linux-kernel - [PATCH v3 0/3] net/tcp: Dynamically disable TCP-MD5 static key

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Date:   Fri, 11 Nov 2022 21:23:17 +0000
From:   Dmitry Safonov <dima@...sta.com>
To:     linux-kernel@...r.kernel.org, David Ahern <dsahern@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>
Cc:     Dmitry Safonov <dima@...sta.com>,
        Bob Gilligan <gilligan@...sta.com>,
        "David S. Miller" <davem@...emloft.net>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Francesco Ruggeri <fruggeri@...sta.com>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Salam Noureddine <noureddine@...sta.com>,
        netdev@...r.kernel.org
Subject: [PATCH v3 0/3] net/tcp: Dynamically disable TCP-MD5 static key

Changes from v2:
- Prevent key->enabled from turning negative by overflow from
  static_key_slow_inc() or static_key_fast_inc()
  (addressing Peter Zijlstra's review)
- Added checks if static_branch_inc() and static_key_fast_int()
  were successful to TCP-MD5 code.

Changes from v1:
- Add static_key_fast_inc() helper rather than open-coded atomic_inc()
  (as suggested by Eric Dumazet)

Version 2: 
https://lore.kernel.org/all/20221103212524.865762-1-dima@arista.com/T/#u
Version 1: 
https://lore.kernel.org/all/20221102211350.625011-1-dima@arista.com/T/#u

The static key introduced by commit 6015c71e656b ("tcp: md5: add
tcp_md5_needed jump label") is a fast-path optimization aimed at
avoiding a cache line miss.
Once an MD5 key is introduced in the system the static key is enabled
and never disabled. Address this by disabling the static key when
the last tcp_md5sig_info in system is destroyed.

Previously it was submitted as a part of TCP-AO patches set [1].
Now in attempt to split 36 patches submission, I send this independently.

Cc: Bob Gilligan <gilligan@...sta.com>
Cc: David Ahern <dsahern@...nel.org>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: Dmitry Safonov <0x7f454c46@...il.com>
Cc: Eric Dumazet <edumazet@...gle.com>
Cc: Francesco Ruggeri <fruggeri@...sta.com>
Cc: Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>
Cc: Jakub Kicinski <kuba@...nel.org>
Cc: Paolo Abeni <pabeni@...hat.com>
Cc: Salam Noureddine <noureddine@...sta.com>
Cc: netdev@...r.kernel.org
Cc: linux-kernel@...r.kernel.org

[1]: https://lore.kernel.org/all/20221027204347.529913-1-dima@arista.com/T/#u

Thanks,
            Dmitry

Dmitry Safonov (3):
  jump_label: Prevent key->enabled int overflow
  net/tcp: Separate tcp_md5sig_info allocation into
    tcp_md5sig_info_add()
  net/tcp: Disable TCP-MD5 static key on tcp_md5sig_info destruction

 include/linux/jump_label.h | 21 ++++++++--
 include/net/tcp.h          | 10 +++--
 kernel/jump_label.c        | 54 +++++++++++++++++-------
 net/ipv4/tcp.c             |  5 +--
 net/ipv4/tcp_ipv4.c        | 86 +++++++++++++++++++++++++++++++-------
 net/ipv4/tcp_minisocks.c   | 12 ++++--
 net/ipv4/tcp_output.c      |  4 +-
 net/ipv6/tcp_ipv6.c        | 10 ++---
 8 files changed, 150 insertions(+), 52 deletions(-)

base-commit: 4bbf3422df78029f03161640dcb1e9d1ed64d1ea
-- 
2.38.1