Re: Getting MAC address?

From: Doug Rabson (dfr_at_nlsystems.com)
Date: 06/26/04

  • Next message: Doug Rabson: "Re: Getting MAC address?" 
    To: freebsd-hackers@freebsd.org
Date: Sat, 26 Jun 2004 13:51:16 +0100

    On Saturday 26 June 2004 10:15, Ivan Voras wrote:
    > Dmitry Morozovsky wrote:
    > > On Sat, 26 Jun 2004, Ivan Voras wrote:
    > >
    > > IV> How to get the MAC address for an (ethernet) interface? The
    > > linux code IV> does this:
    > > IV> retval = ioctl(thisint->sockInt, SIOCGIFHWADDR, &ifr);
    > > IV>
    > > IV> After some searching, I found SIOCSIFLLADDR ioctl, but it
    > > appears there IV> isn't a "GET" counterpart.
    > > IV>
    > > IV> (I've got interface name & index available...)
    > >
    > > Take a look at ifconfig(8) source.
    > >
    > > getifaddrs(3), case when sa_family == AF_LINK
    >
    > I was looking at it and came across getifaddrs(). This function does
    > not depend on a open socket (yes, mine is AF_LINK, sockaddr_dl), and
    > apparently returns a list of all interfaces. Is there really no other
    > way than to traverse this list?

    Its really not that hard:

    static void
    getNodeID(uint8_t node[6])
    {
        struct ifaddrs *ifap;

        if (getifaddrs(&ifap) == 0) {
            struct ifaddrs *p;
            for (p = ifap; p; p = p->ifa_next) {
                if (p->ifa_addr->sa_family == AF_LINK) {
                    struct sockaddr_dl* sdp = (struct sockaddr_dl*) p->ifa_addr;
                    memcpy(node, sdp->sdl_data + sdp->sdl_nlen, 6);
                    freeifaddrs(ifap);
                    return;
                }
            }
            freeifaddrs(ifap);
        }
    }
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