If you are trying to compile any network packet capturing related program, there are higher chances you may see an errors like,
undefined reference to `pcap_lookupdev' undefined reference to `pcap_open_live' undefined reference to `pcap_loop' undefined reference to `pcap_geterr' collect2: error: ld returned 1 exit status
This error is because, you either doesn’t have libpcap installed or its not being linked from the command line. Lets say you are trying to compile simple wifi packet sinffer based on libpcap, then first you will need to install libpcap.
$ sudo apt-get install libpcap-dev
This will install your machine dependent libpcap version. and then link the libpcap during compilation as,
$ gcc -o simplesniffer simplesniffer.c -lcap