Re: IPFilter: need to classify packets according to value of certain bits of a field

Momina, aren't those bits the same as the formerly-defined DSCP
(Differentiated Services Code Point)? Can't you just say
"tcp and ip dscp = 10" or whatever? I don't understand your problem;
if you provided a specific Click configuration, perhaps using
FromIPSummaryDump in the style of the tests, showing what you expect
to happen, that would help. (Of course there's a gap between ip tos >
110 and ip tos < 110, namely ip tos == 110, but of course you know
this.)

Eddie


On Mon, Jul 22, 2013 at 7:41 AM, Momina Khan <[email protected]> wrote:
> Hi all i have been going through the IPFilter code for some time now ... i
> have to filter packets based on the value of the 6 high end unused bits of
> the TOS field in the IP header.
>
> have set _mask.u to 252 ... as per my understanding the value of the field
> to be checked is applied this mask before value checking
> The problem is that  the config parameter to be compared with _u.u leaves a
> gap between the greater than and less ( >110 and < 110) than value provided
> after the bit shift and in this gap of values the router neither labels
> packets as greater than nor less than. referring to the set_mask() routine.
> What routine actually does the comparison and filtering? is there detailed
> documentation of IPFilter code?
>
> from .click file
> ip_classifier :: IPClassifier(tcp and ip tos > 110,tcp and ip tos <
> 110/*protocol == tcp and TOS < 110*/,- /*everything else */ );
>
> regards
> momina
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