Date:   Mon, 18 Dec 2017 13:50:55 -0800
From:   Christoph Paasch <cpaasch@...le.com>
To:     netdev@...r.kernel.org
Cc:     Eric Dumazet <edumazet@...gle.com>,
        Mat Martineau <mathew.j.martineau@...ux.intel.com>,
        Alexei Starovoitov <ast@...nel.org>
Subject: [RFC 00/14] Generic TCP-option framework and adoption for TCP-SMC and
 TCP-MD5

This patchset introduces a generic framework for handling TCP-options.

TCP-options like TCP_MD5 and SMC are rather rare use-cases, but their
implementation is rather intrusive to the TCP-stack. Other, more recent
TCP extensions like TCP-crypt, MPTCP or TCP-AO would make this situation
even worse.

This new framework allows to add these TCP-options in a modular way. Writing,
reading and acting upon these options is done through callbacks that get
registered to a TCP-socket. A TCP-socket has a list of "extra" TCP-options
that it will use.

We make TCP-SMC and TCP-MD5SIG adopt this new framework. As can be seen, there
is now no more TCP-SMC code in the TCP-files and the TCP-MD5 code has been
reduced to a bare minimum.

This patchset is admittedly rather big, but we wanted to show where the
framework will lead to and what it enables. Suggestions as to how to better
structure the patchset is appreciated.

One point of discussion might be whether or not we should use static-keys
before accessing the tcp_option_list to avoid branching and the additional
access to the tcp_sock, request-sock, time-wait-sock structure.
The way static keys could be used is that they get incremented each time a
socket starts using one of the new TCP-options and decremented when the socket
eventually gets destroyed. A caveat of this design would be that if a host keeps
on creating/closing these sockets in a sequence, each time we go into the slow
path of the static keys occuring potentially a big overhead to update all the
jump-labels.
For now we opted for a simple if (unlikely(!hlist_empty(...)) check.

Feedback is very welcome!


Thanks,
Mat & Christoph


Christoph Paasch (13):
  tcp: Write options after the header has been fully done
  tcp: Pass sock and skb to tcp_options_write
  tcp: Allow tcp_fast_parse_options to drop segments
  tcp_smc: Make smc_parse_options return 1 on success
  tcp_smc: Make SMC use TCP extra-option framework
  tcp_md5: Don't pass along md5-key
  tcp_md5: Detect key inside tcp_v4_send_ack instead of passing it as an
    argument
  tcp_md5: Detect key inside tcp_v6_send_response instead of passing it
    as an argument
  tcp_md5: Check for TCP_MD5 after TCP Timestamps in
    tcp_established_options
  tcp_md5: Move TCP-MD5 code out of TCP itself
  tcp_md5: Use tcp_extra_options in output path
  tcp_md5: Cleanup TCP-code
  tcp_md5: Use TCP extra-options on the input path

Mat Martineau (1):
  tcp: Register handlers for extra TCP options

 drivers/infiniband/hw/cxgb4/cm.c |    2 +-
 include/linux/inet_diag.h        |    1 +
 include/linux/tcp.h              |   43 +-
 include/linux/tcp_md5.h          |   39 ++
 include/net/inet_sock.h          |    3 +-
 include/net/tcp.h                |  213 +++---
 net/ipv4/Makefile                |    1 +
 net/ipv4/syncookies.c            |    6 +-
 net/ipv4/tcp.c                   |  391 ++++++++---
 net/ipv4/tcp_diag.c              |   81 +--
 net/ipv4/tcp_input.c             |  137 ++--
 net/ipv4/tcp_ipv4.c              |  556 ++--------------
 net/ipv4/tcp_md5.c               | 1359 ++++++++++++++++++++++++++++++++++++++
 net/ipv4/tcp_minisocks.c         |   77 +--
 net/ipv4/tcp_output.c            |  182 +----
 net/ipv6/syncookies.c            |    6 +-
 net/ipv6/tcp_ipv6.c              |  390 ++---------
 net/smc/af_smc.c                 |  190 +++++-
 18 files changed, 2227 insertions(+), 1450 deletions(-)
 create mode 100644 include/linux/tcp_md5.h
 create mode 100644 net/ipv4/tcp_md5.c

-- 
2.15.0

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