Merge branch 'tcp-3-fixes-for-retrans_stamp-and-undo-logic'

Merge branch 'tcp-3-fixes-for-retrans_stamp-and-undo-logic'

Neal Cardwell says:

====================
tcp: 3 fixes for retrans_stamp and undo logic

Geumhwan Yu <geumhwan.yu@samsung.com> recently reported and diagnosed
a regression in TCP loss recovery undo logic in the case where a TCP
connection enters fast recovery, is unable to retransmit anything due to
TSQ, and then receives an ACK allowing forward progress. The sender should
be able to undo the spurious loss recovery in this case, but was not doing
so. The first patch fixes this regression.

Running our suite of packetdrill tests with the first fix, the tests
highlighted two other small bugs in the way retrans_stamp is updated in
some rare corner cases. The second two patches fix those other two small
bugs.

Thanks to Geumhwan Yu for the bug report!
====================

Link: https://patch.msgid.link/20241001200517.2756803-1-ncardwell.sw@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>