I created a thread to continually sniff certain network packets at the datalink layer every few seconds using libpcap. eth0 is being opened in promiscuous mode. I do not want to leave the pcap object open, so I am calling pcap_open_live() and pcap_close() each time in the loop. This results in

entered promiscuous mode

left promiscuous mode

I understand I can redirect to null in comand line or script. However, the message is being displayed during library call to pcap_open_live() in the libpcap library.
Anyways, I have found the printk statement in the kernel file /net/core/dev.c., function dev_set_promiscuity(). So, I just commented it out and rebuilt the kernel for my embedded system.