How to set up netem qdisc and tbf qdisc using libnl-route?

Question

I'm trying to do network emulation on ubuntu 12.04 while the shell commands work:

tc qdisc add dev eth1 root handle 1:0 tbf rate 200kbit buffer 1600 limit 3000

or

tc qdisc change dev eth0 root netem loss 0.1%

Now I want to do the same things in c code and i found libnl.

I have successfully added prio & htb qdisc using the doc

http://www.carisma.slowglass.com/~tgr/libnl/doc/route.html#tc_qdisc

but when I did the netem qdisc, it returned "Invalid input data or parameter", and "Missing attribute" in tbf qdisc case. My codes is as follows:

1. netem

   q = rtnl_qdisc_alloc();
   rtnl_tc_set_ifindex(TC_CAST(q), 2);
   rtnl_tc_set_parent(TC_CAST(q), TC_H_ROOT);
   rtnl_tc_set_handle(TC_CAST(q), TC_HANDLE(1, 0));
   rtnl_tc_set_kind(TC_CAST(q), "netem");
   
   rtnl_netem_set_delay(q, 100);
   rtnl_netem_set_loss(q, 10);
   
   int err = rtnl_qdisc_add(sock, q, NLM_F_CREATE);
   if(err<0){
     printf("netem error: %s\n", nl_geterror(err));
   }
   

2. tbf

   q = rtnl_qdisc_alloc();
   rtnl_tc_set_ifindex(TC_CAST(q), 2);
   rtnl_tc_set_parent(TC_CAST(q), TC_H_ROOT);
   rtnl_tc_set_handle(TC_CAST(q), TC_HANDLE(1, 0));
   rtnl_tc_set_kind(TC_CAST(q), "tbf");
   
   rtnl_qdisc_tbf_set_limit(q, 1000);
   rtnl_qdisc_tbf_set_rate(q, 1000, 1000, 8);
   
   int err = rtnl_qdisc_add(sock, q, NLM_F_CREATE);
   if(err<0){
     printf("tbf error: %s\n", nl_geterror(err));
   }
   

I have tried all the corresponding functions the api ref refers, but always have the same errors "Invalid input data or parameter" and "Missing attribute", and googled with no help.

I have got stuck with the problem for more than a week, i need your help.

Answer 1

I looked over your code, but I miss some parameters. Like versions of your libraries and gcc flags you are using. So I decided to give you an example code and you can compare what are the difference to your system/code.

All the libraries on my system have the version 3.2.24-1 (debian unstable); Libraries you need:

• libnl-3-dev
• libnl-cli-3-dev
• libnl-genl-3-dev
• libnl-nf-3-dev
• libnl-route-3-dev
• libnl-3-200
• libnl-cli-3-200
• libnl-genl-3-200
• libnl-nf-3-200
• libnl-route-3-200
• libnl-utils

To compile the code use this command. You can adjust if you want, but "-lnl-genl-3 -lnl-3 -lnl-route-3" is mandatory

"gcc -lnl-genl-3 -lnl-3 -lnl-route-3 -fpermissive --pedantic-errors -Wall -Wextra -ftabstop=4 -march=native -fshow-column -ftabstop=4 -frounding-math -pipe -ggdb3 -O0 main.c -o your_qdisc_app"

#include <libnl3/netlink/route/tc.h>
#include <libnl3/netlink/route/qdisc.h>
#include <libnl3/netlink/route/qdisc/netem.h>
#include <libnl3/netlink/route/qdisc/tbf.h>

int main(int argc, char ** argv)
{
  struct nl_sock *sock;
  struct rtnl_qdisc *q;
  struct nl_cache *cache;
  struct rtnl_link *link;
  int if_index;


  sock = nl_socket_alloc();

  nl_connect(sock, NETLINK_ROUTE);
  rtnl_link_alloc_cache(sock, AF_UNSPEC, &cache);
  link = rtnl_link_get_by_name(cache, "eth0");
  if_index = rtnl_link_get_ifindex(link);

  q = rtnl_qdisc_alloc();               

  rtnl_tc_set_ifindex(TC_CAST(q), if_index);
  rtnl_tc_set_parent(TC_CAST(q), TC_H_ROOT);
  rtnl_tc_set_handle(TC_CAST(q), TC_HANDLE(1, 0));
  rtnl_tc_set_kind(TC_CAST(q), "tbf"); 

  /*
   * netem okay, htb okay, please comment 
   * and uncomment the special parameters for the qdiscs
  */
  rtnl_qdisc_tbf_set_limit(q, 1000);
  rtnl_qdisc_tbf_set_rate(q, 1000, 1000, 8);
  /*
   * rtnl_netem_set_delay(q, 100);
   * rtnl_netem_set_loss(q, 10);
  */

  rtnl_qdisc_add(sock, q, NLM_F_CREATE);

  rtnl_qdisc_put(q);
  nl_socket_free(sock);
  rtnl_link_put(link);
  nl_cache_put(cache);

  return 0;
}

I left out all the checks with "if" to minimize the lines. The checks can be added if necessary. If you have further question, get in touch with me.

cya, Philipp