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Jiri Bohac a6d95c5a62 Revert "xfrm: xfrm_state_mtu should return at least 1280 for ipv6"
This reverts commit b515d26372.

Commit b515d26372 ("xfrm: xfrm_state_mtu
should return at least 1280 for ipv6") in v5.14 breaks the TCP MSS
calculation in ipsec transport mode, resulting complete stalls of TCP
connections. This happens when the (P)MTU is 1280 or slighly larger.

The desired formula for the MSS is:
MSS = (MTU - ESP_overhead) - IP header - TCP header

However, the above commit clamps the (MTU - ESP_overhead) to a
minimum of 1280, turning the formula into
MSS = max(MTU - ESP overhead, 1280) -  IP header - TCP header

With the (P)MTU near 1280, the calculated MSS is too large and the
resulting TCP packets never make it to the destination because they
are over the actual PMTU.

The above commit also causes suboptimal double fragmentation in
xfrm tunnel mode, as described in
https://lore.kernel.org/netdev/20210429202529.codhwpc7w6kbudug@dwarf.suse.cz/

The original problem the above commit was trying to fix is now fixed
by commit 6596a02295 ("xfrm: fix MTU
regression").

Signed-off-by: Jiri Bohac <jbohac@suse.cz>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
2022-01-27 07:34:06 +01:00
arch Networking fixes for 5.17-rc1, including fixes from netfilter, bpf. 2022-01-20 10:57:05 +02:00
block SCSI misc on 20220113 2022-01-14 14:37:34 +01:00
certs certs: move scripts/extract-cert to certs/ 2022-01-08 18:28:21 +09:00
crypto lib/crypto: add prompts back to crypto libraries 2022-01-18 13:03:55 +01:00
Documentation Networking fixes for 5.17-rc1, including fixes from netfilter, bpf. 2022-01-20 10:57:05 +02:00
drivers net: stmmac: remove unused members in struct stmmac_priv 2022-01-24 13:31:45 +00:00
fs Merge branch 'akpm' (patches from Andrew) 2022-01-20 10:41:01 +02:00
include Revert "xfrm: xfrm_state_mtu should return at least 1280 for ipv6" 2022-01-27 07:34:06 +01:00
init Kbuild updates for v5.17 2022-01-19 11:15:19 +02:00
ipc shm: extend forced shm destroy to support objects from several IPC nses 2021-11-20 10:35:54 -08:00
kernel Networking fixes for 5.17-rc1, including fixes from netfilter, bpf. 2022-01-20 10:57:05 +02:00
lib Networking fixes for 5.17-rc1, including fixes from netfilter, bpf. 2022-01-20 10:57:05 +02:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm Merge branch 'akpm' (patches from Andrew) 2022-01-20 10:41:01 +02:00
net Revert "xfrm: xfrm_state_mtu should return at least 1280 for ipv6" 2022-01-27 07:34:06 +01:00
samples Merge branch 'akpm' (patches from Andrew) 2022-01-20 10:41:01 +02:00
scripts Merge branch 'akpm' (patches from Andrew) 2022-01-20 10:41:01 +02:00
security fs.idmapped.v5.17 2022-01-11 14:26:55 -08:00
sound virtio,vdpa,qemu_fw_cfg: features, cleanups, fixes 2022-01-18 10:05:48 +02:00
tools selftests: net: ioam: expect support for Queue depth data 2022-01-21 19:26:39 -08:00
usr kbuild: rename cmd_{bzip2,lzma,lzo,lz4,xzkern,zstd22} 2022-01-14 02:54:05 +09:00
virt RISCV: 2022-01-16 16:15:14 +02:00
.clang-format genirq/msi: Make interrupt allocation less convoluted 2021-12-16 22:22:20 +01:00
.cocciconfig
.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 .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap RISCV: 2022-01-16 16:15:14 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Removing Ohad from remoteproc/rpmsg maintenance 2021-12-08 10:09:40 -07:00
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 wireless fixes for v5.17 2022-01-21 11:23:33 +00:00
Makefile Kbuild updates for v5.17 2022-01-19 11:15:19 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -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 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.