Merge branch 'mptcp-misc-fixes-involving-fallback-to-tcp'

Merge branch 'mptcp-misc-fixes-involving-fallback-to-tcp'

Matthieu Baerts says:

====================
mptcp: misc. fixes involving fallback to TCP

- Patch 1: better handle DSS corruptions from a bugged peer: reducing
  warnings, doing a fallback or a reset depending on the subflow state.
  For >= v5.7.

- Patch 2: fix DSS corruption due to large pmtu xmit, where MPTCP was
  not taken into account. For >= v5.6.

- Patch 3: fallback when MPTCP opts are dropped after the first data
  packet, instead of resetting the connection. For >= v5.6.

- Patch 4: restrict the removal of a subflow to other closing states, a
  better fix, for a recent one. For >= v5.10.
====================

Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>