mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2026-09-22 09:34:56 +02:00
Jakub Sitnicki
89d912e494
Add a dynptr type, similar to skb dynptr, but for the skb metadata access. The dynptr provides an alternative to __sk_buff->data_meta for accessing the custom metadata area allocated using the bpf_xdp_adjust_meta() helper. More importantly, it abstracts away the fact where the storage for the custom metadata lives, which opens up the way to persist the metadata by relocating it as the skb travels through the network stack layers. Writes to skb metadata invalidate any existing skb payload and metadata slices. While this is more restrictive that needed at the moment, it leaves the door open to reallocating the metadata on writes, and should be only a minor inconvenience to the users. Only the program types which can access __sk_buff->data_meta today are allowed to create a dynptr for skb metadata at the moment. We need to modify the network stack to persist the metadata across layers before opening up access to other BPF hooks. Once more BPF hooks gain access to skb_meta dynptr, we will also need to add a read-only variant of the helper similar to bpf_dynptr_from_skb_rdonly. skb_meta dynptr ops are stubbed out and implemented by subsequent changes. Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com> Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org> Reviewed-by: Jesse Brandeburg <jbrandeburg@cloudflare.com> Link: https://patch.msgid.link/20250814-skb-metadata-thru-dynptr-v7-1-8a39e636e0fb@cloudflare.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.