Re: seems dblib can get TDS protocol wrong in unusual case

2008/11/12 James K. Lowden <[email protected]>:
> Hayes, Ted (London) wrote:
>>
>> The problem is that dbsqlok() processes the TDS_DONEPROC_RESULT and with
>> no error flag set in done_flags, sets dbproc->dbresults_state to
>> _DB_RES_SUCCEED and exits.  This just makes the subsequent dbresults()
>> invocation exit immediately, and the results from the second half of the
>> packet are lost.  From the TDS specification, it seems to me that maybe
>> the TDS_DONE_MORE_RESULTS bit in done_flags should cause dbsqlok() to
>> continue looping to make further tds_process_tokens() invocations.
>>
>> I added this at line 4601 of dblib.c
>>
>> if (done_flags & TDS_DONE_MORE_RESULTS)
>> { break; }
>>
>> /* else continue with existing code..*/
>> tdsdump_log(...
>> dbproc->dbresults_state = _DB_RES_SUCCEED;
>>
>> With this change, dbsqlok() carries on and processes additional tokens
>> including the 0x7c (PROCID) at offset 0x171, the 0xa0 (COLNAME) at 0x17a
>> and 0xa1 (COLFMT) at 0x188.  dbsqlok() exits when the 0xae result token
>> is encountered at 0x191 and dbresults() then successfully processes the
>> rest of the packet.
>
> My, what a can of worms you've opened.
>
> For the nonce I've improved/broken dbsqlok with this:
>
> retcode = (done_flags & TDS_DONE_ERROR)? FAIL : SUCCEED;
> dbproc->dbresults_state = (done_flags & TDS_DONE_MORE_RESULTS)?
>        _DB_RES_NEXT_RESULT : _DB_RES_NO_MORE_RESULTS;
> return retcode;
>
> The code you found in 0.82 is decidedly odd.  The dbresults_state is set
> to rows/norows in the fail branch but only to succeed in the succeessful
> branch.
>
> But with the above, even if I include logic to continue gobbling packets
> (along the lines you suggest), 5 unit tests fail.  You might try your
> patch and see.  Specifically, t0018.c.
>
> Now, it might be that the test is bad.  It looks that way to me.  But I
> think I've reached a state of _DB_RES_VERY_CONFUSED, so I'm checking in
> the broken code and taking a break.
>
> Thanks for pointing this out.  Results processing is, er, important.
>

Well... this is the last stopover so I took some time to narrow down...
After some tests and after checking ms dblib bahavior I think this is
a false problem. Like ODBC in this case dblib generate a sort of empty
recordset with no rows. After dbsqlok set dbresults_state to
_DB_RES_SUCCEED dbresults returns SUCCEED without any token processing
but it also set dbresults_state to _DB_RES_NEXT_RESULT so on next
dbresults call token processing take place again without discupting
anything...

freddy77
_______________________________________________
FreeTDS mailing list
[email protected]
http://lists.ibiblio.org/mailman/listinfo/freetds