Re: [TLS] Sending fatal alerts over TCP

[Martin Rex <[e-mail]>]

Marsh Ray wrote:
> 
> On 12/21/2011 01:13 PM, Martin Rex wrote:
> >
> > Unless the local application performs a shutdown(), the TCP implementation
> > of Y MUST continue to deliver data that was received.
> 
> This seems relevant http://tools.ietf.org/html/rfc793
> 
> > [when in state:] ESTABLISHED  FIN-WAIT-1 FIN-WAIT-2 CLOSE-WAIT
> >
> >         If the RST bit is set then, any outstanding RECEIVEs and SEND
> >         should receive "reset" responses.  All segment queues should be
> >         flushed.  Users should also receive an unsolicited general
> >         "connection reset" signal.  Enter the CLOSED state, delete the
> >         TCB, and return.
> 
> This part about "all segment queues should be flushed" suggests to me 
> that received-but-undelivered application data MAY or SHOULD be 
> discarded. Deleting the TCB altogether certainly sounds final.


In case that you're referring to  page 70,
this text appears in a section

  "second check the RST bit,"

and can only be ever reached when it was
not fully processed by the previous "first check sequence number"
a page before, which says:




  first check sequence number

      SYN-RECEIVED STATE
      ESTABLISHED STATE
      FIN-WAIT-1 STATE
      FIN-WAIT-2 STATE
      CLOSE-WAIT STATE
      CLOSING STATE
      LAST-ACK STATE
      TIME-WAIT STATE

        Segments are processed in sequence.  Initial tests on arrival
        are used to discard old duplicates, but further processing is
        done in SEG.SEQ order.  If a segment's contents straddle the
        boundary between old and new, only the new parts should be
        processed.

        There are four cases for the acceptability test for an incoming
        segment:

        Segment Receive  Test
        Length  Window
        ------- -------  -------------------------------------------

           0       0     SEG.SEQ = RCV.NXT

           0      >0     RCV.NXT =< SEG.SEQ < RCV.NXT+RCV.WND

          >0       0     not acceptable

          >0      >0     RCV.NXT =< SEG.SEQ < RCV.NXT+RCV.WND
                      or RCV.NXT =< SEG.SEQ+SEG.LEN-1 < RCV.NXT+RCV.WND

        If the RCV.WND is zero, no segments will be acceptable, but
        special allowance should be made to accept valid ACKs, URGs and
        RSTs.

*>      If an incoming segment is not acceptable, an acknowledgment
*>      should be sent in reply (unless the RST bit is set, if so drop
*>      the segment and return):

          <SEQ=SND.NXT><ACK=RCV.NXT><CTL=ACK>

        After sending the acknowledgment, drop the unacceptable segment
        and return.


-Martin