Add usrsctp component (sctplab/usrsctp + ESP-IDF lwIP integration) (IEC-545)

[vikramdattu]

Summary

Adds usrsctp — an ESP-IDF wrapper around upstream sctplab/usrsctp (0.9.5). Submodule pinned at 2e1ab10, with five build-time patches applied at configure time.

usrsctp is a portable userland implementation of SCTP (RFC 4960). It's the standard SCTP stack used by WebRTC data channels (SCTP-over-DTLS-over-UDP) and by other consumers that need SCTP on platforms without a kernel-level implementation. Pairs naturally with the libsrtp2 component (PR #753) for the WebRTC use case.

Why a new component

We've been carrying this as a downstream component on the AWS KVS WebRTC SDK port for ESP32, in production on ESP32-P4 for the camera/WebRTC workstream. Bringing it into idf-extra-components so any IDF project can add-dependency espressif/usrsctp.

Naming

Bare upstream project name, matching the idf-extra-components convention (cf. cbor, nghttp, freetype, zlib, etc., which all match the upstream project's primary name — even when the install artifact is called lib<name>.a).

Searchable tag synonyms in idf_component.yml: sctp, sctplab, esp_usrsctp, esp_sctp, libusrsctp, webrtc, data-channel, rfc4960.

Commits

1. feat(usrsctp): add component (sctplab/usrsctp + ESP-IDF lwIP integration) — wrapper sources, usrsctp/usrsctp as a submodule gitlink at 2e1ab10, root .gitmodules entry, five build-time patches in patches/.
2. ci: register usrsctp in CI manifests — .idf_build_apps.toml, upload-component components:, bug-report dropdown. Alphabetical.

Patches

Five local patches in patches/, applied via git apply --check-gated loop in CMakeLists.txt (idempotent — already-applied patches are skipped):

#	Patch	Status
0001	Added LWIP support	Upstream PR in flight: sctplab/usrsctp#743. Will be dropped once it lands + we re-pin the submodule.
0002	Fix overflow error / allocate for larger sin6 structure	Bug fix. Will offer upstream as a separate small PR.
0003	ESP_PLATFORM: add support for thread-safe netif API	ESP-IDF-specific. Stays as downstream patch.
0004	feat(esp): allocate usrsctp thread stacks from SPIRAM	ESP-IDF-specific (helps on memory-constrained C5 / C6). Stays.
0005	Fix non-LWIP / Linux-target buildability in 'Added LWIP support'	Buildability fix. Folds into 0001 when it goes upstream.

See patches/README.md for the ledger.

Layout

usrsctp/
├── CMakeLists.txt        # ESP-IDF component registration + patch-apply loop
├── Kconfig               # debug + thread-stack location + crypto knobs
├── idf_component.yml     # registry manifest (tags, examples, sbom)
├── sbom_usrsctp.yml      # SBOM for the wrapped upstream
├── patches/              # 5 patches + README ledger
├── examples/get_started/
├── test_apps/            # embedded smoke test (esp32 + esp32c3)
├── host_test/            # IDF Linux-target socket-lifecycle test
├── usrsctp_register.c    # empty TU so idf_component_register has a source
└── usrsctp/              # sctplab/usrsctp submodule @ 2e1ab10

Build / test verification (local)

• test_apps/ on esp32: ✅ builds clean
• test_apps/ on esp32c3: ✅ builds clean
• host_test/ on IDF Linux target: ✅ builds clean + binary runs (usrsctp host_test: PASS, exit 0)
• examples/get_started/ builds clean
• .github/consistency_check.py passes
• Downstream verification: this same wrapper (under the old name esp_usrsctp) drives the WebRTC data-channel transport for our ESP32-P4 KVS WebRTC port in production.

License

Apache-2.0 AND BSD-3-Clause — ESP-IDF port glue is Apache-2.0; the bundled usrsctp/ submodule remains under upstream's BSD-3-Clause.

Related

• libsrtp2 component (PR feat(libsrtp2): add component (libsrtp 2.8.0 + ESP-IDF mbedTLS port) (IEC-542) #753) — the SRTP/SRTCP packet-protection partner for the WebRTC SRTP path.
• sctplab/usrsctp#743 — upstream PR adding the LWIP backend; when it lands, our patch 0001 (and the buildability follow-up 0005) disappear.

Reviews welcome — happy to split the patch series further, rename the option knobs, or rework anything that doesn't fit.

[vikramdattu]

Heads-up — moving this to espressif/esp-protocols instead of idf-extra-components, on the same migration track as the libsrtp PR (#753 → espressif/esp-protocols#1060).

New PR: espressif/esp-protocols#1063 (Draft — sits behind #1060 + #1061 on the migration train, will flip to ready-for-review once either lands and we apply consistent review feedback).

Component name and patch set carry over unchanged; conventions adapted to esp-protocols (.cz.yaml, paths under components/usrsctp/, .build-test-rules.yml rooted at the repo root, component-local .github/workflows/ dropped — replaced by the top-level usrsctp__build.yml matching the lws_build.yml pattern).

Closing this once the esp-protocols PR lands.

cc @euripedesrocha