Is there a kernel module that returns exactly what a simple 'ifconfig' does?

Question

I'm writing a kernel module that needs information about the local machine's interfaces just like the ones retuned by a simple 'ifconfig' command, I've searched a lot for it, but couldn't find anything

Answer 1

You can get all of that information through the struct net_device one way or another. As Albert Veli said, you can get this struct net_device pointer using __dev_get_by_name().

If you tell us what information you need specifically we might even be able to point you to the correct fields.

Finding the MAC address is fairly simple:

struct net_device *dev = __dev_get_by_name("eth0");
dev->dev_addr; // is the MAC address
dev->stats.rx_dropped; // RX dropped packets. (stats has more statistics)

Finding the IP address is rather harder, but not impossible:

struct in_device *in_dev = rcu_dereference(dev->ip_ptr);
// in_dev has a list of IP addresses (because an interface can have multiple)
struct in_ifaddr *ifap;
for (ifap = in_dev->ifa_list; ifap != NULL;
         ifap = ifap->ifa_next) {
    ifap->ifa_address; // is the IPv4 address
}

(None of this was compile tested, so typos are possible.)

Answer 2

See for example the in6_dump_addrs function in net/ipv6/addrconf.c for how to get at addresses. For link properties like link layer address, see core/rtnetlink.c instead. ifconfig and its ioctls are obsolete (on Linux), so better don't think in terms of that now-bug-ridden program.