3 files changed, 21 insertions, 0 deletions
diff --git a/net.c b/net.c
index 4708080687..3b69d3b847 100644
--- a/net.c
+++ b/net.c
@@ -280,6 +280,21 @@ void qemu_format_nic_info_str(VLANClientState *vc, uint8_t macaddr[6])
              macaddr[3], macaddr[4], macaddr[5]);
 }
 
+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++;
+}
+
 static char *assign_name(VLANClientState *vc1, const char *model)
 {
     VLANState *vlan;
diff --git a/net.h b/net.h
index 439de2a842..605092a87d 100644
--- a/net.h
+++ b/net.h
@@ -7,6 +7,10 @@
 #include "qemu-option.h"
 #include "net-queue.h"
 
+struct MACAddr {
+    uint8_t a[6];
+};
+
 /* VLANs support */
 
 typedef int (NetCanReceive)(VLANClientState *);
@@ -65,6 +69,7 @@ ssize_t qemu_send_packet_async(VLANClientState *vc, const uint8_t *buf,
 void qemu_purge_queued_packets(VLANClientState *vc);
 void qemu_flush_queued_packets(VLANClientState *vc);
 void qemu_format_nic_info_str(VLANClientState *vc, uint8_t macaddr[6]);
+void qemu_macaddr_default_if_unset(MACAddr *macaddr);
 int qemu_show_nic_models(const char *arg, const char *const *models);
 void qemu_check_nic_model(NICInfo *nd, const char *model);
 int qemu_find_nic_model(NICInfo *nd, const char * const *models,
diff --git a/qemu-common.h b/qemu-common.h
index 47272f58cb..768e749feb 100644
--- a/qemu-common.h
+++ b/qemu-common.h
@@ -185,6 +185,7 @@ typedef struct PixelFormat PixelFormat;
 typedef struct TextConsole TextConsole;
 typedef TextConsole QEMUConsole;
 typedef struct CharDriverState CharDriverState;
+typedef struct MACAddr MACAddr;
 typedef struct VLANState VLANState;
 typedef struct VLANClientState VLANClientState;
 typedef struct QEMUFile QEMUFile;