mptcp: cope with later TCP fallback

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With MPTCP v1, passive connections can fallback to TCP after the
subflow becomes established:

syn + MP_CAPABLE ->
               <- syn, ack + MP_CAPABLE

ack, seq = 3    ->
        // OoO packet is accepted because in-sequence
        // passive socket is created, is in ESTABLISHED
	// status and tentatively as MP_CAPABLE

ack, seq = 2     ->
        // no MP_CAPABLE opt, subflow should fallback to TCP

We can't use the 'subflow' socket fallback, as we don't have
it available for passive connection.

Instead, when the fallback is detected, replace the mptcp
socket with the underlying TCP subflow. Beyond covering
the above scenario, it makes a TCP fallback socket as efficient
as plain TCP ones.

Co-developed-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Christoph Paasch <cpaasch@apple.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

...

This commit is contained in:

Paolo Abeni 2020-01-21 16:56:33 -08:00 • committed by David S. Miller

parent d22f4988ff

commit 8ab183deb2

2 changed files with 103 additions and 17 deletions

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119

net/mptcp/protocol.c

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1

net/mptcp/protocol.h

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