• Julian Anastasov's avatar
    tcp: accept socket after TCP_DEFER_ACCEPT period · d1b99ba4
    Julian Anastasov authored
    Willy Tarreau and many other folks in recent years
    were concerned what happens when the TCP_DEFER_ACCEPT period
    expires for clients which sent ACK packet. They prefer clients
    that actively resend ACK on our SYN-ACK retransmissions to be
    converted from open requests to sockets and queued to the
    listener for accepting after the deferring period is finished.
    Then application server can decide to wait longer for data
    or to properly terminate the connection with FIN if read()
    returns EAGAIN which is an indication for accepting after
    the deferring period. This change still can have side effects
    for applications that expect always to see data on the accepted
    socket. Others can be prepared to work in both modes (with or
    without TCP_DEFER_ACCEPT period) and their data processing can
    ignore the read=EAGAIN notification and to allocate resources for
    clients which proved to have no data to send during the deferring
    period. OTOH, servers that use TCP_DEFER_ACCEPT=1 as flag (not
    as a timeout) to wait for data will notice clients that didn't
    send data for 3 seconds but that still resend ACKs.
    Thanks to Willy Tarreau for the initial idea and to
    Eric Dumazet for the review and testing the change.
    Signed-off-by: default avatarJulian Anastasov <ja@ssi.bg>
    Acked-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    d1b99ba4
tcp_minisocks.c 22.1 KB