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4618e195f9
ECN bits in TOS are always cleared when sending in ACKs in TW. Clearing them is problematic for TCP flows that used Accurate ECN because ECN bits decide which service queue the packet is placed into (L4S vs Classic). Effectively, TW ACKs are always downgraded from L4S to Classic queue which might impact, e.g., delay the ACK will experience on the path compared with the other packets of the flow. Change the TW ACK sending code to differentiate: - In tcp_v4_send_reset(), commitba9e04a7dd("ip: fix tos reflection in ack and reset packets") cleans ECN bits for TW reset and this is not affected. - In tcp_v4_timewait_ack(), ECN bits for all TW ACKs are cleaned. But now only ECN bits of ACKs for oow data or paws_reject are cleaned, and ECN bits of other ACKs will not be cleaned. - In tcp_v4_reqsk_send_ack(), commit66b13d99d9("ipv4: tcp: fix TOS value in ACK messages sent from TIME_WAIT") did not clean ECN bits of ACKs for oow data or paws_reject. But now the ECN bits rae cleaned for these ACKs. Signed-off-by: Ilpo Järvinen <ij@kernel.org> Signed-off-by: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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.