Accessing data link layer packets

Question

I want to create a socket for accessing IPv4 packets from data link layer. From unix network programming V1,

socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP))

1)I am implementing a dhcp client, is this the correct way of doing that? (means without accessing data link layer, i cannot receive reply from dhcp server) or is there any other easier way? also, since this socket will receive all IPv4 packets destined for my system, how should I distinguish dhcp reply packet from other packets?

2)please suggest me a good link/tuorial for network programming with data link layer access. In the above book, it is not detailed description.

This is my code

Answer 1

Do you need the link layer headers too? If so, You need to use SOCK_RAW—SOCK_DGRAM will remove the link layer header before feeding it to your application.

You can identify DHCP requests by the source and destination ports, since DHCP generates traffic on UDP ports 67 and 68.

Answer 2

Did you tried looking at PCAP libraries? It provides nice filtering functions on IP, port and other things.