void qemu_macaddr_default_if_unset(MACAddr *macaddr) { static int index = 0; static const MACAddr zero = { .a = { 0,0,0,0,0,0 } }; if (memcmp(macaddr, &zero, sizeof(zero)) != 0) return; macaddr->a[0] = 0x52; macaddr->a[1] = 0x54; macaddr->a[2] = 0x00; macaddr->a[3] = 0x12; macaddr->a[4] = 0x34; macaddr->a[5] = 0x56 + index++; }