osv_start_if: set address instead of adding a new one

SIOCAIFADDR appends an address to the interface's address list instead of
replacing it.  This causes 'ifconfig' to display 0.0.0.0 (the first address
configured) instead of the correct address obtained by dhcp.

Fix by also deleting the existing address, if it exists.

bsd/porting/networking.c

@@ -16,6 +16,7 @@
 int osv_start_if(const char* if_name, const char* ip_addr, const char* mask_addr)
 {
     int error, success;
+    struct ifreq oldaddr;
     struct in_aliasreq ifra;
     struct bsd_sockaddr_in* addr      = &ifra.ifra_addr;
     struct bsd_sockaddr_in* mask      = &ifra.ifra_mask;
@@ -58,6 +59,11 @@ int osv_start_if(const char* if_name, const char* ip_addr, const char* mask_addr
     broadcast->sin_addr.s_addr = (addr->sin_addr.s_addr &
                                   mask->sin_addr.s_addr) |
                                  ~mask->sin_addr.s_addr ;
+    strncpy(oldaddr.ifr_name, if_name, IFNAMSIZ);
+    error = in_control(NULL, SIOCGIFADDR, (caddr_t)&oldaddr, ifp, NULL);
+    if (!error) {
+        in_control(NULL, SIOCDIFADDR, (caddr_t)&oldaddr, ifp, NULL);
+    }
     error = in_control(NULL, SIOCAIFADDR, (caddr_t)&ifra, ifp, NULL);
 
 out: