LARTC - Apr 2006 - "action pass random determ/netrand reclassify --value--": granularity problems

Hi all!
 
 I''m trying to do proportional marking of real-time traffic to indicate
link congestion, and for that, I wish to use the DSMARK filter to mark from, say
EF to 0xcc. (an unused DSCP value)
 By proportional, I mean, if congestion on the egress link is, say 38%, then I
shall remark 38 packets of every 100 leaving eth0.
 
 I already wrote some scripts, and I can measure the overload ratio, decide when
congestion occurs locally, and modify any filter from C code in runtime with
system calls.
 
 Problem is, from what I get from the /doc library from the newest iproute2
package, when using ACTIONS with DETERM or NETRAND, followed by a value, that
number is an INTEGER, and thus it says:
 
 action drop random netrand ok 10  -->
 allow 1 out 10 randomly
 
 and
 
 action drop random determ ok 2  -->
 deterministically accept every second packet
 
 This seems to behave like: every nth, so I can''t have anything more
than 50%,
 and even below 50%, levels are stepped, like 33%, 25%, etc.
 
 What I would like to do is:
 action pass random determ continue  RATIO,
 so when RATIO is 0, it would pass all packets, when it is not,
 it would step to the next filter (the DSMARK remarker) before sending.
 But I need stepping at % ratio, (meaning if insisting on nth-method, the value
could be: every 100/74-th packet, which is obviously not an integer.
 
 Could you give me some ideas? Anyone used something like this before?
 
 Any advice/help is highly appreciated.
 
 Ferenc
 
			
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