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Ido Schimmel 91b6dbced0 bridge: netfilter: Fix forwarding of fragmented packets
When netfilter defrag hooks are loaded (due to the presence of conntrack
rules, for example), fragmented packets entering the bridge will be
defragged by the bridge's pre-routing hook (br_nf_pre_routing() ->
ipv4_conntrack_defrag()).

Later on, in the bridge's post-routing hook, the defragged packet will
be fragmented again. If the size of the largest fragment is larger than
what the kernel has determined as the destination MTU (using
ip_skb_dst_mtu()), the defragged packet will be dropped.

Before commit ac6627a28d ("net: ipv4: Consolidate ipv4_mtu and
ip_dst_mtu_maybe_forward"), ip_skb_dst_mtu() would return dst_mtu() as
the destination MTU. Assuming the dst entry attached to the packet is
the bridge's fake rtable one, this would simply be the bridge's MTU (see
fake_mtu()).

However, after above mentioned commit, ip_skb_dst_mtu() ends up
returning the route's MTU stored in the dst entry's metrics. Ideally, in
case the dst entry is the bridge's fake rtable one, this should be the
bridge's MTU as the bridge takes care of updating this metric when its
MTU changes (see br_change_mtu()).

Unfortunately, the last operation is a no-op given the metrics attached
to the fake rtable entry are marked as read-only. Therefore,
ip_skb_dst_mtu() ends up returning 1500 (the initial MTU value) and
defragged packets are dropped during fragmentation when dealing with
large fragments and high MTU (e.g., 9k).

Fix by moving the fake rtable entry's metrics to be per-bridge (in a
similar fashion to the fake rtable entry itself) and marking them as
writable, thereby allowing MTU changes to be reflected.

Fixes: 62fa8a846d ("net: Implement read-only protection and COW'ing of metrics.")
Fixes: 33eb9873a2 ("bridge: initialize fake_rtable metrics")
Reported-by: Venkat Venkatsubra <venkat.x.venkatsubra@oracle.com>
Closes: https://lore.kernel.org/netdev/PH0PR10MB4504888284FF4CBA648197D0ACB82@PH0PR10MB4504.namprd10.prod.outlook.com/
Tested-by: Venkat Venkatsubra <venkat.x.venkatsubra@oracle.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Link: https://patch.msgid.link/20250515084848.727706-1-idosch@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2025-05-16 16:02:06 -07:00
arch Kbuild fixes for v6.15 2025-05-14 22:24:17 -07:00
block block-6.15-20250509 2025-05-09 10:34:50 -07:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: scompress - increment scomp_scratch_users when already allocated 2025-04-25 10:33:30 +08:00
Documentation Including fixes from Bluetooth and wireless. 2025-05-15 10:40:49 -07:00
drivers team: grab team lock during team_change_rx_flags 2025-05-16 15:47:48 -07:00
fs for-6.15-rc6-tag 2025-05-14 18:39:12 -07:00
include Including fixes from Bluetooth and wireless. 2025-05-15 10:40:49 -07:00
init init: remove unused CONFIG_CC_CAN_LINK_STATIC 2025-05-12 15:03:46 +09:00
io_uring io_uring/sqpoll: Increase task_work submission batch size 2025-05-09 07:56:53 -06:00
ipc treewide: const qualify ctl_tables where applicable 2025-01-28 13:48:37 +01:00
kernel Kbuild fixes for v6.15 2025-05-14 22:24:17 -07:00
lib hardening fixes for v6.15-rc3 2025-04-18 13:20:20 -07:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm vfs-6.15-rc7.fixes 2025-05-12 10:04:14 -07:00
net bridge: netfilter: Fix forwarding of fragmented packets 2025-05-16 16:02:06 -07:00
rust rust: clean Rust 1.88.0's clippy::uninlined_format_args lint 2025-05-07 00:11:47 +02:00
samples tracing: samples: Initialize trace_array_printk() with the correct function 2025-05-12 13:07:22 -04:00
scripts kbuild: fix typos "module.builtin" to "modules.builtin" 2025-05-12 15:04:52 +09:00
security Landlock fix for v6.15-rc4 2025-04-24 12:59:05 -07:00
sound ASoC: Fixes for v6.15 2025-05-01 10:22:20 +02:00
tools Including fixes from Bluetooth and wireless. 2025-05-15 10:40:49 -07:00
usr usr/include: openrisc: don't HDRTEST bpf_perf_event.h 2025-05-12 15:03:17 +09:00
virt ARM: 2025-04-08 13:47:55 -07:00
.clang-format clang-format: Update the ForEachMacros list for v6.15-rc1 2025-04-13 11:03:59 +02:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.cocciconfig
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: Retire Ralf Baechle 2024-11-12 15:48:59 +01:00
.gitattributes
.gitignore kbuild: Create intermediate vmlinux build with relocations preserved 2025-03-17 00:29:50 +09:00
.mailmap soc: fixes for 6.15, part 2 2025-05-14 09:11:05 -07:00
.rustfmt.toml
COPYING
CREDITS MAINTAINERS: update SLAB ALLOCATOR maintainers 2025-04-17 20:10:06 -07:00
Kbuild drm: ensure drm headers are self-contained and pass kernel-doc 2025-02-12 10:44:43 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS soc: fixes for 6.15, part 2 2025-05-14 09:11:05 -07:00
Makefile Revert "kbuild, rust: use -fremap-path-prefix to make paths relative" 2025-05-12 15:04:13 +09:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

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.