FreeTDS Development Group

[Brian Bruns <camber AT ais.org>]

There should be no need for a TDS_CANCELLING state, since we enter 
tds_process_cancel() and don't (well shouldn't maybe) leave until we have 
completed the cancel.  The real problem is we call tds_get_byte and he 
makes only one attempt at reading a packet

if (tds->in_pos >= tds->in_len) {
        if (!tds->s || !tds_read_packet(tds)) 
                return (0);
        }
        return tds->in_buf[tds->in_pos++];
}

is the problem code.  A simple fix is:
  
...
        while (tds->s && (tds_read_packet(tds) || tds->in_buf[0] == 0x0f))
...

which is kinda kludgy.  A better solution is to modify tds_read_packet to 
return -1 instead of 0 on error.  Since it is called only two places, both 
within read.c and one ignores the return code, it's fairly localized 
behaviour.

Brian

On Wed, 4 Sep 2002, ZIGLIO Frediano wrote:

> Ok, understood the problem.
> 
> You send cancel
> Server return a cancel only-header packet.
> tds_process_cancel read a byte. 
> If only-header packet is received tds_get_byte return a zero.
> tds_process_cancel on received zero act as a done/cancel token (this patch
> is not so good, see diff between version 1.25 and 1.26 in token.c at
> http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/freetds/freetds/src/tds/token
> .c.diff?r1=1.25&r2=1.26&sortby=date, IMHO should be removed..).
> Replacing the if in tds_get_byte with a while whould resolve partially the
> problem.
> 
> Note that while sending cancel server can send another packet...
> I suggest to add a TDS_CANCELLING state, read should discard all packet in
> cancelling and stop reading the only-header cancel packet, then change state
> (TDS_CANCELLED ??) and act in the usually mode.
> 
> Also before sending cancel packet we should discard partial packet (just a
> init packet before sending it).
> 
> Seem not so difficult but should be tested accurately...
> 
> freddy77
>