How to print messages in BSD network stack code?

Question

I want to add some printf statements of my own in the BSD network stack. But after adding them I cannot see the messages coming up on the console of my machine. I tried to add some in the netisr ( sys/net/netisr.c ) . Cannot even find the already present printf statements. A noob at kernel programming.

 netsmp_lockinit(void *dummy)
  {      
          printf("Function %s   File %s : Line %d\n",__func__,__FILE__,__LINE__);
          rw_init_flags(&Netstack, "netsmp", RW_NETLOCK);
  }

Answer 1

The kernel can't use the C Standard I/O facilities. It must use a logging facility. For example, sys/netinet/in.c uses

log(LOG_INFO, "in_scrubprefix: err=%d, old prefix delete failed\n", error);

to communicate to the world outside what happened.