• Neal Cardwell's avatar
    tcp: stretch ACK fixes prep · e73ebb08
    Neal Cardwell authored
    
    
    LRO, GRO, delayed ACKs, and middleboxes can cause "stretch ACKs" that
    cover more than the RFC-specified maximum of 2 packets. These stretch
    ACKs can cause serious performance shortfalls in common congestion
    control algorithms that were designed and tuned years ago with
    receiver hosts that were not using LRO or GRO, and were instead
    politely ACKing every other packet.
    
    This patch series fixes Reno and CUBIC to handle stretch ACKs.
    
    This patch prepares for the upcoming stretch ACK bug fix patches. It
    adds an "acked" parameter to tcp_cong_avoid_ai() to allow for future
    fixes to tcp_cong_avoid_ai() to correctly handle stretch ACKs, and
    changes all congestion control algorithms to pass in 1 for the ACKed
    count. It also changes tcp_slow_start() to return the number of packet
    ACK "credits" that were not processed in slow start mode, and can be
    processed by the congestion control module in additive increase mode.
    
    In future patches we will fix tcp_cong_avoid_ai() to handle stretch
    ACKs, and fix Reno and CUBIC handling of stretch ACKs in slow start
    and additive increase mode.
    Reported-by: default avatarEyal Perry <eyalpe@mellanox.com>
    Signed-off-by: default avatarNeal Cardwell <ncardwell@google.com>
    Signed-off-by: default avatarYuchung Cheng <ycheng@google.com>
    Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    e73ebb08
tcp_yeah.c 6.88 KB