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Alexei Starovoitov
5cc5924d83
Jesper Dangaard Brouer says: ==================== V4: - Fixup checkpatch.pl issues - Collected more ACKs V3: - Fix issue on virtio_net patch spotted by Jason Wang - Adjust name for variable in mlx5 patch - Collected more ACKs V2: - Fix bug in mlx5 for XDP_PASS case - Collected nitpicks and ACKs from mailing list V1: - Fix bug in dpaa2 XDP have evolved to support several frame sizes, but xdp_buff was not updated with this information. This have caused the side-effect that XDP frame data hard end is unknown. This have limited the BPF-helper bpf_xdp_adjust_tail to only shrink the packet. This patchset address this and add packet tail extend/grow. The purpose of the patchset is ALSO to reserve a memory area that can be used for storing extra information, specifically for extending XDP with multi-buffer support. One proposal is to use same layout as skb_shared_info, which is why this area is currently 320 bytes. When converting xdp_frame to SKB (veth and cpumap), the full tailroom area can now be used and SKB truesize is now correct. For most drivers this result in a much larger tailroom in SKB "head" data area. The network stack can now take advantage of this when doing SKB coalescing. Thus, a good driver test is to use xdp_redirect_cpu from samples/bpf/ and do some TCP stream testing. Use-cases for tail grow/extend: (1) IPsec / XFRM needs a tail extend[1][2]. (2) DNS-cache responses in XDP. (3) HAProxy ALOHA would need it to convert to XDP. (4) Add tail info e.g. timestamp and collect via tcpdump [1] http://vger.kernel.org/netconf2019_files/xfrm_xdp.pdf [2] http://vger.kernel.org/netconf2019.html Examples on howto access the tail area of an XDP packet is shown in the XDP-tutorial example[3]. [3] https://github.com/xdp-project/xdp-tutorial/blob/master/experiment01-tailgrow/ ==================== Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.