• Sowmini Varadhan's avatar
    RDS: TCP: Track peer's connection generation number · 905dd418
    Sowmini Varadhan authored
    The RDS transport has to be able to distinguish between
    two types of failure events:
    (a) when the transport fails (e.g., TCP connection reset)
        but the RDS socket/connection layer on both sides stays
        the same
    (b) when the peer's RDS layer itself resets (e.g., due to module
        reload or machine reboot at the peer)
    In case (a) both sides must reconnect and continue the RDS messaging
    without any message loss or disruption to the message sequence numbers,
    and this is achieved by rds_send_path_reset().
    
    In case (b) we should reset all rds_connection state to the
    new incarnation of the peer. Examples of state that needs to
    be reset are next expected rx sequence number from, or messages to be
    retransmitted to, the new incarnation of the peer.
    
    To achieve this, the RDS handshake probe added as part of
    commit 5916e2c1 ("RDS: TCP: Enable multipath RDS for TCP")
    is enhanced so that sender and receiver of the RDS ping-probe
    will add a generation number as part of the RDS_EXTHDR_GEN_NUM
    extension header. Each peer stores local and remote generation
    numbers as part of each rds_connection. Changes in generation
    number will be detected via incoming handshake probe ping
    request or response and will allow the receiver to reset rds_connection
    state.
    Signed-off-by: default avatarSowmini Varadhan <sowmini.varadhan@oracle.com>
    Acked-by: default avatarSantosh Shilimkar <santosh.shilimkar@oracle.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    905dd418
rds.h 27.6 KB