Merge branch 'sctp-pmtud-convergence'

Merge branch 'sctp-pmtud-convergence'

Xin Long says:

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sctp: make the PLPMTUD probe more effective and efficient

As David Laight noticed, it currently takes quite some time to find
the optimal pmtu in the Search state, and also lacks the black hole
detection in the Search Complete state. This patchset is to address
them to mke the PLPMTUD probe more effective and efficient.
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Signed-off-by: David S. Miller <davem@davemloft.net>