svn commit: r229665 - head/sys/netinet

[Sergey Kandaurov]

On 6 January 2012 02:29, John Baldwin <jhb at freebsd.org> wrote:
> Author: jhb
> Date: Thu Jan  5 22:29:11 2012
> New Revision: 229665
> URL: http://svn.freebsd.org/changeset/base/229665
>
> Log:
>  Remove the assertion from tcp_input() that rcv_nxt is always greater
>  than or equal to rcv_adv and fix tcp_twstart() to handle this case by
>  assuming the last window was zero rather than a negative value.
>
>  The code in tcp_input() already safely handled this case.  It can happen
>  due to delayed ACKs along with a remote sender that sends data beyond
>  the window we previously advertised.  If we have room in our socket buffer
>  for the extra data beyond the advertised window, we will accept it.
>  However, if the ACK for that segment is delayed, then we will not
>  effectively fixup rcv_adv to account for that extra data until the
>  next segment arrives and forces out an ACK.  When that next segment
>  arrives, rcv_nxt will be beyond rcv_adv.
>
>  Tested by:    pjd
>  MFC after:    1 week
>
> Modified:
>  head/sys/netinet/tcp_input.c
>  head/sys/netinet/tcp_timewait.c
>
> Modified: head/sys/netinet/tcp_input.c
> ==============================================================================
> --- head/sys/netinet/tcp_input.c        Thu Jan  5 22:28:40 2012        (r229664)
> +++ head/sys/netinet/tcp_input.c        Thu Jan  5 22:29:11 2012        (r229665)
> @@ -1795,9 +1795,6 @@ tcp_do_segment(struct mbuf *m, struct tc
>        win = sbspace(&so->so_rcv);
>        if (win < 0)
>                win = 0;
> -       KASSERT(SEQ_GEQ(tp->rcv_adv, tp->rcv_nxt),
> -           ("tcp_input negative window: tp %p rcv_nxt %u rcv_adv %u", tp,
> -           tp->rcv_nxt, tp->rcv_adv));
>        tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt));
>
>        /* Reset receive buffer auto scaling when not in bulk receive mode. */
>
> Modified: head/sys/netinet/tcp_timewait.c
> ==============================================================================
> --- head/sys/netinet/tcp_timewait.c     Thu Jan  5 22:28:40 2012        (r229664)
> +++ head/sys/netinet/tcp_timewait.c     Thu Jan  5 22:29:11 2012        (r229665)
> @@ -242,10 +242,10 @@ tcp_twstart(struct tcpcb *tp)
>        /*
>         * Recover last window size sent.
>         */
> -       KASSERT(SEQ_GEQ(tp->rcv_adv, tp->rcv_nxt),
> -           ("tcp_twstart negative window: tp %p rcv_nxt %u rcv_adv %u", tp,
> -           tp->rcv_nxt, tp->rcv_adv));
> -       tw->last_win = (tp->rcv_adv - tp->rcv_nxt) >> tp->rcv_scale;
> +       if (SEQ_GE(tp->rcv_adv, tp->rcv_nxt))
> +               tw->last_win = (tp->rcv_adv - tp->rcv_nxt) >> tp->rcv_scale;
> +       else
> +               tw->last_win = 0;
>
>        /*
>         * Set t_recent if timestamps are used on the connection.


Hi, Looks like a typo there:
/usr/src/sys/netinet/tcp_timewait.c: In function 'tcp_twstart':
/usr/src/sys/netinet/tcp_timewait.c:245: warning: implicit declaration
of function 'SEQ_GE'
/usr/src/sys/netinet/tcp_timewait.c:245: warning: nested extern
declaration of 'SEQ_GE' [-Wnested-externs]

-- 
wbr,
pluknet