sockets: AF_PACKET versus PF_PACKET

bayoulinux · 04-27-2012, 02:29 PM

Hi:

I'm new to socket programming... I notice that within the kernel AF_PACKET and PF_PACKET are defined to be the same, as do many (all?) AF_* and PF_* definitions.

When I create a socket:

socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL));

or

socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL));

I was just wondering what's the history, or the reasoning, for both the existence of AF_PACKET and PF_PACKET? Differences?

Thanks!

Nominal Animal · 04-27-2012, 05:03 PM

Quote:

Originally Posted by bayoulinux

AF_PACKET and PF_PACKET are defined to be the same, as do many (all?) AF_* and PF_* definitions.

Yes. AF_foo means address family foo, and PF_foo means protocol family foo. In Linux, they are always been the same values, I believe.

Traditionally, the PF_foo constants were used for socket(), but AF_foo in the struct sockaddr structure.

According to man 2 socket, even the (historical) BSD 4.x manpage states that "The protocol family generally is the same as the address family", and subsequent standards use AF_* everywhere.

Thus, today, there really should be no difference between AF_foo and PF_foo.