Am 15.10.2013 07:57, schrieb mike: > On 10/15/2013 01:07 PM, Stefan Weil wrote: >> Am 15.10.2013 06:17, schrieb Mike Qiu: >>> Changelog to v1: >>> Find remainder of macaddr->a[5] by modulo 256, >>> otherwise it may be overflow by add index++. >>> >>> The default mac address is 52:54:00:12:34:56 + index, this will >>> cause problem that when we boot up more than one guest with all >>> mac addresses unset by default, assume that each guest has one >>> nic. In this situation, all the guest's nic has the same mac address. >>> >>> This patch is to solve this bug. >>> >>> Signed-off-by: Mike Qiu <qiud...@linux.vnet.ibm.com> >>> --- >>> net/net.c | 9 ++++++--- >>> 1 file changed, 6 insertions(+), 3 deletions(-) >>> >>> diff --git a/net/net.c b/net/net.c >>> index c330c9a..9e72764 100644 >>> --- a/net/net.c >>> +++ b/net/net.c >>> @@ -21,6 +21,8 @@ >>> * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER >>> DEALINGS IN >>> * THE SOFTWARE. >>> */ >>> +#include <time.h> >>> + >>> #include "config-host.h" >>> #include "net/net.h" >>> @@ -147,12 +149,13 @@ void qemu_macaddr_default_if_unset(MACAddr >>> *macaddr) >>> if (memcmp(macaddr, &zero, sizeof(zero)) != 0) >>> return; >>> + srand((unsigned)time(NULL)); >>> 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++; >>> + macaddr->a[3] = rand() % 256; >>> + macaddr->a[4] = rand() % 256; >>> + macaddr->a[5] = (rand() % 256 + index++) % 256; >>> } >>> /** >> There is no overflow which must be handled because a[5] is an uint8_t >> value, so the assignment automatically limits the range to 0...255. > OK, you are right, but I think we'd better to ensure this, > even though a[5] is an uint8_t. >> Is it reasonable to get a random mac address in your guest? I don't >> think so. It would no longer be possible to connect to a guest using >> ssh, restart that guest and connect again with ssh. > Why not? I have do the experiment, after reboot, the mac is not changed. > and the ip address always the same. > > And can be login to the guest after reboot.
"restart" means terminate QEMU and start it again.
