netem: add cell concept to simulate special MAC behavior
This extension can be used to simulate special link layer
characteristics. Simulate because packet data is not modified, only the
calculation base is changed to delay a packet based on the original
packet size and artificial cell information.
packet_overhead can be used to simulate a link layer header compression
scheme (e.g. set packet_overhead to -20) or with a positive
packet_overhead value an additional MAC header can be simulated. It is
also possible to "replace" the 14 byte Ethernet header with something
else.
cell_size and cell_overhead can be used to simulate link layer schemes,
based on cells, like some TDMA schemes. Another application area are MAC
schemes using a link layer fragmentation with a (small) header each.
Cell size is the maximum amount of data bytes within one cell. Cell
overhead is an additional variable to change the per-cell-overhead
(e.g. 5 byte header per fragment).
Example (5 kbit/s, 20 byte per packet overhead, cell-size 100 byte, per
cell overhead 5 byte):
tc qdisc add dev eth0 root netem rate 5kbit 20 100 5
Signed-off-by: Hagen Paul Pfeifer <hagen@jauu.net>
Signed-off-by: Florian Westphal <fw@strlen.de>
Acked-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/pkt_sched.h b/include/linux/pkt_sched.h
index 8786ea7..8daced3 100644
--- a/include/linux/pkt_sched.h
+++ b/include/linux/pkt_sched.h
@@ -502,6 +502,9 @@
struct tc_netem_rate {
__u32 rate; /* byte/s */
+ __s32 packet_overhead;
+ __u32 cell_size;
+ __s32 cell_overhead;
};
enum {