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Add kfunc, bpf_xdp_pull_data(), to support pulling data from xdp fragments. Similar to bpf_skb_pull_data(), bpf_xdp_pull_data() makes the first len bytes of data directly readable and writable in bpf programs. If the "len" argument is larger than the linear data size, data in fragments will be copied to the linear data area when there is enough room. Specifically, the kfunc will try to use the tailroom first. When the tailroom is not enough, metadata and data will be shifted down to make room for pulling data. A use case of the kfunc is to decapsulate headers residing in xdp fragments. It is possible for a NIC driver to place headers in xdp fragments. To keep using direct packet access for parsing and decapsulating headers, users can pull headers into the linear data area by calling bpf_xdp_pull_data() and then pop the header with bpf_xdp_adjust_head(). Signed-off-by: Amery Hung <ameryhung@gmail.com> Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org> Reviewed-by: Jakub Kicinski <kuba@kernel.org> Link: https://patch.msgid.link/20250922233356.3356453-4-ameryhung@gmail.com
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 reStructuredText 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.