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Yingnan Zhang 69bee27edb ipvs: fix MTU check for GSO packets in tunnel mode 
[ Upstream commit 67bf42cae4 ]

Currently, IPVS skips MTU checks for GSO packets by excluding them with
the !skb_is_gso(skb) condition. This creates problems when IPVS tunnel
mode encapsulates GSO packets with IPIP headers.

The issue manifests in two ways:

1. MTU violation after encapsulation:
   When a GSO packet passes through IPVS tunnel mode, the original MTU
   check is bypassed. After adding the IPIP tunnel header, the packet
   size may exceed the outgoing interface MTU, leading to unexpected
   fragmentation at the IP layer.

2. Fragmentation with problematic IP IDs:
   When net.ipv4.vs.pmtu_disc=1 and a GSO packet with multiple segments
   is fragmented after encapsulation, each segment gets a sequentially
   incremented IP ID (0, 1, 2, ...). This happens because:

   a) The GSO packet bypasses MTU check and gets encapsulated
   b) At __ip_finish_output, the oversized GSO packet is split into
      separate SKBs (one per segment), with IP IDs incrementing
   c) Each SKB is then fragmented again based on the actual MTU

   This sequential IP ID allocation differs from the expected behavior
   and can cause issues with fragment reassembly and packet tracking.

Fix this by properly validating GSO packets using
skb_gso_validate_network_len(). This function correctly validates
whether the GSO segments will fit within the MTU after segmentation. If
validation fails, send an ICMP Fragmentation Needed message to enable
proper PMTU discovery.

Fixes: 4cdd34084d ("netfilter: nf_conntrack_ipv6: improve fragmentation handling")
Signed-off-by: Yingnan Zhang <342144303@qq.com>
Acked-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2026-06-01 17:35:39 +02:00
arch arm64: dts: qcom: sdm845-xiaomi-beryllium: Mark l1a regulator as powered during boot 2026-06-01 17:35:33 +02:00
block blk-mq: use quiesced elevator switch when reinitializing queues 2026-06-01 17:35:09 +02:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:22:01 +02:00
crypto crypto: authencesn - reject short ahash digests during instance creation 2026-06-01 17:35:18 +02:00
Documentation Documentation: fix a hugetlbfs reservation statement 2026-06-01 17:35:32 +02:00
drivers pppoe: drop PFC frames 2026-06-01 17:35:39 +02:00
fs fs/ntfs3: terminate the cached volume label after UTF-8 conversion 2026-06-01 17:35:36 +02:00
include pppoe: drop PFC frames 2026-06-01 17:35:39 +02:00
init init: handle bootloader identifier in kernel parameters 2025-10-19 16:21:45 +02:00
io_uring io_uring/poll: fix backport of io_poll_add() changes 2026-06-01 17:35:17 +02:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:05:26 +01:00
kernel tracing: Rebuild full_name on each hist_field_name() call 2026-06-01 17:35:34 +02:00
lib lib/ts_kmp: fix integer overflow in pattern length calculation 2026-06-01 17:35:14 +02:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm mm: blk-cgroup: fix use-after-free in cgwb_release_workfn() 2026-06-01 17:35:08 +02:00
net ipvs: fix MTU check for GSO packets in tunnel mode 2026-06-01 17:35:39 +02:00
samples samples: mei: Fix building on musl libc 2025-08-28 16:24:07 +02:00
scripts scripts/dtc: Remove unused dts_version in dtc-lexer.l 2026-06-01 17:35:12 +02:00
security ima: check return value of crypto_shash_final() in boot aggregate 2026-06-01 17:35:34 +02:00
sound ALSA: sc6000: Keep the programmed board state in card-private data 2026-06-01 17:35:32 +02:00
tools perf util: Kill die() prototype, dead for a long time 2026-06-01 17:35:35 +02:00
usr kbuild: hdrcheck: fix cross build with clang 2025-06-27 11:05:22 +01:00
virt KVM: Don't clobber irqfd routing type when deassigning irqfd 2026-02-11 13:35:27 +01:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore Remove *.orig pattern from .gitignore 2024-10-17 15:11:10 +02:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS staging: rtl8712: Remove driver using deprecated API wext 2025-12-07 06:09:36 +09:00
Makefile Linux 5.15.208 2026-05-23 13:40:45 +02:00
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.