[Qemu-devel] [PATCH 1/2] avoid to allcate used macaddr to to new nic

[Amos Kong <akong@redhat.com>]

QEMU allocates macaddr to nic if user doesn't assigne macaddr.
But we didn't check if the allocated macaddr is used, it might
cause macaddr repeated.

 # qemu -device e1000,netdev=h1,mac=52:54:00:12:34:56
  (qemu) device_add e1000
  (qemu) info network
  e1000.0: index=0,type=nic,model=e1000,macaddr=52:54:00:12:34:56
   \ h1: index=0,type=user,net=10.0.2.0,restrict=off
  e1000.1: index=0,type=nic,model=e1000,macaddr=52:54:00:12:34:56

This patch adds a check in allocating macaddr, reallocate macaddr
if it's used by other nic.

Signed-off-by: Amos Kong <akong@redhat.com>
---
 net/net.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/net/net.c b/net/net.c
index 43a74e4..f019da4 100644
--- a/net/net.c
+++ b/net/net.c
@@ -143,15 +143,43 @@ void qemu_macaddr_default_if_unset(MACAddr *macaddr)
 {
     static int index = 0;
     static const MACAddr zero = { .a = { 0,0,0,0,0,0 } };
+    char info_str[256];
+    NetClientState *nc, *peer;
+    NetClientOptionsKind type;
 
     if (memcmp(macaddr, &zero, sizeof(zero)) != 0)
         return;
+
+realloc_mac:
     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++;
+
+    QTAILQ_FOREACH(nc, &net_clients, next) {
+        peer = nc->peer;
+        type = nc->info->type;
+
+        if (net_hub_id_for_client(nc, NULL) == 0) {
+            continue;
+        }
+
+        if (!peer || type == NET_CLIENT_OPTIONS_KIND_NIC) {
+            snprintf(info_str, sizeof(info_str),
+                     "model=%s,macaddr=%02x:%02x:%02x:%02x:%02x:%02x",
+                     nc->model,
+                     macaddr->a[0], macaddr->a[1], macaddr->a[2],
+                     macaddr->a[3], macaddr->a[4], macaddr->a[5]);
+
+            /* reallocate macaddr if it's used by other nic */
+            if (!strcmp(nc->info_str, info_str)) {
+                goto realloc_mac;
+            }
+        }
+    }
+
 }
 
 /**
-- 
1.8.1.4