A direct bytes dependency names the buffer type already used by sctp-proto.

The patch also keeps the upstream newer lint compatible with the supported Rust 1.88 host compiler and makes the default SCTP constructor test-only.

Source and tests

Production source, upstream library and integration tests, their original PCAP fixtures, protocol documentation, manifests, changelog and license are preserved. The vendor .gitignore explicitly re-includes the published PCAP inputs and BWE diagram. Cargo registry metadata, the logo, README template, upstream CI, editor and lint configuration, examples and example certificate-generation scaffolding are omitted. The normalized manifest omits the removed example targets.

The local Cargo.lock pins the standalone host test graph; production uses the firmware workspace lockfile. No firmware build depends on an archive, experiment, registry-source modification or generated source copy.

From the repository root, run the full library suite with the local protocol and provider patches:

cargo +1.88.0 test --manifest-path firmware/vendor/str0m/Cargo.toml \
  --locked --no-default-features --features rust-crypto --lib \
  --config 'patch.crates-io.sctp-proto.path="firmware/vendor/sctp-proto"' \
  --config 'patch.crates-io.str0m-rust-crypto.path="firmware/vendor/str0m-rust-crypto"' \
  --target-dir artifacts/vendor-tests

The upstream host tests generate certificates and therefore enable the provider's generate-cert feature and its AWS-LC dependency. That feature is disabled in the firmware graph. Keep these vendor crates excluded from workspace membership; --all-features would select unrelated platform crypto providers.

make check-transport-patches also runs the retained contiguous, keyframes and loss integration targets with rust-crypto,_internal_test_exports. Their shared fixture loader covers all seven PCAP inputs, so CI checks that the versioned copy contains those assets.

When upgrading, compare upstream first and remove equivalent local changes. Run this suite, the sctp-proto suite, firmware checks, and live audio, spectrum, command and reconnection validation. Receive budgets are defined in the sctp-proto patch.