Re: Retrieving MAC address from struct ifnet

[Martin Husemann]

On Sun, Jun 08, 2025 at 04:00:22PM +0200, Beesdeckar wrote:
> When I try to cycle through interfaces and I read first member of if_hwdl
> (struct       sockaddr *ifa_addr) the result for ethernet is:
> 
> sa_family: 18, sa_len: 17,
> sa_data: 01 00 06 03 06 00 77 6D 30 F0 DE F1 8F AD EB 00 00

If you just want the string, call getnameinfo(3) on it, like:

        char name[40];
        getnameinfo(ifa, ifa->ifa_addr->sa_len, name, sizeof name,
            NULL, 0, NI_NUMERICHOST);

or if you want the binary representation:

        #include <net/if_dl.h>

        unsigned char dladdr[ETHER_ADDR_LEN];
        const struct sockaddr_dl *sdl = \
            (const struct sockaddr_dl*)ifa->ifa_addr;
        memcpy(dladdr, CLLADDR(sdl), ETHER_ADDR_LEN);


Martin