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Cosmin Ratiu 25e4700489 xfrm_output: Force software GSO only in tunnel mode 
[ Upstream commit 0aae2867aa ]

The cited commit fixed a software GSO bug with VXLAN + IPSec in tunnel
mode. Unfortunately, it is slightly broader than necessary, as it also
severely affects performance for Geneve + IPSec transport mode over a
device capable of both HW GSO and IPSec crypto offload. In this case,
xfrm_output unnecessarily triggers software GSO instead of letting the
HW do it. In simple iperf3 tests over Geneve + IPSec transport mode over
a back-2-back pair of NICs with MTU 1500, the performance was observed
to be up to 6x worse when doing software GSO compared to leaving it to
the hardware.

This commit makes xfrm_output only trigger software GSO in crypto
offload cases for already encapsulated packets in tunnel mode, as not
doing so would then cause the inner tunnel skb->inner_networking_header
to be overwritten and break software GSO for that packet later if the
device turns out to not be capable of HW GSO.

Taking a closer look at the conditions for the original bug, to better
understand the reasons for this change:
- vxlan_build_skb -> iptunnel_handle_offloads sets inner_protocol and
  inner network header.
- then, udp_tunnel_xmit_skb -> ip_tunnel_xmit adds outer transport and
  network headers.
- later in the xmit path, xfrm_output -> xfrm_outer_mode_output ->
  xfrm4_prepare_output -> xfrm4_tunnel_encap_add overwrites the inner
  network header with the one set in ip_tunnel_xmit before adding the
  second outer header.
- __dev_queue_xmit -> validate_xmit_skb checks whether GSO segmentation
  needs to happen based on dev features. In the original bug, the hw
  couldn't segment the packets, so skb_gso_segment was invoked.
- deep in the .gso_segment callback machinery, __skb_udp_tunnel_segment
  tries to use the wrong inner network header, expecting the one set in
  iptunnel_handle_offloads but getting the one set by xfrm instead.
- a bit later, ipv6_gso_segment accesses the wrong memory based on that
  wrong inner network header.

With the new change, the original bug (or similar ones) cannot happen
again, as xfrm will now trigger software GSO before applying a tunnel.
This concern doesn't exist in packet offload mode, when the HW adds
encapsulation headers. For the non-offloaded packets (crypto in SW),
software GSO is still done unconditionally in the else branch.

Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
Reviewed-by: Yael Chemla <ychemla@nvidia.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Fixes: a204aef9fd ("xfrm: call xfrm_output_gso when inner_protocol is set in xfrm_output")
Signed-off-by: Cosmin Ratiu <cratiu@nvidia.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2025-03-28 22:03:25 +01:00
arch arm64: dts: rockchip: remove supports-cqe from rk3588 tiger 2025-03-28 22:03:25 +01:00
block block: fix 'kmem_cache of name 'bio-108' already exists' 2025-03-22 12:54:21 -07:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: api - Fix boot-up self-test race 2025-02-08 09:57:28 +01:00
Documentation rust: remove leftover mentions of the alloc crate 2025-03-22 12:54:23 -07:00
drivers firmware: imx-scu: fix OF node leak in .probe() 2025-03-28 22:03:24 +01:00
fs fs/netfs/read_collect: add to next->prev_donated 2025-03-22 12:54:28 -07:00
include Bluetooth: L2CAP: Fix corrupted list in hci_chan_del 2025-03-22 12:54:28 -07:00
init rust: Disallow BTF generation with Rust + LTO 2025-03-22 12:54:23 -07:00
io_uring io-wq: backoff when retrying worker creation 2025-03-22 12:54:19 -07:00
ipc ipc: fix memleak if msg_init_ns failed in create_ipc_ns 2024-12-05 14:03:02 +01:00
kernel sched_ext: Validate prev_cpu in scx_bpf_select_cpu_dfl() 2025-03-22 12:54:25 -07:00
lib rcuref: Plug slowpath race in rcuref_put() 2025-03-07 18:25:43 +01:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm mm/hugetlb: wait for hugetlb folios to be freed 2025-03-22 12:54:28 -07:00
net xfrm_output: Force software GSO only in tunnel mode 2025-03-28 22:03:25 +01:00
rust rust: init: add missing newline to pr_info! calls 2025-03-22 12:54:26 -07:00
samples rust: treewide: switch to the kernel Vec type 2025-03-13 13:01:46 +01:00
scripts scripts: generate_rust_analyzer: add uapi crate 2025-03-22 12:54:27 -07:00
security ima: Reset IMA_NONACTION_RULE_FLAGS after post_setattr 2025-03-07 18:25:44 +01:00
sound ASoC: codecs: wm0010: Fix error handling path in wm0010_spi_probe() 2025-03-22 12:54:26 -07:00
tools tools/sched_ext: Add helper to check task migration state 2025-03-22 12:54:28 -07:00
usr kbuild: hdrcheck: fix cross build with clang 2025-03-13 13:02:18 +01:00
virt KVM: x86: switch hugepage recovery thread to vhost_task 2024-12-05 14:02:43 +01:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.clippy.toml rust: enable Clippy's check-private-items 2025-03-13 13:01:42 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore rust: introduce .clippy.toml 2025-03-13 13:01:42 +01:00
.mailmap mailmap: add entry for Thorsten Blum 2024-11-07 14:14:59 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Remove self from DSA entry 2024-11-03 12:52:38 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MAINTAINERS: add entry for the Rust alloc module 2025-03-13 13:01:47 +01:00
Makefile Linux 6.12.20 2025-03-22 12:54:28 -07:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

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.