Re: [PATCH v2] mptcp: do not drop partial packets

[Matthieu Baerts]

Hi Shardul,

On 22/04/2026 16:39, Shardul Bankar wrote:
> When a packet arrives with map_seq < ack_seq < end_seq, the beginning
> of the packet has already been acknowledged but the end contains new
> data.  Currently the entire packet is dropped as "old data," forcing
> the sender to retransmit.
> 
> Instead, skip the already-acked bytes by adjusting the skb offset and
> enqueue only the new portion.  Update bytes_received and ack_seq to
> reflect the new data consumed.

Thank you for the v2.

I didn't review it (yet), but just to let you know that there are some
rules on Netdev [1] (that usually also applied on MPTCP side), and an
important one is:

 - don't repost your patches within one 24h period

Each version generates a lot of emails that are sent and need to be
triaged. With the high volume, it is then harder for us to follow, plus
a lot of shared resources are used, etc.

One last thing, because this patch is not an urgent fix, do you mind
sending new versions only the to MPTCP ML: to a restricted number of
people for the first versions, there is enough traffic on Netdev.

[1] https://docs.kernel.org/process/maintainer-netdev.html

> A previous attempt at this fix (commit 1d2ce718811a ("mptcp: do not
> drop partial packets"), reverted in commit bf39160c4218 ("Revert

Note: these two commits should not be mentioned here, they have only
been applied to the MPTCP tree, but not upstreamed. Instead, please use
lore links, e.g.

https://lore.kernel.org/c9b426a4e163aa3c4fe8b80c79f1a610f47ae7d8.1763075056.git.pabeni@xxxxxxxxxx

> "mptcp: do not drop partial packets"")) also added a zero-window
> check and changed rcv_wnd_sent initialization, which caused test
> regressions.  This version addresses only the partial packet handling
> without modifying receive window accounting.
> 
> Fixes: ab174ad8ef76 ("mptcp: move ooo skbs into msk out of order queue.")
> Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/600
> Signed-off-by: Shardul Bankar <shardul.b@xxxxxxxxxxxxxxxxxx>

Checkpatch is complaining that the author of the patch is not the same
as the one who sent the patch; You probably need to run this command to
fix it:

  git commit --amend --reset-author

(when the patch is sent, `git format-patch` will add a second From: tag)

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.