io_uring: add buf-ring + multishot recv to IoUringImpl#44668
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This is a no-behavior-change preparation step for multishot recv. The ``CompletionCb`` callback type now takes a ``uint32_t flags`` argument that carries the raw ``cqe->flags`` value from the kernel. For multishot completions a follow-up change will inspect: * ``IORING_CQE_F_BUFFER`` — a buffer was selected from a buf-ring; the buffer ID is encoded in the upper bits. * ``IORING_CQE_F_MORE`` — the SQE will produce further completions. The worker callback ignores ``flags`` for now. Injected completions are defined to always carry ``flags == 0``. All ``forEveryCompletion`` callers (worker, impl tests) updated. ``IoUringSocket::on*`` virtual methods are intentionally unchanged in this commit; only ``onRead`` will need flags, in the multishot recv change. Signed-off-by: Adam Buran <a.buran28@gmail.com> Signed-off-by: Adam Buran <aburan28@gmail.com>
Adds the kernel-managed buffer ring lifecycle and the ``recv`` multishot opcode to ``IoUringImpl``. This is the plumbing layer for switching the io_uring socket read path off the per-read ``readv`` allocation; the worker change comes in a follow-up PR. New ``IoUring`` virtuals: * ``setupBufRing(group_id, count, buf_size)`` — register a buffer ring with the kernel. The buffers live in a single contiguous allocation owned by ``IoUringImpl``. Validates that ``count`` is a non-zero power of two and rejects double-setup. Falls back to ``IoUringResult::Failed`` on kernels that lack ``IORING_REGISTER_PBUF_RING`` (< 5.19). * ``prepareRecvMultishot(fd, group_id, user_data)`` — submits a recv with ``IOSQE_BUFFER_SELECT`` so the kernel pulls a buffer from the ring. The same SQE may produce multiple completions, signalled by ``IORING_CQE_F_MORE`` in ``cqe->flags``. * ``getBufferForBid(group_id, bid)`` — look up the storage backing a particular kernel-selected buffer; the consumer reads up to ``cqe->res`` bytes and then recycles. * ``recycleBuffer(group_id, bid)`` — return a consumed buffer to the ring so the kernel can reuse it. For now only one buf-ring is supported per ``IoUring`` instance. Test: * ``SetupBufRingValidatesInputs`` — exercises the rejection paths (bad count, bad buf_size, double-setup). * ``MultishotRecvDeliversBuffersAndStaysArmed`` — end-to-end with a real socketpair and a real ring: arm a multishot recv, write twice, verify both completions deliver buffers, the bid is in range, the data matches, and the SQE stays armed (F_MORE set on the first completion). Skips when the kernel lacks buf-ring support. Signed-off-by: Adam Buran <a.buran28@gmail.com> Signed-off-by: Adam Buran <aburan28@gmail.com>
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Signed-off-by: Adam Buran <aburan28@gmail.com>
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Commit Message:
io_uring: add buf-ring + multishot recv API to IoUringImpl
Plumbing layer for switching the io_uring socket read path off the per-read
readvallocation. Adds the kernel-managed buffer ring(
IORING_REGISTER_PBUF_RING) lifecycle andIORING_OP_RECVmultishot toIoUringImpl. The worker change that consumes this comes in a follow-up PR.New
IoUringvirtuals:setupBufRing(group_id, count, buf_size)— registers a buffer ring withthe kernel. Buffers live in a single contiguous allocation owned by
IoUringImpl. Validates thatcountis a non-zero power of two; rejectsdouble-setup. Returns
Failedon kernels < 5.19 (noIORING_REGISTER_PBUF_RING).prepareRecvMultishot(fd, group_id, user_data)— submits a recv withIOSQE_BUFFER_SELECT. The same SQE may produce multiple completions,signalled by
IORING_CQE_F_MOREincqe->flags.getBufferForBid(group_id, bid)— looks up the storage backing akernel-selected buffer.
recycleBuffer(group_id, bid)— returns a consumed buffer to the ring.Only one buf-ring per
IoUringinstance for now.Depends on #44667 (
CompletionCbflags-arg refactor — required soforEveryCompletioncan surfacecqe->flagsto the multishot consumer).Additional Description:
The full multishot read path touches the worker, the server-socket read state
machine, and the proto config. Landing the
IoUringImplAPI on its own givesreviewers a smaller, well-scoped surface to vet against the liburing/kernel
contract.
AI usage disclosure: Portions of the code and/or PR description were drafted
with the assistance of Claude (Anthropic). I reviewed and understand all
submitted code.
Risk Level: Low
(API-only addition. Nothing in this PR calls the new virtuals — the worker-
side caller arrives in #44669. No existing path changes.)
Testing:
SetupBufRingValidatesInputscovers rejection paths (badcount, bad
buf_size, double-setup).MultishotRecvDeliversBuffersAndStaysArmeduses a realIoUringImpl+ socketpair: arms a multishot recv, writes twice, verifiesboth completions deliver buffers, bids are in range, data matches, and
F_MOREstays set across recycles. Skips when the kernel lacks buf-ringsupport.
Docs Changes: N/A. New methods are documented inline in
envoy/common/io/io_uring.h.Release Notes: N/A (internal API additions; not yet exposed to extension
authors or operators — exposure happens in #44670).
Platform Specific Features:
io_uring is Linux-only. Buf-ring requires kernel 5.19+;
setupBufRingreturns
Failedon older kernels and callers are expected to fall back. Noplatform support change beyond the existing io_uring build gating.
Runtime guard: N/A. No call sites in this PR — the new API is dead code
until #44669 lands.