net: disallow to specify multicast MAC address

[Assigning a multicast MAC address to a NIC leads to confusing behavior.
Reject multicast MAC addresses so users are alerted to their error
straight away.

The "net/eth.h" in6_addr rename prevents a name collision with
<netinet/in.h> on Linux.
-- Stefan]

Signed-off-by: Dmitry V. Krivenok <krivenok.dmitry@gmail.com>
Reviewed-by: Amos Kong <kongjianjun@gmail.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/net/net.c b/net/net.c
index c330c9a3a8..870d3bbcee 100644
--- a/net/net.c
+++ b/net/net.c
@@ -27,6 +27,7 @@
 #include "clients.h"
 #include "hub.h"
 #include "net/slirp.h"
+#include "net/eth.h"
 #include "util.h"
 
 #include "monitor/monitor.h"
@@ -689,6 +690,11 @@ static int net_init_nic(const NetClientOptions *opts, const char *name,
         error_report("invalid syntax for ethernet address");
         return -1;
     }
+    if (nic->has_macaddr &&
+        is_multicast_ether_addr(nd->macaddr.a)) {
+        error_report("NIC cannot have multicast MAC address (odd 1st byte)");
+        return -1;
+    }
     qemu_macaddr_default_if_unset(&nd->macaddr);
 
     if (nic->has_vectors) {