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mptcp: do not shrink snd_nxt when recovering

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[ Upstream commit 0d199e4363b482badcedba764e2aceab53a4a10a ]

When recovering after a link failure, snd_nxt should not be set to a
lower value.  Else, update of snd_nxt is broken because:

  msk->snd_nxt += ret; (where ret is number of bytes sent)

assumes that snd_nxt always moves forward.
After reduction, its possible that snd_nxt update gets out of sync:
dfrag we just sent might have had a data sequence number even past
recovery_snd_nxt.

This change factors the common msk state update to a helper
and updates snd_nxt based on the current dfrag data sequence number.

The conditional is required for the recovery phase where we may
re-transmit old dfrags that are before current snd_nxt.

After this change, snd_nxt only moves forward and covers all in-sequence
data that was transmitted.

recovery_snd_nxt is retained to detect when recovery has completed.

Fixes: 1e1d9d6f11 ("mptcp: handle pending data on closed subflow")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Florian Westphal
2021-09-24 14:12:34 -07:00
committed by Greg Kroah-Hartman
parent eade470b43
commit c9f95c6783
2 changed files with 34 additions and 17 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
net/mptcp/options.c
View File

@@ -1019,11 +1019,9 @@ static void ack_update_msk(struct mptcp_sock *msk,
old_snd_una = msk->snd_una;
new_snd_una = mptcp_expand_seq(old_snd_una, mp_opt->data_ack, mp_opt->ack64);
/* ACK for data not even sent yet and even above recovery bound? Ignore.*/
if (unlikely(after64(new_snd_una, snd_nxt))) {
if (!msk->recovery || after64(new_snd_una, msk->recovery_snd_nxt))
new_snd_una = old_snd_una;
}
/* ACK for data not even sent yet? Ignore.*/
if (unlikely(after64(new_snd_una, snd_nxt)))
new_snd_una = old_snd_una;
new_wnd_end = new_snd_una + tcp_sk(ssk)->snd_wnd;