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Vladimir Oltean fa43aa2fb5 net: dsa: report rx_bytes unadjusted for ETH_HLEN 
[ Upstream commit a8eff03545 ]

We collect the software statistics counters for RX bytes (reported to
/proc/net/dev and to ethtool -S $dev | grep 'rx_bytes: ") at a time when
skb->len has already been adjusted by the eth_type_trans() ->
skb_pull_inline(skb, ETH_HLEN) call to exclude the L2 header.

This means that when connecting 2 DSA interfaces back to back and
sending 1 packet with length 100, the sending interface will report
tx_bytes as incrementing by 100, and the receiving interface will report
rx_bytes as incrementing by 86.

Since accounting for that in scripts is quirky and is something that
would be DSA-specific behavior (requiring users to know that they are
running on a DSA interface in the first place), the proposal is that we
treat it as a bug and fix it.

This design bug has always existed in DSA, according to my analysis:
commit 91da11f870 ("net: Distributed Switch Architecture protocol
support") also updates skb->dev->stats.rx_bytes += skb->len after the
eth_type_trans() call. Technically, prior to Florian's commit
a86d8becc3 ("net: dsa: Factor bottom tag receive functions"), each and
every vendor-specific tagging protocol driver open-coded the same bug,
until the buggy code was consolidated into something resembling what can
be seen now. So each and every driver should have its own Fixes: tag,
because of their different histories until the convergence point.
I'm not going to do that, for the sake of simplicity, but just blame the
oldest appearance of buggy code.

There are 2 ways to fix the problem. One is the obvious way, and the
other is how I ended up doing it. Obvious would have been to move
dev_sw_netstats_rx_add() one line above eth_type_trans(), and below
skb_push(skb, ETH_HLEN). But DSA processing is not as simple as that.
We count the bytes after removing everything DSA-related from the
packet, to emulate what the packet's length was, on the wire, when the
user port received it.

When eth_type_trans() executes, dsa_untag_bridge_pvid() has not run yet,
so in case the switch driver requests this behavior - commit
412a1526d0 ("net: dsa: untag the bridge pvid from rx skbs") has the
details - the obvious variant of the fix wouldn't have worked, because
the positioning there would have also counted the not-yet-stripped VLAN
header length, something which is absent from the packet as seen on the
wire (there it may be untagged, whereas software will see it as
PVID-tagged).

Fixes: f613ed665b ("net: dsa: Add support for 64-bit statistics")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2023-03-30 12:50:56 +02:00
arch arm64: dts: imx93: add missing #address-cells and #size-cells to i2c nodes 2023-03-30 12:50:51 +02:00
block block: count 'ios' and 'sectors' when io is done for bio-based device 2023-03-22 13:37:50 +01:00
certs certs: Fix build error when PKCS#11 URI contains semicolon 2023-01-31 17:53:01 +09:00
crypto crypto: rsa-pkcs1pad - Use akcipher_request_complete 2023-03-10 09:28:18 +01:00
Documentation docs: Correct missing "d_" prefix for dentry_operations member d_weak_revalidate 2023-03-22 13:37:42 +01:00
drivers drm/i915: Update vblank timestamping stuff on seamless M/N change 2023-03-30 12:50:56 +02:00
fs nfsd: don't replace page in rq_pages if it's a continuation of last page 2023-03-30 12:50:53 +02:00
include net: stmmac: Fix for mismatched host/device DMA address width 2023-03-30 12:50:54 +02:00
init Kbuild fixes for v6.2 (3rd) 2023-01-21 10:56:37 -08:00
io_uring io_uring/msg_ring: let target know allocated index 2023-03-22 13:38:08 +01:00
ipc Non-MM patches for 6.2-rc1. 2022-12-12 17:28:58 -08:00
kernel tracing/hwlat: Replace sched_setaffinity with set_cpus_allowed_ptr 2023-03-30 12:50:48 +02:00
lib cpuidle: lib/bug: Disable rcu_is_watching() during WARN/BUG 2023-03-10 09:29:06 +01:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm: teach mincore_hugetlb about pte markers 2023-03-22 13:38:07 +01:00
net net: dsa: report rx_bytes unadjusted for ETH_HLEN 2023-03-30 12:50:56 +02:00
rust rust: print: avoid evaluating arguments in pr_* macros in unsafe blocks 2023-01-16 00:54:35 +01:00
samples ftrace: Export ftrace_free_filter() to modules 2023-01-24 11:20:58 -05:00
scripts kconfig: Update config changed flag before calling callback 2023-03-22 13:37:55 +01:00
security ima: Align ima_file_mmap() parameters with mmap_file LSM hook 2023-03-10 09:29:36 +01:00
sound ASoC: qcom: q6prm: fix incorrect clk_root passed to ADSP 2023-03-22 13:38:08 +01:00
tools selftests: net: devlink_port_split.py: skip test if no suitable device available 2023-03-22 13:37:53 +01:00
usr usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt KVM: Register /dev/kvm as the _very_ last thing during initialization 2023-03-10 09:29:33 +01:00
.clang-format iommufd for 6.2 2022-12-14 09:15:43 -08:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore *.rpm 2022-12-30 17:22:14 +09:00
.mailmap 12 hotfixes, mostly against mm/. Five of these fixes are cc:stable. 2023-02-13 14:09:20 -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: update SCTP maintainers 2023-02-02 11:35:33 -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 audit: update the mailing list in MAINTAINERS 2023-02-25 11:13:29 +01:00
Makefile Linux 6.2.8 2023-03-22 13:38:11 +01:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -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 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.