mbox series

[net-next,0/4] mptcp: add TCP_NOTSENT_LOWAT sockopt support

Message ID 20240301-upstream-net-next-20240301-mptcp-tcp_notsent_lowat-v1-0-415f0e8ed0e1@kernel.org
Headers
Series mptcp: add TCP_NOTSENT_LOWAT sockopt support |

Message

Matthieu Baerts (NGI0) March 1, 2024, 5:43 p.m. UTC 
  Patch 3 does the magic of adding TCP_NOTSENT_LOWAT support, all the
other ones are minor cleanup seen along when working on the new feature.

Note that this feature relies on the existing accounting for snd_nxt.
Such accounting is not 110% accurate as it tracks the most recent
sequence number queued to any subflow, and not the actual sequence
number sent on the wire. Paolo experimented a lot, trying to implement
the latter, and in the end it proved to be both "too complex" and "not
necessary".

The complexity raises from the need for additional lock and a lot of
refactoring to introduce such protections without adding significant
overhead. Additionally, snd_nxt is currently used and exposed with the
current semantic by the internal packet scheduling. Introducing a
different tracking will still require us to keep the old one.

More interestingly, a more accurate tracking could be not strictly
necessary: as the MPTCP socket enqueues data to the subflows only up to
the available send window, any enqueue data is sent on the wire
instantly, without any blocking operation short or a drop in the tx path
at the nft or TC layer.

Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
Paolo Abeni (4):
      mptcp: cleanup writer wake-up
      mptcp: avoid some duplicate code in socket option handling
      mptcp: implement TCP_NOTSENT_LOWAT support
      mptcp: cleanup SOL_TCP handling

 net/mptcp/protocol.c | 54 ++++++++++++++++++++++++++-------------
 net/mptcp/protocol.h | 42 +++++++++++++++++++++++--------
 net/mptcp/sockopt.c  | 71 +++++++++++++++++++++++-----------------------------
 3 files changed, 101 insertions(+), 66 deletions(-)
---
base-commit: e960825709330cb199d209740326cec37e8c419d
change-id: 20240301-upstream-net-next-20240301-mptcp-tcp_notsent_lowat-770cab93d253

Best regards,

Comments

patchwork-bot+netdevbpf@kernel.org March 4, 2024, 11 a.m. UTC | #1 
Hello:

This series was applied to netdev/net-next.git (main)
by David S. Miller <davem@davemloft.net>:

On Fri, 01 Mar 2024 18:43:43 +0100 you wrote:
> Patch 3 does the magic of adding TCP_NOTSENT_LOWAT support, all the
> other ones are minor cleanup seen along when working on the new feature.
> 
> Note that this feature relies on the existing accounting for snd_nxt.
> Such accounting is not 110% accurate as it tracks the most recent
> sequence number queued to any subflow, and not the actual sequence
> number sent on the wire. Paolo experimented a lot, trying to implement
> the latter, and in the end it proved to be both "too complex" and "not
> necessary".
> 
> [...]

Here is the summary with links:
  - [net-next,1/4] mptcp: cleanup writer wake-up
    https://git.kernel.org/netdev/net-next/c/037db6ea57da
  - [net-next,2/4] mptcp: avoid some duplicate code in socket option handling
    https://git.kernel.org/netdev/net-next/c/a74762675f70
  - [net-next,3/4] mptcp: implement TCP_NOTSENT_LOWAT support
    https://git.kernel.org/netdev/net-next/c/29b5e5ef8739
  - [net-next,4/4] mptcp: cleanup SOL_TCP handling
    https://git.kernel.org/netdev/net-next/c/7f71a337b515

You are awesome, thank you!