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Rev 2930 Rev 2937
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;;          GNU GENERAL PUBLIC LICENSE                             ;;
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;;          GNU GENERAL PUBLIC LICENSE                             ;;
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;;             Version 2, June 1991                                ;;
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;;             Version 2, June 1991                                ;;
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;;                                                                 ;;
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;;                                                                 ;;
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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$Revision: 2930 $
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$Revision: 2937 $
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macro   TCP_checksum IP1, IP2 {
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macro   TCP_checksum IP1, IP2 {
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macro TCP_set_persist socket {
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; First, check if retransmit timer is not set, retransmit and persist are mutually exclusive
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;        cmp     [socket + TCP_socket.timer_retransmission]
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; calculate RTO
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macro TCP_set_persist socket {
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;        mov     ecx, [socket + TCP_socket.t_srtt]
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;        shr     ecx, 2
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;int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
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;        add     ecx, [socket + TCP_socket.t_rttvar]
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;int tt;
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;        shr     ecx, 1
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;
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;tp->t_flags &= ~TF_PREVVALID;
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;        and     [socket + TCP_socket.t_flags], not TF_PREVVALID
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;
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;if (tcp_timer_active(tp, TT_REXMT))
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;if (tcp_timer_active(tp, TT_REXMT))
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;        panic("tcp_setpersist: retransmit pending");
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;        panic("tcp_setpersist: retransmit pending");
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;
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;; Start/restart persistance timer.
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; Start/restart persistance timer.
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;
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;TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], TCPTV_PERSMIN, TCPTV_PERSMAX);
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;TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], TCPTV_PERSMIN, TCPTV_PERSMAX);
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;tcp_timer_activate(tp, TT_PERSIST, tt);
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;tcp_timer_activate(tp, TT_PERSIST, tt);
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;        cmp     [socket + TCP_socket.t_rxtshift], TCP_MAXRXTSHIFT
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;        jae     @f
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;        inc     [socket + TCP_socket.t_rxtshift]
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;
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;      @@:
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;if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
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;        tp->t_rxtshift++;
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}
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}
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; eax = rtt
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; ebx = socket ptr
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align 4
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TCP_xmit_timer:
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;TODO: update stats
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        cmp     [ebx + TCP_SOCKET.t_rtt], 0
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        je      .no_rtt_yet
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; srtt is stored as a fixed point with 3 bits after the binary point.
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; The following magic is equivalent of the smoothing algorithm in rfc793 with an alpha of .875
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; (srtt = rtt/8 + srtt*7/8 in fixed point)
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; Adjust rtt to origin 0.
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        push    ecx
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        mov     ecx, [ebx + TCP_SOCKET.t_srtt]
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        shr     ecx, TCP_RTT_SHIFT
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        sub     eax, ecx
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        dec     eax
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        pop     ecx
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        add     [ebx + TCP_SOCKET.t_srtt], eax
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        ja      @f
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        mov     [ebx + TCP_SOCKET.t_srtt], 1
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  @@:
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; We accumulate a smoothed rtt variance (actually, a smoothed mean difference),
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; then set the retransmit timer to smoothed rtt + 4 times the smoothed variance.
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; rttvar is stored as fixed point with 2 bits after the binary point.
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; The following is equivalent to rfc793 smoothing with an alpha of .75
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; (rttvar = rttvar*3/4 + delta/4) (delta = eax)
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; get abs(eax)
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        push    edx
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        cdq
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        xor     eax, edx
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        sub     eax, edx
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        mov     edx, [ebx + TCP_SOCKET.t_rttvar]
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        shr     edx, TCP_RTTVAR_SHIFT
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        sub     eax, edx
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        pop     edx
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        add     [ebx + TCP_SOCKET.t_rttvar], eax
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        ja      @f
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        mov     [ebx + TCP_SOCKET.t_rttvar], 1
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  @@:
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        ret
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  .no_rtt_yet:
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        push    ecx