• Neal Cardwell's avatar
    tcp: switch snt_synack back to measuring transmit time of first SYNACK · 86c6a2c7
    Neal Cardwell authored
    Always store in snt_synack the time at which the server received the
    first client SYN and attempted to send the first SYNACK.
    
    Recent commit aa27fc50 ("tcp: tcp_v[46]_conn_request: fix snt_synack
    initialization") resolved an inconsistency between IPv4 and IPv6 in
    the initialization of snt_synack. This commit brings back the idea
    from 843f4a55 (tcp: use tcp_v4_send_synack on first SYN-ACK), which
    was going for the original behavior of snt_synack from the commit
    where it was added in 9ad7c049 ("tcp: RFC2988bis + taking RTT
    sample from 3WHS for the passive open side") in v3.1.
    
    In addition to being simpler (and probably a tiny bit faster),
    unconditionally storing the time of the first SYNACK attempt has been
    useful because it allows calculating a performance metric quantifying
    how long it took to establish a passive TCP connection.
    Signed-off-by: default avatarNeal Cardwell <ncardwell@google.com>
    Signed-off-by: default avatarYuchung Cheng <ycheng@google.com>
    Cc: Octavian Purdila <octavian.purdila@intel.com>
    Cc: Jerry Chu <hkchu@google.com>
    Acked-by: default avatarOctavian Purdila <octavian.purdila@intel.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    86c6a2c7
tcp_ipv6.c 49.5 KB