net: add MAC address string printer

We can use this in virtio-net code as well as new Rocker driver code, so
up-level this.
Signed-off-by: NScott Feldman <sfeldma@gmail.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Message-id: 1426306173-24884-2-git-send-email-sfeldma@gmail.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

include/net/net.h

@@ -97,6 +97,7 @@ typedef struct NICState {
     bool peer_deleted;
 } NICState;
 
+char *qemu_mac_strdup_printf(const uint8_t *macaddr);
 NetClientState *qemu_find_netdev(const char *id);
 int qemu_find_net_clients_except(const char *id, NetClientState **ncs,
                                  NetClientOptionsKind type, int max);

net/net.c

@@ -151,6 +151,13 @@ int parse_host_port(struct sockaddr_in *saddr, const char *str)
     return 0;
 }
 
+char *qemu_mac_strdup_printf(const uint8_t *macaddr)
+{
+    return g_strdup_printf("%.2x:%.2x:%.2x:%.2x:%.2x:%.2x",
+                           macaddr[0], macaddr[1], macaddr[2],
+                           macaddr[3], macaddr[4], macaddr[5]);
+}
+
 void qemu_format_nic_info_str(NetClientState *nc, uint8_t macaddr[6])
 {
     snprintf(nc->info_str, sizeof(nc->info_str),