tcp: ECN blackhole should not force quickack mode

While playing with a new ADSL box at home, I discovered that ECN
blackhole can trigger suboptimal quickack mode on linux : We send one
ACK for each incoming data frame, without any delay and eventual
piggyback.

This is because TCP_ECN_check_ce() considers that if no ECT is seen on a
segment, this is because this segment was a retransmit.

Refine this heuristic and apply it only if we seen ECT in a previous
segment, to detect ECN blackhole at IP level.

Signed-off-by: Eric Dumazet <[email protected]>
CC: Jamal Hadi Salim <[email protected]>
CC: Jerry Chu <[email protected]>
CC: Ilpo Järvinen <[email protected]>
CC: Jim Gettys <[email protected]>
CC: Dave Taht <[email protected]>
Acked-by: Ilpo Järvinen <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

0 files changed, 0 insertions, 0 deletions