(Error in makefile)RTNETLINK answers: File exists

This is my makefile:

delay:
    tc qdisc add dev eth0 root netem delay 0ms
test4_s_delay:delay
    ./a.out 10 10 1 2 3 1 1 20 | tee server_delay.txt

However, I am getting the following error on execution of the makefile:

root@superwii-laptop:/开发者_开发技巧home/superwii/Desktop/Amogh# make test4_s_delay
tc qdisc add dev eth0 root netem delay 0ms
RTNETLINK answers: File exists
make: *** [delay] Error 2

I am unable to get past this error. Please help.

You would get this error, if qdisc root node already exists.
Try deleting the root qdisc

sudo tc qdisc del dev eth0 root

and try again

Looks like your executable tc is exiting with non-zero value of 2.

Try running the command tc qdisc add dev eth0 root netem delay 0ms and see if it runs fine.

use replace instead of add

tc qdisc replace dev eth0 root netem delay. Man page for tc says :

replace performs a nearly atomic remove/add on an existing node id. If the node does not exist yet it is created.