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Currently, AF_XDP only supports a fixed frame-size memory scheme where each frame is referenced via an index (idx). A user passes the frame index to the kernel, and the kernel acts upon the data. Some NICs, however, do not have a fixed frame-size model, instead they have a model where a memory window is passed to the hardware and multiple frames are filled into that window (referred to as the "type-writer" model). By changing the descriptor format from the current frame index addressing scheme, AF_XDP can in the future be extended to support these kinds of NICs. In the index-based model, an idx refers to a frame of size frame_size. Addressing a frame in the UMEM is done by offseting the UMEM starting address by a global offset, idx * frame_size + offset. Communicating via the fill- and completion-rings are done by means of idx. In this commit, the idx is removed in favor of an address (addr), which is a relative address ranging over the UMEM. To convert an idx-based address to the new addr is simply: addr = idx * frame_size + offset. We also stop referring to the UMEM "frame" as a frame. Instead it is simply called a chunk. To transfer ownership of a chunk to the kernel, the addr of the chunk is passed in the fill-ring. Note, that the kernel will mask addr to make it chunk aligned, so there is no need for userspace to do that. E.g., for a chunk size of 2k, passing an addr of 2048, 2050 or 3000 to the fill-ring will refer to the same chunk. On the completion-ring, the addr will match that of the Tx descriptor, passed to the kernel. Changing the descriptor format to use chunks/addr will allow for future changes to move to a type-writer based model, where multiple frames can reside in one chunk. In this model passing one single chunk into the fill-ring, would potentially result in multiple Rx descriptors. This commit changes the uapi of AF_XDP sockets, and updates the documentation. Signed-off-by: Björn Töpel <bjorn.topel@intel.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
77 lines
1.7 KiB
C
77 lines
1.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
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/*
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* if_xdp: XDP socket user-space interface
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* Copyright(c) 2018 Intel Corporation.
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*
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* Author(s): Björn Töpel <bjorn.topel@intel.com>
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* Magnus Karlsson <magnus.karlsson@intel.com>
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*/
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#ifndef _LINUX_IF_XDP_H
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#define _LINUX_IF_XDP_H
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#include <linux/types.h>
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/* Options for the sxdp_flags field */
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#define XDP_SHARED_UMEM 1
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struct sockaddr_xdp {
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__u16 sxdp_family;
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__u16 sxdp_flags;
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__u32 sxdp_ifindex;
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__u32 sxdp_queue_id;
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__u32 sxdp_shared_umem_fd;
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};
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struct xdp_ring_offset {
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__u64 producer;
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__u64 consumer;
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__u64 desc;
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};
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struct xdp_mmap_offsets {
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struct xdp_ring_offset rx;
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struct xdp_ring_offset tx;
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struct xdp_ring_offset fr; /* Fill */
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struct xdp_ring_offset cr; /* Completion */
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};
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/* XDP socket options */
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#define XDP_MMAP_OFFSETS 1
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#define XDP_RX_RING 2
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#define XDP_TX_RING 3
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#define XDP_UMEM_REG 4
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#define XDP_UMEM_FILL_RING 5
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#define XDP_UMEM_COMPLETION_RING 6
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#define XDP_STATISTICS 7
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struct xdp_umem_reg {
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__u64 addr; /* Start of packet data area */
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__u64 len; /* Length of packet data area */
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__u32 chunk_size;
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__u32 headroom;
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};
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struct xdp_statistics {
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__u64 rx_dropped; /* Dropped for reasons other than invalid desc */
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__u64 rx_invalid_descs; /* Dropped due to invalid descriptor */
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__u64 tx_invalid_descs; /* Dropped due to invalid descriptor */
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};
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/* Pgoff for mmaping the rings */
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#define XDP_PGOFF_RX_RING 0
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#define XDP_PGOFF_TX_RING 0x80000000
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#define XDP_UMEM_PGOFF_FILL_RING 0x100000000
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#define XDP_UMEM_PGOFF_COMPLETION_RING 0x180000000
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/* Rx/Tx descriptor */
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struct xdp_desc {
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__u64 addr;
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__u32 len;
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__u32 options;
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};
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/* UMEM descriptor is __u64 */
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#endif /* _LINUX_IF_XDP_H */
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