Monitoring network usage excluding local traffic

Question

I am working on an app that monitors network usage. However I noticed many ways to do this does not allow exclusion of local traffic (say, Time Machine).

I am lookin

Answer 1

you need to read the source for ifconfig(8), which describes how to get the status of every attached network interface.

pay particular attention to in_status(), which gets the inet address and netmask of an interface.

when the source or destination address in the traffic has the same host as a local interface

int is_local =
(src && netmask) == (ifaddr && netmask)
|| (dst && netmask) == (ifaddr && netmask)

then you can be sure that it is local

http://www.opensource.apple.com/source/network_cmds/network_cmds-307/ifconfig.tproj/ifconfig.c