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    tcp: do not mess with listener sk_wmem_alloc · b3d05147
    Eric Dumazet 提交于
    When removing sk_refcnt manipulation on synflood, I missed that
    using skb_set_owner_w() was racy, if sk->sk_wmem_alloc had already
    transitioned to 0.
    
    We should hold sk_refcnt instead, but this is a big deal under attack.
    (Doing so increase performance from 3.2 Mpps to 3.8 Mpps only)
    
    In this patch, I chose to not attach a socket to syncookies skb.
    
    Performance is now 5 Mpps instead of 3.2 Mpps.
    
    Following patch will remove last known false sharing in
    tcp_rcv_state_process()
    
    Fixes: 3b24d854 ("tcp/dccp: do not touch listener sk_refcnt under synflood")
    Signed-off-by: NEric Dumazet <edumazet@google.com>
    Signed-off-by: NDavid S. Miller <davem@davemloft.net>
    b3d05147
tcp_output.c 101.5 KB