doca-eth

# DOCA Ethernet ## Examples - **"My RX queue is up but no packets arrive."** — RX and TX are two Core contexts; one `doca_ctx_start()` does not cover both. - **"Send-task returns AGAIN at line rate."** — size burst against the `_cap_*` queries before changing queue type. ## Instructions Follow Loading order below. Open the tasks companion for configure / build / run. Open the capabilities companion for the RX-type taxonomy and send surface. Do not open every companion file. **Where to start:** This skill assumes DOCA is already installed and the user is doing **hands-on packet-queue work** on a host or BlueField with DOCA. Open the tasks companion if the user wants to *do* something (configure / build / modify / run / test / debug); open the capabilities companion when the question is *what can a DOCA Ethernet queue express* on this version. If the user has not installed DOCA yet, route to `doca-setup/SKILL.md` first. **RX and TX are independent Core contexts.** A `doca_eth_rxq` and a `doca_eth_txq` each get their own `doca_ctx_create` / `_start` / `_stop` / `_destroy`; one `doca_ctx_start()` does **not** start both sides. Do not walk a single lifecycle for "the queue pair". If the user is asking *"how do I get packets to land on my RX queue at all"*, the answer lives in `doca-flow/SKILL.md` — DOCA Ethernet is the *queue* surface; DOCA Flow is the *steering* surface, and they are independent libraries. ## Example questions this skill answers well The CLASSES of DOCA Ethernet questions this skill is built to answer, each with one worked example. The agent should treat the *class* as the load-bearing piece — the worked example is a single instance. - **"How do I bring up an RX and TX queue on a representor or physical port?"** — worked example: *"set up a `doca_eth_rxq` plus a `doca_eth_txq` on a single BlueField representor for first-run testing"*. Answered by two independent Core contexts (each with its own start) in ## configure + ## Capabilities and modes RX / TX object table. - **"Which RX type fits my data shape — regular, cyclic, or managed-recv?"** — worked example: *"line-rate ingress with fixed-size frames into a pre-allocated buffer ring"*. Answered by the RX-type taxonomy in ## Capabilities and modes + the capability-query rule (`doca_eth_rxq_cap_is_type_supported` against a `doca_devinfo`) in ## configure. - **"How do I send a packet from user code through `doca_eth_txq`?"** — worked example: *"allocate a packet `doca_buf`, attach the payload, submit one send-task, wait for the completion event"*. Answered by the TX submission shape in ## Capabilities and modes + the property-set workflow in ## modify. - **"My queue is up but no packets arrive — why?"** — worked example: *"`doca_eth_rxq` started cleanly but the recv callback never fires"*. Answered by the steering-dependency rule in ## Safety policy + the env-prep checklist in ## configure step 1, which routes the steering side to `doca-flow/SKILL.md` and the promiscuous-mode side to `doca-setup/SKILL.md`. - **"Is this Ethernet capability available on my device + my installed DOCA?"** — worked example: *"does this device advertise L3 checksum offload"*. Answered by the capability-query rule (`doca_eth_txq_cap_is_l3_chksum_offload_supported` against a `doca_devinfo`) in ## Capabilities and modes + the version-and-device overlay in ## Version compatibility. - **"What does this `DOCA_ERROR_*` from an Ethernet call mean and which layer caused it?"** — worked example: *"`DOCA_ERROR_AGAIN` on `doca_task_submit` for an `eth_txq` send-task at high rate"*. Answered by the Ethernet overlay on the cross-library taxonomy in ## Error taxonomy + the layered ladder in ## debug that escalates to `doca-debug/SKILL.md`. **Picking the root-cause layer when several could explain a symptom.** Walk the layers bottom-up (install → version → build → link → runtime → program → driver) with the read-only check each layer names in `TASKS.md` `## debug`. The lowest layer whose check fails is the root cause: fix it, change one variable at a time, and re-run the same check before moving up. For a silent RX queue, rule out the three runtime preconditions (device access, port up, traffic steered to the queue) before any program or driver cause. ## Audience This skill serves **external developers building applications that consume the DOCA Ethernet library** — i.e., users whose code calls `doca_eth_rxq_*` / `doca_eth_txq_*` (directly in C/C++, or through FFI/bindings from another language) to do line-rate packet I/O on physical ports, representors, or SFs of a BlueField or ConnectX device. It is *not* for NVIDIA developers contributing to DOCA Ethernet itself. **Language scope.** DOCA Ethernet ships as a C library with `pkg-config` module name `doca-eth`. The shipped samples are written in C. C and C++ consumers are the canonical case; the worked examples in the tasks companion assume that path. Other-language consumers (Rust, Go, Python, …) consume the same `*.so` through FFI or language-specific bindings; the skill's contribution in that case is to keep the queue-object split, lifecycle, capability-discovery, permission, RX-type taxonomy, and error-taxonomy guidance language-neutral, and to route the agent to the public C ABI as the authoritative surface that any wrapper will eventually call. ## When to load this skill Load this skill when the user is doing hands-on DOCA Ethernet work, in any language. Concretely: - Initializing a `doca_eth_rxq` on a `doca_dev` opened against a physical port, a representor, or an SF — choosing among the regular / cyclic / managed-recv RX types based on data shape before `doca_ctx_start()`. - Initializing a `doca_eth_txq` on the same or a different `doca_dev` and posting send-tasks against packet `doca_buf`s payload buffers. - Reading or setting Ethernet queue properties via `doca_eth_rxq_set_*` / `doca_eth_txq_set_*` and querying device capability via `doca_eth_rxq_cap_*` / `doca_eth_txq_cap_*` (max burst size, RX-type support, max scatter-gather length, checksum-offload presence). - Confirming