Code snippet from here:
void packet_handler(u_char *param, const struct pcap_pkthdr *header, const u_char *pkt_data)
{
....
/* retireve the position of the ip header */
ih = (ip_header *) (pkt_data +
14); //length of ethernet header
....
What's const struct pcap_pkthdr *header
for(definition), when do we need it, how is it populated (since there is no such info in the packet itself as below)?
alt text http://www.dcs.gla.ac.uk/~lewis/networkpages/m04s03EthernetFrame_files/image002.gif
If you would have kept the comment, it would have been a tad easier. It says:
Here it says about
typedef void(*) pcap_handler(u_char *user, const struct pcap_pkthdr *pkt_header, const u_char *pkt_data)
: