• Yuchung Cheng's avatar
    tcp: change IPv6 flow-label upon receiving spurious retransmission · 7788174e
    Yuchung Cheng authored
    Currently a Linux IPv6 TCP sender will change the flow label upon
    timeouts to potentially steer away from a data path that has gone
    bad. However this does not help if the problem is on the ACK path
    and the data path is healthy. In this case the receiver is likely
    to receive repeated spurious retransmission because the sender
    couldn't get the ACKs in time and has recurring timeouts.
    
    This patch adds another feature to mitigate this problem. It
    leverages the DSACK states in the receiver to change the flow
    label of the ACKs to speculatively re-route the ACK packets.
    In order to allow triggering on the second consecutive spurious
    RTO, the receiver changes the flow label upon sending a second
    consecutive DSACK for a sequence number below RCV.NXT.
    Signed-off-by: default avatarYuchung Cheng <ycheng@google.com>
    Signed-off-by: default avatarNeal Cardwell <ncardwell@google.com>
    Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    7788174e
tcp.c 101 KB