the port is up and that traffic is actually steered to the chosen RX queue — either via DOCA Flow rules (the canonical path) or via kernel-side promiscuous mode (the expedient first-run path). - Wiring an Ethernet queue to a higher-level data plane: GPU packet processing via DOCA GPUNetIO, custom user-space forwarding agents, or telemetry mirrors that snap a copy of every packet. - Debugging a `DOCA_ERROR_*` returned from an Ethernet call (lifecycle vs. permission vs. capability vs. send-queue-full vs. driver-below) and the per-queue progress engine events. - Designing or extending non-C bindings (Rust, Go, Python, …) that wrap the DOCA Ethernet C ABI — for the lifecycle, queue split, RX-type, capability, and permission rules the wrapper must honor. Do **not** load this skill for general DOCA orientation, install of DOCA itself, flow-rule programming (use `doca-flow/SKILL.md`), host ↔ DPU control messaging (use `doca-comch/SKILL.md`), or RDMA data movement (use `doca-rdma/SKILL.md`). For DOCA documentation orientation, use `doca-public-knowledge-map/SKILL.md`. ## What this skill provides This is a **thin loader**. The body keeps only the orientation needed to pick the right next file. The substantive Ethernet- specific material lives in two companion files: - the capabilities companion — what a DOCA Ethernet queue can express on this version: the RX / TX object split, the RX-type taxonomy (regular / cyclic / managed-recv), the send-task / frame submission surface, the capability-query surface (`doca_eth_rxq_cap_*` / `doca_eth_txq_cap_*`), the Ethernet error taxonomy (mapped onto the cross-library `DOCA_ERROR_*` set), the observability surface (per-queue progress engine events, capability snapshots), and the safety policy that gates the steering / permission / port-state preconditions. - the tasks companion — step-by-step workflows for the six in-scope Ethernet verbs: `configure`, `build`, `modify`, `run`, `test`, `debug`. Plus a `Deferred task verbs` block that points out-of-scope questions at the right next skill, and a `Command appendix` of the recurring commands the agent reaches for. The skill assumes a host or BlueField where DOCA is already installed at the standard location and the user has the privileges their public install profile expects (typically sudo or `mlnx`-group membership to open a `doca_dev` against a port). It does not cover installing DOCA — that path goes through `doca-setup/SKILL.md`. ## What this skill deliberately does not ship This skill is **agent guidance**, not a samples or templates bundle. To keep the boundary clean, it deliberately does not contain — and pull requests should not add: - **Pre-written DOCA Ethernet application source code, in any language.** The verified Ethernet source code is the shipped C samples at `/opt/mellanox/doca/samples/doca_eth/<name>/`. The agent's job is to route the user to those files and prescribe a minimum-diff modification on them via the universal modify-a-sample workflow in `doca-programming-guide/SKILL.md`, layered with the Ethernet-specific overrides in ## modify. - **Standalone build manifests** (`meson.build`, `CMakeLists.txt`, `Cargo.toml`, …) parked inside the skill. The agent constructs the build manifest *in the user's project directory* against the user's installed DOCA, where `pkg-config --modversion doca-eth` is the source of truth. - **A `samples/`, `bindings/`, or `reference/` subtree** of any kind. A mock or incomplete artifact in this skill's tree, even one labeled "reference", is misleading: users will read it as buildable. ## Loading order 1. Read this skill first to confirm the user's question is in scope. 2. **For the Ethernet capability matrix, RX-type taxonomy, send surface, capability-query rules, error taxonomy, observability, and safety policy, see the capabilities companion.** 3. **For step-by-step workflows — configure, build, modify, run, test, debug — see the tasks companion.** Both companion files cross-link to each other, `doca-version/SKILL.md` for the canonical version-handling rules, `doca-flow/SKILL.md` for the steering side that the RX queue depends on, and `doca-public-knowledge-map/SKILL.md` whenever the right answer is "look it up in the public docs or the installed package layout" rather than "Ethernet-specific guidance". ## Related skills - `doca-public-knowledge-map/SKILL.md` — the routing table for every public DOCA documentation source and the on-disk layout of an installed DOCA package. The Ethernet URL slug is `DOCA-Ethernet`. - `doca-setup/SKILL.md` — env preparation, install verification, port-state checks (`devlink dev show`, `ip link`), permission and group-membership requirements for opening a `doca_dev`. This skill assumes its preconditions are satisfied. - `doca-version/SKILL.md` — canonical DOCA version-handling rules. This skill's `## Version compatibility` cross-links the four-way match rule and adds only the Ethernet-specific overlay (RX-type availability windows, checksum-offload device-conditional support). - `doca-structured-tools-contract/SKILL.md` — the bundle's structured-tools precedence rule (detect / prefer / fall back / report). The Command appendix in the tasks companion honors this contract. - `doca-programming-guide/SKILL.md` — general DOCA programming patterns shared by every library: the canonical `pkg-config` + meson build pattern, the universal modify-a-shipped-sample first-app workflow, the universal lifecycle, the cross-library `DOCA_ERROR_*` taxonomy, and the program-side debug order. This skill layers Ethernet specifics on top. - `doca-flow/SKILL.md` — the steering surface that decides which packets land on which `doca_eth_rxq`. DOCA Ethernet does *not* program steering itself; an empty RX queue almost always means a missing or wrong Flow rule, not an Ethernet bug. - `doca-debug/SKILL.md` — the cross-cutting debug ladder (install / version / build / link / runtime / program / driver). Ethernet-specific debug (RX-type mismatches, send-queue-full retries, steering-empty-queue symptoms) overlays on top of that ladder.