Michael Tokarev wrote:
Hello. Right now I'm evaluating various ways to perform traffic accounting in Linux. Nowadays solutions are all based on netfilter and packet queuing over netlink interface. And most tools used for that sort of stuff are based on Cisco "flows". So far so good. There are several tools available to perform logging of various statistics which are being logging over netlink, including the successor of ulogd. But all the tools I've seen so far perform "flow management" in userspace in addition to all the housekeeping the kernel already does - namely, mixing-n-matching various conntrack entries together, keeping/managing hash tables of various (src_IP, dst_IP, src_port, dst_port etc) stuff. For flow-based accounting (compatible with cisco netflows I mean) this all is only to get one field of the flow structure: it's the start_time, i.e., in terms of conntrack, it's the time when the conntrack entry were created. But isn't it a bit excessive to duplicate all the (quite heavy and fast-changing) data structures in both kernel- and user-space? I mean, at least for the "industry standard" format, the one missing field can be kept by kernel, especially since there, it costs only extra 4 bytes, and zero CPU, while in duplicating the whole thing in user space is something entirely else?
I think its done for aggregation, but not sure. And we used to have 32bit counters for a while, so userspace needed to track overflows.
I understand that this is not a standard format, not even to think about "The" standard, and there are other possible formats too, with their own complications/requirements, and that for users who does not use such statistics that's 4 bytes wasted per conntrack which also may mean something... But still, now not talking about cisco netflows in particular, but from just logical point of view -- the information exposed by the kernel is incomplete and lacks this very field, -- flow start_time -- I think. So, are there any objections/comments/suggestions about just adding this one thing (conditionally using CONFIG_foo or not)? Or maybe it is already there and there's nothing to do?
How are you going to log the data of a connection thats removed from the conntrack tables without using netlink? If you're using netlink, you can generate a time stamp when you receive a NEW event. -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
