Re: Unacceptable ACK in SYN_RCVD state handling

[Murali Bashyam <[e-mail]>]

Bob Braden wrote:

>   *>
>   *> No, the scenario that applies is described on page 68 (sequence number check),
>
> Yes, sorry, I misinterpreted what you were asking (ACK field as opposed
> to sequence field of ACK segment (But the man DID say "receive window"...
> mumble).
>
>   *>
>   *> The point u mentioned above is the conflict i am having as well, it seems to me
>   *> that retransmitting
>   *> a SYN-ACK seems the right thing to do. But the BSD stack doesn't seem to be
>   *> doing that.
>
> I thought you said earlier that the BSD DOES retransmit the SYN.  In

Sorry, the BSD stack does retransmit the SYN. Linux sends a pure ACK in response.

Murali

>
> any case, I would agree that the text of RFC 793 seems to say
> otherwise.  This particular test is one that has caused a great deal of
> confusion over the years.  From the underlying logic of TCP,  I believe
> that retransmitting the SYN is OK.  So it seems you can choose either
> interpretation you want (unless there is some  subtle security
> implication.)

>
> Bob Braden
>
>   *>
>   *> Murali
>   *>
>   *>
>   *>
>   *>
>   *> >
>   *> >
>   *> > Bob Braden
>   *>